Our tracking car can drive along the runway automatically. No matter how the runway is curved, The car can be driven automatically. We all know that the reflectivity is different when the light source to the white objects and black objects. Here we use red light source. The light is reflected by the ground to the photoresistor. By detecting the resistance of the photosensitive resistor can determine whether the car is Driving in the white area. With the aim of simplifying the complex principle, we first have a by digital circuit to the intelligent tracking car, in the assembly process, we could not only familiar with the mechanical principle gradually can learn to: photocell, a voltage comparator, a motor drive circuit, and other related electronic knowledge. Usage:Smart Robot Car DIY Spare Parts, welding for toy or experiment. Note:It's diy kits. Need to solder by yourself. The color of board(green or blue) is random and cannot be specified. Power Supply:2 x AA batteries(Not included batteries) Tips:The product may be updated constantly,Due To Different Batches, The Actual Product May Have Slight Differences Or Color Differences, Which Does Not Affect Use. Colour:As Shown Material:Plastic Package Contents: 1 * Smart Car Kit(DIY parts, need to be welded by yourself) Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.