// Arduino based metal detector// (C)Dzl july 2013// http://dzlsevilgeniuslair.blogspot.dk/// Connect search coil oscillator (20-200kHz) to pin 5// Connect piezo between pin 13 and GND// Connect NULL button between pin 12 anf GND// REMEMBER TO PRESS NULL BUTTON AFTER POWER UP!!#define SET(x,y) (x |=(1