本 科 毕 业 论 文
论文题目 数字电子秤 学生姓名 学 号
专 业 电子信息科学与技术 班 级 指导教师
2010年5月
摘 要
摘 要
本文用单片机设计了一个数字电子秤，并给出了设计框图、硬件组成及软件系统。本系统以51单片机最小系统为核心，主要的部件有24位专用串行A/D转换芯片HX711、悬臂梁式电阻应变传感器，输出采用4位数码管显示。系统通过传感器将压力转化为微弱电信号，即电阻应变片感应到压力后，电阻发生微小变化。通过全桥测量电路将电阻的微小变化转化成电压的微小变化，再经过24位专用串行A/D转换芯片HX711将微小的电压信号转换为24位的串行数字信号输入到单片机进行处理，最后输出到数码管上显示。本设计采用的24位专用串行A/D转换芯片HX711，具有分辨率高，占用I/O口少，与外设接口简单等优点。
关 键 词：数字电子秤；应变片式电阻传感器；HX711；单片机
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咸宁学院学士学位论文
ABSTRACT
It designed a digital electronic scale by using the single chip computer, which included the frame drawing, hardware structure and software system. It based on 51 microcomputer system and included other models, such as dedicated A/D converter chip HX711 and cantilever-type resistance strain sensor. The output was displayed by four-bit digital tube. This paper conveted the pressure into weak signal. That is when the pressure was induced by the resistance strain gauge sensor, small changes in resistance occurred . It would be converted to voltage with full-bridge measurement circuit. Then the 24 special serial A/D converting chip HX711 converted the small changes in voltage into 24-bit serial digital signals, SCM processed the signals, lastly the digital tube displayed the output. HX711 is special for A/D converter, moreover it has high resolution and occupys less I/O ports. Importantly its interfacing with peripheral circuits is simple.
KEY WORDS: Digital electronic scale; Resistance strain gauge sensor; HX711; Single chip computer
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目 录
目 录
1 绪论 ...................................................................................................................................... 1 2 系统组成及工作原理 .......................................................................................................... 3 2.1 系统的组成 ................................................................................................................... 3 2.2 系统的工作原理 ........................................................................................................... 3 3 系统硬件设计 ...................................................................................................................... 5 3.1 主控芯片STC89C52单片机基本系统 ....................................................................... 5 3.1.1 STC89C52单片机性能介绍 .................................................................................. 5 3.1.2 STC89C52单片机引脚功能 .................................................................................. 5 3.1.3 复位电路 ................................................................................................................ 6 3.1.4 晶振电路 ................................................................................................................ 7 3.2 A/D转换芯片HX711接口电路的设计 ....................................................................... 7 3.2.1 HX711引脚功能 .................................................................................................... 8 3.2.2 HX711管脚说明 .................................................................................................... 8 3.3 压电传感器的设计 ..................................................................................................... 12 3.3.1 应变片式电阻传感器 .......................................................................................... 12 3.3.2 应变片式电阻传感器的结构和原理 .................................................................. 12 3.3.3 全桥测量电路 ...................................................................................................... 13 3.4 LED显示电路的设计 ................................................................................................. 14 4 系统软件设计 .................................................................................................................... 17 4.1 系统主函数 ................................................................................................................. 17 4.2 A/D数据采集子函数 .................................................................................................. 17 4.3 数码管显示子函数 ..................................................................................................... 18 5 系统测试及定标 ................................................................................................................ 19 5.1 系统硬件测试 ............................................................................................................. 19 5.2 线性度的确定 ............................................................................................................. 19 5.2.1 未定标时数码管显示值 ...................................................................................... 19 5.2.2 定标后数码管显示值 .......................................................................................... 19 5.2.3 误差分析 .............................................................................................................. 19 6 总结 .................................................................................................................................... 23 致 谢 .................................................................................................................................... 25 参考文献 ................................................................................................................................ 27
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