australian electronic gold prospecting forum.com

Detector Technology and Electronics and new detectors => Detector Coils => Topic started by: Aziz on Tuesday November 28 2017 20:34:18 AEDT PM



Title: The need for big deep gold detectors.
Post by: Aziz on Tuesday November 28 2017 20:34:18 AEDT PM
Hi all,

some of the guys want to dig deep. Much deeper than 1 m.
( http://golddetecting.4umer.net/t25661-mineralization )

Chasing the big ones. Which can't be detected with the current detectors and coils.
They are still there. Lot's of them. The big and deep gold.
Just below the impenetrable magnetic field shield (the heavy ground mineralization layer).

Pity, that no one has made such a detector during my absence yet.
What's happened?
We know how to do it.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Tuesday November 28 2017 21:11:06 AEDT PM
  


Pity, that no one has made such a detector during my absence yet.
What's happened?

Aziz

Special instruction needed.

We still bother with GPZ yellow ferrite GB.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday November 28 2017 21:35:17 AEDT PM
  
  


Pity, that no one has made such a detector during my absence yet.
What's happened?

Aziz

Special instruction needed.

We still bother with GPZ yellow ferrite GB.

Hi WM6,

I see, that GPZ had a software update for ground tracking.
Yellow ferrite is a substitute for a hot rock. Oz guys don't need to buy this ferrite. They have lots of hot rocks lying around there.

"Special instruction needed."
Already done in the past.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Tuesday November 28 2017 23:12:01 AEDT PM
  

"Special instruction needed."
Already done in the past.
Aziz

Nice. Then new ML patent and detectors will be out soon.


Title: Re: The need for big deep gold detectors.
Post by: Doug on Tuesday November 28 2017 23:42:44 AEDT PM
 The deepest Pi detector ever developed in my opinion was a prototype  SD2000  that BC modified for the late Jim Stewart.BC slowed down the clock speed  to give a very long pulse and made some other unknown changes to the circuit to cope with higher currents etc. At the time the SD2000 came out BC stated that it was at about 95% of the maximum potential depth that any hand held PI could ever achieve (and still pass emission  standards). However the deepest PI that has ever been made for gold was Corybns detector which detected a  nugget of around 10oz? at 3 feet in depth in WA. Some where on the forum is a reference to it and i will try and find the link when i have time.
doug


Title: Re: The need for big deep gold detectors.
Post by: Doug on Tuesday November 28 2017 23:59:06 AEDT PM
  
The deepest Pi detector ever developed in my opinion was a prototype  SD2000  that BC modified for the late Jim Stewart.BC slowed down the clock speed  to give a very long pulse and made some other unknown changes to the circuit to cope with higher currents etc. At the time the SD2000 came out BC stated that it was at about 95% of the maximum potential depth that any hand held PI could ever achieve (and still pass emission  standards). However the deepest PI that has ever been made for gold was Corybns detector which detected a  nugget of around 10oz? at 3 feet in depth in WA. Some where on the forum is a reference to it and i will try and find the link when i have time.
doug
Here is the post and the link
"What is interesting is that the deepest nuggets ever detected by a Pi  was by a detector used in the early 1980's in WA-Corbyn's  wheeled detector! Pictures of it  and the depths of some of nuggets he found with it can be seen in Mike Wattones book :Quest for gold.NO Pi detector today could match the depths Corby got on at least one nugget! (4cm nugget at over 36" in mineralized ground)
doug 
http://australianelectronicgoldprospectingforum.com/general-chat-and-discussion-forum/detecting-larger-nuggets/msg35490/#msg35490


Title: Re: The need for big deep gold detectors.
Post by: egixe4 on Wednesday November 29 2017 19:45:36 AEDT PM
  
  
  


Pity, that no one has made such a detector during my absence yet.
What's happened?

Aziz

Special instruction needed.

We still bother with GPZ yellow ferrite GB.

Hi WM6,

I see, that GPZ had a software update for ground tracking.
Yellow ferrite is a substitute for a hot rock. Oz guys don't need to buy this ferrite. They have lots of hot rocks lying around there.

"Special instruction needed."
Already done in the past.
Aziz

Nothing new with Ferrite being included with Detectors, my first whites a 5000D VLF had a piece of Ferrite included in the box, used as a sample to set up the manual GB.

The Ferrite represents a mineral sample or negative (hot rock) as opposed to a rusty nail or piece of Ironstone or Positive (hot rock)
Ferrite will Null the threshold when the coil is passed over it, creating a Bong sound as the threshold recovered
These rocks were known back in the day as bongers.

To combat these negative (hot rock's) on a Manual GB machine, the QED for example, is to run a slightly positive offset on the GB.



Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday November 29 2017 20:35:02 AEDT PM
Hi all,

does anyone know the positive/negative peak coil current and the inductance of the TX coil for the new GPZ?
And the TX frequency?


Title: Re: The need for big deep gold detectors.
Post by: Goldman on Wednesday November 29 2017 21:06:14 AEDT PM
  
  
  
  


Pity, that no one has made such a detector during my absence yet.
What's happened?

Aziz

Special instruction needed.

We still bother with GPZ yellow ferrite GB.

Hi WM6,

I see, that GPZ had a software update for ground tracking.
Yellow ferrite is a substitute for a hot rock. Oz guys don't need to buy this ferrite. They have lots of hot rocks lying around there.

"Special instruction needed."
Already done in the past.
Aziz

Nothing new with Ferrite being included with Detectors, my first whites a 5000D VLF had a piece of Ferrite included in the box, used as a sample to set up the manual GB.

The Ferrite represents a mineral sample or negative (hot rock) as opposed to a rusty nail or piece of Ironstone or Positive (hot rock)
Ferrite will Null the threshold when the coil is passed over it, creating a Bong sound as the threshold recovered
These rocks were known back in the day as bongers.

To combat these negative (hot rock's) on a Manual GB machine, the QED for example, is to run a slightly positive offset on the Threshold.



Is that by adjusting bias up slightly from null, or by using a slightly higher GB


Title: Re: The need for big deep gold detectors.
Post by: egixe4 on Wednesday November 29 2017 21:40:31 AEDT PM
  
  
  
  
  


Pity, that no one has made such a detector during my absence yet.
What's happened?

Aziz

Special instruction needed.

We still bother with GPZ yellow ferrite GB.

Hi WM6,

I see, that GPZ had a software update for ground tracking.
Yellow ferrite is a substitute for a hot rock. Oz guys don't need to buy this ferrite. They have lots of hot rocks lying around there.

"Special instruction needed."
Already done in the past.
Aziz

Nothing new with Ferrite being included with Detectors, my first whites a 5000D VLF had a piece of Ferrite included in the box, used as a sample to set up the manual GB.

The Ferrite represents a mineral sample or negative (hot rock) as opposed to a rusty nail or piece of Ironstone or Positive (hot rock)
Ferrite will Null the threshold when the coil is passed over it, creating a Bong sound as the threshold recovered
These rocks were known back in the day as bongers.

To combat these negative (hot rock's) on a Manual GB machine, the QED for example, is to run a slightly positive offset on the Threshold.



Is that by adjusting bias up slightly from null, or by using a slightly higher GB

Sorry that should read, run a slightly positive offset on the GB


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday November 29 2017 23:19:33 AEDT PM
Hi all,

I have just checked my basement and it seems, that I have really enough iron oxide so I don't have to buy more.
Some of the samples must be converted into a strong magnetic maghemite. But I also have quite amount of maghemite samples.

I hope, that I can show the magnetic field shielding effect of the high mineral ground layer by making simple induction measurements (TX -> RX coil sensor). The result will show, that a special coil confuguration can cope with the effect and we already know what kind of coil is the way to go.

BTW, I also have found a bag of nearly 5 kg FeSO4 (ferrous sulphate). I could turn it chemically into iron oxide using a tube cleaner (containing NaOH) but would take some time. I am testing this process with a small amount and an air blower to oxidize the resulting Fe(OH)3.


This experiment is part of the big deep gold detector (regarding the coil).

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: authere on Thursday November 30 2017 00:23:30 AEDT AM
Hi Aziz,

When you get your test beds sorted can you throw in a big bag of salt into one for salt lakes as I'm sure there is better shielding to be had for salt lake detecting

Cheers,Ron


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday November 30 2017 00:33:10 AEDT AM
  
Hi Aziz,

When you get your test beds sorted can you throw in a big bag of salt into one for salt lakes as I'm sure there is better shielding to be had for salt lake detecting

Cheers,Ron

Hi Ron,

why not. But I don't think, that dry salt is going to make problems. Wet salt is another issue of course.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: egixe4 on Thursday November 30 2017 10:53:36 AEDT AM
Some useful info on hot rocks can found here
http://www.metaldetectingworld.com/hot_rocks.shtml


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 1 2017 20:30:35 AEDT PM
Hi all,

I am just wondering why ML is using a Super-D coil for their GPZ. A concentric IB coil would punch deeper in those mineralized grounds.


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Friday December 1 2017 21:46:49 AEDT PM
Surely Aziz .. the detector is there .. is perhaps a new type of coil design required ..
There must be other types of coil configuration yet to be discovered ...


Title: Re: The need for big deep gold detectors.
Post by: mylab on Friday December 1 2017 22:10:41 AEDT PM
Aziz please don't tell them to much or they will pitch your ideas as I believe they have done in the past.

Cheers.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 2 2017 00:28:21 AEDT AM
  
Surely Aziz .. the detector is there .. is perhaps a new type of coil design required ..
There must be other types of coil configuration yet to be discovered ...

Hi gef12,

no, we don't need new coil designs.
A simple concentric coplanar IB coil should simply give GPZ more depth on severe mineralized grounds.

The Super-D coil has only benefit for:
- covering more surface area during the coil sweeps
- double detection of targets during the coil sweeps (if you miss the first signal)
- optimized for small shallow nugget detection

--------------

I have found a possible way of making the old style PI going deeper than existing machines. Without infringing any patent.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Doug on Saturday December 2 2017 12:49:23 AEDT PM
 I see that this topic has been raised on SH forum. As  expected JP chimes in and claims the SAD7000 will" thrash" any PI for depth on large nuggets. He of course provides no evidence to substantiate this or any electromagnetic  or electronic or technical reasons as to why this should be so. As usual he only tells half the story and while he refers to the 1/r^6 law he does not say that this is  one the of main factors in detecting larger conductive objects at depth ie the the diameter of the TX coil will ultimately determine the depth at which large  conductive objects can be detected. Corbyn coils were from memory about 36” in diameter. I have no doubt that the late JS modified SD2000 with his 36” coil would thrash the SAD7000  for depth on most very large, solid  highly conductive nuggets.
 The diam of the TX component of the SAD 7000 DOD coil will ultimately  be one of the key factors in determining how deep a large conductive object can be detected. You cannot escape the laws of physics regardless of what signal acquisition/processing wizardry you use!  In addition for large ,highly conductive objects you require a long exposure time to the  energizing Tx field   and the energizing field needs a lot of low frequency spectral content.
doug


Title: Re: The need for big deep gold detectors.
Post by: Doug on Saturday December 2 2017 13:40:43 AEDT PM
If we are serious about chasing mega nuggets at depth then in my view this is  the sort of systems we need.  The other huge advantage of some of these systems is that when combined with high resolution magnetometers  it opens the possibility of reliably discriminating between ferrous/ non ferrous objects at depth. NO hand held hobby detector will ever be able to compete for depth on larger conductive objects with these large Tx loop sensors!
Large loop EMI sensor for detection of deeply buried munitions in magnetic soils
Jonathan S. Miller; Stephen Billings; Joe Keranen; Gregory Schultz; Chet Bassani
https://www.spiedigitallibrary.org/conference-proceedings-of-spie/8357/1/Large-loop-EMI-sensor-for-detection-of-deeply-buried-munitions/10.1117/12.919393.short?SSO=1
link-https://www.spiedigitallibrary.org/conference-proceedings-of-spie/8357/1/Large-loop-EMI-sensor-for-detection-of-deeply-buried-munitions/10.1117/12.919393.short?SSO=1
http://www.humanitarian-demining.org/2010design/resources/Scorpion_FS-16Nov2017.pdf
link-http://www.humanitarian-demining.org/2010design/resources/Scorpion_FS-16Nov2017.pdf
http://www.gapgeo.com/media/18164/eod-get-high-res_v2.pdf
link-http://www.gapgeo.com/media/18164/eod-get-high-res_v2.pdf
doug


Title: Re: The need for big deep gold detectors.
Post by: mylab on Saturday December 2 2017 15:24:01 AEDT PM
  

....one the of main factors in detecting larger conductive objects at depth ie the the diameter of the TX coil will ultimately determine the depth at which large  conductive objects can be detected.


If true in regards to a DOD coil as it is with a DD coil then the TX coil on the DOD being elongated and smaller in dimension than the overall dimension of the DOD coil itself then I wonder what the 14"DOD or 19"DOD are equivalent to in a coil?

Aziz could also shed more light on the result?


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Saturday December 2 2017 19:25:50 AEDT PM
  
I see that this topic has been raised on SH forum. As  expected JP chimes in and claims the SAD7000 will" thrash" any PI for depth on large nuggets. He of course provides no evidence to substantiate this or any electromagnetic  or electronic or technical reasons as to why this should be so. As usual he only tells half the story and while he refers to the 1/r^6 law he does not say that this is  one the of main factors in detecting larger conductive objects at depth ie the the diameter of the TX coil will ultimately determine the depth at which large  conductive objects can be detected. Corbyn coils were from memory about 36” in diameter. I have no doubt that the late JS modified SD2000 with his 36” coil would thrash the SAD7000  for depth on most very large, solid  highly conductive nuggets.
 The diam of the TX component of the SAD 7000 DOD coil will ultimately  be one of the key factors in determining how deep a large conductive object can be detected. You cannot escape the laws of physics regardless of what signal acquisition/processing wizardry you use!  In addition for large ,highly conductive objects you require a long exposure time to the  energizing Tx field   and the energizing field needs a lot of low frequency spectral content.
doug

Hi Doug and Aziz.

I remember Reg Wilson say that the prototype SD 2000 was the only detector that got a signal on very deep gold nuggets.
Was it because they used more power into the SD than a standard SD?


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Saturday December 2 2017 19:31:41 AEDT PM
  
Hi all,

I am just wondering why ML is using a Super-D coil for their GPZ. A concentric IB coil would punch deeper in those mineralized grounds.


Hi Aziz,
Can I pace an order of this coil you talk about for my gpx 5000 detector.?
There's some ground here that cannot be detected at all by any detector with deep gold diggings everywhere there.
Thanks.


Title: Re: The need for big deep gold detectors.
Post by: Doug on Saturday December 2 2017 21:23:00 AEDT PM
  
  
I see that this topic has been raised on SH forum. As  expected JP chimes in and claims the SAD7000 will" thrash" any PI for depth on large nuggets. He of course provides no evidence to substantiate this or any electromagnetic  or electronic or technical reasons as to why this should be so. As usual he only tells half the story and while he refers to the 1/r^6 law he does not say that this is  one the of main factors in detecting larger conductive objects at depth ie the the diameter of the TX coil will ultimately determine the depth at which large  conductive objects can be detected. Corbyn coils were from memory about 36” in diameter. I have no doubt that the late JS modified SD2000 with his 36” coil would thrash the SAD7000  for depth on most very large, solid  highly conductive nuggets.
 The diam of the TX component of the SAD 7000 DOD coil will ultimately  be one of the key factors in determining how deep a large conductive object can be detected. You cannot escape the laws of physics regardless of what signal acquisition/processing wizardry you use!  In addition for large ,highly conductive objects you require a long exposure time to the  energizing Tx field   and the energizing field needs a lot of low frequency spectral content.
doug

Hi Doug and Aziz.

I remember Reg Wilson say that the prototype SD 2000 was the only detector that got a signal on very deep gold nuggets.
Was it because they used more power into the SD than a standard SD?

I believe it was because of a longer Tx pulse and a higher Tx field strength.
doug


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 2 2017 21:56:43 AEDT PM
Hi Doug,

  
I see that this topic has been raised on SH forum. As  expected JP chimes in and claims the SAD7000 will" thrash" any PI for depth on large nuggets.
doug

SH forum? Where?


Title: Re: The need for big deep gold detectors.
Post by: mylab on Saturday December 2 2017 22:02:33 AEDT PM
Quote from: Aziz

[/quote

SH forum? Where?


Here it is Aziz

http://www.detectorprospector.com/forum/forum/4-detector-prospector-forum/


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 2 2017 22:07:18 AEDT PM
  
Hi Aziz,
Can I pace an order of this coil you talk about for my gpx 5000 detector.?
There's some ground here that cannot be detected at all by any detector with deep gold diggings everywhere there.
Thanks.

Hi sd220d Digger,

such a coil concept already exists. But can't be used on GPX detectors as it would require complex modifications.

The coil concept is known as the separate concentric coplanar (large)TX / (small)RX. These coils would go far deeper on mineralized grounds with the benefit of reduced EMI and ground response. I have alreay analyzed this coil concept a few years ago.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 2 2017 22:11:59 AEDT PM
  
Quote from: Aziz

[/quote

SH forum? Where?


Here it is Aziz

http://www.detectorprospector.com/forum/forum/4-detector-prospector-forum/

Thanks!


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Saturday December 2 2017 23:48:57 AEDT PM
  
  
Hi Aziz,
Can I pace an order of this coil you talk about for my gpx 5000 detector.?
There's some ground here that cannot be detected at all by any detector with deep gold diggings everywhere there.
Thanks.

Hi sd220d Digger,

such a coil concept already exists. But can't be used on GPX detectors as it would require complex modifications.

The coil concept is known as the separate concentric coplanar (large)TX / (small)RX. These coils would go far deeper on mineralized grounds with the benefit of reduced EMI and ground response. I have alreay analyzed this coil concept a few years ago.

Aziz

I thought there might be a catch and thanks for the reply Aziz.

Some days with the gpx 5000,  there's some ground you know their gold there, but the detector, coil and settings just cannot penetrate through, as the ground is just too mineralized.

I thought I'd ask just in case.


Title: Re: The need for big deep gold detectors.
Post by: mylab on Sunday December 3 2017 00:06:42 AEDT AM
  

 I have already analyzed this coil concept a few years ago.

Aziz

Yes Aziz you certainly did as I remember and had saved your postings from another forum, as it was way back in 2008 when you describe the concentric coplanar (small ) Rx / (Large ) RX then in 2014  using a (large) TX / (small) RX.


Title: Re: The need for big deep gold detectors.
Post by: mylab on Sunday December 3 2017 00:30:56 AEDT AM
  
  
Quote from: Aziz

[/quote

SH forum? Where?


Here it is Aziz

http://www.detectorprospector.com/forum/forum/4-detector-prospector-forum/

Thanks!

In my opinion the video displaying the difference between a GPZ and GPX on the target before it was dug up then there is virtually nothing the GPZ had over the GPX other than the larger purchase price for the GPZ.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday December 3 2017 09:30:56 AEDT AM
Now look at this posting by jrbeatty:
http://www.detectorprospector.com/forum/topic/4731-how-deep-do-todays-detectors-go-compared-to-older-technology/?page=3
He shows a nice concentric coplanar coil.
::10 ::
Can't say, whether it is an IB coil or just a separate TX/RX coil (not induction balanced). But it could be well an IB coil.

I'm curious, what JP says this time. And the reaction of the members there.
::10 ::

Someone has obviously studied all my coil analysis results.
::62::


Title: Re: The need for big deep gold detectors.
Post by: Doug on Sunday December 3 2017 11:35:07 AEDT AM
  
Now look at this posting by jrbeatty:
http://www.detectorprospector.com/forum/topic/4731-how-deep-do-todays-detectors-go-compared-to-older-technology/?page=3
He shows a nice concentric coplanar coil.
::10 ::
Can't say, whether it is an IB coil or just a separate TX/RX coil (not induction balanced). But it could be well an IB coil.

I'm curious, what JP says this time. And the reaction of the members there.
::10 ::

Someone has obviously studied all my coil analysis results.
::62::

The last time I was in the shed with Jim at the caravan park he was working on  a big spider wound  litz wire IB  coil. One idea he had was to  be able to adjust the height of the  inner IB coil to assist with GB or nulling over mineralized ground. He could certainly make some good coils! One of his  larger mono coils  on a ML detector was easily the best i have ever seen for depth and  sensitivity. I think it was a once off and some lucky person may now be using it.
doug


Title: Re: The need for big deep gold detectors.
Post by: Doug on Sunday December 3 2017 13:17:19 AEDT PM
 Interestingly JRB has posted  on SH's forum that Jim was working on a ground loop system just prior to his death because the depth advantage over conventional coils is "staggering". Developing such a system  will be very challenging.
doug


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday December 3 2017 21:49:34 AEDT PM
Hi all,

the QED could have been a GPZ killer with minor changes and using a concentric coplanar IB coils.
I won't publish any details until BW is interested in the depth advantage.
(No, I'm not interested in money. I want to kill the GPZ! *LOL*)
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Doug on Sunday December 3 2017 22:13:27 AEDT PM
  
Hi all,

the QED could have been a GPZ killer with minor changes and using a concentric coplanar IB coils.
I won't publish any details until BW is interested in the depth advantage.
(No, I'm not interested in money. I want to kill the GPZ! *LOL*)
Aziz

I am sure the BW would be interested but  i don't know if the QED would run with a concentric coplanar IB coil.The QED will not run with DD coils. We could kill the GPZ with a small portable QED based ground loop system (a portable mini loop Tx). However their are very major technical challenges to developing such a system  but I  believe it  could be easier than trying to do it for  a ML gpx as  the late JS was.Eric foster also tested a g loop system here some years ago  but  have not heard any more about it.
doug


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday December 3 2017 23:01:11 AEDT PM
  
  
Hi all,

the QED could have been a GPZ killer with minor changes and using a concentric coplanar IB coils.
I won't publish any details until BW is interested in the depth advantage.
(No, I'm not interested in money. I want to kill the GPZ! *LOL*)
Aziz

I am sure the BW would be interested but  i don't know if the QED would run with a concentric coplanar IB coil.The QED will not run with DD coils. We could kill the GPZ with a small portable QED based ground loop system (a portable mini loop Tx). However their are very major technical challenges to developing such a system  but I  believe it  could be easier than trying to do it for  a ML gpx as  the late JS was.Eric foster also tested a g loop system here some years ago  but  have not heard any more about it.
doug

Well, the advantage can be implemented on mono coils as well. It only requires small changes in the TX part/snubber cct. If BW can manage separate concentric coplanar (large)TX/(small) RX coil designs in the QED, there is more depth advantage of course. With the concentric coplanar induction balanced coils, it is easier to manage it of course.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Monday December 4 2017 00:06:42 AEDT AM
  
  
  
Hi all,

the QED could have been a GPZ killer with minor changes and using a concentric coplanar IB coils.
I won't publish any details until BW is interested in the depth advantage.
(No, I'm not interested in money. I want to kill the GPZ! *LOL*)
Aziz

I am sure the BW would be interested but  i don't know if the QED would run with a concentric coplanar IB coil.The QED will not run with DD coils. We could kill the GPZ with a small portable QED based ground loop system (a portable mini loop Tx). However their are very major technical challenges to developing such a system  but I  believe it  could be easier than trying to do it for  a ML gpx as  the late JS was.Eric foster also tested a g loop system here some years ago  but  have not heard any more about it.
doug

Well, the advantage can be implemented on mono coils as well. It only requires small changes in the TX part/snubber cct. If BW can manage separate concentric coplanar (large)TX/(small) RX coil designs in the QED, there is more depth advantage of course. With the concentric coplanar induction balanced coils, it is easier to manage it of course.

Aziz

This would be great to see this happening, "the gpz killer"
I know James had his gpx 5000 up there with the gpz and even beat it in some cases.
So, one of these coils modified to be used on my gpx 5000 would make me a happy man. ::419::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 4 2017 08:45:32 AEDT AM
  
This would be great to see this happening, "the gpz killer"
I know James had his gpx 5000 up there with the gpz and even beat it in some cases.
So, one of these coils modified to be used on my gpx 5000 would make me a happy man. ::419::

Hi Digger,

I'm not familiar with the coil specifications and internals regarding the gpx 5000. According to the user manual, there is a Double-D mode (besides Monoloop and Cancel), which could allow us to make a pure concentric coplanar IB coil. As I have understood so far, there are only two internal coil windings TX and RX on pure Double-D coils. TX acts additionally as the second RX coil on Monoloop configuration with the Double-D coils.

Whereas the pure mono loop coil has only one internal coil winding (TX=RX).

I think it should be possible to make a pure concentric co-planar induction balanced coil. But I have no details and specifications regarding the coil (particularly the Double-D type of coil).

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 4 2017 09:44:42 AEDT AM
BTW guys,

I have designed a very KISS non-dissipative snubber circuit with TX coil energy recycling. It requires only 3 parts to implement it in the TX circuit. There is no ringing anywhere (this is the real feature, what makes it unique). No additional heat. Longer battery power duration or larger coil current.
The power dissipation of the TX circuit reduces almost to the half compared to the conventional snubber, when the TX coil is in the (almost) linear ramp up region (coil current not saturated).

There comes the depth advantage:
More power to the (larger) coil by keeping the power dissipation same.

This is a very very tricky circuit. BW could implement it in the next QED version with ease I think. I will keep it secret until BW won't be interested in it.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: bugwhiskers on Monday December 4 2017 16:55:37 AEDT PM
Great to see you back Aziz. Looking forward to your contributions in advancement of the art.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 4 2017 19:07:29 AEDT PM
Hi BW,

  
Great to see you back Aziz. Looking forward to your contributions in advancement of the art.

I have looked into the old qed schematics and checked it for a modification. Yep, it's quite easy to do and the solution would not require snubber drive part.
I have to show you the LTspice file simulation, if you pm me the missing data for:
- TX drive voltage (-V)
- TX mosfet type name (critical for simulation due to spec data)
- Blocking diode type name
- TX coil resistance, inductance, capacitance, damping resistor value
- TX pulse frequency, TX on pulse duration

I can make a comparison to the former solution with the snubber. In this case, I would need the mosfet type name of the subber part also. And when it is switched on/off (timing).

The snubber I have need to be carefully dimensioned (limitting to peak voltage, flyback duration, off-time duration for RX sampling). It does not need extra control lines. The efficiency of the snubber increases with the TX coil operated in the linear region (t on time << TC of the TX coil, coil current not saturated).
First step is to look for power saving. Next step is to increase the coil voltage to get more power to the TX coil with the same power consumption at the end as the previous design. I hope, we can get there.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Monday December 4 2017 22:52:35 AEDT PM
  
Hi BW,

  
Great to see you back Aziz. Looking forward to your contributions in advancement of the art.

I have looked into the old qed schematics and checked it for a modification. Yep, it's quite easy to do and the solution would not require snubber drive part.
I have to show you the LTspice file simulation, if you pm me the missing data for:
- TX drive voltage (-V)
- TX mosfet type name (critical for simulation due to spec data)
- Blocking diode type name
- TX coil resistance, inductance, capacitance, damping resistor value
- TX pulse frequency, TX on pulse duration

I can make a comparison to the former solution with the snubber. In this case, I would need the mosfet type name of the subber part also. And when it is switched on/off (timing).

The snubber I have need to be carefully dimensioned (limitting to peak voltage, flyback duration, off-time duration for RX sampling). It does not need extra control lines. The efficiency of the snubber increases with the TX coil operated in the linear region (t on time << TC of the TX coil, coil current not saturated).
First step is to look for power saving. Next step is to increase the coil voltage to get more power to the TX coil with the same power consumption at the end as the previous design. I hope, we can get there.

Cheers,
Aziz

Sounds like fun times ahead for you two boys.

I myself would love to see for this to happen.
The ground I was talking about earlier where no detector will work, might be the go for this coil.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 5 2017 02:43:29 AEDT AM
Hi guys,

*** Good News ***
A preliminary circuit simulation shows, that the power consumption of the TX-part can be reduced from approx.
1.9 W -> 1 W  (preliminary, missing infos yet)
::62:: Nice.
BW have to give me more detailed infos via pm so I can be more accurate and finalize the circuit simulation for him.
We have approx. 0.9 W to push more into the ground. But I think, we have a limitation to 200 V breakdown voltage.
I have to simulate the previous circuit to get some more required infos.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Doug on Tuesday December 5 2017 10:24:49 AEDT AM
BW has tried using a higher voltages on the QED but they did not result in any improvement  in detection depth.All they achieved was a larger battery drain.
doug


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 5 2017 12:40:56 AEDT PM
  
BW has tried using a higher voltages on the QED but they did not result in any improvement  in detection depth.All they achieved was a larger battery drain.
doug

Hi Doug,

theory is promissing more. There must be other reasons.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 5 2017 13:03:14 AEDT PM
Hi all,

now the power dissipation of the transmitter with the correct TX pulse train:
938 mW (old)
505 mW (new snubber)
not bat.

Unfortunately, the new snubber has some design disadvantages. Can't tell you now.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 5 2017 21:25:20 AEDT PM
Hi all,

now I have really bad news:
The new snubber can't be used in the QED. Pity!
It is owed to the fact of the design limitations (two major disadvantages, which dominates over power saving feature).

But the new subber can be used for Corbyn like PI's.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Tuesday December 5 2017 23:24:25 AEDT PM
  
Hi all,

now I have really bad news:
The new snubber can't be used in the QED. Pity!
It is owed to the fact of the design limitations (two major disadvantages, which dominates over power saving feature).

But the new subber can be used for Corbyn like PI's.

Cheers,
Aziz


Where there's a will, there's a way.

Hi Aziz,
It's there a bridge or a bypass that can be used to overcome this dead end?
I don't know anything about electronics,  so I'm just asking questions. Sometimes, by asking questions, we get to understand what you technology savvy boys are doing and saying.  ::402::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 5 2017 23:43:25 AEDT PM
  
  
Hi all,

now I have really bad news:
The new snubber can't be used in the QED. Pity!
It is owed to the fact of the design limitations (two major disadvantages, which dominates over power saving feature).

But the new subber can be used for Corbyn like PI's.

Cheers,
Aziz


Where there's a will, there's a way.

Hi Aziz,
It's there a bridge or a bypass that can be used to overcome this dead end?
I don't know anything about electronics,  so I'm just asking questions. Sometimes, by asking questions, we get to understand what you technology savvy boys are doing and saying.  ::402::

Hi Digger,

no unfortunately, there isn't any benefit for the qed limitted by the circuit design of the new snubber. I can't talk about it at the moment until BW says "I can't use it so give it to the public." In case of he gives his ok, I'll publish the basic snubber circuit only for discussion. But nothing qed related internals of course.

The new snubber can be used under certain circumstances however. And there is a benefit of course.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: mylab on Wednesday December 6 2017 01:16:59 AEDT AM
  

I can't talk about it at the moment until BW says "I can't use it so give it to the public." In case of he gives his ok, I'll publish the basic snubber circuit only for discussion. But nothing qed related internals of course.

Cheers,
Aziz

Good on you Aziz, very decent of you.

Cheers.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 6 2017 20:31:20 AEDT PM
Hi all,

the journey continues on: Chasing the big and deep gold in highly mineralized ground.
Anyone got an idea?

Aziz


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Thursday December 7 2017 00:35:42 AEDT AM
Idea?
We all waiting on you for new ideas, Aziz.
But ....
Probably this small program code could help:

A. Deep plowing and then using known detector.
B. IF nothing found , GO TO A. again.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 7 2017 20:26:44 AEDT PM
  
Idea?
We all waiting on you for new ideas, Aziz.

Hi WM6 and others,

I'm sorry, but my most favourite idea has not been implemented yet.

The idea is not new.

Go for a separate concentric co-planar (large) TX / (small) RX with moderate coil current increase
Go for a separate concentric co-planar (large) TX / (small) RX with moderate coil current increase
Go for a separate concentric co-planar (large) TX / (small) RX with moderate coil current increase

It has not to be an induction balanced coil. It's very easy to build.

Large and deep signals are usually smooth and broad and fall often through the processing stages (filters).
The coil configuration above makes these signals more sharp and pronounced. *Yeah*
You have less EMI noise induction and less ground response. *Yeah*
The detection section of the RX coil is sensing deep going magnetic fields as they will be less refracted on the center of the coil (magnetic shield effect). *Yeah*
The increase of coil current makes really sense in this configuration. It's not a waste of power. *Yeah*
And the coil configuration is best for small and large target detection *Yeah*
(There are more benefits however .. )

What the f*****g hell are you guys waiting for?
What the f*****g hell are you guys waiting for?
What the f*****g hell are you guys waiting for?
(A free gala dinner maybe?)

This is the best solution I can give you all. And it has already been thoroughly analyzed and proven.
::62::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Goldman on Thursday December 7 2017 20:29:04 AEDT PM
So who can build these coils (of the future).


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 7 2017 20:51:07 AEDT PM
BTW,

the coil arrangement can also be realized as a single inductor TX/RX but tapped on the smaller coil part acting as RX coil in the receive period. Something like a tapped dual field coil configuration.

But I for one would make two physical coils: separate large TX and smaller RX coil.
As we have more space for both windings, we can cheat a bit with loose coil bundles (coil bundles using more space) to have more coil windings  for a specified coil inductance. Basket weave or spiral coils for both TX and RX coil can be realized with ultra fast coil damping feature. We have simplicity in the electronics part too.

But you can not buy such coils yet and you have to build it finally.

I can make proposals for a front-end change to the QED. It isn't difficult.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday December 7 2017 21:19:09 AEDT PM
Hi Aziz, do I remember correctly from a few years ago your best graphs showed that the best ratio of a large TX to small RX was 2:1 that is a 10 inch TX and a 5 inch RX ?

I had a bit of a play with this type of coil .


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 7 2017 22:57:39 AEDT PM
  
Hi Aziz, do I remember correctly from a few years ago your best graphs showed that the best ratio of a large TX to small RX was 2:1 that is a 10 inch TX and a 5 inch RX ?

I had a bit of a play with this type of coil .

Hi 4six,

I can't remember the optimal ratio anymore. But you're doing well with 2:1 ratio (TX:RX diameter).
If the RX is a spiral /basket weave coil, it can even start from almost of the center of the coil. Maybe a small hole in the coil center might be usefull for pinpointing.
You can of course make the RX upto to 2/3 diameter of the coil. But then you're dealing with more ground and EMI noise induction.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Thursday December 7 2017 23:45:45 AEDT PM
  
  
Idea?
We all waiting on you for new ideas, Aziz.

Hi WM6 and others,

I'm sorry, but my most favourite idea has not been implemented yet.

The idea is not new.

Go for a separate concentric co-planar (large) TX / (small) RX with moderate coil current increase
Go for a separate concentric co-planar (large) TX / (small) RX with moderate coil current increase
Go for a separate concentric co-planar (large) TX / (small) RX with moderate coil current increase

It has not to be an induction balanced coil. It's very easy to build.

Large and deep signals are usually smooth and broad and fall often through the processing stages (filters).
The coil configuration above makes these signals more sharp and pronounced. *Yeah*
You have less EMI noise induction and less ground response. *Yeah*
The detection section of the RX coil is sensing deep going magnetic fields as they will be less refracted on the center of the coil (magnetic shield effect). *Yeah*
The increase of coil current makes really sense in this configuration. It's not a waste of power. *Yeah*
And the coil configuration is best for small and large target detection *Yeah*
(There are more benefits however .. )

What the f*****g hell are you guys waiting for?
What the f*****g hell are you guys waiting for?
What the f*****g hell are you guys waiting for?
(A free gala dinner maybe?)

This is the best solution I can give you all. And it has already been thoroughly analyzed and proven.
::62::
Aziz


Ok, I'm ready to place an order for one of these coils.

Anyone ready to take my order?

Coil needs to be made, tested and shown results.  ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 8 2017 10:17:52 AEDT AM
  
Ok, I'm ready to place an order for one of these coils.

Anyone ready to take my order?

Coil needs to be made, tested and shown results.  ::62::

Hi Digger,

you can't use such coils in current PI detectors yet. We can not control the TX pulse power (for modarate power increase). If you change it, you have to change the window timings as well (and adapting the GB is not trival). The coil damping internals in the detector needs to be changed as well. Both TX and RX coils need an individual coil damping resistors. This has not been taken into account in the current PI detectors yet.

1. But a QEDspecial could be made (with modarate power increase).

2. Or just an coil adapter plug (or cable) with the current QED to realise the individual TX coil damping in the adapter housing. The damping of the RX coil takes place in the metal detector electronics (as before and just acting like a Double-D coil configuration) . With this adapater plug, one could use such coils in the QED without the need for power change in the first place. Provided that the QED allows more compensation gain. As we have less EMI noise and ground noise, we can crank up the gain instead of increasing the coil power. We have to increase the gain, as we also have a smaller RX coil and less detecting signals. At the end of the math, there should be a depth increase. Particularly for large TX/RX coils.

The required additional compensation gain is related to the relation of TX to RX coil diameter size.

The special version (1.) needs a firmware change due to power increase and involved window timings change. This would take a longer time to implement. But it would give the ultimate depth increase. The adapter plug (2.) is much simpler of course.

Cheers,
Aziz

PS: uuuups. Version 2 could maybe made for SD, GPX series detectors as well. Oh fugg!, I see a GPZ-Killer with GPX machines coming... *LOL*
Where are the third party coil makers???????


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Friday December 8 2017 10:21:06 AEDT AM
  
  

Hi WM6 and others,

I'm sorry, but my most favourite idea has not been implemented yet.

The idea is not new.

Go for a separate concentric co-planar (large) TX / (small) RX with moderate coil current increase

What the f*****g hell are you guys waiting for?

This is the best solution I can give you all. And it has already been thoroughly analyzed and proven.
::62::
Aziz


Ok, I'm ready to place an order for one of these coils.
Anyone ready to take my order?
Coil needs to be made, tested and shown results.  ::62::

It is not problem to build testing PI coil (Ihave a lot of such coils), but need more data or clarification from Aziz.

Aziz wrote:

"Go for a separate concentric co-planar (large) TX / (small) RX"  - OK, this is clear or at least should be.

"with moderate coil current increase"  -   this is not clear. If we presume that pulse level is 12V, we still
                                                              need to know how "moderate" coil current should be. This mean
                                                              we need to know coil resistance and coil impedance along with
                                                              pulse duration. Suit any PI model to this requirements (par example
                                                              regarding pps regime)?

"This is the best solution I can give you all. And it has already been thoroughly analyzed and proven."

Where? In Corbyn ideas?

Again we are here with depth and problem of target identification.

There is no problem with target identification till  I dig to 15cm or so of depth.
It is easy to dig an identified shallow targets (good and trash).
Even 100 or more per day - no problem.

But who is ready to dig say 5 holes 1,2 meter deep per day for nothing, cause
my "deeper PI" is not able of target identification on reliable way? Probably no one.

It is pure nonsense to conduct debates about PI detectors which can go meter and more
of depth, if such detector are not able to differentiate between old fish can and gold nugget
at such depth.  

So " f*****g things we are waiting for", is secure target identification at all depth in
first line and not bother with archaic Corbin ideas, and depth that no one is ready
to dig for nothing.

Of course those with solution for problem mentioned above will go to one of
main producer and not to public disclose.

Mean it is nothing to waiting for in public domain.



Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 8 2017 10:37:49 AEDT AM
Ok,

you guys need more coil simulation results.

I'll do them again. Now particularly for separate (large)TX / (small) RX coils with variation of the size relation. It will take some time however. So 1-2 weeks or so.

This is going to be very very interesing stuff.
I'm looking forward to your fascinating eyes. You can swing large coils on heavy mineralized grounds soon.
Be prepared to make the adapter plug and the TX/RX coils.
The GPZ-Killer is coming soon.. with a GPX!!! *LOL*

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 8 2017 10:50:42 AEDT AM
  
It is not problem to build testing PI coil (Ihave a lot of such coils), but need more data or clarification from Aziz.

Aziz wrote:

"Go for a separate concentric co-planar (large) TX / (small) RX"  - OK, this is clear or at least should be.

"with moderate coil current increase"  -   this is not clear. If we presume that pulse level is 12V, we still
                                                              need to know how "moderate" coil current should be. This mean
                                                              we need to know coil resistance and coil impedance along with
                                                              pulse duration. Suit any PI model to this requirements (par example
                                                              regarding pps regime)?

"This is the best solution I can give you all. And it has already been thoroughly analyzed and proven."

Where? In Corbyn ideas?

Again we are here with depth and problem of target identification.

There is no problem with target identification till  I dig to 15cm or so of depth.
It is easy to dig an identified shallow targets (good and trash).
Even 100 or more per day - no problem.

But who is ready to dig say 5 holes 1,2 meter deep per day for nothing, cause
my "deeper PI" is not able of target identification on reliable way? Probably no one.

It is pure nonsense to conduct debates about PI detectors which can go meter and more
of depth, if such detector are not able to differentiate between old fish can and gold nugget
at such depth.  

So " f*****g things we are waiting for", is secure target identification at all depth in
first line and not bother with archaic Corbin ideas, and depth that no one is ready
to dig for nothing.

Of course those with solution for problem mentioned above will go to one of
main producer and not to public disclose.

Mean it is nothing to waiting for in public domain.



Hi WM6,

modarate TX coil current increase just means 1.5 to 2 times. Not more. That's enough for a good detection depth increase. Particularly for those large coils. See my previous post also. We don't need changes to the detector, when the detector has enough gain for adjustments. We need a new coil adapter plug and the new TX/RX coil. Or the new TX/RX coil with the inbuilt adapter.

You haven't understood the principle yet. I'll show you and clarify this with new coil simulations.
You can not discriminate. No one can do it. You have to dig all targets.
I know many people, who are really willing to dig sooooo deeeeeeeeep, when they know, it's a target signal there. In the gold fields.
You may leave the signals for us. But mark them with X please.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday December 8 2017 11:25:51 AEDT AM
moderate TX coil current increase just means 1.5 to 2 times



Aziz when you say an increase in coil current are you talking about increaseing the TX pulse width ?
what is the starting current reference ?


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 8 2017 11:30:48 AEDT AM
Yeah,

I'm going to open up the gold fields again. ::620::
With just a new coil, an adapter plug and the GPX.


I may correct JP on the following posting first:
http://www.detectorprospector.com/forum/topic/4731-how-deep-do-todays-detectors-go-compared-to-older-technology/?page=4

SALT is not going to be an issue with large coils. It's the (magnetic) ground response.

Secondly, I can't imagine, that someone has made a seperate TX/RX coil for a GPX machine. The posting by jrbeatty regarding the mysterius coil could also be a dual field coil. Hey, if they (the coil makers) really realised the separate TX/RX coil for the GPX, than hats off! (But I know, where your idea comes from! *LOL*)

Who is willing to open up the gold fields again???
How far can the gain on the GPX be cranked up? Will it be enough? If not, we have to make the RX coil a bit larger but overall smaller than the TX coil of course.

I for one would take the QED instead of the GPX. Its easier to mod the gain stage in worst case situation. Where is Woody? We need a gain mod in worst case.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 8 2017 11:38:08 AEDT AM
  
moderate TX coil current increase just means 1.5 to 2 times



Aziz when you say an increase in coil current are you talking about increaseing the TX pulse width ?
what is the starting current reference ?

Yep, you can achieve this by increasing the TX pulse width (when the coil current has not already been saturated) or increasing the transmitter power supply voltage. That's not relevant how to do it. We need slighty more TX coil current. Even 1.2 times more coil current should give some benefit.

But we don't need to increase the coil current. We can compensate it with higher RX gain.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday December 8 2017 14:12:54 AEDT PM
Hi Aziz I look forward to any new graphs that you make
I have been trying to find the old graphs you made on my old computers
but its mainly dual field stuff i still have.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 8 2017 20:41:23 AEDT PM
  
Hi Aziz I look forward to any new graphs that you make
I have been trying to find the old graphs you made on my old computers
but its mainly dual field stuff i still have.


I'm preparing the TX/RX coil analysis for the bundle and spiral/basket weave type coils. More accurately this time, which is consuming a lot of CPU time.
It seems, that I have to learn how to use my coil software again.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 8 2017 21:00:58 AEDT PM
Hi all,

we have two options for the depth increase with the separate TX/RX coils:
- Increasing the TX coil current -> complex detector changes required -> many issues -> bad idea
- Decreasing the pre-amp noise (thermal noise of the amplifier) -> easy -> good idea

My 0.4 nV/sqrt(Hz) noise density ultra low noise pre-amp is getting important now.
::10::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Friday December 8 2017 23:26:35 AEDT PM
  
  
moderate TX coil current increase just means 1.5 to 2 times



Aziz when you say an increase in coil current are you talking about increaseing the TX pulse width ?
what is the starting current reference ?

Yep, you can achieve this by increasing the TX pulse width (when the coil current has not already been saturated) or increasing the transmitter power supply voltage. That's not relevant how to do it. We need slighty more TX coil current. Even 1.2 times more coil current should give some benefit.

But we don't need to increase the coil current. We can compensate it with higher RX gain.

Aziz

Hi Aziz,
The gpx 5000 RX gain goes up to 20 and so does the stabiliser.
To work the gpx 5000 with these two maxed out is that it creates too much noise.
How will increasing the RX gain do the trick?


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 9 2017 06:04:13 AEDT AM
  
Hi Aziz,
The gpx 5000 RX gain goes up to 20 and so does the stabiliser.
To work the gpx 5000 with these two maxed out is that it creates too much noise.
How will increasing the RX gain do the trick?

Hi Digger,

gain 20 is relative. It does not say how much decibel or times factor.
It would be great to know the dB or times factor for each gain step. We can calculate or obtain the minimum RX coil size.

Nevertheless, we don't even have to know it. The main goal is to use large coils (18 inch and larger) on these heavily mineralized gold fields, where standard mono coils with same size can not be operated at high gain stages. We will obtain a better operation due to less ground noise, better (sharper) detection signal and larger detection depth.

"How will increasing the RX gain do the trick?"
As we can not increase the TX coil power (we do not want to modify the detector electronics nor the software or we can't do it either), we can increase the RX gain. It's the same trick.

We don't detect as much ground signal as well as EMI noise with the smaller RX coil compared to the larger mono coil. And we have some loss of detection signal due to smaller RX coil size too. So we can increase the RX gain savely. At the end of the calculation, we get more sensitivity and detection depth at the center of the coil.
Second important feature is, that at the center of the coil, highly mineralized ground will be penetrated deeper as the magnetic fields won't be refracted much (penetrating almost perpendicular the ground) and the ground has less magnetic shielding effect at the center therefore. Guess, where the sensing windings (RX) sitting to detect all the deep going magnetic fields?  Right, at the center of the coil. We don't detect magnetic field lines coming almost horizontal from the ground (these are dominant and strong on standard mono coils). Only almost vertical magnetic fields.

Well, you all will see, what is going to happen soon! The GPZ-Killer is coming... ::620::
I hope, the third party coil makers (aftermarket coil makers) will produce such separate (large) TX/ (small) RX coils for you!
The sooner, the better.  ::10 ::
I'll give my best, to speed up the development.

The QED should be able to use such coils. Yeah, it will be a GPZ-Killer!

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 9 2017 20:33:19 AEDT PM
Hi all,

I have looked at the coil plug wiring for the SD, GP, GPX, QED series detectors. The damping of the TX coil is done in the detector box. We have to damp the RX coil somewhere else then.
There is a very elegant solution for the lack of enough gain for the RX coil: an additional small box containing an ultra-low-noise amplifier and the damping resistors for the RX coil. There we have it.

Separate TX/RX coil -> coil plug -> small control box -> standard coil plug -> detector

The detector gain can even be set down as the amplifier in the control box should perform better (we want to use better amplifiers of course).

Without the control box solution, the RX coil damping can be done inside the coil plug if there is enough space for the resistors. Otherwise, a smaller control box is needed. In the first stage, we wouldn't require an amplifier in the box as the detector allows some more gain. In case of it isn't high enough, we would need an amplifier.

Let's find out the required RX gain compensation for each coil simulations first.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 9 2017 22:43:21 AEDT PM
Hi all,

I forgot to mention, that we can increase the RX coil inductance a bit (more loop turns) to compensate for RX gain. This is not critical as it would add some weight and capacitance to the RX coil. But we can use thinner wire for the RX coil. Then we wouldn't require any amplifier box. It would make things much much easier for us.

The rest of the gain compensation is made in the detector (just adjusting the gain up).
The GPZ-Killer is coming...
Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Sunday December 10 2017 15:22:15 AEDT PM
Hi Aziz,

You might have got me out of retirement from coil building I have the coaxial coil still that we worked on a few years ago and today dug out one of my prototype TEM coils from the GG Tinkerer project it is coaxial has a Litz TX coil 280 uh .4 ohms the RX was differential so I have run the wires in series so I now have a Litz RX of 810 uh and 6.1 ohms I will have to dig out the processor controlled SD2000M to test it as the QED with the current front end will not run induction balanced coils I still have to hook the coil up to check what has happened to the induction balance as it was balanced with the differential set up.

Regards, Ian.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 11 2017 19:39:32 AEDT PM
  
Hi Aziz,

You might have got me out of retirement from coil building I have the coaxial coil still that we worked on a few years ago and today dug out one of my prototype TEM coils from the GG Tinkerer project it is coaxial has a Litz TX coil 280 uh .4 ohms the RX was differential so I have run the wires in series so I now have a Litz RX of 810 uh and 6.1 ohms I will have to dig out the processor controlled SD2000M to test it as the QED with the current front end will not run induction balanced coils I still have to hook the coil up to check what has happened to the induction balance as it was balanced with the differential set up.

Regards, Ian.

Hi Ian,

I am happy you are doing well in the meantime.

Our goal is to make coils as simple as possible & cheap. We don't need induction balanced coils at the moment.
Does the current QED works with Double-D coils (with these stock Minelab compatible coils)?

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 11 2017 20:58:32 AEDT PM
Hi all,

I have been making different coil models for my coil simulation software. I have not finished it yet however.

But first quick results show its huge benefits. Pity, that I can't show you the ground shield effect in my software so I have to draw some sketches to illustrate this.

Don't forget the main goal:
Detecting big deep gold deeper than what is currently possible on (heavy) mineralized ground.

We can achieve this without any modifications to the detector electronics (except adding damping resistors on the RX coil side). To get this working, we have to reduce the RX coil capacitance by evenly distributing the RX coil windings into some volume space. We can get a gain compensation factor of at least 2 and the rest will come from increasing the gain in the detector. I don't recommend pure flat spiral coils for such coils, as the coil capacitance isn't good enough. Basket weave coils are much better in this case.

Cheers,
Aziz
PS: The GPZ-Killer is coming...


Title: Re: The need for big deep gold detectors.
Post by: Doug on Monday December 11 2017 21:43:49 AEDT PM
  
  
Hi Aziz,

You might have got me out of retirement from coil building I have the coaxial coil still that we worked on a few years ago and today dug out one of my prototype TEM coils from the GG Tinkerer project it is coaxial has a Litz TX coil 280 uh .4 ohms the RX was differential so I have run the wires in series so I now have a Litz RX of 810 uh and 6.1 ohms I will have to dig out the processor controlled SD2000M to test it as the QED with the current front end will not run induction balanced coils I still have to hook the coil up to check what has happened to the induction balance as it was balanced with the differential set up.

Regards, Ian.

Hi Ian,

I am happy you are doing well in the meantime.

Our goal is to make coils as simple as possible & cheap. We don't need induction balanced coils at the moment.
Does the current QED works with Double-D coils (with these stock Minelab compatible coils)?

Cheers,
Aziz

The QED  front end  is incompatible with DD coils as i understand it. BW can  possibly expand on this.I think BW has also tried an coiltek anti interference coil on it but i can't remember  what happened.
doug


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 11 2017 22:09:11 AEDT PM
  
The QED  front end  is incompatible with DD coils as i understand it. BW can  possibly expand on this.I think BW has also tried an coiltek anti interference coil on it but i can't remember  what happened.
doug

Hi Doug,

I would be very happy to know the exact reasons. It would affect the new coil design and how to get around the issues.
I'm interested in the DD coil issue regarding the QED.

The new coil design is promissing so much.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Doug on Monday December 11 2017 22:24:48 AEDT PM
  
  
The QED  front end  is incompatible with DD coils as i understand it. BW can  possibly expand on this.I think BW has also tried an coiltek anti interference coil on it but i can't remember  what happened.
doug

Hi Doug,

I would be very happy to know the exact reasons. It would affect the new coil design and how to get around the issues.
I'm interested in the DD coil issue regarding the QED.

The new coil design is promissing so much.

Cheers,
Aziz

The QED front end is patent pending and unique  but i don't know the technical or electronic reasons as to why it does not like a DD coil.
doug


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 11 2017 22:31:15 AEDT PM
  
The QED front end is patent pending and unique  but i don't know the technical or electronic reasons as to why it does not like a DD coil.
doug

I can imagine the real reason. I have seen the front-end of the QED and the patent in question is prior art.
The RX coil damping is missing too.
If this is the reason, there won't be any issue with the new coils.
Anyway, BW should give me more details to solve the DD coil issue.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Doug on Monday December 11 2017 22:39:33 AEDT PM
  
  
The QED front end is patent pending and unique  but i don't know the technical or electronic reasons as to why it does not like a DD coil.
doug

I can imagine the real reason. I have seen the front-end of the QED and the patent in question is prior art.
The RX coil damping is missing too.
If this is the reason, there won't be any issue with the new coils.
Anyway, BW should give me more details to solve the DD coil issue.

Aziz

What patent are you referring too? The schematics of the current  production QED have NOT been published even on this forum to the best of my knowledge.
doug


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 11 2017 22:56:42 AEDT PM
  
What patent are you referring too? The schematics of the current  production QED have NOT been published even on this forum to the best of my knowledge.
doug

BW sent me the current frond-end schematics part.
I also have an improvement, which should be done in future QED's.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Doug on Monday December 11 2017 23:04:18 AEDT PM
  
  
What patent are you referring too? The schematics of the current  production QED have NOT been published even on this forum to the best of my knowledge.
doug

BW sent me the current frond-end schematics part.
I also have an improvement, which should be done in future QED's.
Aziz

Ok fair enough! But  do they explain why the QED does not like DD coils?
doug


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 11 2017 23:11:18 AEDT PM
  
Ok fair enough! But  do they explain why the QED does not like DD coils?
doug

Yes.  Partly.

But we can solve the issue easily.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 12 2017 03:45:38 AEDT AM
Hi guys,

I have good news for you.

The QED can handle the separate TX/RX coils. We have to add appropriate damping resistors to the RX coil part. This can be done in a small adapter box at the end of the coil cable/plug.

But we have to solve the Double-D coil issue first. I know exactly where the problem is.

The GPZ-Killer is becoming real. ::406::

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 12 2017 11:04:19 AEDT AM
Hi all,

I have solved the Double-D coil issue. And this is prior art too.
The TX/RX coil is easy to build.
So there is nothing to stop you chasing and digging the real big deep gold on super hot grounds soon.
::62::
Let's make the coil calculations now...
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Blacksand on Tuesday December 12 2017 16:30:18 AEDT PM
Hi Aziz.

Are you refering to a concentric coil. I'm thinking of building one but have read a rumor that Nexus are bringing out a large carbon fibre concentric coil for Minelab p.i. detectors.

Cheers Martin




Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 12 2017 19:13:33 AEDT PM
  
Hi Aziz.

Are you refering to a concentric coil. I'm thinking of building one but have read a rumor that Nexus are bringing out a large carbon fibre concentric coil for Minelab p.i. detectors.

Cheers Martin

Hi Martin,

yes, I'm referring to a concentric coil. But coils ain't coils.
The coils I am talking about can't be bought yet. We must build them until coil maker companies copy us (most desired!!!). Note, that we are defining the leading edge of the coil technology. *LOL*

In the coil housing there are two physical independent and separate coils:
A large transmit coil (TX) and a smaller concentric co-planar receive coil (RX). We have a coil coupling factor k of appox. 0.2 to 0.3 between the coils, therefore it isn't an induction balanced coil.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: authere on Tuesday December 12 2017 22:22:17 AEDT PM
Hi Aziz,

What size coils are you thinking of working with, the large coil I hear most using out there is the 25" coil, Bob Hollins made a 30" and I know a few guys had success with that but the main thing is their weight was kept to a minimum, if the weight does become a problem we could always use the u-beaut harness they are using for the GPZ, that's like walking around with a crane attached to your back...so food for thought


Cheers,Ron


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Wednesday December 13 2017 00:08:00 AEDT AM
  
Hi all,

I have solved the Double-D coil issue. And this is prior art too.
The TX/RX coil is easy to build.
So there is nothing to stop you chasing and digging the real big deep gold on super hot grounds soon.
::62::
Let's make the coil calculations now...
Aziz

Hi Aziz and IB GOLD.
I haven't been able to log on because I get a page saying the site is shut down.

Doug,  maybe someone doesn't want us talking about a gpz killer.

Aziz, in regards to the coil size, anything smaller than an 18" coil won't do any good?
And, so the gpx detector doesn't need to be modified but the coil needs a resistor or something like that?
Where would it be installed on the coil?
Thanks, sd220 Digger


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Wednesday December 13 2017 00:11:35 AEDT AM
By the way Doug, I'm using Firefox and even this still gets the error message and I have trouble getting on.
Anyway to get this fixed?


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 13 2017 00:19:33 AEDT AM
  
Hi Aziz,

What size coils are you thinking of working with, the large coil I hear most using out there is the 25" coil, Bob Hollins made a 30" and I know a few guys had success with that but the main thing is their weight was kept to a minimum, if the weight does become a problem we could always use the u-beaut harness they are using for the GPZ, that's like walking around with a crane attached to your back...so food for thought


Cheers,Ron

Hi Ron,

it is up to you what size of coil you prefer and can swing it. As long as the coil specifications meet the detector specs, everything is ok. To save some weight, the coil could be made elliptical of course. The RX coil could be made of thin wire (saving weight too). Ideal coil size is 14 inch and greater (20+ inch).

