Olin Lathrop wrote:
> If I remember right, CdS cells have a peak sensitivity around 600nm light
> wavelength, which is orange. =A0I think I used yellow LEDs since that's w=
hat I
> had. =A0I went thru the junkbox and selected LEDs that showed the best
> response on the CdS cell, which in my case were yellowish (maybe they wer=
e
> amber, it was a long time ago).
>
> The result is of course non-linear. =A0I found it helped to put fixed
> resistors accross each LDR. =A0It depends on how far off you want the vol=
ume
> control to go.

Another option would be using an incandescent lamp as a variable
resistor. It can be 20ma/5V micro lamp:
http://www.fujidengyo.com/incandescent/wtrd24_e.htm

20ma/5V lamp is 250 Ohm at 20ma and I expect it to be less than 20 Ohm
when cold. It should be quite linear at small AC signals, say less
than 100 mV. Feed the lamp with a constant current source regulated by
a microcontroller.

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