My Pulse Oscillation detector project.

[johnandles]

Hi John,
There is nothing special about programming the hex. You may experiment with the parameters in asm file if you wish to tune: the sensitivity and compref(comparator reference voltage).
Looking forward to hear how you are doing.

Hi Teemo,
So far I have uploaded hex to the pic.(my programmer finally arrived..xmas delay?)
I have also etched and drilled the pcb drawn by APberg.
Still collecting parts.
Having a few problems with a 7.5mm spacing for C1 etc in that value.
I can find 'greencaps'.
For a proto..would they be suitable?
Also I noticed on your site, a comment about the coil specs.
I have mainly home wound coils to suit surf p.i. etc
around 400uh.
I see you recommend changing C1 value. above 110uh
Can you advise what parameters for C1 value to suit different coil uh's?
Or maybe in software .
Cheers
John

[Teemo]

Hi Teemo,
So far I have uploaded hex to the pic.(my programmer finally arrived..xmas delay?)
I have also etched and drilled the pcb drawn by APberg.
Still collecting parts.
Having a few problems with a 7.5mm spacing for C1 etc in that value.
I can find 'greencaps'.
For a proto..would they be suitable?
Also I noticed on your site, a comment about the coil specs.
I have mainly home wound coils to suit surf p.i. etc
around 400uh.
I see you recommend changing C1 value. above 110uh
Can you advise what parameters for C1 value to suit different coil uh's?
Or maybe in software .
Cheers
John

Hi,
I have multiple mounting holes for C1 in my PCB layout, to mount 10mm, 15mm, or 20 lead spacing.
Of cource you can try using 'greencaps' but make sure that the voltage rating is at least higher than mosfet's. 250V rating maybe. But the stability with greencaps may be not good, there may be drifting as the capacitor warms up, so when testing give it couple of minutes to stabilize.
About the coil inductance, the bigger inductance is not actually problem if coil resistance is higher also. I have not specified the coil resistance values yet. But I guess I must compile a table of coil incductance, resistance and C1 values.
About my recommendation about changing C1 value to larger I changed my mind-- use the same value capacitor as cpecified. I will try to update my website about that also. I have found out that running the circuit at lower frequency decreaces its sensitivity to smaller objects. Frequency depends only on coil inductance and C1 capacitance. So when coil is larger inductance already then to increase C1 shifts frequency down even more, and that is not good.
Only potential problem with higher inductance is that the energy stored in coil during coil charging pulse may go too high, and then resulting flyback voltage may go too high. Anyway nothing bad happens even then, mosfet will not burn, it will only work in the avalance, and dump the exess voltage. You may notice mosfet getting hot then.
So John, if you already have coils, do not be afraid to connect those to the circuit and try out how they work.

Teemo

[Teemo]

Connecting to PC

Hello everybody!

I have made new special firmware for my project. This time it is for connecting the circuit to computer.
Link to the page:http://digiwood.ee/en/metal-detector...ter-connection
I also attach connection schematic and firmware directly to here.PO_metaldetector125.zip

[Teemo]

Hi

No replays, and no feedback to the computer connection topic. I guess it got too messy. Nobody wants to hook up so many wires.

So now I release new version firmware (1.26). This makes the circuit adapting even better to various coils and mosfets. Now it has automatic adjustment of the comparator reference voltage. When connecting power supply the PIC automatically adjusts the voltage treshold level for comparator.

I add new firmware as attachment to here also.
And picture of PCBs on my table:


Best regards.

[Teemo]

Hello everybody.

I got feedback from Andy who has built the project from my website.
He has made the video about testing it.
With his permission I share the link for the video :http://xyolater.bplaced.de/?Videos:Metalldetektor

Best regards,
Teemo

[WM6]

Hi Teemo. Congratulations on this inventive design.

On your web site you say: "There is no discrimination between metals."

But this is basicaly intermitent BFO, and BFOs are able to distinguish between Ferro and NonFerro (by changin oscillator frequency Up or Down). This is very interesting potential of your design in comparison to equal PI uC solutions. Why you would not take this very interesting advantage / potential of your design?

Expecting your next firmware with Ferro NonFerro distinguish capability.

[Teemo]

Hi Teemo. Congratulations on this inventive design.

