TGSL Tuning & troubleshooting

[ripsdevala]

Im using concentric, above 5cm all medium size iron is not detected, but will detected when very close to the coil

[homefire]

ripsdevala. Please start another Thread. This one has about run it's course.

[Nandor]

Than your coil works just good.

[ripsdevala]

Ok then, thanks all

[Nandor]

I have built a new TGSL, the Geb circuit makes sawtooth waves instead of square wave. The Disc works fine, I just can't figure out why. If someone has ideas please post.

[Tibuck19]

I have built a new TGSL, the Geb circuit makes sawtooth waves instead of square wave. The Disc works fine, I just can't figure out why. If someone has ideas please post.

Because you TGSL is made to detect in the woods lmaoo all jokes aside, id like to know too, as my TGSL its so square wave either, it not saw tooth but is not perfectly square either.

[Nandor]

I've changed the passive components, comparator is tested also but the problem is the same. The disc has nice adjustable square wave but the Geb is a sharp saw like waveform.

[vas]

Hello everyone,
I am a beginner in the field of metal detection, but because I find this project very interesting, I decided to do it. But I didn't take too many steps (I made the coils, the signal generator and the Rx signal amplifier) and I stopped. I don't know:
1. Is there a null signal at the exit U101a-pin7 ? ,
2. Is the output signal processed as phase and / or amplitude?
3. What to look for when checking the floor with Tx, Rx, U101a ? From the adjustment of the position of the coils I obtained a "null" of only 200mV at output of U101a, is it enough?
Thank you for any suggestion.

[waltr]

Hello everyone,
I am a beginner in the field of metal detection, but because I find this project very interesting, I decided to do it. But I didn't take too many steps (I made the coils, the signal generator and the Rx signal amplifier) and I stopped. I don't know:
1. Is there a null signal at the exit U101a-pin7 ? ,
2. Is the output signal processed as phase and / or amplitude?
3. What to look for when checking the floor with Tx, Rx, U101a ? From the adjustment of the position of the coils I obtained a "null" of only 200mV at output of U101a, is it enough?
Thank you for any suggestion.

did you download and study the TGSL 101.pdf document?

1-yes. I use RX amp output to measure coil Null and Phase.
2- Both Phase and amplitude are used in DISC mode.
3- 200mV at U101-7 maybe good. Phase is also important and for a DD coil should be about 20 degrees between TX and RX.
Does the TX and RX coils when connected to the TX circuit oscillate at the correct frequencies? This is very important and tells you the coils are correct.
If phase is way off at the Null then adjust the RX Coils C value.

[vas]

Thank you Waltr,
I promise I will read the pdf document very carefully. These are the signals Tx and U101, pin7. I think I need to change the phase of the Rx coil, right?

[vas]

Channel Tx is 1:10, channel U101 pin7 is 1:1.

[vas]

Hi Waltr,
These is new Tx and U101a pin7 waveform. Is it ok with the phase shift between them? Unfortunately, the voltage at output U101a cannot drop below 200mV a.c.
Thanks again.

[ArchibaldSTM]

Normally

[waltr]

Last scope images look good. The first had a 180? shift which is usually fixed be swapping the RX coils leads.

I'd say it is time for you to put more parts on the board.
Next check is the JFET switch driver (gate) . Then the RX op-amps.

[vas]

Thanks all.
Sorry, my 200mV is peak to peak, I have only 60...70 mV RMS!
Now I have more courage to add another block or two.
However, a 1 euro coin at > 10cm has no visible effect on the signal from output 7 of the U101a.
I will see.