电子称毕业设计 - 图文

I

南京工程学院自动化学院本科毕业设计（论文）

摘 要

该设计以51系列单片机AT89S52为控制核心，实现电子秤的基本控制功能。在设计系统时，为了更好地采用模块化设计法，分步的设计各个单元功能模块，系统的硬件部分可以分为最小系统、数据采集、人机交互界面和系统电源四大部分。最小系统部分主要包括AT89S52和扩展的外部数据存储器；数据采集部分由压力传感器、信号的前级处理和A/D转换部分组成，包括运算放大器AD620和A/D转换器ICL7135；人机交互界面为键盘输入和点阵式液晶显示，主要使用ZLG7289键盘控制芯片和OCM4x8C显示器，可以方便的输入数据和直观的显示中文。系统电源以LM317和LM337为核心设计电路以提供系统正常工作电源。软件部分应用单片机C语言进行编程，实现了该设计的全部控制功能。该电子秤可以实现基本的称重功能（称重范围为0～9.999Kg，重量误差不大于±0.005Kg）,并发挥部分的显示购物清单的功能，可以设置日期和设定十种商品的单价， 还具有超量程和欠量程的报警功能。整个系统结构简单，使用方便，功能齐全，精度高，具有一定的开发价值。

关键词：单片机；采样电路；A/D转换器；液晶显示

I

南京工程学院自动化学院本科毕业设计（论文）

ABSTRACT

The design is based on the microcontroller AT89S52 system as the core to carry out the basic control function of the electronics steelyard. While designing the system, I adopt the mold piece method to divide the hardware of the system into four parts: the minimum system, sampling circuit, I/O interface and the system power supply. The minimum system mainly includes the AT89S52 and the expanded exterior data memory. Sampling circuit is comprised of a pressure sensor, a differential measuring amplifier AD620 and a A/D converter ICL7135. With the usage of ZLG7289 keyboard control chip and OCM4*8C display, we complete the function of the key board input and the LCD manifestation. The power supply system selects the LM317 and LM337 to design the electric circuit to provide the needed power supply. The software part applies a machine C language to carry out all control function. The electronic steelyard can weigh the scope as 0～9.999Kgs, and the weigh error margin is no bigger than ±0.005Kgs. It also has many other functions, such as displaying the shopping detailed list, setting the date and ten kinds of unit prices of merchandise and overweighing alarm. The whole system is simple, well-found, convenient to use and has high accuracy and certain development value.

Key words： microcontroller; sampling circuit; A/D converter;

LCD Manifestation

目 录

II

南京工程学院自动化学院本科毕业设计（论文）

第一章 绪论 .............................................................................................. 1

1.1 引言 .................................................................................................................. 1

1.2选题背景与意义 ............................................................................................... 2

1.3 研究现状 .......................................................................................................... 2

1.3.1 影响因素 ................................................................................................. 2 1.3.2产品质量 .................................................................................................. 3

1.3.3发展方向 .................................................................................................. 3 1.3.4电子秤的智能化 ...................................................................................... 3 1.4 本文的结构 ...................................................................................................... 4

第二章 系统方案的设计 ......................................................................... 5 2.1 电子秤的设计要求 .......................................................................................... 5

2.1.1 基本要求 ................................................................................................. 5 2.1.2 发挥部分 ................................................................................................. 5 2.1.3 创新部分 ................................................................................................. 5 2.2 系统工作原理及设计基本思路 ...................................................................... 5 2.2.1 系统工作原理 ......................................................................................... 5 2.2.2 系统设计基本思路 ................................................................................. 6 2.3 系统总体设计方案比较与论证 ...................................................................... 6 2.4 单片机的选型 .................................................................................................. 8 2.5 数据采集部分的方案确定 .............................................................................. 9

2.5.1 传感器 ..................................................................................................... 9 2.5.2 前级放大器部分 ................................................................................... 12 2.5.3 A/D转换器 ............................................................................................ 15 2.6 人机交互部分 ................................................................................................ 17 2.6.1 键盘输入 ............................................................................................... 17 2.6.2 输出显示 ............................................................................................... 17 2.7 系统电源 ........................................................................................................ 18 2.8 具体实施方案简介 ........................................................................................ 20

第三章 系统硬件设计 ........................................................................... 22 3.1 基于AT89S52的主控电路 ........................................................................... 22

3.1.1 芯片介绍 ............................................................................................... 22 3.1.2 主控电路 ............................................................................................... 26 3.2 基于ICL7135的前端信号处理电路 ........................................................... 27 3.2.1 芯片介绍 ............................................................................................... 27

III

南京工程学院自动化学院本科毕业设计（论文）

3.2.2 信号处理电路 ....................................................................................... 30 3.3 人机交互界面 ................................................................................................ 33 3.3.1 键盘控制电路 ....................................................................................... 33 3.3.2 液晶显示电路 ....................................................................................... 35 3.4 系统电源 ........................................................................................................ 37 3.4.1 芯片介绍 ............................................................................................... 37 3.4.2 电源电路 ............................................................................................... 38 3.5 报警电路 ........................................................................................................ 40

第四章 软件流程 .................................................................................... 41 4.1 主程序流程图 ................................................................................................ 41 4.2 主要中断程序流程图 .................................................................................... 42 第五章 结论 ............................................................................................ 44 致谢 ............................................................................................................ 46 参考文献 ..................................................................................................... 47

附录A：英文资料 ..................................................................................................... 48 附录B：英文资料翻译 ............................................................................................. 55 附录C：原理图 ......................................................................................................... 62 附录D：Pcb板图 ...................................................................................................... 63 附录E：元器件清单 ................................................................................................. 64

IV

百度搜索“77cn”或“免费范文网”即可找到本站免费阅读全部范文。收藏本站方便下次阅读，免费范文网，提供经典小说综合文库电子称毕业设计 - 图文在线全文阅读。