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Close to The Switch Circuit Diagram

2015-09-07 17:59  
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The proximity switch can be used for anti-theft alarm, automatic messenger, automatic protection. It is stable and less susceptible to interference caused by the malfunction, the circuit shown in the figure.

Close to The Switch Circuit Diagram

How it works:capacitors C1 ~ C4 bridge detection circuit, and plugged into the 220V AC mains, due to the capacitance value of the four bridge arms are equal. A, B, two points on the ground potential to maintain a balance, the VD1 ~ the VD4 composed of a diode bridge rectifier, there is no signal output. When the body close to the A or B of the sheet metal, body capacitance Cx formed between them parallel to the capacitive bridge arm, loss of balance, rectifier AC input, the output of a DC signal. This signal base current injected into the  transistor  VT1, VT2 is the VT3 amplified to drive the relay K action. The control circuit of the relay contacts control, to achieve the purpose of the proximity switch.