LINE sensors

Which type of sensors are good to be used in white line follower robot on blue plane, IR with photo-transistors (OR) LED with LDR????

IR with phototransistors. An LDR will work but they are generally more expensive, have a slower response time, and don't filter out ambient light as well.

Pololu sells a nice Reflectance Sensor Array designed for line-following robots. Even if you're not interested in buying it you will probably find their documentation helpful.

I worked on IR with photo-transistor but they are not giving much variation, only variation of 0.05V which is very very less.. I have used this circuit Mechanical Engineering | College of Science and Engineering
This is the common circuit, everywhere this very circuit is used but its not giving much variation..
by the way i can't buy Pololu as i'm in Pakistan

Why anyone not replying?????? :frowning:

Please help me…
I’m using IR and photo-transistor and they are giving me variation of only 0.05V on blue and white surface…
my source is
any help, where might be the problem is??? Or IR gives not much variation???

I've seen these work well.
What's the theory behind how a part like this works? The kids calibrate them in software for the level returned for light vs dark and make successful line followers.

Are you using the exact same parts - or at minimum, similar parts with the same specifications as the parts shown? If not, then what parts are you using (and what are the specifications of them)?

Finally - once you get one pair working, look into setting up nine pairs in a grid (you can detect T and cross junctions that way - just a little hint).


Not using the same parts as shown there but i bought one from local radio shack and it has not written any specification on it but just said that it is IR and photo-transistor. :~

I couldn't find any IR and photo-transistor on which any specification is written so what should i do now?????