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Glass conductive switch

Discussion in 'General Electronics Discussion' started by bobbyyap, Feb 7, 2010.

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  1. bobbyyap


    Feb 7, 2010
    I working on a project, which need to make the glass surface act as a on/off switch.
    I've seen this of table lamp before which you touch on it's acrylic body and the light on or off.
    What sort of RF switch is this and what's the name?

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    there are a couple of ways, but the majority either detect noise being picked up by your body being coupled to an amplifier, or you body's capacitance affecting an oscillator.

    Google for "capacitive touch switch circuit"

    If the glass surface you want to make touch sensitive is the one through which the light shines, you will need (probably) a way to make the inside conductive without being opaque.
  3. Mitchekj


    Jan 24, 2010
    As an example for the oscillator type:

    An LC tank oscillator circuit. I had actually built this some time ago. It works just as advertised with some modifications. I had to add a pull-up on the base of Q4, and take R1's value way down to get the thing to work. (300k is what I think I ended up using for R1.) It still hangs on our door to this day, nifty little thing.

    You can modify that to switch a lamp easily enough. Touching the metal frame, of course.
    How would that work with glass? If I'm understanding your comment, Steve, a small conductive layer?
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Yeah, for glass, all I could imagine is either a conductive inner surface (forming one plate of the capacitor) and your body on the other side of the glass forming the other plate.

    Alternatively, if the outside is conductive it could would act just like a metal plate.

    I'm not sure how feasible those options are though.
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