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I'm looking for a way to make a surface touch sensitive. The sensors have to interface with a keyboard encoder to send signals to the computer as keypresses. This is just the way it has to operate. I have capacitive proximity sensors, but I'm thinking they will not be capable of extending their field to an entire (and irregularly shaped) surface. Is there some kind of capacitive switch that can be used with a foil-like material or fabric-like material that could be glued to the inside of an object, thus making the outside touch sensitive?

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do you just need to know a binary output of whether or not any point on the surface is being touched, or do you need to locate the touch? – vicatcu Jan 31 '12 at 22:32
The former, binary output. – JonathonG Jan 31 '12 at 22:38

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Usually you would etch the capacitive switches onto a PCB, but with an irregular surface some aluminium foil glued to the back of the surface (with wire from foil to capacitive sensing circuit) should work fine.
The larger the area and the thinner the insulating surface material the better.

A uC like the PIC16F1828 would be good for this application, they have a capacitive sensing peripheral with something like 8 (maybe more) channels.

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So essentially scrap the idea of buying a sensor and just make the sensor out of foil? – JonathonG Jan 31 '12 at 22:33
Yes, foil or some thin metal cut/shaped as desired. If you need to detect multiple areas obviously you will need to space them as required. The technology is very simple, though fine tuning and getting it to work reliably can sometimes be a bit of a pain. You may want to read a few app notes before you make your decision - Microchip have a few. – Oli Glaser Jan 31 '12 at 22:39

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