Tuesday, March 1, 2016

Simplest Metal Detector

I was reminded this week how I was challenged to design one of my best known metal detectors. Rachel and Steve Hageman of Hewlett-Packard had designed a self-contained metal detector which (when built) would have just twenty-six PCB-mounted components. This was radically simple. Intuitively, I thought that I could beat that. I simplified, and I simplified, and I reduced a self-contained metal detector to one single PCB-mounted component (see the image). And its performance was better than twice that of the Hageman design. My design was published in Australia and in the UK. It was called the Poor Man's Metal Locator.


Anonymous said...

good afternoon. Mr.
what would be the E1 B1 and e2 b2 that go to the coil ?

LA 3220 can be used in BFO ( 2008 ) ?
grateful for the attention.

Thomas O. Scarborough said...

Thank you Anon. e = the end of the wire, and b = the beginning of the wire. In other words, it matters which way up each coil is. I would suggest that you simply try the LA3220 and see. This circuit is beyond all simulations and calculations. Incidentally I think that my 7556 metal detector on this blog is the best embodiment of this idea: https://thomasscarborough.blogspot.co.za/2013/06/bb-metal-detector.html