I have built the proximity switch circuit in extreme circuits http://www.extremecircuits.net/2011/06/proximity-switch.html but the circuit doesnt make noise only when the sensor terminal is grounded and when I connect the sensor end to a metal object it makes sound but when I connect the ground to the the metal object it doesn't sound and also when I touch the metal when the ground terminal is connected to it.. It doesn't make a sound.. My question is how to make the metal sensor for this circuit???
