Having fun with ARM and fast ADC

[Geremia]

Hi all,

i'm new in metal detecting, i just saw my brother playing with diy metal detectors, and i tought: i've some arm board laying around here, let's have some fun!

I'm not going to catch any relic with it, i just wanted to see that damn decay curve

[Davor]

Nice one. You can observe the target time constant this way as well. Guess it requires a lot of processing to get you there.
Are you going to share this solution somewhere? At least as a block diagram?

[Geremia]

Well, i'm still in sw developing (this is where i get fun), so premature to share, but in real it's old concept.
The external hardware is quite elementary, basically a dirt homemade unshielded coil, a mosfet, couple of diodes, damping resistor, opamp at 1000 gain and then go directly to the 10$ arm board that just acts like an oscilloscope, it samples an initial curve when calibrating, then loops in sampling and comparing with the reference curve, the yellow curve shows the difference in voltage on each time slot (about 250ns each dot).
Processin power is not an issue, it takes more time to plot the 6$ tft display with spi interface.

I've understood that main problems for a MD are coils and noise, this is where the most R&D take place, "hat off" to those people.

[6666]

Thats a great project please continue.