Remember, this separate TX/RX coil is specially designed for:
- Extremely mineralized ground, where the most coils fail due to extreme ground mineralization and hence ground response and you have to operate the detector with lower gain or smaller coils.

- Detecting deep targets (big deep gold) on heavy mineralized ground with sharp and safe detection response (better pin-pointing possibility). The RX coil is focussing to the deep penetrating magnetic fields, where all the other magnetic fields outside the RX coil tend to go almost shallow and horizontal to the ground mineralization layer and causing a lot of ground response. The coil is an "Iron-Shield" penetrater coil.  Remember, the big deep gold is producing a broad and faint detection signal and you can't distinguish it in most cases with ground response or EMI noise. This coil will help to enhance the deep signals. It is also convenient for shallow small gold of course.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 13 2017 00:46:54 AEDT AM
  

Hi Aziz and IB GOLD.
..
Aziz, in regards to the coil size, anything smaller than an 18" coil won't do any good?
And, so the gpx detector doesn't need to be modified but the coil needs a resistor or something like that?
Where would it be installed on the coil?
Thanks, sd220 Digger

The principle of the separate TX/RX coil applies to all coil sizes. You can make it of any size. But not all coil sizes make sense of course (like smaller than 9 inch or so). But we want to chase the big deep gold missed by the others. Then you have to use big coils (14+ inch).

I don't know the internals of the GPX detector. The detector could have built-in RX coil damping resistor inside and it could be activated by a switch position (Double-D switch). We maybe would need an optinal switch in the coil adapter box to activate/switch-off the external RX coil damping resistors in such cases. Someone with a SD/GPX detector have to try it.

I will focus the QED in the first instance because I know, how its front-end is made. And we don't want to modify any detectors.

The RX coil damping resistors (and the optional switch) will be placed in a small adapter box at the end of the coil cable.

Illustration:
Coil housing -> long coil cable (2-3 m) -> small coil adapter box (RX damping + switch) -> short coil cable (20 - 30 cm) -> coil plug (5 pin standard coil plug) -> detector.
That's it.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: egixe4 on Wednesday December 13 2017 10:23:15 AEDT AM
  
By the way Doug, I'm using Firefox and even this still gets the error message and I have trouble getting on.
Anyway to get this fixed?

I'm getting the same error,
hit the back button after the error screen comes up and sign in again, works for me.



Title: Re: The need for big deep gold detectors.
Post by: Goldman on Wednesday December 13 2017 14:02:45 AEDT PM
  
  
By the way Doug, I'm using Firefox and even this still gets the error message and I have trouble getting on.
Anyway to get this fixed?

I'm getting the same error,
hit the back button after the error screen comes up and sign in again, works for me.



Can also click the “retry for a live version” button at the top LH side of the error page to bring up the forum page you selected before the error


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday December 13 2017 15:55:23 AEDT PM
Aziz where do you want the shield connection RX or TX side this is a 16" coil but it is a start I will test with SD2000m then add RX damping and test with QED then try the GPX5000 probably more suited to the 2000 as with that I can adjust the pulse train the TX voltage and the RX gain front end and post integrator stages looks like some fun when it cools down.

Regards, Ian.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 13 2017 20:47:21 AEDT PM
  
Aziz where do you want the shield connection RX or TX side this is a 16" coil but it is a start I will test with SD2000m then add RX damping and test with QED then try the GPX5000 probably more suited to the 2000 as with that I can adjust the pulse train the TX voltage and the RX gain front end and post integrator stages looks like some fun when it cools down.
Regards, Ian.

Hi Ian,

wait until I have finished the coil simulations and show the final results.
QED requires tight coil specs and individual RX coil damping to work with these new coils at the moment.

Regarding the Double-D coil issue on QED:
The high voltage input protection circuit is critically adjusted for 0.4 Ohm mono coils. On a standard ML-compatible Double-D coil the RX coil winding can have 5 - 15 Ohms. This high impedance coil part is mismatching the critical adjustment in the front-end is producing a considerable DC-offset voltage, which is then amplified by the pre-amp. That's the cause at the moment.
We can make the RX coil part with same 0.4 Ohm specs and can hope, the QED will have enough gain adjustment.

Regarding other detectors: wait until we know more.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Wednesday December 13 2017 21:01:27 AEDT PM
  
Aziz where do you want the shield connection RX or TX side this is a 16" coil but it is a start I will test with SD2000m then add RX damping and test with QED then try the GPX5000 probably more suited to the 2000 as with that I can adjust the pulse train the TX voltage and the RX gain front end and post integrator stages looks like some fun when it cools down.

Regards, Ian.

Hi Ian,
This is good news with the coil you're working on.
You say that the coil will be better suited to the SD2000
I have the gpx 5000, do you think this coil can be made to work as you
Say with the SD2000?

Thanks, sd220 Digger


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Wednesday December 13 2017 21:06:54 AEDT PM
  
  
By the way Doug, I'm using Firefox and even this still gets the error message and I have trouble getting on.
Anyway to get this fixed?

I'm getting the same error,
hit the back button after the error screen comes up and sign in again, works for me.



Thanks for the tips.
It seems that Firefox and google have this error coming up.
By pressing the back button seems to do the trick.
But why is this error coming up in the first place???


Title: Re: The need for big deep gold detectors.
Post by: Doug on Wednesday December 13 2017 21:20:42 AEDT PM
  
  
  
By the way Doug, I'm using Firefox and even this still gets the error message and I have trouble getting on.
Anyway to get this fixed?

I'm getting the same error,
hit the back button after the error screen comes up and sign in again, works for me.



Thanks for the tips.
It seems that Firefox and google have this error coming up.
By pressing the back button seems to do the trick.
But why is this error coming up in the first place???


Error 502 Bad Gateway: Where’s the problem?
https://www.1and1.com/digitalguide/hosting/technical-matters/what-does-502-bad-gateway-mean-explanation-and-solution/
doug


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 13 2017 22:41:02 AEDT PM
Hi all,

has anyone one of the new elite coils for ML GP/SD/GPX series detectors?

I am particularly referring to the 18 inch elite variant:
See here:
http://www.coiltek.com.au/coils/elite/18-elite/

Is anyone willing to do some measurements for me? I have to know, whether the coil makers already use the separate TX/RX coil technology. I just want to know, whether there is a large TX coil and a smaller RX coil inside coil housing.

The measurements on the coil plug pins:
TX part:
1. Inductance between pin 4 and 5
2. DC resistance between pin 4 and 5

RX part:
3. Inductance between pin 1 and 2
4. DC resistance between pin 1 and 2

5. DC resistance between pin 2 and 4:
either short circuit (zero ohms) or high impedance (not measureable resistance) or some resistance.

I have to know these values. These simple measurements will answer my question.
Thanks in advance. Any other new coil measuerement would do it either. It must be the new ones however.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 13 2017 22:52:28 AEDT PM
Hi guys,

I have made several coil models and finished the coil simulation calculations.
It will take some time to show them in a nice Excel sheet.
(Not today. The weather here is nice and I'm heading to the nature for a walk with my girlfriend.)

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday December 14 2017 10:34:56 AEDT AM
  
Hi guys,

I have made several coil models and finished the coil simulation calculations.
It will take some time to show them in a nice Excel sheet.
(Not today. The weather here is nice and I'm heading to the nature for a walk with my girlfriend.)



Hi Aziz, great to see you back!
Thanks for sharing your knowledge.

May I suggest if you have anything remotely commercially viable, that you you team up with someone who could take your idea to market.
Don't give a leg up to existing companies by sharing too much online.
There is a fine line between giving information freely and doing yourself out of a possible income, no-one should begrudge you that.
Throwing ideas out and discussing on a forum is how we all learn and can interact with others who are interested in the same thing but its an unfortunate fact that trolls monitor most forums and pick out ideas, nothing wrong with it except they don't acknowledge the author.
If you are not worried about commercial entities using your ideas, then no problems but you have had some great ideas in the past and it would be a shame if you did not benefit from at least one of them!


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday December 14 2017 16:47:25 AEDT PM
Hi Aziz have your coil simulation calculations shown a good size receiver coil for a 14 inch TX coil yet ?


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday December 14 2017 18:07:32 AEDT PM
  
Hi all,

has anyone one of the new elite coils for ML GP/SD/GPX series detectors?

I am particularly referring to the 18 inch elite variant:
See here:
http://www.coiltek.com.au/coils/elite/18-elite/

Is anyone willing to do some measurements for me? I have to know, whether the coil makers already use the separate TX/RX coil technology. I just want to know, whether there is a large TX coil and a smaller RX coil inside coil housing.



The measurements on the coil plug pins:
TX part:
1. Inductance between pin 4 and 5
2. DC resistance between pin 4 and 5

RX part:
3. Inductance between pin 1 and 2
4. DC resistance between pin 1 and 2

5. DC resistance between pin 2 and 4:
either short circuit (zero ohms) or high impedance (not measureable resistance) or some resistance.

I have to know these values. These simple measurements will answer my question.
Thanks in advance. Any other new coil measuerement would do it either. It must be the new ones however.

Cheers,
Aziz

Hi Aziz, Yes I have the 18" Elite and a couple of Evo coils I will do the measurements for you over the week end as I am pre disposed tomorrow.

Regards, Ian.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 14 2017 18:26:20 AEDT PM
  
Hi Aziz, Yes I have the 18" Elite and a couple of Evo coils I will do the measurements for you over the week end as I am pre disposed tomorrow.

Regards, Ian.

Super Ian, I'm looking for the measurements results.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 14 2017 18:56:54 AEDT PM
  
Hi Aziz have your coil simulation calculations shown a good size receiver coil for a 14 inch TX coil yet ?

Hi 6666,

I haven't looked at the naked data yet. It is relative.
The smaller the RX coil size in relation to the TX coil size, the less EMI and ground noise will be picked up by the RX coil and the more gain you would require to compensate for the losses.

There are two option considerations for the gain compensation:
- compensation for the same amount of EMI noise induction
- compensation for the same amount of ground noise induction
same amount means comparable to a specific mono coil size.

I think the latter one is most important (ground noise). Think of the following situation. You have a 14 " mono coil and the ground is heavy mineralized so you have to setup up the detectors gain down to operate on this ground. But you want a greater depth. So a 18"+ TX and 14" RX coil configuration becomes interesting. The RX coil will pick up the same amount of EMI noise (size and inductance has not been changed). But the larger 18"+ TX coil will produce less ground noise induction on the 14" RX coil. The 14" inch RX can have more gain now. This gain compensation will give us the depth improvement. If you don't increase gain, you will have less ground noise (detector runs quieter). You have to choose: either more detection depth or more quiet with some detection depth loss.
The interesting question is, is there enough head room for improvements.
Answer: Yes!
Huch much? To be shown soon.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 14 2017 19:12:06 AEDT PM
Hi guys,

some comments to my last post.

The detection depth improvement is one aspect only. Not the most important one however.

The most improvements come from other effects.
The RX coil focusses to almost perpendicular magnetic fields penetrating the hot ground. Shallow and horizontal affected ground noise won't be picked up by the RX. BTW, these magnetic fields are causing the most ground noises.

A distinct, clear and sharp detection signal for deep targets. You can hear the big deep gold signal better. No more fake signals for the big deep gold.

These are the most important benefits. You will find more gold with it. Forget the depth improvement. It is relative. But you get it too.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 14 2017 19:33:04 AEDT PM
  

...
If you are not worried about commercial entities using your ideas, then no problems but you have had some great ideas in the past and it would be a shame if you did not benefit from at least one of them!

Cheers
Muntari

Hi Muntari,

great to see you again.

I'm not worried about the exploitation of my ideas by others. But they must not be patented!
(BTW, someone in Oz owes me a free cold beer only!)

-->> "Free science, knowledge and inventions to the mankind."
I want more gold for you all.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Thursday December 14 2017 19:38:22 AEDT PM
  
Hi guys,

some comments to my last post.

The detection depth improvement is one aspect only. Not the most important one however.

The most improvements come from other effects.
The RX coil focusses to almost perpendicular magnetic fields penetrating the hot ground. Shallow and horizontal affected ground noise won't be picked up by the RX. BTW, these magnetic fields are causing the most ground noises.

A distinct, clear and sharp detection signal for deep targets. You can hear the big deep gold signal better. No more fake signals for the big deep gold.

These are the most important benefits. You will find more gold with it. Forget the depth improvement. It is relative. But you get it too.

Aziz

You're 100% right there Aziz.
It's always been the ground minerals noise masking the Gold signals.
There is an area that I detect that masks gold that is only 3-6 inches deep. And another area that I cannot detect at all because of these ground minerals and or magnetic fields.

Looking forward to seeing you achieve this.
It's a pity that you don't live in Australia.




Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 14 2017 20:15:22 AEDT PM
  

You're 100% right there Aziz.
It's always been the ground minerals noise masking the Gold signals.
There is an area that I detect that masks gold that is only 3-6 inches deep. And another area that I cannot detect at all because of these ground minerals and or magnetic fields.

Looking forward to seeing you achieve this.
It's a pity that you don't live in Australia.


Hi Digger,

yes, there is still lots of gold in the ground. I will open up the gold fields again. With the separate TX/RX coil design. It is the only way to do it. And it is familiar with the ground loop principle.
More detection depth can be achieved with more TX coil current in conjunction with the RX gain compensation. But we are limitted to RX gain compensation at the moment (what the detector allows for gain compensation or with more RX coil windings in the coil).

Aziz


Title: Re: The need for big deep gold detectors.
Post by: authere on Thursday December 14 2017 23:04:57 AEDT PM
Hi Aziz,

I measured my 18" Elite mono coil for you, saved you some work Ian, and it measured as a mono coil would with .45ohms and 280uH , it doesn't have a second coil

Cheers,Ron


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 15 2017 17:15:02 AEDT PM
  
Hi Aziz,

I measured my 18" Elite mono coil for you, saved you some work Ian, and it measured as a mono coil would with .45ohms and 280uH , it doesn't have a second coil

Cheers,Ron

Thanks Ron,

but I want to see each measured values by myself.
I also need the inductance between pin 2 and 4 (measurement #6).

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 15 2017 17:48:55 AEDT PM
Hi all,

the Excel table is getting large and the coil simulation results will take more time. Publishing date will be very likely next week. I have less free time during the week end.

But don't be disappointed by the naked values comparisons. The separate TX/RX coil will get you more gold, where the equivalent sized mono coil fails its operation. It simply increases the signal-to-noise (SNR) ratio for the big deep gold on heavy mineralized grounds.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 15 2017 19:12:21 AEDT PM
  
BW has tried using a higher voltages on the QED but they did not result in any improvement  in detection depth.All they achieved was a larger battery drain.
doug

I remembered this statement in this thread.

The reason why it hasn't probably worked is because, more power causes more ground noise.

The detection depth will be improved by the separate (large) TX/ (smaller) RX coil design and the larger battery drain won't be wasted power.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 16 2017 07:53:44 AEDT AM
Hi guys,

you won't believe me. ::406::
This will be a major breakthrough in coil technology and electronic gold prospecting.
I will open up all the gold fields again.
But you will hate me for digging deep holes. ::620::

I have to figure out the ground noise response reduction factor for the separate TX/RX coils. A good calculated approximation would be also ok.
But we can also measure them easily for correct factors. By simply building the coils and making some measurements above the hot ground.

BTW, I have found another benefit. The moving coil problem on hot ground reduces also. This will reduce more ground noise of course.
What's a moving coil problem?
The hot ground gets magnetized below the TX coil. If you move the coil during the sampling time (usually done by sweeping the coil), you induce a voltage in the RX coil. The smaller RX coil will see small magnetic field changes by the movement. Compared to the larger TX when used as RX, will induce a much larger ground response of course (big magnetic field change).
::62::

We are changing tomorrows PI technology right now!

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Saturday December 16 2017 13:38:57 AEDT PM
  
Hi guys,

you won't believe me. ::406::
This will be a major breakthrough in coil technology and electronic gold prospecting.
I will open up all the gold fields again.
But you will hate me for digging deep holes. ::620::

I have to figure out the ground noise response reduction factor for the separate TX/RX coils. A good calculated approximation would be also ok.
But we can also measure them easily for correct factors. By simply building the coils and making some measurements above the hot ground.

BTW, I have found another benefit. The moving coil problem on hot ground reduces also. This will reduce more ground noise of course.
What's a moving coil problem?
The hot ground gets magnetized below the TX coil. If you move the coil during the sampling time (usually done by sweeping the coil), you induce a voltage in the RX coil. The smaller RX coil will see small magnetic field changes by the movement. Compared to the larger TX when used as RX, will induce a much larger ground response of course (big magnetic field change).
::62::

We are changing tomorrows PI technology right now!

Cheers,
Aziz

That's great news Aziz.

Now, all you need to do is build them and send me a test coil.

Or you can come and live in Australia and do this here with IB GOLD and Bugwhiskers.  ::10 ::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 16 2017 22:17:55 AEDT PM
Hi all,

a new detector, which is specially designed for the new concentric co-planar large TX/small RX coil design will benefit much more.
A two channel PI detector, which is processing both coils (large TX and small RX) in the off-time. A kind of discrimination of a shallow buried target or deep target can be made.
During the TX coil switch-off phase and constant high voltage limitting the TX coil voltage, the RX coil can sense the coil coupling factor k, which is a grade of mineralization level under the coils, which then can be used for ground balance (GB) to minimize the target signal loss during the GB.
Of course, the information during TX-on phase can be exploited in the RX coil too.

I see a lot of benefits.

And it seems, that I have a long-term PI project on TX/RX coils soon.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday December 17 2017 00:28:20 AEDT AM
Hi all,

this is the road map for the very interesting project:

1. Understanding the principle

2. Coil comparison charts based on coil simulation results

3. Realising the technology on the QED detector (without any modifications)
3.1 Designing a coil with the wire you wind the coil (using my coil software)
3.2 Designing & building the coil adapter box
3.3 Field test

4. Realising the technology on the current SD/GP/GPX detectors  (without any modifications)
4.1 Designing a coil with the wire you wind the coil (using my coil software)
4.2 Designing & building  the coil adapter box
4.3 Field test

5. Future detector designs & ideas


This thread is becoming a large thread. You will find nowhere else the leading edge of coil technolgy.
You may rise questions and objections any time. It's welcome.
I also would need your contribution by supporting me with infos, measurements and tests.
If this isn't going to happen, I will cut-off my contribution. It's your choice. Fair enough?

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Sunday December 17 2017 00:59:05 AEDT AM
  
Hi all,

this is the road map for the very interesting project:

1. Understanding the principle

2. Coil comparison charts based on coil simulation results

3. Realising the technology on the QED detector (without any modifications)
3.1 Designing a coil with the wire you wind the coil (using my coil software)
3.2 Designing & building the coil adapter box
3.3 Field test

4. Realising the technology on the current SD/GP/GPX detectors  (without any modifications)
4.1 Designing a coil with the wire you wind the coil (using my coil software)
4.2 Designing & building  the coil adapter box
4.3 Field test

5. Future detector designs & ideas


This thread is becoming a large thread. You will find nowhere else the leading edge of coil technolgy.
You may rise questions and objections any time. It's welcome.
I also would need your contribution by supporting me with infos, measurements and tests.
If this isn't going to happen, I will cut-off my contribution. It's your choice. Fair enough?

Cheers,
Aziz

Hi Aziz,
I'm no tech wiz so I cannot contribute to this coil idea.
As much as I'd like to.

Maybe IB GOLD (Ian)  can make this coil for me to test?  ::62::


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Sunday December 17 2017 07:57:12 AEDT AM
Hi Aziz

What proportion of TX/RX coil diameter you suggest for starting tests?


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday December 17 2017 10:56:34 AEDT AM
  
Hi Aziz

What proportion of TX/RX coil diameter you suggest for starting tests?

Hi WM6,

this is dependent on the gain margin (max. sensitivity setting) of the detector and the grade of mineralization of the ground you want to operate.
RX/TX diameter relation between 0.7 to 0.4. The smaller the RX, the more gain is required. We are limitted to the maximum gain setting of the detector.

--------

BTW guys,

the custom TX/RX coil should work on the QED, SD/GP/GPX detectors, when we strictly meet the coil specifications tightly to
TX: 300 µH, 0.4 Ohm
RX: 300 µH, 0.4 Ohm

The RX coil could also have more inductance but it's resistance should always be 0.4 Ohms. Basket weave winding technique should keep the coil capacitance low but the wire thickness will make the coils more heavy.

We are just simulating a mono coil, putting damping resistors on the RX coil side but wiring the coil plug to be a DD coil. The detector (SD/GP/GPX) must be configured as a mono coil operation. No switch in the coil adapter box required then. Only the damping resitors for the RX coil.

This should work with less problems in the first instance.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Sunday December 17 2017 16:19:26 AEDT PM
Hi Aziz info as requested,

                                                                               Coil Parameters.  

                                                                                          12"Evolution coil.          14 x 9 elliptical Evo. coil.       18" Elite coil.

TX Inductance pins 4-5.                                                                326 uh.                           314 uh.                         296 uh.

TX Resistance in Ohms. pins 4-5                                                     0.4.                                   0.4.                             0.45.  

RX Inductance pins 1-2                                                                326 uh.                            314 uh.                           296 uh.

RX resistance in Ohms pins 1-2                                                       0.4.                                   0.4.                             0.45.

Inductance pins 2-4                                                                       ----                                    ---                                ---

Resistance pins 2-4                                                                         0.                                       0.                                 0.

S.R.F                                                                                           510.05 KHz                      511.23 KHz                      517.02 KHz
    
Winding.                                                                All Spiral Flat Wound MONO Coils with pins 2-3-4 Bridged in coil plug.      


Regards, Ian.  

                        


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday December 17 2017 20:32:55 AEDT PM
Hi Ian,

thank you very much for the infos, you have nicely presented here.

Nobody has obviously used the separate TX/RX coil design in the new coils yet.
::62::

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: authere on Sunday December 17 2017 22:38:01 AEDT PM
Hi Aziz,

Just like I said

Cheers,Ron


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 18 2017 04:07:55 AEDT AM
  
Hi Aziz,

Just like I said

Cheers,Ron

Hi Ron,

this is not the point. We see the exact coil data and their variation now. 
I always want exact data. ::419::
Cheers,
Aziz

PS:
Be prepared for giving me the coil wire specifications for the custom made TX/RX coil, when we are going to design a coil.
Total wire diameter in mm (core + insulation)
Core wire diameter in mm (copper)
Wire resistance in Ohm/km (or Ohm/m)


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday December 18 2017 16:28:47 AEDT PM
Hi Aziz,

Its a pity you weren't back online a few months ago, I threw all my MPI project gear away, would have been perfect for you coil project.....
see "blast from the past " post from me ...

Cheers

muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 18 2017 19:44:00 AEDT PM
  
Hi Aziz,

Its a pity you weren't back online a few months ago, I threw all my MPI project gear away, would have been perfect for you coil project.....
see "blast from the past " post from me ...

Cheers

muntari

Hi Muntari,

that's really a pitty. Maybe its time for a new and better one?
I recommend a very KISS version.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 18 2017 19:52:55 AEDT PM
Hi guys,

what a fu... mess? ::406::
My PC water cooling system failed yesterday. The iron cool water tank (approx. 15 liter) corroded and got a hole and all the water drained down from the desk to the ground. Fortunatelly, nothing except the water tank has been damaged so far.

It well might delay this project few days. I have to clean the mess.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 18 2017 21:19:18 AEDT PM
Hi all,

I have to calculate the estimated ground response relation of TX/RX for all coil models yet. I'll take a coil height of approx. 1 inch (coil windings to hot ground level). The heigher the coil above the ground, the more erroneous will be the calculated ground response however. But it gives a good estimation in the first instance.

Purpose:
For the comparison of the coils. For instance a comparison between a pure mono coil and a TX/RX coil with same size. Smaller RX coil will pick up less ground noise of course. So we can increase the RX gain to the same level of the ground noise response of the equivalent sized mono coil. Then we can directly compare the detection depth and whether there is an advantage.

How I do this:
By the relation of magnetic flux at the ground level seen by the TX and RX coil. The magnetic flux is direct proportional to the magnetization of the ground layer and therefore to the ground noise response. We don't have to calculate the absolute ground noise reponses (really not a trivial task) and the relation is good enough for this purpose.

see https://en.wikipedia.org/wiki/Magnetic_flux

This will also take some calculation time.
A real ground response relation measurement would be fine of course as it would deliver the correct relation factors. We can make these measurements later if really needed.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Monday December 18 2017 22:23:01 AEDT PM
most of the time I drag my coils on the ground
you were lucky with your tank  leak.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 18 2017 22:29:37 AEDT PM
Hi all,

some comments about what I have found the last days reading the gold prospecting forums.

Most of the (GPX) users have to damp the RX gain down to 7 in extreme hot ground conditions in conjunction with relative large mono coils. With the new TX/RX coils, you don't have to reduce the RX gain anymore. You rise it up to the appropriate working ground conditions. So we would have enough RX gain margin (upto 20 RX gain) for this TX/RX coil to compensate the losses and to get to the very comfort region of depth increase advantage.

Now imagine the effects:
All your old SD/GP/GPX detectors are becoming a GPZ-Killer on very hot ground conditions, where usually gold is being found!
::620::
Provided, that the black box (SD/GP/GPX detector) runs with the new coils of course.
The QED will run. No doubt.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 18 2017 22:34:44 AEDT PM
  
you were lucky with your tank  leak.

Indeed, I was very very lucky.
I have taken a new plastic bucket containing cooling water (10 l). This solution shouldn't delay this project in the first instance.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: authere on Monday December 18 2017 23:17:54 AEDT PM
Hi Aziz,

If I run cooling water into my computer it would let the smoke out ::406::, you must have a wangdoozie of a computer, are you still using valves ::402::

Ron


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday December 18 2017 23:30:53 AEDT PM
  
Hi Aziz,

If I run cooling water into my computer it would let the smoke out ::406::, you must have a wangdoozie of a computer, are you still using valves ::402::

Ron

Hi Ron,

I have built a special CPU water cooling system with a large cooling water tank, which was placed outside of the computer on a desk. It is a passive cooling system and I don't need a radiator. Only the iron water tank has been corroded and got a leak hole. No water came into the computer or main board.
I'm using the heated water tank as a heater during the night. No energy will be wasted.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Tuesday December 19 2017 00:07:53 AEDT AM
  
Hi all,

some comments about what I have found the last days reading the gold prospecting forums.

Most of the (GPX) users have to damp the RX gain down to 7 in extreme hot ground conditions in conjunction with relative large mono coils. With the new TX/RX coils, you don't have to reduce the RX gain anymore. You rise it up to the appropriate working ground conditions. So we would have enough RX gain margin (upto 20 RX gain) for this TX/RX coil to compensate the losses and to get to the very comfort region of depth increase advantage.

Now imagine the effects:
All your old SD/GP/GPX detectors are becoming a GPZ-Killer on very hot ground conditions, where usually gold is being found!
::620::
Provided, that the black box (SD/GP/GPX detector) runs with the new coils of course.
The QED will run. No doubt.

Cheers,
Aziz

Hi Aziz,
Sharp timing and sensitive extra timings on the gpx 5000 will punch deeper into the ground but the problem with these two timings is that it works on mild ground but most gold is trapped in hot mineralized ground.
I have used max RX (20) and max stabiliser (20) on my gpx 5000
But it takes great concentration as the noise is incredibly very noisy and very hard on the ears and head.
Your head starts spinning after a little while.  ::406::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 19 2017 00:39:16 AEDT AM
  
Hi Aziz,
Sharp timing and sensitive extra timings on the gpx 5000 will punch deeper into the ground but the problem with these two timings is that it works on mild ground but most gold is trapped in hot mineralized ground.
I have used max RX (20) and max stabiliser (20) on my gpx 5000
But it takes great concentration as the noise is incredibly very noisy and very hard on the ears and head.
Your head starts spinning after a little while.  ::406::

Hi Digger,

all the issues will be improved with the new TX/RX coils.
And there will be no limit to the total coil size.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 19 2017 05:50:07 AEDT AM
Hi all.

The plot thickens. ::406::

You definitely won't be disappointed about the new concentric co-planar TX/RX coils.
::62::

I also want to make a horizontal coil sweep simulation comparison. Only for two coils to see the major benefit for locating the big deep gold on heavy mineralized ground.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: sd220d Digger on Tuesday December 19 2017 09:50:12 AEDT AM
  
  
Hi Aziz,
Sharp timing and sensitive extra timings on the gpx 5000 will punch deeper into the ground but the problem with these two timings is that it works on mild ground but most gold is trapped in hot mineralized ground.
I have used max RX (20) and max stabiliser (20) on my gpx 5000
But it takes great concentration as the noise is incredibly very noisy and very hard on the ears and head.
Your head starts spinning after a little while.  ::406::

Hi Digger,

all the issues will be improved with the new TX/RX coils.
And there will be no limit to the total coil size.

Aziz

Hi Aziz,
Who will you have making these coils for us? ::419::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 19 2017 09:56:31 AEDT AM
Hi all,

I have a good name for the new coils.
Analogy:
We have got the Evolution coils.

This time the Revolution coils.
::620::
(It's a pefect name. It will revolutionise the gold detecting.)

Oh man!, can we get a RX gain margin in the region of +6 dB (2 times) to +10 dB (3 times) out of the detector setting?
That would be really perfect!
Well, if the amplifier noise is becoming critical or when there isn't enough RX gain headroom, then we have to increase the RX coil inductance a bit. Not too much as we don't want much more coil weight and RX coil capacitance.

An RX gain on the detector setting to dB table would be really fine. I could exactly say you, how the coils will perform.
I see a trial & error development coming up.

Anyway.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 19 2017 10:01:13 AEDT AM
  
Hi Aziz,
Who will you have making these coils for us? ::419::

Hi Digger,

we are making these coils by ourselves in the first instance.
I hope, Coiltek and Nuggetfinder or other coil maker companies will follow us and produce such coils.
(Where the hell are the coil spies? Ring up your boss immediately! It will pay off!!!!$$$$$$$$$$$$$)

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 19 2017 10:26:24 AEDT AM
Let's make some assumptions.

The GPX-5000 has a RX Gain setting level from 1 to 20. The gain could be well linearly divided.
If a RX gain of 7-10 is the working limit on extremely hot ground with large mono coils, then we could have a gain rise of 2 times (+6 dB), when we crank up the RX gain up to 20. So this situation might work.

We also could design the RX coils to 600 µH inductance (that's sqrt(600/300)=1.41 times more loop turn count for the RX coil windings compared to a 300 µH RX coil).
We would be in the safe region (1.41*2 = 2.82 times).
This could really work.

sqrt(800µH/300µH) = 1.63 and the rest by RX gain setting.

Yeah, we have to increase the RX coil inductance somehow.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: egixe4 on Tuesday December 19 2017 11:46:50 AEDT AM
  
Hi Ian,

thank you very much for the infos, you have nicely presented here.

Nobody has obviously used the separate TX/RX coil design in the new coils yet.
::62::

Cheers,
Aziz

What about the GPZ coil?
Is it not a separate TX/RX coil??



Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 19 2017 19:15:55 AEDT PM
  
What about the GPZ coil?
Is it not a separate TX/RX coil??

Hi egixe4,

we want to kill the totally overpriced GPZ. So it doesn't make sense to upgrade the GPZ.
::620::

Well, I don't know anything about the GPZ internals, coil plug, the id chip in the coil (is there any?), etc.

One surely could make the principle working on a GPZ. The TX coil has not such a damping resistors due to bipolar constant current pulsing. The separate RX coil would reqire a damping resistor however.

The GPZ has not implemented the concentric co-planar separate TX/RX coil design. They have only the Super-D coil. 14" and 19" I think.

But the old detectors will run even with extra large coils very smooth and quiet. And they will punch deeeeeeeeeeeeeeeeeeeeeeeep into the extremely mineralized ground.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 19 2017 19:47:31 AEDT PM
Hi all,

I don't think, there is much RX gain margin in the detector settings. We also have to reduce the amplifier noise contribution a bit. It is critical.
So we must increase the RX coil gain by increasing the number of RX coil loop turns (inductance).

QED: RX coil wire must be thick. The total RX coil DC resistance should be 0.4 Ohm. The coil is getting heavy.
It is possible to use thin wire for the RX coil to reduce the coil weight. But the QED box requires impedance matching adjustment for such coils. And won't work for the other coils anymore.

SD/GP/GPX: RX coil wire can be thin. The total DC resistance should be below 5 Ohm.

And the RX coil capacitance should be low on both solutions. The self-resonant-frequency (SRF) should be approx. be at 500 kHz.or above.
Basket weave winding techniqe should meet the desired specification but requiers more winding space. But it is getting critical for small coils due to lack of free winding space. No problem with the big coils, there is enough space.

I have to add high inductance RX coils into the coil simulation comparison. This will take some time.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 19 2017 22:19:38 AEDT PM
Ok guys,

there is no other way. We must use thin RX coil wire and a basket weave winding technique to lower the RX coil capacitance.
The SD/GP/GPX detectors will cope with the high impedance RX coils.

But the QED requires a matching network in the coil adapter box for a specific RX coil impedance (lets say 5 Ohm for the RX coil).
Yes, we can make it work for the QED but these coils can't be used on the SD/GP/GPX detectors then.
****!

Aziz


Title: Re: The need for big deep gold detectors.
Post by: autitch on Tuesday December 19 2017 22:32:42 AEDT PM
Just a thought.  Could someone please measure  the TX & RX inductance & resistance for a Minelab 11" or 18" DD coil.  I  remember  reading some time ago  that the RX inductance was much more than the TX figure but i can't  remember the numbers.  

Azia, I've been following  this  thread  with great  interest from my limited understanding what you are  suggesting is really  a  reconfigured DD coil. As a starting point, to suit  a Minelab GPX the "Revolution" coil Tx RX inductance should more closely match a Minelab DD coil figures.

Furthermore would there be any benefit  in a coil with 16"TX & 10.5"RX or is this concept  better suited to bigger coils?

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday December 19 2017 23:16:40 AEDT PM
  
Just a thought.  Could someone please measure  the TX & RX inductance & resistance for a Minelab 11" or 18" DD coil.  I  remember  reading some time ago  that the RX inductance was much more than the TX figure but i can't  remember the numbers.  

Azia, I've been following  this  thread  with great  interest from my limited understanding what you are  suggesting is really  a  reconfigured DD coil. As a starting point, to suit  a Minelab GPX the "Revolution" coil Tx RX inductance should more closely match a Minelab DD coil figures.

Furthermore would there be any benefit  in a coil with 16"TX & 10.5"RX or is this concept  better suited to bigger coils?

AuTitch

Hi AuTitch,

yes, a great idea getting some real figures for some ML DD coils.
I remember 450 µH and 5-15 Ohms for the RX coil.
But I would be very happy, when someone does some measurements like Ian previously did.

Yes, I am suggesting quasi a reconfigured DD coil but it is a concentric co-planar separate (large) TX / (small) RX with the RX coil damping resistors in the small coil adapter box.

"As a starting point, to suit  a Minelab GPX the "Revolution" coil Tx RX inductance should more closely match a Minelab DD coil figures."
Yes, we would get less problems. But the RX coil isn't much critical and we can compensate for some RX gain as the detector wouldn't allow much gain margin I think. The TX coil part should strictly meet the specifications: 300 µH, 0.4 Ohm. But that's not critical at all.

Furthermore would there be any benefit  in a coil with 16"TX & 10.5"RX or is this concept  better suited to bigger coils?
Yes, there is a benefit. This concept is not restricted to a special coil size. It works with any coil size. There are only practical limitations on small coils (winding space, coil capacitance, coil resistance, etc).

The revolutionary benefit is, that the most of the (shallow) ground noise will be bypassed outside the RX coil. And we have less EMI noise too. So we can increase the RX gain and get to the depth advantage region. For the big deep gold on extremely mineralized ground! We also have a better pin-pointing feature. Clear detection signals. And so on.

The new coil could cause a new gold rush on the gold fields.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 20 2017 02:32:12 AEDT AM
BTW guys,

we are also breaking the limits of the coil size.
You can use coils as large as you can operate with.
No more EMI noise.
Less ground noise.
Going super duper deep.
Operates also on hottest grounds.
Sensitivity to small targets does not decrease compared to the equivalent sized mono coil.
Super pin-pointing feature.

It's really a revolution.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 20 2017 11:33:40 AEDT AM
Hi all,

the Excel table is growing and growing...

BTW, I have to search the internet for pros & cons using large mono coils and I want to make a visual demonstration, how the new coil will shine over the traditional large mono loop coils. A situation, where the mono loop coil simply fails operation and how to get more detection depth.

A large coil is useless, when you can't operate it or have to decrease the RX gain setting for proper operation.

Oh man!, I'm tired... Cheers.. Aziz


Title: Re: The need for big deep gold detectors.
Post by: deemon on Wednesday December 20 2017 12:29:56 AEDT PM
  
Hi all,

I don't think, there is much RX gain margin in the detector settings. We also have to reduce the amplifier noise contribution a bit. It is critical.
So we must increase the RX coil gain by increasing the number of RX coil loop turns (inductance).

QED: RX coil wire must be thick. The total RX coil DC resistance should be 0.4 Ohm. The coil is getting heavy.
It is possible to use thin wire for the RX coil to reduce the coil weight. But the QED box requires impedance matching adjustment for such coils. And won't work for the other coils anymore.

SD/GP/GPX: RX coil wire can be thin. The total DC resistance should be below 5 Ohm.

And the RX coil capacitance should be low on both solutions. The self-resonant-frequency (SRF) should be approx. be at 500 kHz.or above.
Basket weave winding techniqe should meet the desired specification but requiers more winding space. But it is getting critical for small coils due to lack of free winding space. No problem with the big coils, there is enough space.

I have to add high inductance RX coils into the coil simulation comparison. This will take some time.

Aziz

Hi Aziz !

Your coil idea looks interesting , but the RX ringing problem might be hard to solve ... Don't you think about shorted RX coil and a current signal pickup instead of voltage ? As you remember , I used this solution in my first recuperative PI and later in the square-wave approach and never had a problem ... so you can try it in your device as well .


Title: Re: The need for big deep gold detectors.
Post by: egixe4 on Wednesday December 20 2017 14:15:02 AEDT PM
  
  
What about the GPZ coil?
Is it not a separate TX/RX coil??

Hi egixe4,

we want to kill the totally overpriced GPZ. So it doesn't make sense to upgrade the GPZ.
::620::

Well, I don't know anything about the GPZ internals, coil plug, the id chip in the coil (is there any?), etc.

One surely could make the principle working on a GPZ. The TX coil has not such a damping resistors due to bipolar constant current pulsing. The separate RX coil would reqire a damping resistor however.

The GPZ has not implemented the concentric co-planar separate TX/RX coil design. They have only the Super-D coil. 14" and 19" I think.

But the old detectors will run even with extra large coils very smooth and quiet. And they will punch deeeeeeeeeeeeeeeeeeeeeeeep into the extremely mineralized ground.

Cheers,
Aziz

Hi Aziz,

I'm not suggesting making or upgrading coils for the GPZ
Simply replying to your statement made earlier
“Nobody has obviously used the separate TX/RX coil design in the new coils yet”

The Standard 14” GPZ coil is indeed a Separate TX/RX design Coil
Here is a picture of it for you.



Title: Re: The need for big deep gold detectors.
Post by: GARY on Wednesday December 20 2017 15:12:55 AEDT PM
I wonder how much the depth potential of the DOD type round coil is governed by the length and width dimensions of its TX winding?

In the CC type round coil then its TX winding is much larger in dimension since it is around the circumference of the coil.

I had thought the dimension of the TX winding aids more towards outright depth?


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday December 20 2017 16:34:00 AEDT PM
Hi Aziz ,

You are correct with your inductance and resistances for the DD coils and they also do have a damping resistor on the RX I tested the concentric with the RX damping resistor on the QED and I do not believe they are compatible ( poor performance ) will try it on a Minelab and report back.

Regards, Ian. ::62:: now it works.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 20 2017 20:29:58 AEDT PM
  

Hi Aziz,

I'm not suggesting making or upgrading coils for the GPZ
Simply replying to your statement made earlier
“Nobody has obviously used the separate TX/RX coil design in the new coils yet”

The Standard 14” GPZ coil is indeed a Separate TX/RX design Coil
Here is a picture of it for you.


Hi egixe4,

indeed, the GPZ coil has a separate TX/RX coil.
But they are in a more or less induction balanced arrangement and are not concentric co-planar design.

My bad in naming the new coil.

concentric coil: can be everything
concentric co-planar coil: can be everything
concentric co-planar TX/RX coil: better
concentric co-planar separate TX/RX coil: much better

Anyone with a better name?

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 20 2017 20:33:39 AEDT PM
  
Hi Aziz !

Your coil idea looks interesting , but the RX ringing problem might be hard to solve ... Don't you think about shorted RX coil and a current signal pickup instead of voltage ? As you remember , I used this solution in my first recuperative PI and later in the square-wave approach and never had a problem ... so you can try it in your device as well .

Hi deemon,

we don't want to change or modify the existing detectors.
We only want to change the coil design.

Taming the ringing between TX and RX coil is not a big deal.
When properly damped, there won't be any ringing.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 20 2017 20:51:52 AEDT PM
  
Hi Aziz ,

You are correct with your inductance and resistances for the DD coils and they also do have a damping resistor on the RX I tested the concentric with the RX damping resistor on the QED and I do not believe they are compatible ( poor performance ) will try it on a Minelab and report back.

Regards, Ian. ::62:: now it works.

Hi Ian,

regarding the ML DD coil: is the RX damping resistor placed in the coil or coil plug housing or is it placed in the ML detector box?

It would be nice, if you could measure some DD coils for us. We would see the variance of the coil parameters. Would you be so kind and do some DD coil measurements for us?

Regarding the new coil: Please wait until I have presented the coil simulation results. I'm almost finished.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 20 2017 21:06:21 AEDT PM
  
I wonder how much the depth potential of the DOD type round coil is governed by the length and width dimensions of its TX winding?

In the CC type round coil then its TX winding is much larger in dimension since it is around the circumference of the coil.

I had thought the dimension of the TX winding aids more towards outright depth?

Hi Gary,

a good approximation for an 
equivalent mono loop round coil diameter = sqrt(length*width),
where length and width are the dimensions of the TX coil.

DOD coil design is not optimal for big deep gold on highly mineralized ground. You are dealing with high ground response too.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 20 2017 22:07:52 AEDT PM
Hi guys,

I have to draw some magnetic field sketches yet, what is happening in the highly mineralized ground with the magnetic fields penetrating the hot ground. You will see then the real benefit of the coil design. Simple air tests won't show the benefit of the coil design. Only tests on the real hot ground will reveal the real benefits. Unfortunately, my coil software does not support the simulation of magnetic fields in hot ground so I have to draw some sketches for you and they will take some time of course.

Following facts on hot ground:
- Magnetic fields get refracted when penetrating a hot ground. The more, the higher the ground mineralization.
- The steeper the magnetic fields, the less refraction is there. 90 degree magnetic fields won't be refracted at all.
- Most ground noise is caused nearby the edge of the TX coil (nearby the TX coil windings). The magnetic fields are very strong there. The Magnetic fields are very much refracted and they finally go almost horizontal in the ground layer and hence causing shallow affected ground noise.
- This large shallow affected ground noise is mostly bypassed around the RX coil and won't be detected in the RX coil. The RX coil is focussing to the steep (deep) penetrating magnetic fields.

I hope, I can show you this in a sketch.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 21 2017 01:02:36 AEDT AM
I think, I'll write a PDF document to explain the principle.
All info will be compact and I can embed graphics, tables and so on.
But you have to wait longer for the results.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday December 21 2017 08:27:01 AEDT AM
  
I think, I'll write a PDF document to explain the principle.
All info will be compact and I can embed graphics, tables and so on.
But you have to wait longer for the results.
Aziz

Sounds good Aziz.


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday December 21 2017 13:48:36 AEDT PM
  
Hi Aziz info as requested,

                                                                               Coil Parameters.  

                                                                                          12"Evolution coil.          14 x 9 elliptical Evo. coil.       18" Elite coil.

TX Inductance pins 4-5.                                                                326 uh.                           314 uh.                         296 uh.

TX Resistance in Ohms. pins 4-5                                                     0.4.                                   0.4.                             0.45.  

RX Inductance pins 1-2                                                                326 uh.                            314 uh.                           296 uh.

RX resistance in Ohms pins 1-2                                                       0.4.                                   0.4.                             0.45.

Inductance pins 2-4                                                                       ----                                    ---                                ---

Resistance pins 2-4                                                                         0.                                       0.                                 0.

S.R.F                                                                                           510.05 KHz                      511.23 KHz                      517.02 KHz
    
Winding.                                                                All Spiral Flat Wound MONO Coils with pins 2-3-4 Bridged in coil plug.      


Regards, Ian.  

                        

Hi Ian
just wondering what used to measure the I, and what settings
thanks


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday December 21 2017 16:34:57 AEDT PM
Hi Aziz,

I will do it for you over the week end I have some already done just need the SRF done.

6666, Inductance done and checked with my 3 LCR meters.

Regards, Ian.


Title: Re: The need for big deep gold detectors.
Post by: autitch on Thursday December 21 2017 17:25:50 AEDT PM
  
Hi Aziz,

I will do it for you over the week end I have some already done just need the SRF done.

6666, Inductance done and checked with my 3 LCR meters.

Regards, Ian.

Hi IBGOLD

I was wondering how do you measure the  SRF of the  coil or do you calculate it.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 21 2017 19:33:01 AEDT PM
Hi guys,

I have been thinking about the ground response relation calculation and I have found a much more precise estimation this time.


Assuming the coils as a simple transformer. (Oh man!, I must be really blind!)
I have the coil coupling factor k of the coils and their inductances L. The rest is easy. One can even make a spice simulation and can read the estimation values.
According to the new ground noise relation factors, we can even rise the RX gain much more and get to the very comfort zone of depth advantage.

Unfortunately, everything delays a bit more. It is too much work.

Cheers,
Aziz
PS:
Ground response relation = Ground response of the larger coil / Ground response of the smaller coil in concentric co-planar arrangement.
It simply tells, how much times a bigger coil pick ups ground noise than a smaller coil.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 21 2017 19:39:35 AEDT PM
  
Hi Aziz,

I will do it for you over the week end I have some already done just need the SRF done.

Regards, Ian.

Hi Ian,

that is really fine. I'm looking forward to your measurements.
Thanks very much.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 21 2017 20:20:21 AEDT PM
Hi all,

oh man!, there is a relative huge depth advantage possible. Provided that we can manage a high RX gain compensation (3 to 10 times!!!).
We must use as much RX coil inductance as possible. This is only limitted by the  RX coil capacitance, winding space and coil weight.

We will revolutionise the gold detecting.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 21 2017 23:42:36 AEDT PM
Well,

I found a much better way of estimating the ground noise response relation factor for coils being above the ground.
This should give us much more accurate coefficients. Then we hopefully can see, what is really possible.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 00:31:36 AEDT AM
  
Hi all,

oh man!, there is a relative huge depth advantage possible. Provided that we can manage a high RX gain compensation (3 to 10 times!!!).
We must use as much RX coil inductance as possible. This is only limitted by the  RX coil capacitance, winding space and coil weight.

We will revolutionise the gold detecting.
Aziz

What a calculation mess! These coefficients were wrong.
The simple transformer principle did not work for the ground noise response relation coefficients.

I get now the same old coefficients with different estimation approach (Magnetic flux and voltage induction approach). So they must be correct now.
All the "fictive" depth advantage is gone!

The worst case will be, that the TX/RX coil design will approach to the same size TX mono coil performance. But we know, that we will have other major advantages here, which will dominate at the end.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 00:56:45 AEDT AM
Hi all,

A coil comparison between a 18" mono loop round coil (as reference) and different TX/RX variations of the same size (TX = 18").
RX coil is being compensated (amplified) for equivalent ground noise induction as the 18" mono loop round coil.

All TX coils inductance = 300 µH
All RX coils inductance = 300 µH

12" RX: Gain = 1.86
9" RX: Gain = 2.82
6" RX: Gain = 4.70

The worst case is happening. No free lunch for us. (see graphics below)

The smaller RX coils require more winding space for a specific inductance (300 µH), so they need more windings, which give a better performance compared to the mono coil. Note, that a mono coil (reference) has less response at the center of the coil but more response nearby the coil edge. So ignore the first few target response inches in the comparison. The target response has been made for the center axis only.

But the TX/RX coil design will shine over highly mineralized grounds with better pin-pointing option and for searching big deep gold. This is the major advantage, which I can not show in the comparisons.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 01:08:48 AEDT AM
BTW,

another advantage I forgot to mention in the last post:
Where big mono coils fail practically its operation on severe ground and EMI noise conditions, the TX/RX coil design overcomes these problems with ease. So you still have a big advantage here.

As the shallow (flysh1t) gold is mostly picked up by by the current detectors, you can focus for the big deep gold now. This new coil will enhance the signals for big deep gold.

It makes fully sense to develop further this new coil.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 01:15:07 AEDT AM
And we are going to cheat a bit with coil winding technique to enhance the overall coil performance. So you get more at the end.

A new detector, which drives the TX with more current would give you the ultimate depth advantage of course. But we can not do it for the existing detectors in the first instance.

Oh well, I'm going to build a special detector prototype, which will do it for me. So don't pick up the large deep (3+ ft) slugs please!
::62::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: deemon on Friday December 22 2017 03:49:28 AEDT AM
  

What a calculation mess! These coefficients were wrong.
The simple transformer principle did not work for the ground noise response relation coefficients.

I get now the same old coefficients with different estimation approach (Magnetic flux and voltage induction approach). So they must be correct now.
All the "fictive" depth advantage is gone!

The worst case will be, that the TX/RX coil design will approach to the same size TX mono coil performance. But we know, that we will have other major advantages here, which will dominate at the end.

Cheers,
Aziz

Once upon a time , Aziz , I had placed on Geotech forum the simple but convincing proof of one fact - if you wanna have a strongest target signal on a fixed diameter coil and on a fixed distance , you must use a mono coil ... so your latest result isn't a mistery for me  ::419:: In other words we can say that even the most sophisticated construction in the world cannot beat the simple coil in terms of target signal  ::419:: And this is why I use a mono coil in all my projects , even in a balanced approach .

But your idea , being a kind of "portable ground loop" , might have another potential benefit - an ability of some "ground noise" reduction , especially in a situation with a highly mineralized ground - sometimes it can be better to sacrifice a portion of a target signal in order to suppress much stronger and annoying ground noise , thus increasing overall signal-to-noise performance ... and what I think now - that I really can add this thing to my square wave project as an additional "information channel" . You see , if I can balance a mono-coil with my electronic auto-balance circuitry , remowing all TX signal completely - so I can add a special concentric RX coil with less diameter ( electrically shorted in order to reject this ringing issue ) , with another auto-balance chain - and get more info about the overall situation , I mean target , ground , etc . Anyhow , it seems to be more and more interesting ...  ::419::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 05:56:47 AEDT AM
  

Once upon a time , Aziz , I had placed on Geotech forum the simple but convincing proof of one fact - if you wanna have a strongest target signal on a fixed diameter coil and on a fixed distance , you must use a mono coil ... so your latest result isn't a mistery for me  ::419:: In other words we can say that even the most sophisticated construction in the world cannot beat the simple coil in terms of target signal  ::419:: And this is why I use a mono coil in all my projects , even in a balanced approach .

But your idea , being a kind of "portable ground loop" , might have another potential benefit - an ability of some "ground noise" reduction , especially in a situation with a highly mineralized ground - sometimes it can be better to sacrifice a portion of a target signal in order to suppress much stronger and annoying ground noise , thus increasing overall signal-to-noise performance ... and what I think now - that I really can add this thing to my square wave project as an additional "information channel" . You see , if I can balance a mono-coil with my electronic auto-balance circuitry , remowing all TX signal completely - so I can add a special concentric RX coil with less diameter ( electrically shorted in order to reject this ringing issue ) , with another auto-balance chain - and get more info about the overall situation , I mean target , ground , etc . Anyhow , it seems to be more and more interesting ...  ::419::

Hi deemon,

it is great for me to inspire you.

Indeed, the TX/RX coil design has more inherent benefits, which I can't show in my coil simulations at the moment.
But cheating allows us to get a few more inches of detection depth increase by simultaneously inceasing the detection depth for deep targets and improved pin-pointing ability. This will allow us to outperform a simple mono coil.
::62::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday December 22 2017 10:26:56 AEDT AM
  
Hi Aziz,

I will do it for you over the week end I have some already done just need the SRF done.

6666, Inductance done and checked with my 3 LCR meters.

Regards, Ian.

Thanks Ian, I have a couple of different LCR meters, which give different results on coils, do you have any other nugget finder monos that we could compare readings  , thats if you would not mind doing so ?


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday December 22 2017 10:31:57 AEDT AM
Thanks for the graph Aziz, so which is the correct way to read your graph
which is the better coil ratio maybe the 6" RX coil ? do we have to shield the TX coil ?
I will have to buy a family size pizza for the bigger box so I can wind a 18" coil :)
Doug the smilys still dont work

12" RX: Gain = 1.86
9" RX: Gain = 2.82
6" RX: Gain = 4.70


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday December 22 2017 12:08:14 AEDT PM
  
BTW,

another advantage I forgot to mention in the last post:
Where big mono coils fail practically its operation on severe ground and EMI noise conditions, the TX/RX coil design overcomes these problems with ease. So you still have a big advantage here.

As the shallow (flysh1t) gold is mostly picked up by by the current detectors, you can focus for the big deep gold now. This new coil will enhance the signals for big deep gold.

It makes fully sense to develop further this new coil.

Aziz

Hi Aziz,

A gradiometer as in like what Corbyn and the MPI used, in my opinion, is the best way to go but there is a trade off both in weight , TX power and they are impractical for use on a standard detector format. Most people would not like to haul around a 400mm wide x 300mm high coil lol.
A separate TX RX co planar coil is the next best thing.... in my opinion.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Doug on Friday December 22 2017 12:41:15 AEDT PM
  
Doug the smilys still dont work



They are working for me now. ::62::
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Doug on Friday December 22 2017 12:51:06 AEDT PM
  


Hi Aziz,

A gradiometer as in like what Corbyn and the MPI used, in my opinion, is the best way to go but there is a trade off both in weight , TX power and they are impractical for use on a standard detector format. Most people would not like to haul around a 400mm wide x 300mm high coil lol.

Cheers

Muntari


You could of course use a wheeled trolley coil like Corbyn used.
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday December 22 2017 14:37:49 AEDT PM
Hmmmmm not for me I use fire fox


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 20:06:33 AEDT PM
Hi guys,

note, that the gain compensation factors for the RX coil gain might be wrong or inaccurate. The used values are estimations. The real world conditions could be better or worser. I don't no, until we make real measurements on hot ground conditions.

The TX/RX coil will run better compared to an equivalent size mono loop coil. You will find no other coil running better on severe ground conditions and detecting gold.

Here is an another comparison example:
Basket weave on TX and RX compared to a mono loop coil (bundle windings).
RX gain compensation reduces to 1.33 as it has 80 loop turns (thinner coil wire). RX inductance is approx. 1200 µH.
TX = 300 µH

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 20:08:51 AEDT PM
second pic


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 20:20:41 AEDT PM
  
Thanks for the graph Aziz, so which is the correct way to read your graph
which is the better coil ratio maybe the 6" RX coil ? do we have to shield the TX coil ?
I will have to buy a family size pizza for the bigger box so I can wind a 18" coil :)
Doug the smilys still dont work

12" RX: Gain = 1.86
9" RX: Gain = 2.82
6" RX: Gain = 4.70

Hi 6666,

there isn't any optimum coil diameter ratio.
The smaller the RX coil, the more you have to amplify (compensate) the RX signal.
And you end in practical limitations:
- amplifier noise increases
- not enough space for RX coil windings

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 21:15:18 AEDT PM
  
Hi Aziz,

A gradiometer as in like what Corbyn and the MPI used, in my opinion, is the best way to go but there is a trade off both in weight , TX power and they are impractical for use on a standard detector format. Most people would not like to haul around a 400mm wide x 300mm high coil lol.
A separate TX RX co planar coil is the next best thing.... in my opinion.

Cheers

Muntari

Hi Muntari,

yes, there isn't any other best practical coil besides the TX/RX coil.

I think, the TX/RX coil will show its dominant advantage on severe ground conditions, where an equivalent sized mono loop coil can't be operated well.
Severe ground (very hot ground mineralization) tends to shield (block) the magnetic fields. Except in the center region of the coil so they penerate deeper into the ground. And here we go. We are just focussing to the deep penetrating magnetic fields and bypassing all the large shallow ground noise contribution.

This coil will get you more gold. More big deep gold.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 21:37:24 AEDT PM
Hi guys,

let's continue the development of the TX/RX coil design. There is lots of work to do yet.
And we can cheat alot by giving more space to the (RX) coil windings.

The non-believers keep swinging their old coils.
The believers will be rewarded at the end. No doubt.
::62::

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 22 2017 22:58:28 AEDT PM
Hi all,

as I have not much time during the xmas holidays, here is a compressed rar file containing the Excel table in the attachment.
You can play around with it if you like.
It's a preliminary comparison. The development continues.

With the free antenna software 4nec2 (see internet), you can download the coils (all *.NEC files) and display them on the screen how they wound and their geometry.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Saturday December 23 2017 07:02:45 AEDT AM
Hi Aziz thanks for the file, I have been winding some small scale  test coils, with scrap wire,  I've cut up some pizza boxes and figured out a simple former , for flat spiral wind RX and a stacked (2 layers x15 turns) TX, and flat plate shield.

The scrap wire is .8mm  outside diameter, pvc covered,
starting with a small almost  flat spiral RX coil, (basket weave) with a inside hole of 90mm, I ran out of wire after 27 turns giving about 470uH, 170MM outside dia,  so to get to 80 turns and  1200uH, is going to take a lot of THIN wire.

