Metal Detector is used to sense the presence of metallic materials. This simple metal detector circuit diagram using A 100uH impedance as a sensor. The frequencies oscillation determined by the IC C209A built in oscillator circuit and the coil L1 form as a part of external LC circuit. The mechanism of the metal detector is as the following : If there is a presence of metals, the coil inductance is changed and the resultant change in oscillation is demodulated to create an alarm. The availability of LED is used as a visual indicator. This simple metal detector is able to sense the presence of metals up to a few inches in distance. To adjust the sensitivity, the value of R1 POT need to be adjusted.
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