Here is the circuit diagram of a magnetic proximity switch that finds a lot of applications in many fields.The circuit is based on a magnetic reed switch(S1) as the proximity sensor. A monostable multivibrator based on NE555 (IC1) and a toggle flip flop based on CD4013 (IC2) does the rest of the circuit.
When a magnet is reached in proximity of S1 it closes to give a negative trigger at pin 2 of IC1.The output of IC1 goes high for a time determines by R2 and C2.This clocks the IC2 wired as a toggle flip flop.The output (pin 1 ) of IC2 goes high and the transistor Q1 is biased to ON.The relay is activated and so do the equipment connected to the relay.The LED D1 glows when IC1 is triggered.
- Switch S1 can be a general purpose magnetic reed switch.
- The equipment to control can be connected using NC,NO and C points of the relay according to the application.
- Use a 12 regulated power supply for powering the circuit.
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