For the RX, I had planned to use #25 AWG muti strand tinned copper , pvc covered wire for the RX, but that is going to be too thick I think. So may end up with #30 awg single strand  for RX.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 23 2017 08:55:33 AEDT AM
  
Hi Aziz thanks for the file, I have been winding some small scale  test coils, with scrap wire,  I've cut up some pizza boxes and figured out a simple former , for flat spiral wind RX and a stacked (2 layers x15 turns) TX, and flat plate shield.

The scrap wire is .8mm  outside diameter, pvc covered,
starting with a small almost  flat spiral RX coil, (basket weave) with a inside hole of 90mm, I ran out of wire after 27 turns giving about 470uH, 170MM outside dia,  so to get to 80 turns and  1200uH, is going to take a lot of THIN wire.

For the RX, I had planned to use #25 AWG muti strand tinned copper , pvc covered wire for the RX, but that is going to be too thick I think. So may end up with #30 awg single strand  for RX.

Hi 6666,

you're welcome.

But you are way too early in winding a coil (except for training of course ::419::).
A large inductance for the RX coil is very critical for proper operation with GPX detectors for instance.

This is the problem:
Self resonant frequency (SRF) of the coil
SRF = 1 / (2*pi*sqrt(L*C)), where
L = coils inductance
C = coils parasitic capacitance

We have to keep the specified coils SRF same. This is around 500 kHz. With a 300 µH inductance, we get for C approx. 330 pF.
If we increase the inductance L, we inherently increase the coils parasitic capacitance C. There are more windings, which make more capacitance of course. But to keep the SRF same, we must ensure to keep the product L*C same. So if we make L four times (1200 µH), we have to reduce C four times (to 82.5 pF).
So we need ultra fast coils for the RX winding.

What happens, if we can not reduce the coils capacitance?
The RX coil will get slow and add a few µs damping delay. And this could cause timing problems in the detector.

We must figure out yet, what we can make (maximum practical RX coil inductance). So the Double-D coil measurements from Ian will give us some more details.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday December 24 2017 00:21:07 AEDT AM
Hi all,

some notes on coil capacitance:

The coil capacitance is composed of coil wire length + interwire capacitance between each loops.
The first one is direct proportional to the core wire thickness. The thicker the coil wire, the more capacitance is there.
And we have the insulation of the coil wire (dielectric constant), creating more coil capacitance.

With appropriate winding technique, the interwire coil capacitance can be reduced much. For instance with the basket weave winding technique, where each individual winding loop has more distance to the other windings.

And we have to increase the RX coil inductance a bit to compensate for the RX gain. So we have to go for an appropriate thin litz teflon wire using the basket weave winding technique. Or even a naked (very thin silk insulation or no insulation at all) litz wire. We must not fall below the specified SRF. But we can exceed it with no problems. But then, in investing more RX winding loops would be the better choice in this case.

So please wait before you start winding coils. You will waste expensive coil wire or time and effort. Until you have understood the principle, one can make a lot of mistakes, which will end in a total disappointment.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday December 24 2017 20:23:47 AEDT PM
Hi all,

I have two good ideas more,  when the TX/RX coil is becoming difficult to realise.
::62::
Merry xmas to all.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday December 24 2017 23:03:25 AEDT PM
Hi all,

the very simple to realise idea is on the other topic:
http://australianelectronicgoldprospectingforum.com/detector-coils/ground-noise-reduction-coil-idea/msg43954/?topicseen#msg43954

The other idea is going to the direction of concentric co-planar IB coil (not new!) for PI detectors, but the induction balance is a quasi induction balance (thus not perfect IB) to make things easy for us. The main purpose is to reduce a great amount of ground noise so we get into the depth increase region much easier this time.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday December 27 2017 15:34:11 AEDT PM
  
Hi Aziz,

I will do it for you over the week end I have some already done just need the SRF done.

6666, Inductance done and checked with my 3 LCR meters.

Regards, Ian.

OK Aziz,  I re measured some DD coils for you as below but still have to do the SRF sorry I forgot I have family here so I will do the SRF measurements over the weekend after delivering family home.

Regards, Ian.

                                                                 DD Coil Measurements.

                                                               Minelab 11"DD GPX coil.                Coiltek 430 x 280 DD Pro.      SEF   21" x 17" DD.

  TX  pins 5-4 Inductance  =                              294 uh.                                             249 uh.                              293 uh.
          "   "  " Resistance   =                               0.4 ohms.                                         0.5 ohms.                          0.46 ohms.

RX  pins 1-2  Inductance  =                               368 uh.                                             524 uh.                              416 uh.
        "    " "   Resistance  +                                17.1 ohms.                                        7.2 ohms.                          8.21 ohms.

Inductance between pins 2-4.                             590 uh.                                             775 uh.                              712 uh.
Resistance between   "    "  "                              17.5 ohms.                                        7.7 ohms.                           8.5 ohms.

Remembering pins 1-5 are shorted in the coil plug.
Pins 3-4 are shorted in the coil plug.
SRF's to come.
Hope that helps Aziz .

Regards, Ian.     ( no smileys here)


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday December 27 2017 19:45:40 AEDT PM
Thank you very much Ian.
We get the real infos for our coil project, which I will evolve when we get the missing SRF data.
::62::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 28 2017 03:47:19 AEDT AM
BTW guys,

be prepared to tell me, what kind of coil wire you are going to use for the first prototype. I will design a coil just for the designated coil wires. So we can tightly match the coil specifications.

TX coil wire specifications:
Core wire diameter in mm
Wire diameter in mm (core+insulation)
Resistance in Ohms per km

RX coil wire specifications (should be a thin wire of course):
Core wire diameter in mm
Wire diameter in mm (core+insulation)
Resistance in Ohms per km

When you are using Litz wire, we need the specified resistance per km wire length as the wire consists of multiple enamelled strands. Resistance of single strand wire (like the enamelled magnet wire) can be calculated of course. But I need the full info about the coil wires.

I will only accept suggestions from persons skilled in the art. Sorry, but we don't need amateurs right now.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Thursday December 28 2017 14:37:57 AEDT PM
Aziz,

recently I am building extra lite coils out of so called ECCA (Enameled Copper Clad Aluminum) wire.

Mostly multiple wire braided together (2x, 3x, 4x) to lower DC resistance.

Have in stock two diameter of ECCA wire, 0.25mm and 0.50mm.

Probably drawback for your conception is higher ECCA wire resistance in comparison to Cul wire?

If it could still suit with your front end design, I can provide more specific data.



 


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday December 28 2017 16:01:18 AEDT PM
Hi Aziz I have updated the list.
                                                                   DD Coil Measurements.

                                                               Minelab 11"DD GPX coil.                Coiltek 430 x 280 DD Pro.      SEF   21" x 17" DD.

  TX  pins 5-4 Inductance  =                              294 uh.                                             249 uh.                              293 uh.
          "   "  " Resistance   =                               0.4 ohms.                                         0.5 ohms.                          0.46 ohms.

RX  pins 1-2  Inductance  =                               368 uh.                                             524 uh.                              416 uh.
        "    " "   Resistance  +                                17.1 ohms.                                        7.2 ohms.                          8.21 ohms.

Inductance between pins 2-4.                             590 uh.                                             775 uh.                              712 uh.
Resistance between   "    "  "                              17.5 ohms.                                        7.7 ohms.                           8.5 ohms.

SRF  TX                                                            492 kHz                                            509 kHz                               356 kHz
SRF  RX                                                            496 kHz                                            570 kHz                               356 kHz

Remembering pins 1-5 are shorted in the coil plug.
Pins 3-4 are shorted in the coil plug.

Two additions but only inductance's and resistances as I do not now have the coils and this is all I logged.

11" SD series DD  TX inductance 314 uh resistance .4 ohms. RX inductance 402 uh resistance 14.4 ohms.

11" GP series DD  TX inductance 304 uh resistance .4 ohms. RX inductance 348 uh resistance 14.6 ohms.

Regards, Ian. ::62:: with smileys.



Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 28 2017 20:07:41 AEDT PM
Hi Ian,

thank you very much for the lots work you kindly have done. The RX coil side varies to much and is obviously not as critical as I thought first. This is good. ML DD coils do not have a perfect induction balance, as there is some considerable mutual inductance between TX and RX coil.

I'll put the infos into an Excel table and do some calculations on it.

Cheers und Danke,
 ::62::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 28 2017 20:18:07 AEDT PM
  
Aziz,

recently I am building extra lite coils out of so called ECCA (Enameled Copper Clad Aluminum) wire.

Mostly multiple wire braided together (2x, 3x, 4x) to lower DC resistance.

Have in stock two diameter of ECCA wire, 0.25mm and 0.50mm.

Probably drawback for your conception is higher ECCA wire resistance in comparison to Cul wire?

If it could still suit with your front end design, I can provide more specific data.


Hi WM6,

these wires are hard to get and probably expensive.

The coil weight is not much critical for the prototype.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday December 28 2017 20:55:16 AEDT PM
Hi all,

lets negotiate about the coil size and used wires (TX, RX) for the first coil prototype.
Any suggestions?
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 29 2017 00:06:49 AEDT AM
Hi all,

you know now, what the real reason was of getting all the coil measurement infos.
You will find the Excel table in the rar attachment file.

I'll continue the coil project and there is so much to do yet.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 29 2017 10:11:14 AEDT AM
Hi all,

this is, how the new TX/RX coil is configured for the SD/GP/GPX detector operation. Note, that the detector has to be configured for mono coil and we do the RX coil damping in the small coil adapter box. The TX damping is done inside the detector as usual.
When we unintentionally make an ultrafast TX coil (happens with basket weave coils), we have to slow down it by connecting a capacitor to the TX coil (Cx). So the SRF of the TX coil should be around 500 kHz at the end.

Below is the LTspice file (zipped rar) for your convenience.

The QED needs RX coil voltage biasing in the coil adapter box in conjunction with high impedance RX coils. I will show you how to do it anytime.

 ::419::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Friday December 29 2017 11:07:28 AEDT AM
Have been following with interest thus far .. very interesting Aziz .
I opened up an old DD coil some time back . The rx windings are of thinner wire than the much thicker Tx .. both are litz wire.
Rx is approx 25 - 30 turns  and is approx 7.5 inch dia.  There is also a 680 ohm damper in parallel across this Rx coil .
keep up the good work
For info



Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 29 2017 17:23:32 AEDT PM
  
Have been following with interest thus far .. very interesting Aziz .
I opened up an old DD coil some time back . The rx windings are of thinner wire than the much thicker Tx .. both are litz wire.
Rx is approx 25 - 30 turns  and is approx 7.5 inch dia.  There is also a 680 ohm damper in parallel across this Rx coil .
keep up the good work
For info

Hi gef12,

that's interesting. The info is unfortunately irrelevant until you tell the brand name of the coil.
SD/GP/GPX compatible coil?

The RX coil must be damped somewhere. Either in the coil housing/coil plug housing or in the detector.

But how did Ian measure the SRF of the RX coil, when there is a damping resistor connected to it?
Just wondering.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Friday December 29 2017 17:45:43 AEDT PM
Aziz. The RX SRF's were measured with the RX damping resistor in situation as it is in the coil but I concur with gef12 680 ohms is the usual RX damping resistor in Minelab coils.

I will give you the the specifications for my prototype concentric coil tomorrow as I am now home for a while and can play if I build anymore coils I will have to source some more wire as I have run out.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 29 2017 18:09:59 AEDT PM
  
Aziz. The RX SRF's were measured with the RX damping resistor in situation as it is in the coil but I concur with gef12 680 ohms is the usual RX damping resistor in Minelab coils.

I will give you the the specifications for my prototype concentric coil tomorrow as I am now home for a while and can play if I build anymore coils I will have to source some more wire as I have run out.

Regards, Ian. ::62::

Hi Ian,

ok, I didn't know this info regarding the RX damping resistor. So the RX damping resistor is placed inside the coil housing.
Ok, in this case, the detector may also be switched to DD coil configuration. But not Chancel mode of course.

I can assist you in making/designing the coil. I would need the total coil diameter size and the coil wire specifications (both for RX and TX coil).
In the first instance, it is better to start with a bigger RX coil (RX/TX coil size relation of around 0.7) so we can compansate the RX gain with higher RX coil inductance and we would have more RX winding space to lower the interwire coil capacitance. The critical thing is the RX coil capacitance and whether we can achieve the minimum specified SRF (approx. 500 kHz).
The next thing is to look, whether there is enough gain margin in the detector settings (Sensitivity/Rx gain setting) to compensate the missing RX gain loss.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 29 2017 18:48:37 AEDT PM
Hi guys,

ok, there is some info regarding the RX coil damping resistor:
http://www.findmall.com/read.php?34,137344

The info for me is consistent now.
 ::05::

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday December 29 2017 19:50:23 AEDT PM
Hi guys,

the next very critical part is all the parasitic capacitances, which add to the RX coil capacitance.
Coil shielding:
Use a thicker distance spacer (3+ mm) to the RX coil windings and a graphite coated paper with a thin tinned drain wire taped onto it. The round graphite coated paper must be cut and isolated so it does not form a circular current path.

Big big issue: RX coil cable!
You can't use 50 Ohm impedance antenna coax cables. They have approx. 100 pF/m capacitance. We would add 300 pF for 3 m coil cable and that would be too much.
The next best thing is to use 75 Ohm impedance antenna coax cables. They have approx. 67 pF/m. Still too much how ever.

There are coax cables available with less pF/m. I have seen a 55 pF/m cable. Would be ok I think.

To reduce further RX cable capacitance, one just could make it out of cables with 2 insulated strands and thicker insulation over the strands. A graphite coated paper strip wrapped around the cable, a tinned thin drain wire onto it and insulated with adhesive tape.

We have to reduce the RX coil capacitance as much as possible to be able to use higher RX coil inductances to compensate for the RX gain.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Saturday December 30 2017 12:03:09 AEDT PM
  
  
Have been following with interest thus far .. very interesting Aziz .
I opened up an old DD coil some time back . The rx windings are of thinner wire than the much thicker Tx .. both are litz wire.
Rx is approx 25 - 30 turns  and is approx 7.5 inch dia.  There is also a 680 ohm damper in parallel across this Rx coil .
keep up the good work
For info

Hi gef12,

that's interesting. The info is unfortunately irrelevant until you tell the brand name of the coil.
SD/GP/GPX compatible coil?

The RX coil must be damped somewhere. Either in the coil housing/coil plug housing or in the detector.

But how did Ian measure the SRF of the RX coil, when there is a damping resistor connected to it?
Just wondering.

Cheers,
Aziz

Hi Aziz .. the coil is standard 11 inch Minelab DD coil ..  several years old .. but think they would be same as current standard ..


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Saturday December 30 2017 12:38:30 AEDT PM
I have a 20inch spoked mono .. surely could just add Rx coil on top of this and send the coax to your box into or with separate plug ..
just different modus operandi .. in this instance should the both coils share same sheild link wire ...
your thoughts


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 30 2017 17:47:58 AEDT PM
  
I have a 20inch spoked mono .. surely could just add Rx coil on top of this and send the coax to your box into or with separate plug ..
just different modus operandi .. in this instance should the both coils share same sheild link wire ...
your thoughts

Hi gef12,

you want to upgrade your 20 inch mono coil.  ::419::
Sure, why not! It is possible of course.
The TX coil part is not critical.
The RX coil is the most critical part however. We need a lot of loop turns for it to get enough RX gain compensation. Standard bundle winding would fail due to forming a much higher RX coil interwire capacitance. You have to use the basket weave winding technique.
At the end, the RX coil should have at least the minimum specified SRF (approx. 500 kHz) taking all parasitic capacitances (coil, coil shielding, coil cable) into account. The damping of the RX coil is dependent on RX coils inductance and total parasitic capacitances. So you can't use a simple 680 Ohm resistor here.

If you can not achieve some RX gain compensation, you will get a quiet detector with reduced detection depth.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 30 2017 18:13:35 AEDT PM
Hi gef12,

I forgot to add:

You can switch between MONO and Double-D mode and will have both benefits of the coils.
 ::05::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 30 2017 19:16:58 AEDT PM
Hi all,

there is a mistake in the last schematics diagram:

The detector must be operated in the Double-D mode of course!

Since I know, where the damping of the RX coil happens, there shouldn't be any impact. But the detector switches between two input signal sources (TX and RX).

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 30 2017 19:30:04 AEDT PM
Hi all,

I think it is a very good idea made by gef12 just to upgrade the existing large mono coil in the first instance.
We only have to focus to the RX coil winding, its shielding and cabling, making the coil adapter box and the final coil plug for the detector.

We could test the final coil much earlier and it is also fairly easy to do.
I like the idea!
 ::05::

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Blacksand on Saturday December 30 2017 20:32:15 AEDT PM
Hi all,

Hope your all enjoying the holidays.

As the Tx/Rx coil is for a p.i. circuit, is it necessary to have it a good mechanical null (with an oscilloscope) like a VLF coil. I have read that a bucking coil needs to be added to the RX and have found photo's on the net of opened minelab dd commander coils showing a looped wire, probably in series with the Tx coil and placed on the Rx side of the coil.

Regards

Martin


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 30 2017 20:55:41 AEDT PM
  
Hi all,

Hope your all enjoying the holidays.

As the Tx/Rx coil is for a p.i. circuit, is it necessary to have it a good mechanical null (with an oscilloscope) like a VLF coil. I have read that a bucking coil needs to be added to the RX and have found photo's on the net of opened minelab dd commander coils showing a looped wire, probably in series with the Tx coil and placed on the Rx side of the coil.

Regards

Martin

Hi Martin,

thanks for the pics. Yes, I can see the RX damping resistor inside the coil.  ::419::

But we don't use VLF coils or VLF detectors. Just SD/GP/GPX/QED PI detectors. So there is absolutely no need for a (perfect/any) induction balance as the RX coil is beeing processed in the off-time period only. We have to take care, that the RX coil is not becoming a target and hence causing a target signal. The time constant of the RX coil is below 1 µs. And it doesn't carry current (only parasitic currents) and merely inducing a voltage. That's the reason, why the RX coil wire can be very thin (for lower coil capacitance and coil weight).

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 30 2017 21:05:46 AEDT PM
Hi Martin,

there is no bucking coil in SD/GP/GPX coils. The bucking coil is necessary for concentric VLF coils, which need a perfect induction balance. The bucking coil is connect in series with the TX coil with opposite winding direction to the TX coil.

We have much easier coils for PI detectors.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Blacksand on Saturday December 30 2017 21:52:30 AEDT PM
Hi Aziz

Thanks for your reply, thought I do some research before I make any attempt at building my own concentric coil. Hope to start making the jig after New Year, but still deciding whether to make it multi wound or spider basket weave. Will have to use enamel copper wire as I'm stocked with it, 17awg for Tx and 28awg for receive and got a full can of nickel conductive paint for shielding. Few months back I had replaced the graphite shielding from my Coiltek 11" mono elite with nickel conductive paint and works well. Quite shocked how poorly the graphite shielding paper was glued on (hot glue gun) onto the foam base.

Cheers

Martin


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 30 2017 22:53:33 AEDT PM
BTW guys,

in exchanging the TX/RX coil sizes, thus an existing (small/mid size) mono coil with a larger RX coil, the ground noise will be greatly reduced too. But we would induce more EMI noise. On the other side, we would not have the problems with the RX gain compensation and low capacitance RX coils.
There is a benefit in appropriate conditions:
- in extremely hot ground mineralization conditions
- for larger ground coverage
- in low EMI conditions

Make the coil adapter box flexible, so you can plug in different add-on coils (RX coil + skid plate combo) to your existing mono coils.

Two pin RX coil socket (in the coil adapter box as first input)
Five pin coil socket for the mono coil (in the coil adapter box as second input)
From coil adapter box a short coil cable with a 5 pin coil plug as output.

That's it. You are perfectly prepared for different coil configurations.

I'll do a coil simulation and compare it's performance soon.
 ::05::
I'm curious.  ::10 :: Let's see, what happens.
 ::62::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday December 30 2017 23:08:16 AEDT PM
  
Hi Aziz

Thanks for your reply, thought I do some research before I make any attempt at building my own concentric coil. Hope to start making the jig after New Year, but still deciding whether to make it multi wound or spider basket weave. Will have to use enamel copper wire as I'm stocked with it, 17awg for Tx and 28awg for receive and got a full can of nickel conductive paint for shielding. Few months back I had replaced the graphite shielding from my Coiltek 11" mono elite with nickel conductive paint and works well. Quite shocked how poorly the graphite shielding paper was glued on (hot glue gun) onto the foam base.

Cheers

Martin

Hi Martin,

the shielding coating need not to be low conductive. So the graphite coat will do it well without causing target like signals.
Concentric VLF IB coil is really difficult to build. I wouldn't recommend it. A simple DD coil is much simpler to realise.

But we are focussing to the PI coils here.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Sunday December 31 2017 16:06:00 AEDT PM
Hi Aziz,

My prototype using the GG concentric I made a few years ago specifications are as follows TX coil is 400 mm center line made with 100/36 AWG Litz wire 17.5 turns with bucking coil 4.375 turns inductance 280 uh resistance .3 ohms the RX is 200 mm center line made with 8/46 Litz wire  38 turns with inductance of 819 uh and resistance of 6.34 ohms and it is pretty close to induction balanced other than that I will have to start from scratch.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Monday January 1 2018 13:56:07 AEDT PM
  
Hi Aziz,

My prototype using the GG concentric I made a few years ago specifications are as follows TX coil is 400 mm center line made with 100/36 AWG Litz wire 17.5 turns with bucking coil 4.375 turns inductance 280 uh resistance .3 ohms the RX is 200 mm center line made with 8/46 Litz wire  38 turns with inductance of 819 uh and resistance of 6.34 ohms and it is pretty close to induction balanced other than that I will have to start from scratch.

Regards, Ian. ::62::

Hi Ian what was the smallest nugget that coil could detect ? thanks.


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Monday January 1 2018 15:33:33 AEDT PM
6666, I have no idea it was originally built for a project that was never finished so I have just modified it to try on this project I have only bench tested it on the QED but it is not suited when I fix the SD2000M of my sons mate I have on the bench that is dead I will try it on that.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Alex on Monday January 1 2018 16:21:45 AEDT PM
Hi Aziz . I'm new to this and been following along trying to learn .My question is . Is a very fine copper wire wrap shielding type not suitable for this type of coil and why. thanks


Title: Re: The need for big deep gold detectors.
Post by: Doug on Tuesday January 2 2018 14:39:54 AEDT PM
 Interestingly this topic has been read over 1950 times so far so it shows that their is a lot of interest in the topic.
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 2 2018 19:54:33 AEDT PM
  
Hi Aziz . I'm new to this and been following along trying to learn .My question is . Is a very fine copper wire wrap shielding type not suitable for this type of coil and why. thanks

Hi Alex,

the RX coil takes a lot of space for its windings due to larger space between the windings to reduce the coil capacitance and more windings for compansation of the RX gain. We have a large area to shield. Only high impedance shielding like the graphite coating on paper is the most convenient type for such RX coils.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 2 2018 19:58:13 AEDT PM
  
Hi Aziz,

My prototype using the GG concentric I made a few years ago specifications are as follows TX coil is 400 mm center line made with 100/36 AWG Litz wire 17.5 turns with bucking coil 4.375 turns inductance 280 uh resistance .3 ohms the RX is 200 mm center line made with 8/46 Litz wire  38 turns with inductance of 819 uh and resistance of 6.34 ohms and it is pretty close to induction balanced other than that I will have to start from scratch.

Regards, Ian. ::62::

Hi Ian,

leave that GG concentric coil alone. Focus to the basket weaved RX coil and mount it either above or below a standard mono coil. Build a coil adapter plug and you can start testing it with a SD/GP/GPX detector.
This is the easiest way for the first prototype.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 2 2018 20:02:49 AEDT PM
Hi guys,

I have found more convenient low capacitance coax cables for the RX coil cabling:
see http://www.standard-wire.com/coax_cable_theory_and_application.html

RG 24A/U    (125 Ohm cable impedance, 12 pF/ft)
RG 114A/U  (185 Ohm, 6.5 pF/ft)

The more cable impedance, the better for us.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 2 2018 20:23:58 AEDT PM
  
BTW guys,

in exchanging the TX/RX coil sizes, thus an existing (small/mid size) mono coil with a larger RX coil, the ground noise will be greatly reduced too. But we would induce more EMI noise. On the other side, we would not have the problems with the RX gain compensation and low capacitance RX coils.
There is a benefit in appropriate conditions:
- in extremely hot ground mineralization conditions
- for larger ground coverage
- in low EMI conditions

Make the coil adapter box flexible, so you can plug in different add-on coils (RX coil + skid plate combo) to your existing mono coils.

Two pin RX coil socket (in the coil adapter box as first input)
Five pin coil socket for the mono coil (in the coil adapter box as second input)
From coil adapter box a short coil cable with a 5 pin coil plug as output.

That's it. You are perfectly prepared for different coil configurations.

I'll do a coil simulation and compare it's performance soon.
 ::05::
I'm curious.  ::10 :: Let's see, what happens.
 ::62::
Cheers,
Aziz

Hi guys,

the results:
You can also pimp up your (small) monoloop coils used as TX and an add-on bigger RX coil.
The ground noise behaves similar to the larger TX/smaller RX designs. But you will pick up more EMI noise! This is really not a big advantage. So we are pi$$ing off to this design option.

18" RX / 12 " TX: 1.77 times less ground noise compared to a 18 " monoloop coil, 1.58 times more EMI noise for a 300 µH RX coil
18" TX / 12 " RX: 1.86 times less ground noise compared to a 18 " monoloop coil, 1.58 times less EMI noise for a 300 µH RX coil

For big deep gold on extremely mineralized ground the larger TX/smaller RX coil design is the way to go. And you can switch back to the larger MONO coil in the detector.

I'm sure, a new generation of the detector coils will be available soon using this technology.
If not, we are going to make it by ourselves.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Alex on Tuesday January 2 2018 21:32:31 AEDT PM
Aziz .Thanks for your reply.Once again correct me if I am wrong .The coax rg114a/u I think is copper cladded steel centre .Is that not a problem.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 2 2018 21:57:28 AEDT PM
  
Aziz .Thanks for your reply.Once again correct me if I am wrong .The coax rg114a/u I think is copper cladded steel centre .Is that not a problem.

Yes, that's a real problem. Steel is paramagnetic and can cause signals.

Copper core would be fine. If any available. I haven't looked in detail.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Tuesday January 2 2018 22:26:08 AEDT PM
  
Hi guys,

I have found more convenient low capacitance coax cables for the RX coil cabling:
see http://www.standard-wire.com/coax_cable_theory_and_application.html

RG 24A/U    (125 Ohm cable impedance, 12 pF/ft)
RG 114A/U  (185 Ohm, 6.5 pF/ft)

The more cable impedance, the better for us.

Aziz

A source for low capacity high impedance coax can be old car radio antenna coax, while the quality of the cable used for car radios is not always great, its worth checking if you have any laying around the junk box.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 3 2018 12:51:01 AEDT PM
  
  
BTW guys,

For big deep gold on extremely mineralized ground the larger TX/smaller RX coil design is the way to go. And you can switch back to the larger MONO coil in the detector.


Hi Aziz and all, Great thread, thanks for sharing and also to Ian and 6666 for chipping in. It goes to show, that without distraction and good focus (and no trolls) that topics can raise interest in a good way...with good outcomes...

 Aziz, I totally agree with the large TX/smaller RX is the way to go. Solving the SNR problem at the coil starts right there.

Ill start chipping in more soon, just loaded up with work atm.

Keep up the good work

muntari


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Wednesday January 3 2018 20:11:07 AEDT PM
Or if you have an old coil laying around .. just use the cable from this ...  ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 3 2018 20:21:56 AEDT PM
  
Or if you have an old coil laying around .. just use the cable from this ...  ::62::

Or DIY ultra low capacitance RX coil cable. You need only 3 m or so.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 3 2018 23:02:09 AEDT PM
Hi guys,

the separate TX/RX coil takes advantages of two coils:
- large TX coil
overall good depth performance on benign and mild ground conditions

- small RX coil
superior pin-pointing feature with increased detection depth
good depth performance on severe ground conditions

On the GPX detectors, you can switch between large TX and small RX signal sources (just like switching to mono mode with Double-D coils plugged in). Even the cancel mode should work when the winding direction of the RX coil is right.

This is the best combo coil, you can ever have.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: deemon on Wednesday January 3 2018 23:43:55 AEDT PM
  
Hi guys,

I have found more convenient low capacitance coax cables for the RX coil cabling:
see http://www.standard-wire.com/coax_cable_theory_and_application.html

RG 24A/U    (125 Ohm cable impedance, 12 pF/ft)
RG 114A/U  (185 Ohm, 6.5 pF/ft)

The more cable impedance, the better for us.

Aziz

You can also try a special cable used in an oscilloscope probes - this cable has extremely thin internal wire and very low capacitance too .


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 4 2018 00:28:08 AEDT AM
  
  
Hi guys,

I have found more convenient low capacitance coax cables for the RX coil cabling:
see http://www.standard-wire.com/coax_cable_theory_and_application.html

RG 24A/U    (125 Ohm cable impedance, 12 pF/ft)
RG 114A/U  (185 Ohm, 6.5 pF/ft)

The more cable impedance, the better for us.

Aziz

You can also try a special cable used in an oscilloscope probes - this cable has extremely thin internal wire and very low capacitance too .
.   In fact this is a great cable type for low capacitance , I used it on the MPI receive circuits with BNC connectors originally or internal and external connections over about 2 metres. Alas, was not robust enough for field use. Great for internal where there is no flex. Osc probes usually have overmolded end connectors and long tailed strain relief but as Deemon states its low capacitance.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday January 4 2018 15:20:28 AEDT PM
Hi Aziz,

What I am proposing is I have flat wound Mono prototype coil that I received in a package deal that I will use as the TX coil it is 600 mm x 600 mm square center line of coil winding and I will use 8/44 Litz for the RX coil what size do you want me to wind the RX and what kind of basket weave.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday January 4 2018 20:02:51 AEDT PM
  
Hi Aziz,

What I am proposing is I have flat wound Mono prototype coil that I received in a package deal that I will use as the TX coil it is 600 mm x 600 mm square center line of coil winding and I will use 8/44 Litz for the RX coil what size do you want me to wind the RX and what kind of basket weave.

Regards, Ian. ::62::

Hi Ian,

Your coil is too big to test it easy. I for one would use any 14" - 18 " mono loop round coil and would mount the (shielded) RX coil at the top or bottom side of the mono loop coil. A simple coil adapter and here we go! This is the easiest way for a prototype and you have to focus to the RX coil only. You can use your big coil for the next prototype, when we know the RX gain margin of the detector setting and whether we can achieve a low capacitance RX coil with more inductance (up to 1.2 mH).

Remember, the smaller the RX coil (compared to the TX), the more RX gain compensation we need. We are gain compensating it with
a) more loop turns for the RX coil (more RX coil inductance) and
b) setting the detectors RX gain/sensitivity up (we don't know the gain margin here yet and whether it is sufficent enough)

In the example #7 (see the Excel sheet I have provided earlier), an equivalent ground noise compensation factor is 2.41 times for a 300 µH RX coil. That means, we have to amplify the RX signal by 2.41 times. I can't imagine, that the detector will have the required gain margin for the compensation. In the example #9 with more loop turns (80), the RX gain compensation factor reduces to 1.33 times (no wonder, we have made the big part of the gain compesation with more inductance). The 1.33 times gain can be easily compensated by the detector settings (RX gain/sensitivity turning up) now.
We have to try out some RX coils to test it, whether the detector will have enough gain margin and whether we can achieve low capacitance RX coil with higher inductances more than 300 µH. We must achieve at least 500 kHz SRF for the RX coil (including the coil cable, shielding etc.).


I think, the Litz wire for the RX coil will not have enough insulation thickness to keep the RX coil capacitance low. We need more radial spacing between the loop turns. There are several possible ways to wind the RX coil using your thin Litz wire or even simple and cheap thin magnet wire (0.2 - 0.4 mm thickness). Vertical spacing of the windings is trival. But we have to focus to the radial loop turn spacing. A radial loop turn spacing of 1.5 - 3 mm (wire center to wire center distance) should be achieved somehow. Of course, it is dependent of the coil size and whether there is enough space for the windings.

A thin core wire with a thicker insulation would be easy to start with. Winding the RX coil would be very trivial.

I am going to try out some coil winding solutions with the thin Litz wire or magnet wire and will post it here soon.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Thursday January 4 2018 20:42:15 AEDT PM
Thanks Aziz ..also remember that there are other detectors out there other than GPX units .. there are GP and SD ..and modified ones also ..
so should keep in mind ..


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday January 4 2018 21:17:18 AEDT PM
  
Thanks Aziz ..also remember that there are other detectors out there other than GPX units .. there are GP and SD ..and modified ones also ..
so should keep in mind ..

Hi gef12,

yes, you're right. I have checked several detector manuals.
The SD series detectors do not provide the RX coil switch option between MONO, Double-D and Cancel mode. Only the coil type defines whether there is a Monoloop coil or Double-D coil used (configured at the coil plug).

This is not a problem. A simple switch in the coil adapter box can make this for SD series detectors easy for us.
I will show the final coil adapter box schematics anytime later.

The GP and GPX series detectors all provide the coil option switches for us.
The coil plug interface is standardised for all SD/GP/GPX detectors.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 5 2018 05:57:59 AEDT AM
  
Hi Aziz,

What I am proposing is I have flat wound Mono prototype coil that I received in a package deal that I will use as the TX coil it is 600 mm x 600 mm square center line of coil winding and I will use 8/44 Litz for the RX coil what size do you want me to wind the RX and what kind of basket weave.

Regards, Ian. ::62::

Hi Ian,

you can use your flat mono prototype coil of course. But I have to figure out yet, which winding technique is simple and cheap. Then I will give you more detailed infos for the RX coil.

I have bought some materials for different winding techniques to test today.
Wooden staff, cardboards, PVC rods, large & stable 5 mm thick XPS sheets (extruded polystyrene)..

It will take some time however. I still haven't setup my work bench yet.
Anybody with a good idea how to wind the RX coil using a thin and cheap magnet wire is welcome.
::419::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 5 2018 10:55:48 AEDT AM
Hi all,

the 5 mm XPS foam sheet seems to be feasable with thin litz or magnet wire. The smallest distance between two notches I can cut is 1.5 mm. This will make possible a 3 mm wire to wire radial distance and 5 mm vertical distance.
The XPS foam has a very low dielectric constant (a lot of air is in it) and the RX coil will have very low capacitance therefore. And less weight too.

I will show you soon, when I have wound a demonstration coil. I haven't found my magnet wire yet.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Friday January 5 2018 16:21:21 AEDT PM
Hi Aziz,

I will wind a round 3DSS basket weave coil to go with the 24" square mono I will have to source some XPS foam sheet that is what I used before on basket weave coils I will wind a round basket weave coil using .2 enameled wire as I have that and I have layout former for the 3DSS coil what center line diameter should I wind it your call.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 5 2018 22:23:48 AEDT PM
  
Hi Aziz,

I will wind a round 3DSS basket weave coil to go with the 24" square mono I will have to source some XPS foam sheet that is what I used before on basket weave coils I will wind a round basket weave coil using .2 enameled wire as I have that and I have layout former for the 3DSS coil what center line diameter should I wind it your call.

Regards, Ian. ::62::

Hi Ian,

a quick calculation of the DC resistance of the 0.2 enamelled copper wire would exceed the 15 Ohm resistance for the RX coil.
Better would be 0.3 mm and up (up to 0.5 mm not much critical).

You are free in the region of 0.75 to 0.4 RX/TX diameter relation.
Let's take 23" inch diameter estimation for the TX coil bundle due to coil housing.
23" * 0.75 = 17.25 "
23" * 0.4  = 9.2 "

So you can wind the inner coil region starting from diameter 9" to 17". The RX coil dimensions should be somewhere approx. in this region.
Let's take an example:
Wire to wire distance: 3 mm
Loop turns: 60
Ending diameter: 17 "
Beginning diameter: 17" - (3*60/25.4) = 9.9" (approx. 10")
So start winding at approx. 10" diameter

The RX coil DC resistance should not exceed 15 Ohms.
The minimum RX coil inductance should be 600 µH.

And let's see, whether we can achive minimum SRF of 500 kHz. If not, we have to reduce the RX coil inductance or increase the wire to wire spacing.

It's a more or less trial & error method for the first prototypes.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Friday January 5 2018 22:46:06 AEDT PM
  


So you can wind the inner coil region starting from diameter 9" to 17".

Cheers,
Aziz

We can conclude that smaller RX could be better (more exact) in pinpoint purposes.

But which from proposed 9" to 17" RX diameter would perform better regarding depth?


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday January 6 2018 00:23:31 AEDT AM
  
  


So you can wind the inner coil region starting from diameter 9" to 17".

Cheers,
Aziz

We can conclude that smaller RX could be better (more exact) in pinpoint purposes.

But which from proposed 9" to 17" RX diameter would perform better regarding depth?

Hi WM6,

yes and yes.

the smaller the RX, the better the pin-pointing
the smaller the RX, the less ground noise and the more detection depth losses on the RX coil (when RX coil inductance is same as TX coil inductance)
therefore, the more RX gain you need to compensate for detection depth losses

The RX gain compensation is done via
a) more RX coil inductance (more loop turns)
b) detector sensitivity increase
The total RX gain compensation factor is a product of both a) and b)

But there is a limit. You can not make very small RX coils. You can not compensate the RX gain too much (detector sensitivity is limitted, more amplifier noise will be there too, etc.) . We have to meet the coil specifications. So we have to find a good compromise.

The proposed dimension is a good compromise.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Saturday January 6 2018 01:11:55 AEDT AM
Hi Aziz

Regarding RX coil diameter.

How on suitable diameter imply coil Q (quality)?

Somewhere I read that coil under 5cm are under-optimal, due
to high coil self damping.

It is about Brooks coil optimization:

http://www.nessengr.com/techdata/brooks/brooks.html (http://www.nessengr.com/techdata/brooks/brooks.html)

http://nvlpubs.nist.gov/nistpubs/scientificpapers/nbsscientificpaper455vol18p451_a2b.pdf (http://nvlpubs.nist.gov/nistpubs/scientificpapers/nbsscientificpaper455vol18p451_a2b.pdf)


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday January 6 2018 07:52:41 AEDT AM
  
Hi Aziz

Regarding RX coil diameter.

How on suitable diameter imply coil Q (quality)?

Somewhere I read that coil under 5cm are under-optimal, due
to high coil self damping.

It is about Brooks coil optimization:

http://www.nessengr.com/techdata/brooks/brooks.html (http://www.nessengr.com/techdata/brooks/brooks.html)

http://nvlpubs.nist.gov/nistpubs/scientificpapers/nbsscientificpaper455vol18p451_a2b.pdf (http://nvlpubs.nist.gov/nistpubs/scientificpapers/nbsscientificpaper455vol18p451_a2b.pdf)

Hi WM6,

forget Q and what you have read there.
It doesn't apply to our RX coils.

Making basket weave RX coil is a bit difficult for thin wires needing some space between the windings.
Spider coils on XPS coil form seems to work perfect as one can cut notches, where the thin wire put into to avoid movements of the windings.
The RX coil will look like this:
http://makearadio.com/coils/images/992uh-coil.jpg
(round of course)

5 mm is the XPS sheet thickness. On both sides, there will be windings (interleaved). So the XPS coil form is divided into odd number of sectors.

This is looking like the XPS coil form:
http://www.crystalradio.net/crystalsets/hassell/hassell_2.jpg

The XPS sheet I have bought is made for parquet isolation and hence rigid and strong. Perpect for coil form and distance spacer for the shieldings on both sides of the coil.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Saturday January 6 2018 16:07:38 AEDT PM
OK Aziz,

 I will go with your form and be using 5/38 Litz I estimate the resistance to be somewhere around 10 ohms Max coil siameter starting at 300 mm or greater.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday January 7 2018 01:23:31 AEDT AM
  
OK Aziz,

 I will go with your form and be using 5/38 Litz I estimate the resistance to be somewhere around 10 ohms Max coil siameter starting at 300 mm or greater.

Regards, Ian. ::62::

Hi Ian,

ok, this is fine. Litz wire is perfect as it is quite soft for winding on XPS coil former. Try to achieve at least 600 µH (better 800 - 1000 µH) and lets see, whether we can get SRF of at least 500 kHz (including shielding and coil cable). You may even start at 400 mm so the RX gain compensation factor decreases a bit. It is not critical.
Most important is DC resistance < 15 Ohm and SRF >= approx. 500kHz (low capacitance).

BTW, XPS is stronger than EPS. Try to get XPS sheets for coil former.

I have found at home a 0.4 mm silver plated copper wire. I think, it is too stiff to wind on XPS coil former. I will buy a 0.3 mm and 0.2 mm wire and will see, what I can make of it. BTW, as I leave more space between the loops, I can even use non-enamelled wire.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Sunday January 7 2018 11:09:12 AEDT AM
If you want to make printable circle templates have a look here, just move the slider to alter number of slots and dia.

https://www.blocklayer.com/circle-divider.aspx


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Sunday January 7 2018 11:21:10 AEDT AM
Quote
Making basket weave RX coil is a bit difficult for thin wires needing some space between the windings.



Aziz are you saying that we should cut notches where the wires cross in the slots to add more distance between the wires so they do not touch ?


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Sunday January 7 2018 12:02:35 AEDT PM
  
Hi Aziz,

I will wind a round 3DSS basket weave coil to go with the 24" square mono I will have to source some XPS foam sheet that is what I used before on basket weave coils I will wind a round basket weave coil using .2 enameled wire as I have that and I have layout former for the 3DSS coil what center line diameter should I wind it your call.

Regards, Ian. ::62::

Ian .. make note on direction you wind .. i think from memory both tx and rx have to be wound same direction .. hard to know what direction the standard mono loops are wound .. would this be correct Aziz ??


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday January 7 2018 21:28:17 AEDT PM
  
Quote
Making basket weave RX coil is a bit difficult for thin wires needing some space between the windings.

Aziz are you saying that we should cut notches where the wires cross in the slots to add more distance between the wires so they do not touch ?

Hi 6666,

yes. See picture below for illustration only.

This is required for thin coil wires without any significant insulation material (enamelled copper wire, litz wire, etc.) to maintain more distance to each loop turns and to fix the wires from movement.

More info later. I have no time at the moment.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday January 7 2018 21:42:38 AEDT PM
  
Ian .. make note on direction you wind .. i think from memory both tx and rx have to be wound same direction .. hard to know what direction the standard mono loops are wound .. would this be correct Aziz ??

Hi gef12,

no problem at all. You can flip over the RX coil to change its winding direction.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday January 7 2018 21:50:38 AEDT PM
Hi all,

here is a nice web site for spider web coils:
http://www.welt-der-alten-radios.de/detektor-spider-183.html

The coil former on the right side can be used for wood/plastic coil formers to reduce the dielectric constant and hence to lower the coil capacitance and coil weight. But we should use the coil former shown on the left side if we use the XPS sheet coil former. We need some mechanical stability of the coil former of course.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday January 7 2018 22:25:02 AEDT PM
Hi all,

this is useful for calculating spider web coil inductance:
http://www.crystalradio.net/professorcoyle/professorcoylespiderweb.shtml
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Monday January 8 2018 08:00:08 AEDT AM
  
  
Quote
Making basket weave RX coil is a bit difficult for thin wires needing some space between the windings.

Aziz are you saying that we should cut notches where the wires cross in the slots to add more distance between the wires so they do not touch ?

Hi 6666,

yes. See picture below for illustration only.

This is required for thin coil wires without any significant insulation material (enamelled copper wire, litz wire, etc.) to maintain more distance to each loop turns and to fix the wires from movement.

More info later. I have no time at the moment.
Aziz


Thanks Aziz, looking at my prototype with just 13 slots x 80 turns = 2080 notches , that will take some time to do.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 8 2018 09:26:09 AEDT AM
  
Thanks Aziz, looking at my prototype with just 13 slots x 80 turns = 2080 notches , that will take some time to do.

I for one would take 7 or 9 slots. Not more.

You could use each notch twice (bottom and top side of the coil former) as the windings interleave on odd number of slots. So for each diameter, you can wind two loops. At the end, you have half radial winding distance and more coil capacitance. Or make the radial distance twice long and wind two loops per diameter. Less work.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 8 2018 09:35:57 AEDT AM
Hi all,

here is an useful Excel sheet for calculating the true wire spacing and slot angle on spider web coils.
The notch spacing is not the same as wire-to-wire spacing.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Monday January 8 2018 12:56:53 AEDT PM
I might try to  use each notch twice   ::419::

Here is a 9 segment template


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Monday January 8 2018 13:29:04 AEDT PM
  
  
Thanks Aziz, looking at my prototype with just 13 slots x 80 turns = 2080 notches , that will take some time to do.

I for one would take 7 or 9 slots. Not more.

You could use each notch twice (bottom and top side of the coil former) as the windings interleave on odd number of slots. So for each diameter, you can wind two loops. At the end, you have half radial winding distance and more coil capacitance. Or make the radial distance twice long and wind two loops per diameter. Less work.

Aziz

Aziz .... so if using Litz wire vice the single core wire ...  would same spacing be required or can be closer me thinks ...
your thoughts ...


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 8 2018 20:27:46 AEDT PM
  
Aziz .... so if using Litz wire vice the single core wire ...  would same spacing be required or can be closer me thinks ...
your thoughts ...

Hi gef12,

same spacing. The purpose of the spacing is to lower the coil capacitance so we can have more RX coil inductance, which than compensates for RX gain losses.

Thin Litz wire is easy to wind as it is very flexible and is the best wire you can use. But very expensive.
I for one would start with a thin enamelled single core copper wire (0.3 mm). It's cheap for prototypes.

It is quite possible, that we can not achieve SRF of 500 kHz. Then the next question is, how far can we reduce the SRF to maintain detectors proper operation. Another question is, how low the RX coil inductance can be, that the sensitivity gain of the detector setting can compensate for RX gain losses. Its a balance act of low capacitance and high inductance of the RX coil.

The Trial & Error method will reveal the answers sooner or later.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 8 2018 21:18:45 AEDT PM
Hi all,

another possibility for lowering the RX coil capacitance and increasing the inductance is to go for more volume space.

Two stacked spider web coils connected in series (same winding direction of course) with a 5 mm XPS spacer between them. 5+5+5+5+5 = 25 mm, two for RX coils and three for distance spacer including the shielding spacer.
Then we can have more interwire space to go for low capacitance and high inductance.

This is the last option, when we can't get the RX coil capacitance as low as required and as high inductance as required.

BTW, the XPS sheets can be easily glued with super glue. All the RX coil windings will be tight when the XPS spacer glued on the RX coil and won't be sensitive to mechanical shocks. That's the reason for going for spider web coils instead of basket weave winding technique.

The TX coil can be wound as basket weave as it is not that critical of course.
 ::419::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 8 2018 21:34:36 AEDT PM
Hi all,

I hope to draw some sketches about what happens on severe ground conditions to magnetic fields soons.
You will immediately see, why this coil will outperform equivalent sized standard mono coils. And why you will be able to detect big deep gold on highly mineralized ground.

This is what I unfortunately can't simulate with my coil software.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 9 2018 02:46:29 AEDT AM
Yeah,

I have found my enamelled copper wire now.
0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 mm wires.

I'll start with the 0.3 mm wire and will see, how the RX coil winding gets.
 ::10 ::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 10 2018 00:55:16 AEDT AM
Hi all,

I have been winding my first test spider web coil on XPS sheet.
0.3 mm is the thickest enamelled copper wire to be wound easily.
True Litz wire should be much easier to wind as it is very flexible.
The slot width should be less than 5 mm. 2-4 mm would be sufficient enough and would avoid moving wires from the notches.
One also could wind the RX coil on thicker XPS sheets (6 mm up to 10 mm) to avoid such problems.
Number of slots not more than 9. 7 or 9 is ideal (less work).
Use two loops per notch (two loops per diameter). So you don't need to mark and cut much notches.

The RX coil need not to be art work. Tightness of the windings is more important.
I'll make another XPS coil former and practice my winding skill.
The RX coil looks really fine.
 ::419::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 10 2018 09:30:08 AEDT AM
Nice work Aziz, how do you find winding with the 5 mm XPS sheet?
I have played around with it but found it to be very brittle.
It machines well on my cnc and I was hoping to continue making coil forms with the thinner sheet  but I am looking for some other material to try.
PVC foam cuts really well, can be vacuum formed and is more robust but capacitance of coil will most likely go up.

Cheers

muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 10 2018 09:48:15 AEDT AM
On second thoughts, after reading safety notes from PVC foam board (that's closed cell PVC foam) DON'T heat form it without plenty of ventilation!
The fumes produced contain Hydrochloric acid among other nasty noxious fumes, not good for machines or humans.....

Always a trade off lol

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 10 2018 11:05:53 AEDT AM
  
On second thoughts, after reading safety notes from PVC foam board (that's closed cell PVC foam) DON'T heat form it without plenty of ventilation!
The fumes produced contain Hydrochloric acid among other nasty noxious fumes, not good for machines or humans.....

Always a trade off lol

Cheers
Muntari

Hi Muntari,

well, EPS won't work. It is too soft. XPS works well with thin flexible wires if you work gently.

You can go for wood for coil former. There are 5x10 mm rectangular wood rods available. You can cut the notches first and glue the rods onto a small round wood plate. Two rods for each slot.

Same with rectangular plastic rods.

But I like the XPS sheets. The windings will be tight after gluing the shielding spacer. Super low dielectric constant too.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: autitch on Wednesday January 10 2018 11:27:10 AEDT AM
  
  
Have been following with interest thus far .. very interesting Aziz .
I opened up an old DD coil some time back . The rx windings are of thinner wire than the much thicker Tx .. both are litz wire.
Rx is approx 25 - 30 turns  and is approx 7.5 inch dia.  There is also a 680 ohm damper in parallel across this Rx coil .
keep up the good work
For info

Hi gef12,

that's interesting. The info is unfortunately irrelevant until you tell the brand name of the coil.
SD/GP/GPX compatible coil?

The RX coil must be damped somewhere. Either in the coil housing/coil plug housing or in the detector.

But how did Ian measure the SRF of the RX coil, when there is a damping resistor connected to it?
Just wondering.

Cheers,
Aziz

Hi Aziz, 
As previously mentioned I’ve been following this thread with great interest and you’ve motivated me to built  my first coil.  The paper design of the RX coil is progressing well and I’m currently sourcing the materials I require to realise my first coil.

I require a little help.  You’ve indicate on the above post that “The RX coil must be damped somewhere. “

I was wondering how to calculate the required damping resistor for a specific coil. 

Thanks in advance.

AuTitch



Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday January 10 2018 16:27:22 AEDT PM
Muntari,

You could try some HIPS sheet I am picking a sheet up in town on Friday it is 3 mm thick and I envision gluing two sheets together I also have some Styrofoam sheet that is used under floating floors it is 2 mm and I have glued three of these together It will be the lightest but remains to be seen if it is rigid enough with epoxy bonding the sheets together the marking and slotting form is completed.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday January 10 2018 17:38:18 AEDT PM
For RX coil, to lower inter-winding capacitance, we need
small number of turns and ferrite basket coil like this:

(https://i62.servimg.com/u/f62/19/61/60/05/ferrit10.jpg)


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 10 2018 22:35:09 AEDT PM
  
Hi Aziz, 
As previously mentioned I’ve been following this thread with great interest and you’ve motivated me to built  my first coil.  The paper design of the RX coil is progressing well and I’m currently sourcing the materials I require to realise my first coil.

I require a little help.  You’ve indicate on the above post that “The RX coil must be damped somewhere. “

I was wondering how to calculate the required damping resistor for a specific coil. 

Thanks in advance.

AuTitch

Hi AuTitch,

the RX coil damping resistor is usually built in the coil housing itself and is connected parallel to the RX coil. But we are going to build a small coil adapter box, where the RX coil damping resistor is placed and connected parallel to the RX coil.

The damping resistor Rd is calculated as follows:
Rd = 0.5 * sqrt(L/C), where

L = RX coil inductance in Henry H
C = Total RX coil capacitance, it is a sum of all parasitic capacitances of coils interwire capacitance + shielding capacitance + cabling capacitance + small amount of the input stage capacitance of the detector (10 - 20 pF). The unit of C Farad F.
Rd in Ohms

Example:
L = 800 µH
C = 180 pF
Rd = 0.5*sqrt(800*1e-6/180*1e-12) = 0.5*sqrt(444444.4) = 1054 Ohm

Before we can calculate the damping resistor, we have to know the RX coils inductance L by measuring it and we can obtain the coils capacitance by the measurement of the self resonant frequency (SRF) of the coil.

SRF = 1/(2*pi*sqrt(L*C)), where

L = coils inductance,
C = coils capacitance (total, including shielding and cable)

Solve for C and you know the capacitance. Add 10-20 pF for the input stage and calculate the damping resistor Rd.

C = 1/(4*PI*PI*SRF*SRF*L), where

PI = 3.1415..
SRF = self-resonant frequency of the coil in Hz
L = coils inductance in Henry
C in Farad

That's all.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 10 2018 22:47:14 AEDT PM
  
For RX coil, to lower inter-winding capacitance, we need
small number of turns and ferrite basket coil like this:

No WM6,

we need more volume space for the RX coil to have more windings and low capacitance.
We also increase the Ampere*turns, which is the cheating part of the game.
Get that ferrite out of the coil. You won't get any benefit only disadvantages.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: autitch on Thursday January 11 2018 08:19:36 AEDT AM
  
  
Hi Aziz, 
As previously mentioned I’ve been following this thread with great interest and you’ve motivated me to built  my first coil.  The paper design of the RX coil is progressing well and I’m currently sourcing the materials I require to realise my first coil.

I require a little help.  You’ve indicate on the above post that “The RX coil must be damped somewhere. “

I was wondering how to calculate the required damping resistor for a specific coil. 

Thanks in advance.

AuTitch

Hi AuTitch,

the RX coil damping resistor is usually built in the coil housing itself and is connected parallel to the RX coil. But we are going to build a small coil adapter box, where the RX coil damping resistor is placed and connected parallel to the RX coil.

The damping resistor Rd is calculated as follows:
Rd = 0.5 * sqrt(L/C), where

L = RX coil inductance in Henry H
C = Total RX coil capacitance, it is a sum of all parasitic capacitances of coils interwire capacitance + shielding capacitance + cabling capacitance + small amount of the input stage capacitance of the detector (10 - 20 pF). The unit of C Farad F.
Rd in Ohms

Example:
L = 800 µH
C = 180 pF
Rd = 0.5*sqrt(800*1e-6/180*1e-12) = 0.5*sqrt(444444.4) = 1054 Ohm

Before we can calculate the damping resistor, we have to know the RX coils inductance L by measuring it and we can obtain the coils capacitance by the measurement of the self resonant frequency (SRF) of the coil.

SRF = 1/(2*pi*sqrt(L*C)), where

L = coils inductance,
C = coils capacitance (total, including shielding and cable)

Solve for C and you know the capacitance. Add 10-20 pF for the input stage and calculate the damping resistor Rd.

C = 1/(4*PI*PI*SRF*SRF*L), where

PI = 3.1415..
SRF = self-resonant frequency of the coil in Hz
L = coils inductance in Henry
C in Farad

That's all.

Cheers,
Aziz

Thanks Aziz for your detailed response.  Your assistance is greatly appreciated.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 11 2018 09:44:28 AEDT AM
  
Muntari,

You could try some HIPS sheet I am picking a sheet up in town on Friday it is 3 mm thick and I envision gluing two sheets together I also have some Styrofoam sheet that is used under floating floors it is 2 mm and I have glued three of these together It will be the lightest but remains to be seen if it is rigid enough with epoxy bonding the sheets together the marking and slotting form is completed.

Regards, Ian. ::62::

Hi Ian, sounds good, thanks for the info, Ill take a look at HIPS, are you sourcing it in SA?
Will be interesting to see how your build goes.

Cheers  Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 11 2018 10:43:59 AEDT AM
  
  
On second thoughts, after reading safety notes from PVC foam board (that's closed cell PVC foam) DON'T heat form it without plenty of ventilation!
The fumes produced contain Hydrochloric acid among other nasty noxious fumes, not good for machines or humans.....

Always a trade off lol

Cheers
Muntari

Hi Muntari,

well, EPS won't work. It is too soft. XPS works well with thin flexible wires if you work gently.

You can go for wood for coil former. There are 5x10 mm rectangular wood rods available. You can cut the notches first and glue the rods onto a small round wood plate. Two rods for each slot.

Same with rectangular plastic rods.

But I like the XPS sheets. The windings will be tight after gluing the shielding spacer. Super low dielectric constant too.

Cheers,
Aziz

Thanks Aziz, I have ordered some more XPS from different supplier, so will see how I go with that.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 11 2018 13:49:09 AEDT PM
  
  
  
On second thoughts, after reading safety notes from PVC foam board (that's closed cell PVC foam) DON'T heat form it without plenty of ventilation!
The fumes produced contain Hydrochloric acid among other nasty noxious fumes, not good for machines or humans.....

Always a trade off lol

Cheers
Muntari

Hi Muntari,

well, EPS won't work. It is too soft. XPS works well with thin flexible wires if you work gently.

You can go for wood for coil former. There are 5x10 mm rectangular wood rods available. You can cut the notches first and glue the rods onto a small round wood plate. Two rods for each slot.

Same with rectangular plastic rods.

But I like the XPS sheets. The windings will be tight after gluing the shielding spacer. Super low dielectric constant too.

Cheers,
Aziz

Thanks Aziz, I have ordered some more XPS from different supplier, so will see how I go with that.

Cheers

Muntari

Aziz, BTW, the PVC foam is a closed cell rigid form, not the soft EPS or PVC as used in underlay or exercise mats etc.
It is 1/2 the weight of solid PVC and much lighter then ABS.

