-- [ From: Peter L. Taylor * EMC.Ver #2.5.02 ] --


> Martin Nilsson wrote:
> >
> > I have an application where I need to sense four touch pads with a PIC.
> > These pads should react to very light touch, or even just proximity,
> > so (mechanical) membrane switches are inadequate.
> >
> > I'm thinking of the following approaches:
> > - Optical: Sensing the proximity of a finger with a photoreflector
> > - Inductive/Capacitive: Presence of a finger changes
inductance/capacitance
> >   in an oscillator, which changes the frequency
> >
> > I would be interested in hearing if anyone has suggestions and
> > experience of this problem. Noise and ESD are factors.
>
> Paul Mathews wrote:
>
> For photoelectrics, noise immunity is best for 'through-beam' mode, where
> finger interrupts a beam rather than reflects it.  Also, you will need to
> consider whether modulation of the beam is necessary if ambient light is
> strong.  Hamamatsu and Sharp offer 4-pin chips that include everything
needed
> for modulated photosensor except LED and bypass capacitor.

O.K. but how do you "Fly-Proof" the buttons?
What I mean is how do you keep a fly or other object from creating an
erroneous button press?

--
Peter L. Taylor
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Email: petert@transera.com
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http://www.transera.com
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TransEra Corp.
345 East 800 South
Orem, Utah 84058
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Voice:  (801)224-6550
Fax:    (801)224-0355
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