Metal detector is very common devices for checking the person in shopping
malls, hotels, cinema halls to ensure that person is not carrying any explosive
metals or illegal things like guns, bombs etc. metal detectors can be created
easily and the circuit is not that complex.
The LC circuit is nothing but inductor and capacitor which is
connecter in parallel. The LC circuit will trigger the proximity sensor if it
detects any metal near to it. Proximity sensor will give glow the led, and also
make the buzz with the help of the buzzer.