I think I'll machine a former using this and also try Ian's suggestion of HIPS.
The type of  spider coil former that you linked to where the guy was using a CD and using 2 fingers in place of each slot and removing material between those fingers, to me looks a good way to do it using 3 mm material. Weight would be much reduced and rigid enough I think.
Of course not everyone here has a cnc router so it would be more time consuming but for me, it is an obvious way to try it.

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday January 11 2018 14:46:49 AEDT PM
Hi Muntari,

Yes City Plastics in Adelaide I am on the SYP.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 11 2018 15:37:04 AEDT PM
  
Hi Muntari,

Yes City Plastics in Adelaide I am on the SYP.

Regards, Ian. ::62::

Hi Ian,

Ok, thanks I have attached the former I will machine from some rigid material, its just to test strength.

Cheers

Muntari


(http://[img])[/img]


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday January 11 2018 19:37:20 AEDT PM
Hi all,

HIPS is quite expensive. And other extruded plastic sheets too.

A combination wood and EPS or XPS will make a very robust coil former. Even the TX coil can be wound on the same coil former. You then cut the center part of the coil former after finalising the coil and you get still a light weight and robust coil.
I'll show this cheap and easy solution, when I have more free time.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday January 11 2018 22:40:37 AEDT PM
Oh man!,

there is still so much to do and I have not much free time for this stuff.
1. I want to upgrade the coil software, so we can calculate the inductance for our spider web coils more precise. Some coding is required.
2. Theoretical section: Text and sketches waiting for several weeks already.
3. RX coil prototype 1 (I have finished my XPS coil former)
4. Coil prototype 2 (Simple wood/XPS coil former both for TX and RX coils to be built and shown)
5. Continue with the project topics
...
So be patient please.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Thursday January 11 2018 23:48:11 AEDT PM
  

Ok, thanks I have attached the former I will machine from some rigid material, its just to test strength.

Cheers

Muntari

Hi Muntari

Nice coil former design, thank you.

Is this former provided for RX windings only?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 12 2018 10:35:02 AEDT AM
  
  

Ok, thanks I have attached the former I will machine from some rigid material, its just to test strength.

Cheers

Muntari

Hi Muntari

Nice coil former design, thank you.

Is this former provided for RX windings only?

Hi WM6

Thanks
Yes, its just one solution I think will work Ok to keep weight down and is rigid enough to hold its shape.
It's not my original idea, Aziz posted a link showing a CD based spider coil former which I thought was a great idea, so I expanded on that.
I am working on another couple of designs which I'll post up when I get time.

Aziz, some plastic sheet stock is expensive for sure, however, there are some cheap versions around which can be used.
Probably the question for most is how to cut the material....
I just happen to have a CNC router, CNC mill and large format 3D printer so I have options which others may or may not have but I guess my point is, sure, make things as cheap as we can using the tools and materials we have but explore all options. 
Crikey, you could even use MDF as a former if needed, its all in the design.
At the moment with prototypes we are just trying to get the ball rolling so we are following your lead.

If you want, I am happy to make a few formers for you free of charge if it helps.  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 12 2018 11:04:54 AEDT AM
  
..
If you want, I am happy to make a few formers for you free of charge if it helps.  ::62::

Cheers
Muntari

Hi Muntari,

no thank you. I'll go for a mixture of rectangular wood rods (cheap) and XPS. One coil former for TX and RX coil. All wound as spider web.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 12 2018 11:11:09 AEDT AM
Hi all,

I have upgraded my coil software today. I can model spider web coils with slots. Unfortunately it is adding many wire segments and they all take time for calculations.
Ignore the coil model. It is under construction yet.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 12 2018 11:28:02 AEDT AM
Hi Aziz,

No worries.

Excellent work! thanks for sharing.

Is this one you have wound already?

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 12 2018 11:49:07 AEDT AM
  
Hi Aziz,

No worries.

Excellent work! thanks for sharing.

Is this one you have wound already?

cheers

Muntari


No, I'm designing a new coil for the new coil former containing both coils (TX & RX).

The XPS coil former I have made for the RX coil does not get enough inductance.
This is my old XPS coil former data:
Number of slots: 9
XPS sheet thickness: 5 mm
Inner diameter: 8 cm
Outer diameter: 24 cm
Number of turns: 2 x 33 = 66 (2 loops per one notch)
Notch spacing: 2.5 mm
Notch depth: 2-3 mm
Slot width: 2-3 mm
Wire length: 32.7 m
Inductance: 631 µH

The RX coil has not been wound yet. I'm thinking of making a more stable coil former.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 12 2018 11:57:32 AEDT AM
Hi Aziz,

Ok thanks for the info on coil, interesting.

What inductance are you shooting for RX?

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 12 2018 12:42:00 AEDT PM
Hi all,

Here is a modification to last former...
The center section can be removed after winding, or , as it is 40mm diameter... here in Oz that is a standard PVC plumping pipe size so you can remove center and push a bit of pipe into hole to aid in winding of coil...

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 12 2018 13:07:53 AEDT PM
  
Hi Aziz,

Ok thanks for the info on coil, interesting.

What inductance are you shooting for RX?

Cheers

Muntari



800 µH - 1 mH


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 12 2018 13:11:54 AEDT PM
  
Hi all,

Here is a modification to last former...
The center section can be removed after winding, or , as it is 40mm diameter... here in Oz that is a standard PVC plumping pipe size so you can remove center and push a bit of pipe into hole to aid in winding of coil...

Cheers

Muntari
Hi Muntari,

this design is nice. I for one would fill in the sectors with XPS (glued). This gives more stability to the windings.
I'm going to build the wood version (wood rods) and will fill the sectors with XPS.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 12 2018 13:59:50 AEDT PM
Hi Aziz,

Thanks for info on inductance.

Yes I agree on the XPS infill, that was my thought too.

I was also thinking about another way which I will illustrate soon.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 12 2018 14:30:32 AEDT PM
Hi all,

Here is the draft layout with measurements for another Spider coil former.

Outer area is TX inner RX.

Size is arbitrary, let me know what sizes you want but for now this is start.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 12 2018 16:31:09 AEDT PM
Hi All,

Here is a draft version of RX TX spider coil former

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 12 2018 16:57:51 AEDT PM
And here is the sketch of same

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Friday January 12 2018 19:13:43 AEDT PM
Great work Muntari again. Thanks!

Probably middle section should not be removed, cause we need it to place rod mounting ears there, to fixing detectors lower rod on it.



Aziz, regarding TX coil. Does really TX should be build in a basket way like RX? Is it not enough for TX to be simple boundle wound?


Additionally, what RX coil impedance / DC resistance should be expected /suggested?


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 12 2018 21:30:05 AEDT PM
  
Great work Muntari again. Thanks!

Probably middle section should not be removed, cause we need it to place rod mounting ears there, to fixing detectors lower rod on it.

Aziz, regarding TX coil. Does really TX should be build in a basket way like RX? Is it not enough for TX to be simple boundle wound?

Additionally, what RX coil impedance / DC resistance should be expected /suggested?

Hi WM6,

there will be enough space between the TX and RX coil for the coil cable mounting and coil rod mounting.

The TX is not critical as long as you meet the specifications (inductance, SRF, DC resistance). You can make it whatever it looks like: bundle, basket weave, spider web, etc.
But the cheating effect is greater on basket weave and spider web winding technique. You get more loop turns for the TX coil for a specified inductance. So increasing the Ampere*loop turns number. If you increase it, you will have more detection depth compared to a compact bundle TX coill. That's the idea behind it.

RX coil impedance/DC resistance should be below approx. 15 Ohm (for ML machines). We have not specified its inductance yet as we have to try out some RX coils (trial & error method).

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 12 2018 21:40:11 AEDT PM
  
Hi All,

Here is a draft version of RX TX spider coil former

Cheers

Muntari

Hi Muntari,

#4 of your proposals is the one, what I have thought of initially. Instead of plastic, I'm going to use rectangular wood rods glued on a small circular wood plate. Additionally, all the sectors will be filled with XPS (glued). And I will cut the notches for the windings before the wood rods will be glued together. After finalising the coil, I'll get rid of the center region.
This is really cheap and easy to build.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Doug on Friday January 12 2018 23:00:09 AEDT PM
 As this has been such a hot topic (thanks Aziz and all the other contributors) i am proposing to open it up for guests to read unless anyone thinks this is not desirable?
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 12 2018 23:30:30 AEDT PM
  
As this has been such a hot topic (thanks Aziz and all the other contributors) i am proposing to open it up for guests to read unless anyone thinks this is not desirable?
doug ::419::

I appreciate this. I hope, that the coil maker companies act quick and offer us such coils soon.
 ::10 :: ::10 :: ::10 ::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Doug on Saturday January 13 2018 00:02:55 AEDT AM
  
  
As this has been such a hot topic (thanks Aziz and all the other contributors) i am proposing to open it up for guests to read unless anyone thinks this is not desirable?
doug ::419::

I appreciate this. I hope, that the coil maker companies act quick and offer us such coils soon.
 ::10 :: ::10 :: ::10 ::
Aziz

Guest can now  view this board.
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday January 13 2018 00:44:14 AEDT AM
Hi all,

I am continuing with the principle of the TX/RX coils so we can understand what is happening on high ground mineralization and why this coil design will detect big deep gold on highly mineralized ground much much better than the original monoloop coil design.

Lets look at the monoloop coil first. The picture below shows the magnetic field strength distribution and direction around the monoloop coil. As you can see, the magnetic field strength is very high nearby the coil windings.

to be continued..
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday January 13 2018 00:59:10 AEDT AM
.. to be continued..

Magnetic fields entering a high permeable matter (iron mineralized ground) will be refracted.
The steeper the magnetic field, the less refraction.
The shallow the magnetic field, the more refraction.
The more ground mineralization, the more refraction.

Below is an example for µr=1 (air) and µr=10 (hot ground). You can see, that even small deviations from the perpendicular magnetic fields entering the ground will be refracted much. This is an exaggerated example of course. But shows the principle.
You can play with the Excel file in the attachment below (rar file).

If you really have severe ground conditions (iron ore sites), this ground acts like a magnetic field shield. The magnetic fields can't penetrate it much. Only a small center region of the TX coil will penetrate the ground deep. Most magnetic fields will be shalow depth (particularly nearby the TX coil windings) and is causing huge ground noise due to high magnetization of the ground there.

.. to be continued..


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday January 13 2018 01:24:14 AEDT AM
.. to be continued..

Now lets look at a TX/RX coil (bundle version for simplicity) and see the difference between a mild/benign ground condition and highly mineralized ground condition. On mild/benign ground, the magnetic fields will be refracted less or none, which I haven't shown in the sketch.

On high ground mineralization, the magnetic fields will be refracted heavily. Acting like a magnetic field shield. Most of the magnetic fields don't penetrate the hot ground much deep. Only shallow deep. And this is causing a lot of ground noise due to the magnetization of the mineralized ground below the coil. You can see the exaggerated sketch showing the refracted magnetic fields I have drawn in the picture below.

Fortunately, our RX coil is small and is focussing to the deep penetrating magnetic fields in the center region. So the signal-to-noise-ratio (SNR) will be improved for deep targets and a huge amount of the shallow depth caused ground noise will be simply bypassed or not sensed by the smaller RX coil.
The small RX coil will detect less EMI noise and less target signals (detection depth loss) and also less ground noise. So we can increase our RX gain to compensate for the detection depth loss.

The RX gain compensation can be made by
a) more coil windings of the RX coil (more inductance), which is quite easy to do
b) increasing the RX gain setting of the detector (amplifier gain), which is limitted by detector design and is causing amplifier noise too

A good compromise of a) and b) is the best option we are trying to achieve in this project.
 ::62::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday January 13 2018 03:57:07 AEDT AM
Hi all,

I found this again. Gary's PI coil data:

http://chemelec.com/Projects/Metal-1a/Coil-Data.htm

We should easily get ultra-low interwire coil capacitance with basket-weave or spider web RX coils. I don't think, we would get any problems with high inductance RX coils. All right and we will succeed in realising this project.

Then there is a big portion of the shielding and coil cabling capacitance. But this is deterministic and very trivial.
 ::62::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Saturday January 13 2018 04:29:41 AEDT AM
According Garry data, spiral wound is (in case of interwire capacitance) better than basket-weave wound.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday January 13 2018 05:43:43 AEDT AM
  
According Garry data, spiral wound is (in case of interwire capacitance) better than basket-weave wound.

No! The coil there isn't a basket weave coil.
The basket weave coils I have shown here as coil models will be much lower than spiral coils.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday January 13 2018 10:47:19 AEDT AM
Hi Aziz,
Great work as usual, thanks for sharing. You have been a busy man.
I will sketch up your version of former and post.
Maybe 5mm threaded nylon rod would be useful as the thread would allow wire soaring...of course it's more expensive than wood though but just a thought.

Hi WM6,

Thanks for comments, I understand what you are saying, I guess I was thinking the former would just be an insert and I was trying to decrease weight.

As to bundle or spider winding for TX , I do have another option which I'll draw and post soon.



Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday January 13 2018 10:59:34 AEDT AM
  
Hi Aziz,
Great work as usual, thanks for sharing. You have been a busy man.
I will sketch up your version of former and post.
Maybe 5mm threaded nylon rod would be useful as the thread would allow wire guiding...of course it's more expensive than wood though but just a thought.

Hi WM6,

Thanks for comments, I understand what you are saying, I guess I was thinking the former would just be an insert and I was trying to decrease weight.

As to bundle or spider winding for TX , I do have another option which I'll draw and post soon.



Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday January 13 2018 23:51:18 AEDT PM
Hi all,

I now have a few different plastics sheet material ranging from Lexan, HDPE, foamed PVC, ABS and HIPS and also some different timbers and MDF to try out for formers.
CAD models are done so hopefully I can start machining tomorrow.
The idea is to test some different former shapes for strength while winding and of course weight.
I will Cut the shapes on the CNC and later I'll 3D print the same shape formers which dont have to be super dense or solid prints and I suspect, the latter method might be very light weight ...see how we go.
I'll post as I move along...it will take a while but will be worth the effort.

Btw for those with 3D printers, the former shown in my last post can be printed in sections and snapped together ..or glued to make the complete former so you don't need a large print bed...more on that later first up is some machining

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday January 14 2018 23:59:14 AEDT PM
Hi all,

I have found a way of calculating the SRF and the expected interwire coil capacitance by using the free antenna simulation software 4nec2 (using the NEC2 engine).
I have to take into account the wire data (insulation, dielectric constant, etc.) for the antenna software and have to code my coil software a bit to provide appropriate NEC2-cards for the antenna software.

Due to some software bugs, the antenna simulation does not work always correct. For spiral/basket weave/spider web coils it should work however.
 ::10 ::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 15 2018 01:32:53 AEDT AM
Hi all,

I have found the reason for incorrect antenna simulation results & bugs and can solve the issues easily.
We will know soon, what SRF and coil capacitance we can expect for a specific coil model.
This is a big step forward in coil design: The marriage of the antenna modelling software (4nec2/NEC2) with my coil software.
 ::10 ::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 15 2018 09:52:52 AEDT AM
Hi all,

this is how it works:
My coil software can export the coil model into naked NEC2-file. This file needs some NEC2-cards (information) so the coil can be simulated as an (bad) antenna by an antenna simulation software (4nec2 using NEC2-engine).
Then a frequency sweep calculation is made on the coil antenna. For each frequency step, the antennas complex impedance is calculated.

Z = R + jX, where

Z = antennas complex impedance,
R = real part of the complex impedance,
X = imaginary part of the complex impedance.

For resonance, the reactive part X must be 0.

The frequency step with X=0 is picked up and there is the SRF (self-resonant frequency).
As the coil inductance is known by my coil software, the coils interwire capacitance can be calculated easily.

It seems, that I have to upgrade my coil software a bit so the exported NEC2-file can be directly used by the antenna software.
Below is the obtained SRF of approx. 3.49 MHz for a spider web TX coil shown in the picture.
This is so nice now.
 ::62::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday January 15 2018 09:59:52 AEDT AM
Great news Aziz, look forward to seeing the results.

I have to go find my spools of wire, I put them in a box when I moved workshop now can't find the box...grrr

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday January 15 2018 10:01:42 AEDT AM
  
Hi all,

this is how it works:
My coil software can export the coil model into naked NEC2-file. This file needs some NEC2-cards (information) so the coil can be simulated as an (bad) antenna by an antenna simulation software (4nec2 using NEC2-engine).
Then a frequency sweep calculation is made on the coil antenna. For each frequency step, the antennas complex impedance is calculated.

Z = R + jX, where

Z = antennas complex impedance,
R = real part of the complex impedance,
X = imaginary part of the complex impedance.

For resonance, the reactive part X must be 0.

The frequency step with X=0 is picked up and there is the SRF (self-resonant frequency).
As the coil inductance is known by my coil software, the coils interwire capacitance can be calculated easily.

It seems, that I have to upgrade my coil software a bit so the exported NEC2-file can be directly used by the antenna software.
Below is the obtained SRF of approx. 3.49 MHz for a spider web TX coil shown in the picture.
This is so nice now.
 ::62::
Cheers,
Aziz

Excellent work Aziz, very nice.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: autitch on Monday January 15 2018 10:45:21 AEDT AM
HI Aziz,

Thanks for posting the coil magnetic flux simulation diagrams.  A picture is certainly worth a thousand words.   With these diagrams you clearly demonstrate the coplanar large TX small RX concept  and benefits.

Some questions springs to mind.

You show the magnetic flux arrow pointing down through the centre of the coil. Is this critical?  What happens if the magnetic flux is reversed due to winding direction or electrical polarity connection.

To achieve the magnetic flux to pointing down through the centre of the coil am I correct in assuming that the coil winding handing and voltage/current polarity needs to be in a certain configuration and if so what guidelines would you give. 

Since a detector produces a pulse current/voltage, I’m assuming that it’s a little difficult to measure or ascertaining  the direction of magnetic flux.  Once a coil is built, how could one easily determine magnetic flux  direction so that it's configured to produce the desired flux direction.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 15 2018 20:30:38 AEDT PM
  
HI Aziz,

Thanks for posting the coil magnetic flux simulation diagrams.  A picture is certainly worth a thousand words.   With these diagrams you clearly demonstrate the coplanar large TX small RX concept  and benefits.

Some questions springs to mind.

You show the magnetic flux arrow pointing down through the centre of the coil. Is this critical?  What happens if the magnetic flux is reversed due to winding direction or electrical polarity connection.

To achieve the magnetic flux to pointing down through the centre of the coil am I correct in assuming that the coil winding handing and voltage/current polarity needs to be in a certain configuration and if so what guidelines would you give. 

Since a detector produces a pulse current/voltage, I’m assuming that it’s a little difficult to measure or ascertaining  the direction of magnetic flux.  Once a coil is built, how could one easily determine magnetic flux  direction so that it's configured to produce the desired flux direction.

AuTitch


Hi AuTitch,

magnetic field direction is irrelevant as the same refraction happens to the magnetic fields in the reverse direction.  I have choosen the direction down for illustration.

For a PI/metal detector it is irrelevant, which direction the magnetic fields have. Only the current direction (winding direction) of the TX coil windings determines the magnetic field direction.

You can measure the magnetic fields using Hall-sensors. Or use the right hand grip rule to determine the magnetic field direction.
https://en.wikipedia.org/wiki/Right-hand_rule#Electromagnetics

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 15 2018 23:11:02 AEDT PM
Hi all,

4nec2 supports insulation specifications (radius and dielectric constant). We can simulate teflon/PE/PU.. coated wires with ease.
Unfortunately not more. The gap material between the wires for the spider web coils can't be simulated.
For EPS/XPS isn't much critical as the dielectric constant (relative permittivity) for it is very very small and neglectable (1.03).

I'm upgrading my coil software for more 4nec2 support.
And when I'm finished, I'll try to simulate gary's spiral coil for tests.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday January 15 2018 23:38:10 AEDT PM
  
Hi all,

4nec2 supports insulation specifications (radius and dielectric constant). We can simulate teflon/PE/PU.. coated wires with ease.
Unfortunately not more. The gap material between the wires for the spider web coils can't be simulated.
For EPS/XPS isn't much critical as the dielectric constant (relative permittivity) for it is very very small and neglectable (1.03).

I'm upgrading my coil software for more 4nec2 support.
And when I'm finished, I'll try to simulate gary's spiral coil for tests.

Cheers,
Aziz

Hi Aziz,

I downloaded 4nec2 from the link you provided a few posts ago and it is quite nice software.
I'll need to spend some more time on it later but at the moment I'm working on different coil former ideas. Also, as you say XPS dielectric constant is not really a problem for the proposed use.
Thanks for sharing your knowledge.
I'll post some photos and drawings of what I'm up to but with the weather about to ramp up to around 40 deg C here in next few days, I won't be out in the workshop for long so most likely more drawings first.
Did you Manage to find time to build your wooden former yet?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: mylab on Tuesday January 16 2018 01:24:52 AEDT AM
I am looking forward to some actual physical testing of Aziz's concentric coil once completed at an in-ground mineralised test site up against the spiral wound mono coil to see which comes out on top and provide some insight if this concentric has indeed an advantage over the spiral for extra depth and also operate quieter on mineralised ground.

Although depth is more important as detector settings can be used to quieten things down.

However I expect we would need to work out what the equivalent size spiral mono would need to be for a fair comparison?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday January 16 2018 09:34:30 AEDT AM
  
I am looking forward to some actual physical testing of Aziz's concentric coil once completed at an in-ground mineralised test site up against the spiral wound mono coil to see which comes out on top and provide some insight if this concentric has indeed an advantage over the spiral for extra depth and also operate quieter on mineralised ground.

Although depth is more important as detector settings can be used to quieten things down.

However I expect we would need to work out what the equivalent size spiral mono would need to be for a fair comparison?

Like we all are I guess but I am happy to work through to that logical conclusion as Aziz puts forward his ideas and theory behind them.
If Aziz produces a tool that helps others build coils to suit their needs, then that is a great achievement.

As to equivalent coil sizes, that's an interesting point since the receive coil on the concentric will be smaller than the TX.

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: mylab on Tuesday January 16 2018 11:21:20 AEDT AM
  

As to equivalent coil sizes, that's an interesting point since the receive coil on the concentric will be smaller than the TX.

Cheers

Muntari



There appears to be a limit for the maximum size that a spiral flat wound mono coil can be wound up too to outperform a normal bundle wound mono coil.

That maximum size if we look at what two Australia aftermarket coil manufactures have produced so far with their spiral flat wound mono coils then one is 18” (45cm) and the other 19” (48cm) for their outside diameters.

Therefore would it be fair to say for a fair comparison then Aziz’s type concentric type coil would need to be of similar / same outside diameter?

Cheers.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday January 16 2018 12:00:23 AEDT PM
  
  

As to equivalent coil sizes, that's an interesting point since the receive coil on the concentric will be smaller than the TX.

Cheers

Muntari



There appears to be a limit for the maximum size that a spiral flat wound mono coil can be wound up too to outperform a normal bundle wound mono coil.

That maximum size if we look at what two Australia aftermarket coil manufactures have produced so far with their spiral flat wound mono coils then one is 18” (45cm) and the other 19” (48cm) for their outside diameters.

Therefore would it be fair to say for a fair comparison then Aziz’s type concentric type coil would need to be of similar / same outside diameter?

Cheers.


From experience with my gradiometer coils, for depth I would say Aziz's coil would need to be slightly larger if only to give separation between TX / RX coils.
On the other hand, I suspect Aziz's coils will be quieter than a standard mono loop.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: mylab on Tuesday January 16 2018 14:59:41 AEDT PM
  
.... for depth I would say Aziz's coil would need to be slightly larger if only to give separation between TX / RX coils.
On the other hand, I suspect Aziz's coils will be quieter than a standard mono loop.

Cheers

Muntari

Another difference that springs to mind is the overall weight.

The spiral flat wound CT 18" coil weighs in around 1200g (1.2Kg) and the NF 19" around 1100g (1.1Kg)

Be interesting what Aziz's concentric designed coil's overall weight ends at up in comparison, especially if having to be larger in size to match or out-depth both of these spiral flat wound monos?

cheers.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday January 16 2018 16:08:44 AEDT PM
Hi Mylab

I believe the size increase will be due to inter-wire spacing more than anything else but we just have to make some prototypes and see if we can match Aziz's calculated requirements.

Aziz, does your software calculate wire length required? I know its probably a silly question but had to ask.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday January 16 2018 17:00:38 AEDT PM
A very dirty and quick calculation for a 350mm outside diameter spider wound search coil  .56mm coppper wire RX coil @1200uH (80turns) = 0.150kg     ,  1mm copper wire @ 300uH  (25 turns) = 0.175kg. Like I said quick and dirty check....

So the coil copper weight is not the biggest problem as far as I can see.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 16 2018 19:49:22 AEDT PM
  
...Aziz, does your software calculate wire length required? I know its probably a silly question but had to ask.

Yes.
Physical bending of wires like in the spider web coils require slightly more length as I can not model the bending effect accurate enough.

The inductance calculation is quite accurate even when I approximate the surface integral with the Monte Carlo method (the random-method).

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 16 2018 20:06:11 AEDT PM
Hi all,

there is slow progress with the antenna modelling software.
I think that the SRF calculation won't be correct or accurate.
I infringe the antenna modelling design guidelines:
- Coil wire elements too small compared to the wave length (lambda = c/f). I get error and warning messages.
(Hey, I do not want to radiate energy with it. I just want to get the impedance of my sh1t of wires!!)
- Emulation of the insulation material is not accurate. Note that the NEC-engine does not support insulation material and 4nec2 approximates it with a load card 2 (LD 2).

I have modelled garys coil and the antenna software does not deliver the correct SRF. There is only minimal change with and without insulation material. The output can't be correct.

We have to make some RX coil prototypes and measure them. There is no other way.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 16 2018 20:35:29 AEDT PM
Hi all,

there is more weight for the coil of course:
1. The cheating effect (increasing the ampere-turns) require more loop turns for a specific inductance. More copper = more weight. Particularly true for the thick and heavy TX coil wires. That's the reason why the RX coil wire should be thin and should not have heavy insulation material. Thin Litz wire or enamelled copper wire is good for us.

2. Coil frame
We have to wind and fix the RX coil somewhere. It requires some material to realise it. That's the reason, why I like the XPS coil former.
I think, that the RX coil interwire capacitance is not that critical and much and we can use the enamelled copper wire and wind it on the coil former without using notches for the windings.
Some prototypes and measurements will give us the answers.

Most important thing:
The coil idea is not new!

But I'm wondering, why it has not been implemented during 10 - 20 years yet.
The coil makers:
- are too dumb
- do know nothing about coils (but are excellent in copying ideas)
- made mistakes in implementing such coils
- haven't fixed the (RX) coil capacitance problem
- have recognized, that the principle won't give any benefits
...

What's the most appropriate Occam's Razor answer for it?
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 16 2018 21:03:34 AEDT PM
  
..
Did you Manage to find time to build your wooden former yet?
Hi Muntari,

no, but I have wound a RX coil on XPS coil former without using notches. Just for tests and measurements.

I have found a 100 ft ribbon cable at home. I took one strand off it and have wound a spider web RX coil.
The single strand ribbon cable is:
5/28AWG, the core diameter is approx. 0.4 mm and has 5 strands of tinned copper wire.
The total wire diameter (+insulation) is approx. 1 mm.
The RX coil:
Ri = 49 mm (inner radius)
Ro = 99 mm (outer radius)
N=60 (number of loop turns)
L = 580 µH (calculated)
R = 6.2 Ohm (calculated)
Wire length = 28.6 m (calculated).
But due to the wire bending effect and slight loose windings, I did require slightly more wire length (1 - 1.5 m or so).

I will do more RX coils for measurements. But I haven't prepared my work bench yet. So I can't measure anything right now.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 17 2018 09:52:27 AEDT AM
  

Most important thing:
The coil idea is not new!

But I'm wondering, why it has not been implemented during 10 - 20 years yet.
The coil makers:
- are too dumb
- do know nothing about coils (but are excellent in copying ideas)
- made mistakes in implementing such coils
- haven't fixed the (RX) coil capacitance problem
- have recognized, that the principle won't give any benefits
...

What's the most appropriate Occam's Razor answer for it?
Cheers,
Aziz

Hi Aziz,

Economics and an attitude of white goods manufacturers..like don't stick your neck out too far because others aren't doing it yet..

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 17 2018 09:59:58 AEDT AM
  
  


I will do more RX coils for measurements. But I haven't prepared my work bench yet. So I can't measure anything right now.

Cheers,
Aziz

No problems Aziz, it all takes time and thanks for all your work, its good to see you back online

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 17 2018 10:02:25 AEDT AM
Hi Ian,

How are you going with your former, have you had time to get back to it?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 17 2018 15:34:02 AEDT PM
Hi All,

Here is a view of coil size relative to the former I posted a while ago.

The TX RX coil ratio is 0.4    
Inner RX 80mm outer RX 195mm
Inner TX 273  outer 351mm

The inter-wire spacing is .5 of wire diam

RX wire is 80T 0.56mm
TX wire is 25T  1mm

Ill post more on this soon

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday January 17 2018 16:29:26 AEDT PM
Hi Muntari,

Yes I have one former finished it is 6 mm of XPS with  1 mm Styrofoam sheet each side and I have cut one 3 mm HIPS one now waiting for Litz to arrive my start diameter will be 350 mm which should go well with the 590 center line diameter of the square spiral wound coil which I believe was made by Nuggetfinder as a tow coil judging by the length of coax it is what I will use as the TX coil so I will be able to test on targets as both Aziz's configuration or as a Mono we will see if there is any advantages.

Likewise it is a touch hot here to play in the workshop.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 17 2018 17:05:11 AEDT PM
Hi All,

Here is same coil with different coil ratio and inter-wire spacing
Inductance values Ill add later, I'm just trying to show min max sizing relative to wire spacing and ratio .4 to .7

The TX RX coil ratio is 0.7   
Inner RX 80mm outer RX 241mm
Inner TX 409  outer 503mm

The inter-wire spacing is same as wire diam

RX wire is 80T 0.56mm
TX wire is 25T  1mm 

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 17 2018 19:36:03 AEDT PM
  
Hi All,

Here is a view of coil size relative to the former I posted a while ago.

The TX RX coil ratio is 0.4    
Inner RX 80mm outer RX 195mm
Inner TX 273  outer 351mm

The inter-wire spacing is .5 of wire diam

RX wire is 80T 0.56mm
TX wire is 25T  1mm

Ill post more on this soon

Cheers

Muntari


Hi Muntari,

your RX coil in the sketch is too small in the first instance and you would require much more RX gain compensation.
1. We don't know, how much we can compensate the RX gain in the detector setting.
2. We are dealing with more amplifier noise, when we are compensating the RX gain mostly in the detector amplifier.
3. To compensate the RX gain, we also would require much more RX coil inductance.
4. High coil inductance is causing high coil capacitance and hence limitting the minimum RX coil size.

I for one would let the RX radius go up to 170-180 mm (minimum 150 mm).
Best start with larger RX coil size and steadily reduce its size in the next prototypes when the RX coil works.

Note, that the inner windings of the RX coil don't contribute much to the inductance.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Wednesday January 17 2018 21:15:14 AEDT PM
Thanks Aziz for your work .. interesting. When i have some time i will get to work  lol


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 17 2018 21:50:10 AEDT PM
  
Hi Muntari,

Yes I have one former finished it is 6 mm of XPS with  1 mm Styrofoam sheet each side and I have cut one 3 mm HIPS one now waiting for Litz to arrive my start diameter will be 350 mm which should go well with the 590 center line diameter of the square spiral wound coil which I believe was made by Nuggetfinder as a tow coil judging by the length of coax it is what I will use as the TX coil so I will be able to test on targets as both Aziz's configuration or as a Mono we will see if there is any advantages.

Likewise it is a touch hot here to play in the workshop.

Regards, Ian. ::62::

Great news Ian, Cant wait to see what you have done.
Ill get to mine once heat dissapears

stay cool over the next few days its going to be an inside kinda week ending

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday January 17 2018 22:03:02 AEDT PM
  

Note, that the inner windings of the RX coil don't contribute much to the inductance.


Does this mean that RX could be logarithmic wound (from center to outer windings)?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 17 2018 22:19:25 AEDT PM
Hi Aziz,


Yep, I understand the issue of amp noise and sensible gain.
Not a problem, on coils that's fine its easy to change.
I was going by your ratios mentioned earlier from .4 to .7 but that's Ok, its about all being on the same page.

Strictly speaking of course, my sketches are not yet spider wound, both these drawings are meant to show approx ratios and spacing along with inductance so folk can see the difference from one extreme to the other.

I have also been working on a very novel method to produce a cross between spider and spiral wound coils which will take the pain away from winding them.
These drawings come first though and as you have already stated, the RX is too small but I think to start at 170mm and still achieve the 1000 - 1200uH you stated, we are going to have quite a large coil, may have to stack a couple or use very fine gauge wire or minimal wire to wire spacing, something will have to give.

Look at the outer TX size now it is 500mm on last drawing.

Anyways, I will certainly redraw, I don't have a problem with that, lets see how we end up size wise with the required inductance.
I'll try a few different configurations however I'm basing my calculated inductance on a spiral wound coil atm.


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 17 2018 22:34:57 AEDT PM
  
  

Note, that the inner windings of the RX coil don't contribute much to the inductance.


Does this mean that RX could be logarithmic wound (from center to outer windings)?

Yes. You could do it if you like.
 ::419::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 17 2018 22:49:55 AEDT PM
  
Hi Aziz,


Yep, I understand the issue of amp noise and sensible gain.
Not a problem, on coils that's fine its easy to change.
I was going by your ratios mentioned earlier from .4 to .7 but that's Ok, its about all being on the same page.

Strictly speaking of course, my sketches are not yet spider wound, both these drawings are meant to show approx ratios and spacing along with inductance so folk can see the difference from one extreme to the other.

I have also been working on a very novel method to produce a cross between spider and spiral wound coils which will take the pain away from winding them.
These drawings come first though and as you have already stated, the RX is too small but I think to start at 170mm and still achieve the 1000 - 1200uH you stated, we are going to have quite a large coil, may have to stack a couple or use very fine gauge wire or minimal wire to wire spacing, something will have to give.

Look at the outer TX size now it is 500mm on last drawing.

Anyways, I will certainly redraw, I don't have a problem with that, lets see how we end up size wise with the required inductance.
I'll try a few different configurations however I'm basing my calculated inductance on a spiral wound coil atm.


Cheers

Muntari

Hi Muntari,

0.8 .. 1.0 R: Fill radius area for the TX windings
0.7 .. 0.4 R: Fill radius area for the RX windings
You don't need to fill all the regions with windings.
It says, that the windings should be approx. in the region.
The bigger the RX coil in relation to the TX coil, the less RX gain compensation is required. The less problems we will have in the first instance.

There are many uncertain parameters we have to figure out yet:
- Enough gain margin of the detector (detector setting)?
- Coil capacitance: can we build the RX coil with specified SRF of approx 500 kHz with enough high inductance?

It is completely wrong to start with relative small RX coils.  Better start with larger RX coils. So the required RX gain compensation factor will be small. Then, when it works, you can make smaller RX coils.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 17 2018 23:19:02 AEDT PM
Hi Aziz,

Thanks ,
That's Ok,  its not my intention to start out with small RX, I'm just posting drawings so we can clarify and keep the ball rolling.
Better to be around the mark for prototypes than not else how can we compare, that's just just my thoughts anyways.

So if we are shooting for 1200uH and inside diam of 180mm say .4 mm wire 65 turns and spacing of say 1.2 to 1.3mm we are looking at roughly 320 to 330mm outside diam for RX.

What is the size ratio you are looking at between RX and TX, I mean there will be a point where we have no benefit with the idea, I guess that's what we need to find out.

It all good...

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 17 2018 23:39:44 AEDT PM
Hi Aziz,

Its late here now so I will sketch up a new version and post  tomorrow.
I'm just trying to show the scale of what we are looking at doing..may be helpful...may be not...

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: WM6 on Thursday January 18 2018 05:34:42 AEDT AM
  
  
  

Note, that the inner windings of the RX coil don't contribute much to the inductance.


Does this mean that RX could be logarithmic wound (from center to outer windings)?

Yes. You could do it if you like.
 ::419::
Aziz

Maybe Muntari is able to draw such one solution?


Title: Re: The need for big deep gold detectors.
Post by: CRUNCHBIRD on Thursday January 18 2018 07:51:54 AEDT AM
  
  
  
  

Note, that the inner windings of the RX coil don't contribute much to the inductance.


Does this mean that RX could be logarithmic wound (from center to outer windings)?

Yes. You could do it if you like.
 ::419::
Aziz
Aziz, I have not been reading the forum for a long time. I heard that you were back so I checked in to read what everyone is up to. In an earlier post, you mentioned that the High voltage protection circuit that I came up with would have a problem with dual D's or concentric coils due to their normally having a higher resistance. I have used the circuit with such coils. the trick is obvious and extremely simple. Just replace the bias resistor with a simple current source. It works fine even with secondary coils with 30? resistance. Dave Emery. PS: I like your work. You are one smart cookie.


Maybe Muntari is able to draw such one solution?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 18 2018 09:16:46 AEDT AM
  
  
  
  

Note, that the inner windings of the RX coil don't contribute much to the inductance.


Does this mean that RX could be logarithmic wound (from center to outer windings)?

Yes. You could do it if you like.
 ::419::
Aziz

Maybe Muntari is able to draw such one solution?

Interesting, I'll give it a crack  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 18 2018 10:14:52 AEDT AM
Hi WM6,

Something like this maybe?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Thursday January 18 2018 10:49:54 AEDT AM
  
Hi WM6,

Something like this maybe?

Cheers

Muntari

Hi Muntari, thanks.

I think yes. Probably it could be even more "logarithmic" like this parabolic spiral:

(https://i62.servimg.com/u/f62/19/61/60/05/parabo10.jpg)



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 18 2018 11:35:43 AEDT AM
Ok, i'll change a few things.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday January 18 2018 15:50:40 AEDT PM
The problem is with this wind yes you lower the capacitance but need more winds to get the wanted inductance more winds will the increase capacitance which is what you are trying to avoid.

The coil I am winding is starting at in the first instance ID OF 350 mm and I envision with about 36 turns will be around 900 uh give or take and OD of coil around 462 mm I will add or subtract turns to achieve the required inductance this inductance I will let Aziz decide when the time comes.

Hi Dave.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 18 2018 16:29:49 AEDT PM
  
The problem is with this wind yes you lower the capacitance but need more winds to get the wanted inductance more winds will the increase capacitance which is what you are trying to avoid.

The coil I am winding is starting at in the first instance ID OF 350 mm and I envision with about 36 turns will be around 900 uh give or take and OD of coil around 462 mm I will add or subtract turns to achieve the required inductance this inductance I will let Aziz decide when the time comes.

Hi Dave.

Regards, Ian. ::62::

Hi Ian and WM6,

Here is a modified version but like you Ian, I am struggling to see how to get inductance up with this design without it being quite large.
However WM6 asked if I might try so I did  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 18 2018 16:36:51 AEDT PM
  
The problem is with this wind yes you lower the capacitance but need more winds to get the wanted inductance more winds will the increase capacitance which is what you are trying to avoid.

The coil I am winding is starting at in the first instance ID OF 350 mm and I envision with about 36 turns will be around 900 uh give or take and OD of coil around 462 mm I will add or subtract turns to achieve the required inductance this inductance I will let Aziz decide when the time comes.

Hi Dave.

Regards, Ian. ::62::

Hi Ian,

What size wire will you be using?

BTW, the above drawing is meant to show only spacings and relative size

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday January 18 2018 16:59:02 AEDT PM
Hi Muntari,

5/36 AWG  Litz.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 18 2018 17:05:41 AEDT PM
  
Hi Muntari,

5/36 AWG  Litz.

Regards, Ian. ::62::

Thanks Ian,

I'm just going to machine the former and get started on my version.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday January 18 2018 17:51:01 AEDT PM
Hi all,

the log-radial RX coil would not give you any benefit however. Only disadvantages:
- less ampere-turns (less cheating effect)
- more coil capacitance
- difficult to wind

Forget it quickly.
Only the opposite solution (more loop turns for small radius) would give you some benefit on extremely mineralized ground.
Then again, more disadvantage as mentioned above.
Forget it quickly.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday January 18 2018 18:01:44 AEDT PM
  
The problem is with this wind yes you lower the capacitance but need more winds to get the wanted inductance more winds will the increase capacitance which is what you are trying to avoid.

The coil I am winding is starting at in the first instance ID OF 350 mm and I envision with about 36 turns will be around 900 uh give or take and OD of coil around 462 mm I will add or subtract turns to achieve the required inductance this inductance I will let Aziz decide when the time comes.

Hi Dave.

Regards, Ian. ::62::

Hi Ian,

you can take any inductance between 800 µH and 1400 µH for the first instance. The more we can make it, the less RX gain compensation will be required.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday January 18 2018 18:16:03 AEDT PM
  
Aziz, I have not been reading the forum for a long time. I heard that you were back so I checked in to read what everyone is up to. In an earlier post, you mentioned that the High voltage protection circuit that I came up with would have a problem with dual D's or concentric coils due to their normally having a higher resistance. I have used the circuit with such coils. the trick is obvious and extremely simple. Just replace the bias resistor with a simple current source. It works fine even with secondary coils with 30? resistance. Dave Emery. PS: I like your work. You are one smart cookie.

Hi Dave,

I have to make a spice simulation to see if there is a problem with the current source solution.
 ::419::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 18 2018 21:56:46 AEDT PM
  
Hi all,

the log-radial RX coil would not give you any benefit however. Only disadvantages:
- less ampere-turns (less cheating effect)
- more coil capacitance
- difficult to wind

Forget it quickly.
Only the opposite solution (more loop turns for small radius) would give you some benefit on extremely mineralized ground.
Then again, more disadvantage as mentioned above.
Forget it quickly.
Aziz

I'm personally not going to use the log winding, it was done as a request from WM6.
I can see what he was thinking about when he asked you a few posts ago if it was worth it hence the drawing.
It seems the only way we are going to find out what works best is just build as close to your theoretical as we can. Everyone has ideas to share and every little bit helps to include or exclude as we move along with what you are proposing. I've been here before , many times, designs can end up a world away from the original but one has to start prototyping for proof of concept at some stage and always have someone in the lead.
There will be trade-offs whatever is decided and I only post drawings based on what others are discussing.  Now I would like to help  but this is your baby Aziz tell us what you would like us to do.
Do we wait for your software update and then build protos from that?
Its a great idea with plenty of potential for everyone to learn

Keep up the great work Aziz

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 19 2018 21:42:11 AEDT PM
Hi all,

no problems at all Muntari.

The XPS sheet coil former with notches cut for the windings offer a feature, which can be made quite easily.
For the inner windings of the RX coil, each notch can be used twice (two windings for each radius). For the outer windings of the RX coil, only one winding per notch. This way, the steep and deep going magnetic fields on heavy mineralized ground will be enhanced more.
This is a good compromise if you like. And easy to realise.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 19 2018 23:22:37 AEDT PM
  
Hi all,

no problems at all Muntari.

The XPS sheet coil former with notches cut for the windings offer a feature, which can be made quite easily.
For the inner windings of the RX coil, each notch can be used twice (two windings for each radius). For the outer windings of the RX coil, only one winding per notch. This way, the steep and deep going magnetic fields on heavy mineralized ground will be enhanced more.
This is a good compromise if you like. And easy to realise.

Cheers,
Aziz

Hi Aziz,

Yep that sounds like a plan to me, I'll give it a try, just waiting on a package of  5mm XPS. It's the blue type so I'm hoping it's more rigid than the last lot which was yellow and not very dense although I was assured it was XPS..

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 19 2018 23:35:04 AEDT PM
Hi Aziz,
 what would you estimate the minimum thickness top to bottom of your spider winding would be?
I've thought about it and was thinking 3 mm would be the minimum for a coil around 400mm diam.

Cheers

Muntari




Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday January 20 2018 00:55:22 AEDT AM
  
Hi Aziz,
 what would you estimate the minimum thickness top to bottom of your spider winding would be?
I've thought about it and was thinking 3 mm would be the minimum for a coil around 400mm diam.

Cheers

Muntari


Hi Muntari,

the question is only, whether you can wind the coil onto the coil frame or not. If the XPS sheet is stable enough, you can use 3 mm XPS sheets too.

But I'm going to use 5 mm XPS sheets. 2 mm slot width, approx. 2 mm notch depth, 2 mm notch (radial winding) spacing, two windings per notch, 0.3 or 0.4 mm enamelled copper wire.

Three 5 mm XPS sheets will be used. The middle for the spider web coil frame and the two others for the shielding spacing. Total slightly >15 mm for the RX coil.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday January 20 2018 11:52:11 AEDT AM
  
  
Hi Aziz,
 what would you estimate the minimum thickness top to bottom of your spider winding would be?
I've thought about it and was thinking 3 mm would be the minimum for a coil around 400mm diam.

Cheers

Muntari


Hi Muntari,

the question is only, whether you can wind the coil onto the coil frame or not. If the XPS sheet is stable enough, you can use 3 mm XPS sheets too.

But I'm going to use 5 mm XPS sheets. 2 mm slot width, approx. 2 mm notch depth, 2 mm notch (radial winding) spacing, two windings per notch, 0.3 or 0.4 mm enamelled copper wire.

Three 5 mm XPS sheets will be used. The middle for the spider web coil frame and the two others for the shielding spacing. Total slightly >15 mm for the RX coil.

Cheers,
Aziz

Hi Aziz,

Thanks for the info , yes that would seem very reasonable overall thickness.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Saturday January 20 2018 16:14:20 AEDT PM
Aziz/ Muntari,

To minimize coil to shield capacitance I usually try to have a coil to shield spacing of 10 mm minimum for fast coils a five mm spacing may lower the SRF too much, I have been able to achieve SRF's on spider wound Mono's of 300 mm C/line diameter to around 730 KHz and higher but with wider coil to shield distances. we need to minimize capacitance where ever we can.

I will post pictures of my former's tomorrow 1/ 3 mm HIPS and 1/ 6 mm   + 1 mm HIPS each side total 8 mm but still very light and rigid.

Regards, Ian.::62::


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Saturday January 20 2018 17:46:58 AEDT PM
  
Aziz/ Muntari,

To minimize coil to shield capacitance I usually try to have a coil to shield spacing of 10 mm minimum for fast coils a five mm spacing may lower the SRF too much, I have been able to achieve SRF's on spider wound Mono's of 300 mm C/line diameter to around 730 KHz and higher but with wider coil to shield distances. we need to minimize capacitance where ever we can.

I will post pictures of my former's tomorrow 1/ 3 mm HIPS and 1/ 6 mm   + 1 mm HIPS each side total 8 mm but still very light and rigid.

Regards, Ian.::62::

Ian are you sourcing ur HIPs locally like bunnings or ???


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday January 20 2018 21:59:10 AEDT PM
  
Aziz/ Muntari,

To minimize coil to shield capacitance I usually try to have a coil to shield spacing of 10 mm minimum for fast coils a five mm spacing may lower the SRF too much, I have been able to achieve SRF's on spider wound Mono's of 300 mm C/line diameter to around 730 KHz and higher but with wider coil to shield distances. we need to minimize capacitance where ever we can.

I will post pictures of my former's tomorrow 1/ 3 mm HIPS and 1/ 6 mm   + 1 mm HIPS each side total 8 mm but still very light and rigid.

Regards, Ian.::62::

Hi Ian,

Thanks fir the info, it will be great to see what you have done.

Generally I used spiral wrap then woven braid over that for bundle wound in the MPI for spiral it's only been pcb milled with one side coil the other branched shield and a carbon based sheet on the other side.
Total distance from wire to each shield 6mm and they were fast coils.

I've never wound a spider coil so can't comment.
Look forward to your input ????

Cheers

Muntari





Title: Re: The need for big deep gold detectors.
Post by: Alex on Sunday January 21 2018 12:34:21 AEDT PM
Hi Ian.Sorry this is off the topic but after reading your last post I am curious .With minlab sd .when you wind a coil above 730khz srf do you need to adjust the damping resistor .I have no electronic traning but trying to learn .thanks again


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Sunday January 21 2018 16:29:24 AEDT PM
 ::62::Hi all,

gef12 local plastic supplier but Dotmar Plastic Solutions are the distributor at Regency Park in Adelaide I do not know if they have an office in NT.

Muntari,  I gave up using spiral wrap many years ago my norm was Styrofoam sheet about 16 mm thick I would cut two to shape route out for the coil bundle half each side then encapsulate the coil bundle and bond the two halves with a thin coat of epoxy, sand the form then apply the shield medium.

Alex, no I have never bothered changing the damping resistors in the SD2000M to get the best out of the SD2000 you need to have different frequencies mine has 12 crystal locked channels or  micro controlled variable frequency control I did go to the trouble to put variable damping in my GP3500 but hardly ever changed it once set up although nowadays I use the QED in preference to my minelab machines because of its convenience and light weight.

Formers below.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday January 21 2018 17:55:40 AEDT PM
  
::62::Hi all,

gef12 local plastic supplier but Dotmar Plastic Solutions are the distributor at Regency Park in Adelaide I do not know if they have an office in NT.

Muntari,  I gave up using spiral wrap many years ago my norm was Styrofoam sheet about 16 mm thick I would cut two to shape route out for the coil bundle half each side then encapsulate the coil bundle and bond the two halves with a thin coat of epoxy, sand the form then apply the shield medium.

Alex, no I have never bothered changing the damping resistors in the SD2000M to get the best out of the SD2000 you need to have different frequencies mine has 12 crystal locked channels or  micro controlled variable frequency control I did go to the trouble to put variable damping in my GP3500 but hardly ever changed it once set up although nowadays I use the QED in preference to my minelab machines because of its convenience and light weight.

Formers below.

Regards, Ian. ::62::

Hi Ian,

Thanks for sharing.
Those formers are looking good.

I happened to be searching the net for Litz wire last night and came across some Russian sites with a number of photos related to spider coils just like we are talking about.
I didn't translate but the builds are related to Surf Pi and another East Europe  Pi.
Interesting. So like Aziz says, it's not a new idea.

Too hot in the workshop this last week and this next week will be a scorcher again here in SA.
I went to move some large sheets if 3mm aluminium that were sitting on the Cnc router, they were $&&@ hot like 58 deg hot!...I left them there lol..
So I'm not getting much work done..

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 22 2018 00:39:10 AEDT AM
Hi all,

I am aware of the coil to shielding capacitance. I'll provide you soon a nice Excel sheet to estimate/calculate the shielding capacitance of the coil. This is not a big deal. But I have to measure the permittivity of my EPS and XPS sheets and check the calculation with real coils built and measured their shielding capacitance.

Be patient please. I don't have much time during the week ends.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Monday January 22 2018 16:40:35 AEDT PM
Hi all,

I wound a trial coil on the HIPS former starting at 350 mm Diam. 35 turns of insulated 7/.16 tinned wire result 988 UH 5.26 ohms so in the ball park though I will not be using this in finished designs it was just what I had lying around until my Litz wire arrives.

Cool here today only 32 degrees C.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday January 22 2018 19:14:50 AEDT PM
  
Hi all,

I wound a trial coil on the HIPS former starting at 350 mm Diam. 35 turns of insulated 7/.16 tinned wire result 988 UH 5.26 ohms so in the ball park though I will not be using this in finished designs it was just what I had lying around until my Litz wire arrives.

Cool here today only 32 degrees C.

Regards, Ian. ::62::

Hi Ian,

I would be interested in the shielding capacitance. This part is going to be the biggest part besides the coil cable capacitance.
A provisionally measurement using Al-foil or graphite paper on both sides with appropriate EPS/XPS shielding spacer could be done quickly.

My first RX coil with single strand ribbon cable AWG28 with Ri=49 mm, Ro=99 mm, N=60, L=580 µH (calculated) with 2x 5mm XPS shielding spacer has a  shielding capacitance of 122 pF.  ::406::
I think, the insulation of the coil wire contributes a big portion to the capacitance.

Now preparing the second RX coil using enamelled copper wire this time.

We have to reduce the inductance, if we can not achive the required SRF. And hope, that the RX gain compensation can be fully made in the RX gain setting of the detector.

I have made dielectric constant measurements of my EPS and XPS sheets by making a large parallel plate capacitor.
EPS: 1.106
XPS: 1.142
Oh well, my capacitance meter could be quite inaccurate.

Oh yes, it's cool here too: only 1 degree C.  It snowed. Brrrrrrrrrr ::419::
 ::419::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday January 23 2018 10:34:55 AEDT AM
Hi all,

Here are some dielectric constants of a few  plastics, and timber, all averaged from different suppliers and given @1 MHz.

not all manufactures give data @1 to 2 Khz so did not include.



Air 1,
Foamed Polyethylene 1.5 - 2.1
Foamed PVC 1.56
Teflon 2.03
Polyethylene 2.27 - 2.5
Polypropylene   2.25
Nylon   4.0 - 4.6
PVC   3.8 - 8.0
Balsa wood 1.22
Unsealed  MDF 2.8 - 4.5
Pine  1.5 - 4.5 (depends on grain and moisture content numbers given are from 5 to 30% MC)

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday January 23 2018 11:47:26 AEDT AM
  
Hi all,

I wound a trial coil on the HIPS former starting at 350 mm Diam. 35 turns of insulated 7/.16 tinned wire result 988 UH 5.26 ohms so in the ball park though I will not be using this in finished designs it was just what I had lying around until my Litz wire arrives.

Cool here today only 32 degrees C.

Regards, Ian. ::62::

Hi Ian,

Nice work, thanks for sharing, interesting results.
What sort of weight is your coil/former looking like?

Yeah, nice here to day but I'm back at work...typical lol

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 23 2018 19:41:44 AEDT PM
Hi all,

I have ripped my XPS sheet coil former during tighting the coil wire during winding the RX coil. Cutting the notches was not a good idea and it takes so much time to do them either. I have wound the RX coil without the notches this time and it is easier and faster to do it.
More info later how I wound the RX coil.
 ::419::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 24 2018 09:59:32 AEDT AM
Hi all,

I have good news for you:
I have successfully wound/weaved a spider web coil on a 5 mm XPS sheet using 0.4 mm enamelled copper wire.
It should work with 0.3 mm enamelled copper wire or Litz wire even better.

The winding technique requires only one coil former so the TX coil could be wound on the same XPS coil former. But this is another story to figure out and optimize the winding process. The TX wire is thick and should be quite flexible like Litz wire to get it working. I don't have such a wire at home at the moment.

And I'm not happy with my capacitance meter. It isn't accurate enough at the lower end of the measurement range. So I have to build something, which makes me more accurate measurements possible. Anyway.

I'll show you the new RX coil and how to wind it soon.
 ::10 ::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 24 2018 21:01:51 AEDT PM
Hi all,

this is my new RX coil on 5 mm XPS sheet with 9 slots. Just for measurements.
Wire: 0.4 mm diameter enamelled copper wire
Wire length: 37.6 m,
Slot width = 4 mm,
RI = 51 mm,
RO = 114 mm,
Number of turns: 2x36 = 72
L = 887 µH (calculated)
R = 5.3 Ohm

I start with two winding loops. Stick the 2 mm width XPS strips into the slots and cut them. After pushing the XPS pieces as distance spacer, I wind the two next loops until the coil finishes. Due to the tension of the wire during the winding, the 2 mm XPS stripes get clinched a bit so I have less than 2 mm distance spacer.
Average distance between loops: (114 mm - 51 mm)/(36-1) = 1.8 mm.
This method works really fine.
Below are the steps.
 ::419::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 24 2018 21:03:23 AEDT PM
to be continued..


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 24 2018 21:08:49 AEDT PM
This is my first RX coil for measurements.


Title: Re: The need for big deep gold detectors.
Post by: Doug on Wednesday January 24 2018 21:58:41 AEDT PM
 Nice work Aziz! ::62::
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday January 24 2018 22:14:46 AEDT PM
  
Nice work Aziz! ::62::
doug ::419::

Thanks Doug.

The shielding capacitance is the next issue.  
::406::  ::406::  ::406::

Shielding capacitance measurement of the new RX coil:
Shielding capacitance with 2 x 5 mm XPS shielding spacer: 151 pF (too much!)
Shielding capacitance with 2 x 10 mm EPS shielding spacer: 84 pF (could be too much)
The interwire capacitance is quite low for sure. But I can not measure it at the moment.
The capacitance reading is not accurate enough.

If we can not reduce the parasitic capacitances, we have to lower the coil inductance.
A trial & error method.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday January 25 2018 00:04:20 AEDT AM
Hi all,

we have to save some parasitic capacitance.
I'll try a cheap and easy custom made RX coil cable and let's look, how much capacitance we can save.
3 m coil cable should be long enough.
 ::10 ::
We have to figure out the ball park for the RX coil inductance. Maybe a SRF of 400 - 500 kHz (below 500 kHz) could also work. There was one coil in the coil measurements table (the SEF coil), which had SRF of below 400 kHz.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 25 2018 00:19:44 AEDT AM
  
Hi all,

we have to save some parasitic capacitance.
I'll try a cheap and easy custom made RX coil cable and let's look, how much capacitance we can save.
3 m coil cable should be long enough.
 ::10 ::
We have to figure out the ball park for the RX coil inductance. Maybe a SRF of 400 - 500 kHz (below 500 kHz) could also work. There was one coil in the coil measurements table (the SEF coil), which had SRF of below 400 kHz.

