TJ-56-687Ultrasonic Automatic Obstacle Avoidance Intelligent Car DIY Kit. The car automatically advances, and when the sensor senses an obstacle in front, it automatically turns left or right, or even directly reverses to avoid the obstacle and continue moving forward. The sensing distance of ultrasound can be reset by pressing the button. [Operational Principle] The ultrasonic obstacle avoidance system is based on the reflection of acoustic waves when encountering obstacles. The ultrasonic sensor measures the time difference between mitted and received ultrasonic waves to calculate the distance between the obstacle and the sensor. By monitoring changes in this distance, the system achieves automatic obstacle avoidance functionality. tip: Delivery without 4 AA batteries Material: abs colour: As Shown Package Contents: 1 x Ranging and obstacle avoidance car (Shipped in bulk) 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.