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How to make a touch sensor replicate an on/off switch - HELP!

Discussion in 'Sensors and Actuators' started by wrongsideof40, Dec 29, 2017.

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  1. wrongsideof40

    wrongsideof40

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    Dec 29, 2017
    Hi folks - I have a touch-sensitive switch, intended for use with Arduino, like this...

    https://www.ebay.co.uk/itm/TTP223B-...742124&hash=item2a5c1681ab:g:faQAAOSwLzdWSXos

    It has a three-pin connector: VCC, OUT and GND. Touching the switch momentarily switches the output from low to high. What I actually want to achieve is the effect of having an on/off switch which is normally open circuit, then closed circuit (or 0V), when closed. The power drawn by the load will be negligable (1mA approx) so no need for relay, etc.

    Can anyone please suggest the simplest, solid-state way of achieving this. I'd like to continue to use the PCB, as the touch interface is just right for my needs.

    Any help very much appreciated.

    Thanks
     
  2. kellys_eye

    kellys_eye

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    1,146
    Jun 25, 2010
    Feed the output signal to the base of an NPN transistor via a 1k resistor.
    Connect the emitter of the transistor to 0V and put the load in the collector circuit (one side of the load connected to the collector, the other side to the supply).
     
  3. Minder

    Minder

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    623
    Apr 24, 2015
    Or the later alternative, a Fet, the 2N7000.
    M.
     
  4. wrongsideof40

    wrongsideof40

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    Dec 29, 2017
    Thanks folks BUT- I tried kellys_eye suggestion, and this worked, with respect to allowing power to flow to a load (gracious thanks!).

    Perhaps I poorly explained what I want to do: I want an output that will ground when the touch switch is activated, and to be open circuit, when not. The appliance I am signalling to will activate when its input is grounded, if that makes sense.

    I probably need to reconfigure that transistor (or FET) but I don't know how.

    Thanks again
     
  5. Minder

    Minder

    2,948
    623
    Apr 24, 2015
    Here is the original PDF on it, ignore the 55¢ !
    M.
     

    Attached Files:

  6. Arouse1973

    Arouse1973 Adam

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    1,080
    Dec 18, 2013
    Please clarify. Press the switch once and the circuit activates, press it again and it de-activates. Or press and hold the switch and the circuit activate and release the switch and the circuit de-activates?
    Thanks
    Adam
     
  7. wrongsideof40

    wrongsideof40

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    Dec 29, 2017
    Hi. The latter: activate for as long as switch is touched (which is what it does already, although this can be reconfigured). But rather than switch the supply to the load, I want to ground the output, when activated...
     
  8. Arouse1973

    Arouse1973 Adam

    5,164
    1,080
    Dec 18, 2013
    So if it does it already what do you need to do?
    Thanks
    Adam
     
  9. wrongsideof40

    wrongsideof40

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    2
    Dec 29, 2017
    Me again - I just tried Minder's 2N7000 suggestion and this fits the bill perfectly! Thanks so much for all your help.
     
    Minder and Arouse1973 like this.
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