Hi
I needed a probe for metal detecting and, struggling to find anything, decided to design my own.
It's just a simple colpitt's oscillator strapped to a PIC08M. As the oscillator coil comes close to metal, the frequency varies. At boot (power switch is a simple push to make button, you don't need to remember to switch off
), the picaxe measures the oscillator frequency (40KHz) then stores the value. It then constantly monitors the frequency and if it varies by any more than a threshold value, it sounds the beeper - that's essentially it.
Sensitivity is about 20 to 25mm on a UK penny (about the size of a US cent).
Ferrite rod is about 10mm x 70mm, wire is 0.5mm EC.
Anyone specifically interested in building metal detectors can view the original post along with some pix in the geotech forums ...
http://www.geotech1.com/forums/showthread.php?t=19194
Cheers
Neil
I needed a probe for metal detecting and, struggling to find anything, decided to design my own.
It's just a simple colpitt's oscillator strapped to a PIC08M. As the oscillator coil comes close to metal, the frequency varies. At boot (power switch is a simple push to make button, you don't need to remember to switch off
), the picaxe measures the oscillator frequency (40KHz) then stores the value. It then constantly monitors the frequency and if it varies by any more than a threshold value, it sounds the beeper - that's essentially it.Sensitivity is about 20 to 25mm on a UK penny (about the size of a US cent).
Ferrite rod is about 10mm x 70mm, wire is 0.5mm EC.
Anyone specifically interested in building metal detectors can view the original post along with some pix in the geotech forums ...
http://www.geotech1.com/forums/showthread.php?t=19194
Cheers
Neil