江南大学物联网工程学院电子技术课程设计实验报告2014

1江南大学物联网工程学院电子技术课程设计实验报告实验名称：正弦波发生、频率显示电路专业班级：____实验时间：2014.6.20-2014.6.25学生姓名：学号：_______同实验者：实验成绩：2目录一、题目名称············································4二、设计任务和要求·······································4三、电路及工作原理·······································4（a）总体框图及工作原理··································4（b）单元电路及工作原理··································5（1）正负电源电路·····································5（2）正弦波发生及波形变换电路·························5（3）单稳态定时电路···································6（4）频率计数显示电路·································7（5）超量程指示电路···································8（6）控制电路·········································8（c）完整电路图··········································9四、安装与调试··········································10（a）使用仪器仪表·······································10（b）中规模器件的管脚图及功能表·························10（1）uA741··········································10（2）555定时器·····································10（3）CD4511·········································11（4）CD4001·········································11（5）共阴极数码管···································123（6）MC14553········································12（c）总管脚图···········································12（d）安装················································13（e）测试················································14（1）正弦波电路测试································14（2）正弦波与波形变换电路测试······················14（3）控制电路测试··································15（4）控制电路与单稳态定时电路测试··················15（5）电路整体测试··································16（e）测试方法与技巧······································17（f）调试中出现的故障、原因及排除方法···················18五、Protel电路图及元件清单·······························18（a）元件清单············································19（b）Protel电路图········································19六、实验总结·············································20七、收获和体会···········································204一、题目名称正弦波发生、频率测量显示电路二、设计任务和要求正弦波振荡频率100～1000Hz，输出信号幅度5±5％V；（1）用3位数码管显示振荡频率；（2）能自动连续测量、显示频率，测量周期为4S；（3）用中规模集成电路实现。三、电路及工作原理（a)总体框图及工作原理图1正弦波发生电路组成框图工作原理：正弦波振荡器自激振荡产生正弦波输出信号；波形变换电路将正5弦波变换成同频方波，便于计数；控制电路产生4s的循环信号循环驱动单稳态；单稳态产生1s的暂稳态信号，驱动计数器，计数1s内同频方波个数，即方波频率，也是正弦波频率，并由译码显示电路显示。自此，便完成了4s循环计数显示频率。计数器超量程会输出超量程信号，驱动超量程指示电路，显示超量程。控制电路还输出清零信号和超量程复位信号，用于每次开始计数时时清零计数器及复位超量程信号。（b）单元电路及工作原理(1)正负电源电路数字电路试验箱上只有+5V电源，我们以中间为零电位，上下便分别为+2.5V和-2.5V，如图（2）正弦波发生及波形变换电路因振荡频率要求不高，故采用RC文氏振荡器。考虑到要数字显示振荡频率，需对正弦波进行波形变换以便计数。正弦波发生及波形变换电路如图2所示RC桥式正弦波振荡电路以RC串并联网络为选频网络和正反馈网络，以电压串联负反馈电路为放大环节，具有振荡频率稳定、带负载能力强、输出电压失真小等优点。波形变换电路用电压比较器来实现正弦波到方波的变换。R1200R2200+C1+C2+5GND6。