Implement Metal detector circuitry in LabVIEW

[DPARK]

Hey,

I already optimized the coil and built up the new circuitry. I didn't get any good results and the oscillating signal from the receiver coil is back (withal the parallel 100k resistor).

But I couldn't get the DO working, so I tried it with the counter-output of 6V again....

Here is some data:

Tx-Coil: Frequency: 847.4 Hz

Period: 1.18 ms

Mean V: 2.56 V

Pk-Pk: 6.0V

Rx-Coil: Frequency: 63 kHz

Period: 16 us

Mean V: 20 mV
Pk-Pk: 1.2 V

Unfortunately, that's totally another result as in the software from Henrik... 😞

Best,

Simon

[Henrik_Volkers]

Last night, after all my wifes (I have three daughters) fall asleep, I build two coils (about 100mm diameter and 100Ohm of 0.2 mm wire , didn't count the turns .. used a cordless screwdriver 😛 , together with tape , shielding, tape  it took about 30min to build them) and heated my old scope and a my old Wavetek mod. 116 generator.

I'm addicted to LabVIEW, but on the bench I prefer knobs... menus belong to restaurants 😉  (stolen from Jim Williams, linear.com, appnote 128 or so)

Resonance of the sending coil was at about 50kHz.

After adjusting the read coil for minimum read and using square wave excitation @ resonance I was able to detect a (copper) coin at 3cm ,  a nail or my solder coil at 8cm.

Minimum read was about 5mVpp and 10mVpp with the copper coin at 3cm over the center  🙂

To get the best sensitivity drive the coil in resonance  -> more current in the coil, stronger magnetic field) , you can use the analog output to drive the FET with a square wave at resonance. Remove the diode and resistor ( maybe replace it with a capacitor to move the resonace) and observe the voltage over the FET, it shouldn't  go higher than 20V (or use a FET with a higher voltage (U_DS) rating. 

More later...have to do some serious work now 😉