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555 touch switch

Discussion in 'General Electronics Discussion' started by atollp, Feb 21, 2012.

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  1. atollp

    atollp

    33
    0
    Feb 11, 2012
    Hey forum,

    Slight problem with this touch switch I built. Once triggered, the circuit description says that in order to reset, pin 4 needs a low logic level. The circuit works great, but once I touch the sensor plate (pin 2) it won't turn off unless I disconnect the battery, and even then when I reconnect it the LED comes back on without touch activation. If anyone could tell me how to reset this damn thing, it would be greatly appreciated.

    Thanks much, G

    (first circuit on page...the 'manual' one)

    http://electronicidea.blogspot.com/2008/09/touch-switch.html
     
  2. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    out of curiosity, if you removed the touch plate and replaced it with a momentary push button(or anything that will hold the button low, then high to be triggered). Does the circuit work as expected?

    is it possible that you are shorting out the metal touch plate causing pin 2 to remain high? Make sure that there is zero electrical connection between the plate and anything around it.
     
  3. atollp

    atollp

    33
    0
    Feb 11, 2012
    Just figured it out....just had to touch pin four to negative side of battery. I thought I was doing that before, but oh well, it works now. Thanks for the reply though!
     
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