图2正弦波发生及波形变换电路（3）单稳态定时电路为了便于测量换算，设计一个1S定时电路，在该定时范围内所测得的脉冲个数即为振荡频率。定时电路及单稳态输出波形如图3所示。图31s定时电路7用555定时器构成单稳态定时电路，Tw=1.1RC=1.1*0.47*2=1.034≈1s，式中R和C为定式电阻和电容。在电路中加入由Cr和R1组成的微分电路，这样单稳态电路只要靠输入的下降沿触发（4）频率计数显示电路计数器选用MC14553芯片，这是一片3位BCD加法计数器芯片，由选择端1DS、2DS、3DS控制每一时刻只输出一位BCD码。显示译码器选用CD4511芯片，该芯片具有BCD七段锁存/译码/驱动功能。计数及译码显示电路如图4所示。8图4计数及译码显示电路（5）超量程指示电路当计数器MC14553计到1000个脉冲时，“OF”端会输出一个正脉冲，该信号连到超量程指示电路，驱动发光管发光，表示信号频率超范围需调整。超量程指示电路如图5所示。图5超量程指示电路（6）控制电路控制电路实际上是一低频信号发生器，振荡周期为4S，精度要求不高，用其产生方波和尖脉冲信号，分别用来触发单稳态电路、超量程指示电路复位和计数器清零。电路如图6所示。9图6控制电路（C）完整电路图图7完整电路10四、安装与调试（a）使用仪器仪表主要仪器为：数字电路试验箱（提供+5V电源），示波器，万用表（b）中规模器件的管脚图及功能表（1）7411和5为偏置(调零端)，2为正向输入端，3为反向输入端，4接地，6为输出，7接电源8空脚（2）555定时器1地GND2触发3输出4复位5控制电压6门限(阈值）7放电8电源电压Vcc11（3）CD4511BI：4脚是消隐输入控制端，当BI=0时，不管其它输入端状态如何，七段数码管均处于熄灭（消隐）状态，不显示数字。LT：3脚是测试输入端，当BI=1，LT=0时，译码输出全为1，不管输入DCBA状态如何，七段均发亮，显示“8”。它主要用来检测数码管是否损坏。LE：锁定控制端，当LE=0时，允许译码输出。LE=1时译码器是锁定保持状态，译码器输出被保持在LE=0时的数值。A1、A2、A3、A4、：8421BCD码输入端。a、b、c、d、e、f、g：为译码输出端，输出为高电平1有效。CD4511的内部有上拉电阻，在输入端与数码管笔段端接上限流电阻就可工作（4）CD400112（5）共阴极数码管（6）MC14553CLOCK：计数脉冲输入端，下调沿有效。CIA、CIB：内部振荡器的外界电容端子。MR：计数器清零（只清计数器部分），高电平有效。LE：锁定允许。当该端为低电平时，3组计数器的内容分别进入3组锁存器，当该端为高电平时，锁存器锁定，计数器的值不能进入。DIS：该端接地时，计数脉冲才能进行计数。DS1、DS2、DS3：位选通扫描信号的输出，这3端能循环地输出低电平，供显示器作为位通控制。Q0、Q1、Q2、Q3：BCD码输出端，它能分时轮流输出3组锁存器的BCD码。13（c）总管脚图（d）安装（1）首先在四连面包板上布好电源线，每块板上正下负，由于存在模拟电路，将其中一块板的负极接0电势点，不接电源负极。（2）规划个面包板，并按照总管脚图，依次在面包板相应位置连接好单元电路，力保准确、无误，接口连接良好。（3）测试每一部分单元电路。（4）单元电路测试无误后，将单元电路中的连线安装好，再依TRIG2Q3R4CVolt5THR6DIS7VCC8GND1U1CA555ENC8VCC7OUTPUT6OFFSET5VEE4IN+3IN-2OFFSET1U2741NC8VCC7OUTPUT6OFFSET5VEE4IN+3IN-2OFFSET1U3741DS2'1DS1'2CIB3CIA4Q35Q26Q17VSS8VDD16DS3'15OF14MR13CLK12DIS11LE10Q09U414553A1B2J3K4C5D6VSS7VDD14H13G12M11L10F9E8U6400110g9f8GND7a6b5h4C3GND2d1eU7LED10g9f8GND7a6b5h4C3GND2d1eU8LED10g9f8GND7a6b5h4C3GND2d1eU9LEDQ1PNP1Q2PNP1Q3PNP1Q4NPND1DIODESCHOTTKYBT1+5VR14R13R157*200R12R10R9R20R21RES2R81KR710K1200R2200R32KR610kR162MR1791KR1922MR1822MR11R23RES2R24RES2C30.1uC40.1uC747uC50.01uC6C80.1uC9+C147u+C247uGNDGNDD2R450KR550KGNDGNDVDD16f15g14a13b12c11d10e9B1C2BI'4LE5D6A7GND8LT'3R334511R22RES2C100.01uF14次测试。（见测试章节）(e)测试（1）正弦波电路测试电路要产生正弦波需满足起振条件和幅值条件Au=(1+Rf/R1)=3，即Rf=2R1=4kΩ，调节电位器Rf使之略大于4kΩ；RC桥式电路中应调节电位器R2，使R2=R=10kΩ。1、首先将两个电位计调至4.5KΩ及10KΩ2、连接电源，并将正弦波信号接入示波器3、观察波形，轻微调节Rf，使波形大小适宜，没有失真4、调节示波器幅值及频率档，使波形易于观察调节出的波形如图：（2）正弦波与波形变换电路测试由于正弦波本就与波形变换电路连接在一起只需将输入示波器的波形变换一下即可，输出方波如图：15（3）控制电路测试控制电路连接好后无需其他操作，只要将uib输入示波器即可。由于控制电路周期为4s，频率仅0.25Hz，因此将示波器时间调节为2.5s，输出为缓慢经过的扫描信号，如图：（4）控制电路与单稳态定时电路测试将控制电路输出Uib输入单稳态，将单稳态输出接至示波器，示波器人输出缓慢行进的扫描信号，如图：16（5）电路整体测试其余模块需要前面模块的信号才能测试，因此，前边测试无误后，便是模块整体测试了。将Uo