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Electronic circuits that use the 555 Timer

555 Timer Circuits

555 Timers are fun and a great way to start learning electronics

TOUCH SWITCH and TOUCH ON-OFF Circuit


The Touch Switch circuit will detect stray voltages produced by mains voltages and electrostatic build-up in a room. In the first circuit, pin 2 must see a LOW for the circuit to activate.  If sufficient static voltage is detected by the plate, the chip will change state. If not, you will need to touch the plate and the 0v rail. In the second circuit, two touch plates are provided and the resistance of your finger changes the voltage on pin 2 or 6 to toggle the 555.



The circuit can be made 100 times more sensitive by adding a transistor to the front-end as shown in the diagram below:



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