Single chip metal detector circuit By john www.250.org.ua Description. This is a simple single chip metal detector circuit based on IC CS209A from the Cherry Semicon- ductors. A 100uH coil is used to sense the presence of metal. The IC CS209A has a built in oscillator circuit and the coil L1 forms a part of its external LC circuit which determines the frequency of oscillation. The inductance of the coil change in the presence of metals and the resultant change in oscillation is demodulated to create an alarm. The LED gives a visual indication too. This circuit can sense metals up to a distance of few inches. Circuit diagram with Parts list. Notes. ·ð Assemble the circuit on a general purpose PCB. ·ð The switch S1 can be a slide type ON/OFF switch. ·ð The IC must be mounted on a holder. ·ð The POT R1 can be used to adjust the sensitivity of the circuit.