This circuit will activate a motor when the LDR detects a certain level of light.
To use this in a Line Following Buggy you need 2 of the circuits below. The LDRs are mounted about 300mm apart with an LED lit between them facing the floor. The left LDR controls the right motor and vice verca. The buggy should follow a white line against a dark background.
If the buggy drifts left, the right motor stops, causing the left motor to make the buggy pivot around the right wheel until the line is found again. When the strip runs out, the buggy will stop.
Circuit Voltage: 4.5 to 12 volts
Set VR1 at the mid point.
Try using the Schmitt on or off to suit certain conditions. VR1 sets the light level required to enable motor to run. Adjust VR1 so that the motor switches off when the buggy drifts off line.
For reliable operation, use 3 x100nF capacitors between the motor connections and the case. Motors produce very strong electrical interference.
The white line on the floor should contrast as much as possible from the flooring beneath it. Setting the correct brightness for the LED is also important.