摘  要 利用超声波来进行测距由于在使用中不受光照度、电磁场等一些因素的影响，而且超声波传感器的结构相对简单，成本较低，并且超声波传播速度快且稳定，方便检测与计算，在汽车倒车、测量等许许多多的方面都已经得到了广泛的应用。85231

本次毕业设计是以STC89C51单片机为核心设计的倒车雷达系统，分析一些倒车雷达的设计原理。本次设计主要是利用超声波测距的特点和优势，再将超声波测距系统和STC89C51单片机结合在一起组成一个倒车雷达。整个系统分为软件和硬件两个部分，硬件部分主要由单片机硬件接口电路、超声波发射电路和超声波接收电路、LED数码管显示电路、电源电路和报警电路组成，软件部分主要是由主程序和超声波发射接收中断程序、距离计算子程序和显示报警子程序等部分组成。驾驶员只需坐在车内就可以知道汽车与后方障碍物之间的距离，提高倒车时的安全性。

Abstract Using ultrasound to range as in use are not subject to the influence of some factors such as light, electromagnetic field, and the structure of the ultrasonic sensor is relatively simple, low cost, and the ultrasonic transmission speed and stable, convenient detection and calculation, in reverse, many aspects such as the measurement has been widely used。

This graduation design is a STC89C51 microcontroller as the core design of reversing radar system, analysis of some of the design principle of the reversing radar。 This design mainly is to use ultrasonic ranging features and advantages, then the ultrasonic ranging system and STC89C51 microcontroller combine together to form a reversing radar。 Software and hardware of the whole system is pided into two parts, hardware part is mainly composed of single chip microcomputer hardware interface circuit, ultrasonic launch circuit and ultrasonic receiving circuit, LED digital tube display circuit, power circuit and alarm circuit, software part mainly consists of the main program and receiving interrupt program, ultrasonic launch distance calculation subroutine and display alarm subroutine, etc。 The driver just sitting in the car the car is known and the distance between the rear obstacles, to improve the safety of reversing。

毕业论文 关键词： 超声波 ; STC89C51 ; LED ; 测距 ; 传感器

  Keyword: ultrasound; STC89C51; LED; Range; The sensor

                 目  录

目  录 4

1 绪 论 6

1。1选题的背景 6

1。2研究的内容 7

1。3拟解决的主要问题 7

2 电路总体设计 8

2。1 电路总体设计框图与简单的功能介绍 8

3单片机概述 9

3。1 STC89C51介绍 9

3。2 STC89C51外部结构与I/O口介绍 10

3。3 STC89C51内部构成 12

4 超声波测距模块概述 13

4。1 HC-SR04超声波测距模块的功能特点 13

4。2 HC-SR04的管脚排列和主要技术参数 13

4。2。1 管脚简介 13

4。2。2 HC-SR04的主要电气参数 14

5系统硬件电路设计 15

5。1硬件电路总体设计介绍