DIY capacitive touchpad

Technology
DIY capacitive touchpad


capacitivekeypad2_cc.jpg
From the MAKE Flickr pool

Flickr member svofski made this rather sweet touch-sensitive keypad with backlighting –

This a custom implementation of capacitive sensing technlogy as per QMatrix Whitepaper. It uses an ATmega8 to scan the keys and outputs ASCII characters to the serial port.

Schematic, PCB, and source code are available, though the project page is currently Russian-only. Check out the Googlish interpretation for details.

Update: As the pointed out in the comments, Google’s Russian is a little rusty. For further explanation, best to check out the tech whitepaper.

8 thoughts on “DIY capacitive touchpad

  1. svofski says:

    “Thus, a pipsqueak of crumbs on Ctank charge will gradually accumulate” :)

    It’s best to just refer to QMatrix Whitepaper, which gives a very good explanation of what’s going on:
    http://www.atmel.com/dyn/resources/prod_documents/qmatrix_white_paper_100.pdf

  2. Collin Cunningham says:

    ha – good point!

  3. jeff-o says:

    I’ve managed to build a “keypad” with two buttons (see below for link), but this looks like a logical progression for my next project… or something like it! Hmmm, how can I put 12, 16, or more capacitive sensor keys to work? Oh, the possibilities!

    http://www.instructables.com/id/Illuminated_Touchscreen_Poster_Frame_with_Sublimin/

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