> > But i'm using cheap frat beer
> > (Old German, Boh Ice) and it's the color of piss...totally translucent.
>
>Since beer appears yellow or brownish, it must absorb more blue than red
>light.  The light detection scheme would probably work better with a
>shorter wavelength than what a red LED provides.  Try a green LED, or
>maybe even a blue LED if you can get hold of one.  However, I sortof
>remember (perhap incorrectly) that CdS photoresitor sensitivity falls off
>over the visible spectrum from red to blue.  But, these things are quite
>sensitive to start with, so using a shorter wavelength is probably still a
>win.  You will have to expriment here.

Too right about the spectrum sensitivity, but a glance at my handy
sensitivity chart suggests that the CdS is still more sensitive in blue than
the human eye.

Just a suggestion, but you could use a PIC12F675 (I think that's it- 8 pin
w/ADC) to watch the resistor voltage (Olin's bridge circuit suggestion
should be here), then turn on the LED.  I know on the surface it *seems*
more complicated and expensive, but the PIC costs <$2 from Digi-Key,
and that would be basicallly the only component needed besides the
LED's, the photocell and whatever bits and bobs you use for the bridge
circuit.

Mike H.

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