◀ maker

Build your own metal detector with an Arduino

“Most metal detectors use a search coil that act as part of an oscillator circuit. When metal is put in proximity of the search coil both the frequency of the oscillation changes. Many metal detectors uses another more stable oscillator BFO (beat frequency oscillator) to act as a reference for the frequency of the search coil,” Dzl wrote in a blog post.“Usually the frequency of the BFO is adjusted to exactly match that of the search coil oscillator when no metal is present near this. The signals from these two oscillators are then fed to a (usually analog) circuit that creates an output proportionally to the difference in frequency of the two. This may be either an audible tone and/or some meter reading.”However, says Dzl, another device that is quite handy at detecting minute frequency changes is a versatile microcontroller (MCU).“[So] we decided to swap the BFO approach for a microcontroller and came up with [a] simple circuit. The oscillator circuit feeds a 160kHz signal to pin 5 of the Arduino. The Arduino sketch then measures the frequency of this pin very accurately,” Dzl explained.“When the ‘NULL SW’ button is held this frequency is stored. Any deviation from this frequency is then represented as a series of ‘geiger counter’ clicks on the piezo. The rate of the clicks increases as metal approaches the coil.”

Go To Source
comments powered by Disqus
26 Jul
Planet Arduino @planetarduino
RT @Atmel: Look for some loose coins or jewelry with this #DIY Arduino-powered metal detector: http://t.co/8LL4awTs6p #Atmel #Arduino #Make…
26 Jul
rich nass @rnass
RT @Sander1Arts: Build your own metal detector with an Arduino http://t.co/A4O9Z0BMMr via @wordpressdotcom