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Thread: Touch library and static electricity

  1. #1
    Junior Member
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    Touch library and static electricity

    Hi,

    I'm using the touch library to create a set of input signals to control a light sculpture. The metal inputs are large 1/8" steel plates. The setup works very well and can get some good response to how much of the metal input is being touched. The devices are going to be deployed in a very dry environment and I'm worried about static discharge. In order to get to the devices you have to climb up a ladder and I'm planning on having a grounding plate be one of the rungs which will help to ground participants.

    Does anyone have advice on if I should be protecting the teensy inputs to protect against that kind of shock directly?

    Thanks,
    mauricio

  2. #2
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by mbustosorg View Post
    Does anyone have advice on if I should be protecting the teensy inputs to protect against that kind of shock directly?
    There are at least 3 things you can do.

    #1 - Add a series resistor between the electrode and Teensy pin. Even 1K will dramatically help.

    #2 - Add a 3.9V to 4.7V zener diode between the Teensy pin and ground. The cathode connects to the pin. This adds a small, fixed capacitance.

    #3 - Cover the electrode with thin but reliable insulating material. This greatly reduces the sensitivity.

  3. #3
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    Thanks Paul,

    That makes a lot of sense. Does anyone have experience with using any of the off the shelf TOV chips to help with this? I going to use the above techniques but would be interested to hear any other opinions on TOV.

    Thanks,
    mauricio

  4. #4
    Senior Member Jp3141's Avatar
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    The Zener is the best solution. The TOV is bidirectional - so it won't protect the teensy from negative static spikes.

    If you are In an environment where you can sometimes see the static sparks, then 2 zeners & resistors might be better - input R from the pad to zener1, then another R to zener2 & the teensy pin. Be careful to ground the zeners close to the Teensy's ground pin. Even so, a static zap might cause the Teensy to latch up or reset. Is that OK ?

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