This is the circuit diagram of white line follower toy. The actuator of the toy is the DC motor. This circuit can be used for a toy car to follow a white line, this circuit also known as very simple robot: “line follower without microcontroller”. The motor is either a 3v type with gearing to steer the car or a rotary actuator or a servo motor.
How the circuit work..?
When equal light is detected by the photo resistors the voltage on the base of the first transistor will be mid rail and the circuit is adjusted via the 2k2 potensiometer so the motor does not receive any voltage. When one of the LDR’s receives more (or less) light, the motor is turned on / activated. And the same thing will be happen when the other LDR receives less or more light.
You can see the below video as the result of this circuit project: