Capacitive switches..?

Discussion in 'General Electronics Chat' started by axeman22, Sep 5, 2010.

  1. axeman22

    Thread Starter Active Member

    Jun 8, 2009
    53
    0
    Hey Gang,

    what are these switches...
    touch switch.jpg
    ..the pic is the inside of a remote control. I must confess I've never fully understood these - are they capacitive/resistive etc - what's the deal..? if I want to make an external switch to trigger the contacts (ie us a picaxe to turn my laptop on/off) what would you do.? I can find the track and solder into it down the line a little then just short the to contacts together.. but I feel this is not the best course action.

    I have a laptop (weather station) and I want to make a watchdog circuit for it.. because it locks up. Any ideas on the simplest way to connect something up to a USB port and be able to toggle that with software.. I can sense that state with the PICAXE and reboot if needed..

    hmm...
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    They're resistive switches. The parts your're showing are just the static contacts on the PC board and the backs of the rubber buttons that push onto them are coated with a conductive rubber compound.

    If you ever have an intermittent button on a remote control you can clean these (and the backs of the rubber buttons) with a pencil eraser.
     
  3. axeman22

    Thread Starter Active Member

    Jun 8, 2009
    53
    0
    any idea the kind of resistive value to place over them (if doing it hardwired as opposed to pressing the actual pad. I'm thinking 10Meg Ohm or something like that..?

    if you just use a small relay and actually short the wires(contact pads) together would that blow anything/mater...?
     
  4. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    A zero ohm contact closure should work with no problem. Observing polarity, you also could try a transistor driven by the PICAXE to act as a switch.

    Ken
     
  5. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    About any resistance will work down to -0-, it's just a simple matrix circuit.
    Out of curiosty meaure across one of the rubber pad contacts to see what you get.
     
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