Line Following Robot

I got a project of building a line following robot. The robot has to follow a track with one side being White Background with a blue line and the other black background with a blue line.


1) Firstly, How is possible to sense the blue line with blackground.

2) I want to use three sensors, the circuit diagram attached to this post use 2. how can this circuit diagram can be modified to include three sensors and a the component H bridge in the circuit.

Thanks for the help

You really shouldn't need a third sensor. Most simple light sensors are not color specific, just shades of gray.

It is possible to adjust the sensitivity of your sensors (with R7 and R8) to varying shades of gray. Not easy, I'll admit, but doable.