【正文】 入超聲波接收傳感器內(nèi)引起誤判斷所以程序要求超聲波發(fā)射若干時間后必須停止若干時間這個時間大約是超聲波在空氣中傳播 20 多厘米的時間這段時間內(nèi)是不接受信號的主要就是為了躲開直接傳導的信號避免引起誤判斷 實物圖 42 軟件實現(xiàn)與操作 系統(tǒng)軟件的整體結構各模塊在前面已介紹先在 WAVE 下編完程序 然后編譯好通過后生成目標文件十二和十六進制燒錄到 89S52 片子中時先下載監(jiān)控程序加上我們編譯好的十六進制程序再寫入芯片中即可調(diào)試通過不斷修改完善最終很好地實現(xiàn)了我們的目標 根據(jù)實際情況可以修改超聲波發(fā)生子程序每次發(fā)送的脈沖寬度和兩次測量的間隔時間以適應不同距離的測量需要根據(jù)所設計的電路參數(shù)和程序測距儀能測的范圍為 27cm400cm 測距儀最大誤差不超過 3cm 系統(tǒng)調(diào)試完后應對測量誤差和重復一致性進行多次實驗分析不斷優(yōu)化系統(tǒng)使其達到實際使用的測量要求 測距儀改進的設想 電路板上包括超聲波收發(fā)傳感器接收放大電路四 位 LED 數(shù)碼顯示四位按鍵四個按鈕和蜂鳴器屬于功能預留程序中無定義電源部分自帶整流濾波穩(wěn)壓電路允許交流 7～ 15V或者直流 9～ 16V這是為后續(xù)開發(fā)應用所預留的可以在程序中定義為開關功能按下一個按鍵電路板開始測距按下另一個按鍵電路板停止測距或者定義為多檔距離報警設定當檢測到低于設定距離時驅動蜂鳴器報警其我們的電路板也可以加以改進例如用 1602 的液晶模塊代替數(shù)碼管顯示增加語音電路實現(xiàn)語音播報探測距離等等 A／ DCAD 線路制版電路安裝調(diào)試等完整環(huán)節(jié)形成電子整機雖然在制作過程中我們大家都盡心盡力團結一致克服困難但在軟件下載時遇到了不少的阻力但在老師和我們大家的不斷努力和協(xié)助下通過使用現(xiàn)有的單片機應用板將自己的程序下載進去不斷校改多次調(diào)試后得到了我們想要的結果 從而完成了畢業(yè)設計的項目要求經(jīng)過自己親手的實踐過程使我學到了許多課本里學不到的東西積累了一定的經(jīng)驗和教訓在實踐的過程中鍛煉了自己的動手能力和團隊協(xié)作能力為自己以后能更快的投入工作提供了一定的經(jīng)驗 英語翻譯 Microcontroller reset is to make the CPU and other system features are in a defined initial state and from this state to work reset PC 0000H the microcontroller from the first a unit to take mand Whether it is connected to the microcontroller when the power is just the beginning or after power failure or failure to be reset MCU reset conditions are the RST pin must be coupled with continued two machine cycles ie 24 oscillations is high Clock frequency in this article 12MHz each machine cycle is 1μs then the only 2μs time high above appears in the RST pin high after the implementation of the second machine cycle reset Reset circuit constituted by the capacitor series resistance bined with the map the capacitor voltage can not be mutatedin nature can know when the system is a power RST will be a foot high and that the duration of this high by the circuit The RC values to decide Appropriate bination of RC values can ensure a reliable reset The circuit in addition to a poweron reset functions to reset just press the RESET button then power through resistance voltage reset in the RESET high end Clock circuit main task is to provide a working frequency Internal microcontroller used to form a highgain inverting amplifier oscillator the amplifier input and output are XTAL1 and XTAL2 XTAL1 and XTAL2 on the external clock source can constitute a clock circuit Both internal and external clock generation mode This design uses the internal clock generation means Circuit connection shown in Figure 32 both ends of the jumper XTAL1 and XTAL2 crystal resonator oscillator frequency 12MHZ and internal selfexcited oscillator inverter constituted The issue of pulse timing control directly into the onchip ponents In addition the capacitance of the frequency tuning role as an external crystal oscillator capacitor selection 20pF practical application and capacitor resonator near as possible to install in the SCM to reduce the parasitic capacitance the oscillator stable and reliable work Ultrasonic transmitting circuit includes ultrasonic generator circuit and the ultrasonic transmitter control circuit of two parts ultrasound probes also known as ultrasonic transducer use CSB40T 40KHz is the use of ultrasonic oscillation drive circuit 555 produce ultrasonic probe 555 constituted by the multivibrator timer shown in Figure 33 Power the power by charging the capacitor and when 1 3 the oscillator output 1 the discharge end When the charge to ≥ 2 3 the oscillator output flip to 0 then discharge tube turns on the discharge end DIS grounded capacitor C discharges through the ground so that decline Present down to ≤ 1 3 the oscillator output and turn into 1 discharge and cutoff time so that the discharge end DIS is not grounded power and again by charging the capacitor and also allows from 1 3 up to 2 3 flipflop flip took place again and again to be a continuous change in the output of the oscillator pulse Pulse width of ≈ 07 determined by the capacitor discharge time 07 determined by the capacitor charging time pulse period T ≈ The oscillation frequency calculated as f 143 2 Ultrasonic transmitter circuit shown in Figure 34 will be designed to be adjustable resistance for the purpose of adjusting the signal frequency so that the transducer 40kHz with the natural frequency of the same Formed using 555 timer multivibrator duty cycle can regulate a wide range and circuit design is simple small footprint 555 timer is reset terminal 4 feet use it to co