Simplest PI detector possible?

[brucester]

Hello,

I am after a schematic that a beginner could build using a few basic parts.

Can anyone recommend a well documented project suitable for my purposes? I dont care how it performs, as long as a get a beep when i put a bit of metal near the coil would satisfy me at this stage.

Thanks

[sido]

Are you serious mate. Have you not read the multi posts on the basic Surf Pi. The most simplest and reproduced common basic Pi.

It is quite well documented here.

[brucester]

serious :P

cheers cob

[Finderskeepers]

Sido is right. A surf or even a baracuda are simple p.i. detectors for a newbie to build as opposed to making a Minelab SD2000 which is like walking through a minefield. The surf pi and baracuda are very simple to operate and are similar with depth and sensitivity. Performance of the machine will also depend on how good you build the coil.

[dfbowers]

I have a drawer full of "simplest PI s " possible. If you are going that far to make something that works, why not go just a bit further and make something that works really well. If you want to learn exactly how they work, go with the HH1 as Carl has perfect documentation and can be made to work very well. Personally I would go with the Baracuda as my build was slight better than the Surf PI.

[brucester]

Thanks DF.

I do want to make the best metal detectorr possible eventually. But still in the learning phase and figured building a simple one up front would be good for the learning experience. Over the next decade i will probably build many. Just need an easy one to get me started

[6666]

Hey its Xmas, actually this could be a fun project, all analogue
you can make the worlds simplest from a couple of ATtiny chips, but thats not fun.

[Eddy71]

From Russia, with love

[Eddy71]

Hire more:

http://forum.cxem.net/index.php?showtopic=111009

[brucester]

From Australia, with thanks

[6666]

Thanks Eddy

there is some xmas fun for you brucester
have fun

[6666]

I have had a bit of a look around Eddy's forum,
the google translation is a bit hard to follow
but it seems that some good work has been done on this simple circuit,
and some alterations to the basic circuit gives reasonable results,30cm on the penny!
The op amp seems to be a K157UD2, which I cannot identify, but there is some talk about using aTL072.
The coil is something like, 190mm dia, 25T, .5mm wire.

A bit more reading is required.

[6666]

A couple of schematics from forum.

[6666]

These seem to be the latest schematics.
TAKE NOTE if you use some other op amp than a K157UD2
then disregard the pin numbers and make connections to the correct + and - inputs.

[6666]

From Eddy's forum I was lead to another which had a project very similar, the translation seemed to call it
the Pirate MD.

9-12 volts
Current consumption - 30-40 mA
Sensitivity - 25 millimeter coin - 20 cm

The coil is wound on a mandrel 190mm and contains 25 turns of PEV 0.5mm.
Can anybody please tell us what a K157UD2 is ? thanks