How to make a color sensor?

Question

color sensor must sense a minimum of 8 colors and output has to be in voltage....can someone help me out on this???i searched the net for a working sensor but i can't understand its operation

Answer 1

I think that I would use three photo transistors, one with a red filter in front, one with a green filter and one with a blue filter.

I'd arrange them each in a circuit to give a voltage output and then take these three outputs to the inputs of a simple weighted summing amplifier using an op-amp.

If necessary, I might use an extra, unfiltered photo transistor with a comparator circuit to compensate for variation in illumination.