Cheers,
Aziz


Great work Aziz!
Thanks for posting
I will complete my version of the former and windings using 6mm Foamed PVC with same spacing and turns then measure. I'll post results and pics when done.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: autitch on Thursday January 25 2018 09:24:09 AEDT AM
Hi Aziz & the brains trust,
Aziz Thanks for posting the pic with the spider coil winding and the capacitance figures using different shielding spacers.  The way I look at the coil optimal design we are ultimately capacitance limited not inductance limited.  I’ve produced a table using Ian’s measured existing DD coil parameters and it struck me that a reasonably low capacitance can be achieved for a given RX coil.  If you take a look at the table the Coilteck 430 x  280 DD  coil  for a RX Inductance of 542uH and SRF of 570 kHz by calculation this RX coil has a capacitance of 148 pF.  It can also be seen that the SAF21” x 17” RX coil has a comparatively poor SRF and high capacitance of 480 pF.  Your measured Capacitance of 84pF for 2x10 EPS shielding spacer in encouraging.  If Coiltek have been able to produce a coil with a relatively low capacitance I would suggest that a little reverse engineering might be in order to determine how they have been able to do achieve the low capacitance.

By my calculations Aziz for the coil you have wound, to achieve a SRF of 500kHz you need to limit the capacitance to 114pF so if you are able to limit the cable capacitance to 30pF you have achieved the goal of a high inductance RX coil with a in spec SRF of 500kHz.  I feel that you are within reach of the goal.

Furthermore if a RX capacitance of 148 pF is achievable & for a SRF of 500kHz we could realise a coil with 685 uH which is a lot better than any of the coils measure to date.
 
I was wondering what LCR meters people are using to take their measurements.  There aren’t too many meters that I’ve seen capable of measuring the small inductance, capacitance and resistance that we are playing with.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday January 25 2018 11:40:14 AEDT AM
  
Hi Aziz & the brains trust,
Aziz Thanks for posting the pic with the spider coil winding and the capacitance figures using different shielding spacers.  The way I look at the coil optimal design we are ultimately capacitance limited not inductance limited.  I’ve produced a table using Ian’s measured existing DD coil parameters and it struck me that a reasonably low capacitance can be achieved for a given RX coil.  If you take a look at the table the Coilteck 430 x  280 DD  coil  for a RX Inductance of 542uH and SRF of 570 kHz by calculation this RX coil has a capacitance of 148 pF.  It can also be seen that the SAF21” x 17” RX coil has a comparatively poor SRF and high capacitance of 480 pF.  Your measured Capacitance of 84pF for 2x10 EPS shielding spacer in encouraging.  If Coiltek have been able to produce a coil with a relatively low capacitance I would suggest that a little reverse engineering might be in order to determine how they have been able to do achieve the low capacitance.

By my calculations Aziz for the coil you have wound, to achieve a SRF of 500kHz you need to limit the capacitance to 114pF so if you are able to limit the cable capacitance to 30pF you have achieved the goal of a high inductance RX coil with a in spec SRF of 500kHz.  I feel that you are within reach of the goal.

Furthermore if a RX capacitance of 148 pF is achievable & for a SRF of 500kHz we could realise a coil with 685 uH which is a lot better than any of the coils measure to date.
 
I was wondering what LCR meters people are using to take their measurements.  There aren’t too many meters that I’ve seen capable of measuring the small inductance, capacitance and resistance that we are playing with.

AuTitch

Hi AuTitch,

yes, you are correct.  ::419::

We are in the ball park of 600 - 700 µH for the RX coil, which is easily feasible, when we use the best available low capacitance coax cable. Note, that the interwire coil capacitance has not been measured yet. I have estimated it comparing with the Gary's Spiral coil in my calculation below. 20 pF is by far a good estimation. I think, we will achieve lower than 16 pF.

I suggest, that we don't make the RX coil size too small relative to the TX coil size. I'm sure we can even go below 500 kHz SRF. Something in the region of 450 kHz to 500 kHz would be very likely ok.
 ::419::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 25 2018 16:08:52 AEDT PM
  

I was wondering what LCR meters people are using to take their measurements.  There aren’t too many meters that I’ve seen capable of measuring the small inductance, capacitance and resistance that we are playing with.

I have Agilent U1733C and looking at a spare unit from Enoma called a Lutron LCR-9183 which for $157 + GST isn't too bad.
Also had a few cheap Chinese rip-offs just to compare but they are not for me.....

The Agilent was around $800-$900 from memory

With the cheapy ($20 type) you get what you pay for...5-10% accuracy at best..if you are lucky but probably ok for poking around.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 25 2018 16:15:48 AEDT PM
  


 20 pF is by far a good estimation. I think, we will achieve lower than 16 pF.

I suggest, that we don't make the RX coil size too small relative to the TX coil size. I'm sure we can even go below 500 kHz SRF. Something in the region of 450 kHz to 500 kHz would be very likely ok.


Hi Aziz,

Thanks for your table.

I think this is very feasible.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: autitch on Thursday January 25 2018 16:31:37 AEDT PM
Thanks Muntari,

The Lutron LCR-9183 looks ok.  Just wondering if one can measure the small resistance values required for a typical TX coil winding accurately or would you use a Wheatstone bridge circuit.

AuTitch

  
  

I was wondering what LCR meters people are using to take their measurements.  There aren’t too many meters that I’ve seen capable of measuring the small inductance, capacitance and resistance that we are playing with.

I have Agilent U1733C and looking at a spare unit from Enoma called a Lutron LCR-9183 which for $157 + GST isn't too bad.
Also had a few cheap Chinese rip-offs just to compare but they are not for me.....

The Agilent was around $800-$900 from memory

With the cheapy ($20 type) you get what you pay for...5-10% accuracy at best..if you are lucky but probably ok for poking around.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 25 2018 17:08:44 AEDT PM
  

The Lutron LCR-9183 looks ok.  Just wondering if one can measure the small resistance values required for a typical TX coil winding accurately or would you use a Wheatstone bridge circuit.

Hi AuTitch,

With the Agilent, it will not be a problem, other I have tried results varied.
My U1733C is away for annual calibration checks hence the reason for looking at another unit, else I would post some pics and results.

The Lutron looks to be the goods so should also be Ok like a fair number of other s out there, beware the cheapies, they wander all over the place and I would not trust them for serious work.

I will have my Agilent back in a couple of weeks.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 25 2018 21:55:13 AEDT PM
Hi Aziz,

As a matter of interest, roughly how long did it take you to wind that coil?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Thursday January 25 2018 23:21:49 AEDT PM
  

With the Agilent, it will not be a problem, other I have tried results varied.


In principle modern, microprocessor controlled LCR meter incorporating good self-correction
algorithm and self-calibration, should be better option than old hi-tech instruments.

The Lutron LCR-9183 is good look, I have alike LCR meter named DER EE DE-5000.

Here some comparative results with my different LCR meters based on inductance measurement
using one PI coil as test sample:


1. Let start with simple, cheap, but accurate enough for detector homebuilders LC-meter model VC6243+:

f=2.5kHz, L=222uH


2. Next was LC-meter with generic name L/C METER (instrument has no fixed frequency - it is adapted by uC to inductor properties):

f=271kHz, L=280uH


3. By uC controlled (and this way adapted working frequency to specification part tested)
 is Peak ATLAS LCR40 too:

f=200kHz, L=252uH, DCR=3,4E



4. LCR meter model 4070L is working at fixed frequency:

f=100Hz, L=280uH, R=4E



5. What to say about next "crazy meter" (mean that user become crazy using it). OK maybe it was something like interference with mains grid frequency, at those low working frequency, I don't know - I am using power supply (genuine), cause inner accu go dead. Deviations are smaller in case of regular "bundle" wound coil than in "basket" wound. This instrument offer to user himself, to change among four working frequencies. It is named TH 2821A LCR METER:

f=100Hz, L=123mH, R=3.3E, Z=3.3E, Q=0.043
f=120Hz, L=85mH, R=3.3E, Z=3.3E, Q=0.05
f=1kHz, L=1461uH, R=3.9E, Z=3.6E, Q=0.43
f=10kHz, L=242uH, R=65E, Z=14.8E, Q=4.3



6. Next tested LCR meter allow measurement at five working frequencies. Good design a lot of measurement parameters and most accurate from LCR-meters taken in test (and most expensive too).
It is about DER EE LCR METER DE-5000:

f=100Hz, L=230uH, Rs=3.35E, DCR=3.36E, Q=0.043
f=120Hz, L=230uH, Rs=3.35E, DCR=3.36E, Q=0.05
f=1kHz, L=230uH, Rs=3.36E, DCR=3.36E, Q=0.43
f=10kHz, L=230uH, Rs=3.36E, DCR=3.36E, Q=4.3
f=100kHz, L=234uH, Rs=3.90E, DCR=3.36E, Q=38



7. LCR-T4-ESR

L=0.21mH (210uH), R=3.6E (no check about measurement frequency yet).


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 26 2018 00:46:57 AEDT AM
Hi WM6,

Your measurements with different LCR meters is kind of what I was referring to, the readings tend to be reasonable but too variable across units at the lower $ end, it's hard to know which one to trust but as you say, for general use not really a big concern.

The Agilent is one of the newest handhelds  from that company..actually someone else produces them now but  great quality and I am very comfortable with results.

The DER 5000 looks like a good unit too. Very similar

apologies for being off topic a little bit but  we do need them for coil work I think..

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 26 2018 01:35:00 AEDT AM
  
Hi Aziz,

As a matter of interest, roughly how long did it take you to wind that coil?

Cheers
Muntari

Hi Muntari,

2-3 hours (including the coil former). Once you have some practice, 2 hours or shorter.
It is quite easy to do. And it is quite cheap as well.
Use 0.3 mm diameter enamelled copper wire for best & cheap results.
 ::419::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 26 2018 01:45:49 AEDT AM
Hi all,

I wish, I had an LCR-Meter. The cheap one are quite inaccurate. The other one are too expensive.
I model the coil in my software and let it calculate to get the inductance. It is more accurate than the most LCR-Meters out there.
 ::620::
Oh yes, I'm also using the VA-Visual Analyzer software (sound-card based measurement, http://www.sillanumsoft.org/ ).
Aziz


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Friday January 26 2018 02:15:36 AEDT AM
  

Oh yes, I'm also using the VA-Visual Analyzer software (sound-card based measurement, http://www.sillanumsoft.org/ ).


This is interesting piece of software art.
I wish to check it but not sure, if it can work proper under my Linux.

This feature of ZRLC meter looks Especially interesting:

You can measure :
    All the previous parameters at different frequencies, and with automatic sweep, in time and frequency domain

http://www.sillanumsoft.org/ZRLC.htm (http://www.sillanumsoft.org/ZRLC.htm)


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 26 2018 09:30:26 AEDT AM
  
  
Hi Aziz,

As a matter of interest, roughly how long did it take you to wind that coil?

Cheers
Muntari

Hi Muntari,

2-3 hours (including the coil former). Once you have some practice, 2 hours or shorter.
It is quite easy to do. And it is quite cheap as well.
Use 0.3 mm diameter enamelled copper wire for best & cheap results.
 ::419::
Aziz

Hi Aziz,

Thanks for the info, it's good to know.
Looks like good therapy ????

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Friday January 26 2018 16:48:04 AEDT PM
Hi all, 

I have received my Litz and have stripped my tinned wire wind I only have enough wire for two coils so want to get it close fist time so what have we decided for the inductance should it be 650 uh- 700 if so I will try for 750 uh as it is easy to remove a few strands to lower it I have started the wind using Aziz's method but 3 mm spacing I will complete the wind when I get you confirmation on required inductance I have three LCR meters a Trio a home built LC one and a Japanese one all very close in measurement.

Regards, Ian. ::62::


 


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 26 2018 21:31:55 AEDT PM
  
Hi all, 

I have received my Litz and have stripped my tinned wire wind I only have enough wire for two coils so want to get it close fist time so what have we decided for the inductance should it be 650 uh- 700 if so I will try for 750 uh as it is easy to remove a few strands to lower it I have started the wind using Aziz's method but 3 mm spacing I will complete the wind when I get you confirmation on required inductance I have three LCR meters a Trio a home built LC one and a Japanese one all very close in measurement.

Regards, Ian. ::62::

Hi Ian,

please remember, that the smaller the RX coil size in relation to the TX coil size, the more RX gain compensation we need. The more RX gain setting in the detector is required and the more detector amplifier noise we get. To reduce the required amplifier gain (detector amplifier) a bit, we would need more RX coil inductance. And we have seen, that we are quite limitted in RX coil inductance due to parasitic RX coil capacitances.

The easy and safe way is as follows:
Make the RX coil size large: RX/TX coil size: 0.7 .. 0.8  (mean diameter relations). This way, we can start with low RX coil inductances.
600 µH is a good value to start with. We have to figure out yet, whether the detectors gain setting is enough to compensate for RX gain.

When this coil works, we can still increase the inductance upto 700 µH or more. Or decrease the RX coil size a bit.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday January 26 2018 22:32:42 AEDT PM
Hi all,

I have a good idea, how to easy realise a custom made shielded RX coil cable with low cable capacitance (< 20 pF/m).
Coil cable impedance Z0 approx. 200 Ohm or above.
Rdc = 1.7 to 2 Ohm for 3 m cable
C < 18 pF/m (I hope, I can realise it)

I'll use 0.2 mm diameter enamelled copper wire (inner wire), XPS stripes, spiral wrap tubing (PE material), graphite coated paper stripes, silver plated 0.4 mm diameter drain wire (outer wire), insulating tape
The RX coil cable is getting thick however (8 mm - 10 mm).

I'll try the idea and will show you how I made it next week. I don't have much time during the week ends.
 ::10 ::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Sunday January 28 2018 16:18:18 AEDT PM
Oh well start again time the 5/38 Litz is no good too much resistance could only achieve 535 uh and 18.32 ohms resistance with 3 mm wire spacing  so back to the drawing board and look for some better Litz.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday January 28 2018 19:09:54 AEDT PM
  
Oh well start again time the 5/38 Litz is no good too much resistance could only achieve 535 uh and 18.32 ohms resistance with 3 mm wire spacing  so back to the drawing board and look for some better Litz.

Regards, Ian. ::62::

Hi Ian,

no problem at all. Take 2 mm distance spacer for the windings, start with Ri 1-2 cm wider and add some wire tension during the winding, so the winding distance spacer gets below 2 mm.

18 Ohms could still be tolerable.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday January 28 2018 19:16:20 AEDT PM
Hi all,

I have been using the Visual Analyzer for coil measurements again. No good! It is totally inaccurate.
I have tried other software. No good!
No good programmers out there!
 ::35::
I could implement the software by myself using the lock-in amplifier for the measurements.
I could very likely measure very low inductances, resistances and capacitances. And much more accurate too.
This seems to be the best option for me.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday January 30 2018 16:57:21 AEDT PM
  
  



6. Next tested LCR meter allow measurement at five working frequencies. Good design a lot of measurement parameters and most accurate from LCR-meters taken in test (and most expensive too).
It is about DER EE LCR METER DE-5000:

f=100Hz, L=230uH, Rs=3.35E, DCR=3.36E, Q=0.043
f=120Hz, L=230uH, Rs=3.35E, DCR=3.36E, Q=0.05
f=1kHz, L=230uH, Rs=3.36E, DCR=3.36E, Q=0.43
f=10kHz, L=230uH, Rs=3.36E, DCR=3.36E, Q=4.3
f=100kHz, L=234uH, Rs=3.90E, DCR=3.36E, Q=38



7. LCR-T4-ESR

L=0.21mH (210uH), R=3.6E (no check about measurement frequency yet).


Hi WM6,

With my Agilent away for checks, I was looking at Lutron for a spare meter but after researching a bit more and seeing a great price on fleebay, I went with the same meter DE-5000..it will probably get here about the same time my Agilent comes home but at least I have a spare for next time...

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday January 30 2018 22:04:15 AEDT PM
Hi all,

the DER EE LCR METER DE-5000 seems to be ok for the affordable price.

But I don't need to buy an LCR meter now. I can code it by myself and correct.
(unlike most programmers out there ::37:: )

::37:: https://meettechniek.info/passive/inductance.html
There are some bugs in the formulas! ::37:: Garbage!

 ::05:: http://download.tek.com/document/75W_28152_1.pdf
Good and simple formulas, which are correct!

The Lock-in amplifiers are perfectly destined to make sound card LCR measurements. I have tested the formulas in Excel sheet and I have to code the software now.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday January 31 2018 07:56:21 AEDT AM
Hi Muntari

it is fair price for DE-5000 on eBay now (US $98.54).
I spend about US $230.00 on it, more than year ago.


Interested in Aziz idea final solution and its accuracy.


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Wednesday January 31 2018 16:17:45 AEDT PM
I may buy a DE-5000, but how do we know thats its accurate ?


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Wednesday January 31 2018 16:23:48 AEDT PM
  
I may buy a DE-5000, but how do we know thats its accurate ?

Send it away for calibration .. but it will cost you  ...


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday January 31 2018 21:45:37 AEDT PM
  
  
I may buy a DE-5000, but how do we know thats its accurate ?

Send it away for calibration .. but it will cost you  ...

It is easy, you should buy etalon check instrument of 0.05% basic accuracy, like this

https://www.zhinst.com/products/mfia?gclid=CjwKCAiA78XTBRBiEiwAGv7EKroOg7wdPSffS7GdYV7nvFQZZxllge8flBTlJbUfGKkGfhkXqRZ7BxoCiMcQAvD_BwE# (https://www.zhinst.com/products/mfia?gclid=CjwKCAiA78XTBRBiEiwAGv7EKroOg7wdPSffS7GdYV7nvFQZZxllge8flBTlJbUfGKkGfhkXqRZ7BxoCiMcQAvD_BwE#)

and compare results (but probably price first).


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday February 1 2018 08:16:19 AEDT AM
Found the English manual
http://akizukidenshi.com/download/ds/deree/DE-5000_manu_en2p.pdf


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Thursday February 1 2018 11:00:52 AEDT AM
Probably this combination of LCR meter with True RMS multimeter is even (economically) better solution for our needs:

DE-5004

https://www.ebay.com/itm/1x-DMM-LCR-Digital-Multimeter-Meter-Trur-RMS-DE-5004-6000-Count-DER-EE-DE-5000-/141821131870 (https://www.ebay.com/itm/1x-DMM-LCR-Digital-Multimeter-Meter-Trur-RMS-DE-5004-6000-Count-DER-EE-DE-5000-/141821131870)


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday February 1 2018 11:39:04 AEDT AM
Maybe a 3d printer Experiment

(https://s14.postimg.org/dykh4e869/7inch_coil.jpg)


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 1 2018 16:33:02 AEDT PM
  
Maybe a 3d printer Experiment

(https://s14.postimg.org/dykh4e869/7inch_coil.jpg)

Interesting you say that 6666,

I have been working on designs for both 3D print and CNC cutting forms.

At the risk of trolls, here is the draft pics of what I have done and the idea behind it.
This is of coarse for everyone to use but not profit from..so copyright

Foamed PVC 6 mm will be the material Dielectric constant of around 1.56 - 2.1  but with machining probably lot less.
This is good given the practicalities of real world builds

Instead of the usual spider cuts into 7 or 9 sections a spiral path is cut into the material and each section's depth along that path is machined to alternating high and low cuts.
The wire is a press fit into the slot. In this way the wire is layed the same profile as a standard Spider wind.
The advantages are that you can use less turns for same inductance but with the advantage of a standard spiral wound (arcs instead of straight lines in each section).
I am machining a couple first then slicing for 3D printing later.
The final cuts are not shown but have angled smooth tapers into slots to avoid sharp edges

The wire is held in the slots by the pressure fit and by using TechBond 263 hot glue sticks...low Dielectric constant high temp use (~105 deg C).

Will share more photos later when measurements are done.

Yes and I get that not everyone will have a CNC or 3D printer but I'm just showing some of my thinking and methods used with the MPI coil stacks...

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 1 2018 17:00:36 AEDT PM
  
I may buy a DE-5000, but how do we know thats its accurate ?

Hi 6666,

Check against a known calibrated unit, have high accuracy L,C,R standards in the workshop.

Failing that check against what reviews are saying  ::62::

Ill check mine against the Agilent when it comes home.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 2 2018 00:04:25 AEDT AM
Hi All,

Here is a close up of the coil former slot draft or fillets to prevent sharp bending of the wire.

You can clearly see the wire slots and how they alternate on height.
Shallow wire slot = 1mm, Deep wire slot = 5mm, slot width = 1mm
Design is parametric so all dimensions are on a spreadsheet and can be changed to suit coil size and material thickness without having to re-draw design every time coil or wire size is changed, takes longer to do first up but once done is repeatable and easily changed.
The drawing changes automatically..saves a lot of work.

Post more soon.

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 2 2018 14:43:23 AEDT PM
Hi All,

Just to add to last post.

Once I have completed a few prototype coils, I will show a method of producing the coil form using a Dremmel and a jig, you will not need a CNC or 3D printer to produce these formers.

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Friday February 2 2018 16:13:18 AEDT PM
Hi all,

I ended up making my own wire out of 2 strands of 0.2 mm enameled wire twisted at 12 turns per 25 mm worked well with the former 8 mm thick and turns spacing of 2 mm 30 turns gives me 714 uh and 9.27 ohms well with in the parameters if it turns out to high in inductance I can remove turns but will start with this for a first test.

Muntari looking good.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday February 2 2018 19:31:21 AEDT PM
Hi all,

thanks for contributing to the thread.
I'm impressed with Muntari's coil former designs.

I'm looking forward to the test results from Ian's coil.

Pity, but I had not much time to continue. I hope next week it will be better.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 2 2018 21:20:14 AEDT PM
  
Hi all,

I ended up making my own wire out of 2 strands of 0.2 mm enameled wire twisted at 12 turns per 25 mm worked well with the former 8 mm thick and turns spacing of 2 mm 30 turns gives me 714 uh and 9.27 ohms well with in the parameters if it turns out to high in inductance I can remove turns but will start with this for a first test.

Muntari looking good.

Regards, Ian. ::62::

Hi Ian,

That's great work and it will interesting to see the test results.
I'm using Teflon insulated wire to compare against plain magnet wire.

Your input is much appreciated as we need to chip away at the job and every bit we do will peak someone else's interest and hopefully spur things along with Aziz guiding.

Like Aziz says, there is a lot of work to be done but we have time ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 2 2018 21:26:59 AEDT PM
  
Hi all,

thanks for contributing to the thread.
I'm impressed with Muntari's coil former designs.

I'm looking forward to the test results from Ian's coil.

Pity, but I had not much time to continue. I hope next week it will be better.
Cheers,
Aziz

Hi Aziz,

Thanks and thanks for coming back to the forum and  for starting this thread, it has rekindled my enthusiasm and compelled me to bring to the table,  my ideas from the MPI but in a new way.

I'm very confident in your approach to this project so keep up the good work..oh and keep crunching the numbers ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 2 2018 21:45:58 AEDT PM
Hi All,

BTW for the record, I have made a spiral former with 2 mirrored parts with the idea of pressing a spiral coil into the shape of a spider coil (vertically spaced wires)
but it tended to shear the winding and stretch the copper...not so good for reliability.

So my advice is to forget that path  it did form the shape but way to much work.

This current idea is a modified version of my field proven MPI coil former but with Aziz's take on things.

Oh and before anyone asks, really sorry but I won't disclose the original MPI coil winding information, it would not be of use in a standard form detector in any case.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday February 2 2018 21:49:55 AEDT PM
“ Ill check mine against the Agilent when it comes home.
Cheers, Muntari “

Thanks I will be very interested to see how it tests !

“Here is a close up of the coil former slot “

Interesting deseign, when you get it made would it be possible for you to please take a photo with just a few turns of wire so we can see windings ?


“I will show a method of producing the coil form using a Dremmel “

Never thought of that, good suggestion


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 2 2018 21:59:42 AEDT PM
Hi 6666,

Yes for sure ..on all counts lol.

What with hot weather, full time job and grand kids  and trying to finish off some guitar amplifier parts  for a paying job...Its been hard to stay in the workshop.
I have been busy on tweaking the design and tool path is generated now so hopefully tomorrow is the day I can start re-cutting.

Yeah, on the Dremmel and jig, it will be a miniature version of a copy router basically.
Main difference is more control over the vertical pattern movement, it has to be accurate to within 0.2mm horizontally but that too is not as hard as it seems.. ill show at a later time but check out copy routers and you will figure it out.

Have you thought more on your square coil design btw, it looks interesting

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Doug on Saturday February 3 2018 12:32:14 AEDT PM
For new members and guests coming to this thread for the first time it might be useful if those involved in this project could perhaps explain:
What  are the aims and objectives of this coil project?
What are the expected benefits  to detector users  of the coils?
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Saturday February 3 2018 17:22:45 AEDT PM
Second prototype half wound on HDMI former expected to be mid 600's pictures to follow tomorrow.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday February 3 2018 19:05:33 AEDT PM
  
Second prototype half wound on HDMI former expected to be mid 600's pictures to follow tomorrow.

Regards, Ian. ::62::

Excellent Ian, look forward to seeing results.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday February 3 2018 19:15:14 AEDT PM
  
For new members and guests coming to this thread for the first time it might be useful if those involved in this project could perhaps explain:
What  are the aims and objectives of this coil project?
What are the expected benefits  to detector users  of the coils?
doug ::419::


Hi Doug,


I'll kick off and Aziz and others involved can modify..

To experiment with and to prove (or disprove) the advantages of a concentric co planer TX/RX coil suitable for deep seeking targets with existing PI detectors, in particular, starting with  the QED.
It is however, not limited to existing designs

Along the way showing different build options / methods and arriving at one or more optimum designs.


Benefits, -- deeper seeking, lower noise in mineralized ground and hopefully lighter weight coils as compared to similar existing mono coils of same size (18 - 19 inch)

I will add a little footnote...my thoughts are that Aziz is putting his ideas out there to get members / readers to think outside the square, if you can't improve the detector electronics because of patents, then what else can you do? I mean, if you follow what is the norm, nothing new will eventuate. We are mostly here in the tech area to learn and contribute to the art and hopefully, improve chances of finding pay dirt as a side benefit to this hobby.

Oh, and if you are a trolling manufacturer, then do the right thing if this project is successful and you copy, then produce and sell at reasonable prices and acknowledge the designers, this area is open to guests so a lot of people who might buy such a coil from you (should you copy)  and those who don't read the forums are well enough tech savvy to check out things before purchase.. google is a powerful tool these days..

As Aziz has said, this is NOT his original idea, co planar / concentric coils have been around for years but not necessarily in the way he is presenting. This is thinking outside the square...

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Doug on Sunday February 4 2018 13:07:18 AEDT PM
  

Hi Doug,

I'll kick off and Aziz and others involved can modify..
To experiment with and to prove (or disprove) the advantages of a concentric co planer TX/RX coil suitable for deep seeking targets with existing PI detectors, in particular, starting with  the QED.
Muntari

Having a detector like the QED with a simpler circuit and firmware that is very, very understood  i think is a major advantage compared to any other PI's some of which are not very coil parameter tolerant and their firmware is locked.
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Sunday February 4 2018 16:08:56 AEDT PM
I concur with Muntari's words above  and submit the pictures of my two prototypes as promised, they are now ready to have the XPF foam applied prior to shielding when I pick it up from IKEA when I am in Adelaide next.


Title: Re: The need for big deep gold detectors.
Post by: autitch on Sunday February 4 2018 19:03:54 AEDT PM
Nice work  Ian

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday February 4 2018 19:12:26 AEDT PM
  
I concur with Muntari's words above  and submit the pictures of my two prototypes as promised, they are now ready to have the XPF foam applied prior to shielding when I pick it up from IKEA when I am in Adelaide next.

Hi Ian,

Very nice work, looks great.
What is the weight of each coil assembly Ian?

As soon as it cools later, I'm firing up the Cnc and cutting a small sample of coil former.
will post photos when complete

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 5 2018 13:46:09 AEDT PM
Hi All,

Ok so I finally got back into the workshop last night and did some test cuts for design.

I didn't get to finish it as I was using a 1mm end mill which is meant for metal cutting so not great in plastic but I wanted to check the rigidity of side walls which are only 0.5mm
wide in this test piece.

When I cut this foamed PVC I would normally use a 6mm or larger diameter bit and it cuts really well but down at 1mm things change drastically.
I have ordered correct endmills and will  try again later.

The material like I said, is very rigid even with .5mm wall thickness so that is a good thing.

The 1st photo shows a couple of deep cuts on bottom right, rest are 1mm.
The swarf has not been cleaned from slots and I have to machine the remaining 5mm deep slots so I left the piece on the machine.

I'll play around with setting to get cleaner cuts of course but I'm happy the material is going to hold up to winding.
Second shot shows the size of jig. the router has a moving bed 2m x 3m and I usually position different jigs around on the  bed so I can have multiple job tooling / jigs set up without having to rip them off all the time..seems ridiculous machining something this small but it works for me.
As an aside, in its past life, this machine was a 2007 build  $300K  Tekwin banner UV printer, I scored it for $5k and modified it into the beast it is now.. ::62::

More later

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 5 2018 22:37:31 AEDT PM
Hi All,

Ironed out a few wrinkles and the machining part is looking like I wanted.

Ill post the completed former once its off the CNC and cleaned up a bit..

Then I'll put a few turns on and post a photo of that

Looks like my Agilent wont be back til late next week but that DE5000 has just cleared customs so hopefully I can get some L values later this week.

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: egixe4 on Tuesday February 6 2018 10:42:58 AEDT AM
I'm enjoying this thread, so thanks posters.
Looks like you guys have some nice toys hidden away in the shed.  ::402::
 


Title: Re: The need for big deep gold detectors.
Post by: Doug on Tuesday February 6 2018 14:52:09 AEDT PM
  
I'm enjoying this thread, so thanks posters.
Looks like you guys have some nice toys hidden away in the shed.  ::402::
 

A  forum member here has bought a new Pi detector to market, now lets hope that the coil boys here can bring some better coils to fruition!
Some very clever and dedicated members here! ::62::
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 6 2018 15:15:19 AEDT PM
Hi Doug,

Hmm, anymore info on that detector or are you referring to QED

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 6 2018 15:29:41 AEDT PM
  
I'm enjoying this thread, so thanks posters.
Looks like you guys have some nice toys hidden away in the shed.  ::402::
 

Hi Egixe4,

That's good to hear, that's what it's all about.
Yeah a few toys collected and hidden over the journey  ::62::

Cheers

Muntari




Title: Re: The need for big deep gold detectors.
Post by: Doug on Tuesday February 6 2018 15:30:33 AEDT PM
  
Hi Doug,

Hmm, anymore info on that detector or are you referring to QED

Cheers

Muntari

QED  ::62:: should have made it clearer ! ::75::
doug.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 6 2018 15:54:04 AEDT PM
Hi Doug,

All good, after reading again,  thought you might have been outlining to guests.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 6 2018 16:10:15 AEDT PM
Hi All,

My plan is to machine 4 blanks in order to wind 4 different configurations same size, same material, same wire

1) Like the last one posted
2) Single Spiral wound with same wire spacing and constant 2 mm depth
3) Double sided as above but with one side offset to the other, that is each wire sees a view of the ground
4) Standard bundle wound on edge of former, same outside diameter as 3 above.

I'll then compare parameters and post results.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday February 6 2018 16:23:10 AEDT PM
Hi Muntari,

To answer your question the XPS former including wire etc as pictured is 21.2 grams the HIPS former with wire etc is 33 grams now starting on the shells these will be fabricated as they are one off's not vacuum formed.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 6 2018 16:30:27 AEDT PM
  
Hi Muntari,

To answer your question the XPS former including wire etc as pictured is 21.2 grams the HIPS former with wire etc is 33 grams now starting on the shells these will be fabricated as they are one off's not vacuum formed.

Regards, Ian. ::62::

Hi Ian,

Thanks, that's pretty darn good.
Is that HIPS 3 mm or 6 mm?

Looking good!

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday February 6 2018 17:01:07 AEDT PM
Hi Muntari 3 mm.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Tuesday February 6 2018 19:33:30 AEDT PM
  
Hi All,

My plan is to machine 4 blanks in order to wind 4 different configurations same size, same material, same wire

1) Like the last one posted
2) Single Spiral wound with same wire spacing and constant 2 mm depth
3) Double sided as above but with one side offset to the other, that is each wire sees a view of the ground
4) Standard bundle wound on edge of former, same outside diameter as 3 above.

I'll then compare parameters and post results.

Cheers

Muntari

Watching with interest.
I have not done anything with the square coil idea yet, it was mainly to show the grooves in the formers and how it could be done on a 3d printer, which I am working on getting.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday February 6 2018 21:31:59 AEDT PM
Hi all,

I have implemented my own sound card LCR meter and it seems, that it works ok and more accurate. I have to test it thoroughly however.
Measuring low capacitances is critical and can't be done yet.
Parasitic coil capacitance does limit the measurement frequency and accuracy.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday February 6 2018 22:48:52 AEDT PM
Hi all,

Ok, low capacitance can also be measured quite accurately. I have tested it with a 1.5 m twisted pair cable.
Yeah!  ::10 ::

Open/short calibration could also be done to increase the measurement accuracy.
Well, I'll think of it.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 6 2018 23:44:29 AEDT PM
Hi All,

Here are a couple of photos of completed former and a couple of sample winds with 0.5 mm wire.

Easy as pie to wind, just need a butter knife as a guide, hold over wire, place in slot and rotate former and it presses into place just right..and snug.
The butter knife has perfect arc...great tool!


Ill do complete wind tomorrow night

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 6 2018 23:46:14 AEDT PM
  
[
Watching with interest.
I have not done anything with the square coil idea yet, it was mainly to show the grooves in the formers and how it could be done on a 3d printer, which I am working on getting.

Hi 6666,

I like the idea, you should follow it up for sure.
3D printing in the case of coil formers should be a reasonable fit as the required height is not extreme, they don't have to be perfect and there is a huge choice of filaments available in all sorts of material.
Actual print time might be quite fine.
I'll have a shot on mine at a later time but you should definitely try it out when you can

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 6 2018 23:47:46 AEDT PM
  
Hi all,

I have implemented my own sound card LCR meter and it seems, that it works ok and more accurate. I have to test it thoroughly however.
Measuring low capacitances is critical and can't be done yet.
Parasitic coil capacitance does limit the measurement frequency and accuracy.

Cheers,
Aziz


Hi Aziz,

Cool idea, I want to hear more...

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday February 7 2018 00:03:53 AEDT AM
Hi Muntari

Your "Butter knife coil" looks great.

Excellent design solution.


How do you plan to wind TX part?
Same way or maybe bundle wound?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 7 2018 00:20:08 AEDT AM
  
Hi Muntari

Your "Butter knife coil" looks great.

Excellent design solution.


How do you plan to wind TX part?
Same way or maybe bundle wound?

Hi WM6,

Thanks, still a ways to go, this is a proof of concept and I'll improve the ease of manufacture once we know required values etc.

There will be a number of things to try with TX, one of them a bundle winding the other spiral/spider.
I'm leaning towards a double sided spiral on the same sheet as RX.

If bundle wound then ill cut 2 donuts that over hang the outer edge of RX former and glued to top and bottom.....so it forms a bobbin and just wind around edge of RX.

Of course the former above would be made larger with those spokes longer...probably best if I draw it up  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Wednesday February 7 2018 04:03:46 AEDT AM
Looking good Muntari
I also forgot to mention that a prototype of that square coil could be made useing balsa wood and a small razor saw, useing more arms to make it more round, a lot of cuts with the saw though , would be very easy to do, get some 3mm MDF, cut the slots and glue down the arms , pad the wire with foam underneath to stop vibration, then glue down atop cover.   


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 7 2018 10:08:45 AEDT AM
Hi 6666,

Thanks, getting there, I'm looking forward to seeing results of Ian's coil once testing begins.
I'll make one  the same size as Ian's to compare but that will be after I've done making and comparing the 4 units at 200 mm.
Its not my intention to make coils this small but for proof of concept, and getting some tests underway, this size is fine.
If results are as expected, then I'll go straight up to the larger size, not sure what that will be yet , perhaps 400mm so any input would be appreciated on that.

Yes, Balsa wood is an interesting timber and great for prototyping.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 7 2018 10:11:32 AEDT AM
  
Hi Muntari 3 mm.

Regards, Ian. ::62::

Thanks Ian, it will be good to compare notes on the different builds, weight, size, L, C, R.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 7 2018 10:41:42 AEDT AM
Hi All,

Forgot to mention, the weight of the A4 sized sheet of Foamed PVC was 175 grams.

It was cut from a 1200 x 800 mm sheet purchased from Bunnings..cost about $30.

Phoned manufacture and distributors but prices were the same, no real discounts and a headache to deal with, so go to Bunnings ::62::

I have not weighed the finished former piece yet but I expect it will be around 25 to 30 something grams, add wire to that.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 7 2018 22:16:17 AEDT PM
Hi All,

Ok, so here are a couple of photos of completed winding.

Former 6 mm thick, OD = 190 mm,  ID = 100 mm , Shallow winding depth = 2 mm, Deep winding depth = 5 mm, wire spacing 1.8 mm

Wire used = 0.56 mm diam, turns = 22

Time to wind = 8 min   ( no jig just rotating flat on table using a butter knife to press into slots)

Inductance -- will measure tomorrow DE-5000 LCR meter has arrived gotta pick up from PO....
SRF --- will setup tomorrow and check along with other tests.

So easy to wind and no need to machine radial slots at depth cross over points, the butter knife radius and width guide the wire perfectly with no sharp bends.

More later


Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday February 7 2018 22:45:14 AEDT PM
Wow! What a nice coil and coil former!  ::05::
Well done Muntari.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 7 2018 23:26:18 AEDT PM
Hi Aziz,

Thanks, it turned out pretty good, just have to do some measurements and then make a few more variations and compare notes.

Are you able to or do you have time to model a layered spiral coil with your software?

I am thinking that for TX i would machine top and bottom spiral pattern  to 2 mm (its a good wire holding depth) but have windings offset horizontally by 1 turn width same inter-wire spacing (1.5 - 1,8 mm) so same number of turns top and bottom. It would be one winding but in 2 parts is my thinking (no solder)
The reason is to reduce the overall ID to OD horizontal winding space diam  as much amount possible but still be better than a bundle wound TX.

I'm curious to the vertical spacing effect on TX field pattern and ratios of LC. I can go build a former and just do the measurements but if I can get close to an optimum design I can tweak the former to suit.

I know it performs well in my gradiometer style coil but vertical spacing was >1/2 coil diam

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Thursday February 8 2018 09:15:05 AEDT AM
Well done Muntari. It's Wonderful.

https://youtu.be/QILaCLtWW9A (https://youtu.be/QILaCLtWW9A)


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 8 2018 11:40:36 AEDT AM
  
Well done Muntari. It's Wonderful.


Haha, thanks WM6, lets see how it measures against some other variations.

The DE-5000 arrived this morning Ill setup and do some measurements and post

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 8 2018 12:18:11 AEDT PM
Hi All,

I had a quick play with the DE-5000 LCR meter, checked a few standards I have and I'm pretty happy with it. Will check against Agilent later

Then checked inductance of coil, it reads 97uH

I was shooting for 100uH but had to allow space on material for hold downs while machining....but it was close

More later

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 8 2018 12:30:02 AEDT PM
Hi All,

I should add, what I'm doing is setting up to compare different winding forms as discussed earlier.

The numbers and size are arbitrary but will all be the same size and spacing, 200mm just happens to fit on an A4 sized sheet nicely.

I also need to add 2 more formers to the earlier list which is standard spider (straight wires between sections).

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday February 8 2018 12:55:59 AEDT PM
  
Hi All,

I had a quick play with the DE-5000 LCR meter, checked a few standards I have and I'm pretty happy with it. Will check against Agilent later

Then checked inductance of coil, it reads 97uH

I was shooting for 100uH but had to allow space on material for hold downs while machining....but it was close

More later

Cheers

Muntari

Thanks for showing us, so with the brief testing of your standards do you think its safe to order one ?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 8 2018 13:37:34 AEDT PM
  
  
Hi All,

I had a quick play with the DE-5000 LCR meter, checked a few standards I have and I'm pretty happy with it. Will check against Agilent later

Then checked inductance of coil, it reads 97uH

I was shooting for 100uH but had to allow space on material for hold downs while machining....but it was close

More later

Cheers

Muntari

Thanks for showing us, so with the brief testing of your standards do you think its safe to order one ?

Hi 6666,

Yes, absolutely, I'm confident you will not be disappointed.
 I went for one that had all extras from Trad Japan on Ebay total cost $218 but you can find them half that price but they don't have all probes/IR link etc.

I still don't have my Agilent back (which is not unusual this time of year) else I would post results against that.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday February 8 2018 16:21:32 AEDT PM
Thanks I've ordered one for about $120 with 2 probes,
without probes they are about $100,
now just got to sort out the 3d printer


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 8 2018 20:57:36 AEDT PM
  
Thanks I've ordered one for about $120 with 2 probes,
without probes they are about $100,
now just got to sort out the 3d printer

That's great news 6666. Pretty good deal for what you get an quality is quite good.

With 3D printer my advice is to steer clear of those cheap eBay jobs, they will cause nothing but grief and turn you off 3D printing very quickly.
The CR10 is the minimum I would recommend if you just want to get stuck into it without building and reworking Chinese rubbish.

I'm sure people out there have had success with some of the cheapies but it's more hit and miss

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday February 8 2018 22:38:10 AEDT PM
  
Hi Aziz,

..
Are you able to or do you have time to model a layered spiral coil with your software?
..
Cheers

Muntari

Hi Muntari,

sure, I can do it. You have to specify the coil geometry data and coil wire data as accurate as possible.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday February 8 2018 22:54:21 AEDT PM
Hi all,

I have developped my sound card LCR meter further and have played with some measurements.
I can measure up to 24 kHz test frequency using lockin-amplifiers.
Phase angle resolution measurements up to +/- 0.0005 degree (TC=10.7 ms). With higher lock-in time constants (TC) even more accurate.
FFT would allow measurements up to 48 kHz but I haven't implemented it.

One important issue with thin single strand wires for the RX coil:
Proximity and skin depth effect is quite measureable. The RX coils series resistor Rs becomes frequency dependent. This could degrade its performance considerable.
I think, we would require Litz wire for the RX coil.

I have to buy these Litz wires yet. And some more parts for the new PI detector platform.
And I am really thinking of buying an LCR meter.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday February 8 2018 23:16:59 AEDT PM
Quote
I think, we would require Litz wire for the RX coil.


Hi Aziz
would multistrand tin plated copper wire be ok ?
or does it have to be real Litz ?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 8 2018 23:39:56 AEDT PM
  
  
Hi Aziz,

..
Are you able to or do you have time to model a layered spiral coil with your software?
..
Cheers

Muntari
[/quote

Hi Muntari,

sure, I can do it. You have to specify the coil geometry data and coil wire data as accurate as possible.
Cheers,
Aziz

Hi Aziz,

Ok thank you, that's great. I can output most 3D or 2D vector file types and STL ,IGES, etc, let me know what type and I'll see if I can export.
I have to sit down and re work some things on the model so I'll cad up what I'm thinking and PM the file if you like. I'll have to machine the other  former variations first so might be a few days
Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday February 9 2018 00:00:25 AEDT AM
  
Quote
I think, we would require Litz wire for the RX coil.


Hi Aziz
would multistrand tin plated copper wire be ok ?
or does it have to be real Litz ?

Hi 6666,

I have a test RX coil here (my first RX coil prototype shown here):
Insulated wire with 5 tinned strands, total approx. 0.4 mm core wire diameter and approx. 1 mm diameter with insulation.
L = 580 µH (calculated)
Rs = 6.2 Ohm (calculated DC resistance)

Measured with a 10 Ohm reference resistor (1% tolerance & accuracy at the moment). Lock-in TC approx. 0.5 seconds.

Frequency[Hz]   Rs[Ohm]    L[µH]
93.75           6.087        588
750             6.108       592.2
1031.25     6.127       592.2
3000          6.440       591.7
6000         7.508       590
9000          9.25         587.1
15000        14.7        578
19875       21.0         568
24000       27.4         557.6

As we can see it, the series resistor Rs goes rapidly up on higher frequencies. It could affect the detector performance.
We have to try it out to be sure.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 00:04:38 AEDT AM
  
Hi all,

I have developped my sound card LCR meter further and have played with some measurements.
I can measure up to 24 kHz test frequency using lockin-amplifiers.
Phase angle resolution measurements up to +/- 0.0005 degree (TC=10.7 ms). With higher lock-in time constants (TC) even more accurate.
FFT would allow measurements up to 48 kHz but I haven't implemented it.

One important issue with thin single strand wires for the RX coil:
Proximity and skin depth effect is quite measureable. The RX coils series resistor Rs becomes frequency dependent. This could degrade its performance considerable.
I think, we would require Litz wire for the RX coil.

I have to buy these Litz wires yet. And some more parts for the new PI detector platform.
And I am really thinking of buying an LCR meter.
Cheers,
Aziz

Hi Aziz,
Thanks for sharing, you have been busy ::62::
Looks like I'll add another former to the list to cater for Litz wire, it's expensive stuff though but if the result is head and shoulders above the average, then it's worth it.

The De-5000 LCR meter is value for money , WM6 mentioned it and I purchased one also and I'm quite impressed so maybe take a look at that one.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday February 9 2018 00:20:38 AEDT AM
This is the second RX coil protoype shown here using a 0.4 mm enamelled copper wire.

L = 887.2 µH (calculated)
Rs = 5.32 Ohm (calculated DC resistance)

Measured with a 10 Ohm reference resistor (1% tolerance & accuracy at the moment). Lock-in TC approx. 0.5 seconds.

Frequency[Hz]   Rs[Ohm]    L[µH]
93.75           5.29        891.8
750             5.338       894.7
1031.25     5.383        894.6
3000          6.094        892.7
6000         8.489         886.7
9000          12.41        876.8
15000        24.38        847
19875       37.48         814.6
24000       50.35         782.8

Look: the single strand coil wire has significant more frequency dependent series resistor Rs.
 ::406::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 00:38:48 AEDT AM
  
This is the second RX coil protoype shown here using a 0.4 mm enamelled copper wire.

L = 887.2 µH (calculated)
Rs = 5.32 Ohm (calculated DC resistance)

Measured with a 10 Ohm reference resistor (1% tolerance & accuracy at the moment). Lock-in TC approx. 0.5 seconds.

Frequency[Hz]   Rs[Ohm]    L[µH]
93.75           5.29        891.8
750             5.338       894.7
1031.25     5.383        894.6
3000          6.094        892.7
6000         8.489         886.7
9000          12.41        876.8
15000        24.38        847
19875       37.48         814.6
24000       50.35         782.8

Look: the single strand coil wire has significant more frequency dependent series resistor Rs.
 ::406::
Cheers,
Aziz


Hi Aziz,

Thanks for that great info,
I have no doubt there is benefit in Litz wire but I'm wondering how much, I mean there is a trade off frequency where the cost / benefit ratio  becomes not economical so it would be good to know what point is . 2 to 3kHz perhaps?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday February 9 2018 00:51:42 AEDT AM
  
Hi Aziz,

Thanks for that great info,
I have no doubt there is benefit in Litz wire but I'm wondering how much, I mean there is a trade off frequency where the cost / benefit ratio  becomes not economical so it would be good to know what point is . 2 to 3kHz perhaps?

Cheers

Muntari

Hi Muntari,

pulse induction detectors are wide band response detectors. Minimum required band width is 50kHz - 100 kHz. Fast time constant target responses require more band width (500 kHz and up).
If the coil wire isn't a pure Litz wire, you simply reduce the detectors response band width significantly. In the early sampling times, you have a much higher non-linearity and the ground balance is affected.

There is no way. We have to use good Litz wires. Both for TX and RX coil.

I am even thinking of making my own Litz wires. With a simple DIY machine (motor controlled).
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 10:09:54 AEDT AM
  
  
Hi Aziz,

Thanks for that great info,
I have no doubt there is benefit in Litz wire but I'm wondering how much, I mean there is a trade off frequency where the cost / benefit ratio  becomes not economical so it would be good to know what point is . 2 to 3kHz perhaps?

Cheers

Muntari

Hi Muntari,

pulse induction detectors are wide band response detectors. Minimum required band width is 50kHz - 100 kHz. Fast time constant target responses require more band width (500 kHz and up).
If the coil wire isn't a pure Litz wire, you simply reduce the detectors response band width significantly. In the early sampling times, you have a much higher non-linearity and the ground balance is affected.

There is no way. We have to use good Litz wires. Both for TX and RX coil.

I am even thinking of making my own Litz wires. With a simple DIY machine (motor controlled).
Cheers,
Aziz

Hi Aziz, that's a typo on my part (posting late night is not good) was meant to be 20 - 30kHz  but yes, you are right, they are wide band response but I have built fast coils with single strand wire  <6usec but there is always the trade off, your front end has to be stable and quiet.

The point I was getting at I guess, was that at some point for the DIY, the cost of Litz wire versus real world benefit brings you close to the cost of a commercial coil unless you get creative as Ian and yourself have done and suggested.

I bow to your immense knowledge and I can see the benefit of Litz in the RX but I am not yet convinced it is required for the TX... and I'm talking real world builds with weight and size taken into account .
I have an open mind and have tried many, many different configurations over the years but I am still willing to learn more and try new things so I am happy to physically build any design you say works best. Like you, I think outside the square and ask lots of questions.. ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 10:13:23 AEDT AM

'I am even thinking of making my own Litz wires. With a simple DIY machine (motor controlled).'

Now you're talking, tell us more  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 11:06:33 AEDT AM
Hi all,

So to the benefits of Litz wire...

Reduces Skin Effect
Reduces Proximity Effect
Allows Use at High Frequencies
Increases Efficiency
Reduces Weight

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 11:30:08 AEDT AM
So the only thing I can see in that list that could be done with standard wire and the winding form design  alone is reducing proximity effect (basket weave, spider weave)

Other than that, Litz is heads and shoulder above other wires for coils

The problem I have with Litz wire is that in small amounts, it is expensive and not always easy to get a hold of.
If you have the time, sure you can make your own but unless its semi- automated or you have a lot of patience and well organised, you can end up with a rats nest.

I'm not being negative here but I'm not sure I want to be making my winding wire unless I can do it efficiently, if someone has done it, I would like to know roughly how long it takes to set up and wind, methods used and how well it actually performed.


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 12:29:57 AEDT PM
  

'I am even thinking of making my own Litz wires. With a simple DIY machine (motor controlled).'

Now you're talking, tell us more  ::62::

Cheers

Muntari

If I was to do it, then I would start with something like this.

Feed wires through holes of variable speed spindle from how ever many spools you have onto another motorized but geared spool holder.

The speed at which you turn each dictates the twist.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 12:46:43 AEDT PM
Yeah, right, I'm an idiot!

That won't work haha, the wires have to be guided first we dont want wire twisting both sides of spindle ...what was I thinking ...DOH

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: autitch on Friday February 9 2018 13:13:34 AEDT PM
The Litz wire availability in the correct gauge and resistance figures is a bit of a problem for sure.  I'm investigating having some made to order.  There are come Chinese manufactures that cater for small order runs but in the interim may need to make some up. 

Just a question for those that have experience making Litz wire how critical is the twist of the Litz wire.  Could a moderate twist count of say 1 twist in 50mm suffice say for a 44 strands of AWG33(0.18mm) or is a higher twist count preferable.

Muntari, I was also thinking of a similar cable twisting mechanism.  As you have identified to twist the individual strands you are going to need a multi hole single strand guide, a rotating guide (does the actual twisting) and then a series of single hole guides to neck down the twisting individual strands down to a single Litz wire before going the winding reel.

BTW if anyone is looking to purchase Litz wire from Woody I have personally measure the wire he is selling and on my gear it came out at 0.02049 ohms/m which for my coil design would produce a TX resistance of 0.51 ohms which is too far away from the recommended  0.4 ohms.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 13:52:45 AEDT PM
Hi Autitch,

Yes, I had a plan in my head then had a brain fade as I was drawing it.

I would  have the individual spools of raw wire on motor driven platter with spokes and guides for each spool then feeding into a single guide like you have said.
So 2 motors one to drive the twisting spools of wire the other the finished material spool which draws the wire through.

It is much easier but a little larger to do it this way rather than having the finishing spool rotating and twisting on 2 axis.
It would fit neatly on a standard bench.
Ill try cad a draft up and post.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: autitch on Friday February 9 2018 14:04:39 AEDT PM
Hi Muntari,

What you are proposing is a very elegant solution, semi production run type of setup.  I'm trying to think up of a way to do the twisting in one operation / setup 25m long (enough for 1 TX cable).  I'm thinking something that goes onto a drill perhaps with a means to swap the position of the individual strands on the drill fixture to alternate the position of the individual strands in the final Litz wire.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 14:28:39 AEDT PM
Hi Autitch,

Yep, I'm with you. Your idea would work, if you could shorten the distance by half with an idler wheel at the halfway mark, it would be more manageable, the idler would have to have an ID nice and convex and smooth. You could possibly double that again by adding another. food for thought.. Mast head rope pulley springs to mind

I would try it on a smaller 2 meter scale first to see how it twists.

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: autitch on Friday February 9 2018 15:12:58 AEDT PM
Hi Muntari,
This is what I was thinking of.  The yellow item is a PVC pipe end cad with radial holes 16 off diam to suit all thread. White are all thread with nuts and magenta is the central bolt that the battery drill spins. The green items are individual stands.  The idea here is to periodically move the all threads with the wire strands around  so to impart a layering and twisting.  The other end of the strands 25m away can just be mailed to a bench or piece of timber. The drill would impart the necessary twisting action and presto you have Litz wire.  ( I hope).


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 16:13:01 AEDT PM
Hi Autitch,

Excellent thinking, I like it very much! nice elegant solution.

I went for a more agricultural approach but I really do like yours.

Here's my spin (yeah bad pun) on it.

Back platter spins with small bobbins loaded and wire fed through slots in discs that progressively get smaller diameter until finally fed through single hole.
The other end is fixed to the rotating spool slowly drawing it through as back platter spins.


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Friday February 9 2018 16:25:58 AEDT PM
 ::62:: Hi all,

If you want to read up on the ultimate Litz for coils read Sean Goddard's  Post on ( Geotech http://www.geotech1.com/forums/showthread.php?23838-DIY-Mad-Litz-Wire-for-ULTRA-FAST-PI-Coils ) that is the way to make it.

As for making Litz wire Stefan and I have been hand making it for quite a few years and it takes quite some time and it is nowhere as involved as Sean's wire the strands need to be supported and evenly tension-ed at a minimum of 3 meter intervals and you need about a 30 meter length for an 18" plus coil the RX wires for the two prototypes that I wound I used over 40 meters each I started off at 49 meters it took me 6 hours to set up and wind the two wires and they have about 10 turns per inch or 25.4 mm one of two strands and one of three strands much different to winding TX wire that takes me a day to set up and wind a 30 meter length and I have all the jigs and supports made up I have seen a couple of homemade mechanized machines for winding Litz wire  I will see if I still have the links to them and will post if I can find them I started building one then decided as my other half decided I had built enough coils I should give it away and concentrate on getting out and use what I have but you have to use up the stuff you have you cant have it going to waste that's my excuse.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: autitch on Friday February 9 2018 16:33:17 AEDT PM
Muntari,
That’s very creative and would certainly wind a lice cable.   A couple of things pop out at me,
The bobbin plate will need to cater for at least 35 bobbins of 0.2 wire or 56 bobbins of 0.16 wire if you are going to spin the Litz in one go.
To protect the strands the slotted discs and the final plate will need to be made from some sort of plastic / PTEP UHMWPE to protect the enamelling.

Autitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 16:49:55 AEDT PM
  
::62:: Hi all,

If you want to read up on the ultimate Litz for coils read Sean Goddard's  Post on ( Geotech http://www.geotech1.com/forums/showthread.php?23838-DIY-Mad-Litz-Wire-for-ULTRA-FAST-PI-Coils ) that is the way to make it.

As for making Litz wire Stefan and I have been hand making it for quite a few years and it takes quite some time and it is nowhere as involved as Sean's wire the strands need to be supported and evenly tension-ed at a minimum of 3 meter intervals and you need about a 30 meter length for an 18" plus coil the RX wires for the two prototypes that I wound I used over 40 meters each I started off at 49 meters it took me 6 hours to set up and wind the two wires and they have about 10 turns per inch or 25.4 mm one of two strands and one of three strands much different to winding TX wire that takes me a day to set up and wind a 30 meter length and I have all the jigs and supports made up I have seen a couple of homemade mechanized machines for winding Litz wire  I will see if I still have the links to them and will post if I can find them I started building one then decided as my other half decided I had built enough coils I should give it away and concentrate on getting out and use what I have but you have to use up the stuff you have you cant have it going to waste that's my excuse.

Regards, Ian. ::62::

Hi Ian,

Thanks for the info, yes I have seen Sean's windings and it just seemed like too much work.
You are a very dedicated sole and must have the patience of Jobe to spend that time making Litz wire, I don't think I've got that much patience lol
Haha, yeah can't waste stuff that's what I tell my SOH  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 17:00:02 AEDT PM
  
Muntari,
That’s very creative and would certainly wind a lice cable.   A couple of things pop out at me,
The bobbin plate will need to cater for at least 35 bobbins of 0.2 wire or 56 bobbins of 0.16 wire if you are going to spin the Litz in one go.
To protect the strands the slotted discs and the final plate will need to be made from some sort of plastic / PTEP UHMWPE to protect the enamelling.

Autitch

Hi Autitch,

Thanks for the input and observations and yes, that's the problem with handling that gauge wire isn't it and if you have any slack, like Ian has stated, its not far from a rat's nest. I'm not sure on the cost .2 and .16 wire on small bobbins, that's the other issue but  at 56 bobbins, the platter would have to be horizontally mounted, be like the wheel of fortune other wise.

I would probably use HDPE or similar material for the discs for sure.

I'm sure there is a solution out there, it will be good to see Ian's links he was referring to.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: autitch on Friday February 9 2018 17:10:20 AEDT PM
IBGold & Muntari,

My initial gut feeling is that since we aren't building a mono coil but are employing two dedicated coils the TX may not be in this instance that critical to necessitate the "super fast winding technique".  Perhaps the RX may benefit from the improved winding  technique.  I gave twisting a pair of wires a go and I noticed that there is quite a bit of  "shrinkage"  of the wire that takes place especially as the twist per inch count goes up.  This "shrinkage" needs to be taken into account when working out the number  of strands required to achieve the desired linear resistance.

Autitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 22:02:13 AEDT PM
  
IBGold & Muntari,

My initial gut feeling is that since we aren't building a mono coil but are employing two dedicated coils the TX may not be in this instance that critical to necessitate the "super fast winding technique".  Perhaps the RX may benefit from the improved winding  technique.  I gave twisting a pair of wires a go and I noticed that there is quite a bit of  "shrinkage"  of the wire that takes place especially as the twist per inch count goes up.  This "shrinkage" needs to be taken into account when working out the number  of strands required to achieve the desired linear resistance.

Autitch

Hi Autitch,

Yes I'm with you on that one . I know Aziz feels it is important that both should be Litz and in an ideal world I would agree but somewhere along the line we might have to compromise.
I am quite happy to build some prototypes of each proposed version and share findings .
The purpose of doing some small 200mm coils was to have some future reference and be able to compare each type of winding in a like for like situation. I think I'll continue on with that then tackle the next bit.

There are so many variations that I can see just in formers and windings from very experienced coil builders like Ian and others and myself with the MPI coil arrays it's hard to quantify results.

Sometimes I think it's better to be as informed as you can and then just go for it, try new ideas taking on board what's others are doing and saying but ultimately, just doing it.
We know that fir RX Litz is the way to go, Aziz has said that Spider windings are a good thing with certain ratios compared to the TX, I think that's where we should start with the RX.

If the improvements are there as Aziz has calculated, then move onto the Super wound TX

Btw, I noticed on another forum Geotech , Green had done quite a bit with spider/ basket type coils, back in 2016. I don't know where it ended up but quite a few posts.

Interesting on the shrinkage, I think Ian said he use to allow a bit more length too, perhaps for same reason.

I'm still going to carry on with a Litz winding jig and I've been thinking about another variation which may make it easier to realise

More later

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 9 2018 22:25:36 AEDT PM
  
::62:: Hi all,

If you want to read up on the ultimate Litz for coils read Sean Goddard's  Post on ( Geotech http://www.geotech1.com/forums/showthread.php?23838-DIY-Mad-Litz-Wire-for-ULTRA-FAST-PI-Coils ) that is the way to make it.

As for making Litz wire Stefan and I have been hand making it for quite a few years and it takes quite some time and it is nowhere as involved as Sean's wire the strands need to be supported and evenly tension-ed at a minimum of 3 meter intervals and you need about a 30 meter length for an 18" plus coil the RX wires for the two prototypes that I wound I used over 40 meters each I started off at 49 meters it took me 6 hours to set up and wind the two wires and they have about 10 turns per inch or 25.4 mm one of two strands and one of three strands much different to winding TX wire that takes me a day to set up and wind a 30 meter length and I have all the jigs and supports made up I have seen a couple of homemade mechanized machines for winding Litz wire  I will see if I still have the links to them and will post if I can find them I started building one then decided as my other half decided I had built enough coils I should give it away and concentrate on getting out and use what I have but you have to use up the stuff you have you cant have it going to waste that's my excuse.

Regards, Ian. ::62::

Hi Ian,

Have you wound Litz for use in large PI mono coils and if so what are your thoughts on performance?

Hi Aziz,

Have you simulated large Litz wire made large PI mono coils if so are you be able to share any models generated please?

Cheers

Muntari






Title: Re: The need for big deep gold detectors.
Post by: IBGold on Saturday February 10 2018 16:50:32 AEDT PM
 Hi Muntari,

Yes I have used it in Mono's of 18", 24" and a   780 x 600 with half round ends of the two prototypes I have under construction one will pair with the 600 x 600 flat wound square coil I have which as I believe was made by Nuggetfinder and would be a Litz wire coil and the other with the self made 750 x 600 bundle wound Litz wire coil.

 I cannot find the Litz winder information if Dave is reading this could he supply a link as it was he who supplied me with the information a few years back I can report the top half of the housings are made now onto the bottoms  should be complete ready to put together mid next week now have to think about shielding this will be the make or break decision I will have to dig in the cupboard and see what I have left.

Aziz may have modeled some of my coils .

Regards,  Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday February 10 2018 17:02:06 AEDT PM
Hi Ian,

Thanks for the info, were you happy with the mono's performance compared to standard wound?

Good work on those coils to, looking forward to results of testing.

Hopefully Aziz has some models of Litz wound  ::62::

I'm currently getting ready to do some more test formers now that it has cooled a bit here has it cooled your way yet


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: deemon on Saturday February 10 2018 22:38:05 AEDT PM
  
I think, we would require Litz wire for the RX coil.


Hi Aziz !

As for me , I think that you demands too much here ... you see , we need Litz if we have a big current and a high frequency at the same time , but in your application the RX signal current is negligible and there are strong limitation in a coil stray capacitance , so the best wire for RX is a simple thin copper strand , something like .07 mm , for instance .

What about a TX coil - I think that you don't need Litz there too . Of course , the TX current may be big , but this skin effect isn't a major cause of an energy loss in your TX chain , and on the other hand , your RX coil never cross the TX coil wire - as we can see in a DD coil configuration - so you cannot be afraid of any RX signal distortion due to skin effect problem . So if I try to test your concentric coil , I'll use something like .7 mm TX coil wire and .07 mm RX coil wire , and that's must be enough , IMHO .

And the only case when we really need a good Litz wire , as I think , is a very fast mono coil in a square-wave balanced approach , just because the same wire used to transmit and to receive at the same time - and I really can see quite a noticeable quality increase in this application .... 


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday February 11 2018 08:43:41 AEDT AM
Hi all,

the most benefit of using Litz wire for the RX coil is simply reducing further parasitic capacitances (shielding and interwire coil capacitance).
And yes, the RX coil will draw approx. 20 - 40 % of the TX coil energy during the damping period. The skin effect isn't negligible here.

We need Litz wire for the RX coil.

BTW, I can't model Litz wire AC behaviour in my software.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday February 11 2018 19:51:04 AEDT PM
Hi Deemon an Aziz,

Thanks for sharing your knowledge and confirming what I and some other members have been suspecting.

Aziz, that's ok on Litz wire modelling, we'll just have to build some to test...


I will be continuing on with the 200mm ref coils with same inter-wire spacing as per my earlier posts.
Then I'll step up in size to 400mm. RX OD and repeat as per 200mm variations
Again the reason I'm doing test coils at 200mm is that I can get 12 formers out of 1 sheet of foamed PVC this size is also easy to store as references.

After that I'll look into a Diy Litz wire winding machine, Same as described in my earlier post but taking on board what Autitch has pointed out.

Drawings to follow later

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 13 2018 16:25:52 AEDT PM
Hi All,

I completed another former last night, wound it and did some quick checks for SRF etc. see attached photos..
NOTE-- no shielding yet. 1 Meg Ohm resistor in series with coil, coil probe 13pF

Identical machining diameter and wire spacing.  Spider has 2mm deep, 5mm deep alternating section depth, Spiral Single depth 2mm, wire gauge 0.56mm enamelled

Spider L=97.6uH, Q= 0.819 , SRF = 4.44MHz, Cp = 12.5pF,   DCR= 0.76,  wire length = 12.4m

Spiral  L= 100uH, Q= 0.849, SRF = 4.40MHz,  Cp= 12.89pF,  DCR= 0.75, wire length = 12.1m

First pics are of formers and inductance of Spiral

Followed by Spider SRF, then Spiral SRF

Like I said quick checks. So far I don't see much advantage in Spider versus spaced Spiral, I need to wind a spiral with no inter-wire spacing to check.
I will also need to make a couple of large coil formers with both TX and RX machined patterns to make up my mind.
I do see a slight peak amplitude advantage at SRF with Spider but not much.

One last thought, I think there is an optimum inter-wire spacing versus coil size.

Oh, did I say, I love this Foamed PVC..

More later

Cheers

Muntari




Title: Re: The need for big deep gold detectors.
Post by: WM6 on Tuesday February 13 2018 22:10:00 AEDT PM
  


Identical machining diameter and wire spacing.  Spider has 2mm deep, 5mm deep alternating section depth, Spiral Single depth 2mm

Spider L=97.6uH, Q= 0.819 , SRF = 4.44MHz, Cp = 12.5pF,   DCR= 0.76

Spiral  L= 100uH, Q= 0.849, SRF = 4.40MHz,  Cp= 12.89pF,  DCR= 0.75

First pics are of formers and inductance of Spiral



Thanks for all your efforts, Muntari, to providing us really useful data.

So we can say, that all is much as expected, no significant difference between
equal dimensioned spider and spiral coils.

Did you measure how much length of wire you spend for both coils?



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 13 2018 22:36:33 AEDT PM
  
  


Identical machining diameter and wire spacing.  Spider has 2mm deep, 5mm deep alternating section depth, Spiral Single depth 2mm

Spider L=97.6uH, Q= 0.819 , SRF = 4.44MHz, Cp = 12.5pF,   DCR= 0.76

Spiral  L= 100uH, Q= 0.849, SRF = 4.40MHz,  Cp= 12.89pF,  DCR= 0.75

First pics are of formers and inductance of Spiral



Thanks for all your efforts, Muntari, to providing us really useful data.

So we can say, that all is much as expected, no significant difference between
equal dimensioned spider and spiral coils.

Did you measure how much length of wire you spend for both coils?



Hi WM6,

Thanks and no worries at all, I will still finish off the other versions as I outlined in earlier posts but unless there is something that sticks out with more inductance and a larger coil radius or perhaps Litz wire, I'm just not sure but I stand to be corrected and have an open mind.

With the gradiometer type coils, fine enamelled wire was all I ever used A) because Litz wire is crap to work with. B) It is expensive and C) it didn't seem to perform any better on 600 and 400mm coils I made.  I've never owned a commercial Litz wire wound one so can't comment and people like them so I'm just trying to see what is going on for myself.

I did write down the length used but cant find the paper, pretty sure it was around 12 and 12.5m but will recheck later to be sure.

Btw, some of those online inductance calculators are way off in inductance and length used...I don't trust many of them anymore, if someone knows of a reasonably accurate one I'd appreciate a link ::62::

Cheers

Muntari.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 13 2018 22:49:05 AEDT PM
Hi All,

What I have found is that the Foamed PVC is really good for machining, it is readily available and it does not absorb moisture readily.

It is light weight, rigid, has a reasonable temp rating ~ 68 deg C and best of all its Dielectric constant is 1.56 - 2.1.

I had the chance to get 4 pallet loads of the stuff from a sign writer for 0$ but didn't think I would ever use it... oh well

I'll post some more on the large former I'm working on later

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 13 2018 23:03:32 AEDT PM
Hi WM6,

Yep just checked the length used on each coil.

Spider = 12.4

Spiral = 12.1

Have edited the original post with photos to reflect missing data

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Wednesday February 14 2018 00:53:58 AEDT AM
Quote
Btw, some of those online inductance calculators are way off in inductance and length used...I don't trust many of them anymore, if someone knows of a reasonably accurate one I'd appreciate a link

Have not found a good one yet  ::402::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 09:25:56 AEDT AM
Hi 6666,

Did you get your DE-5000 yet?

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 10:52:53 AEDT AM
Hi All,

I realize I have pulled this thread a little sideways from Aziz's original intent which as I stated a few posts ago when Doug asked..what is the purpose of the project..

I replied with...

1) To experiment with and to prove (or disprove) the advantages of a concentric co planer TX/RX coil suitable for deep seeking targets with existing PI detectors, in particular, starting with  the QED.   It is however, not limited to existing designs

2) Along the way showing different build options / methods and arriving at one or more optimum designs.

3) Benefits, -- deeper seeking, lower noise in mineralized ground and hopefully lighter weight coils as compared to similar existing mono coils of same size (18 - 19 inch)

I believe my input was down the lines of #2. I will still complete the other 200mm coils as references (layered spiral, standard straight section spider)

However, given that I have found a suitable material to work with, and now have a better insight into what is required to achieve the original goal,  I will put most my focus back onto experimenting with optimum TX/RX winding ratios with large coils 400mm +.

Cheers

Muntari




Title: Re: The need for big deep gold detectors.
Post by: Doug on Wednesday February 14 2018 10:59:23 AEDT AM
  
Hi All,

I realize I have pulled this thread a little sideways from Aziz's original intent which as I stated a few posts ago when Doug asked..what is the purpose of the project..

I replied with...

1) To experiment with and to prove (or disprove) the advantages of a concentric co planer TX/RX coil suitable for deep seeking targets with existing PI detectors, in particular, starting with  the QED.   It is however, not limited to existing designs

2) Along the way showing different build options / methods and arriving at one or more optimum designs.

3) Benefits, -- deeper seeking, lower noise in mineralized ground and hopefully lighter weight coils as compared to similar existing mono coils of same size (18 - 19 inch)

I believe my input was down the lines of #2. I will still complete the other 200mm coils as references

Given that I think i have found a suitable material to work with, I will put most my focus back onto experimenting with optimum TX/RX winding ratios with large coils 400mm +.

Cheers

Muntari




Don't worry about pulling  this thread a little sideways! ::62::
This is a hot thread and has already been read over 7500 times!
Obviously their is a lot of interest in the topic.
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday February 14 2018 11:22:33 AEDT AM
  
Hi WM6,

Yep just checked the length used on each coil.

Spider = 12.4

Spiral = 12.1

What I have found is that the Foamed PVC is really good for machining, it is readily available and it does not absorb moisture readily.
Muntari

Thanks Muntari

What is factory brand-name of those "Foamed PVC"?
Is it really PVC or some sort of polystyrene or alike technical stuff?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 11:23:48 AEDT AM
Hi Doug,

No worries, I'm just mindful of staying on point but we do need to work through the basics, remove fiction from fact and with every answer there are more questions...


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 11:36:50 AEDT AM
  
  
Hi WM6,

Yep just checked the length used on each coil.

Spider = 12.4

Spiral = 12.1

What I have found is that the Foamed PVC is really good for machining, it is readily available and it does not absorb moisture readily.
Muntari

Thanks Muntari

What is factory brand-name of those "Foamed PVC"?
Is it really PVC or some sort of polystyrene or alike technical stuff?

Hi WM6,

Yes it is certainly foamed PVC not PVC clad foam...

PALRAM is the manufacturer of the material I use

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 11:48:52 AEDT AM
  
  
  
Hi WM6,

Yep just checked the length used on each coil.

Spider = 12.4

Spiral = 12.1

What I have found is that the Foamed PVC is really good for machining, it is readily available and it does not absorb moisture readily.
Muntari

Thanks Muntari

What is factory brand-name of those "Foamed PVC"?
Is it really PVC or some sort of polystyrene or alike technical stuff?

Hi WM6,

Yes it is certainly foamed PVC not PVC clad foam...

PALRAM is the manufacturer of the material I use

Cheers

Muntari




Here is a link to the material I am using

https://www.bunnings.com.au/suntuf-3-x-600-x-1200mm-white-pvc-foam-sheet_p1010814

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Wednesday February 14 2018 12:20:55 AEDT PM
  
::62:: Hi all,

If you want to read up on the ultimate Litz for coils read Sean Goddard's  Post on ( Geotech http://www.geotech1.com/forums/showthread.php?23838-DIY-Mad-Litz-Wire-for-ULTRA-FAST-PI-Coils ) that is the way to make it.

As for making Litz wire Stefan and I have been hand making it for quite a few years and it takes quite some time and it is nowhere as involved as Sean's wire the strands need to be supported and evenly tension-ed at a minimum of 3 meter intervals and you need about a 30 meter length for an 18" plus coil the RX wires for the two prototypes that I wound I used over 40 meters each I started off at 49 meters it took me 6 hours to set up and wind the two wires and they have about 10 turns per inch or 25.4 mm one of two strands and one of three strands much different to winding TX wire that takes me a day to set up and wind a 30 meter length and I have all the jigs and supports made up I have seen a couple of homemade mechanized machines for winding Litz wire  I will see if I still have the links to them and will post if I can find them I started building one then decided as my other half decided I had built enough coils I should give it away and concentrate on getting out and use what I have but you have to use up the stuff you have you cant have it going to waste that's my excuse.

Regards, Ian. ::62::

IMHO for the time and money it takes to make lizt .. better off buy the stuff ... just saying


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 12:27:38 AEDT PM
Hi All,

Here's a link to foamed PVC fabrication

http://www.palram.com/palight

BTW, it can be used up to 75 deg C not 68 as I stated earlier ::62::
Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 12:31:23 AEDT PM
  
  
::62:: Hi all,

If you want to read up on the ultimate Litz for coils read Sean Goddard's  Post on ( Geotech http://www.geotech1.com/forums/showthread.php?23838-DIY-Mad-Litz-Wire-for-ULTRA-FAST-PI-Coils ) that is the way to make it.

As for making Litz wire Stefan and I have been hand making it for quite a few years and it takes quite some time and it is nowhere as involved as Sean's wire the strands need to be supported and evenly tension-ed at a minimum of 3 meter intervals and you need about a 30 meter length for an 18" plus coil the RX wires for the two prototypes that I wound I used over 40 meters each I started off at 49 meters it took me 6 hours to set up and wind the two wires and they have about 10 turns per inch or 25.4 mm one of two strands and one of three strands much different to winding TX wire that takes me a day to set up and wind a 30 meter length and I have all the jigs and supports made up I have seen a couple of homemade mechanized machines for winding Litz wire  I will see if I still have the links to them and will post if I can find them I started building one then decided as my other half decided I had built enough coils I should give it away and concentrate on getting out and use what I have but you have to use up the stuff you have you cant have it going to waste that's my excuse.

Regards, Ian. ::62::

IMHO for the time and money it takes to make lizt .. better off buy the stuff ... just saying


Hi Gef12,

Yeah, it's a lot of work by hand, I wouldn't have the patience for it .. maybe of benefit with a compact winder for custom wire

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday February 14 2018 14:46:52 AEDT PM
  

Here is a link to the material I am using

https://www.bunnings.com.au/suntuf-3-x-600-x-1200mm-white-pvc-foam-sheet_p1010814


Thanks.
I found such PVC-hard-foam material here locally too now.
It is used for promo panels.


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday February 14 2018 16:37:27 AEDT PM
Hi all I agree it is a pain but if you cannot get the strand count/AWG wire you want for a purpose it leaves you no option don't worry I steer clear of making it if I can.

 I can report I have the XPS shield former's made and the housings completed do you want pictures before I start assembling to see how I make one off's.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Wednesday February 14 2018 16:40:06 AEDT PM
  
Hi 6666,

Did you get your DE-5000 yet?

cheers

Muntari

Not yet still in the mail, but I'm sweating on it  ::62::


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Wednesday February 14 2018 16:44:58 AEDT PM
  
Hi all I agree it is a pain but if you cannot get the strand count/AWG wire you want for a purpose it leaves you no option don't worry I steer clear of making it if I can.

 I can report I have the XPS shield former's made and the housings completed do you want pictures before I start assembling to see how I make one off's.

Regards, Ian. ::62::

Some pictures would be handy thanks.


Title: Re: The need for big deep gold detectors.
Post by: autitch on Wednesday February 14 2018 16:48:55 AEDT PM
  
Hi all I agree it is a pain but if you cannot get the strand count/AWG wire you want for a purpose it leaves you no option don't worry I steer clear of making it if I can.

 I can report I have the XPS shield former's made and the housings completed do you want pictures before I start assembling to see how I make one off's.

Regards, Ian. ::62::

Yes please Ian.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 16:51:31 AEDT PM
  
Hi all I agree it is a pain but if you cannot get the strand count/AWG wire you want for a purpose it leaves you no option don't worry I steer clear of making it if I can.

 I can report I have the XPS shield former's made and the housings completed do you want pictures before I start assembling to see how I make one off's.

Regards, Ian. ::62::

Yes please Ian

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday February 14 2018 21:19:45 AEDT PM
Hi all,

I have been a bit desperate with my sound card impedance meter.
This is the story:
I have found an old coil wound with 30 x 0.1 mm true Litzwire. Measured its series resistor Rs up to 24 kHz and it still showed significant frequency dependence. (Oh well, it showed almost no difference to single strand magnet wire  ::406::).
I have cross-checked the measurement by measuring an 1 Ohm metal film resistor: No frequency dependence. The measurement seems to be ok.

There must be perhaps something wrong. I want to rewrite my sound card impedance meter using FFT algorithm and cross-check next time

Pity, I don't have any Litz wire anymore and I can't reuse the Litz wire in the old coil (glued with synthetic resin).

Building a Litz wire winding machine doesn't make much sense. The thin enamelled copper wire (0.1 mm and below) costs by weight almost the same as ready produced Litz wire.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 21:45:26 AEDT PM
  
Hi all,

I have been a bit desperate with my sound card impedance meter.
This is the story:
I have found an old coil wound with 30 x 0.1 mm true Litzwire. Measured its series resistor Rs up to 24 kHz and it still showed significant frequency dependence. (Oh well, it showed almost no difference to single strand magnet wire  ::406::).
I have cross-checked the measurement by measuring an 1 Ohm metal film resistor: No frequency dependence. The measurement seems to be ok.

There must be perhaps something wrong. I want to rewrite my sound card impedance meter using FFT algorithm and cross-check next time

Pity, I don't have any Litz wire anymore and I can't reuse the Litz wire in the old coil (glued with synthetic resin).

Building a Litz wire winding machine doesn't make much sense. The thin enamelled copper wire (0.1 mm and below) costs by weight almost the same as ready produced Litz wire.

Cheers,
Aziz

Hi Aziz,

It's a pity you are having issues with measuring Rs. Either it's correct And you trust what it's saying, or you have  a very weird fault. Hope you can sort it out soon.


On Litz wire winding machine, as Ian says, if you can't get the size and strands you require, then you have no option but to wind your own. In that case, a simple winding machine makes perfect sense, given you could also use the same for producing simple twisted pair wires. It doesn't have to be made from anyting more than plywood really, no need to spend much making one.
Personally, I will never wind Litz by hand again but I am interested enough to come up with a design anyone could DIY. ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 21:53:26 AEDT PM
  
  
Hi 6666,

Did you get your DE-5000 yet?

cheers

Muntari

Not yet still in the mail, but I'm sweating on it  ::62::

Hope it turns up soon 6666, I don't think you can go wrong with that meter for coil use.

I'm still waiting on the Agilent to come back but at this time of year a lot of my gear goes for calibration and test and I drop back to my second tier test gear.. I am glad I've got the De-5000 now..

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday February 14 2018 22:06:30 AEDT PM
Hi Muntari,

nices coils you built there.  ::05::

Here are some important notes on interwire coil capacitances:

One sided flat spiral vs. spider web coil:
In your coil design, the flat spiral coil has enough interwire spacing. So there is no more benefit of using spider web coil design. Best leave it to the flat spiral coil design with enough interwire spacing.
A flat spiral coil without interwire spacing would have higher interwire coil capacitance of course. That was the reason for going for spider web coil design.

Two sided spiral coil former consisting of two partial coils:
Coil one begins on the one side and coil two on the other side. Interwire spacing on both sides are interleaved.
There is absolutely no benefit at all. The coil can be seen as a center-tapped Tesla coil, except the other coil part has some vertical distance to the first coil. This coil would have much much more interwire coil capacitance.

We have to ensure, that the coil windings are being progressively wound. That wouldn't be the case for Tesla coil or the two sided spiral coils. The goal is to minimize the partial stored interwire capacitor energy between the coil windings.

According to the formula
E = 0.5*C*U², where

E = energy stored in a capacitor,
C = capacitance
U = voltage across the capacitor

we have to ensure, that the energy stored in the partial capacitances is kept minimal. Only the progressive coil winding technique ensures that the induced voltage between each loop turn is kept small.
On the example above (two sides sprial coil or center-tapped Tesla coil) the induced voltage between coil halves is immense and there would be stored a lot of energy in the partial interwire coil capacitances.

So the coil should be wound strict progressively.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday February 14 2018 22:25:36 AEDT PM
  

Hi Aziz,

..
On Litz wire winding machine, as Ian says, if you can't get the size and strands you require, then you have no option but to wind your own. In that case, a simple winding machine makes perfect sense, given you could also use the same for producing simple twisted pair wires. It doesn't have to be made from anyting more than plywood really, no need to spend much making one.
Personally, I will never wind Litz by hand again but I am interested enough to come up with a design anyone could DIY. ::62::

Cheers
Muntari
Hi Muntari,

BTW, I have all the parts for a nice Litz wire winding machine at home and I can build it.
One slow running motor with in-built gearing.
One powerfull motor for twisting (a small 100 W hand drill of course).
Two PWM motor controllers (already built and ready to use).
It's only a matter of time to build this machine.

But I have to resolve the impedance meter issues first. If the series resistor Rs can not be kept small enough on high frequencies, than I would use thicker Litz wires (more strands). This is required to minimize the thermal noise of the coil on high frequencies (early sampling times).

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday February 14 2018 22:47:35 AEDT PM
Now to the story of using pure Litz wire regards to interwire coil capacitance.

Each enamelled strand caries equal amount of partial coil current and at switch-off flyback period each strand stores equal amount of charge. But a lot of inner strands being placed in a Faraday cage and do not contribute to the interwire coil capacitance. These strands being fully electrical shielded. The amount of charge stored outside of the wire (the outside strands) is smaller than compared to a single strand coil wire.

This is the reason, why the true Litz wire should minimize the interwire coil capacitance.
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 22:49:51 AEDT PM
  
Hi Muntari,

nices coils you built there.  ::05::

Here are some important notes on interwire coil capacitances:

One sided flat spiral vs. spider web coil:
In your coil design, the flat spiral coil has enough interwire spacing. So there is no more benefit of using spider web coil design. Best leave it to the flat spiral coil design with enough interwire spacing.
A flat spiral coil without interwire spacing would have higher interwire coil capacitance of course. That was the reason for going for spider web coil design.

Two sided spiral coil former consisting of two partial coils:
Coil one begins on the one side and coil two on the other side. Interwire spacing on both sides are interleaved.
There is absolutely no benefit at all. The coil can be seen as a center-tapped Tesla coil, except the other coil part has some vertical distance to the first coil. This coil would have much much more interwire coil capacitance.

We have to ensure, that the coil windings are being progressively wound. That wouldn't be the case for Tesla coil or the two sided spiral coils. The goal is to minimize the partial stored interwire capacitor energy between the coil windings.

According to the formula
E = 0.5*C*U², where

E = energy stored in a capacitor,
C = capacitance
U = voltage across the capacitor

we have to ensure, that the energy stored in the partial capacitances is kept minimal. Only the progressive coil winding technique ensures that the induced voltage between each loop turn is kept small.
On the example above (two sides sprial coil or center-tapped Tesla coil) the induced voltage between coil halves is immense and there would be stored a lot of energy in the partial interwire coil capacitances.

So the coil should be wound strict progressively.

Cheers,
Aziz

Hi Aziz,

Thanks, I'm glad we are in agreement on the Spider versus spaced Spiral ::62::

Of course I had an image in my head with dual layered Spiral acting like a Tesla but I was interested in the effect of different winding directions in to out flip, then in to out again, or in to out, flip then out to in all with same vertical and horizontal spacing and offset.  This was for TX only.
That's why I asked if you could model ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 22:53:36 AEDT PM
  
Now to the story of using pure Litz wire regards to interwire coil capacitance.

Each enamelled strand caries equal amount of partial coil current and at switch-off flyback period each strand stores equal amount of charge. But a lot of inner strands being placed in a Faraday cage and do not contribute to the interwire coil capacitance. These strands being fully electrical shielded. The amount of charge stored outside of the wire (the outside strands) is smaller than compared to a single strand coil wire.

This is the reason, why the true Litz wire should minimize the interwire coil capacitance.
Aziz

Hi Aziz,

I will also be making same spiral sized former to wind with Litz

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 22:58:47 AEDT PM
  
  

Hi Aziz,

..
On Litz wire winding machine, as Ian says, if you can't get the size and strands you require, then you have no option but to wind your own. In that case, a simple winding machine makes perfect sense, given you could also use the same for producing simple twisted pair wires. It doesn't have to be made from anyting more than plywood really, no need to spend much making one.
Personally, I will never wind Litz by hand again but I am interested enough to come up with a design anyone could DIY. ::62::

Cheers
Muntari
Hi Muntari,

BTW, I have all the parts for a nice Litz wire winding machine at home and I can build it.
One slow running motor with in-built gearing.
One powerfull motor for twisting (a small 100 W hand drill of course).
Two PWM motor controllers (already built and ready to use).
It's only a matter of time to build this machine.

But I have to resolve the impedance meter issues first. If the series resistor Rs can not be kept small enough on high frequencies, than I would use thicker Litz wires (more strands). This is required to minimize the thermal noise of the coil on high frequencies (early sampling times).

Cheers,
Aziz

Hi Aziz,

That's great, it will interesting to see what you come up with re Litz wire winder.

Hope you sort the issues with the impedance meter soon ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 14 2018 23:04:30 AEDT PM
Btw Aziz, Great discussion as usual

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 15 2018 10:38:40 AEDT AM
Hi Aziz,

This is the winding of double layered spiral, series wound.

I would have thought that with enough offset and vertical / horizontal spacing Cp can be reduced.

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday February 15 2018 16:30:23 AEDT PM
Hi All,

As promised for your information some of my coil build pictures anyone just a little handy should be able to replicate other than normal hand tools I use a band saw, router table and a laminate trimmer with jigs made to suit now for the pictures.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 15 2018 19:00:03 AEDT PM
  
Hi All,

As promised for your information some of my coil build pictures anyone just a little handy should be able to replicate other than normal hand tools I use a band saw, router table and a laminate trimmer with jigs made to suit now for the pictures.

Regards, Ian. ::62::


Hi Ian,

Great work! They look very good, thanks for sharing
What is the shell material Ian?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday February 15 2018 20:54:40 AEDT PM
  
Hi Aziz,

This is the winding of double layered spiral, series wound.

I would have thought that with enough offset and vertical / horizontal spacing Cp can be reduced.

cheers

Muntari


Hi Muntari,

this coil will still have large Cp. Each coil half has progressive winding but the two coil halves together don't.
At the beginning and end windings, there will be induced high voltage and the stored stray capacitance energy will be quite large.
It is still a kind of Tesla coil, even there is a large space between the coil halves.

The pure single layer spiral coil is a pure progressive winding coil, which will have the least Cp.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday February 15 2018 20:57:02 AEDT PM
Nice coil Ian,

I hope, the final SRF is high enough.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday February 15 2018 23:00:52 AEDT PM
  
  
Hi Aziz,

This is the winding of double layered spiral, series wound.

I would have thought that with enough offset and vertical / horizontal spacing Cp can be reduced.

cheers

Muntari


Hi Muntari,

this coil will still have large Cp. Each coil half has progressive winding but the two coil halves together don't.
At the beginning and end windings, there will be induced high voltage and the stored stray capacitance energy will be quite large.
It is still a kind of Tesla coil, even there is a large space between the coil halves.

The pure single layer spiral coil is a pure progressive winding coil, which will have the least Cp.

Cheers,
Aziz

Hi Aziz,

Yes, on the money as usual Aziz,  I did some testing today, some things expected as you have previously well noted, I'm not 100% sold on the idea but did note some interesting things which I will post at a later date as it is not strictly related to what we are doing here and more testing will be done in line with known theory.. and I would rather not be side tracked anymore so will leave it there.  ::62::

Here is a draft of the former I hope to machine in next day or two

Basically an 18" former
Material = 6mm Foamed PVC
TX = 40 turns
RX = 54 turns  
turns ratio I think is about 1.4
TX/RX size ratio   TX OD to RX OD = 0.6
Wire spacing = 1.5mm
Groove depth = 3mm
Groove width = 1mm

Note: - more turns than required but for testing I can position the start and finish to suit, hence fat sections

Feel free to comment, else I'll go ahead and create the tool paths tomorrow night

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Friday February 16 2018 14:49:15 AEDT PM
  
Hi All,

As promised for your information some of my coil build pictures anyone just a little handy should be able to replicate other than normal hand tools I use a band saw, router table and a laminate trimmer with jigs made to suit now for the pictures.

Regards, Ian. ::62::


I love  your work Ian ..
are these just Rx coil ?   what material is being used and have you incorporated shield ...
soon to commence mine ... just reading back thru the material on specs to use. Will be using the litz I had purchased .... happy days


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Friday February 16 2018 15:33:55 AEDT PM
Hi all yes they are RX only coils for use with existing Mono's used as the TX coils the housing material is 1.0 mm ABS black as it was the only color available last time I purchased sheets the former materials are as previously discussed XPS sheets from IKEA and HIPS from a plastic supplier.

 Aziz pre shielding the SRF is in the high 500's so what is the answer to an ultra low capacitance shielding I have a couple of ideas but am open to out of the box suggestions.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday February 16 2018 19:59:16 AEDT PM
  
..
 Aziz pre shielding the SRF is in the high 500's so what is the answer to an ultra low capacitance shielding I have a couple of ideas but am open to out of the box suggestions.

Regards, Ian. ::62::

Hi Ian,

regarding low capacitance shielding:
Take enough shielding spacer. 10 mm on each side with EPS sheets would be ok. Use graphite on paper for shielding and a thin silver plated copper drain wire taped onto the graphite paper shielding.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday February 16 2018 20:11:03 AEDT PM
  
Hi Aziz,

Yes, on the money as usual Aziz,  I did some testing today, some things expected as you have previously well noted, I'm not 100% sold on the idea but did note some interesting things which I will post at a later date as it is not strictly related to what we are doing here and more testing will be done in line with known theory.. and I would rather not be side tracked anymore so will leave it there.  ::62::

Here is a draft of the former I hope to machine in next day or two

Basically an 18" former
Material = 6mm Foamed PVC
TX = 40 turns
RX = 54 turns  
turns ratio I think is about 1.4
TX/RX size ratio   TX OD to RX OD = 0.6
Wire spacing = 1.5mm
Groove depth = 3mm
Groove width = 1mm

Note: - more turns than required but for testing I can position the start and finish to suit, hence fat sections

Feel free to comment, else I'll go ahead and create the tool paths tomorrow night

Cheers

Muntari


Hi Muntari,

I like your idea of making an universal coil former. The TX section spiral for thicker coil wires (1.4 - 2.4 mm diam.) and the inner RX section for thinner coil wires (up to 0.7 mm diam. ). So we are free to start each coil at appropriate positions and number of turns.

Yep, sounds very good!

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 16 2018 21:10:22 AEDT PM
  
  
Hi Aziz,

Yes, on the money as usual Aziz,  I did some testing today, some things expected as you have previously well noted, I'm not 100% sold on the idea but did note some interesting things which I will post at a later date as it is not strictly related to what we are doing here and more testing will be done in line with known theory.. and I would rather not be side tracked anymore so will leave it there.  ::62::

Here is a draft of the former I hope to machine in next day or two

Basically an 18" former
Material = 6mm Foamed PVC
TX = 40 turns
RX = 54 turns  
turns ratio I think is about 1.4
TX/RX size ratio   TX OD to RX OD = 0.6
Wire spacing = 1.5mm
Groove depth = 3mm
Groove width = 1mm

Note: - more turns than required but for testing I can position the start and finish to suit, hence fat sections

Feel free to comment, else I'll go ahead and create the tool paths tomorrow night

Cheers

Muntari


Hi Muntari,

I like your idea of making an universal coil former. The TX section spiral for thicker coil wires (1.4 - 2.4 mm diam.) and the inner RX section for thinner coil wires (up to 0.7 mm diam. ). So we are free to start each coil at appropriate positions and number of turns.

Yep, sounds very good!

Cheers,
Aziz

Hi Aziz,

Thanks for the feedback, I'm currently finishing off the design and will widen the TX spiral toolpath with a fine v groove depth of 3mm and top width of 2mm.
That will hold fine wires at bottom or thicker towards the top.
Inter- wire spacing will remain at 1.5 fir first one.

Will post photos of progress .

Cheers

Muntari.





Title: Re: The need for big deep gold detectors.
Post by: IBGold on Saturday February 17 2018 16:07:35 AEDT PM
  
  
..
 Aziz pre shielding the SRF is in the high 500's so what is the answer to an ultra low capacitance shielding I have a couple of ideas but am open to out of the box suggestions.

Regards, Ian. ::62::

Hi Ian,

regarding low capacitance shielding:
Take enough shielding spacer. 10 mm on each side with EPS sheets would be ok. Use graphite on paper for shielding and a thin silver plated copper drain wire taped onto the graphite paper shielding.

Cheers,
Aziz

Hi Aziz,

 I had already done that except the wire is attached to the paper before adding the shield paint (Electrodag) as used commercially so I will trial fit to one coil tomorrow and see what coil to shield capacitance I get the other option was to use the 316 Stainless steel shielding mesh but I would have to do in in pieces as that is all I have left I was hoping we might get some out of the box ideas we could try but at least this method is what commercial operators would use if it works and they decide to copy the ideas.

XPS spacer thicknesses are 12 mm.

What shield resistance per inch would you like at present about 160 ohms per inch but I can adjust.

Regards, Ian.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday February 18 2018 06:05:43 AEDT AM
  
Hi Aziz,

 I had already done that except the wire is attached to the paper before adding the shield paint (Electrodag) as used commercially so I will trial fit to one coil tomorrow and see what coil to shield capacitance I get the other option was to use the 316 Stainless steel shielding mesh but I would have to do in in pieces as that is all I have left I was hoping we might get some out of the box ideas we could try but at least this method is what commercial operators would use if it works and they decide to copy the ideas.

XPS spacer thicknesses are 12 mm.

What shield resistance per inch would you like at present about 160 ohms per inch but I can adjust.

Regards, Ian.

Hi Ian,

I for one wouldn't use the stainless steel shielding. It is ferro magnetic and no go for us.

A simple high impedance graphite shielding on paper is ok.
I have measured my graphite on paper shielding of approx. 6 kOhm/inch. I haven't polished the shielding yet and it's resistance will go down, when it is polished.
160 Ohm/inch is quite low but is ok, when it is working.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday February 18 2018 06:13:46 AEDT AM
Hi all,

I have solved my sound card impedance meter issue now.
Nothing wrong with the software. Even the FFT algorithm delivers the same results and behaviour.

The problem is the measurement range and the reference resistor Rref.
The measurement will be more accurate, when the measured impedance Z is approx. the same as reference resistor resistance.
I have to use higher reference resistor values when I measure with high test frequencies. That's all.

I have to make the impedance measurements once again and you will see soon, that a thin single strand enamelled copper wire isn't as critical as thought. And I will make the measurement for true 30 x 0.1 mm Litz wire coil too.
 ::10 ::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Sunday February 18 2018 15:37:39 AEDT PM
Hi Aziz the commercial graphite shielding is applied at 60 to 80 ohms per inch or it was they may have changed formulation these days.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 19 2018 09:47:10 AEDT AM
  
Hi all,

I have solved my sound card impedance meter issue now.
Nothing wrong with the software. Even the FFT algorithm delivers the same results and behaviour.

The problem is the measurement range and the reference resistor Rref.
The measurement will be more accurate, when the measured impedance Z is approx. the same as reference resistor resistance.
I have to use higher reference resistor values when I measure with high test frequencies. That's all.

I have to make the impedance measurements once again and you will see soon, that a thin single strand enamelled copper wire isn't as critical as thought. And I will make the measurement for true 30 x 0.1 mm Litz wire coil too.
 ::10 ::
Cheers,
Aziz

Hi Aziz,

That is good news, glad you found the issue.
Looking forward to your measurments.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 19 2018 10:02:37 AEDT AM
  
Hi Aziz the commercial graphite shielding is applied at 60 to 80 ohms per inch or it was they may have changed formulation these days.

Regards, Ian. ::62::

Hi Ian,

I have used a product called MG Super Shield with excellent results.

Trick with this Nickel based product is to thin it down and apply 2-3 light coats and it is not seen by detector.

With a normal coat, not thinned, it is about 0.004 Ohms per CM so you have to watch how it is applied.

You can apply it in a branched pattern, or completely cover inside housing, both work, just different amount of effort.

I will post some photos and more info when I complete the big coil.

Tool path for the 18" TX/RX coil is completed so its just a matter of finding time to get back into workshop to machine the former and housing.

Ill try to post some drawings later today on construction of the test unit assembly.

Only thing I'm missing is some XPS for shield spacer

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 19 2018 14:49:41 AEDT PM
Hi All,

This is a draft of the 18 inch mono housing which will be machined from laminated Foamed PVC then eventually vacuum molded.

The TX/RX variant will be a modified version of this with slightly larger diameter housing.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Monday February 19 2018 15:26:11 AEDT PM
Nice.


Title: Re: The need for big deep gold detectors.
Post by: autitch on Monday February 19 2018 15:44:01 AEDT PM
Nice work Muntari.
The 18” coil size will be a killer.  Just an observation or two.   You may want to look to reduce the stress raiser at the mounting shaft clevis outside corners.  This is an area of especially high stresses especially as the coil increase in size.  I have seen quite a number of coil housing failures due to poor transition in this area.  As inspiration the NF clevis mount is very robust but necessitates an injection moulded component (could be 3D printed).  For a vacuumed formed arrangement  I like the way Coiltek do this detail on the 14” round coils and by contrast the way they do it on the 14x9 is terrible, a real recipe for cracks which from all reports they have had a few.
The location of the cable entry may not be optimal as the cable path is appears to be slightly obscured to be able to go down the arm.
AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 19 2018 16:13:08 AEDT PM
  
Nice work Muntari.
The 18” coil size will be a killer.  Just an observation or two.   You may want to look to reduce the stress raiser at the mounting shaft clevis outside corners.  This is an area of especially high stresses especially as the coil increase in size.  I have seen quite a number of coil housing failures due to poor transition in this area.  As inspiration the NF clevis mount is very robust but necessitates an injection moulded component (could be 3D printed).  For a vacuumed formed arrangement  I like the way Coiltek do this detail on the 14” round coils and by contrast the way they do it on the 14x9 is terrible, a real recipe for cracks which from all reports they have had a few.
The location of the cable entry may not be optimal as the cable path is appears to be slightly obscured to be able to go down the arm.
AuTitch


Hi Autitch,

Thanks for your comments and observations.

Yes, it is not optimal for sure, and good point on the corner stresses, I would normally spread the load radially and have a broader sweep so there is enough cavity to fill with epoxy. I haven't done the stress analysis on it yet and something I will do.
Thanks for the heads up on Coiltek and NF housings, I deliberately avoid looking at other products when doing a first draft  design and then take a peek to see where it can be improved, old habits  ::62::

Again, great input, its always good to get feedback, I appreciate it.

I've got to go into workshop tonight and machine that 18" former which will take 3.5hours.

When the design is finalised, I will make an aluminium tool piece with inverted pattern of former.
I did some tests with the 200mm Foamed PVC former and found I can heat soften the material and then press a 2mm deep x 1mm spiral pattern into it quite easily.

If this works on a larger scale (18+") then it will be happy days.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 19 2018 16:33:21 AEDT PM
Hi Autitch,

Just had a good look at those coils and can see what you are saying.
I'll work on that with a similar solution, thanks again

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Monday February 19 2018 16:52:22 AEDT PM
Love ur work Muntari ..
going into production on these are we    lol


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 19 2018 21:58:20 AEDT PM
  
Love ur work Muntari ..
going into production on these are we    lol

Thanks gef12,

Haha, nah, just force of habit , too many years in electronics design for manufacture and an idle mind  ::62::

I'm interested to see how Aziz's theory pans out so just thought I would contribute to the cause..

Mind you, maybe I could do something haha  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 19 2018 22:04:37 AEDT PM
  
Nice.

Thanks 6666,

Hey, did you get your meter yet?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 19 2018 23:25:00 AEDT PM
Hi All,

After a long night in the workshop, with CNC cutting away at the large former, I had a bit of time to think of ways to reduce the amount of time it takes to machine these test pieces.

Basically I am going to machine up  a crease wheel similar to this

https://www.cncroutershop.com/us_en/knife-blades/creasing-wheels.html
 and heat the Foamed PVC and try and crease the spiral pattern (only has to go 2-3mm in depth) in one pass.
The only gotcha is there will be a minimum diameter I could do this way because of the radius of the wheel but we will see.

Currently with a 1mm endmill, I have to dumb down the feed rate to prevent snapping bits.

I know from my previous tests I can press a 200mm diameter spiral pattern with the heat softened foamed PVC, so I'm hoping I can produce some results this way.

If it works then producing one off formers will be quick and easy, It is a thermo plastic so should work Ok

Lets see if it works  ::62::

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday February 20 2018 00:13:52 AEDT AM
Hi Muntari,

you can heat press XPS sheets to make mass production of XPS coil formers. And it is quite cheap.

And it seems, I can even make my own XPS spiral coil formers with soldering iron and a thin steel pin mounted onto it.
Manually by hand of course. But a mechanical tool is requied to make it easier.
 ::62::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Tuesday February 20 2018 00:58:33 AEDT AM
I'm thinking along the line of a PCB drill and some sort of router bit


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 20 2018 10:48:17 AEDT AM
Hi Aziz and 6666,

Yes, both of your ideas will work. You just need some reasonable control over positioning at the wire spacing we are thinking of.
Aziz, I will try the same idea on XPS sheets too.

XPS and Foamed PVC machines very well, just use a 1 or 2 flute end mill as you want to clear the chips from the cut. Too many flutes and you will gum up and snap the bit.
A simple mechanical drive based on a turntable type platter and ball screw would do the trick. The platter holds the material, the ball screw holds tool.
You would drive them with variable speed motors to obtain required pitch, very simple setup.

I will try the creasing wheel idea but instead of heating the sheet of material,  I will heat the wheel with a ceramic heating element as used in 3D printer nozzles

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 20 2018 12:05:20 AEDT PM
Hi All,

Here is the basic (very) idea of making your own spiral cutter.
2 Axis motor driven.

Make a simple gantry over platter so ball screw assembly is supported both sides.
You can adjust the ball screw assembly on gantry or platter assembly up and down to obtain required depth.

Its probably more rigid if you move platter as a Z axis assembly rather than the X axis.

What is not shown is the X axis support rail etc

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Tuesday February 20 2018 14:21:15 AEDT PM
My DE-5000 arrived today  ::10 ::

did a couple of quick tests in Auto mode, seems to work, more testing later  ::419::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 20 2018 15:28:34 AEDT PM
  
My DE-5000 arrived today  ::10 ::

did a couple of quick tests in Auto mode, seems to work, more testing later  ::419::

Happy days  ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 20 2018 15:31:11 AEDT PM
Hi All,

Here is a quick assembly drawing of the 18" test coil I'm working on.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Tuesday February 20 2018 23:36:29 AEDT PM
Artwork!

You should go in touch with NASA to redesign space station.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 21 2018 00:06:09 AEDT AM
  
Artwork!

You should go in touch with NASA to redesign space station.

Hi WM6,

Haha, thanks but the software does all the work, I just push and click the mouse  ::62::

Just trying to show what I'm thinking and doing as regards coils etc


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday February 21 2018 16:01:22 AEDT PM
Hi all,

I have started shielding the prototypes the first one is finished and I am pleased with it so far the specifications shielded are Inductance 707 uh resistance 9.98 ohms shield to coil capacitance is 81.2 pf I like the carbon to paper shielding but it is a bit fiddly to apply here are some pictures for your information and it looks like SRF will be above 500 KHz.

Regards, Ian.


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Wednesday February 21 2018 16:52:52 AEDT PM
  
Hi All,

Here is a quick assembly drawing of the 18" test coil I'm working on.

Cheers

Muntari
I think u have done this stuff before mate .. awesome stuff   lol


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 21 2018 18:37:52 AEDT PM
  

I think u have done this stuff before mate .. awesome stuff   lol
[/quote]

Yeah, a few times gef12  lol  ::62::

And how good is Ian's work, hats off to you Ian,  great work and thanks for sharing your knowledge!

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 21 2018 18:39:28 AEDT PM
  
Hi all,

I have started shielding the prototypes the first one is finished and I am pleased with it so far the specifications shielded are Inductance 707 uh resistance 9.98 ohms shield to coil capacitance is 81.2 pf I like the carbon to paper shielding but it is a bit fiddly to apply here are some pictures for your information and it looks like SRF will be above 500 KHz.

Regards, Ian.

Great work Ian, how long did it take you to assemble..?


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday February 21 2018 19:37:04 AEDT PM
  
Hi all,

I have started shielding the prototypes the first one is finished and I am pleased with it so far the specifications shielded are Inductance 707 uh resistance 9.98 ohms shield to coil capacitance is 81.2 pf I like the carbon to paper shielding but it is a bit fiddly to apply here are some pictures for your information and it looks like SRF will be above 500 KHz.

Regards, Ian.

Hi Ian,

well done. Nice coils.  ::62::

Let's look for an appropriate coax cable for the RX coil.

This is a list of coax cables:
http://www.rfcafe.com/references/electrical/coax-chart.htm

For a low capacitance RX coax cable, we need relative high impedance cables. Total length 9 ft (approx. 3 m lenght).
Some of the low capacitance coils are getting too thick (outer diameter well above 10 mm).
So let's look at appropriate ones:

RG-210/U: Z0 = 93 Ohm, O.D.=6.15 mm, C=13.5 pF/ft, C=121.5 pF/9 ft, SRF = 420 kHz (may work)
RG-63 B/U: Z0 = 125 Ohm, O.D.=10.3 mm, C=10 pF/ft, C=90 pF/9 ft, SRF = 457 kHz (may work)
RG-114A/U: Z0 = 185 Ohm, O.D.=10.3 mm, C=6.5 pF/ft, C=58.5 pF/9 ft, SRF = 506 kHz (should work)

Although some coax cables lead SRF to below 500 kHz, the RX coil may still work. We just have to try it out.
So trying with the RG-210/U coax cable would be interesting. The coax cable isn't much thick and should be easily available.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Thursday February 22 2018 11:51:57 AEDT AM
  
Hi all,

I have started shielding the prototypes the first one is finished and I am pleased with it so far the specifications shielded are Inductance 707 uh resistance 9.98 ohms shield to coil capacitance is 81.2 pf I like the carbon to paper shielding but it is a bit fiddly to apply here are some pictures for your information and it looks like SRF will be above 500 KHz.

Regards, Ian.

Didn't see this yesterday for some reason .. thou .. very nice Ian ..  quality workmanship ..
hope she performs well


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday February 22 2018 16:12:35 AEDT PM
  
  
Hi all,

I have started shielding the prototypes the first one is finished and I am pleased with it so far the specifications shielded are Inductance 707 uh resistance 9.98 ohms shield to coil capacitance is 81.2 pf I like the carbon to paper shielding but it is a bit fiddly to apply here are some pictures for your information and it looks like SRF will be above 500 KHz.

Regards, Ian.

Great work Ian, how long did it take you to assemble..?

Hi Muntari I applied the shielding to the second coil today and it virtually took all day so it is not quick but this one turned out a bit neater I will measure the coil to shield capacitance tomorrow.

Aziz yes now the fun starts with coax I will have to see what I can get for my configuration I only need 1400 mm so we will see.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 23 2018 00:16:29 AEDT AM
  
  
  
Hi all,

I have started shielding the prototypes the first one is finished and I am pleased with it so far the specifications shielded are Inductance 707 uh resistance 9.98 ohms shield to coil capacitance is 81.2 pf I like the carbon to paper shielding but it is a bit fiddly to apply here are some pictures for your information and it looks like SRF will be above 500 KHz.

Regards, Ian.

Great work Ian, how long did it take you to assemble..?

Hi Muntari I applied the shielding to the second coil today and it virtually took all day so it is not quick but this one turned out a bit neater I will measure the coil to shield capacitance tomorrow.

Aziz yes now the fun starts with coax I will have to see what I can get for my configuration I only need 1400 mm so we will see.

Regards, Ian. ::62::
Thanks Ian, do you apply the carbon to a adhesive backed cardboard or paper?
Made my little tool up for creasing the spiral pattern tonight, purchased some more foamed PVC on way home, had an early dinner, out yo the shed started Cnc up zeroed everything, about yo push the start button, then son phones and wants me to take him to look at 4wd about 2 hrs drive away....so maybe over weekend I can try the creaser out... Will post some photos of the test.



Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Friday February 23 2018 14:56:36 AEDT PM
Hi Muntari,

I used a brown paper backed white paper almost like wall paper from IKEA and glued it on, self adhesive would be a better option the bad news I did the self resonance tests today using a piece of coax I had hanging around the coax measures 113.7 pf and the self resonance of the coils with shielding and coax are 361 KHz and 353 KHz so too low I think.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 23 2018 15:29:54 AEDT PM
  
Hi Muntari,

I used a brown paper backed white paper almost like wall paper from IKEA and glued it on, self adhesive would be a better option the bad news I did the self resonance tests today using a piece of coax I had hanging around the coax measures 113.7 pf and the self resonance of the coils with shielding and coax are 361 KHz and 353 KHz so too low I think.

Regards, Ian. ::62::

Hi Ian,

Thanks for the info, that's disappointing for you on the capacitance but perhaps with some other coax it can be lowered.
I'm back in the workshop over weekend to produce a coil of similar size so it will be interesting to see the Cp on that with shielding.

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday February 23 2018 15:36:42 AEDT PM
Hi all,

So I made my creasing tool up last night and didn't get to use it as explained in earlier post but that gave me time to think.
Anyways, I was looking for a tool anyone could get a hold of to help put together a spiral cutter, then remembered the good old pipe cutter.

The creasing wheels are essentially the same type of thing only way more expensive.... so had a look at el cheapo Bunnings stuff and this is what I found.

https://www.bunnings.com.au/craftright-32mm-tube-and-pipe-cutter_p4902185

Perfect for the job with a few mods  ::62::

Its only the wheel and shaft assembly we need...maybe a little bit of lathe work so it fits into cnc spindle

More on this later but Ill grab one on the way home tonight and butcher it and try.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Alex on Friday February 23 2018 19:11:36 AEDT PM
Great work guys and thanks for the effort your putting in. Regards to the coax .Would a twisted pair feed line not be as good as a coax and why . thanks


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday February 23 2018 19:28:02 AEDT PM
  
Hi Muntari,

I used a brown paper backed white paper almost like wall paper from IKEA and glued it on, self adhesive would be a better option the bad news I did the self resonance tests today using a piece of coax I had hanging around the coax measures 113.7 pf and the self resonance of the coils with shielding and coax are 361 KHz and 353 KHz so too low I think.

Regards, Ian. ::62::

Hi Ian,

throw that coax cable out of the window.  ::419::

My relative thin oscilloscope cable (4 mm diameter, 2.07 m length) has even 73 pF for the whole lenght and connectors.
Please take a look at high impedance coax cables. Don't use 50 / 75 Ohm coax cables.
As deemon proposed, a cheap oscilloscope cable could also be used for this purpose.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday February 23 2018 19:29:41 AEDT PM
  
Great work guys and thanks for the effort your putting in. Regards to the coax .Would a twisted pair feed line not be as good as a coax and why . thanks

Hi Alex,

a twisted pair cable would have more capacitance. And has no shielding.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday February 23 2018 20:35:19 AEDT PM
Hi all,

I have analysed my sound card impedance meter further.
Most measurement errors come from the inbalance of the left/right input channels. And there is a phase offset error at high test frequencies.

So I have to implement a calibration function into my measurement software before I can make any measurements with it.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday February 23 2018 21:51:05 AEDT PM
What is considered too high a value of capacitance for the cable, I retested a 1200MM twisted pair with PE insulation striped from a cat5 cable and its 56PF. (DE-5000)

If the twisted pair was put into heat shrink wrap, or 3MM  PE cable spiral wrap and then put inside the outer braid from some coax for a shield ,
whats wrong with that ?,

the twisted pair also adds about 20uH to the total inductance

I only need 1000MM for my testing so the  capacitance would be even lower at that length.

Muntari and IBgold great ideas on your projects


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Friday February 23 2018 22:00:51 AEDT PM
  


If the twisted pair was put into heat shrink wrap, or 3MM  PE cable spiral wrap and then put inside the outer braid from some coax for a shield ,
whats wrong with that ?,


Probably it is a little complicated way.

Then it is better to use two shielded parallel cable and get way lower inter-wire capacitance.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday February 23 2018 22:03:01 AEDT PM
  
What is considered too high a value of capacitance for the cable, I retested a 1200MM twisted pair with PE insulation striped from a cat5 cable and its 56PF. (DE-5000)

If the twisted pair was put into heat shrink wrap, or 3MM  PE cable spiral wrap and then put inside the outer braid from some coax for a shield ,
whats wrong with that ?,

the twisted pair also adds about 20uH to the total inductance

I only need 1000MM for my testing so the  capacitance would be even lower at that length.

Muntari and IBgold great ideas on your projects

Hi 6666,

making a simple low capacitance shielded coax cable isn't that difficult. I will show this how to do it soon.
The only drawback is, that the cable may not be bendt too much. And it is quite thick (up to 8-10 mm diameter).
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday February 24 2018 00:10:55 AEDT AM
  
Great work guys and thanks for the effort your putting in. Regards to the coax .Would a twisted pair feed line not be as good as a coax and why . thanks

Hi Alex,

Thanks, I think we are all getting something out of this thread, so that's a good thing ::62::

Probably a little too much capacitance in twisted pairs and best to be shielded.

There are some good low C coax cables out there but they can be very expensive and some not that robust for the rough and tumble of field work.
I have a couple requests into some manufactures of scope probe leads to see if it can be purchased in short runs but so far only one has responded..will post the info if anything eventuates.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday February 24 2018 00:17:28 AEDT AM
  
Hi all,

I have analysed my sound card impedance meter further.
Most measurement errors come from the inbalance of the left/right input channels. And there is a phase offset error at high test frequencies.

So I have to implement a calibration function into my measurement software before I can make any measurements with it.

