单片机电子称控制系统的设计

I电子称单片机控制系统的设计I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IIABSTRACTThedesignisbasedonthemicrocontrollerAT89S52systemasthecoretocarryoutthebasiccontrolfunctionoftheelectronicssteelyard.Whiledesigningthesystem,Iadoptthemoldpiecemethodtodividethehardwareofthesystemintofourparts:theminimumsystem,samplingcircuit,I/Ointerfaceandthesystempowersupply.TheminimumsystemmainlyincludestheAT89S52andtheexpandedexteriordatamemory.Samplingcircuitiscomprisedofapressuresensor,adifferentialmeasuringamplifierAD620andaA/DconverterICL7135.WiththeusageofZLG7289keyboardcontrolchipandOCM4*8Cdisplay,wecompletethefunctionofthekeyboardinputandtheLCDmanifestation.ThepowersupplysystemselectstheLM317andLM337todesigntheelectriccircuittoprovidetheneededpowersupply.ThesoftwarepartappliesamachineClanguagetocarryoutallcontrolfunction.Theelectronicsteelyardcanweighthescopeas0～9.999Kgs,andtheweigherrormarginisnobiggerthan±0.005Kgs.Italsohasmanyotherfunctions,suchasdisplayingtheshoppingdetailedlist,settingthedateandtenkindsofunitpricesofmerchandiseandoverweighingalarm.Thewholesystemissimple,well-found,convenienttouseandhashighaccuracyandcertaindevelopmentvalue.Keywords：microcontroller;samplingcircuit;A/Dconverter;LCDManifestationIII目录第一章绪论..............................................................................................11.1引言..................................................................................................................11.2选题背景与意义...............................................................................................21.3研究现状..........................................................................................................21.3.1影响因素.................................................................................................21.3.2产品质量..................................................................................................31.3.3发展方向..................................................................................................31.3.4电子秤的智能化......................................................................................31.4本文的结构......................................................................................................4第二章系统方案的设计.........................................................................52.1电子秤的设计要求..........................................................................................52.1.1基本要求.................................................................................................52.1.2发挥部分.................................................................................................52.1.3创新部分.................................................................................................52.2系统工作原理及设计基本思路......................................................................52.2.1系统工作原理.........................................................................................52.2.2系统设计基本思路.................................................................................62.3系统总体设计方案比较与论证......................................................................62.4单片机的选型..................................................................................................82.5数据采集部分的方案确定..............................................................................92.5.1传感器.....................................................................................................92.5.2前级放大器部分...................................................................................122.5.3A/D转换器............................................................................................152.6人机交互部分................................................................................................172.6.1键盘输入...............................................................................................172.6.2输出显示...............................................................................................172.7系统电源........................................................................................................182.8具体实施方案简介........................................................................................20第三章系统硬件设计...........................................................................223.1基于AT89S52的主控电路...........................................................................223.1.1芯片介绍...............................................................................................22IV3.1.2主控电路...............................................................................................263.2基于ICL7135的前端信号处理电路................................