Jinx wrote:
>An A2D pin has a maximum recommended signal source impedance
>of 10k. You don't mention which photocell you're using but if it is more
>than 10k at any time then you'd need to buffer it
>
>Perhaps this way, using a dual op-amp. One 1/2 to produce a DC
>offset voltage and the other 1/2 as a summer amp to add and amplify
>the DC offset and the photocell output. By making the DC offset and
>gain adjustable you can make the photocell's output span between 0
>and 5V at the A2D input


I have not decided which one to use yet, based on the answer to this
question. I looked at some on Digikey's site and since I'll be using it
mainly in the light, the resistance should be around 4kohms to 7kohms. So
that should be ok. I can get one and test first. With that, is that a
simpler way now (without an opamp)? Thank you.

Brian.




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