Just look at microchip's m-touch

Andre


On 2/17/08 3:39 PM, "Jinx" <joecolquitt@clear.net.nz> wrote:

>> It's possible to detect a hand or any other conductive object
>> at a distance of 6" by using capacitive sensing
> 
> Scott, the attached circuit will do just that. Sensitivity is mostly
> dependant on the size of the metal plate. I've embedded these
> behind walls as secret switches, using 100mm x 100mm of
> adhesive aluminium foil as the sensor. A sensor that size will
> react to a hand (parallel is best at that distance) through 100mm
> of averagely-dry wood. Although I've described it as "touch" it's
> actually a proximity detector. I often have a discrete Schmitt
> trigger, with or without settable hysteresis points, after the op
> amp to get logic levels but an analogue interface could be used


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