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Designing a touch sensor using 555 timer IC

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thecritic

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I am trying to design a touch sensor using 555 timer IC.
What I did was--
I used the 555 IC in its popular Monostable mode, and I attached a small copper touch plate to its trigger pin 2.
What happened is that my device worked fine at first. (It would be triggered by finger and also by any metal objects.). So I set the power on for overnight to record if it would make any false trigger. But when I returned on the morning, the curcuit was already rendered insensitive. It wouldn't be triggered by hand. It would be only triggered if I supplied ground to pin 2.

So, what I want to know is that, is it that my IC was damaged or that the circuit I used was unrelaiable.
 

Boncuk

New Member
tie a 10 to 100kΩ betwen trigger input (pin2) and VDD. Add a small cap 10 to 100nF parallel with the resistor.

Boncuk
 
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