Description: The circuit consists of several parts, namely, photoelectric sensor, voltage comparison and motor drive. Depending on the reflectivity of the black and white parts of the tube, the received photoresistance will vary. LM393 compares the size of the two paths of photosensitive resistance, controls the operation of the motors on both sides, so as to correct the direction of the trolley, and to ensure that the trolley moves along the black track. The motor is equipped with a speed reducer, please do not rotate vigorously to prevent damage. With assembly drawing of the main board of the car. Specification: The assembly steps: Step 1: Welding circuit Electric welding part is simpler, welding sequence according to the principle of component level from low to high, the first welding eight resistance, is important to use multi meter to confirm resistance is correct Step 2: Mechanical assembly The red line is connected to the 3V positive power supply, the yellow line grounding, excess wire can be used for motor wire. Step 3: The installation of a photoelectric circuit Photosensitive resistance and light-emitting diodes (note polarity) is reverse-mounted on the PCB, and the ground distance is about 5 mm, both photosensitive resistance and light-emitting diodes are 5 mm distance. Finally, you can power test. Step 4: Vehicle debugging The right direction is along the universal wheel direction, if you press and hold the left photo resistor, the wheels on the right side of the car should be rotated. Press and hold the right photo resistor, the wheels on the left side of the car should be rotated, if the car driving back, can also exchange the wiring of two motors, if the one side normal and the other side back up, as long as you can swap wiring of back side. Package Includes: 1 x Base board 2 x 35mm Wheels 2 x Rubber Wheel bands 1 x AA Battery holder 2 x Gearded DC Motors 1 x Screw set 1 x LM393 Chipset 1 x 8pin DIP Socket 10 x Resistor 2 x Electrolytic capacitor 2 x Light dependant resistors 2 x Transitors 2 x White LED 2 x Red LED 1 x Power switch 4 x 70mm Leads