Set it to a few tenths of a volt with light but no smoke.Okay, thank you for that. So setting it to be 0.2/0.3v with no smoke and no light will be the bias needed. Then just using a pot instead of the fixed resistor in the position specified will allow me to change the bias to get whats needed. Then changing R23 lower it would increase the gain.
I don't have a 1Mohm pot, i will get some ordered tonight. I'm guessing that a 20k would be miles off? Also, are you saying put the phototransistor to 3.3v because then the voltage that flows through is smaller and therefor wont hit the rails so easily? I have it connected to 5v.
I suggested a 10 megohm pot, not a 1 megohm.
You can try a smaller value, I just don't know how high a resistance is needed to get the desired signal.
5V is fine. Somehow I was thinking you had a 3.3V supply.