big shattering in vodoo`s second preamp signal

[Levin]

Hello
my voodo detector doesnt work. in second preamp stage is a massive shattering. in this video you can see how I turn the offset resistor R6 from 0 to 100% of his resistance. yellow is tp5 and blue tp3:

more informations are in this post.
thanks for helping
LG Levin

[Qiaozhi]

R6 is the 1R0 series resistor in the TX circuit. Do you mean R30?
I'm not sure what you're asking here. The scope loses sync about halfway through the video. Is that what you're referring to?

https://www.youtube.com/playlist?lis...Ny2u3m-SRFjPFy

[Levin]

o sorry i mean r30 in about 10 hours I will give a better description

[Levin]

hello
i am a completely beginner in designing own metall detecors. I thoght that the very crude bleu curve from my second pream stage cannot be interpreted by the electronics. I cant see any changes in tp 3 if move a 2€ coin over my coil. is the problen in me or in my setup.
thanks for helping
Levin

[Qiaozhi]

hello
i am a completely beginner in designing own metall detecors. I thoght that the very crude bleu curve from my second pream stage cannot be interpreted by the electronics. I cant see any changes in tp 3 if move a 2€ coin over my coil. is the problen in me or in my setup.
thanks for helping
Levin

Does the signal at TP5 respond to a metal target?
If so, then do you have the jumpers at PL7 and PL8 set correctly?

[Levin]

I think pl7 and 8 are correctly setted. in this video is tp 5 blue and tp 3 yellow. in the first 5 seconds i did nothing. from second 5 to 10 i swing a coin 5 cm over the coil. and in the las 5 seconds I put the coin on my coil:

here is a oszillogramm from tp5 with 50 mv/div. looks that good ?:

thanks

[Levin]

does this oscillogram look good

[Levin]

Hello
please help me. does that looks good. made I a mistake.
Best regards and thanks Levin

[Qiaozhi]

Hello
please help me. does that looks good. made I a mistake.
Best regards and thanks Levin

As I said previously, the scope loses sync so I cannot tell if anything was detected or not.
Trying to debug this remotely is very difficult.

[Levin]

Ok thanks for answer I want ask more accurate
is it normal, that the second amplifier stage`s Signal is after the last part of the coil`s pike so irregular and non periodic, without a piece of metal in the near?
thanks for help and best regards Levin

[Qiaozhi]

Ok thanks for answer I want ask more accurate
is it normal, that the second amplifier stage`s Signal is after the last part of the coil`s pike so irregular and non periodic, without a piece of metal in the near?
thanks for help and best regards Levin

If you're testing the detector indoors, then most probably "yes".
A pulse induction detector's input circuitry is wide-band (that is, not tuned) and is therefore sensitive to external interference.
However, pulse induction detectors tend to be used away from such interference.

[Levin]

Hello
I tested my detector with the detector`s coil in a (bad) faraday shielded room. the results are much better. I got a relativly constant curve. but how I can find out the sample delay. my measuring devices are in the house and I think the measuring devices produces electromagnetic interferences themselves
best regards Levin

[Qiaozhi]

The main sample delay is set in software to 27us.

[Levin]

does the sample delay not dependent on the used coil?

[Qiaozhi]

The default main sample delay is 27us, but you can adjust the delay in the menu system from 15us to 50us.
Carl ported the software from Mikro-C code to the MicroChip XC8 compiler. One of the improvements he made was to keep the detector running while the menus are being adjusted. You might find it easier to adjust the delay using this version -> XC8 C code