>> 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.

Hi Jinx,

I'm sure your circuit works as advertised.

But for a 6" distance, the coupling between a hand and a sensor that is
roughly 6"X6" is on the order of a picofarad. And the ability to reliably
resolve a detection distance on the order of 6 inches requires a circuit
that can resolve much smaller than a pF. I think your circuit can achieve
this if the potentiometer is adjusted correctly and the noise is low
enough.  I think your approach or something similar is Cedric's only
option. The other dedicated capacitance sensors except for perhaps ADI
(with which I have no experience) are too noisy. They're designed for
applications other than proximity. FWIW, I work at Synaptics
(www.synaptics.com). And they keep me busy, which explains why I don't
post too much anymore!

Scott

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