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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