【正文】 壓，防止反向電壓擊穿三極管的C、E極。在電動機引腳兩端并聯(lián)的電容器C是抗干擾用的，電動機在運轉(zhuǎn)時，他的電刷和整流子之間產(chǎn)生電火花，特別是在電動機轉(zhuǎn)換旋轉(zhuǎn)方向時，電火花會更大，容易干擾電子電路的正常工作，增建這個電容器后可以有效的濾除干擾，免除許多莫名其妙的麻煩。表（1）A端電平 B端電平電動機軸旋轉(zhuǎn)方向01正轉(zhuǎn)10反轉(zhuǎn)在一塊集成電路封裝內(nèi)部有4個2輸入端與非門，我們只使用了其中的2個來構(gòu)成單穩(wěn)態(tài)觸發(fā)器延時電路，剩余的2個還在那里閑著無事可干，現(xiàn)在正好派上用場。三、信號檢測電路該電路如圖7的作用就是檢測出地上的黑線并把這個信號傳遞給單片機，以使單片機做出相應(yīng)的動作。光電三極管通常只有2根引腳，他們的長短是不一致的，對于NPN型的光電三極管而言，較長的一根通常是E極，較短的一根是C極。首先將萬用表置于R*1k電阻擋，用不透光的物體，將光電管遮蓋住，使其處于很暗的環(huán)境中，然后測量光電管兩只引腳之間的正反向電阻。反之如果測量得到的正反向電阻值有非常明顯的差別，一個較小而另一個較大，則所測的管子是光電二極管。（2）電路工作原理。當光電三極管檢測到黑線以后，將輸出高電平信號，然后該信號經(jīng)過兩級放大，再把放大了的信號傳遞給單片機。圖7 信號檢測電路四、系統(tǒng)形成的總電路圖為：圖8 系統(tǒng)總體電路第三章 軟件設(shè)計（一）程序設(shè)計根據(jù)本系統(tǒng)的要求，復(fù)讀機要實現(xiàn)的功能為錄音、放音。為了驗證我們所設(shè)計的單片機最小系統(tǒng)的正確性，我們編寫了簡單的控制程序，通過編程器把程序燒寫到AT89C51的ROM中，來調(diào)試我們的軟件和硬件。 編制不分段錄音程序?qū)⒌刂肪€AA7設(shè)置為高電平，構(gòu)成最簡單的不分段錄音電路。程序名：REC_PLAY2 。入口條件：、 REC EQU 。回放控制端，電平方式 ORG 0000H AJMP STARTSTART: SETB 。關(guān)錄放 SETB PLAYLRETN1: JB ,PLAY 。調(diào)用錄音子程序 JNB ,$ 。判斷播放鍵是否按下 ACALL LPLAYL 。判斷播放鍵是否放開L2: SJMP RETN1。子程序名：LREC。開始錄音 LCALL DELAY10S 。錄音結(jié)束 RET。子程序名：LPLAYL。開始錄音 LCALL DELAY SETB PLAYL 。 *******************延時10s子程序*******************。功能：延時10秒DELAY: MOV R7,100DEL3: MOV R5,100DEL2: MOV R6,250DEL1: NOP NOP DJNZ R6,DEL1 DJNZ R5,DEL2 DJNZ R7,DEL3 RET178。只要將不分段語音錄放控制程序REC_PLAY1中的不分段初始化控制指令取消即可。程序名：REC_PLAY2 ；功能：錄音、放音控制。功能：延時3秒DELAY: MOV R7,30DEL3: MOV R5,100DEL2: MOV R6,250DEL1: NOP NOP DJNZ R6,DEL1 DJNZ R5,DEL2 DJNZ R7,DEL3 RET END（二）程序調(diào)試由于程序不可能一次成功，所以需要對程序進行調(diào)試，最終使程序?qū)崿F(xiàn)所要求的功能。在這其中，對延時程序的調(diào)試很重要，延時的時間必須設(shè)置的合理，否則會觀察不到實驗現(xiàn)象。第四章、英語翻譯The electronics electric circuit design While designing an electronics electric circuit system, first have to definitely the design mission of the system, carry on a project choice according to the mission, then each part in the other party case carry on the design of unit, parameter calculation and spare part choose, the end links each part together and draw a matches design to request of integrity of system electric circuit diagram. One. The design mission of the explicit system request Carry on to the design mission of the system concrete analysis, full understanding system of function, index sign, contents and request, with explicit the system should plete of mission. Two. The project choose The work of this one step requests to be the mission which wants the system to plete to assign to some unit electric circuits, and draw a whole machine principle frame diagram that can mean each unit function. The important mission of the project choice is according to control of knowledge and data, aim at the mission that the system put forward, request and condition, the function design of pletion to presume quest in this process, brave innovation, work hard for to attain the design project reasonable, credibility, economy, the function is wellfound, technique the other party case want to continuously carry on a possibility with defective analysis, finally design a plete frame diagram have to the correct reflection should plete of mission with each constitute part of functions, make clear system of basic constitute with correlation. Three. The design of unit electric circuit, parameter calculation and period choose According to index sign and function frame diagram of system, definitely each parts of mission, carry on the design of each unit electric circuit, parameter calculation and spare part choose.1. The unit electric circuit designThe unit electric circuit is the whole machine of one part, only make the each unit electric circuit design raise the whole machine design level so then can. Each unit electric circuit design ago all needed the mission of each unit electric circuit definitely, draft a function index sign of unit electric circuit in detail, with in front and back the relation of class, analyze constitute of electric circuit a concretely designing, the forerunner39。Flap to concuss electric resistance in machine, electric capacity, flap to concuss frequency etc. the calculation of the good prehension electric circuit of work principle, the exactitude makes use of calculation formula and the calculating parameter then can satisfy a design a request. When the parameter pute, the same of electric circuit may have a few datas, the attention choose a function that can plete an electric circuit design a request, the ability real viable parameter in the fulfillment. Should notice the following problem while puting electric circuit parameter: (1) dollar the work electric current, electric voltage of the spare part, frequency and achievement consume etc. parameter in response to can satisfy the request of electric circuit index sign。 (3) the parameter of electric resistance and electric capacity should choose a calculation value the mark of the neighborhood to call a value. 3. The spare part choose (1) the ponent choose The electric resistance and electric capacity category is much, electric resistance and electric capacity of the exactitude choice are very different electric circuit requests to be different also to the electric resistance and the electric capacity function and the electri