This is one of my best super-simple metal detector designs, which a publisher generously donated to the public. Before this design came along, induction balance (IB) metal detectors typically used 50-100 components. The simplicity was achieved through several tricks -- but in summary, I stripped out the usual analogue electronics. Copyright restrictions prevent me from publishing the design on my blog, but it may be downloaded free here: Matchless Metal Locator. OBSERVATION: What I can offer on my blog is nearly ten years of hindsight. I would now improve the design, most importantly, by increasing the battery voltage to 12V or 15V, and using a 9V regulator. This would greatly assist stability. The biasing around IC1 pins 8 and 12 could be simplified by combining VR1 and VR2 in one 500k component. And if I had the chance, I would like to apply a wobbulator to the IC1b input circuitry. This has been a popular design. It went into production in Australia, in two versions.