/diy/ - Do It Yourself

>>1660307
So you flash red, then green, then blue, and measure the amplitude of each reflection with the photodiode? You could arguably skip all that and use a second RGB LED as the receiving photodiode and just shine a white light on the conveyor constantly. Might need some tuning as I think the red LED would pick up green and blue light also, but that's easy enough to do.
Arguably, pulsing the LED with AC might be better in order to get an absolute amplitude, since you could filter out the DC component which would contain noise due to ambient lighting.

Now a simple non-inverting amplifier circuit would work fine. Since op-amps work better closer to the negative rail than to the positive if I recall correctly, you'd want to swap the LED and resistor around in your circuit. Then you could get away with using 0V as your op-amp's ground rail, which I think would work fine. Pic related, set the ratio of one resistor to the other to be a factor of 5, which would give a gain of 6.