Tesoro Bandido - 18,5Khz - To find small gold nuggets

[Andre]

Forum friends! I decided to present here my project to modification the famous Tesoro Bandido II U-max, to find small gold nuggets. After countless attempts, I managed to arrive at this project that surprised me! I leave your outline published here for your analysis. A CA3140 op-amp was used to generate a sinusoid wave with adjustable frequency. I used a type D coil with 17cm in diameter and 28 AWG wire. 9.12mH for the receiver and 9mH for the transmitter. The receiving coil was covered with metallic adhesive tape and grounded to the circuit's GND. You may think that the set is out of resonance frequency, but, incredibly, that's how it worked best.
The op-amps must be the same as in the diagram shown. Attempts with equivalents left the circuit with less sensitivity.
I appreciate any comments or constructive criticism.
Tesoro Bandido 18500Hz.pdf

[MartyJ1963]

Hiya Andre,,,Is there a PCB Layout available for your version please? Thanks, Regards, Marty.

[Andre]

Unfortunately not. My PCB was hand-drawn and profoundly altered, as it is a prototype. It looks horrible but is functional. Follow the photos.

[Andre]

I will send a video, as soon as possible, of its operation. A negative power supply made with ICL7660 was causing a lot of noise in the circuit. So I chose to use Li-ion batteries with LM 7806 and LM 7906 to regulate and make the voltage stable.

[MartyJ1963]

Thanks for your reply Andre. Do you have a drawing of your pcb? Maybe I could re-draw it and replicate it in Sprint Layout? Regards, Marty.

[Andre]

I will try to draw, but this is very tiring. I had a lot of trouble designing the layout in LTspice. This schematic was my first in this software. It does not contain errors of component values or wrong interconnections. I just forgot to indicate pin1 of U4 - input after R9. Could the .asc file help you?

[MartyJ1963]

Hi Andre. I'm not sure what a '.ASC File' is and I'm not familiar with LTspice. If you could draw the PCB accurately by hand and place the components appropiately I could then redraw it in Sprint layout and be able to remake it and produce Gerber files. Thanks, Regards, Marty.

[Andre]

The file must be corrected. I don't know how to make it simulable.

[MartyJ1963]

Hi Andre, I have never used asc file and don't know how to open it. Regards, Marty

[Andre]

I understand! I'll try to draw him! But soon.
Thank you for your interest!
Andre.

[MartyJ1963]

Ok Andre, No probs. Thanks, Marty.

[bgs]

This oscillator circuit does not work

[SWL]

This is a simplified version of the generator from the Admiral. We must do the full, probably

[Andre]

Dear bgs,
This is very strange! I've used this setting many times. Only works with the CA3140. Did you build the oscillator or just do the simulation?

The theoretical world is different from the practical one!

[Andre]

I am posting the photos of the "unlikely" oscillator that our dear bgs said does not work.
The frequency is a little lower than the original frequency because I'm testing it on another coil.



Some time ago in history, someone said: "Blessed is he who believes without seeing!"