Pre-Confirmation to our Project (Metal Detector)

Metal Detector

·  The circuit described here is that of a metal detector.                · The circuit utilises two RF oscillators.The frequencies of both oscillators are fixed at 5.5  MHz.              ·  For proper operation of the circuit it is critical that frequencies of both the          oscillators are the same so as to obtain zero beat in the absence of any metal in the near vicinity of the circuit.       ·The alignment of oscillator 2 (to match oscillator 1 frequency) can be done with the help of trimmer capacitor VC1.         ·When the two frequencies are equal, the beat frequency is zero, i.e. beat   frequency=Fx-Fy=0, and thus there is no sound from the loudspeaker.       · When search coil L1 passes over metal, the metal changes its inductance, thereby     changing the second oscillator’s frequency.        · So now Fx-Fy is not zero and the loudspeaker sounds.        · Thus one is able to detect presence of metal