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.