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1、摘 要目前，随着电子工业的发展，电子元器件急剧增加，电子元器件的适用范围也逐渐广泛起来，在应用中我们常常要测定电容的大小。在电子产品的生产和维修中，电容测量这一环节至关重要，因此，设计可靠，安全，便捷的电容测试仪具有极大的现实必要性。本文提出了以 MCS-51 单片机为控制核心，结合多谐振荡器来实现电容测量的方法。并介绍了测量原理并给出了相应的电路及软件设计。关键词：电容测试仪；单片机；测量目录1 概述 11.1 设计目的和意义.1 1.2 设计任务与要求.1 2 硬件电路设计及其描述1 2.1 设计方案 .1 2.2 原理框图.2 2.3 基于 AT89C51 电容测量系统硬件设计详细分析.
2、2 2.3.1 AT89C51单片机工作电路.2 2.3.2 基于 AT89C51电容测量系统复位电路.3 2.3.3 基于 AT89C51电容测量系统时钟电路.4 2.3.4 基于 AT89C51电容测量系统按键电路.4 2.3.5 基于 AT89C51电容测量系统555芯片电路.5 2.3.6 基于 AT89C51电容测量系统显示电路.6 2.4 各部分电路连接成整个电路图.9 2.5 系统所用元器件.10 2.6 PCB制图.11 3 软件流程及程序设计 .11 3.1 系统模块层次结构图11 3.2 程序设计算法设计.12 3.3 软件设计流程 .13 3.4 源程序代码 13 4 系
3、统调试及仿真 .17 5 总结.18 5.1 本系统存在的问题及改进措施.18 5.2 心得体会 .18 参考文献 .19 文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9
4、R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:
5、CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2
6、HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 Z
7、S9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编
8、码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U
9、2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H81/20 1 设计任务1.1 设计目的和意义目前，随着电子工业的发展，电子元器件急剧增加，电子元器件的适用范围也逐渐广泛起来，在应用中我们常
10、常要测定电容的大小。在电子产品的生产和维修中，电容测量这一环节至关重要，一个好的电子产品应具备一定规格年限的使用寿命。因此在生产这一环节中，对其产品的检测至关重要，而检测电子产品是否符合出产要求的关键在于检测其内部核心的电路，电路的好坏决定了电子产品的好与坏，而电容在基本的电子产品的集成电路部分有着其不可替代的作用。同样，在维修人员在对电子产品的维修中，电路的检测是最基本的，有时需要检测电路中各个部件是否工作正常，电容器是否工作正常。因此，设计可靠，安全，便捷的电容测试仪具有极大的现实必要性。1.2 设计任务与要求1）采用 MCS-51系列单片机以及多谐振荡器进行电容测量仪设计；2）能测试 0
11、.10.99UF的电容，其精确度为 0.01UF。3）用2行16个字的 LCD1602显示测量结果。2 基于单片机电容测量硬件设计2.1 设计方案本设计选择基于 AT89C51单片机和 555芯片构成的多谐振荡电路的电容测量方法。这种电容测量方法主要是通过一块555芯片来测量电容，让 555芯片工作在直接反馈无稳态的状态下，555芯片输出一定频率的方波，其频率的大小跟被测量的电容之间的关系是：f=0.772/R*Cx），我们固定R 的大小，其公式就可以写为：f=k/Cx，只要我们能够测量出 555芯片输出的频率，就可以计算出测量的电容。计算频率的方法可以利用单片机的计数器T0和中断 INT0，
12、配合使用来测量，系统框图见图1所示。图中给出了整个系统设计的系统框图，系统主要由四个主要部分组成：单片机和晶振电路设计、555芯片电路设计、显示电路设计、复位电路设计。2.2原理框图文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码
13、:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2
14、 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9
15、ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档
16、编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10
17、U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A
18、9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H82/20 2.3 基于 AT89C51电容测量系统硬件设计详细分析2.3.1 AT
19、89C51 单片机工作电路单片机电路是本设计的核心部分，本设计选用了常用的AT89C51 单片机。AT89C51 是低功耗、高性能、经济的8位CMOS微处理器，工作频率为024MHz，内置 4K字节可编程只读闪存，128x8位的内部 RAM，16位可编程 I O总线。AT89C51 工作的最简单的电路是其外围接一个晶振和一个复位电路，给单片机接上电源和地，单片机就可以工作了。其最简单的工作原理图如图2所示。图2工作原理图2.3.2基于 AT89C51 电容测量系统复位电路MCS-51的复位是由外部的复位电路来实现的。MCS-51单片机片内复位，复位引脚RST通过一个斯密特触发器用来抑制噪声，在
20、每个机器周期的 S5P2，斯密特触发器的输出电平由复位电路采样一次，然后才能得到内部复位操作所需要的信号。本设计采用按键手动脉冲复位方式，按键脉冲复位是利用RC微分电路产生的正脉冲来实现的。复位电路如图 3所示。文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9
21、ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档
22、编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10
23、U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A
