Sunday, October 05, 2014

Capacitive Touch Sensors, revisited

Last year, I wrote about my plan to use capacitive touch sensors in my house as "wall switches" rather than what you'd find in any sane person's house.

I got my first batch of sensor pad boards a year ago, but never got around to actually writing a post about them. The rather poor picture to the right shows the pads and the ground-hatch on the back. You can even make out an Apache Subversion revision tag on the silk screen :-)

It has a few problems, however: sizing is incorrect for our 1-gang electrical boxes, it is missing drill/mounting holes, and there are no cutouts so the backlighting can shine through. Whoops! When the new board is designed and back from production, then I'll get some good pictures posted.

So why post now? It's been a year!! ... well, I finally got around to pairing this sucker up with SparkFun's MPR121 breakout board. Connected that to a Raspberry Pi, and started Real Testing. I may have to tweak the pads and traces a bit for Rev2, but it is doing very well for the first iteration.

The largest obstacle to getting this functioning with the MPR121 was failure to use its "Auto Config" feature. Once I let the chip figure out what the hell it is connected to... it worked like a dream.

(see next post, re: problems talking to an MPR121 from a Raspberry Pi)

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