Dave,
Nope, they can generate voltage from light too. I didn't believe it either
when I first heard it.. about 40mv last time I checked with a voltmeter (use
one with about 1MOhm/Volt or better). Not a lot, but fairly easy to amplify
with an op-amp or comparator if memory serves. I think they are pretty
selective about light range too (i.e. only respond to the color they emit).
I suggested them because at first I was thinknig "solar cell" when you were
writing "photo cell". However, their electricity-generation properties can
be useful at times, and I'm pretty sure they have a very fast response to
light.
later,
patbob ([EMAIL PROTECTED] [EMAIL PROTECTED])
> > If it hasn't already been suggested, you might try
> using an LED. They
> > generate a small voltage when light hits them, and I'd bet
> they have a way
> > faster response to light than the photocell.
> I was under the impression that an LED generates light, not
> senses it :) You
> may be referring to a photodiode (or phototransistor)?
>
> The photocell I was using has a pretty quick response time
> (it's basically a
> really tiny silicon solar cell) and proved adequate for the
> purposes of my test.
> I wasn't really wanting to put too much effort into it :)
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