Touch sensor experimenting

[Simon]

Having considered using a light sensor as a tactile pickup I've got a bit more ambitious and I'm thinking of an actual capacitive touch pad. I have found the following controller chip http://www.farnell.com/datasheets/1714150.pdf?_ga=1.120898063.646536181.1456469885 which hopefully would make life a lot simpler than trying to do all the controls myself. There are no suggestions on the actual footprint of the pad. Does anybody have any clues as to what works best? I'm also wondering how to estimate the capacitance of my pads so that I don't have to have many trials. I suppose I should look out some copper clad board and just do some cut marks to define my pads and see what happens.

[chris_leyson]

Atmels Qtouch sensors are based on the Qprox touch sensor from back in the day. I think I used a 5x10mm touch pad with a Qprox sensor in one design and the sampling cap might have been 10nF, sensitivity can be set by changing the value of the sampling cap.

[ludzinc]

Microchip have some excellent application notes. Sorry - not at desk at the moment so can't provide links.

[Koen]

Atmel buttons, sliders and wheels sensor design guide

[ludzinc]

Atmel buttons, sliders and wheels sensor design guide

That's really good!