Cheers,
Aziz


Hi Aziz,

Hope you can sort it soon.
As a matter of interest, what sound card are you using?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday February 24 2018 00:26:55 AEDT AM
  
What is considered too high a value of capacitance for the cable, I retested a 1200MM twisted pair with PE insulation striped from a cat5 cable and its 56PF. (DE-5000)

If the twisted pair was put into heat shrink wrap, or 3MM  PE cable spiral wrap and then put inside the outer braid from some coax for a shield ,
whats wrong with that ?,

the twisted pair also adds about 20uH to the total inductance

I only need 1000MM for my testing so the  capacitance would be even lower at that length.

Muntari and IBgold great ideas on your projects

Hi 6666,

Thanks, it's been an interesting thread.

Good to see you getting some use out of that de 5000 already ????

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday February 25 2018 00:05:14 AEDT AM
Hi All,

So I did some testing with my prototype creasing wheel for making spiral formers with foamed PVC and XPS.

Pictures show how it went. The Craftright pipe cutter from Bunnings worked Ok with a bit of hacking

I learnt a few things,

1) It will work but you must use a trailing or drag knife style setup
2) The wheel diameter could be smaller and width a tad thinner (for smaller coils)
3) Foamed PVC can be pressed cold
4) The material is not uniform in thickness, the stuff I have from Bunnings (Palfoam) ranges from 5.5 to 6.2mm
5) I will make a purpose built attachment that bolts onto my Z Axis frame instead of spindle
6) Using this method rather than milling, the machining time went from 45 minutes to 15.

Question I have...How much has the dielectric constant changed by compressing the material?

More later

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday February 25 2018 00:26:34 AEDT AM
Hi All,

Here is the chop down of the Pipe cutter (only require the shaft and wheel assembly)

There was  little bit of lathe work to remove thread and bring shaft down to 6 mm collet size but in the final version, you wont need to do that.

The locking nut was simply some of cut off from original pipe cutter.

I will write up a complete assembly and parts etc but for now just some photos.



Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Sunday February 25 2018 01:11:59 AEDT AM
  

6) Using this method rather than milling, the machining time went from 45 minutes to 15.


Super, and no milling residue this way.

Still have no idea how you solve your spiral CNC machining project. Anyway great work.


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Sunday February 25 2018 09:57:19 AEDT AM
Great invention Muntari .


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday February 25 2018 10:39:52 AEDT AM


Hi WM6,

Yes, I'm going to tweak a few things to make it even faster.

I'll draw up some plans for a simple spiral cutter once I've done some test coils.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday February 25 2018 10:50:04 AEDT AM
  
Great invention Muntari .

Hi 6666,

Thanks, I am going to add another part to the cutter assembly which will carry a spool of wire and feed it into the path of another narrow roller which will press the wire into groove.

If this works as expected, I'll transfer this design to the small spiral cutter design.
Looking at that pipe cutter I purchased from Bunnings, the body is cast alloy and has a pressure adjusting knob. I'm thinking of using that complete section on the little spiral cutter project as you could manually adjust depth of cut.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Sunday February 25 2018 22:51:23 AEDT PM
Hi all,

regarding the oscilloscope cables:
We can't use them. Absolutely no go!
The DC resistance is way too much (>200 Ohm).

Let's look, how my custom made coax cable goes.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday February 25 2018 22:57:40 AEDT PM
Hi All,

Well it seems XPS does not like the creasing wheel, or the 1mm end mill bit at any depth of cut, it just flakes away so I wont go any further with that material for this type of former. It cuts fine with larger ball mill ~6mm though so Ill just use it as the shield spacing material only.

Oh, on the foamed PVC, I noticed some odd patches on the sheet that were not machining well, its like the material was not quite as dense in some places.
Its just something to watch out for, I mean, its still usable but I'll contact the manufacturer to check if it was just a dodgy sheet.

Ok, also made a simple conical bit out of a broken 6mm end mill to see if i could drag it through the foamed PVC.
Well it worked quite good too, in fact I like it better than the creasing wheel (in its current form). So another option.

Basically I drag it through in 1.5mm passes and have the spindle turning at about 400rpm which just warms the material enough.

Photos show the set up.

I started on the large 18" former and coil arrangement tonight see last photo.
Will continue on tomorrow night and post some more photos.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday February 25 2018 23:25:30 AEDT PM
Hi All,

Here is a close up photo of results using the simple conical bit creasing / Drag tool


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Sunday February 25 2018 23:58:09 AEDT PM
Good work, Muntari again.

What if instead of conical bit try to use heated tip of soldering iron at proper heat and speed?


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Monday February 26 2018 00:21:33 AEDT AM
  
Hi All,

Here is a close up photo of results using the simple conical bit creasing / Drag tool


Cheers

Muntari

This is very encouraging and relatively simple


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 26 2018 11:11:35 AEDT AM
  
Good work, Muntari again.

What if instead of conical bit try to use heated tip of soldering iron at proper heat and speed?

Hi WM6,

Thanks, the problem with this material is the fumes, they are pretty toxic so melting is probably not a good idea for that reason, other than that it would work.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 26 2018 11:19:29 AEDT AM
  
  
Hi All,

Here is a close up photo of results using the simple conical bit creasing / Drag tool


Cheers

Muntari

This is very encouraging and relatively simple

Hi 6666,

Yes, I'm liking this more than the creasing wheel, any HSS bit can be ground with a short cutting end.
Being short allows for higher feed rate and less likely to snap the tip. I used 6mm as I have plenty of worn endmills . I will play around with best tip shape, probably slightly steeper draft than that shown.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday February 26 2018 23:44:18 AEDT PM
Hi All,

Here are a couple of photos of the 464 mm TX / RX former.

Used a broken 6mm end-mill and machined a conical 1.2 mm diam end on to it (about 5 mm length)

2 Passes at 1mm  (1.5mm was too much) If you look at top photo and top and bottom and center section you will notice some rough areas.
The material looks like it had some air pockets, not sure but eased off on the depth per pass and it went fine.

Final depth of spiral groove = 2mm

6mm End-mill used to cut the inner and outer profiles

I will put some turns on it and post some pics of those results.

The final former will be machined from 3mm Foamed PVC for 2 reasons.
1) To drop some weight
2) It allows another sheet of 3mm foamed PVC  or 12mm XPS to be glued onto winding side of former to encase those winding's
I am also hoping to decease the number of turns on both RX and TX winding but that will depend on shielding.

More later

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday February 27 2018 00:39:58 AEDT AM
Hi all,

I have made my own coax cable for the RX coil. It is made out of 28 AWG ribbon cable, where the insulation has been removed for both inner core and drain wire. The wire consists of 5 strands of tinned copper wire.

Length: 1.44 m (4.72 ft)
Capacitance: 44 pF
Rs = 0.5 Ohm (DC resistance)
O.D. = 8 mm
Shielding: graphite paper wrap with drain wire

Capacitance per unit length:
30.6 pF/m or
9.3 pF/ft


Not bad for the first time. I'm sure, I can make it lower capacitance next time and I will show you, how to make it.
 ::62::

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Tuesday February 27 2018 08:53:40 AEDT AM
Sounds good Aziz

be interested to see how you made the Shielding: graphite paper wrap with drain wire


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 27 2018 09:58:11 AEDT AM
Hi Aziz,

Interesting way of doing it, good numbers too, looks promising, thanks for sharing.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Tuesday February 27 2018 14:28:18 AEDT PM
"graphite paper wrap"? Forget. It is about cable shielding not coil. Cable should be flexible or it is of no practical use.


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday February 27 2018 16:33:34 AEDT PM
My coils are on hold as I can not source any of the coax's as suggested here in Australia I have made my own coaxes but can not get the capacitance anywhere low enough for what we require.

Muntari, that is a pain that you have trouble with the XPS  I was going to see if you could cut me a former but with my 10 mm XPS I will have to see what I can do on the router table  but means I will have to set up to do each each winding to each side can you get 2 mm mill cutters with a 6 mm shaft.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 27 2018 17:04:31 AEDT PM
  
My coils are on hold as I can not source any of the coax's as suggested here in Australia I have made my own coaxes but can not get the capacitance anywhere low enough for what we require.

Muntari, that is a pain that you have trouble with the XPS  I was going to see if you could cut me a former but with my 10 mm XPS I will have to see what I can do on the router table  but means I will have to set up to do each each winding to each side can you get 2 mm mill cutters with a 6 mm shaft.

Regards, Ian. ::62::

Hi Ian,

The XPS I had left was from Bunnings and used for insulation, I don't have the Ikea XPS and was planning to drop by to grab some to see if it was just the material, so I will do that and try. No problems cutting a former for you if it works :-)

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday February 27 2018 20:18:15 AEDT PM
  
My coils are on hold as I can not source any of the coax's as suggested here in Australia I have made my own coaxes but can not get the capacitance anywhere low enough for what we require.
..
Regards, Ian. ::62::

Hi Ian,

the ML detectors might still work even there is a large capacitance on the coil. They might have implemented the negative capacitance converter (NIC, negative impedance converter) in the front-end.
See the patent application:
https://patents.google.com/patent/US9547065

We could still try out the coil.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 27 2018 21:29:20 AEDT PM
  
My coils are on hold as I can not source any of the coax's as suggested here in Australia I have made my own coaxes but can not get the capacitance anywhere low enough for what we require.

Muntari, that is a pain that you have trouble with the XPS  I was going to see if you could cut me a former but with my 10 mm XPS I will have to see what I can do on the router table  but means I will have to set up to do each each winding to each side can you get 2 mm mill cutters with a 6 mm shaft.

Regards, Ian. ::62::

Sorry Ian, I misread the last part of your post...... Yes you can get 6mm shaft end-mill cutters in 2 mm,  in fact right down to  0.5 mm (reliable ones that is).

Let me try another couple of tricks with the XPS and see what I can come up with.

Is it 2 mm spiral grooves you were wanting?

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday February 27 2018 23:52:30 AEDT PM
Hi All,

Here are some photos of the 18" coil former with full windings.

Note the turns will be reduced  but I wanted to see approx values.

TX wire = 0.56 mm 40 turns
RX wire = 0.4 mm  54 turns
Inter-wire spacing =1.5mm

There were some weird sections in the material that were softer than other areas and you can see from the photos at top and bottom (outer turns) where its a bit rough. Another sheet machined the same way did not have this problem...anyways, it still wound ok, just looks rough. I will super glue those wire sections

Will also try and get to measure SRF and capacitance tomorrow and post results

More later

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday February 28 2018 00:33:53 AEDT AM
Looks great.
No reason to complain.
In any case it should be epoxy fixed (best with some sort of textile armature).
Hot glue not suit well here, cause it softened at warm wetter and change coil parameters..


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 28 2018 09:39:28 AEDT AM
  
Looks great.
No reason to complain.
In any case it should be epoxy fixed (best with some sort of textile armature).
Hot glue not suit well here, cause it softened at warm wetter and change coil parameters..

Thanks WM6, yeah, it's not really a complaint but I do need to find out why it ripped up like it did, don't want that happening all the time ::62::

The windings will be glued into place and then encased between 2 sheets of 12 mm XPS.
It won't take much to fill the grooves and it will be  a low dielectric constant filler

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 28 2018 15:28:30 AEDT PM
Hi All,

Ok did some quick SRF checks of the coils with no shield and we have:

Total wound coil weight  = 597 grams , Former material  = Foamed PVC  (manufacturer = Palram )

TX = 417 kHz  Inductance = 1110 uH  ,  Cp = 131 pF  Wire = enameled  copper 0.56 mm ,  Inter-wire spacing = 1.5 mm  , Groove depth 2 mm

RX = 521 kHz   Inductance = 750 uH   ,  Cp = 124 pF  Wire = enameled copper 0.4 mm  ,    Inter-wire spacing = 1.5 mm  , Groove depth 2 mm

More tests later tonight.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday February 28 2018 16:55:50 AEDT PM
Hi Aziz,

When I get some coax I can use I will do a test with the GPX and see how it goes.

Muntari,
This coil I am thinking about will be a 9 segment spider with the grooves evenly at about 5 mm centers width to suit the Litz I am sourcing 1.6 mm may do it the former will be 10 mm thick with grooves evenly on both sides for bonding your XPS try Sikabond Foam Fix it is a foam adhesive I spray it on one side spread it evenly and press together with weight on it it foams up and fills any gaps I leave mine for about three hours ( Erata leave with weight on for 24 Hours the ones I just finished expanded after 3 hours so play it safe ) then take the weight off it is a bit fiddly and you have to work reasonably fast but it does the job and will fix the wires permanently in place.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 28 2018 17:06:14 AEDT PM
Hi Ian,

Thanks for the information on your planned coil, I'll see what I can do regards machining the grooves, the former shape, is easy enough. Will work on some test pieces and let you know how it goes. Ill try that Sikabond too

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday February 28 2018 17:16:32 AEDT PM
 ::05::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday February 28 2018 21:27:18 AEDT PM
Hi Muntari & Ian,

it seems, that the parasitic coil capacitances (coil interwire, coil shielding, coax cabling, etc.) are screwing up our desired goal.
We have to reduce the RX coil inductance as a consequence of this fact.
Next RX coil inductance range:
400 µH to max. 500 µH.

Let's make our life a bit easier.

I think, the detector should have enough RX gain setting margin.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday February 28 2018 23:57:15 AEDT PM
Hi All,

Here is the adjusted turns ratio for the 18" TX RX coil

Ran the CNC over the grooves again with 1 mm bit then rewound

The SRF is much better after removing quite a few turns and seating the wire better.

Photo attached shows the changed turns and position.

TX inductance = 328 uH , Turns = 20 , DCR = 1.7 , SRF = 1.39 MHz,   Cp = 30 pF ,  Wire = enameled copper 0.56mm , Inter-wire spacing = 1.5 mm  , Groove depth 2 mm

RX inductance = 640 uH , Turns = 48 , DCR = 5.9 , SRF = 1.09 MHz,   Cp = 41 pF ,  Wire = enameled copper 0.38mm , Inter-wire spacing = 1.5 mm  , Groove depth 2 mm

I am pleased with the result now.

Next will come the XPS spacer and shielding then I'll do the SRF again.

Aziz, I think this will work, I just had to figure out some build issues.

I'll play around with different wire sizes later

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday March 1 2018 00:07:51 AEDT AM
Hi Aziz,

I will finish this coil off first and then look at the reductions in inductance if still required

Like you say,  it will depend on shield and cable capacitance but lets see how this one goes.

The Next formers will be straight out spiral from inside to out no gaps, this will allow better and finer adjustment / placement between TX RX windings .

I did it the way shown to allow separate shielding, which I think is the best way, Aziz, Ian, what are your thoughts?

I will have to get some more XPS, hopefully tomorrow, if I get time.

Will post findings

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday March 1 2018 08:31:20 AEDT AM
Looks good  ::419::


Title: Re: The need for big deep gold detectors.
Post by: freds on Thursday March 1 2018 11:43:07 AEDT AM
  
Hi Aziz,

I will finish this coil off first and then look at the reductions in inductance if still required

Like you say,  it will depend on shield and cable capacitance but lets see how this one goes.

The Next formers will be straight out spiral from inside to out no gaps, this will allow better and finer adjustment / placement between TX RX windings .

I did it the way shown to allow separate shielding, which I think is the best way, Aziz, Ian, what are your thoughts?

Well done to all who have contributed....when the average (with skills) diy person can construct these coils it will be a GREAT day
I think that time is getting close
Once thanks again
Fred

I will have to get some more XPS, hopefully tomorrow, if I get time.

Will post findings

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday March 1 2018 12:17:44 AEDT PM
  
  
Hi Aziz,


Well done to all who have contributed....when the average (with skills) diy person can construct these coils it will be a GREAT day
I think that time is getting close
Once thanks again
Fred


Hi Fred,

It goes to show that forum projects can work, when egos are left at the door, no money is involved and everyone is civil.
I don't begrudge manufactures selling their wares but at the same time those who love this hobby and in some cases earn a bit of cash from it, should not be hampered by the BS of patenting. We simply want to go about enjoying what we do.

Anyways, glad you are enjoying the thread and hopefully soon, you can go build one to suit, we will, as a group, share as much info as we can on how to go about it.
Mind you, even after 35 odd years of playing with these things, I'm still learning too ::62::

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday March 1 2018 20:24:58 AEDT PM
  
Hi All,

Here is the adjusted turns ratio for the 18" TX RX coil

Ran the CNC over the grooves again with 1 mm bit then rewound

The SRF is much better after removing quite a few turns and seating the wire better.

Photo attached shows the changed turns and position.

TX inductance = 328 uH , Turns = 20 , DCR = 1.7 , SRF = 1.39 MHz,   Cp = 30 pF ,  Wire = enameled copper 0.56mm , Inter-wire spacing = 1.5 mm  , Groove depth 2 mm

RX inductance = 640 uH , Turns = 48 , DCR = 5.9 , SRF = 1.09 MHz,   Cp = 41 pF ,  Wire = enameled copper 0.38mm , Inter-wire spacing = 1.5 mm  , Groove depth 2 mm

I am pleased with the result now.

Next will come the XPS spacer and shielding then I'll do the SRF again.

Aziz, I think this will work, I just had to figure out some build issues.

I'll play around with different wire sizes later

Cheers

Muntari


Hi Muntari,

this coil could really work. The interwire capacitance is low enough this time.
But your first measurement shocked me.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday March 1 2018 20:38:28 AEDT PM
  
Hi Aziz,

I will finish this coil off first and then look at the reductions in inductance if still required

Like you say,  it will depend on shield and cable capacitance but lets see how this one goes.

The Next formers will be straight out spiral from inside to out no gaps, this will allow better and finer adjustment / placement between TX RX windings .

I did it the way shown to allow separate shielding, which I think is the best way, Aziz, Ian, what are your thoughts?

I will have to get some more XPS, hopefully tomorrow, if I get time.

Will post findings

Cheers

Muntari

Hi Muntari,

yes, separate shielding is the way to go. Whereas the TX coil part isn't really a big issue as it is not that critical as the RX coil part.

I will investigate how to reduce the shielding capacitance further without increasing the distance gap to the coil windings. We don't need a perfect shielding functionality. The shielding should keep out the stray capacitance effects only. Indeed, there are some interesting ways to reduce heaps of shielding capacitance.
I have to do some experiments first. Before I can do it, I have to finish my sound card impedance meter.
BTW, my impedance meter is getting more and more accurate. I just have to buy some precision resistors yet to start with measurements.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday March 1 2018 22:15:17 AEDT PM
  
  
Hi All,

Here is the adjusted turns ratio for the 18" TX RX coil

Ran the CNC over the grooves again with 1 mm bit then rewound

The SRF is much better after removing quite a few turns and seating the wire better.

Photo attached shows the changed turns and position.

TX inductance = 328 uH , Turns = 20 , DCR = 1.7 , SRF = 1.39 MHz,   Cp = 30 pF ,  Wire = enameled copper 0.56mm , Inter-wire spacing = 1.5 mm  , Groove depth 2 mm

RX inductance = 640 uH , Turns = 48 , DCR = 5.9 , SRF = 1.09 MHz,   Cp = 41 pF ,  Wire = enameled copper 0.38mm , Inter-wire spacing = 1.5 mm  , Groove depth 2 mm

I am pleased with the result now.

Next will come the XPS spacer and shielding then I'll do the SRF again.

Aziz, I think this will work, I just had to figure out some build issues.

I'll play around with different wire sizes later

Cheers

Muntari


Hi Muntari,

this coil could really work. The interwire capacitance is low enough this time.
But your first measurement shocked me.

Aziz

Hi Aziz,

Yes the readings suprised me too, I initially thought my test bench was faulty but it wasn't that.
The problem turned out to be a couple of things, the creasing tool was cutting too deep on each pass and compacting the foam and the other problem was using wrong gauge wire for RX. I used .42mm instead of the .38mm. Of course the damaged areas on the Tx outer grooves are not  used now either , I think they added to the problem
The over compressed grooves would have increased the dielectric constant and coupled with slightly higher wire gauge the Cp was higher, anyways that's what I believe caused it.
Less turns helps too
Both operator error  ::10 ::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday March 1 2018 22:29:29 AEDT PM
Hi Aziz,

Thanks for confirming that, will be interesting to see what you come up with.

I have used a few different shield sprays in the past and both Nickel and Carbon types worked easily without dropping the SRF much at all.

One in particular called Super Shield when sprayed in a branch like pattern onto a spaced disc works really well, as does complete coverage.

I have also done this with the little 200mm test coils and it appears to be fine on the spiral.

I'll post photos and readings once I set up for the final assembly.

Will also try anything you come up with

Btw, I have found by far the biggest culprit with Cp being too high....the glues and resins used in construction of the coils.

If done right, wires embedded into grooves and spaced apart help with rigidity, reduce coil weight, use less resin and we end up with less Cp.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 2 2018 13:55:06 AEDT PM
Hi All,

Here is an overlay photo showing the proposed new position of TX RX windings.
You can compare to original

It falls within Aziz's design boundaries, maximizes the size of RX / TX loop radius and removes a lot of weight from the former.

I will machine one over the weekend and see how we go.

This will be after I assemble the shields to this first set of windings, then I'll post results.
I'm going to try Ian's method with using Sikabond foam glue as it sounds very good.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Friday March 2 2018 16:37:22 AEDT PM
Muntari,

Warning use the minimum amount of foam I spray it on and use an off-cut of XPS to spread it as thin as I possibly can then put together and weight down be very careful as it tends to try and slide sideways and too much foam and it will bulge so the trick is as thin a coating as you can because it does expand as you spread it out you will see it grow I try for less than .5 mm coat less is better.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 2 2018 16:41:20 AEDT PM
  
Muntari,

Warning use the minimum amount of foam I spray it on and use an off-cut of XPS to spread it as thin as I possibly can then put together and weight down be very careful as it tends to try and slide sideways and too much foam and it will bulge so the trick is as thin a coating as you can because it does expand as you spread it out you will see it grow I try for less than .5 mm coat less is better.

Regards, Ian. ::62::

Hi Ian,

Ok, thanks for the heads up, its good to be aware of the gotchas  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 2 2018 22:21:07 AEDT PM
Hi All,

So here I am waiting while the CNC machines the next former and I got to thinking.
Has anyone tried using polyethylene fishing line as a wire spacing material for spiral coils?

You could use a bobbin type former from 3 layers of XPS made the same as usual construction for winding flat spiral but feed in both wire and fishing line through a simple guide.

There is plenty of different diameter polyethylene line available and at very cheap prices..

Any takers?

anyways, back to the machine minding for me  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday March 2 2018 23:10:56 AEDT PM
Hi all,

oh well, the reasonable LCR meters are quite expensive. I have to pay out at least 220 bucks for PEAKTECH 2170, which would do for me. The cheaper ones are pure waste of money. DE-5000 isn't available here.
Ok, I will upgrade my sound card LCR meter further. Open/Short calibration is the next issue.

BTW, I can measure stray capacitance effects quite easily with high resolution (+/-0.01 pF). This will help to develop a low capacitance shielding. It would be nice to reduce the coil shielding capacitance into half amount or even more.

I haven't built the next coax cable yet. But the inner cable core consists of XPS pieces ("pearls") and air. All the XPS core pieces (5x5 mm width/height, 10-15 mm length) are lined up like pearls on the inner core wire. These XPS pieces are pierced at the center line with a needle and lined up directly to the inner core wire. After lining up all the XPS piceses, they will be (super) glued with the inner core wire (every 10 - 15 cm) to avoid movement of the XPS pieces. It is then wound up with a PE spiral wrap (0.6 mm thick for 5 - 20 mm diameter wraps) and fixed with adhesive tape. Then drain wire + graphite paper stripe shielding wrapped around. Then insulation tape. That's all.
I'll show you some pictures when I have more time.
 ::62::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday March 2 2018 23:15:50 AEDT PM
  
Hi All,

So here I am waiting while the CNC machines the next former and I got to thinking.
Has anyone tried using polyethylene fishing line as a wire spacing material for spiral coils?

You could use a bobbin type former from 3 layers of XPS made the same as usual construction for winding flat spiral but feed in both wire and fishing line through a simple guide.

There is plenty of different diameter polyethylene line available and at very cheap prices..

Any takers?

anyways, back to the machine minding for me  ::62::

Cheers

Muntari
Yes a similar experiment has been tried with fishing line , I think it was 100lB mono filament,  it was claimed to work,  I enquired about a few more details but no reply

Here is the quote
Quote
I have tried the monofilament idea (was mine in the first place) to wind a spiral coil using copper wire then 100lbs monofilament along side it. Better still, use the Rx coil and wind the two side by side for fantastic coupling. Even BETTER is to overwind (more turns in the Rx than the Tx) the Rx for a transformer type action.

Better than nylon, use FLOUROCARBON, it has a much better dielectric coefficient than monofilament. Try the FlouroCarbon with the above multi core wound in a spiral or basket weave and see how that works.


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday March 2 2018 23:17:31 AEDT PM
  
Hi all,

oh well, the reasonable LCR meters are quite expensive. I have to pay out at least 220 bucks for PEAKTECH 2170, which would do for me. The cheaper ones are pure waste of money. DE-5000 isn't available here.
Ok, I will upgrade my sound card LCR meter further. Open/Short calibration is the next issue.

BTW, I can measure stray capacitance effects quite easily with high resolution (+/-0.01 pF). This will help to develop a low capacitance shielding. It would be nice to reduce the coil shielding capacitance into half amount or even more.

I haven't built the next coax cable yet. But the inner cable core consists of XPS pieces ("pearls") and air. All the XPS core pieces (5x5 mm width/height, 10-15 mm length) are lined up like pearls on the inner core wire. These XPS pieces are pierced at the center line with a needle and lined up directly to the inner core wire. After lining up all the XPS piceses, they will be (super) glued with the inner core wire (every 10 - 15 cm) to avoid movement of the XPS pieces. It is then wound up with a PE spiral wrap (0.6 mm thick for 5 - 20 mm diameter wraps) and fixed with adhesive tape. Then drain wire + graphite paper stripe shielding wrapped around. Then insulation tape. That's all.
I'll show you some pictures when I have more time.
 ::62::
Cheers,
Aziz

I got my DE-5000 with both probes  from Japan via ebay


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday March 2 2018 23:22:07 AEDT PM
  
Hi All,

Here is an overlay photo showing the proposed new position of TX RX windings.
You can compare to original

It falls within Aziz's design boundaries, maximizes the size of RX / TX loop radius and removes a lot of weight from the former.

I will machine one over the weekend and see how we go.

This will be after I assemble the shields to this first set of windings, then I'll post results.
I'm going to try Ian's method with using Sikabond foam glue as it sounds very good.

Cheers

Muntari

Hi Muntari,

the coil is looking very nice. Well done.
You can use super glue with XPS coil formers. But not much (less is more). Only a few lines of super glue will fix the windings and shielding spacers.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday March 3 2018 00:31:30 AEDT AM
Hi Aziz,

That is a pity you couldn't get a DE-5000.

Will be good to see your coax too.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday March 3 2018 00:35:42 AEDT AM
  
  
Hi All,

So here I am waiting while the CNC machines the next former and I got to thinking.
Has anyone tried using polyethylene fishing line as a wire spacing material for spiral coils?

You could use a bobbin type former from 3 layers of XPS made the same as usual construction for winding flat spiral but feed in both wire and fishing line through a simple guide.

There is plenty of different diameter polyethylene line available and at very cheap prices..

Any takers?

anyways, back to the machine minding for me  ::62::

Cheers

Muntari
Yes a similar experiment has been tried with fishing line , I think it was 100lB mono filament,  it was claimed to work,  I enquired about a few more details but no reply

Here is the quote
Quote
I have tried the monofilament idea (was mine in the first place) to wind a spiral coil using copper wire then 100lbs monofilament along side it. Better still, use the Rx coil and wind the two side by side for fantastic coupling. Even BETTER is to overwind (more turns in the Rx than the Tx) the Rx for a transformer type action.

Better than nylon, use FLOUROCARBON, it has a much better dielectric coefficient than monofilament. Try the FlouroCarbon with the above multi core wound in a spiral or basket weave and see how that works.


Hi 6666,

Thanks for that info, its interesting to see how that was done.

I was more thinking of laying it alongside the copper for ease of construction, its good to see how other folk think too.
My thinking was that it may be another option for the builders that don't want to go down the path I have taken.

Thanks for your input.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday March 3 2018 00:41:57 AEDT AM
  
  
Hi All,

Here is an overlay photo showing the proposed new position of TX RX windings.
You can compare to original

It falls within Aziz's design boundaries, maximizes the size of RX / TX loop radius and removes a lot of weight from the former.

I will machine one over the weekend and see how we go.

This will be after I assemble the shields to this first set of windings, then I'll post results.
I'm going to try Ian's method with using Sikabond foam glue as it sounds very good.

Cheers

Muntari

Hi Muntari,

the coil is looking very nice. Well done.
You can use super glue with XPS coil formers. But not much (less is more). Only a few lines of super glue will fix the windings and shielding spacers.

Cheers,
Aziz

Hi Aziz,

Thanks, getting there slowly.
Yes I did note where you used super glue with XPS might be useful to tack wires into place before encapsulating with the Sikabond Foam Fix Ian has been using.
Always good to have options.

Here is the latest former version to be cut from 3mm Foamed PVC.

This version which will be much less weight. I will post sizes tomorrow.

Will machine in the morning.

More later

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Saturday March 3 2018 08:46:00 AEDT AM
Quote
I was more thinking of laying it alongside the copper for ease of construction, its good to see how other folk think too.
My thinking was that it may be another option for the builders that don't want to go down the path I have taken.

Hi yes there has been some brief discussion about winding in parallel a flat coil with fishing line and wire, the problem is how to stick them to a backing board without the wire going rats nest, also another idea was winding figure 8 speaker wire, then removing one wire to leave the spacing between wires, that would be brilliant if we could get it to stick and work.. But the fishing line and wire in parallel would probably be easier to just glue and forget.   


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday March 3 2018 10:49:30 AEDT AM
  
Quote
I was more thinking of laying it alongside the copper for ease of construction, its good to see how other folk think too.
My thinking was that it may be another option for the builders that don't want to go down the path I have taken.

Hi yes there has been some brief discussion about winding in parallel a flat coil with fishing line and wire, the problem is how to stick them to a backing board without the wire going rats nest, also another idea was winding figure 8 speaker wire, then removing one wire to leave the spacing between wires, that would be brilliant if we could get it to stick and work.. But the fishing line and wire in parallel would probably be easier to just glue and forget.  

Hi 6666,

Yes I was thinking of a very narrow bobbin type former just wide enough for the wire with slots cut on one face for glue or resin and feeding wire fishing line in via a guide very close to former edge.
Once wound, glue into place.
The XPS outer pieces would be 12mm thick the inner may even be thin cardboard to suit wire thickness.
You would maybe need a front and back support for the XPS while winding but I think you could just about get away without them, no big deal if they are needed though.
The advantage woul be a light weight coil and you could spray or paint shielding directly onto former

Thinking on it more, get a 25mm thick XPS sheet  cut to required diameter, put in onto a jig that turns, grab a fine blade saw and cut into centre of side to depth of inner most winding, put some slots on one face and there's your former
Once tested use some glue and Ian's Sikabond foam fix method to seal up slots and around side, then spray the whole assembly with your favourite shield material.

You then have a rigid, light weight winding. It is something that could be done quite easily I think.


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Golddiggerdave on Saturday March 3 2018 11:20:41 AEDT AM
Possible Litz alternative - See:-

TinManPower - YouTube - Tesla BPC from copper ribbon winding jig
used copper foil to wind a coil - large surface area.

.....Dave


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Saturday March 3 2018 11:32:36 AEDT AM
A link would help that guy has tons of videos


Title: Re: The need for big deep gold detectors.
Post by: Golddiggerdave on Saturday March 3 2018 14:07:27 AEDT PM
I have been following this thread and would love to be able to contribute. and because I am electronically challenged I havn't any technical knowledge to share.
BUT if this suggestion helps, then I can feel that I have contributed to something we can all benefit from. If it's a bad idea, File it. I'm still with you.

I've used Plastic plumbing adhesive on insulated speaker cable.
Also "UHU POR" glue is good on some polystyrene.

Great work fellas, I'm on your side. Looking forwad to making my own Super Coil.

Link:
https://www.youtube.com/watch?v=EQR6i0qNt4U 

Or Just Google:-
TinManPower - YouTube - Tesla BPC from copper ribbon winding

That video will be right in the top few.

......   Dave




 


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Saturday March 3 2018 16:05:55 AEDT PM
Hi Muntari and all,

Yes I have wound flat wound coils using this method about 5 years ago or more I used 15 mm Styrofoam and routed a 1.6 mm recess where the Litz wire and Fluorocarbon line went then painstakingly wound the wire and fluorocarbon line super gluing every 30 mm I then glued the other side on it was 13 mm thick overall width ended up 30 mm when bonded then painted the shielding directly onto the Styrofoam did not work bad at all I still have it in my armory.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday March 3 2018 22:01:06 AEDT PM
  
I have been following this thread and would love to be able to contribute. and because I am electronically challenged I havn't any technical knowledge to share.
BUT if this suggestion helps, then I can feel that I have contributed to something we can all benefit from. If it's a bad idea, File it. I'm still with you.

I've used Plastic plumbing adhesive on insulated speaker cable.
Also "UHU POR" glue is good on some polystyrene.

Great work fellas, I'm on your side. Looking forwad to making my own Super Coil.

Link:
https://www.youtube.com/watch?v=EQR6i0qNt4U 

Or Just Google:-
TinManPower - YouTube - Tesla BPC from copper ribbon winding

That video will be right in the top few.

......   Dave




 


Hi Dave,

Thanks for the input, every little idea helps so please keep contributing, you never know, that link may lead to another great idea. Digging around on the Internet and sharing possible alternatives is a good thing.
The copper foil in that width would probably have a lot of capacitance and may not be suitable fir a PI coil BUT. I have never tried it so perhaps it might ::62::

We can add that to the list of possibles unless someone here has already tried it.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday March 3 2018 22:12:58 AEDT PM
  
Hi Muntari and all,

Yes I have wound flat wound coils using this method about 5 years ago or more I used 15 mm Styrofoam and routed a 1.6 mm recess where the Litz wire and Fluorocarbon line went then painstakingly wound the wire and fluorocarbon line super gluing every 30 mm I then glued the other side on it was 13 mm thick overall width ended up 30 mm when bonded then painted the shielding directly onto the Styrofoam did not work bad at all I still have it in my armory.

Regards, Ian. ::62::

Hi Ian,

Thanks for sharing, Funny, I thought you may have tried it ::62::
So it sounds like a very viable alternative for those who would like to experiment I think.
It would be interesting to see what the inductance and Cp is on that coil at some stage.
I think it's great to have different options to achieve the same goals.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday March 4 2018 00:55:17 AEDT AM
Hi All,

So for the fishing line spacer+wire XPS former I was thinking along this path.

As Ian has already given information on his coil at 30mm thick I went with that to start with

30mm thick XPS, 2mm groove as deep as required  and slots on one face as required

Ill try one at some stage but maybe someone else might like to give it a try, I already have plenty to do  ::62::

More later


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday March 5 2018 10:39:00 AEDT AM
Hi All,

I will be increasing the TX wire diam to 1mm and dropping from 20 to 18 turns to reduce the resistance from the current value of 1.5 Ohms.
Then I'll check the SRF and Cp again
The RX will remain the same 44 turns 0.38mm  5.7 Ohms.

Was hoping to cut the latest foamed PVC (3mm thick version) of the former and finish off the test coil over weekend but didn't happen, between family commitments and getting side tracked cleaning out my workshop, time was gone. Next time family or friends ask if they can store gear for "a few weeks" I know what my answer will be  ::08::
It gets to a point where there isn't enough room to operate the machinery safely but people just see floor space and think there's plenty of room. Those of you with adult kids will know where I'm coming from ::62::

Cheers

Muntari





Title: Re: The need for big deep gold detectors.
Post by: IBGold on Monday March 5 2018 16:25:22 AEDT PM
Hi Muntari,

Your 1 mm wire will carry eddy currents hence the need for Litz wire the Litz I will be using for my TX coil has an OD around 1.6 mm and I have ordered the appropriate end mills I am all set up waiting for the wire and end mills to arrive I also took a leaf from your book and made a cutter to put the grooves for the RX coil it is a 6 mm rod cut down so a hacksaw blade fits in with a hole for a 3 mm bolt which holds the blade tight the blade is about 12 mm out of the rod and is shaped as a cutter it is held in the router depth of cut set and the formed manually rotated while cutting the groove the way it is set up it tracks and works fine  so now waiting for wire.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday March 5 2018 17:07:27 AEDT PM
  
Hi Muntari,

Your 1 mm wire will carry eddy currents hence the need for Litz wire the Litz I will be using for my TX coil has an OD around 1.6 mm and I have ordered the appropriate end mills I am all set up waiting for the wire and end mills to arrive I also took a leaf from your book and made a cutter to put the grooves for the RX coil it is a 6 mm rod cut down so a hacksaw blade fits in with a hole for a 3 mm bolt which holds the blade tight the blade is about 12 mm out of the rod and is shaped as a cutter it is held in the router depth of cut set and the formed manually rotated while cutting the groove the way it is set up it tracks and works fine  so now waiting for wire.

Regards, Ian. ::62::

Hi Ian,

Yeah, I was concerned about that 1mm but want to compare against a number of different gauges for TX.
I am trying to steer clear of Litz but if I need to, then I'll go that way.

Great work, glad you got a tool set up for groove cutting, as long as it drags slightly (off center) it will cut fine.
Are you using XPS ?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday March 5 2018 18:43:21 AEDT PM
  
  
Hi Muntari,

Your 1 mm wire will carry eddy currents hence the need for Litz wire the Litz I will be using for my TX coil has an OD around 1.6 mm and I have ordered the appropriate end mills I am all set up waiting for the wire and end mills to arrive I also took a leaf from your book and made a cutter to put the grooves for the RX coil it is a 6 mm rod cut down so a hacksaw blade fits in with a hole for a 3 mm bolt which holds the blade tight the blade is about 12 mm out of the rod and is shaped as a cutter it is held in the router depth of cut set and the formed manually rotated while cutting the groove the way it is set up it tracks and works fine  so now waiting for wire.

Regards, Ian. ::62::

Hi Ian,

Yeah, I was concerned about that 1mm but want to compare against a number of different gauges for TX.
I am trying to steer clear of Litz but if I need to, then I'll go that way.

Great work, glad you got a tool set up for groove cutting, as long as it drags slightly (off center) it will cut fine.
Are you using XPS ?

Cheers

Muntari


Hi Ian, forgot to say, I made a hot wire foam cutter to slice one of the Bunnings 30mm thick XPS sheets as I still haven't got down to IKEA yet, when I do I'll stock up..

The foam cutter was made out of  a guitar "E" string , some aluminium and a couple of ceramic insulators.
The power supply is an old car battery and I made up a PWM circuit to adjust temperature.
I attach it underneath the Cnc X axis , place the XPS on the Y axis moving bed and feed it through the cutter. Will take photos next time I use it, works a treat. ::62::
I'll try to cut a former for you too btw


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday March 6 2018 00:08:02 AEDT AM
Hi all,

oh well, the capacitance meter of my digital multi meter (DMM) isn't quite accurate.  ::406::
The calibration of my sound card LCR meter is somewhat complicated and quite time consuming.
I can calibrate it to 1%/sqrt(10) = 0.32 % accuracy (10 parallel connected 1% resistors to determine the resistor value of my reference resistors).
I can live with that in the meaning time but I want to buy a resonable LCR meter soon.  ::10 ::

In the meaning time:
The most important benefit of my sound card LCR meter is the extreme sensitivity to stray capacitance measurements.
So I can check the efficiency of different coil shielding types.
And I can investigate the interwire coil capacitance and how to reduce it.

It's going to be an interesting stuff..
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday March 6 2018 13:36:03 AEDT PM
  

In the meaning time:
The most important benefit of my sound card LCR meter is the extreme sensitivity to stray capacitance measurements.
So I can check the efficiency of different coil shielding types.
And I can investigate the interwire coil capacitance and how to reduce it.

It's going to be an interesting stuff..
Cheers,
Aziz

Hi Aziz,

Sounds good
Look forward to your findings with the different shielding methods, I'm sure you will come up with a novel approach, keep up the great work!

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday March 6 2018 16:23:54 AEDT PM
Hi Muntari,

Yes the cutter is off center and yes I am using XPS 2 pieces of the IKEA stuff bonded together I spray my cutters router bits and end mills with Teflon spray it stops pick up with that on the blade it cuts with no tearing of the XPS I have done about 1/4 of a new RX spider coil both sides I am running the wires at 2.5 mm centers with no damage so far the beauty of being able to make your own tools.

Aziz, have you had any more thoughts on how we are going to run these coils on the QED Dave did give a hint on how it might be done in his post earlier.

Regards, Ian.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday March 6 2018 21:36:07 AEDT PM
  
..Aziz, have you had any more thoughts on how we are going to run these coils on the QED Dave did give a hint on how it might be done in his post earlier.

Regards, Ian.

Hi Ian,

it is easier to test the coils on ML detectors first.

I hadn't time to look for a good solution for the QED detector.
We just have to cancel the bias current in the (RX) coil caused by the diode overvoltage protection circuit. This bias current is causing a voltage drop and it will be amplified by the front-end amplifier.
It is quite trivial to solve the issue however.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday March 7 2018 00:12:42 AEDT AM
  
Hi Muntari,

Yes the cutter is off center and yes I am using XPS 2 pieces of the IKEA stuff bonded together I spray my cutters router bits and end mills with Teflon spray it stops pick up with that on the blade it cuts with no tearing of the XPS I have done about 1/4 of a new RX spider coil both sides I am running the wires at 2.5 mm centers with no damage so far the beauty of being able to make your own tools.

Aziz, have you had any more thoughts on how we are going to run these coils on the QED Dave did give a hint on how it might be done in his post earlier.

Regards, Ian.

Hi Ian,
That's great news, excellent work, I agree, being able to make your own tools with what you have available or can get readily is such a bonus. It allows one to do things that would otherwise cost a fortune. I have seen so many great ideas from DIY people, some simple some very involved but all doing the job they were intended to do, good ideas don't have to look fancy.

I've been side tracked on a couple of fronts,  replacing the Y axis servo end ballscrew bearing ( part should arrive in a day or so, it's 50mm screw so was expensive should be good for another 10 years then ) my new vacuum former project  ( old one can only do coils up to 350mm) and modification to the CNC hot wire foam cutter attachment.
The latter is almost completed and it will allow easy install / removal of the hot wire bow.
Just have to source a good 10 mm x compression Spring, there a few in the workshop..somewhere  ::62::
Should have it up and running again tomorrow night.
The vacuum former will take a week or so and I'll work on that while the CNC is running off a few coil formers .

I am also interested in the adapting the coils to the QED. I have my old faithful GP 3000 so can start with that but the QED is the one I'm most interested in using.

More later

Cheers

Muntari





Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday March 7 2018 16:38:36 AEDT PM
Hi Muntari,

The RX former is ready for wire that may take a few weeks to get here the XPS from IKEA comes in a pack the sheets are 790 mm x 590 mm 5 mm thick 13 sheets to a pack about $30 per pack part number 803.215.87 give the cashier the number and they will tell you where to pick them up I will be away for a few days cheers.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday March 7 2018 16:52:03 AEDT PM
Hi Ian,

That's good news on finishing your former, glad it worked for you.

Thanks for the info on XPS, Ill contact them.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday March 7 2018 19:51:12 AEDT PM
Hi all,

I have measured my DIY coax cable capacitance with my calibrated sound card LCR meter again.
It is even better:
C = 32.3 pF/144 cm
C = 22.5 pF/m
C = 6.84 pF/ft

I was not able to reduce the coil shielding capacitance further with less effective shielding types.
It isn't possible. It remains to some degree sensitive the stray capacitances. This is going to be critical on conductive and wet grounds. And there would be minimal shielding capacitance savings too (10 - 20%). Another critical part is, that the less effective shielded coil will pickup more EMI noise. So it doesn't make sense.
We have to use thicker coil shielding spacer to reduce the shielding capacitance. Maybe with more air in the coil shielding spacer to reduce the dielectric constant of the shielding spacer material. Or reduce the shielding area of the coil (less windings, more compact windings, thin RX coil wire, ..).

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday March 7 2018 23:39:56 AEDT PM
Hi Aziz and All

That's pretty good figures, well done.

I'm up to the shielding stage on my test coil now but I needed to have more options for spacer thickness, funny you talk about that...

I can get XPS 5mm thick from Ikea, Ian put us on to that and I will get a couple of packs on the weekend  but right across the road I have Bunnings hardware that sell 30mm and 50mm thick XPS for use in insulation.

Its too thick so I decided to make an hot wire foam cutter attachment for the CNC specifically to be able to make spacer material to custom thickness.

I used whatever I have laying around, made some brackets, tapped a few holes, found a spring, then some Bakelite for use as an insulator..that came from a skid plate on the bottom of an old table router, then I just  purchased a roll of stainless steel MIG wire. Don't use mild steel or gasless MIG wire, its too soft and wont retain it's shape once heated..

The power supply is an old car battery/ PWM  but this will be replaced with a 24v switch mode supply and PWM later (steppersonline have the cheapest reliable units)

It's basically a bow with levered spring tension at top, the spring came from an old workbench magnifier, the cable attached to that spring was an old lawnmower throttle cable inner..

I'm trying to use materials everyone can get a hold of at reasonable prices and come up with different ideas that will work for most people.
You don't need a CNC to do it, use same sort of structure I have here but put a skate bearing on the bottom of each bow part, grab a bit of MDF route a couple of tracks for the bearings to run in, set the height of hot wire to suit..or, make it stationary and slowly push the sheet through, just remember to put a weight of some sort on top of foam that way you will get a nice even cut.

I will make another smaller vertical hot wire attachment for use in cutting circles or other patterns...
When I'm not using it, I just remove 2 screws and that's it


Here are some photos.


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 9 2018 00:23:16 AEDT AM
Hi All,

So following on from last night with the foam cutter, here are some photos of the sliced  30mm sheet of XPS cut into 2 x 14mm thick pieces, then  machined into the  top and bottom donut shield pieces followed by a quick dry fit. I could of machined all 4 parts from 1 cut down piece of XPS If not for some tests with foam cutter last night and so the length was reduce by 200mm so not quite long enough.

Overall thickness is 34mm which is fine for testing. Overall diameter = 464mm. I will weigh it tomorrow.

Future versions will be 3mm Former + whatever shield spacing is required, I think it will be around 11mm top and bottom but lets see.
Next up is getting some Sikabond foam glue, Bunnings were out of it the other day so hopefully they will have stock now.
Before I glue the assembly however, I'll make up a gluing  jig from MDF which will basically be a round pocket 464mm diameter and top cover to clamp the assembly in and prevent sideways movement, (Thanks for heads up on that one Ian)
Once assembled I'll spray the shield coating directly onto XPS, I've already done a test with the spray and its fine on the material, there was no pitting of the surface which is good. A fine wire will be stitched into the foam with enough surface area exposed to make good contact. It won't be looped just a wide enough pitch in the stitch to hold it secure, I'll also put some tape on the wire for strain relief.

This has been a lot of work but also enjoyable too and  once the tooling, jigs and process is sorted, future coils will be much much quicker and easier to make.

More later

Cheers

Muntari






Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 9 2018 12:26:37 AEDT PM
Hi All,

Weighed coils and we have combined weight of 669 grams

More later

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Doug on Friday March 9 2018 13:10:34 AEDT PM
  
Hi All,

Weighed coils and we have combined weight of 669 grams

More later

Cheers

Muntari



Superb  work Muntari!
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 9 2018 13:44:50 AEDT PM
Hi Doug,

Thanks, its getting there, I'm searching for some ultra tough thin,light weight material for thermo-forming the shells, something new, simple to use, other than ABS.
I think I have found a good candidate and will post more on that later.
The goal is to have an 18 inch coil with total weight  less than 750 grams, that doesn't leave much headroom on current design but when I drop back to a 3mm former, it shouldn't be a problem.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: mylab on Friday March 9 2018 15:38:11 AEDT PM
I wonder is there any way to run a field test of this coil at an in ground depth test site before all the finishing touches to the coil such as housing etc have been completed as it may not work out as planned for extra depth, if that being the major reason for this type of coil being built?

   


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 9 2018 15:59:38 AEDT PM
  
I wonder is there any way to run a field test of this coil at an in ground depth test site before all the finishing touches to the coil such as housing etc have been completed as it may not work out as planned for extra depth, if that being the major reason for this type of coil being built?

   

Hi Mylab,

That is a good point and is the general idea, yes.

However, I would like to also test one with the QED too and I need to get more detail on the requirements to interface.

I'll be going ahead with coil housings for another coil design I have anyway so the housing is a not really a concern for me and I want to see how it performs with everything included.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 9 2018 16:05:44 AEDT PM
Should have said also, from my own preliminary testing, I am quietly confident there is a number of benefits using this design.
If there isn't, then that will lead to another avenue of investigation.

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 9 2018 16:10:01 AEDT PM
Hi Ian,

Quick question for you, where do you bring your TX/RX wire out on  your coils?
As in all inside?

I would like to keep them in same position you are using for later comparison.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 9 2018 20:54:42 AEDT PM
Hi Ian,

I should be more specific sorry, do you bring your coil wires up through the shield to  the center of the coil or on outer edges of both?

Generally, I take mine straight up through the shield spacer then across to the center area for connection to coax.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday March 10 2018 00:38:08 AEDT AM
Hi All,

Here is a draft version of a coil shield pattern I used some time ago to good effect.

Please note, it is a draft of the 464mm TX shield bottom face shown here and is not fully populated.
There are quite a few more radial leads required.
I have a formula somewhere in my archive but can't remember where.
Aziz may have such a formula but basically, the radials are perpendicular to coil windings.
They are not lines just drawn through the circular axis.
There is another version which is called a star pattern which I used on a PCB coil but I believe this one is more suited.
I will cut a stencil which is easily achievable with this design.
The edges of the coil former (XPS) maybe continued radials or completely covered with shield spray (Aziz?)
I cant even remember where I got the idea from but I'm sure if you did a google search one would come up somewhere  ::62::

Anyways here's the basic idea and please remember, its a draft  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Saturday March 10 2018 16:23:52 AEDT PM
Hi Muntari,

As you usually through the shield spacer to the inside of the coil terminating to coax where convenient in a concentric coil in between the two winding's normally but for the two separate coil versions I have built they both will be inside the coils to suit current Mono TX cable positions.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: autitch on Saturday March 10 2018 22:16:14 AEDT PM
After some painstaking tedious work I’ve managed to document a bunch of measured parameters for a Coiltek DD 14” round coil I decided to sacrifice for the benefit general knowledge.  All inductance readings are measured at 1kHz and all SRF measurements were made using the test circuit as shown in SRF circuit sketch attached.

Test 1:  Complete coil, as is.
                         RX ( pin 1-2)                        TX ( pin 4-5 )
Inductance            500 uh                                   280 uh
Resistance             6.9 Ohms                             0.57 Ohms
SRF                       Not Measurement                 464 kHz

Test 2: Coils was opened and shielding removed to expose the damping resistor.  Damping resistor was removed and all shielding was replaced and coil shell refitted.

                            RX ( pin 1-2)                        TX ( pin 4-5 )
Inductance            511 uh                                Not Measurement
Resistance             6.9 Ohms                            Not Measurement
SRF                       272 kHz                              Not Measurement

Test 3: Coax coil was removed and short enamelled copper wires were soldered.  Shielding was refitted prior to testing.

                            RX ( pin 1-2)                        TX ( pin 4-5 )
Inductance            511 uh                                   280 uh
Resistance             6.6 Ohms                              0.47 Ohms
SRF                      331kHz                                  1040 kHz
 
Test 4: As per Test 3  without shielding.

                            RX ( pin 1-2)                        TX ( pin 4-5 )
Inductance            511 uh                                   280 uh
Resistance             6.6 Ohms                             0.47 Ohms
SRF                       333kHz                                  1060 kHz

Damping resistor 559 Ohms (soldered in parallel in the coil across the Rx wires)

Coax Cable 1525mm long
 
                            RX ( pin 1-2)                        TX ( pin 4-5 )
Capacitance           216 pF                                  316 pF
 
Feel free to post any additional measurements that may be of interest.
AuTitch


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Saturday March 10 2018 22:23:41 AEDT PM
Good job on the pics


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday March 10 2018 22:46:32 AEDT PM
Hi Autitch,

Great work, thanks for taking the time and for sharing,
Some interesting results you have there.
How do you find the coil itself  in use,  are you happy with it?
Coil lead capacitance is interesting

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday March 10 2018 23:48:01 AEDT PM
Hi Autitch,

In test 1 I noticed the TX resistance is 0.57 Ohms is that a typo?

Btw, it's good you have include your test circuit, also noticed your using the DE-5000.
There are a number of members here have them now so it's good for comparing notes.
I'll stick with using mine too instead of the Agilent just for clarity.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: autitch on Saturday March 10 2018 23:48:29 AEDT PM
I’ve put the numbers in a table with calculated capacitance from the SRF measurements.
There are some primary observations one can make from these measurements.
1. The coax parameters has a very large impact on the capacitance of the coil TX and a significant affect on the RX capacitance.
2. The RX interwinding capacitance is very large.
3. The shielding contribution to the capacitance of either the TX or RX is negligible.
4. The RX SRF is well below the 500 kHz figure that is consider optimum.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: autitch on Saturday March 10 2018 23:53:08 AEDT PM
  
Hi Autitch,

In test 1 I noticed the TX resistance is 0.57 Ohms is that a typo?

Btw, it's good you have include your test circuit, also noticed your using the DE-5000.
There is a number of members genre that have them now so it's good for comparing notes.
I'll stick with using mine too instead of the Agilent just for clarity.

Cheers

Muntari

I have checked my notes and the TX resistance was definitely 0.57 Ohms.

I have a second Coiltek DD 14" coil that may get sacrificed and that too measures 0.56 Ohms.

Autitch

Autitch
 


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday March 11 2018 00:06:23 AEDT AM
  
I’ve put the numbers in a table with calculated capacitance from the SRF measurements.
There are some primary observations one can make from these measurements.
1. The coax parameters has a very large impact on the capacitance of the coil TX and a significant affect on the RX capacitance.
2. The RX interwinding capacitance is very large.
3. The shielding contribution to the capacitance of either the TX or RX is negligible.
4. The RX SRF is well below the 500 kHz figure that is consider optimum.

AuTitch


Hi Autitch,

Indeed, that coil lead and the bundle wound coils are not helping Cp at all.
Are theses coils well used?

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: autitch on Sunday March 11 2018 00:14:49 AEDT AM
  
  
I’ve put the numbers in a table with calculated capacitance from the SRF measurements.
There are some primary observations one can make from these measurements.
1. The coax parameters has a very large impact on the capacitance of the coil TX and a significant affect on the RX capacitance.
2. The RX interwinding capacitance is very large.
3. The shielding contribution to the capacitance of either the TX or RX is negligible.
4. The RX SRF is well below the 500 kHz figure that is consider optimum.

AuTitch


Hi Autitch,

Indeed, that coil lead and the bundle wound coils are not helping Cp at all.
Are theses coils well used?

Cheers

Muntari



Muntari

I purchased the coils second  hand and I  have  never used them.  They are used  but in good  condition. 
AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday March 11 2018 00:20:54 AEDT AM
  
  
Hi Autitch,

In test 1 I noticed the TX resistance is 0.57 Ohms is that a typo?

Btw, it's good you have include your test circuit, also noticed your using the DE-5000.
There is a number of members here that have them now so it's good for comparing notes.
I'll stick with using mine too instead of the Agilent just for clarity.

Cheers

Muntari

I have checked my notes and the TX resistance was definitely 0.57 Ohms.

I have a second Coiltek DD 14" coil that may get sacrificed and that too measures 0.56 Ohms.

Autitch

Autitch
 

Hi Autitch,

I was thinking its a little weird with that TX resistance in test 1 unless I'm missing something,
Umm yes I missed the obvious, lead resistance, just re read your post and noticed the short enamelled wires were used in some tests...must be my bed time

Thanks for posting the table format, great job  ::62::

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Sunday March 11 2018 00:25:51 AEDT AM


Thanks Autitch, was just wondering, anyways hope you find some gold with them


Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Eski on Monday March 12 2018 18:37:18 AEDT PM
Hi guys , not sure if it helps :

there is a foam product that has low pressure expansion, we use it around window frames in home building...

it works like an adhesive  but will not warp things.

touch'n'seal no-warp foam window and door insulating sealant.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday March 12 2018 20:36:04 AEDT PM
  
Hi guys , not sure if it helps :

there is a foam product that has low pressure expansion, we use it around window frames in home building...

it works like an adhesive  but will not warp things.

touch'n'seal no-warp foam window and door insulating sealant.

Hi Eski,

Thanks for the info, will check it out

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Monday March 12 2018 21:29:52 AEDT PM
I need to replace some putty around a window is it any good for that ?, I can only find touch'n'seal  on ebay @ $38 a tube


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday March 12 2018 21:50:57 AEDT PM
  
I’ve put the numbers in a table with calculated capacitance from the SRF measurements.
There are some primary observations one can make from these measurements.
1. The coax parameters has a very large impact on the capacitance of the coil TX and a significant affect on the RX capacitance.
2. The RX interwinding capacitance is very large.
3. The shielding contribution to the capacitance of either the TX or RX is negligible.
4. The RX SRF is well below the 500 kHz figure that is consider optimum.

AuTitch


Hi AuTitch,

thanks for your time and effort doing this measurement.
It is quite interesting.

Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday March 13 2018 00:04:31 AEDT AM
Hi All,

Didn't have much time to do any work on the 18 inch coil this weekend but just enough time to revisit the spiral wound former using XPS.

Last time I tried with a 1mm bit it ripped the material and no matter what I tried, it just wouldn't work for me.

