Using LDR's to track the black line

A line follower robot works on the same principle as a light follower robot. However, instead of tracking light the LDR (Light Dependant Resistor) is used to track the black line. This is done by programming the chip connected to the LDR to differentiate the line colour and the colour of its surroundings (in our case a black line on a white background).

It is possible to use one LDR to act as the sensing device to track the line; however the buggy would not follow the line smoothly. To improve the smoothness (resolution) of the line following, more LDR’s would need to be used.

As we are limited to the number of LDR’s we can connect to our project board the group have made a decision to use 2 LDR’s in a line combination.

The diagram above shows how the buggy could follow the black line. It uses the two LDR's (S1 and S2) to navigate its way along the line in a zig zag motion. The LDR's (S1 and S2) read the intensity of the light being reflected from the track surface. So, when S1 is directly above the black line the light intensity is low making the buggy turn left. Smilarly, when S2 is directly above the black line the light intensity is low making the buggy turn right. We could include another case where neither S1 or S2 are above the black line. When this is the case both wheels would be turning at the same rate, therefore keeping the buggy moving in a forward direction.