Threshold Pot doesn't work

[MartinB]

Unfortunately, it is not at my country.

Sent you a PM

[Carl-NC]

It sounds like maybe the EFE cancellation isn't working. Make sure you have correct EFE sample pulses.

[h9361]

Hello
Dear Walter.
I have a question about your experience with Voodoo project.
I had some tests with small objects. I think it can't discriminate Small objects that is near coil (3-5cm).
But it discriminates big object very nice.
Had you such experience like me?
Thanks.

[h9361]

Is it possible for my Coil?

[waltr]

I have not done much with the VooDoo and it has been some time since I did (over a year).
From what I remember is it did Disc ferrous verse non-ferrous on coin and nail sized objects.

Could be the coil and/or the cap added. I had used one of the IB PI coils I built for the HH2. I did need to try various Caps to get it working.
Re-read the book and experiment.

[Qiaozhi]

As waltr said, Voodoo has no problem discriminating small ferrous targets close to the coil.

[h9361]

Thank you Dear Walter and Qiaozhi.
I used capacitor that resonance frequency is calculated 10KHz.
So, it's better i build another concentric coil with different inductance.
I saw a test video in youtube, i'm trying to use its inductance values.

[h9361]

Dear Qiaozhi
I measured Voltage TP5, is it true?
Primary voltage (no target) = 0.140 - 0.150V

Detecting Target:
Minimum voltage = -5V
Maximum voltage= +5V

[Qiaozhi]

Dear Qiaozhi
I measured Voltage TP5, is it true?
Primary voltage (no target) = 0.140 - 0.150V

Detecting Target:
Minimum voltage = -5V
Maximum voltage= +5V

I'm not sure what you're asking.
Have a look at the TP5 signal using an oscilloscope.

[h9361]

Hello
Dear Carl.
I have a question about shield of PI coils.
Some people and companies (like Minelab) insist to use Graphite powder and other prefer to use Very thin aluminum (foil).
I tested ohm of GPX shield (graphite), it's near 200-500R, while ohm of pure metals like aluminum foil is near 1R!
Is it possible to tell me your opinion about this?
Thanks.

[kt315]

and the depth will be better or you hope to get better protection? what is your aim?

[h9361]

Hello
Dear Carl.
I have a question about shield of PI coils.
Some people and companies (like Minelab) insist to use Graphite powder and other prefer to use Very thin aluminum (foil).
I tested ohm of GPX shield (graphite), it's near 200-500R, while ohm of pure metals like aluminum foil is near 1R!
Is it possible to tell me your opinion about this?
Thanks.

Dear Carl
I hope you tell me your opinion.
Thanks.

[Carl-NC]

For PI you don't need a metallic shield but you do need a fairly low impedance shield. If you use carbon shield paint then use multiple thin coats. My personal preference is polyester fabric tape with copper-nickel plating, it's much easier to work with. 3M 2191FR is an example, Ali Express has cheaper options.

[h9361]

For PI you don't need a metallic shield but you do need a fairly low impedance shield. If you use carbon shield paint then use multiple thin coats. My personal preference is polyester fabric tape with copper-nickel plating, it's much easier to work with. 3M 2191FR is an example, Ali Express has cheaper options.

Thank you dear Carl for your information.
Unfortunately, it's not in my country.
I searched in Ali Express, but it also is not in it.

[h9361]

Sorry for my questions.
As you know, we use foil over coil with a gap.
Do you think we still need the gap with copper-nickel plating?
And, should i connect the plate with a wire to ground?
Thanks