This is white line follower circuit. 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 potentiometer 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 happen when the other LDR receives less or more light.
10R, 440k, 220K, 470K, 2.2k, 1K
100uf, 100 or 330nf
2pcs of 3v Battery