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Thread: push buttons with 100 ohm resistance and teensy

  1. #1

    push buttons with 100 ohm resistance and teensy

    hello
    i got package with new small tactical silicon push buttons for my project and i figure out that they dont give 0 resistance when i push the button under measurement.
    its give me 100 ohm.
    (my project include 31 buttons that connected to 2X Mux16 wired to teensy).
    right now my project run with another small clickable tactical buttons and its working great.
    i just wanna know if teensy should to deal ok with this 100 ohm value instead the the (about) 0 ohm buttons i got now?
    tnx
    rota
    Last edited by rotabox; 03-19-2019 at 12:54 PM.

  2. #2
    Senior Member PaulStoffregen's Avatar
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    That's very unusual for pushbuttons to have such a high on resistance. Are you sure they are reliable?

    Whether you will get a reliable signal depends on the ratio of the resistance with whatever is doing the pullup when the button isn't pressed. If the pullup is quite weak, you should get a reliable logic low when the button is pressed.

    With mux chips, the wait time for settling of the signal, before you can read it will also depend on the resistor. The higher the resistor (better for logic levels) the longer you must wait for the signal to settle.

  3. #3
    Quote Originally Posted by PaulStoffregen View Post
    That's very unusual for pushbuttons to have such a high on resistance. Are you sure they are reliable?

    Whether you will get a reliable signal depends on the ratio of the resistance with whatever is doing the pullup when the button isn't pressed. If the pullup is quite weak, you should get a reliable logic low when the button is pressed.

    With mux chips, the wait time for settling of the signal, before you can read it will also depend on the resistor. The higher the resistor (better for logic levels) the longer you must wait for the signal to settle.
    Tnx for your replay Paul
    That's the button I ordered
    I noticed the more I press Herder more the resistance decrease but not more then 80 ohms
    I think I just gonna try replace 1 button to see what happened. I just wanna know I'm not harm the teensy or the mux.
    Click image for larger version. 

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  4. #4
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    The resistance will not make any particular difference to the Teensy and in fact will probably work 'fine' assuming the buttons themselves are reliable. Problems would start to happen if your pullup resistance is close to or smaller than the button resistance but the Teensy internal pullup is in the 10k range.

    Having the pins at something other than a clean one or zero can become a problem if you are making a battery powered design or are dealing with high power switching devices but for what you are doing how well the button feel and function meets your needs in terms of user experince (do the feel right, match the rest of your design, mount neatly etc) matters more than the electrical properties.

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