We found this circuit in an English publication from 1980. It provides a logical output signal when the sensor is touched. The signal can be used to trigger a power step or relay. The circuit operates as an oscillator that is muted when it touches or approaches the sensor. The supply can be done with voltages from 5 to 12 V. Never use a source without a transformer to supply this circuit. The transistors can be the BC548. The coil consists of approximately 200 turns of wire 32 in a ferrite rod. With the 4027 the action of the circuit becomes bistable.
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