Who is the most simple PI detector circuit?

Thank you for this russian pirate pi PCB, do you know anythink about his function characteristics, or about coil detail?


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http://www.thunting.com/smf/index.php/topic,21224.msg275998.html#msg275998

I did one similar from over at geotech.. I made quite a few changes with things and it works great. It just needs to have adjustment, if it
is set with the values used in the original pirate it doesn't work, at least not for a hill of beans... you can see it in this vid, I'm no videographer
so it isn't the best but you can see it works well for what it is. I redrew the schematic with my changes and parts placement, have also made
some major changes to it using dual 555's and have 3 different units all working good. a fun little project if you want to play around and experiment
with it. Its cheap too..

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http://www.thunting.com/smf/index.php/topic,21224.msg279910.html#msg279910

The redraw or whatever you want to call it and the revised pcb image is posted in the open simple pi group at

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.

I did some major changes throughout but ended up back to the simple version just using the 5 trimmer in R1, different op amp and a 1.2k 1watt damping resistor with a 1k series resistor because I use a fast spider coil with it.

The gain is pretty high so basically making a good coil and adjusting the values to your coil works well for it. I have a 4 dip switch added with 4 resistors at R7 on my last experiment so I can change to 16 different values, it will let it work with numerous different coils that way as long as you make the adjustments at R1, it was quite the learning experience using this little pi as the platform. I know so much more about how it works now after working with it one part at a time and making changes and seeing what it did or didn't do.

I think bernte's pcb (the one posted in here) works just as well, it just needs some value changes at R1, R4, R7 and use a better op amp.

George (geotech) said the 555 oscillator is wired a little different than normal but works, that is why maybe your confused with the layout or wiring of R1. I have a newer version using dual 555's so the timing can be adjusted on both sides with on/off times, still on the bench though, I just haven't had time to play with it since I'm working on a new different custom design pi. Hope to have it half way wired up today.

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http://www.thunting.com/smf/index.php/topic,21224.msg279959.html#msg279959

Geocash1

Interested in the spider coil you made thats on the bench in your video
any chance of a couple of close up pics please ?

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http://www.thunting.com/smf/index.php/topic,21224.msg280088.html#msg280088

What I'm after is a dual audio PI detector schematic, I just can't seem to be able to find one. I've been working on my own design but I'm in a bit of a hurry. 

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http://www.thunting.com/smf/index.php/topic,21224.msg280151.html#msg280151

Xavier