Superscan PI

[ZOUjiarui]

I have to get to the task at hand: superscan, readjusting another detector, which is still quite difficult for me.

[eduardo1979]

Hello eduardo1979, I would be very happy to build a ground-balanced metal detector, like the SD2000, or a genuine GS6, using an 80cm diameter detection coil. I'm not sure if the GS5Lite is suitable for large coils.

The GS-5 LITE requires some modifications to function properly with 80cm x 80cm or 1m x 1m frame-style coils. This detector operates at a very high frequency and is designed for small, low-conductivity objects. The frequency would need to be lowered, the first main sample delay increased to over 40µs, and the synchronization times adjusted, similar to the GS-6 or Superscan.

[ZOUjiarui]

Hello eduardo1979, I would be very happy to build a ground-balanced metal detector, like the SD2000, or a genuine GS6, using an 80cm diameter detection coil. I'm not sure if the GS5Lite is suitable for large coils.

[eduardo1979]

It's very likely that the MOSFET overheating is due to the 24V voltage, as our colleague NASIOS stated. I built the Superscan, but I never powered it with 24V. My Superscan was powered by 12V, and I remember that the MOSFET didn't get hot at all; it was just lukewarm. I used an IRF840, as it has a higher breakdown voltage than the IRF740. I recall that the depth of my Superscan was quite good; it detected a 33mL can of Coca-Cola at a depth of 1.5m with a 1m x 1m frame coil. I did this test in a moderately mineralized soil section. The coil had two turns of Category 5 UTP cable, which is a total of 16 turns, since the cable has 8 wires. I don't remember the value of the damping resistor, but it's quite important, as it can greatly influence the detector's depth. I used an NE5534 in the preamplifier. It's also important that the op-amp be original. I'll repeat that this detector isn't suitable for searching in highly mineralized clay soils, like red clay. For that, you need a detector with ground balance. I abandoned this project many years ago for this very reason. If you want a good detector that's suitable for all types of terrain, you can opt for the GS-5 Lite with the same timings and operating frequency as the Superscan. Don't waste your time and money on things that have already been tried and tested and didn't produce good results.

[ZOUjiarui]

Hello, I retested the coil waveform, and it's not a square wave; it's not normal.

[nasios]

hell The damping resistor is 150Ω, and I'm not very familiar with using oscilloscopes yet. I can't zero the 061 and 072, and the 740 keeps getting hot, but it hasn't burned out.

is normal to be hot is 24v, now i look your youtbe video and i look you use to many wire cable, maybe make capacitance
look this video for help you with R

https://www.youtube.com/watch?v=Gr__N4_k2Mc&t=3s

[ZOUjiarui]

hell The damping resistor is 150Ω, and I'm not very familiar with using oscilloscopes yet. I can't zero the 061 and 072, and the 740 keeps getting hot, but it hasn't burned out.

[GeoMax]

Can you change the time base on your oscilloscope? Then you can see better the coil decay path. Maybe the damping resistor is not right.

[ZOUjiarui]

https://youtube.com/shorts/baPQpnV0dMY?si=BOJGUrRl3_0wKN-z

2

[ZOUjiarui]

https://youtube.com/shorts/6s5XVtqB-vM?si=szICPJaxbzlC65FC

[ZOUjiarui]

The depth is good, but the coil waveform is not quite normal.https://youtube.com/shorts/6s5XVtqB-...RGd4gyDwIWXTUD

[ZOUjiarui]

A diameter of 0.5 mm² is approximately equal to 0.8 mm; I will try again. We cannot find any information about the original small coil.

[ZOUjiarui]

The inductance is only 460uH, while Eric's data shows 500uH and 1.5Ω, which should be the specifications for a large coil. I was originally using a 1-meter long 30-core cable with 0.5mm² copper cores per strand, an inductance of 520uH, and 1.2Ω, and it also had noise; I suspect it had large parasitic capacitance. Now I've disassembled it, and the inductance is only around 420uH. I'll reconnect it and try again. It's also possible that interference from household appliances is causing the problem.

[nasios]

Yes, it's operating at high power. The coil might be unsuitable; it's wrapped in paper. The diameter is 10 cm, the resistance is 1 ohm, and the wire diameter is 0.6 mm. After adjusting the frequency, it's indeed much more normal; a 2W high resistance can be detected at around 5 cm. I'm glad it's working fine; the rest is just precise adjustment, which is also difficult.

i think you have try with other coil bigger size and maybe bigger wire 0.8
before many year i build a coil for demagnetization and make noise, after i use bigger wire is stop, i am not sure if you are in same problem but i say maybe is this

[ZOUjiarui]

Yes, it's operating at high power. The coil might be unsuitable; it's wrapped in paper. The diameter is 10 cm, the resistance is 1 ohm, and the wire diameter is 0.6 mm. After adjusting the frequency, it's indeed much more normal; a 2W high resistance can be detected at around 5 cm. I'm glad it's working fine; the rest is just precise adjustment, which is also difficult.