hi all,
You think i possible do the line follower robot with speed control??? Robot will run faster when detect the black line. and run slower when detect the blue line. Please give any advice.. Thanks

 

It is possible. YOu will need fancier sensors than normal to tell the difference between a black and blue line.

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So normal IR sensor can differancial black and blue colour???
If cannot. Any recommand??? Because colour sensor is too expensive.

 

May be you can use LDR. It can not detect different colour but different colour may reflect different amount of light. So different voltage will be obtained by the LDR.

 

if ur using microcontroller ..... tkae one 555 timer to generate pulse from ldr. calculate the time of pulse r number of pulse according to ur ckt desing .

then according to the range

 

A CDS cell cannot differentiate between colors, but only change the amount of resistance. A CDS cell cannot differentate between what is a black, blue or green.

Just throwing that out there.

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Light detectors simply give intensity information. If you want color information you either need a detector that doesn't respond to certain wavelengths, or you need to use filters for the various wavelengths. The latter method is by far the most commonly used method. (I consider a photodetector with a built-in filter or monochromator as the latter, not former type. The former type might be represented by the cones in the retina.)

That being the case, you could consider a line follower that had two detectors. One detector would have a filter that allowed max. transmission for one color of interest and the other other would have a filter for the other color of interest. Knowing the ratio of the outputs for color 1
and for color 2 would allow you to determine which line the detector was "seeing."

From a construction standpoint, I would use fixed detectors and filters rather than one detector with movable filters, but either way will work. John

Edit: This may be a bit arcane, but I used the cones as an example of a wavelength selective detector, not filter based detector, because of the very close, molecular association of the protein opsin with the actual signal generator (See: http://en.wikipedia.org/wiki/Rhodopsin).
A better example might be the photoelectric effect one sees with LEDs in which the color sensitivity is due to the doping (See:http://scitation.aip.org/getabs/serv...cvips&gifs=yes
http://scitation.aip.org/getabs/serv...cvips&gifs=yes).