2018 IEEE 3rd Advanced Information Technology, Electronic and Automation Control Conference(IAEAC 2018) Design of distance measuring and reversing system SUN Zhi1，YANG Yi1，WANG ZHI-sheng* 1.Research Institute of Photonics, Dalian Polytechnic University 313989901@qq.com, 329112607@qq.com, 23439176@qq.com Abstract—The main work of this paper is to design and implement a set of ultrasonic ranging system which uses STC89C51 single chip microcomputer as the main control chip, uses ultrasonic ranging sensor HC - SR04 as the ranging method, and uses DS18B20 temperature sensor to correct the sound speed in the current measuring environment, displays and alarms the ranging result with LCD12864 liquid crystal display and buzzer, and supports the function of modifying the alarm distance. enhancement of the ultrasonic wave frequency, the wavelength of the ultrasonic wave will also become longer. when the frequency of the ultrasonic wave reaches a certain level, it will lead to the inability to pass through weak gas. However, if the frequency of ultrasonic wave is too low, it will cause the ultrasonic wave to decay directly to a very weak frequency band, which will adversely affect the measurement accuracy. B. Ultrasonic sensor Ultrasonic sensors are sensors that generate ultrasonic waves themselves and receive echoes. The principle of ultrasonic wave generation by ultrasonic sensors is to convert electrical energy into mechanical energy, and the principle of receiving echo signals is to convert mechanical energy into electrical energy[1]. Keywords—single-chip; alarm; sensing; microcomputer I. INTRODUCTION Due to the problem of driver's vision, there are often scraping accidents with pedestrians and obstacles in the process of backing up and parking, causing danger. In essence, the reversing radar system is a kind of safety assistance system aimed at the parking process of a vehicle. the system alerts and alerts the driver about the surrounding environment during the parki