五邑大学本科毕业设计
摘 要
本论文从国际电子称重技术的发展及市场竞争的需要出发，展望了21世纪初电子称重技术的发展趋势与技术，提出了电子称重系统的设计方案，并完成了电子称重系统的硬件及软件设计。该系统以AT89S51单片机为核心，外围电路包含电压信号放大电路、A/D转换电路和键盘/显示单元等几个功能模块。称重系统的工作过程是：系统的前端为压敏式压力传感器采集重量产生的电压模拟信号，将该信号经放大、滤波后，由ADC0809实现数模转换，转换后数字信号进入AT89S51单片机，系统软件进行运算处理后，由数码管进行动态显示，实现对压力的称重控制。
本文提出的一种基于AT89S51单片机控制的新型电子称重系统,该系统具有体积小、重量轻、精度高、在没有交流电的场合进行测重方便、可靠。
关键词 电子称重技术；传感器；A/D转换器；51单片机
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五邑大学本科毕业设计
Abstract
From the international electronic weighing technology development and the needs of market competition, this thesis looked to the early 21st century electronic weighing technology development trends and technology, bring forward the electronic weighing system design, and completed the hardware and software design of electronic weighing system. The system use AT89S51 single-chip micro-computer as the core, containing the external circuit voltage signal amplifier, A / D converter circuit and keyboard display unit, and several other modules as well. the process of weighing system is: The front part of the system is for pressure-sensitive pressure sensor acquisition weight of the voltage analog signal, after amplification and filtering the signal and achieving D\\A conversion by the ADC0809, converted digital signals being put into AT89S51 SCM ,after the processing of System software, numerical code tube displays the dynamic digital, and controls the pressure weighing.
This thesis presents a new electronic weighing system base on AT89S51 MCU, which is small, light, high precision, it is convenient and reliable to measure weight in the absence of AC occasions.
Keyword Electronic weighing technology Transducer A/D converter single-chip micro-computer
II
五邑大学本科毕业设计
目 录
摘要 ·················································································································································· I Abstract ·········································································································································· II
第1章 绪论 ································································································································· 1
1.1课题背景 ···························································································································· 1 1.2国内外电子称重技术的发展 ···························································································· 1 1.3电子称重系统中相关概述 ································································································ 3 1.4本课题的主要研究目标及内容 ························································································ 4 1.5本章小结 ···························································································································· 4 第2章 系统的硬件设计 ··············································································································· 5
2.1总体设计 ···························································································································· 5
2.2传感器的工作原理及其仿真分析 ···················································································· 5
2.2.1工作原理 ·················································································································· 5 2.2.2传感器的仿真分析 ·································································································· 7 2.3放大电路模块 ···················································································································· 8 2.4放大芯片LM358 ············································································································· 11 2.4.1 LM358的概述 ······································································································· 11
2.4.2 LM358特性 ··········································································································· 11 2.4.3 LM358的原理 ······································································································· 12 2.5 ADC0809转换器 ············································································································· 13
2.5.1转换器芯片ADC0809简介 ················································································· 14 2.5.2信号引脚 ················································································································ 15 2.5.3 MCS-51单片机与ADC0809的接口 ··································································· 16 2.5.4 转换数据的传送 ··································································································· 17 2.6 MCS—51单片机 ············································································································ 19 2.6.1 MCS—51单片机芯片概述 ·················································································· 19
2.6.2 MCS—51单片机内部结构与工作原理 ······························································ 19 2.7 LED数码管结构 ············································································································· 23 2.8整体的PROTEL电路图 ································································································· 24 2.9 本章小结 ························································································································· 24 第3章 系统软件设计 ················································································································· 25
3.1软件的总体设计 ·············································································································· 25 3.2系统的主程序 ·················································································································· 26 3.3相关的子程序 ·················································································································· 27 3.4本章小结 ·························································································································· 29 第4章 系统调试与总结 ············································································································· 30
III
五邑大学本科毕业设计
4.1 PCB的绘制和制板过程 ······························································································ 30 4.2 硬件电路调试 ················································································································· 31 4.3 软件调试 ························································································································· 31 4.4 软、硬件总体调试 ········································································································· 31 4.5体会 ·································································································································· 32
结论 ··············································································································································· 33 致谢 ··············································································································································· 34 参考文献 ······································································································································· 35 附录1 ········································································································································ 36 附录2 ········································································································································ 38 附录3 ········································································································································ 40
IV
五邑大学本科毕业设计
第1章 绪论
1.1课题背景
电子称重技术是现代称重计量和控制系统工程的基础之一自50年代中期电子技术渗人到衡器助测量装置，印年代初期出现机电结合式电子衡来，经过40多年的不断改进与完善，电子衡器从的机电结合型发展到现在的全电子型和数字化智：由于它具有称量准确、快速，读数方便，环境适强，便于与电子计算机结合而实现称重计量自动化等特点，在工商贸易、能源交通、冶金矿工食品、医药卫生、航空航天等部门得到了广泛用。
近年来，随着计算机和称重传感器技术的迅速发展，现代科学技术的相互渗透，电子称重技术及应用又有了新发展。称重技术从静态称重向动态称重发展；计量方法从模拟测量向数字测量发展；测量特点从单参数测量向多参数测量发展特别是对快速称重和动态称重的研究与应用，已为世界各国所关注。可以说电子称重技术的发展水平，已成为衡量一个国家科学技术水平和工业发达程度的重要标志之一。
电子称重技术是集机械、电子、材料、信息、管理为一体的综合技术，是一项系统工程。各工业发达国家长期以来，都把电子称重技术的研究及应用提高到电子称重设备制造工程的高度来认识。它们不约而同的将研究开发的重点，从单纯的称重转移到生产过程的称重系统和自动控制领域，使称重计量的内涵不断扩展，由狭义到广义，由单项到系统，新型的现代称重计量概念已脱颖而出，一跃成为当代世界瞩目的技术与行业。尽管80年代以来，我国衡器行业打破了部门和地区的界限，走上了按专业和产品归口的行业管理轨道，开创了由机械衡器向电子衡器过渡的新局面，电子衡器产品的数量和质量与工业发达国家相比还有较大差距，行业的总体水平还跟不上国家经济的发展步伐。因此，中国衡器协会在2010年长远规划中提出“到2010年电子衡器和称重传感器生产厂家的技术装备和检测试验手段要达到国际如年代中期的水平；到2010年要基本达到当代国际水平。”为配合完成这一规划，本论文就我国21世纪初电子称重技术的发展趋势与技术课题，电子衡器产品的发展动向，谈些浅薄看法，并提出了电子称重技术如何进人21世纪的问题供同行思考。
1.2国内外电子称重技术的发展
称量技术在近百年的历史中，大致经历了以下的四个发展阶段，约半个世纪的机械式的模拟式称量时代，接着进入了电气时代称量和电子称量时代，至七八十年代末期，全面进入了数字化称量及微机智能化称量的时代，至九十年代，开始进入模型化称量的新时代。不仅要求取得称量的正确结果，而且要求对称量结果的状态趋势进行估计，对动态变化中的量进行实时称量。这种要求仅仅依靠传统的称量方法和数据处理的方法已经不可能实现的，只有模型化称量才能为日趋复杂的动态称量问题开辟一条新的路径。国际上己经取得了动态精密称量的技术突破，称量技术已经跨入了高技术王国。把激烈的市场竞争由
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