Digital PI (Pulse Induction) metal detector.

I want to build a digital PI (Pulse Induction) metal detector. Which components may be the best for this? I think I'll need a fast and precise AD converter and a fast micro controller to measure the voltage decay and then compare with a normal curve without metal present. ¿Am I in the right way?

Thanks in advance!

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0 michaelkellett over 10 years ago

You've double posted this - I've answered it in the Ben Heck group where I saw it first - you really shouldn't double post.

MK
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0 Former Member over 10 years ago in reply to michaelkellett

You are right sorry about that and thanks a lot.
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0 bobalexander over 10 years ago

You could add a ARMinARM board if you are wanting to utilize the Pi as some kind of interface:
onandoffables / hardware / arminarm / board
The STM32 ARM Cortex-M3 microcontroller 'backpack' would let you perform all the signal sensing and low level processing just passing off data to the Pi...

Most metal detectors utilize a VLF transmitter and receiver to detect the presence of a metal.
They then discriminate between ferrous and non-ferrous materials based on the phase shift of the returned signal. This allows you to tell if the metal you are detecting is a rusty old nail or a gold coin as each type of metal will shift the phase of the bounced signal differently.

Here is a basic overview:
http://www.thomasathomas.com/Metal_detectors_work.htm
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0 michaelkellett over 10 years ago in reply to bobalexander

I think that for the OP, PI means Pulse Induction not RaspberryPi.
But never mind - the board you suggest is quite nice but based on an older STM32 processor which can't convert as fast as some of the more recent parts.

MK
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0 bobalexander over 10 years ago in reply to michaelkellett

Good point - I completely missed that!
I was under the impression that Pulse Induction is not a great option as you can never discriminate out iron.
Perhaps that is what the OP is wanting to detect though...

Good call on the older STM32 - I didn't even think about it not being fast enough for processing signals in the kHz range.
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0 Former Member over 10 years ago in reply to michaelkellett

Yes, PI stands for Pulse Induction, that's the reason why I need fast measurement, see the curve in the figure:
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