On your web site you say: "There is no discrimination between metals."

But this is basicaly intermitent BFO, and BFOs are able to distinguish between Ferro and NonFerro (by changin oscillator frequency Up or Down). This is very interesting potential of your design in comparison to equal PI uC solutions. Why you would not take this very interesting advantage / potential of your design?

Expecting your next firmware with Ferro NonFerro distinguish capability.

I am currently working at it, to add this feature. Current plan is to make some kind of dual tone sound, so that Ferro NonFerro will make different sounds. I want it to sound something like old times PC speaker music. The information to distinguish is already there, just need to program new sound system.

Struggling with sound algorithm. I guess I will try to make dual tone sound by switching periodically between audio frequencies. Keep one frequency constant, alter other frequency depending on target.

Any ideas welcome! If anyone knows a good page about how pc speaker sound was generated for old games, please post link here!

[Davor]

You could go for a pulse-counting FM/PM detector which is very resilient to amplitude change, but discrimination will be influenced with coil loading, as in essence it will perform as an off-resonance detector with FM/PM sensing.
Pulse-counting detector? Just count zero crossings over a constant period.

[Xtrem]

sound

https://en.wikipedia.org/wiki/Genera...ment_AY-3-8910

[Rumcajs]

Hi. It is nice project. Not recommended connecting to computer to directly. Better way, if you have using an opto-coupler.
Best regards

Rumcajs

[Rumcajs]

Hi Teemo,

what do you thinh from auto transformer?

http://www.transtutors.com/Uploadfil...ransformer.JPG

The LOAD side (see linked pic.) is FET-side, and V1-side is the tank capacitor side, for example 47nf/1kV or serial 4x220nF/250V (the result is approx 55nF), and paralel an bigger damping resistor.

[Teemo]

Hi. It is nice project. Not recommended connecting to computer to directly. Better way, if you have using an opto-coupler.
Best regards

Rumcajs

Hello!
Yes I know it is generally better to use optocoupler to be safe. So everybody, using direct connection, or any connection to computer only at your own risk!
Anyway I continue to use direct connection myself because of its extreme simplicity, and also it works perfect (as long as circuit is powered by batteries as it normally should be, so no risk of ground loops).

[satdaveuk]

Hello everybody.

I got feedback from Andy who has built the project from my website.
He has made the video about testing it.
With his permission I share the link for the video :http://xyolater.bplaced.de/?Videos:Metalldetektor

Best regards,
Teemo

Hi Teemo
That video you posted here from Andy doesn't do your design any justice at all, your better off without it on here.
It starts off ok but within seconds of it starting he has put music on it while dancing around with targets good as touching the coils , How redickulas can anyone get, there's me trying to listen to the response signals from his different targets and its drowned with music.
Also his build didn't seem to be much good far as range, I get better depth out of my £6.99 stud finder.
If you want good advise I would delete that video simply because anybody who had been considering building your design like myself, after seeing that they may well not bother and move on too something else because it portrays to be nothing special, maybe its not, but if it is you want and need as much interest as possible from the tech guys to help further develop it.
I am not having a go at you personally because I respect people like you that have a go with different designs off there own head and also do realize the time and hard work involved, Its just I don't want your project to fall flat on its *** like so many others have.
Matter of interest what sort of depths are you actually getting to-date on this project? I was quite impressed how Apberge has progressed with the pinpoint coil, looks like a manufactured coil very professional.
Last night made another Barrcuda board for further experiments on that design and was going to also quickly make a board for your design but held back to see what Apbergs Sprint lay files look like because I prefer working from lay files there easy altered for experiments if we feel the need.
Anyway keep up the hard work, you got some good clever guys here to help you along the way, all the best

Regards

[F117]

Hi Teemo,
I really like your design! and I agree with Dave's earlier reply:
It has much potential - especially in the way the change in frequency is an indication on the kind of metal.

To generate tones, you just need to toggle an output pin in the right frequency, as you probably know already.
Have a look at the function 'sound()' here: http://users.telenet.be/willaert/MD/...ckini_16F616.c

Best regards,
- Bernard

[6666]

But I guess I must compile a table of coil inductance, resistance and C1 values.

Anytime soon ?