LOOKING FOR GOLDSCAN 4 Schematic.

[David222]

Hello. I used an original Minelab 8" Mono coil, which had an inductance of 300uH and a resistance of approximately 0.4 Ohms. The value of the damping resistor is very important, and I believe it was 680 Ohms, if I remember correctly. You can solve this by using a potentiometer and a couple of coupled resistors. Connect this assembly where the damping resistor is located, and with the help of an oscilloscope, find the corresponding value. With the coil connected and far away from any metallic object, the output of the 5534 should read as close to 0 Volts as possible. The frequency is variable, as there is a potentiometer to adjust it. Around 2.8kHz is fine. You should carefully measure the +5V supply, as it comes from the charge pump, which is synchronized with the detector's frequency, and this voltage should not vary with changes in frequency. That's why the frequency potentiometer should be 1K, no more, to avoid unpleasant surprises.

Hi Eduardo. I hope you're doing well. I built the GS5 LITE. This device is great. Of course, I haven't taken it outside yet. But on the lab table, with a 30CM coil, 2-ohm resistance, and 400uH inductance, it detects a coin with a diameter of 28CM at a distance of 35 cm. I chose a damping resistor of 330 ohms. Please tell me how to adjust the resistor with an oscilloscope. I appreciate your big heart and the kindness you’ve shown.

[eduardo1979]

https://youtu.be/Gr__N4_k2Mc?is=XYbn6VuTytl5RnOR

[daniel. z]

Hi has anyone ever reverse-engineered the TDI metal detector?

[GeoMax]

Hi Daniel,

check it out... TDI project - Geotech Forums There you can find the schematics.

[Orbit]

Hi has anyone ever reverse-engineered the TDI metal detector?

[tuntunlin]

Hello. I used an original Minelab 8" Mono coil, which had an inductance of 300uH and a resistance of approximately 0.4 Ohms. The value of the damping resistor is very important, and I believe it was 680 Ohms, if I remember correctly. You can solve this by using a potentiometer and a couple of coupled resistors. Connect this assembly where the damping resistor is located, and with the help of an oscilloscope, find the corresponding value. With the coil connected and far away from any metallic object, the output of the 5534 should read as close to 0 Volts as possible. The frequency is variable, as there is a potentiometer to adjust it. Around 2.8kHz is fine. You should carefully measure the +5V supply, as it comes from the charge pump, which is synchronized with the detector's frequency, and this voltage should not vary with changes in frequency. That's why the frequency potentiometer should be 1K, no more, to avoid unpleasant surprises.

Thank you very much, Eduardo.

So the NE5534 output should be at 0V DC and the waveform must be correct as well — I understand now. I will do my best to get it right.

[tuntunlin]

Dear fellow builders and mentors who have successfully constructed the GS5 Lite,
I would like to kindly request your help in answering this question.

On my GS5 Lite, I have already adjusted the NE5534 output to 0V DC and the waveform is now correct. The 4 sampling timing components have also been set accurately.

Based on my current tests, the detector only responds to a metal target up to a distance of about 8 cm.

Therefore, I would like to ask: are there any additional adjustments or specific balanced voltage reference points that I should check?

To be more specific, I am referring to the expected voltage values at the pins of ICs such as the TL072, TL064, and LT1114. Could you please advise what the proper voltages should be at those points?

My coil is 300µH, and the damping resistor is 470 ohms.

Thank you very much for your time and guidance.

[Emersonpaz]

If you have a clear photo of your board with the ICs mounted and everything looks correct, it seems like you might be using a counterfeit IC.

[daniel. z]

Hi Daniel,

check it out... TDI project - Geotech Forums There you can find the schematics.

Hi GeoMax
I checked this schematic and apparently it has a series of errors, especially in the samples.

[daniel. z]

Did you reverse-engineer it yourself?

[daniel. z]

Dear fellow builders and mentors who have successfully constructed the GS5 Lite,
I would like to kindly request your help in answering this question.

On my GS5 Lite, I have already adjusted the NE5534 output to 0V DC and the waveform is now correct. The 4 sampling timing components have also been set accurately.

Based on my current tests, the detector only responds to a metal target up to a distance of about 8 cm.

Therefore, I would like to ask: are there any additional adjustments or specific balanced voltage reference points that I should check?

To be more specific, I am referring to the expected voltage values at the pins of ICs such as the TL072, TL064, and LT1114. Could you please advise what the proper voltages should be at those points?

My coil is 300µH, and the damping resistor is 470 ohms.

Thank you very much for your time and guidance.

Change the damping resistor from 330 ohms to 660 ohms and check the results to see if any change occurs.
As Emerson would say, maybe the ICs are counterfeit.

[Orbit]

Јеси ли сам урадио реверзни инжењеринг?

Not with a friend. After that I repaired the pcb because without modification the gnd was unstable. The excess drawing was thrown out which is not used at all. Karl helped me with the voltage drop.

[daniel. z]

Not with a friend. After that I repaired the pcb because without modification the gnd was unstable. The excess drawing was thrown out which is not used at all. Karl helped me with the voltage drop.

That's great, good luck.
I've decided to build it
do you think it's worth doing?

[Orbit]

8

That's great, good luck.
I've decided to build it
do you think it's worth doing?

I think it's worth it, but only in places where there are a lot of minerals in the ground, so it's not for every day. For certain places it is ok. Not too deep I did an 8 inch coil. And I have the original coil of gs 5. The Sl is perfectly silent at maximum sensitivity and can find coins under nails and debris where all possible vlf devices can absolutely not match it.Otherwise the proto TDI scheme is completely correct as put by Altra! TDI or Proto TDI is a bit deeper but also more noisy!

[daniel. z]

8

I think it's worth it, but only in places where there are a lot of minerals in the ground, so it's not for every day. For certain places it is ok. Not too deep I did an 8 inch coil. And I have the original coil of gs 5. The Sl is perfectly silent at maximum sensitivity and can find coins under nails and debris where all possible vlf devices can absolutely not match it.Otherwise the proto TDI scheme is completely correct as put by Altra! TDI or Proto TDI is a bit deeper but also more noisy!

So, does the TDI Proto design work perfectly? Do you have the SL design yourself?
I wanted to buy a TDI SL and start reverse engineering the circuit from it, but unfortunately I couldn't find one.