This simple metal detector circuit diagram is used to sense the presence of metal. A 100uH is used as a sensor. IC C209A has a build in oscillator circuit and the coil L1 form a part of its external LC circuit which determines the frequencies oscillation. When there is a presence of metals, the inductance of the coil is change and the resultant change in oscillation is demodulated to create an alarm. The LED also gives as a visual indicator. This circuit can sense metals up to a distance of few inches. Adjust the value of R1 POT to adjust the sensitivity.
