My New Pi Metal Detector (ATTiny 25)

[jon-ecm]

So I thought I'd build a pulse induction metal detector.
I scraped some wire from a microwave transformer and wound
about 25 turns on a 8" pan and taped it up good
I also put a 1k resistor between the two leads of the coil
for the TX I hooked up a mosfet to a ATtiny 25 which delivered a pulse about 250 us (going to be adjustable soon)
for the receiver I used another ATtiny 25 with a few diodes for protection, a variable resistor for sensitivity adj, a piezo for sound and a separate powersupply

I'm able to detect a penny at about a foot
and a lead pellet at about an inch
larger objects I can detect at several feet
It dosn't detect a cup of black sand at all but if I put a
a screw or something in the cup of black sand it detects
it like the black sand didn't exist.

Any ideas on improvement? I want to use it to find gold, right now it has less than half a dozen components and the simpler the better!

Thanks!
Jon

[Qiaozhi]

So I thought I'd build a pulse induction metal detector.
I scraped some wire from a microwave transformer and wound
about 25 turns on a 8" pan and taped it up good
I also put a 1k resistor between the two leads of the coil
for the TX I hooked up a mosfet to a ATtiny 25 which delivered a pulse about 250 us (going to be adjustable soon)
for the receiver I used another ATtiny 25 with a few diodes for protection, a variable resistor for sensitivity adj, a piezo for sound and a separate powersupply

I'm able to detect a penny at about a foot
and a lead pellet at about an inch
larger objects I can detect at several feet
It dosn't detect a cup of black sand at all but if I put a
a screw or something in the cup of black sand it detects
it like the black sand didn't exist.

Any ideas on improvement? I want to use it to find gold, right now it has less than half a dozen components and the simpler the better!

Thanks!
Jon

Would you be able to post some photos of your project, and possibly a schematic?
I'm sure many people here would be interested to see what you have achieved.

[bernte_one]

...and the hexfile for attiny too

[TH Jim]

Yes I would also be very interested to have a look at your project - it sounds marvellous!

[jon-ecm]

Pictures!

Here are some pictures of my setup, I will try to upload a video later

Thanks!
Jon

[jon-ecm]

Mess

I guess vBulletin dosn't handle images very wheel **sigh**

You can use Ctrl - to zoom out, at least you can see them that way

I resized them, hope that helps

[jon-ecm]

Pictures

The coils you see are not in use, just ones I tested, the one in use is attached to the window

[TH Jim]

Thanks for the photos of your detector Jon. I like the look of it, particularly the compact size of the circuit. Will you be able to post a schematic and source code so that we can build one too?

Thanks, Jim

[jon-ecm]

Well I just flew by the seat of my pants but I'll make a schematic and release the code.

On another topic If I got pcb's made do you think they would sell?

[bernte_one]

if you put a programmed micro controller to the packet with pcb i would buy some i think

[TH Jim]

I think they would sell, but it might be usefull if a few of us could independantly verify your results first tho - otherwise people might be uncertain what they would be buying.

[jon-ecm]

Schematic

Here's a Schematic of the detector, I think it closely resembles what I've built but if you see any errors let me know. I didn't remember the value of the signal receive current limiting resistor in the rx but I think It's
somewhere around 100k, I'll open up my detector some time and get the exact value.

Good Luck! and if you need any assistance or If I missed something, just let me know

P.S. I'll upload the hex files soon

[simonbaker]

Here are some pictures of my setup, I will try to upload a video later

Thanks!
Jon

Looks like a great snowy-day project to me!

Keep the info flowing.

Regards,

-SB

[pelanj]

Here's a Schematic of the detector, I think it closely resembles what I've built but if you see any errors let me know. I didn't remember the value of the signal receive current limiting resistor in the rx but I think It's
somewhere around 100k, I'll open up my detector some time and get the exact value.

Good Luck! and if you need any assistance or If I missed something, just let me know

P.S. I'll upload the hex files soon

Hi,
it looks like a very nice project. There is one thing missing in the schematic - the audio output. Am I right or just do not see it?

[jon-ecm]

Good Point

Hi,
it looks like a very nice project. There is one thing missing in the schematic - the audio output. Am I right or just do not see it?

Good Point!
I forgot all about that!

I'll update the schematic
For volume control you could put a potentiometer on the speaker leads