TGSL Tuning & troubleshooting

[folharin]

The tgsl detector has always been my favorite! I think I've built about 15 devices so far. The inductances never worked for me. At the time of winding they were correct, but after tightening them with insulating tape and applying aluminum tape they always gave different measurements I always adjusted the null of the coils by testing with different metals

[cristiano.sar]

One doubt about the ~30cm distance for a 1 euro coin, is this value usually got with coils shielded or unshielded? What position of ground balance pot? I'm asking this because I'm testing nulling the coils without shield (because I want to put the graphite in the coil shell later). Thanks.

[vas]

Hi everyone,
The synchronous detectors work very well and extract the useful signal from the noise. This is my experimental model, it detects 1euro from 32cm, it discriminates and large targets are also detected from 1m!
I'm trying to make a reproductible printed circuit in China and maybe change the sound. Thanks to those who made this interesting experience possible.

[dbanner]

Graphite is demonstrably better.

https://m.youtube.com/watch?v=XnrStRklcUQ&t=8s

[waltr]

Hi Waltr,
Thanks for reply.
Is the graphite shield better than the one with aluminum foil?

I did build coils with Alum and graphite shields. The performance difference was barely noticeable but the Graphite is better.
However, I may have simply done a better job on the coils and nulling of the one shielded with graphite rather than the graphite making it better.

[vas]

Hi Waltr,
Thanks for reply.
Is the graphite shield better than the one with aluminum foil?

[waltr]

Hi,
Is correct to connect a pole of Rx coil to ground, like in picture attached?
Thanks.

I did connect ground like in the picture. You do need to experiment to find if it is better or not with ground connected.

[vas]

Hi,
Is correct to connect a pole of Rx coil to ground, like in picture attached?
Thanks.

[vas]

Thanks for the tips.
I read that a version of this project is with multiple tones. Does anyone know where?
I can find documentation for this?
I want to make the best version of this project, to make the printed circuit (gerber files), to publish them here, so that anyone who wants a metal detector can execute them in China(Allpcb, Pcbway, ... ).
Awaiting a reply,
best regards to all.

[folharin]

the tgsl project presented better results than minelab safari and equinox and fisher f5

[folharin]

minha regi?o solo mineralizado..muito dif?cil de detectar

[folharin]

I built about 10 devices always with the double coil

[waltr]

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.

That is correct, at U101-7 the change in signal is very tiny. The next two RX stages add gain plus has synchronous detection, JFET switches.

[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.

[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.