24、9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8
25、文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N
26、10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H83/20 图3复位电路一般的，单片机的复位速度比外围
27、I/O快些。若 RC上电复位电路接 MCS-51单片机和外围电路复位端，则能使系统可靠地同步复位。为保证系统可靠复位，在初始化程序中应用到一定的复位延迟时间。复位电路软件程序或者硬件发生错误的时候产生一个复位信号，控制MCS-51单片机从 0000H单元开始执行程序，重新执行软件程序。此电路的输出端RESET接在单片机的复位引脚。2.3.3 基于 AT89C51电容测量系统时钟电路时钟在单片机中非常重要，单片机各功能部件的运行都是以时钟频率为基准。时钟频率直接影响单片机的速度，时钟电路的质量也直接影响单片机系统的稳定性。常用的时钟电路有两种方式，一种是内部时钟方式，另一种为外部时钟方式。本设计
28、使用内部时钟方式，其内部时钟方式电路图如图4 所示。图4内部时钟方式电路图 MCS-51 单片机内部有一个用与构成振荡器的高增益反相放大器，该高增益反相放大器的输入端为芯片引脚XTAL1，输出端为引脚 XTAL2。这两个引脚接石英晶体振荡器和微调电容，就构成一个稳定的自激振荡器电路。文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1
29、L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR
30、5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR
31、2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9
32、R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:
33、CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2
34、HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 Z
35、S9R1L1G3H84/20 电路中的电容 C1和 C2典型值通常选择为30PF左右。对外接电容的值虽然没有严格的要求，但是电容的大小会影响振荡器频率的高低、振荡器的稳定性和起振的快速性。晶体的振荡频率的范围通常是在1.2MHz12MHz之间。很设计中单片机选择12MHz的石英晶体。2.3.4 基于 AT89C51电容测量系统按键电路按键是实现人机对话的比较直观的接口，可以通过按键实现人们想让单片机做的不同的工作。键盘是一组按键的集合，键是一种常开型开关，平时按键的两个触点处于断开状态，按下键是它们闭合。图5就是一种比较典型的按键电路，在按键没有按下的时候，输出的是高电平，当按键按下去的时候，
36、输出的低电平。图5按键电路2.3.5 基于 AT89C51电容测量系统 555 芯片电路对于555电路等效看成一个带放电开关的RS触发器，这个特殊的触发器有两个输入端：阈值端 TH可看成是置零端 R，要求高电平，触发端 R可看成置位端低电平有效。它只有一个输出端 Vo，Vo可等效为触发器的 Q端。放电端 DIS可看成由内部放电开关控制的一个接点，放电开关由触发器的端控制：Q=1时DIS端接地；Q=0时，DIS端悬空。此外，这个触发器还有复位端MR加上低电平(时可使输出为低电平。该特殊的RS触发器有两个输入端，这两个输入端的触发电平要求一高一低，其中置零端R即阈值端TH要求高电平，置位端即触发端
37、则要求低电平，也就是使它们翻转的阈值电压值不同。当 VK 端不接控制电压时，对 TH端(即R端来讲，大于 23VDD是高电平 1，小于 23VDD时是低电平 0；而对 TR端(即端来讲，大于 13VDD是高电平 1，小于 13VDD是低电平 O。55芯片电路的应用电路很多，本次设计应用直接反馈型无稳类电路。电路如图6所示。文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10
38、U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A
39、9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8
40、文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N
41、10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A
42、7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3
43、H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F
44、2N10U2 HR2M9S9A7A9 ZS9R1L1G3H85/20 图 6 555 产生方波电路555芯片芯片输出的频率为 f=0.772/(R*C，只要我们改变电阻 R，就可以达到改变电阻量程的目的，本设计提供了一组电阻，所以说有电容测量量程为。在555芯片输出方波后，由于硬件的原因，输出的方波会有很多毛刺，为了去除这些毛刺本设计中使用了一个两输入与门74HC08），让信号通过 74HC08后会使输出的波形毛刺减少很多，使单片机的测量结果变得精确。74HC08如图7所示。图774HC082.3.6 基于 AT89C51电容测量系统显示电路本设计使用的是 2行16个字的 1602液晶模块作为
45、测量值显示部分。其中字符型液晶模块是一种用 5x7点阵图形来显示字符的液晶显示器，根据显示的容量可以分为1行16个字、2行16个字、2行20个字等等。如图 8为LCD1602引脚图。文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码
46、:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2
47、 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9
48、ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档
49、编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10
50、U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A9 ZS9R1L1G3H8文档编码:CR5X4F2N10U2 HR2M9S9A7A