todbotI made a quick capsense button PCB for the CAP1188 capacitive touch chip . I intentionally followed none of the recommendations for designing capsense buttons. But I did design it so it would easily plug into the Adafruit breakout board which can nicely live on a small solderless breadboard with an Arduino Pro Micro.
To make it a bit more usable, I covered the bare copper with a sheet of kapton tape.
When running the simple test sketch for the chip, I discovered just how bad the board design was. Pretty much any touch would trigger multiple inputs. But after reading the CAP1188 datasheet a bit, I made a small config change of
cap.writeRegister(0x1F, 0x1F); // addr 0x1F set sensitivty to 0x1F (4x, default 32x)
to reduce the sensitivity, it ends up working out pretty well.
I may end up using this board as a tester, but I do really need to redesign it. :-)
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Can you use the same technique as the OS Tricorder project (I know there are loads) to make a rotary capacitive touch input, a la Apple touchwheel? I can see that you are already interested in rotary encoders for device input. Perhaps you can make the body of the lamp part of the controller.
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Hi Simon, Yes I totally could make a wheel. Most capsense controllers support a wheel mode, and even though the CAP1188 chip I use here does not seem to, you can fake it in firmware.
And you guessed my end goal: making part of the lamp body the controller. I've started experimenting with flexible PCBs and my hope is to make a flexible capsense controller that can conform to any crazy shape I end up with.
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I've been using copper foil tape that gardeners use to repel slugs. Cheaper than flexible pcb material when you are just experimenting with the pad forms. It does solder with flux.
I wrote some rotary encoder code for ATMEGA328P and would love to experiment with forms for a capacitive version (flat surfaces are pretty unimaginative). You mentioned the smoothness and inertia of rotary inputs in an earlier log and capacitive sensing would be probably be suitable for this.
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