第二基于單片機的超聲波倒車?yán)走_系統(tǒng)的設(shè)計(已修改)

　

【正文】 基于單片機的超聲波倒車?yán)走_系統(tǒng)的設(shè)計摘 要近年來，我國的汽車數(shù)量正逐年增加。在公路、街道、停車場、車庫等擁擠、狹窄的地方倒車時，駕駛員既要前瞻，又要后顧，稍微不小心就會發(fā)生追尾事故。因此。增加汽車的后視能力，研制汽車后部探測障礙物的倒車?yán)走_便成為近些年來的研究熱點。為此，設(shè)計了以單片機為核心，利用超聲波實現(xiàn)無接觸測距的倒車?yán)走_系統(tǒng)。工作時，超聲波發(fā)射器不斷發(fā)射出一系列連續(xù)脈沖，給測量邏輯電路提供一個短脈沖。最后由信號處理裝置對接收的信號依據(jù)時間差進行處理，自動計算出車與障礙物之間的距離。目前，國內(nèi)外一般的超聲波測距儀，其理想的測量距離為 1m～5 m，因此大都用于汽車倒車?yán)走_等近距離測距中。本文根據(jù)聲波在空氣中傳播反射原理，以超聲波換能器為接口部件，介紹了基于 AT89C51 單片機的超聲波測距器。該設(shè)計由超聲波發(fā)射模塊、信號接收模塊、單片機處理模塊、數(shù)碼顯示以及聲光告警顯示模塊等部分組成，文中詳細介紹了測距器的硬件組成、檢測原理、方法以及軟件結(jié)構(gòu)。超聲波接收電路使用 SONY 公司的 CX20226A 紅外檢測專用芯片，該芯片常用于 38kHz 的檢波電路，文中通過對芯片內(nèi)部電路的仔細分析，設(shè)計出能夠成功對 40kHz 超聲波檢波的硬件電路，距器使用數(shù)碼管顯示目標(biāo)物的距離。關(guān)鍵詞：超聲波 測距 AT89C51 倒車DESIGN OF ULTRASONIC VEHICLE REVERING SYSTEM WITHULTRASONIC BASEDON MCUABSTRACTIn recent years, China39。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 rearend 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 bee 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 rangefinder. Receiving circuit using the SONY pany dedicated CX20226A infrared detecting chip, the chip used in the detector circuit 38KHz, the text of the chip through the careful analysis of the internal circuit design can successfully 40kHz ultrasonic detection of hardware circuitry and adjustable gain, The use of digital rangefinder display the distance between objects. KEY WORDS AT89C51 Silent Wave。Measure Distance Reversing目 錄摘 要 ............................................................................................................................................IABSTRACT...............................................................................................................................II1 緒論 ............................................................................................................................................1 設(shè)計的現(xiàn)狀 ................................................................................................................1 設(shè)計的意義 ................................................................................................................2 目前國內(nèi)倒車?yán)走_的發(fā)展現(xiàn)狀 .....................................................................22 總體設(shè)計方案 ......................................................................................................................3 超聲波測距 ................................................................................................................4 超聲波測距原理 ................................................................................................測量與控制方法 ..............................................................................................理論計算 ............................................................................................................5 影響精度的因素分析 .......................................................................................6 提高精度的方案及系統(tǒng)設(shè)計 .........................................................................7 測量盲區(qū) ..............................................................................................................8 超聲波傳感器 ..........................................................................................................9 超聲波傳感器原理及結(jié)構(gòu) ...............................................................................9 超聲波傳感器的特性 ......................................................................................11 超聲波傳感器的應(yīng)用 .....................................................................................133 硬件設(shè)計 ...............................................................................................................................14 超聲波發(fā)射電路 ...................................................................................................14 超聲波檢測接收電路 ........................................................................................15 集成電路 CX20226A......................................................................................15 超聲波接收電路 ..............................................................................................17 超聲波顯示及控制部分電路 ........................................................................18 AT89C51 單片機的原理及工作特點 ..........................................................18 單片機實現(xiàn)測距原理 ......................................................................................19 壓電陶瓷超聲波傳感器 (TCF4018TR1)................................................19 穩(wěn)壓電源電路 ...................................................................................................20 顯示電路原理 ...................................................................................................21 溫度測量電路 ...................................................................................................23 鍵盤控制電路 ...................................................................................................234 軟件設(shè)計 ................................................................................................................................23 軟件設(shè)計的要求 ..............