2 Coils and 6 Transistors Metal Detector

[Funfinder]

The following schematic has no further description.
But with its 6 TRs and with audio out it might be already very sensitive
and a nice 'n easy to built low-cost detector - especially for persons
who have no access to special electronic parts.

Hammerhead, perhaps it could be something for you!

[6666]

http://www.easytreasure.co.uk/bfo.htm

[Finderskeepers]

That was my first ever electronics project - built it in 2011. Circuit is simple to make, getting the two coils right I found tricky. From memory I replaced the reference coil with a choke and used a pot to tune in the detector. Now it's in the scrap parts box.

[Funfinder]

http://www.easytreasure.co.uk/bfo.htm

You are the profi, thanks for the link!


OK, there is written on the page:
> The 16 cm coil is just about perfect for coins and rings.

Very good, if Hammerhead builts it to search for rings on the beach of Alexandria he
has now the correct advise but for luck with our modern detectors coils from 25-35cm
are still perfect for coins and rings and they are much faster for larger areas.

Anyway - the good thing is that now we have with the:
2_Coils_and_6_Transistors_Metal_Detector.jpg
an useful schematic because on that "drawing"
at the website not even the transistors are typified.

[ODM]

The transistors can be just about any small signal transistors actually, 2n3904, 2n2222, bc107-9, bc547-9. If what you happen to have are PNP transistors, you can flip the schematic and have a working detector.

But without a shielded coil, a BFO will be pretty lousy to use, particularly in wet grass.