Now when I used the hot wire cutter to trim down the 30mm sheets of XPS i noticed different thickness of "skin" forming after  melting depending on the speed of the material passing through the hot wire. Eg..the slower it was fed the thicker the skin.
So it had me thinking...I grabbed a bit of scrap XPS and fed it through the hot wire cutter slowly then put the CNC to work to machine the same spiral pattern as per my original 200mm test coils and this time it machined Ok. I then passed the hot wire cutter over it once more just skimming the surface and it strengthened the XPS.
Just what I was looking for. I didn't bother cleaning it up much so looks rough but it works

I wound some 0.38mm enameled copper wire onto it, Inductance was same as original (99 uH)  SRF = 4.26MHz (originals were around 4.1 to 4.4).
So I might play with it a bit more when I get time, its worth it due to the weight saving.

I'm still trying to source some Sikabond foam fix from Bunnings they were out of stock at my local so its holding up the final assembly of the 18 inch coil

More later

Cheers

Muntari




Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday March 13 2018 19:11:00 AEDT PM
Hi all,

I have ordered the digital LCR/ESR meter PeakTech 2170 and it should arrive soon.
It is high time to own one.
 ::10 ::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday March 13 2018 21:47:42 AEDT PM
Muntari,  Bunnings Mile End Has it was there today just got home did you get my PM.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday March 13 2018 23:55:35 AEDT PM
  
Muntari,  Bunnings Mile End Has it was there today just got home did you get my PM.

Regards, Ian. ::62::

Hi Ian,

Thanks for that , yeah I noticed Munno Para have it too now.
Yep, just read you PM and responded, sorry missed it earlier
I've been busy rebuilding a larger vacuum former

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday March 13 2018 23:57:47 AEDT PM
  
Hi all,

I have ordered the digital LCR/ESR meter PeakTech 2170 and it should arrive soon.
It is high time to own one.
 ::10 ::
Aziz

Good stuff Aziz, yes it is  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday March 14 2018 14:40:17 AEDT PM
Hi Doug,

I have been thinking, perhaps we could have another thread for tools or methods related to coil building rather than me clutter up this thread, not sure?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday March 15 2018 23:09:06 AEDT PM
Hi all,

I will get my new LCR meter very likely tomorrow. It is on the way. I hope to speed up the development a bit then.
But I will work on a new PI design, which will exploit the new possibilities of the new coil design.
Main goal will be to reduce the ground noise effects and hence to minimize the detection hole and to increase the target response.
By sensing the coil coupling coefficient factor change (TX -> RX) a lot of ground noise effects in the off-time sampling time can be removed without decreasing the target response.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday March 15 2018 23:38:16 AEDT PM
Hi Aziz,
That's great news, they are certainly handy to have around.
It will be interesting to see what new PI design ideas you come up with too, that would fully exploit the coil benefits as you see them.

Cheers

Muntari




Title: Re: The need for big deep gold detectors.
Post by: Eski on Friday March 16 2018 18:27:23 AEDT PM
  
I need to replace some putty around a window is it any good for that ?, I can only find touch'n'seal  on ebay @ $38 a tube

na... no good for that!


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday March 16 2018 23:26:07 AEDT PM
Hi all,

my digital LCR/ESR meter PeakTech 2170 came today. I'm really happy with it.  ::10 ::
A lot of interesting measurements will be made in the coming days/weeks.

My coil software must be adapted & arranged to calculate more accurate. The spiral/spider coil arrangement is causing non neglectable error in inductance/induction calculation as there are to many wires in the calculation region (thin/thick wire model, magnetic field inside the wire, induction inside the wire, etc., a typical boundary case problem). I have to redesign some of the core implementations. Unfortunately, this is not so trivial.

But my sound card LCR meter is pretty darn accurate when calibrated properly. Didn't know it until I compared my measurements with the 2170 LCR meter. The inductance calculation was inaccurate due to the described facts above.


Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Saturday March 17 2018 00:40:12 AEDT AM
Hi Aziz,

Great stuff, glad you have it and you are happy with it.
Will you be prototyping some more coils?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday March 17 2018 01:00:25 AEDT AM
  
Hi Aziz,

Great stuff, glad you have it and you are happy with it.
Will you be prototyping some more coils?

Cheers
Muntari

Yes, but when I have solved the issues and upgraded my coil software. It's a time consuming stuff and I have to read the electromagnetics stuff once again.

But interesting finding regards to litz/magnet wire, which confused me during last weeks/month of making measurements:
The proximity effect isn't neglectable in bundle coils. The proximity effect is domination over skin effect even on litz wire and isn't neclegtable. Using litz wire in bundle coils is a waste of money. Hahaha  ::620::

But the proximity effect decreases on spiral/spider coils greatly and you can even use simple magnet wire. Haha, that's a great news. The skin effect is neglectable in this case.
 ::419::

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday March 17 2018 06:06:03 AEDT AM
Hi all,

my bull-sh1t-meter worked obviously totally wrong. No!, it worked perfectly.  ::43::
It has nothing to do with the proximity effect. Wrong assumption.
My bad. Sorry for this.

But the parasitic capacitive effects dominate on high test frequencies. The interwire capacitance can cause huge measurement errors when measuring at high test frequencies (for instance at 100 kHz).

Skin effect measurements are difficult, when there is some inter-wire capacitance. I have a litz wire bundle coil, which really has huge interwire coil capacitance. And a magnet wire spider web coil, which has low interwire capacitance.

Let's exploit this fact to get the SRF and Cp (parallel interwire coil capacitance) by measuring the coil at low and high frequency.
I wonder, whether it is possible. I will play with some measurements and spice simulations and check it out.
 ::10 ::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: autitch on Saturday March 17 2018 16:45:33 AEDT PM
Thats interesting  Aziz.  I noticed that at times the 100kHz inductance  measured quite a bit from the 1 &10 kHz measurements too. I don't  have my notes  with me but i do recall  this observation i just didn't  know  the  reason.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday March 19 2018 22:29:34 AEDT PM
Hi All,

Just a quick update on the 18 inch test coils.
I now have all the materials and glue to complete them and hope to get back onto it in the next week or so and will have something more to show then.
I'm currently finishing of the larger vacuum former which will be required for the coils both for shells and as a large vacuum clamp to hold all the wafers together.
So a bit of a long way round but it will make experimenting a lot easier down the track.
There's also been a lot of paying work come in for the CNC machines so of course that comes first.

I have quite a few new ideas I want to try out and share so some interesting times ahead.

More later

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday March 20 2018 16:43:11 AEDT PM
My Litz arrived today so I am about two thirds the way through winding the 400 uh approx RX spider coil slow process to get the wires into the slots cut in the XPS former I ended up using Muntari's method of using the backside of an old kitchen knife I tried various methods but that seems the best so far.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday March 20 2018 16:51:41 AEDT PM
Hi Ian,

That's good news on the Litz, hope it works out the way you planned, ah, the old kitchen knife, very handy tool ::62::
Do you find the XPS brittle or flaky or is it working Ok for you.

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday March 20 2018 17:20:25 AEDT PM
Hi Muntari not brittle but can get a bit flaky I wish I could have routed 1 mm slots rather than the blade cuts but we do what we can do.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday March 20 2018 22:11:47 AEDT PM
Hi Ian,

I am going to circle back on WM6's idea of using a hot soldering iron tip, only instead of the soldering iron tip, try using a needle point which is heated by a ceramic 3D printer extruder element., you can get then for $3-$5 of auction sites in both 12 and 24 V dc versions
I will do a quick draft and post under the tools and methods section.

The trick is to move the tip at such rate as to avoid over heating the XPS.
It works fine with some testing I did a few weeks ago.
It will be best to control the heat with a PWM to find the sweet spot.

Just gives us more options, so thanks WM6  is is a good idea, albeit slightly modified ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday March 21 2018 06:43:40 AEDT AM
Hi Muntari

Using hot soldering tip along with XPS on coil design regularly.
Of course in manual way only, and not in CNC hi-tech way like you.

Probably it could be better (for latter winding fix and to retain tight hot
grinding borders) if you use hot soldering tip shape for hot XPS grinding like this:

(https://i62.servimg.com/u/f62/19/61/60/05/xps_ho10.jpg)


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday March 21 2018 10:07:00 AEDT AM
Hi WM6,

That's an interesting way of doing it, is this what you are using?

If so, what is the approx dimensions of tip and what is the smallest inter-wire gap you have managed to achieve?

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday March 21 2018 11:17:42 AEDT AM
Hi Muntari

What I am mostly using are hot soldering "knife" tips (photo).

But, as I say, my way is limited to handwork, not CNC art, and I need it for
trenching gutters in XPS sheets (mostly on rand as on photo testing example).

This way I do not need nail headed hot tip, but for your CNC artwork,
 I presume, that nail-like headed hot tip could bring you better results.

(https://i62.servimg.com/u/f62/19/61/60/05/hot_so10.jpg)


Depend on solder type used (tip bore) some modified copper nails can be used too:

(https://i62.servimg.com/u/f62/19/61/60/05/hot_so11.jpg)



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday March 21 2018 11:49:17 AEDT AM
Hi WM6,

Ok, now I see what you are doing, great idea.

Thanks for sharing, yes I think a finer tip will be the go for cnc

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday March 21 2018 15:58:03 AEDT PM
Hi All,

The Litz spider RX coil is wound the specifications are 429 uh resistance 4.4 ohms and S.R.F coil on former 620 KHz.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday March 21 2018 19:38:49 AEDT PM
  
Hi All,

The Litz spider RX coil is wound the specifications are 429 uh resistance 4.4 ohms and S.R.F coil on former 620 KHz.

Regards, Ian. ::62::

Hi Ian,

this is really very nice. (So we have some more margin up to 500 µH inductance next time.)

I have been testing my digital LCR meter in the mean time. Measurement comparisons have shown, that my sound card LCR meter is almost as good and accurate as the 220 EUR bucks device.  ::620::
Both the digital LCR meter and sound card LCR meter behaves the same at high frequency measurement (100 kHz/45 kHz) on my heavy capacitance Litz bundle coil (a former VLF coil).

I have circuit simulated some (Jfet-)LC oscillators and simple RC-oscillator to have a simple tool for determining the SRF of the coil. I don't have a high frequency function generator and I have to build the tools yet.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday March 21 2018 23:41:12 AEDT PM
  
Hi All,

The Litz spider RX coil is wound the specifications are 429 uh resistance 4.4 ohms and S.R.F coil on former 620 KHz.

Regards, Ian. ::62::

Hi Ian,

That's great news, much better, well done.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday March 21 2018 23:49:07 AEDT PM
Hi Aziz,

That's good news will be good to get some testing on coils soon.
Won't be long now I think. ::402::
I tested the platen on vacuum former tonight and it's working very well, so I can get back on to test coils again in a day or so.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Friday March 23 2018 13:04:51 AEDT PM
Query regarding inductance ...
After coil is wound and inductance is example 500uH ..
will the inductance increase with sheilding and cable or decrease ..
I read somewhere that it will decrease by about 20 or 40 percent ..
yet seeing elsewhere that it will increase from the original wind of coil ..
thoughts .
I have a current coil (plain - without shield or cable etc ) at 1000uH using Litz on
HDP spider flat wound.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday March 23 2018 13:47:13 AEDT PM
Hi gef2,

The coil Q and inductance will  decrease depending on conductivity of shield, aluminum, copper, zinc, steel etc.
But adding extra cable length can increase inductance, it would have to be a fair bit of cable to get that 20-40% increase though.

I have found that the decrease in Q of the inductor will be affected with some materials worse than others, still the same net effect though.

I use Nickel shielding mostly and always with a gap in the shield (no shorted turn) but I don't see a drastic reduction in Q or inductance, certainly not 20-40% the distance between shield and spacer will of course play a part.




Cheers

Muntari




Title: Re: The need for big deep gold detectors.
Post by: gef12 on Friday March 23 2018 15:49:04 AEDT PM
  
Hi gef2,

The coil Q and inductance will  decrease depending on conductivity of shield, aluminum, copper, zinc, steel etc.
But adding extra cable length can increase inductance, it would have to be a fair bit of cable to get that 20-40% increase though.

I have found that the decrease in Q of the inductor will be affected with some materials worse than others, still the same net effect though.

I use Nickel shielding mostly and always with a gap in the shield (no shorted turn) but I don't see a drastic reduction in Q or inductance, certainly not 20-40% the distance between shield and spacer will of course play a part.

Tks Muntari ...

not percent but maybe uH .. 
Interesting read   http://www.geotech1.com/pages/metdet/projects/fastcoils/FastCoil.pdf
Will get back into it in week or so as still doing cyclone clean up after Markus ....
cheers for now





Cheers

Muntari





Title: Re: The need for big deep gold detectors.
Post by: gef12 on Friday March 23 2018 18:20:34 AEDT PM
  
Hi All,

The Litz spider RX coil is wound the specifications are 429 uh resistance 4.4 ohms and S.R.F coil on former 620 KHz.

Regards, Ian. ::62::

Hi Ian .. did you try your previous coil proto types .. ..
curious how u went or u waiting to get a bunch of differing values ...
My aim is to have a one go .. and to see an Ideal inductance


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Saturday March 24 2018 16:59:33 AEDT PM
Hi gef2,

I have now 3 different value RX coils just have to finish the last one then will try to do some testing before I have a full shoulder repair on the 12th of next month I will then be out of action according to the surgeon for 2 to 3 months we will see about that.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Sunday March 25 2018 15:10:46 AEDT PM
No probs Ian .. take it easy mate .. my brother had both done .. just do ur re=hab ...
cheers


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Monday March 26 2018 16:25:58 AEDT PM
Hi all,

Jeff fine I had the Right one done 13 years ago now for the left one only this one is a bit more problematical but once done should be fine and I know all about the rehab.
 
Attached find a picture of my latest Mono spider coil I am hoping to get it finished before my opp.

Regards, Ian. ::62::



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday March 26 2018 16:40:22 AEDT PM
Hi Ian,

Great work, is that masking tape you are using to hold windings?

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Monday March 26 2018 16:53:22 AEDT PM
Hi Muntari,

The blue masking tape is a marker so when I routed the wire slots with the 1.6 mm end mill I knew where the start and finish was because the slot is being cut on the underside the litz is just pushed into the slot interference fit no need for adhesive the wires are held in place when the shield spacer is bonded on I cannot go any further until I get the foam cutter going so I can trim the shield spacers to the correct thickness.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday March 27 2018 09:33:33 AEDT AM
Hi Ian,

Oh, Ok, I was looking at the photo thinking it was all covered in light blue masking tape, then realized, its the color of the XPS you are using,  ::62::

Great job anyway, look forward to seeing how it all turns out.

I've been busy with the vacuum former and will be away with work again so might be a week or so until I can get back into it.

Hope your Op goes well too Ian, good luck with it.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday March 27 2018 15:54:03 AEDT PM
Hi Muntari,

Yes the light blue is the IKEA XPS the green bands are the 2.5 mm XPS spacers where the wires go to the other side of the form so 10 winding's each side.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday March 29 2018 20:08:42 AEDT PM
Hi all,

I've been busy with my sound card LCR meter. I have improved it further using a three stage complex calibration (sound card, open and close calibration using complex math). It's base accuracy is now 0.1 % (my digital LCR meter has 0.3% base accuracy). I can improve it further by measuring my reference resistors down to 0.1%/sqrt(10) = 0.032% accuracy.

Unfortunately, this is required to measure the parasitic coil capacitance. The coil capacitance caused impedance effect is low but should be measurable. I hope to be able to do it.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday March 31 2018 01:16:43 AEDT AM
Hi all,

I've been quite tortured by the complex equations to calculate the parasitic capacitance Cp of the coil by simply making a low and high frequency impedance measurements.
 ::406::
It isn't that trivial. But I will make it quite trivial by Monte Carlo calculation algorithm.

I will be able to measure the Cp of the coil soon. By simply using my sound card LCR meter.
 ::10 ::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Saturday March 31 2018 08:44:50 AEDT AM
Keep at it Aziz, on my list of things to do, is make a simple RF oscillator, and if it works it will oscillate with just the coils inductance and capacitance, plus feed line, it will only give comparative results  between coils, but should be interesting experiment.


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Saturday March 31 2018 14:51:54 AEDT PM
  
Keep at it Aziz, on my list of things to do, is make a simple RF oscillator, and if it works it will oscillate with just the coils inductance and capacitance, plus feed line, it will only give comparative results  between coils, but should be interesting experiment.

Just for fun I made a VERY simple oscillator with a 40106 and the damn thing worked, I will make a better LC oscillator later, but this is what I got.
Home made bunch wind mono twisted pair feed line 1M long 243 uH 1.1564 MHZ
8" ML super gold search 296 uH  496.18 KHZ
8x6 Sadie 290 uH     501.18 KHZ


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Saturday March 31 2018 18:44:08 AEDT PM
Hi 6666,

the following Jfet LC oscillator works fine.
 ::419::
Aziz


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Saturday March 31 2018 22:01:21 AEDT PM
Thanks Aziz, I will see what bits I have in the junk box.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Tuesday April 3 2018 17:29:42 AEST PM
Hi all,

it seems, that the direct parasitic capacitance Cp measurement using an impedance meter isn't easy and requires a very very accurate measurement. The bandwidth of my impedance meter (sound card LCR meter) is limitted up to the nyquist frequency of 48 kHz (96 kHz sampling rate) and make measurements difficult. And the impedance change at high frequency (up to 48 kHz) is quite low to get accurate Cp readings.

The Monte Carlo algorithm worked very nice. But the real measurements screwed the accuracy. Overall it was a nice practice to calculate with complex numbers. I will try it again, when I have increased the accuracy of my sound card LCR meter further.

Be aware of when measuring a coil at high test frequency will give you wrong readings (higher inductance L and high coil series resistance Rs), when the coil Cp is high. But there is no problem at low test frequencies up to 1 kHz however.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday April 5 2018 20:18:31 AEST PM
Hi all,

here is a big surprise!  ::620::

My 5 bucks sound card LCR meter is by far more accurate than the 220 bucks digital LCR meter.
What a waste of money!  ::620::

I'll upgrade my sound card LCR meter circuit to be able to calibrate into 0.03 % accuracy.

Unfortunately the measurement accuracy is required to check some coil shielding capacitance calculations and the coil software.
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Doug on Thursday April 5 2018 20:36:27 AEST PM
  
Hi all,

here is a big surprise!  ::620::

My 5 bucks sound card LCR meter is by far more accurate than the 220 bucks digital LCR meter.
What a waste of money!  ::620::

I'll upgrade my sound card LCR meter circuit to be able to calibrate into 0.03 % accuracy.

Unfortunately the measurement accuracy is required to check some coil shielding capacitance calculations and the coil software.
Cheers,
Aziz

Why is the sound card LCR meter is by far more accurate than the 220 bucks digital LCR meter?  ::16 ::
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Thursday April 5 2018 21:06:13 AEST PM
  
Why is the sound card LCR meter is by far more accurate than the 220 bucks digital LCR meter?  ::16 ::
doug ::419::

Hi Doug,

it is quite simple:
1. Better calibration & measurement software
2. Higher measurement resolution (24 Bit ADC)
3. Higher noise immunity (more averaging between measurements)
4. More precision reference resistors used
5. Optimal measurement range selection

I don't even need Kelvin clips & circuit to outperform an expensive digital LCR meter.

My actual accuracy is 0.1%. My next goal is to achive 0.032% accuracy.
 ::419::
Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Friday April 6 2018 13:19:26 AEST PM
Hi Aziz .. must be using something as a reference for your accuracy ...  Local measurements Lab ?


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Friday April 6 2018 19:51:03 AEST PM
  
Hi Aziz .. must be using something as a reference for your accuracy ...  Local measurements Lab ?

Hi gef12,

I use high accuracy reference metal film resistors. I only have to know their exact resistor values.
I have bought a bunch of different 0.1% metal film resistors last month.
With the initial 0.1% reference resistors, I can measure lets say ten 1% resistors. When I connect the then resistors parallel, I can calculate their parallel resistor. So the value of the 0.1% resistor can be determined easily back and I can increase it's tolerance from 0.1% into 0.1%/sqrt(10) = 0.032%. Trivial task.
I have 5 reference resistor to be calibrated. Each measurement range has it's own reference resistor. Going from 10 Ohm, 100 Ohm, 1 kOhm, 10 kOhm to 100 kOhm.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Saturday April 7 2018 13:08:40 AEST PM
yep no probs Aziz .. sounds feasable .. I did a course " Meausurements Uncertanity" with NMI Aust years ago for our work and there was a lot of math involved.. as we calibrated "Instruments" and was required at the time .. now we out source thank god ... so dont have to go to court if there are issues now....


Title: Re: The need for big deep gold detectors.
Post by: Alex on Tuesday April 24 2018 08:53:35 AEST AM
Hi all .I hope this is the right place to post this question.On this subject on post 431 Ian listered specs on coils.What has me confused ,is we strive for the highest resonate frequency but the 12 inch evo coil has a resonate frequency of 510khz which I thought was low  and yet has very good reviews.I hope someone in the know could explain this . Thanks again.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday April 24 2018 12:11:34 AEST PM
Hi Alex,

This coil at 510 kHz SRF would still have relatively low capacitance though, so it should perform well.

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: autitch on Tuesday April 24 2018 21:48:05 AEST PM
Hi Alex,

I've measure a bunch of coils that I have and here are the results.  You will notice that my measured results vary from what was previously posted by IBGold however one can get a sense of the order of the SRF between coils. 

NF EVO 12" - SRF 622 kHz, 309 uH, 212 pF calculated
NF EVO 14"x9" - SRF 653 kHz, 298 uH, 198 pF calculated
NF EVO 17"x13" - SRF 613 kHz, 309 uH, 218 pF calculated
NF ADVANTAGE - SRF 633 kHz, 291 uH, 217 pF calculated
COILTEK 16" GOLDSTALKER - SRF569 kHz, 310 uH, 252 pF calculated
COILTEK 14" DD - TX SRF 464 kHz RX SRF 272 kHz without damping resistor ( damping resistor 559 Omhs in parallel)
ML COMMANDER 11" - SRF 634 kHz, 290 uH, 217 pF calculated

In my opinion the increased sensitivity of the flat wound coils compared to the bundle wound coils is due to the winding creating a better / more efficient antenna when the mono coil  receives a signal from a target. 

Except for the Goldstalker all the other monos all have a very comparable SRF.  Inductance is about 6% higher for the NF EVO 12 compared to the ML COMMANDER 11 and the ML has slightly higher SRF however the EVO is a more sensitive coil.  I suspect that what is holding back all commercial coils including the NF EVO flat wound coils is the relatively high capacitance of the coil.  On assessment, different winding techniques haven't improved the SRF unless the coils have been tuned to maintain similar SRF between flat wound and bundle wound coils by playing with the capacitance of the coils. 

Has anyone cut a foot from the coax cable on a flat wound coil to see the infield results?

AuTitch




Title: Re: The need for big deep gold detectors.
Post by: Alex on Wednesday April 25 2018 15:52:39 AEST PM
Thanks autitch great info.


Title: Re: The need for big deep gold detectors.
Post by: GARY on Wednesday April 25 2018 19:42:52 AEST PM
  

NF ADVANTAGE - SRF 633 kHz, 291 uH, 217 pF calculated

In my opinion the increased sensitivity of the flat wound coils compared to the bundle wound coils is due to the winding creating a better / more efficient antenna when the mono coil  receives a signal from a target. 



I would agree with you in regards to the increased sensitivity of the Flat wound mono over the Bundle wound mono.

BTW what size coil was the NF ADVANTAGE ?

Gary.


Title: Re: The need for big deep gold detectors.
Post by: autitch on Wednesday April 25 2018 21:00:35 AEST PM
The NF Advantage is 16" round.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday April 25 2018 21:24:54 AEST PM
  
  

NF ADVANTAGE - SRF 633 kHz, 291 uH, 217 pF calculated

In my opinion the increased sensitivity of the flat wound coils compared to the bundle wound coils is due to the winding creating a better / more efficient antenna when the mono coil  receives a signal from a target. 



I would agree with you in regards to the increased sensitivity of the Flat wound mono over the Bundle wound mono.

BTW what size coil was the NF ADVANTAGE ?

Gary.

Thanks for posting your findings Autitch

Ditto, I agree, more wire turns exposed to target but also less capacitance.
Using different coil lead length and/or different types of coax material will in my opinion, have much more effect on Cp than most well constructed coil windings and then you have connectors, solder joints, shielding, critical damping, mosfet Coss etc. It truly is a trade off on the system as a whole.
Coils have come a long way in recent years, hats off to the coil manufacturers but I think they can still be improved and the coil leads should definitely be put front and centre of any new design..my 2 cents worth anyway

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday April 26 2018 14:43:39 AEST PM
  
  
  

NF ADVANTAGE - SRF 633 kHz, 291 uH, 217 pF calculated

In my opinion the increased sensitivity of the flat wound coils compared to the bundle wound coils is due to the winding creating a better / more efficient antenna when the mono coil  receives a signal from a target. 



I would agree with you in regards to the increased sensitivity of the Flat wound mono over the Bundle wound mono.

BTW what size coil was the NF ADVANTAGE ?

Gary.

Thanks for posting your findings Autitch

Ditto, I agree, more wire turns exposed to target but also less capacitance.
Using different coil lead length and/or different types of coax material will in my opinion, have much more effect on Cp than most well constructed coil windings and then you have connectors, solder joints, shielding, critical damping, mosfet Coss etc. It truly is a trade off on the system as a whole.
Coils have come a long way in recent years, hats off to the coil manufacturers but I think they can still be improved and the coil leads should definitely be put front and centre of any new design..my 2 cents worth anyway

Cheers

Muntari

I agree in my view higher performance coils can be made as we are not bound by the constraints of  the commercial builders we can take the time to optimize the winding,the former materials and thicknesses, shield types and coax types and lengths personally I run shorter coax lengths than most, coil to detector + 100 mm with coax securely fixed to shaft with just enough excess to re terminate the plug if and when required I could go on about Coax design requirements but commercially it goes on deaf ears so I have given up. 

Regards, Ian.  ::62:: 


Title: Re: The need for big deep gold detectors.
Post by: Alex on Friday April 27 2018 17:13:47 AEST PM
Hi Ian ,yes coax.I find not only the capacidence to take into account but the coax I been using raises the uh about 25 uh for 1.2 mt length.I was thinking about trying a twisted pair.


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Saturday April 28 2018 16:00:49 AEST PM
Hi Alex,

Yes I have tried most coax's available in Australia and homemade coax as well as twisted pair's shielded and unshielded there are pro's and con's for all but I have yet to find anything I am really happy with but while I am out of action for the next six weeks or more I have plenty of time to think about it.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: gef12 on Sunday April 29 2018 10:11:37 AEST AM
Have found in my collection of coax " Prolink interconnect s-vhs cable"  about 20pf / ft .... but inner core is rather thin ..
might be good if just using the Rx coil.
Have DD coax (from the tx side) measuring 45pf  .. lost the rx side somehow.... may have used on another project.


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Monday April 30 2018 16:31:50 AEST PM
Hi Geff,

The best coax I have found is a Soundlink one From Wess Electronics or https://www.wagneronline.com.au/soundlink-shielded-audio-cable-7mm/cable/cables-connectors/aic227-10192/5995/pd/ . AIC227 It is low capacitance 7 mm OD but stranded OFC copper and the center conductor could be bigger but if firmly mounted to shaft so it cannot move works OK I have not tried their AIC228 though but that could also be OK and it has a heaver center conductor but is 8 mm OD it is a pity they do not do them with either tinned or enameled strands.

Regards, Ian.


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Monday April 30 2018 17:16:06 AEST PM
Hi Ian

What mean declared "super low capacitance"? How much per meter of length?

"Heavy duty PVC Jacket" is nice read too.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday April 30 2018 22:45:15 AEST PM
  
Hi Ian ,yes coax.I find not only the capacidence to take into account but the coax I been using raises the uh about 25 uh for 1.2 mt length.I was thinking about trying a twisted pair.

Hi Alex,

the rise of 25 uH of the coil inductance is oved to the measurement error in conjunction with higher coax capacitance and high test frequency.
1.2 m coax cable won't add such a huge inductance.
Try to measure the inductance at low frequencies (100 Hz, 120 Hz or max. 1 kHz). The higher the test frequency, the higher the wrong inductance reading will be due to higher capacitance effects.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Monday April 30 2018 22:52:12 AEST PM
Hi all,

pity, I don't have much time to show you my self-made RX coax cable.
It is really easy to build and cheap too.

Measured capacitance:
31.68 pF/144 cm (6.7 pF/ft, 22.0 pF/m, @10 kHz measurement frequency)
31.46 pF/144 cm (6.6 pF/ft, 21.8 pF/m, @100 kHz measurement frequency)

The assembly principle can be applied to a true litz wire based TX coax cable too (both core and shielding as litz wire solution). But I haven't built the TX coax cable yet.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday May 1 2018 11:04:58 AEST AM
Hi Ian,

I have sent an email to WES regarding the AIC228 cable capacitance as it does not state it on the listing.
Might get some if it looks ok.

Had my eye on some other shielded microphone cable @ 22pF per metre but then fell off my chair when I looked at the price $1850 for 300 meters and they only sell in 300m quantities...German made stuff... it can wait I think  ::62::

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday May 1 2018 11:38:51 AEST AM
Hi Ian and All,

Ok, WES says the Cp of AIC228 is 19.4pF per ft.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Tuesday May 1 2018 15:37:54 AEST PM
  

Ok, WES says the Cp of AIC228 is 19.4pF per ft.

Muntari


Thanks Muntari.
About 60pF per meter. Not really "super low" as stated, but acceptable.


Quote from: Muntari

... fell off my chair when I looked at the price $1850 for 300 meters....



Ha, ha, hope it is only a typo and in fact it is $300 for 1850 meters.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday May 1 2018 16:46:37 AEST PM
Hi WM6,

It's Belden Brilliance 2221 2 core + shield, stupid prices but good cable.

There are also a few guitar cables which are essentially coax that will do the job nicely with Cp ranging 38-55 per metre.

Also, as Gef12 has mentioned, some video cable is suitable. Look for studio and stage cables, there are plenty of flexible types with braided shield.

All in all, Ian's find, is not too bad for the price, readily available, just have to save some Cp from the coil construction.

I'm waiting on pricing for low Cp guitar cable atm and will post once I hear back from distributor.

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday May 1 2018 16:53:30 AEST PM
The AIC 227 is 17pf per foot from memory.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Alex on Tuesday May 1 2018 20:18:37 AEST PM
  
  
Hi Ian ,yes coax.I find not only the capacidence to take into account but the coax I been using raises the uh about 25 uh for 1.2 mt length.I was thinking about trying a twisted pair.

Hi Alex,

the rise of 25 uH of the coil inductance is oved to the measurement error in conjunction with higher coax capacitance and high test frequency.
1.2 m coax cable won't add such a huge inductance.
Try to measure the inductance at low frequencies (100 Hz, 120 Hz or max. 1 kHz). The higher the test frequency, the higher the wrong inductance reading will be due to higher capacitance effects.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Alex on Tuesday May 1 2018 20:32:33 AEST PM
Thankyou. Aziz.I appreciate your reply ,with what your dealing with at the moment.  I have been confused with that for a while ,it didn't make sense.  My inductance meter wont measure at that low frequency.so ill calculate coax and measure coil separately.


Title: Re: The need for big deep gold detectors.
Post by: Aziz on Wednesday May 2 2018 19:05:04 AEST PM
  
Thankyou. Aziz.I appreciate your reply ,with what your dealing with at the moment.  I have been confused with that for a while ,it didn't make sense.  My inductance meter wont measure at that low frequency.so ill calculate coax and measure coil separately.

Hi Alex,

you can do a simple measurement test. Connect a small capacitor (100 pF) parallel across the coil and measure its inductance.
The measured inductance will be higher without the parallel capacitor.
The coax cable does add a huge capacitance across the coil.

The inductance of the coax cable can be easily calculated.
see here https://www.allaboutcircuits.com/tools/coax-inductance-calculator/
The inductance of the coax cable should be around 1-2 µH or less.
But not as much as you thought.

Cheers,
Aziz


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday May 8 2018 10:54:58 AEST AM
Hi All,

I came across this interesting read on simplifying the choice of Litz wire construction.

[urlhttp://web.mit.edu/ryz/www/pdf/simplitz_apec2014.pdf][/url]

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Friday June 15 2018 16:14:48 AEST PM
  
Hi all,

Jeff fine I had the Right one done 13 years ago now for the left one only this one is a bit more problematical but once done should be fine and I know all about the rehab.
 
Attached find a picture of my latest Mono spider coil I am hoping to get it finished before my opp.

Regards, Ian. ::62::



Hi all I am back starting to be able to use the arm again and have now finished this coil final details are.
Mono spider coil.
20 turns of 150/38 litz wire.
Turns spacing 5 mm former 10 mm thick rebated 2 mm deep 1.6 mm wide to take the winding both sides.
Coil to shield capacitance.   = 106.2 pf.
SRF shield in place but not connected.   = 695 KHz.
Coax 1400 mm long.       = 100 pf.
Finished Inductance.   = 295 uh.
Finished resistance.    = 0.48 ohms.
Finished SRF.         = 552 KHz.

the Litz RX coil is ready for shielding will do that in the next few days. 

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Sunday June 17 2018 14:04:02 AEST PM
I am curious as to what will be the bench mark for seeing improvement over current coils ?


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Sunday June 17 2018 15:57:45 AEST PM
Testing against an 18' Elite flat wound Mono first up.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday June 18 2018 09:54:18 AEST AM
Hi Ian,

Good to hear you are up and about again.

I've been snowed under with work and been out in the paddocks while weather is good and not had much time for the coil project lately.
Everything is ready to assemble and test, just have to find time to do it now.

The coil comparison sounds like a plan.


cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Monday June 18 2018 16:43:34 AEST PM
Hi Muntari,

Check your email I emailed you last week.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Eski on Monday June 18 2018 17:05:34 AEST PM
HEy Ian, will you put some final pics of the coil before you test?
 reason i ask is i want to start winding some project coils inc something like this but need to get setup - it would be better if i had an idea what i would need and i think it would be helpful to see your finish coil.


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday June 19 2018 16:19:06 AEST PM
Hi Eski,

I will compile a series of shots that should give you some pointers tomorrow.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Eski on Tuesday June 19 2018 20:12:56 AEST PM
cheers Ian , that is awesome.!


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday June 20 2018 15:39:09 AEST PM
Hi Eski,

I did not take a full range of build pictures for this build but here are some all spider wind but some are RX coil and a couple are the latest TX coil but it does not matter the construction is the same.

Regards, Ian.


Title: Re: The need for big deep gold detectors.
Post by: autitch on Wednesday June 20 2018 16:15:19 AEST PM
Hi Ian,
It’s great to hear you are well on the road to getting over your operation and I guess you must be getting keen to head out for a swing.  I’ve been looking at your most recent photos with great interest as I’m working on 14” flat wound coil with homemade “mad” litz wire and coax.  I was wondering how you have shielded the windings.  I’ve been scratching around for a reliable shielding method and I can’t quite nail a reliable method.
AuTitch


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday June 20 2018 16:35:26 AEST PM
Hi Autich,

You are looking at it last picture Electro-Dag painted on heavy paper glued to former.

Regards, Ian.


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Wednesday June 20 2018 18:54:12 AEST PM
Great work Ian. Must say, again, from you.

Congratulations.


Title: Re: The need for big deep gold detectors.
Post by: autitch on Thursday June 21 2018 10:16:56 AEST AM
Thanks Ian,

I'm looking for a supplier AATM There are so many different products which confusing the issue.

Gust wondering would this stuff work

https://www.mgchemicals.com/downloads/tds/tds-838ar-a.pdf

it's available through Mektronics  Australia.

AuTitch


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday June 21 2018 15:55:55 AEST PM
Hi AuTich,

The product I am using is Ex one of the coil makers and now no longer available to me what you require is something with a resistance of around 60 to 100 ohms per inch if you find something let me know as I am looking for something as I have only enough left for one coil that stuff would be OK for painting on the inside of the coil housing if the resistance is OK and it is a simple way of shielding anything with solvents is a problem on Styrofoam and XPS former's.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: autitch on Thursday June 21 2018 16:04:36 AEST PM
Hi Ian,

I’m assuming that the ohms measurement is performed with the probes one inch apart or do you use the four probe sensing method.

 AuTich,


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday June 21 2018 16:25:32 AEST PM
You are correct 1" apart.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: autitch on Thursday June 21 2018 16:26:45 AEST PM
Thank Ian


Title: Re: The need for big deep gold detectors.
Post by: Eski on Monday June 25 2018 17:46:57 AEST PM
thanks for that Ian ,
I think the later tx coil is the one with the "round" Windings ?


Title: Re: The need for big deep gold detectors.
Post by: Eski on Monday June 25 2018 17:50:34 AEST PM
ALso Ian , in that last coil the tx and rx are all encased in the one casing? roughly what sort of separation is there between the 2 coils?

On a side note, i may have missed it , but what machine are you running this on?

Looks good , reckon you'll be testing in no time!

sorry for the twenty questions....


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Tuesday June 26 2018 17:11:23 AEST PM
Hi Eski the last 3 pictures are the TX mono coil only not to be used in conjunction with the RX coils the others are RX to go with existing TX Mono's as Aziz's ideas.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday November 5 2018 12:37:29 AEDT PM
Hi All,

Following on from where I left off, many moons ago....
I have managed to get back onto building up my suite of coil platforms that can be taken into the field for real world testing.
Not being 100% convinced with flat wound coils, I back-tracked a bit to look at the bundled versus flat /spiral  arguments and how I could go about getting the best out of both in a large and medium format coil, so from say 300 to 490 mm diameter loop.
The latest posts regarding ground loops and the Bismark coil have prompted me to start posting a little more.
Its also interesting to note my flat wound posted a while ago, resembles the Bismark, so it shows size and ratio thinking are very close and that Aziz was on the right path.
I am convinced from recent field tests that concentric / co-planar coils have their place in nugget hunting and that there is an optimal size and ratio of TX to RX that is required to achieve the best performance.
Concentric designs are not new, they have been around for many years but because of their weight to size ratio, have been relegated down the list on preferred coil types.
Despite this, they have a great SNR  which is very important when looking for deeper objects and hence,the position of the  RX coil, while not critical, is best centred on the TX coil.
In bench tests and field tests alike, I have found that moving the RX closer the TX results in same target depth in air but the SNR degrades.
Likewise the ratio of inductance between TX and RX, you can increase RX gain by adding extra turns but only up to a point for each given size of TX and that ratio is not linear.
Then you throw in the bundle versus flat arguments versus Litz wire and other wire types and the waters become quite muddy.
Everyone has their view on what is best for them, manufactures and serious users and experimenters alike (Ian) have spent many years looking for the holy grail of coils and come up with some outstanding results but like Aziz, I like to question the thinking as it motivates me to find better ways of doing things.
From that thinking I put the theory into practical experiments and get out an test for myself, even if its been done before...I want my data not someone else's, that might not even be available anyway.
So, in the spirit of keep Aziz's original post and theory alive, I will try and post progress over the next year or so on what I've been up to...
I'll post what I can as I get time.
A couple of photos attached on the latest test piece, 3D printed formers that snap together
Print time was 5 hours for the set with clips, TX 390 mm RX 280 mm hieght 10mm width 15 for RX 20 for TX
Total weight of pictured assembly, including wire, is 250grams
A foam spacer is added sprayed with shield material and its ready for field test.

Cheers

Muntari




Title: Re: The need for big deep gold detectors.
Post by: Huego on Monday November 5 2018 13:43:49 AEDT PM

Beautiful & tidy and light... great work!!
What detector will you use for testing your coils Muntari?
QED or ML?

regards, Huego


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Monday November 5 2018 14:13:21 AEDT PM
  

Beautiful & tidy and light... great work!!
What detector will you use for testing your coils Muntari?
QED or ML?

regards, Huego

Hi Huego,

Thanks,  yes , needs to be ultra light. detectors used are QED, ML and one other.

Here is shell for last posted,  weight is calculated to be 280 gm so all up will be slightly less than 600 gm...

The design allows for flat and bundle wound

cheers

Muntari




Title: Re: The need for big deep gold detectors.
Post by: GARY on Monday November 5 2018 17:12:34 AEDT PM
  
Hi All,

Following on from where I left off, many moons ago....
I have managed to get back onto building up my suite of coil platforms that can be taken into the field for real world testing.

I am convinced from recent field tests that concentric / co-planar coils have their place in nugget hunting and that there is an optimal size and ratio of TX to RX that is required to achieve the best performance.

So, in the spirit of keep Aziz's original post and theory alive, I will try and post progress over the next year or so on what I've been up to...I'll post what I can as I get time.


A few years back I was privileged to view some in-ground testing which to me displayed how well a CC coil could perform during some in-ground tests at a purpose built test site with the ground at the site being mineralised enough to produce problems using the Normal timing on the GPX. That particular CC round coil was 14" in diameter and appeared to be capable of handling the mineralised ground at the test site better than the larger round Mono coils, an 18" and 22", it was being compared too over the gold nuggets being used for the test results at various depths. Also the CC coil appeared to operate smoother than the Monos when the GPX was set in its Normal timing.

Gary.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday November 6 2018 00:07:30 AEDT AM
Hi Gary,

Yes, that does not surprise me at all. The CC coils do handle mineral soils well in my opinion. The Coiltek ellipitcal mono 600 x 300mm  I have is insanely noisy over mineralized ground compared to the the  CC coil type shown in my earlier posts now while that is to be expected given the mono's size,  the standard ML 280mm round DD is also noisy compared to this concentric which also has a receive coil at 280mm and that was interesting as the ML was my go to coil for tough soils.
The round CC design requires more overlap on the swing but I have an elliptical version in the works too, I just have't completed the cad design for it just yet.

In the workshop, the CC is fine with all the hash produced by my PC and the 3D printer and cnc running close by, in the field it is a stable coil design and I am glad I went on testing with it. Still want to try a few more things which are mainly to do with the weight reduction and ergonomics than anything else.

more later...

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Doug on Tuesday November 6 2018 10:48:03 AEDT AM
  
Hi Gary,

Yes, that does not surprise me at all. The CC coils do handle mineral soils well in my opinion. The Coiltek ellipitcal mono 600 x 300mm  I have is insanely noisy over mineralized ground compared to the the  CC coil type shown in my earlier posts now while that is to be expected given the mono's size,  the standard ML 280mm round DD is also noisy compared to this concentric which also has a receive coil at 280mm and that was interesting as the ML was my go to coil for tough soils.
The round CC design requires more overlap on the swing but I have an elliptical version in the works too, I just have't completed the cad design for it just yet.

In the workshop, the CC is fine with all the hash produced by my PC and the 3D printer and cnc running close by, in the field it is a stable coil design and I am glad I went on testing with it. Still want to try a few more things which are mainly to do with the weight reduction and ergonomics than anything else.

more later...

Cheers

Muntari

What is the optimal way to run these coils?
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday November 6 2018 12:03:00 AEDT PM


What is the optimal way to run these coils?
doug ::419::
[/quote]

Hi Doug,
With the ML GP3000, pretty much the same setup as DD but with more sweep overlap and don't use too much tracking.
The threshold is noticeably more stable in mineralised soils
What will be noticed is how quiet they run compared to a mono and DD of comparable size.
I have yet to fully optimise the CC coil for the QED so I cant really give an answer on optimal setting for it just yet,its a bit too early,however, it does work with it.

I will know in a few months the optimal settings for each detector once I have completed all my testing.

The biggest issues being faced is getting time and obtaining Litz wire and so I have been experimenting with other wire types, so things will change accordingly. ::419::
I have a number of projects on the go all in various stages but all interrelated.

cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Doug on Tuesday November 6 2018 12:33:16 AEDT PM
  


What is the optimal way to run these coils?
doug ::419::
[/quote]

Hi Doug,
With the ML GP3000, pretty much the same setup as DD but with more sweep overlap and don't use too much tracking.
The threshold is noticeably more stable in mineralised soils
What will be noticed is how quiet they run compared to a mono and DD of comparable size.
I have yet to fully optimise the CC coil for the QED so I cant really give an answer on optimal setting for it just yet,its a bit too early,however, it does work with it.
On the revamped MPI design, likewise, settings are not like a standard PI so it would not help to post findings on that...

I will know in a few months the optimal settings for each detector once I have completed all my testing.

The biggest issues being faced is getting time and obtaining Litz wire and so I have been experimenting with other wire types, so things will change accordingly. ::419::
I have a number of projects on the go all in various stages but all interrelated.

cheers

Muntari


[/quote]

thanks! ::62::
I guess the most sensitive coil would be bundle wound TX and flat wound RX?
Keep us informed  on the MPI project particularly for new member who might be unaware of what it is.
Here is the link to the MPI project
http://australianelectronicgoldprospectingforum.com/diy-detectors-read-all-about-the-aziz-mpi-and-moodztinkerer-pi-detector/blast-from-the-past-mpi/
link-http://australianelectronicgoldprospectingforum.com/diy-detectors-read-all-about-the-aziz-mpi-and-moodztinkerer-pi-detector/blast-from-the-past-mpi/
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday November 6 2018 12:53:35 AEDT PM
"I guess the most sensitive coil would be bundle wound TX and flat wound RX?"

It could very well be as there is not much difference on the bench and in most hot soils I have tested (between fully flat and bundle).
TX coil still needs to be fast but with good design and construction, bundle wound should suffice.
Getting the ratios correct is the balancing act needed.

The revamped MPI is just going to be my test bed, it will never be sold commercially, it's too complicated and costly to produce and I don't need the BS that comes with it  ::62::
In a nutshell, it is a hyped up DSP engine with data logging capabilities, invaluable for field research
Its just good to have a new perspective on my old designs...and I'm having too much fun with coils atm.

cheers

muntari


Title: Re: The need for big deep gold detectors.
Post by: Doug on Tuesday November 6 2018 14:29:05 AEDT PM
  
The revamped MPI is just going to be my test bed, it will never be sold commercially, it's too complicated and costly to produce and I don't need the BS that comes with it  ::62::
cheers
muntari

Costly detectors are no problem for some people who are happy to fork out $10K!
doug  ::419::


Title: Re: The need for big deep gold detectors.
Post by: Doug on Tuesday November 6 2018 14:35:52 AEDT PM
  
Getting the ratios correct is the balancing act needed.
cheers
muntari
What do you mean by this? The inductive ratios  between the TX/RX or simply the wire turns ratio? One idea you might think about is one that the late Jim Stewart was perusing with his CC coil and this was to be able to raise or lower the center coil.Jim never fully explained this idea so I am not sure what was behind it.
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday November 6 2018 14:54:03 AEDT PM
Hi Doug,

The inductive ratio / RX gain and SNR balancing act.
On the CC coil yes vertical adjustment, I did this with the MPI where each RX coil was raised or lowered in respect of it's position within the linear array.
Could be interesting to re-visit but it will essential only change the RX signal gain, in an array it was important, in a hand held it would allow optimum SNR but at a cost of depth.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Tuesday November 6 2018 16:31:59 AEDT PM
  
  
The revamped MPI is just going to be my test bed, it will never be sold commercially, it's too complicated and costly to produce and I don't need the BS that comes with it  ::62::
cheers
muntari

Costly detectors are no problem for some people who are happy to fork out $10K!
doug  ::419::

Sorry missed this post, yeah, I guess so but for me, I am happy to enjoy what I do without all the problems  ::62::


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Tuesday November 6 2018 22:55:34 AEDT PM
Quote
The revamped MPI is just going to be my test bed

Is that the one you chucked out all the pcb's ?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday November 7 2018 09:57:35 AEDT AM
Yeah, that's the one, chucked out everything to do with it, hardware, software, engineering notes, the whole lot.

That was along with another 25 years worth of projects and surplus electronics stuff that was just cluttering up my workshop.

The MPI circuits have been redesigned using latest technology, its half the size and uses off the shelf DSP modules and custom front end boards.
I just had to research new components, redesign boards and write a whole lot of new code, the method was still in my head so not so bad.

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Doug on Wednesday November 7 2018 13:08:15 AEDT PM
  
In a nutshell, it is a hyped up DSP engine with data logging capabilities, invaluable for field research

cheers
muntari

The data data logging capabilities  are in my opinion incredibly important both  for coil testing and data acquisition over various ground types.  The latter may lead to  better or individualized ground cancelling algorithms.
doug ::419::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday November 7 2018 14:09:49 AEDT PM
Yes, as a tool, data loggers are a must for field research and further to that, a tool with some DSP grunt is invaluable for filtering and segmenting data on the fly.
You can exclude, include, mix data depending on the experiment.

On CC coils, you mentioned Jim's idea of adjusting the RX vertically and I said I had done this with the MPI too.
Well, to add to this a little more, I have previously mentioned my use of gradiometer type coils which is akin to Aziz's 'top hat' in many ways.
Now this is where you can use the adjustment, the top RX coil is moving in relation to the co-planar RX /TX combination and the reason it is done, is to achieve better SNR without the loss of depth that would happen if you moved the co-planar RX up or down relative the TX.
If you move it up, you loose equivalent depth.
Thanks to Corbyn's and Colani's early work and MRI research, the light bulb turned on in my head a long time ago, not about the electronics, about the coils.

more later

Cheers

Muntari



Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday November 7 2018 20:04:36 AEDT PM
Here is a picture of the bundle versus flat spiral wound coils.

Same inductance on both units.
The depth and noise figures are about the same will post SRF when I get more time.
One interesting thing though is the weight, there is only about 100 grams difference... 590 bundle, 695 spiral



cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Thursday November 8 2018 00:35:13 AEDT AM
  
Here is a picture of the bundle versus flat spiral wound coils.



Hi Muntari

Wrong Photo?

I cannot see flat spiral wound coil on this photo.
Seems both coils are bundle wound.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday November 8 2018 09:30:16 AEDT AM
Hi WM6,

The bottom foam pieces hold the spiral coils, I will remove the foam tonight and post a photo.
I should have explained a bit more but was just trying to show size comparison.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Thursday November 8 2018 16:44:39 AEDT PM
Hi when we talk coil sizes can we use center-line measurements IE bundle center line and flat wind center-line rather than coil OD.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday November 8 2018 21:12:17 AEDT PM
  
Hi when we talk coil sizes can we use center-line measurements IE bundle center line and flat wind center-line rather than coil OD.

Regards, Ian. ::62::

Hi Ian,

Yes, sure, why not, save any confusion.. ::62::

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday November 8 2018 23:50:01 AEDT PM
Here is the stripped down spiral and bundle details as promised.
I will give more info once I have completed some more builds and settled on final form, then field tested again.




More later

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday November 9 2018 00:06:13 AEDT AM
Just a quick note on comparing concentric spiral versus bundle wound.
Enough separation is required between TX inner and RX outer
How much, depends on the size of the RX coil required.

To get the equivalent inductance on spirals requires more turns than a bundle wound
To get equivalent  depth requires a larger diameter receive coil.
To get a bigger receive coil, requires a larger TX coil...

Then you have to balance this with the increased capacitance

No free lunch

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: WM6 on Friday November 9 2018 01:22:55 AEDT AM
Great! Thank you Muntari.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday November 9 2018 09:49:46 AEDT AM
  
Great! Thank you Muntari.

No Worries WM6

Btw center line for spiral wound is

TX 407
RX 228

You will notice on the flat former, windings can start an finish further in or out, depending on requirements ...it is my re-usable test bed  for the bench, field test units get fully enclosed and the former is cut to finished size to eliminate as much weight as possible so finish part looks nothing like this.

Cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 9 2019 13:40:05 AEDT PM
Finally, got back to setting up more coils for field testing later in the season.

Below are some photos of the 400 mm round concentric with draft 3D printed housing.

Last photo is of some Toro sprinkler stands, which are made from ABS and 350 mm diameter ..look interesting for use as a DIY coil housing...part number is embossed on them but haven't yet tried to see if they can be purchased separately


Title: Re: The need for big deep gold detectors.
Post by: dasenator777 on Wednesday January 9 2019 14:32:23 AEDT PM
are you selling any of these coils buddy  ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 9 2019 14:42:53 AEDT PM
  
are you selling any of these coils buddy  ::62::

Might do once tested and verified  ... I have a few other things on my radar that may take more of my time, not sure yet, if trigger is not pulled on those, then I'll seriously think about it.
 
Noticed you are in the Gilbert Valley, not a long way from me  ::62::

cheers

Muntari




Title: Re: The need for big deep gold detectors.
Post by: Alex on Wednesday January 9 2019 14:56:19 AEDT PM
Great work Muntari. Thanks for sharing ,ill look forward for the test results.I am also impressed with the weight A flat spiral mono 15 inch I wound was 850gms


Title: Re: The need for big deep gold detectors.
Post by: dasenator777 on Wednesday January 9 2019 14:56:41 AEDT PM
yep im in the clare area mate , will look forward to the updates  ::402:: ::62::


Title: Re: The need for big deep gold detectors.
Post by: IBGold on Wednesday January 9 2019 15:42:38 AEDT PM
Hi Muntari, I am sure you have it covered but I do not see a gap in the shielding from the center to one edge of the housing so the shield does not act as a shorted turn.
I will PM you when I get a bit of time.

Regards, Ian. ::62::


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 9 2019 15:49:58 AEDT PM
  
Hi Muntari, I am sure you have it covered but I do not see a gap in the shielding from the center to one edge of the housing so the shield does not act as a shorted turn.
I will PM you when I get a bit of time.

Regards, Ian. ::62::

Hi Ian,

Yep, have a gap there, its covered with masking tape which is hard to see in photo

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 9 2019 15:51:35 AEDT PM
  
yep im in the clare area mate , will look forward to the updates  ::402:: ::62::

Thanks Alex, yes keeping the weight down is a task in itself isn't it


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Wednesday January 9 2019 15:59:11 AEDT PM
  
yep im in the clare area mate , will look forward to the updates  ::402:: ::62::

Yep, know the area very well, lived not far from Riverton for 10 years, worked in Clare.
Will PM when I'm satisfied with coils and let you try them out maybe . ::05::

cheers

muntari


Title: Re: The need for big deep gold detectors.
Post by: dasenator777 on Wednesday January 9 2019 16:10:21 AEDT PM
im 5 mins from riverton out towards marabell  ::62:: ::62::


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday January 10 2019 12:15:21 AEDT PM
Hi Muntari looks like good work.
I have been looking for a graphic  I think you published.
In reply 351 here you published a graphic for wm6 its a spiral but the outside winding spacings are compressed.
Did you publish a spiral graphic like that one but the turn spacing was equal ?
I've been up and down this thread but cannot find it, would it be possible to post it again please ?
Thanks


Title: Re: The need for big deep gold detectors.
Post by: mylab on Thursday January 10 2019 12:53:38 AEDT PM
It would be interesting on how a large spiral wound DD goes up a against a large spiral wound Concentric and for a fair comparison be the same overall diameter?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 10 2019 15:15:08 AEDT PM
"I have been looking for a graphic  I think you published."

Hi 6666, I'll find it and post no probs.

cheers

muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 10 2019 15:22:51 AEDT PM
Hi 6666,

Is this the one?

If not,let me know the number of turns and spacing, size etc and I'll draw one up for you, no probs..

cheers

muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 10 2019 16:10:24 AEDT PM
6666,

here is the other one

cheers

muntari


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Thursday January 10 2019 16:15:51 AEDT PM
  
6666,

here is the other one

cheers

muntari

Thank you this is what I was looking for , much appreciated.


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 10 2019 16:37:40 AEDT PM
No worries,

Let me know if you need a different template and I'll CAD one up for you

cheers

muntari


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Thursday January 10 2019 16:43:47 AEDT PM
  
It would be interesting on how a large spiral wound DD goes up a against a large spiral wound Concentric and for a fair comparison be the same overall diameter?

Hi Mylab,

Yep, that's in the works too.
One version at same diameter as inner RX, another version at TX size or outer shell size.
Any other ideas let me know and I'll put that on the todo list...

cheers

Muntari


Title: Re: The need for big deep gold detectors.
Post by: mylab on Thursday January 10 2019 19:41:17 AEDT PM
Thanks Muntari.
Look forward to the results.
No other ideas at present.


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday January 11 2019 06:53:54 AEDT AM
  
No worries,

Let me know if you need a different template and I'll CAD one up for you

cheers

muntari

For interest do you cad a spiral by hand or is there a template ?


Title: Re: The need for big deep gold detectors.
Post by: Muntari on Friday January 11 2019 16:48:33 AEDT PM
  
  
No worries,

Let me know if you need a different template and I'll CAD one up for you

cheers

muntari

For interest do you cad a spiral by hand or is there a template ?

No template just function in the applications
I use SolidWorks or Fusion360 depending on the job I'm asked to do. Both have similar tools. They have  helicoil or spiral functions and you set the diameter, pitch and height plus the material size or diameter. Then number of turns.
Other CAD software probably has a similar function but these are the two I use regularly.
Fusion360 is an online use application with a student version or hobby version available still I think for free. You will need 64bit Windows PC but check it out, its ok.


cheers

Mdtoday


Title: Re: The need for big deep gold detectors.
Post by: 6666 on Friday January 11 2019 21:04:24 AEDT PM
  
  
  
No worries,

Let me know if you need a different template and I'll CAD one up for you

cheers

muntari

For interest do you cad a spiral by hand or is there a template ?

No template just function in the applications
I use SolidWorks or Fusion360 depending on the job I'm asked to do. Both have similar tools. They have  helicoil or spiral functions and you set the diameter, pitch and height plus the material size or diameter. Then number of turns.
Other CAD software probably has a similar function but these are the two I use regularly.
Fusion360 is an online use application with a student version or hobby version available still I think for free. You will need 64bit Windows PC but check it out, its ok.


cheers

Mdtoday


Thanks I will check them out, cheers.


Title: Re: The need for big deep gold detectors.
Post by: geof_junk on Friday January 11 2019 22:11:08 AEDT PM
Keep up the good work guys  ::10 ::