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Thread: broader capacitive sensing

  1. #1
    Senior Member
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    broader capacitive sensing

    Hi.

    I really like the cleanness of the current capacitive sensing implementation but I see from the Freescale site that these values are only really meant to sense from 50-500pF. It would be nice to have hardware support for a broader range of values, imo. I don't really want touchsense but rather proximity sense.

    Alternately, if anyone has experience or success with compatible boards could easily do this (I know they're out there), I would be all ears!

    .02
    Cere

  2. #2
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    If you're interested in rolling your own PCB, I've had some success using the SX9510 (http://www.digikey.com/product-detai...TCT-ND/4259560). One of the neat things about this chip is it multiplexes the sense lines with LED signals so it's really easy to add backlighting to the sense buttons. In prox sense mode I can get it to reliably detect from over 2" away.

    If you're looking for something premade there's several boards using the MPR121, which can be configured to gang all sense electrodes into a proximity sensor. Its prox mode doesn't seem to be as sensitive as the SX9510 but admittedly Freescale's documentation of the MPR121 is better.

    https://www.adafruit.com/products/1982
    https://www.sparkfun.com/products/12017
    https://www.sparkfun.com/products/9695

  3. #3
    Senior Member PaulStoffregen's Avatar
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    Have you tried using touchRead() on either Teensy LC or 3.1. I'm pretty sure it can sense more than 500 pF.

  4. #4
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    Thanks for the advice Potatotron. I'll check that out! Hey Paul. What I am looking for is something that is MORE sensitive, not less. So I am looking for something that can read even lower capacitive values below 50pF. I am using touchRead. It doesn't really work as a very sensitive proximity sensor.

    Thanks.

  5. #5
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    I needed something like this, and I made a Theremin: works great.

    Using the circuit of this great post:
    http://interface.khm.de/index.php/la...ensing-device/

    With this great Teensy Library:
    https://www.pjrc.com/teensy/td_libs_FreqCount.html
    Last edited by musinou; 06-18-2015 at 02:26 AM.

  6. #6
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    Neat. Thanks for pointing me to your work!

  7. #7
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    I want to make a midi Theremin, but it is not finished yet. I can point you to my work when I finish it!

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