color sensor

[flames]

hi,

i'm intending to make an autonomous robot that will take a colored ball and bring it to a box with the same color.

i want to ask about the color sensor. how does a color sensor work? what is its output? is it voltage or frequency? and which type should i buy for the color sensor?

[Razor Concepts]

There are roughly three billion types of color sensors. Which one do you have in mind? 

The most basic way would be to take 3 different light sensors that are sensitive to different wavelengths of light.

[flames]

ya, i just need the basic one. is it better to build it ourselves or buy it?

since after some reading about color sensor from this website n forum, i found out that it is quite easy to build but note easy to implement, as how will the output be? is it in analog voltage or what? and does the output correspond to the color's frequency linearly?

[macdad-]

I have tested this before and reversing an LED works as a great color sensor(only produces volts when light of its own usual emission wavelength is applied). I got this idea from here:
http://www.robotroom.com/ReversedLED.html

Note: The voltage output from the LED is relatively low(about 0.8-1.5 volts depending upon how much light is shined upon it), you may want to use an Op Amp, or just a low voltage transistor.

[flames]

But how far the object needed to be from the LED so the LED can detect it?

[macdad-]

With my test with standard brightness, standard current draw, etc LEDs, the source has to be atleast 2 inches away to get a maximum voltage output from the LED. I'm not sure about high brightness LEDs and such with their reverse-color-sensor attributes.

The maximum output I got from a LED held 2 inches away from my Desk Lamp(The LED was a Yellow LED, and the desk lamp was a halogen), was about 1.2 Volts. Give or take .2 volts