I wish to build a line follower, which can follow red line on white background, i tried with IR sensors but it can't distinguish red from white...
Which sensor should i use...???
-> white LED with photo-transistor
-> white LED with LDR
-> red LED with photo-transistor
-> red with LDR
-> IR with LDR
-> Any other
Please help...
forgot to mention, i tried IR with photo-transistor (photo-diode).
You want a phototransistor sensitive to the mid/upper end of the spectrum and use something like a green LED. Green reflected of red wil be pretty dark whilst it should be bright reflected off white. A RED Led will be bright off both. LDRs are probably a bit slow for line following.
GREEN LED with photo-transistor . 
but have a look look at the specs of the phototransistor 
-Thanks Groove
@newbie: how are you going to differentiate a red line with a red LED (unless it is on a green background?)
:-[ Oops got the conccept worng :-X
@newbie: how are you going to differentiate a red line with a red LED (unless it is on a green background?)
@newbie: how are you going to differentiate a red line with a red LED (unless it is on a green background?)
i replied
Oops got the conccept worng
i went wrong with the part as to how a item gets it colour ( absorbs the other colours and reflects it's own )
i took it the other way !
hey thanxs a lot guys...
i'll build it n chk d result...
Why a red line? Why not black ?
Because it is to be used to recreate the Highland regiment's exploits at the Battle of Balaklava?
Groove ;D
But how many other on this board will understand that?
Also what if the line is thick and not thin.