Pressure mapping sensor mat

[imsolidstate] built his own pressure sensitive mat. It utilizes two discs of copper clad board with a piece of foam in between for each of 64 sensors. As the foam gets compressed, the capacitance between the two pieces of copper changes, a measurement that is fairly easy to make with an analog to digital converter. The mat is being used to measure how well a horse saddle fits the animal. Data is read in through a serial port and then mapped using Excel. This prototype proves that the concept works but [imsolidstate] mentions that there’s room to improve the sensitivity and that there could be more noise filtering incorporated into the design.

Comments

  1. dan says:

    good to know, but where is the site link?

  2. Munden says:
  3. Ren says:

    Nice! The horses will thank you for it.

    I’m guessing each “load cell” would need to be
    calibrated, each with its own look up table (pressure v. resistance) to compensate for variations between cells.

  4. KWA says:

    very cool practical application of the idea. I love it and can imagine this being useful for a lot of other things.

  5. packrat says:

    This is pretty useless without a clear idea what sort of foam is being used here. “I think the foam is polyurethane open-cell foam but I’m not sure.” is not very informative.

  6. zzz says:

    packrat: experiment with everything you got

  7. mjrippe says:
  8. Frollard says:

    @packrat — its any foam, its not resistive, its capacitve sensing the distance between, not anything special about the foam. Any closed cell foam will do.

  9. vonskippy says:

    Nice concept – not sure the results are any where near accurate – nor will they remain consistent over time using foam as a spacer – nor will they hold calibration (even if you could calibrate them).

  10. Itwork4me says:

    A bit easier than making the horse lay on it’s back to make a mold.

  11. aj says:

    This sounds like a Forrest Mims idea out of this book;

    (excellent book BTW- brilliant pre-uc circuit ideas and brilliant adaption of components to do “interesting” things ;) )

    In that book mims recommends anti-static foam (the stuff DIPS and through hole transistors sometimes ships in).

  12. aj says:

    B*gger, Mims used the anti static foam to make a pressure sensitive resistor whereas this project senses capacitance.

  13. delirium says:

    Who’s up for a game of twister!
    When I saw the picture that’s what came to mind…

  14. tomas says:

    This has very important medical applications too! a device such as this, used in orthopedic applications, goes for nearly $10k !

    see here – http://www.apostherapy.co.uk/

    these guys use a similar device to analyze your posture and adjust special shoes accordingly. it works well, but costs a fortune.
    about time this was open source :(

  15. Darkheart says:

    I use a mat like this to trigger a vibrating coffen I built for halloween.

  16. m8rix187 says:

    I have been looking for something like this for a couple of years now. Thanks for publishing this project.

  17. Ben says:

    I wonder if you could use magnets in guide tubes to get a more predictable capacitance curve. Might make the mat too thick though.

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