View the object through 3 sensors, each of which has a different color filter in front of it (red-blue-green or red-blue-yellow, depending). Different colors produce different intensities at each sensor.
This I believe is the currently accepted method for many commercial products.Processing digital image data from a video or still camera could be a simple approach.
Alternative method which is simple but less accurate: Use one or more sensors to ensure sensitivity to a wide color range the illuminate it with different color light sources.
You don't tell us the size, shape or how many many colors it has, and how fast the measurement has to be taken but in principle: use an LDR and say a red and blue LED light source. You use the RED LED as the sole illuminator and measure the reflected light at the LDR then you repeat with the blue LED. From the differences in reflected light you can determine the color of the original surface. You may have to take into account how shiny the surfaces are, a glossy one may produce different result to a matt one.
Brian.
Processing digital image data from a video or still camera could be a simple approach.
View the object through 3 sensors, each of which has a different color filter in front of it (red-blue-green or red-blue-yellow, depending). Different colors produce different intensities at each sensor.
May i know any particular sensor with name you are talking about. Your method looks similar to the one, shared by Brian. If not then please elaborate.
May i know any particular sensor with name you are talking about. Your method looks similar to the one, shared by Brian. If not then please elaborate.
II am planning to replace the Photo-transistor with LDR and then will check the results..
The detector should ideally have uniform sensitivity for the three radiations. Else you will be needing independent calibrations for the three light sources.
You will also need to calibrate with a white sheet: it should give the same reading for RGB sources.
I guess pin 2 is your ground connection?
I think you ought to play with resistor values going to the phototransistor, so that you get into a range where variations in light intensity cause electrical variations from the phototransistor.
A midway led intensity should cause a midway voltage from the phototransistor. R4 value is important in achieving this.
If R5 is too large then you lose sensitivity of response.
Also try taking output from its collector terminal, instead of its emitter.
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