System of auto reversing based on STC89C52 single chip computer is designed. Basic principle of ultrasonic ranging is introduced. Detailed description on structure composition of the system and the design of hardware circuit and software are presented. Temperature compensation is used to eliminate the effect of temperature on sound velocity and improve the ranging precision. Real-time display of distance is realized with LCD in the system and also voice prompt is different when the distance changes. Experimental results show that the measured data is accurate between 30j?500 cm. There are several additional advantages of the automobile reversing radar system, such as high reliability, simple peripheral circuit, practical for use and so on.%本文设计一种基于单片机STC89C52的超声波测距仪汽车倒车系统,介绍了超声波测距的基本原理,阐述了倒车雷达系统的结构组成、硬件电路设计,并在数据处理部分采用温度补偿消除温度对声速的影响,提高了测距精度.倒车距离采用LCD进行实时显示,并通过语音报警电路对不同距离段做出不同的语音提示.实验表明该倒车雷达系统在30～ 500 cm范围内可实现准确测距,具有可靠性较高、外围电路简单、实用性强等优点.
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