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555 touching timing switch circuit diagram

2015-02-02 16:39  
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555 touching timing switch circuit diagram
The integrated circuit IC1 is a piece of 555 timing circuit, connected to monostable circuit here. Usually as there's no induced voltage in the port of touching slab P, after the capacitance C1 passes 555 NO.7 pin to discharge, the outputof NO.3 pin is in low level, relay KS continue to release, the lamp won't be lighted. While needing to turn on a lamp, to touch sheet metal P by hand, the human body's flooding wave signal voltage is applied into 555 triggering ports by C2, and makes 555 output change from low level to high level, the relay KS pulls in, the lamp will be turned on. At the same time, the interior of 555 NO. 7 pin stops working, the power supply then charges for C1 by R1, this is the periodic begin.When the voltage of C1 goes uo to 2/3 of power supply, 555 NO. 7 pin make C1 diacharge until NO. 3 pin is in low level again from high level, the relay releases, the lamp is turned off, this is the periodic over.