Arduino metal detector?

[FoxyLab]

Specified weight: 55 - 60 grams
Density: 3,6 - 4 grams per cubic cm

[FoxyLab]

Finds in the garden with FoxyPI after electrolytic cleaning:

[FoxyLab]

I have drawn FoxyPI v3 schematic in KiCad (see attached image for zoom):

[6666]

I have drawn FoxyPI v3 schematic in KiCad (see attached image for zoom):

Thanks

[FoxyLab]

I built a model of the entire power part of my metal detector for LTspice XVII:
FoxyPI_v3_tran.asc

You can play with the parameters and watch, for example, the voltage on the search coil (1), on the ADC input (2), the current in the coil (3):

[Eddy71]

OpAmp LM358 too slow for PI-detector

[FoxyLab]

OpAmp LM358 too slow for PI-detector

Probably it is.
But he is trying very hard. :-)
All this device is a compromise between extreme simplicity and acceptable sensitivity and stability for me.

[FoxyLab]

The final firmware version 3.4 is ready - FoxyPIv3_4.ino.eightanaloginputs.hex
What's new:

• MOSFET overheating is excluded
• increased stability
• added auto-tuning interval between ADC samples
• added display of the signal curve after auto-balancing

And here is how the interference from a nearby LCD TV appears:

[FoxyLab]

Video illustration of metal detector starting procedures:

[Vadim18]

OpAmp LM358 too slow for PI-detector

Yes, thats why im wondering to! But in opposite shorter bandwidt will produce a less noise) Of course analog part of this detector is less good than digital, so simply placing ne5534 instead of lm358 will boost sensivity. Also high-pass RC filter with R10k and C 0.1 uf beetwen op amp and atmega will be nice, as it help to reduce low frequency noise. I think at nowedays lm358 is one of the best op amp for flicker noise generator project

[Vadim18]

FoxyLab make a nice project. At least simple and good as reference for comparsion.
Sory i forget about common mode voltage range limitation, ne5534 will not work here, tl071 will do.

[useus]

The final firmware version 3.4 is ready - FoxyPIv3_4.ino.eightanaloginputs.hex
What's new:

• MOSFET overheating is excluded
• increased stability
• added auto-tuning interval between ADC samples
• added display of the signal curve after auto-balancing

And here is how the interference from a nearby LCD TV appears:

Congratulations for the project, I would be curious to try an adaptation of your software on the felezjoo pi circuit (same avr of your project, similar but different scheme but I think easily adaptable)

[FoxyLab]

Thanks!!!

The FoxyPI firmware version 3.5 is ready - FoxyPIv3_5.ino.eightanaloginputs.hex

What's new:
added the ability to adjust the display contrast using the CONTRAST item in the service menu

An example is small/normal/excessive contrast:

[FoxyLab]

Congratulations for the project, I would be curious to try an adaptation of your software on the felezjoo pi circuit (same avr of your project, similar but different scheme but I think easily adaptable)

Interesting challenge

[useus]

Interesting challenge

I hope you will!

Maybe with nokia lcd it would be great!