Color sensor

Thread Starter


Joined Feb 8, 2012
Sir, i am a student taking electronics subject in our university. i would like to have some advice in preparing our project(Color sensor). i found a diagram of this circuit having 8 colors exactly what we really need. i made the sensor strictly following the diagram but i can not figure out why it doesn't sense the other colors, can you help me with my problem sir...

this is the diagram i follow

thank you sir...


Joined Apr 5, 2008

Perhaps the inputs of the digital circuits do not match with the signals from the sensors.
You could make 3 comparators for the sensors, so there are distinct levels for the colors.



Joined Apr 24, 2011
At best, that will make a crude color sensor (which may be all you require, that is your decision). It appears an an "idea" circuit, someone had an idea and wrote it down but never built one. I say that because there is now way VR1 2 and 3 have any effect on the circuit performance.

Be that as it may, each input is an LDR from 9V to a 200K resistor. The junction is supposed to go from 0V to 9V when that color light is falling on the LDR. You can use an ohmmeter to check that part out. You will need to find out just how much light this thing needs to react, that depends on which specific LDR you are using.

All is not lost, the trip point can be changed by changing the 220K resistors.

The BLUE GREEN and RED indicators mean some sore of color filter to allow just that color thru to the LDR. That is how it distinguishes colors.

You may be better serves to check out a company such as TAOS Semi who make color detection chips.

Thread Starter


Joined Feb 8, 2012
i should remove VR1 2 and 3 and change the value of the 220k resistor?....
and i also just found so i just try iy out but the outcome is worst...
and does this need to use a "COLORED LIGHT" or just a reflection of color from objects that has colors?....

by the way...i don't know how to edit my profile...>:D

thankzz again sir...
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