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Capacitive Touch Testing! – WΛLLTΞCH

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Before I order pcbs for v5.0 and begin assembly (!) I wanted to test the capacitive touch sensing circuit to verify the resistor value needed and to plain see if it would work at all. I wizzed down to Radioshack and grabbed some 1Mohm resistors and a roll of solder (very good by the way) and started prototyping. I cut out a tinfoil circle the same size as the pad, and covered it with a few layers of tape to secure it to the table and act like soldermask over copper. I wired that up to the A0 pin of my trusty UNO, and then wired the sense pin through x resistors to 3.3v to simulate the lipo battery’s output. Using Arduino and Processing, I made a nice graph of the data, and it worked! I found that 3Mohms of resistance worked the best so that’s what I’m going with. Time to get pcbs made! \o/

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Trusty Solder! This cleans VERY well, runs easily, doesn’t smoke, and makes really great joints, all for $5.99!

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The setup: Three Megohm resistors in series to 3.3v and the pad to A0.

Screen Shot 2014-03-01 at 3.20.45 PM

Little taps

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Short hold and little taps

Screen Shot 2014-03-01 at 3.20.32 PM

Short touches

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Longer holds

Bhm3QZOCUAAQdE-To clarify, the touch sensor is the copper behind the walltech logo silskreen in the center. Also: concept pic!

As you can see with the graph, there’s a fairly constant baseline, of which I will take an average maximum of in the final project. When touched, the button exceeds this average rather alot, and can be captured to trigger the time animation of the watch. I’ll test the light sensor next and make sure that works! Hope you enjoyed this little update, I love posing about my projects! 🙂

 

Capacitive Touch Testing!