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基于单片机的超声波倒车雷达系统的设计
摘要
近年来,我国的汽车数量正逐年增加。在公路、街道、停车场、车库等拥挤、狭窄的地方倒车时,驾驶员既要前瞻,又要后顾,稍微不小心就会发生追尾事故。因此。增加汽车的后视能力,研制汽车后部探测障碍物的倒车雷达便成为近些年来的研究热点。为此,设计了以单片机为核心,利用超声波实现无接触测距的倒车雷达系统。工作时,超声波发射器不断发射出一系列连续脉冲,给测量逻辑电路提供一个短脉冲。最后由信号处理装置对接收的信号依据时间差进行处理,自动计算出车与障碍物之间的距离。目前,国内外一般的超声波测距仪,其理想的测量距离为1m~5 m,因此大都用于汽车倒车雷达等近距离测距中。本文根据声波在空气中传播反射原理,以超声波换能器为接口部件,介绍了基于AT89C51单片机的超声波测距器。该设计由超声波发射模块、信号接收模块、单片机处理模块、数码显示以及声光告警显示模块等部分组成,文中详细介绍了测距器的硬件组成、检测原理、方法以及软件结构。超声波接收电路使用SONY公司的CX20106A红外检测专用芯片,该芯片常用于38kHz的检波电路,文中通过对芯片内部电路的仔细分析,设计出能够成功对40kHz超声波检波的硬件电路,距器使用数码管显示目标物的距离。
关键词:超声波测距 AT89C51 倒车
DESIGN OF ULTRASONIC VEHICLE
REVERING SYSTEM WITH
ULTRASONIC BASEDON MCU
ABSTRACT
In recent years, China's number of cars is increasing every year. Highways, streets, parking, garage and other crowded places narrow reverse, the driver should not only forward but also looking back, a little rear-end careless accidents can after the increase of motor vehicles as the ability to detect obstacles on the development of the rear of the car reversing radar has e the research hotspot in recent years. the ultrasonic transmitter continuously emits a series of consecutive pulses to the measurement of logic circuits to provide a short pulse. Finally, signal processing devices based on the received signal for processing the time difference, automatic calculation of turnout and the distance between obstacles. Ultrasonic Ranging simple, low cost, easy production, but the transmission speed by a larger weather can not be precise range; In addition, the ultrasonic energy and the attenuation is directly proportional to the square of the distance, the farther the distance, the lower sensitivity and thus Ultrasonic Ranging way so that only apply to a shorter distance. At present, ultrasonic range finder at home and abroad in general, the ideal distance of the measurement 1~ 5 m, based on AT89C51 ultrasonic range-finder. Receiving circuit using the pany dedicated CX20106A infrared detecting chip, the chip used in the