Hi,
a line-following robot follows an easy principle: it detects the brightness differences on the ground and moves accordingly
When you use a single light sensor, you follow the edge of the line, making it more of a border-follower. When the robot is on the dark side, he turns to the light one, and vice-versa.
You often see robots doing a little zigzag over a line, that happens when they are not well ballanced.
With two light sensors, you take their brightness difference and turn accordingly. So for example, when your left sensor is on the line, showing black, and the right one isn't, showing white, the robot turns towards the line. It turns slower with a smaller brightness difference, when the sensor only sees a part of the line.
The two VIs you posted both look like a single sensor configuration. If you have a second sensor, I vould definitely recommend a double-sensor-configuration. For the beginning, just play a little with the sensor, and look at the brightness-values they give you back. Once you realise which value corresponds to which surface, you can then try to calcutate the difference, and so you can see if you are too much on the left or on the right. As a 3rd step, you can the use this information to control your wheel speeds.
Good luck, and have fun with your project!
Oliver
