My New Pi Metal Detector (ATTiny 25)

[jon-ecm]

Hello,I have recently recieved my USB ISP programmer from China,at this stage it has a ten pin cable with header plug,so I guess I will need to make a board to program the Attinys..
My other question (s), is the sensitivity control the sample delay,or is that fixed in software?
Also the audio is this a type of vco sound ,and is it a motion only detector...
Sorry soo many questions
Thanks ,Looking forward to your reply
John

In this detector the sample delay is what is used to determine the presence of a metal
so it's not necessary on this type of detector.

it's not a motion only detector but eventually i intend to put on some sort of slow ground balance
to compensate frequency drift in the oscillators.

Good Luck!
Jon

http://www.miymd.com

[silverdog]

John

just program your chips on a breadboard, you only need 6 jumper wires

Silverdog

[johnandles]

Thank you for the schematic and code.
I will try to make it soon. Has anyone already made it?

Please tell me what are the encircled components :

Hello,I have recently recieved my USB ISP programmer from China,at this stage it has a ten pin cable with header plug,so I guess I will need to make a board to program the Attinys..
My other question (s), is the sensitivity control the sample delay,or is that fixed in software?
Also the audio is this a type of vco sound ,and is it a motion only detector...
Sorry soo many questions
Thanks ,Looking forward to your reply
John

[jon-ecm]

componets

The diodes you circled are just two diodes placed in parallel and opposite polarity of each other I used two BAT45 Diodes but I don't think it's that big of a deal

The Mosfet you circled should have a breakdown voltage no less than 500V and as low of capacitance as possible <100pf

here are some good looking options

model coss vds current rds(ON)
*FQPF6N60C 65pf 600V, 5.5 A 2 Ohm
FDPF7N60NZ 90pf 600V 5A 1.2 Ohm
*FQPF7N65C 100pf 650V 7A 1.4 Ohm
*FCPF9N60NT 140pf 600V 9A 0.3 Ohm
FDP10N60NZ 150pf 600V 10A 0.75 Ohm

I purchased the ones marked with asterisks but they haven't arrived yet, when they do I'll let you guys know what works best

Right now I'm just using a mosfet scraped off of a computer psu but anything between 400V - 800V capable of at least 5A should work, The lower capacitance the better!

some people have been using the IRF740/840 but it really isn't that important as long as it has a fairly low output capacitance (coss)


If you just want to buy one I'll bet the FQPF7N65C would make a nice switcher
they have it for $.65 at http://tinyurl.com/3px7b6e

Good Luck!
Jon

[pearl]

Thank you

Thank you for the schematic and code.
I will try to make it soon. Has anyone already made it?

Please tell me what are the encircled components :

[jon-ecm]

hex files and updated schematic

I've attached a zip file containing the updated schematic and hex files
if you have any problems or if I've missed something just let me know

Thanks!
Jon

[jon-ecm]

Hex Files

Like to give your design a try...can we see hexfile soon,also is the sample delay adjustable or only in software?
Thanks
John

I have hex files here but I did a bunch of changes and didn't have time to test them and would hate to send something out that had a bug in it.
I''m at work now and will be for the rest of this week but will get those hex files asap.

Btw: I did see another error in the schematic, the two rx lines need to be switched, I'll fix it when I get home...

Thanks for the interest!
Jon

[johnandles]

Like to give your design a try...can we see hexfile soon,also is the sample delay adjustable or only in software?
Thanks
John

[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

[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?

[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

[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

[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.

[bernte_one]

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

[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?