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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. 0 Members and 2 Guests are viewing this topic. « previous next »
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Author Topic: The need for big deep gold detectors.  (Read 28580 times)
Aziz
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« Reply #700 on: Saturday March 17 2018 06:06:03 AEDT AM »

Hi all,

my bull-sh1t-meter worked obviously totally wrong. No!, it worked perfectly.  JESTER
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.
 excited
Cheers,
Aziz
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autitch
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« Reply #701 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
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Muntari
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« Reply #702 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
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IBGold
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« Reply #703 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. happy face
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Regards, Ian.
Muntari
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« Reply #704 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 happy face
Do you find the XPS brittle or flaky or is it working Ok for you.

cheers

Muntari
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IBGold
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« Reply #705 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. happy face
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Regards, Ian.
Muntari
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« Reply #706 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 happy face

Cheers

Muntari
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WM6
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« Reply #707 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:

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Muntari
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« Reply #708 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
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WM6
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« Reply #709 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.




Depend on solder type used (tip bore) some modified copper nails can be used too:



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Muntari
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« Reply #710 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
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IBGold
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« Reply #711 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. happy face
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Aziz
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« Reply #712 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. happy face

Hi Ian,

this is really very nice. (So we have some more margin up to 500 ┬ÁH 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. 
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
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Muntari
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« Reply #713 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. happy face

Hi Ian,

That's great news, much better, well done.

Cheers

Muntari
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Muntari
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« Reply #714 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. good luck
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
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gef12
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« Reply #715 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.
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Muntari
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« Reply #716 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


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gef12
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« Reply #717 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      
Will get back into it in week or so as still doing cyclone clean up after Markus ....
cheers for now





Cheers

Muntari



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gef12
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« Reply #718 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. happy face

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
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IBGold
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« Reply #719 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. happy face
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Regards, Ian.
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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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