How to make the best coil.

[Stevedbk]

Thanks to all for the info.
I originally had the idea to make a gold detector but here in West Au it ain't gonna work unless Minelab helps me. I will finish my Hammerhead to be a beach/ low mineral PI, won't need super short response times.
I don't have the skills to go processor yet. Have learnt a lot, much to go.
Cheers.
Steve

[MartinB]

Have a look at the Mirage posts here on the forum. Designed in Australia as a gold detector

[Stevedbk]

Have a look at the Mirage posts here on the forum. Designed in Australia as a gold detector

I recently went to a meeting of APLA (Aust prospectors & leaseholders assn) and all were adamant that ground balance was essential for the variable mineralised ground. The chances of finding anything is low as almost all known patches have been hammered each time a better detector has been released. I think many of them go bush as a getaway and use gold as an excuse.
I have no doubt the Mirage is an excellent project though I am already getting low response times on the bench. I haven't packaged it yet.
So I will drop the idea of making a gold det for use here although the design may be feasable in other areas.
Thanks
Steve

[Stevedbk]

I will have to learn micros and follow Waltrs "my take on the HH" to get GB.
Steve

[MartinB]

Or you could spend 7,000 AUD on a Minelab.

[David_1]

Or you could spend 7,000 AUD on a Minelab.

Thats just one nugget now with the price of gold

[detectormods]

There is a technique that was to install the coil preamplifier inside the coil housing, i had a look at the Gold Monster where they have the preamplifier and adc inside in coil casing, no more cable capacitance and no more analogue noise interference, i put a vid up on you tube, what do you think about this? Board interaction with the ground and tx rx signals? https://youtu.be/hzR23qpJGBU

[Lucar]

It's the same stuff mentioned on a lot of threads here, 3M 2191FR or equivalent. Off-brand is cheaper and easily found on Amazon, eBay, and AliExpress. Search for "Faraday tape" with maybe 'fabric' and 'nickel'.

Hello Carl,

since I love elliptical coils and those are no more available to buy, I'm trying to rebuild one out of the two 14x8 Miner John mono coils I have for my TDI SL that (both) stopped working after some years of glorious service .

Regarding the use of conductive tape , such as the 3M 2191FR for example, do You know if there is any difference in spiral wrapping it to the coil or wrapping the coil(+spacer) "U" style with the conductive tape ?

I opened one of the coils and I see that the problem is that the coil cable itself is interrupted somewhere in the coil winding; it's a 24AWD cable, I run my TDI SL at 16.8 volts (4s lipo battery), can there be a relationship with the cable interruption?

Thank You for Your help
Luca

[Carl-NC]

I've always spiral-wrapped coils, but I suppose U-style should work fine. The extra voltage probably didn't cause the cable to fail, more likely it was a lot of flexing. The first place to look is inside the 5-pin connector.

[Lucar]

I've always spiral-wrapped coils, but I suppose U-style should work fine. The extra voltage probably didn't cause the cable to fail, more likely it was a lot of flexing. The first place to look is inside the 5-pin connector.

Hello,
thanks for Your answer I think I'll choose spiral winding the shield.
I did find the interruption , it's in the coil winding, as surprising as it can be, there was a solder junction in the cable winding that got oxydized and went in total rust.
I'm suprised there was a joint in the winding itself and even not protected with a bit of heatshrink; I can't otherwise imagine what was the small 1mm blob that caused the cable to fail and cut in the winding. Looking at the blob under a microscope it looks like the geen powder that battery leakage creates on contacts; small bits of cable strands appeared to be there but it was all mostly rotten powder.
I will try to rebuild the whole coil.

Many thanks!
Luca