LOOKING FOR GOLDSCAN 4 Schematic.

[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.

[daniel. z]

Did you reverse-engineer it yourself?

[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.

[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.

[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.

[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.

[Orbit]

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.

[daniel. z]

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

[eduardo1979]

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

[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]

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.

[tuntunlin]

Why don't you make the GS-5?
In my opinion it is a better detector than the GS-4.
In the past I made a LITE version of GS-5 and it worked very well.
My LITE version has the identical time base as TDI SL.
The VCO is very nice, because it has a CD4046.

https://youtube.com/shorts/2tXTbySBUD4

Dear Eduradro,

I hope you are doing well. Please take your time to reply whenever you are free.

I am currently building a GS5 Lite metal detector. I have already set the 4 simple timing components accurately. For the coil, I am using a self-wound 8-inch coil with 24 AWG wire, wound 27 times, and I have tested it. I also adjusted the waveform at the output of the NE5532 to be correct.

However, when I test it with a metal target, it only responds at a very short distance.

What I would like to know is:

1. What is the correct specification/ratio for the coil (wire gauge, diameter, number of turns)?
2. What is the correct frequency (in kHz) that should be set on the NE555 timer?
3. At the output of the NE5534, what should the DC voltage and AC voltage be approximately?

If there are any other more precise details or adjustments I should consider, I would also greatly appreciate knowing them.

Thank you very much for your guidance.

[tuntunlin]

Dear Eduradro,
I hope you are doing well. Please take your time to reply whenever you are free.

I am currently building a GS5 Lite metal detector. I have already set the 4 simple timing components accurately. For the coil, I am using a self-wound 8-inch coil with 24 AWG wire, wound 27 times, and I have tested it. I also adjusted the waveform at the output of the NE5532 to be correct.

However, when I test it with a metal target, it only responds at a very short distance.

What I would like to know is:

1. What is the correct specification/ratio for the coil (wire gauge, diameter, number of turns)?
2. What is the correct frequency (in kHz) that should be set on the NE555 timer?
3. At the output of the NE5534, what should the DC voltage and AC voltage be approximately?

If there are any other more precise details or adjustments I should consider, I would also greatly appreciate knowing them.

Thank you very much for your guidance.

[tuntunlin]