【正文】 ine and display subroutine and voice alarm subroutine and other parts. Due to the propagation velocity of ultrasonic wave in air is fixed, therefore this design by STC89C51 single chip microputer to calculate the roundtrip time of ultrasound from launch to be accepted, and transmission distance is calculated to achieve the purpose of realtime measuring distance. Circuit design part of the design is simple and reasonable, superior performance, stable operation range fast puting method is simple, and easy to achieve the purpose of realtime monitoring, and reached the industrial measurement error on the practical requirements.Keywords: STC89C51, ultrasonic, digital tube, voice alarmIII第 III 頁目錄第一章 緒論 ...........................................................................................................................................1 課題研究的現(xiàn)狀和發(fā)展歷史及意義 ............................................................................................1 汽車防撞系統(tǒng)的發(fā)展現(xiàn)狀 ............................................................................................................2 本課題的主要研究內(nèi)容 ................................................................................................................2第二章 超聲波測距的原理 .....................................................................................................................4 超聲波的基本理論 ........................................................................................................................4 超聲波的傳播速度 ................................................................................................................4 超聲波對聲場產(chǎn)生的作用 ....................................................................................................4 超聲波傳感器 ................................................................................................................................5 超聲波測距系統(tǒng)原理 ....................................................................................................................5 測量與控制方法 .............................................................................................................................6 控制系統(tǒng)方框圖 ............................................................................................................................6第三章 單片機(jī)主機(jī)系統(tǒng)電路 .................................................................................................................8 單片機(jī)主電路 ................................................................................................................................8 復(fù)位電路 ........................................................................................................................................93. 3 時鐘電路 .......................................................................................................................................93. 4 按鍵電路 .....................................................................................................................................103. 5 蜂鳴器電路 .................................................................................................................................10第四章 系統(tǒng)主要硬件設(shè)計 ...................................................................................................................12 方案論證與比較 ..........................................................................................................................12 超聲波發(fā)射電路: ..................................................................................................................12 超聲波接收電路 ...................................................................................................................13 最終方案確定 ..............................................................................................................................15第五章 系統(tǒng)的硬件結(jié)構(gòu)設(shè)計 ...............................................................................................................17 單片機(jī)的功能特點及測距原理 ..................................................................................................17 單片機(jī)的功能特點 ...............................................................................................................17 單片機(jī)實現(xiàn)測距原理 ...........................................................................................................17 超聲波發(fā)射電路 ..........................................................................................................................18 超聲波檢測接收電路 ..................................................................................................................18IV第 IV 頁 ISD170