【正文】 kHz 脈沖的產(chǎn)生與超聲波發(fā)射 測距系統(tǒng)中的超聲波傳感器采用 UCM40 的壓電陶瓷傳感器，它的工作電壓是40kHz 的脈沖信號，這由單片機(jī)執(zhí)行下面程序來產(chǎn)生。超聲波在空氣中的傳播速度為 340m/s，根據(jù)計時器記錄的時間 t，就可以計算出發(fā)射點距障礙物的距離s，即：s340t/2超聲波測距系統(tǒng)的電路設(shè)計 系統(tǒng)的特點是利用單片機(jī)控制超聲波的發(fā)射和對超聲波自發(fā)射至接收往返時間的計時，單片機(jī)選用 C51，經(jīng)濟(jì)易用，且片內(nèi)有 4K 的 ROM，便于編程。強(qiáng)度較強(qiáng)的脈沖會比強(qiáng)度較弱的脈沖超過界限的時間早點，因此我們會認(rèn)為強(qiáng)度較強(qiáng)的脈沖屬于較近的物體。進(jìn)一步說，從脈沖起始點到剛好超過界限之間的時間段隨著脈沖的強(qiáng)度而改變。這個界限恰恰選于噪音水平之上，然而脈沖到達(dá)時間被定義為脈沖信號剛好超過界限的第一時刻。反之，如果兩電極間未外加電壓，當(dāng)共振板接收到超聲波 時，將壓迫壓電晶片作振動，將機(jī)械能轉(zhuǎn)換為電信號，這時它就成為超聲波接收器了。超聲波發(fā)生器內(nèi)部結(jié)構(gòu)，它有兩個壓電晶片和一個共振板。因此，設(shè)計好的超聲波測距儀就顯得非常重要了。而設(shè)計研制箱涵排水疏通移動機(jī)器人的自動控制系統(tǒng)，保證機(jī)器人在箱涵中自由排污疏通，是箱涵排污疏通機(jī)器人的設(shè)計研制的核心部分。因此，經(jīng)常出現(xiàn)開挖已經(jīng)建設(shè)好的建筑設(shè)施來改造排水系統(tǒng)的現(xiàn)象。關(guān)鍵詞：超聲波，測距儀，單片機(jī)前言 隨著科技的發(fā)展，人們生活水平的提高，城市發(fā)展建設(shè)加快，城市給排水系統(tǒng)也有較大發(fā)展，其狀況不斷改善。因此，深入研究超聲的測距理論和方法具有重要的實踐意義。storage results MOV A, R7 SUBB A, 3CH MOV 30H, A SETB EX0。read the time value MOV R6, TL0 CLR C MOV A, R6 SUBB A, 0BBH。原文出處：傳感器文摘 布拉福德:1993年 第13頁摘要Ultrasonic ranging technology has wide using worth in many fields，such as the industriallocale，vehicle navigation and sonar engineering．Now it has been used in level measurement，selfguided autonomous vehicles fieldwork robots automotive navigation，air and underwater targetdetection，identification，location and so on．So there is an important practicing meaning to learn theranging theory and ways improve the precision of the ultrasonic ranging system in hand，satisfy the request of the engineering personnel for the ranging precision，the bound and the usage，aportable ultrasonic ranging system based on the single chip processor was developed the development of science and technology the improvement of peoplesstandard of living speeding up the development and construction of the system have greatly developed their situation is constantly to historical reasons many unpredictable factors in the synthesis of her time the citydrainage particular drainage system often lags behind urban there are often good building excavation has been building facilities to upgradethe drainage system brought to the city sewage and it is clear to the citysewage and drainage culvert in the sewage treatment is very important topeoples robots designed to clear the drainage culvert and the automaticcontrol system Free sewage culvert clear guarantee robot the robot is designed to clear theculvert sewage to the System is the core ponent of the development ofultrasonic range it is very important to design a good ultrasonic principle of ultrasonic distance measurement The principle of piezoelectric ultrasonic generator Piezoelectric ultrasonic generator is the use of piezoelectric crystal resonators to generator the internal structure as shown it has two piezoelectric chip and aresonance its two plus pulse signal the frequency equal to the intrinsicpiezoelectric oscillation frequency chip the chip will happen piezoelectric resonance andpromote the development of plate vibration resonance ultrasound is the two are not interelectrode voltage when the board received ultrasonic resonance itwill be for vibration suppression of piezoelectric chip the mechanical energy is convertedto electrical signals then it bees the ultrasonic traditional way to determine the moment of the echos arrival is based onthresholding the received signal with a fixed threshold is chosen well abovethe noise level whereas the moment of arrival of an echo is defined as the first moment theecho signal surpasses that intensity of an echo reflecting from an objectstrongly depends on the objects nature size and distance from the the timeinterval from the echos starting point to the moment when it surpasses the thresholdchanges with the intensity of the a consequence a considerable error may occurEven two echoes with different intensities arriving exactly at the same time will surpass thethreshold at different stronger one will surpass the threshold earlier than theweaker so it will be considered as belonging to a nearer principle of ultrasonic distance measurement Ultrasonic transmitter in a direction to launch ultrasound in the moment to launch thebeginning of time at the same time the spread of ultrasound in the air obstacles on his wayto return immediately the ultrasonic reflected wave received by the receiver immediatelystop the in the air as the propagation velocity of 340m / s according tothe timer records the time t we can calculate the distance between the launch distancebarrier s that is: s 340t / 2 Ranging System for the Second Circuit Design System is characterized by singlechip microputer to control the use of ultrasonictransmitter and ultrasonic receiver since the launch from time to time singlechip selectionof 8751 economictouse and the chip has 4K of ROM to facilitate diagram shown in Figure 1 circuit principle diagram 40 kHz ultrasonic pulse generated with the launch Ranging system using the ultrasonic sensor of piezoelectric ceramic sensors UCM40its operating voltage of the pulse signal is 40kHz which by the singlechip implementationof the following procedures to : mov 14h 12h ultrasonic firing continued 200mshere: cpl output 40kHz square wave nop nop nop djnz 14h here ret Ranging in front of singlechip termination circuit input port single chipimplementation of the above procedure the port in a 40kHz pulse output signal afteramplification transistor T the drive to launch the first ultrasonic UCM40T issued 40kHzultrasonic pulse and the continued launch of the right and the left side ofthe circuit respectively then input port and the working principle and circuit infront of the same Reception and processing of ultrasonic Used to receive the first launch of the first pair UCM40R the ultrasonic pulsemodulation signal into an alternating voltage the opamp amplification IC1A and afterpolarization IC1B to is locked loop with audio decoder chip LM567 internalvoltagecontrolled oscillator center frequency of f0 1/ capacitor C4 determinetheir target in the launch of the carrier frequency on theLM567 input signal is greater than 25mV the output from the high jump 8 feet into alowlevel as interrupt request sign