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Arduino based pulse induction metal detector

My Arduino-based MD in action:;)
tgts_160514.jpg
 
Using the laboratory bench, as a digital oscilloscope, I took a series of waveforms for my MD on Arduino.
The voltage on the search coil -
foxyPIv2_Ucoil.png
 
New version of MOSFET driver:
foxyPIv2_drv_4.png

It combines speed and performance at lower supply voltage.
 
With IR4427 has turned a strange thing - a metal detector began to react on literally everything - my body (I'm not the Terminator)))), touching to the connectors, to the coil... I went back to version 3 with HCPL-3120.
 
I solved the problem with the driver, add a filter capacitor and inductor (replaced driver IC for the best - TC4420):
foxyPIv2_drv_4_2.png

MD works fine!
 
Here's a demo - the signal output from the op-amp:
ADC_tgts_curves_1.png

Since the op amp gain is small for stable operation of the comparator circuit, then for clarity using large targets placed in the coil - 1 (without target), 2 (beer can), 3 (dumbbell).
Taking the curve of exponential function, defined for fun time constant for dumbbell - 84 microseconds.
P.S. I went back to the old version of the driver:
foxyPIv2_drv_2.png

This circuit is the most stable.
 
Way to build your own PI! I've thought about buying a PI kit off eBay and putting it together but keep thinking to just keep an eye out for a good deal on a used one.

Pretty cool building your own :thumbsup:
 
The third version of pulse metaldetector on Arduino Nano (FoxyPI v3) (transition to the use of the Arduino ADC and dynamic mode) is ready.
Firmware (hex-file) and description (on russian, edited under the third version) -
https://acdc.foxylab.com/node/47
Test video -
 
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