sensing red and blue lights differently

[robotics_mait]

How can i sense the red and blue lights differently... What should be the contruction of such a sensor?

 

[vinoth8051]

Hi mait,
you can use LDRs covered with filters (Red, Blue and Green), followed by digital logic to determine the color of incident light. check this link
color sensor circuit diagram
Hope it helps you..

 

[robotics_mait]

can i do so using led and photodiode pair using a 555 ic timer which will generate freq. in the portion of red and blue light respectively?

 

[DXNewcastle]

You can use a photodiode to detect the intensity of light falling on its sensor, but it does not respond to individual cycles of the light (it does not work at the frequency of light, and neither will any circuit connected to it. A 555 timer, for example, cannot operate at the frequency of light.
As already proposed, optical filters over 2 or more sensors can be used to distinguish the colour content of the light. Have a look at some basic colour camera designs.

 

[Chullaa]

Hi guys!

i am working on the same color sensor. I have used a RGB led and an LDR. check brightness response of each light. my readings are not precise as i have not used any color filtration. do u have any idea how can i get these filters...or i can make some filter by myself.

 

[DXNewcastle]

You can make the filters. The coloured filter material is produced in large sheets for lights in the entertainment industry. You should be able to ask a technician in a venue / theatre / stadium / video studio to give you a square centimeter of each primary colour Red, Green, Blue.