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QED news
QED on facebook
link-https://www.facebook.com/groups/245308699667153/403446933853328/?comment_id=403472030517485&reply_comment_id=403476793850342&notif_id=1562580344994993&notif_t=group_comment
Interfacion Pty Ltd is pleased to announce that the QED PI Detector has been modified to allow the use of DD (double D) coils. This change involves a simple change to the electronics within the control box.
The firmware has also been upgraded to include a further improved Ground Balance.
All detectors being delivered to new customers from Monday 5th August 2019 will already have the above upgrades included.
As a show of commitment to all QED owners, the hardware modification to allow use of the DD and CC coils will be provided at no cost.
Of course and as per the QED warranty, the firmware update is provided free of charge, except for P&H.
Any QED owner who plans to attend the Laanecoorie Bash is encouraged to bring their detector along and have it upgraded at no cost.
Standard postage and handling arrangements apply to other owners. Send via Australia Post the box (minus batteries) along with a pre-paid, pre-addressed bag/box to:
Interfacion Pty Ltd
PO Box 106R
Redan VIC 3350
Howard Rockey
Director Interfacion Pty Ltd.

australian electronic gold prospecting forum.com  |  Detector Technology and Electronics and new detectors  |  Detector Coils (Moderator: Goldman)  |  Topic: The need for big deep gold detectors. 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: The need for big deep gold detectors.  (Read 29606 times)
Muntari
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« Reply #660 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
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Aziz
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« Reply #661 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
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Muntari
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« Reply #662 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


* Hot wire foam cutter_1.JPG (103.06 KB, 640x480 - viewed 301 times.)

* Hot wire foam cutter_2.JPG (87.36 KB, 640x480 - viewed 304 times.)

* Hot wire foam cutter_3.JPG (78.86 KB, 640x480 - viewed 301 times.)
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Muntari
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« Reply #663 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






* 14mm Slices_XPS .JPG (102.72 KB, 640x480 - viewed 259 times.)

* XPS 14mm Shield 18 Inch coil_1.JPG (107.43 KB, 640x480 - viewed 262 times.)

* XPS 14mm Shield 18 Inch coil_2.JPG (74.5 KB, 480x640 - viewed 261 times.)

* XPS 14mm Shield 18 Inch coil_3.JPG (86.46 KB, 640x480 - viewed 260 times.)
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Muntari
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« Reply #664 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



* Coil weight RX.jpg (25.89 KB, 320x240 - viewed 230 times.)

* Coil weight TX.jpg (24.66 KB, 320x240 - viewed 226 times.)
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« Reply #665 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 smile
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Muntari
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« Reply #666 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
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mylab
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« Reply #667 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?

   
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Muntari
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« Reply #668 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
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Muntari
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« Reply #669 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
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Muntari
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« Reply #670 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
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« Reply #671 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
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« Reply #672 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  happy face

Anyways here's the basic idea and please remember, its a draft  happy face

Cheers

Muntari


* TX Shield 464mm_Draft.jpg (745.17 KB, 1315x1319 - viewed 184 times.)
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IBGold
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« Reply #673 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. happy face
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« Reply #674 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


* SRF Circuit Sketch.jpg (37.09 KB, 727x400 - viewed 134 times.)

* Coiltek DD 14.jpg (138.81 KB, 1324x746 - viewed 131 times.)

* Coiltek DD 14-2.jpg (171.19 KB, 1628x936 - viewed 134 times.)

* Coiltek DD 14-3.jpg (185.96 KB, 1654x934 - viewed 135 times.)

* Coiltek DD 14-4.jpg (177.19 KB, 1656x927 - viewed 139 times.)

* Coiltek DD 14-5.jpg (172.59 KB, 1667x940 - viewed 139 times.)
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« Reply #675 on: Saturday March 10 2018 22:23:41 AEDT PM »

Good job on the pics
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Muntari
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« Reply #676 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
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Muntari
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« Reply #677 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
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autitch
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« Reply #678 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


* SRF Calc Study Coiltek DD 14.JPG (79.98 KB, 1124x311 - viewed 128 times.)
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« Reply #679 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
 
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australian electronic gold prospecting forum.com  |  Detector Technology and Electronics and new detectors  |  Detector Coils (Moderator: Goldman)  |  Topic: The need for big deep gold detectors. « previous next »
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