smart tracking car is based on the principle of the light reflectivity difference, when light emitting on the white and black items, the red LED and photo receptor as the sensoring circuit to control the car running direction automatically, a photo resistance is used to tell robot car whether its on the way or not, and run directly along the black tracking line. 

Motor: 2 pcs stepping motors. Tracking line Width: 16 mm / 0.63 inch, you can use the 1.5-2.0 cm black electrical tape on the ground to design the multifarious runaway. Power supply: AA battery (not included).