高精度数控恒流源

梧州学院I摘要本文介绍了一种开环智能数控直流电流源的设计原理和实施方案，该方案采用D/A（MAX531）转换器、运算放大器等器件来控制场效应管导通状态的原理，达到了输出恒流的目的。整个系统采用AT89S52单片机作为主控部件，将预置电流值数据送入D/A转换器（MAX531），经硬件电路变换为恒定的直流输出，同时采用基本没有温度漂移的康锰铜电阻丝作为精密采样电阻。采用性能优于普通晶体管的场效应管作为恒流源的主要部件，大功率晶体管作为扩流电路的主要器件，结合三端稳压管和多层滤波使得整个系统性能提升了一个层次，从而实现了高精度恒流源的目的。系统还对输出电压进行实时采样，通过A/D转换器采样回单片机与用户给定的限压值进行比较，从而监控了输出电压。同时通过键盘的控制,实现了输出电流值和限压值可预置，可步进调整、输出的电流信号和电压信号可直接数字显示的功能，并具有输出电压实时监控限压报警并自动降低输出电流等功能。与以往的直流恒流源相比，此次所设计的恒流源具有精度高、结构简单、工作稳定、操作方便、成本低廉、带负载能力强等优点。关键词：恒流源AT89S52单片机MAX531MAX187梧州学院IIAbstractThispaperintroducesasmartNCopen-loopDCcurrentsourcedesignprincipleandtheimplementationoftheprogramme,usingtheD/A(MAX531)converters,opamp,andotherdevicestocontrolFETon-stateprinciple,theoutputreachedconstantcurrentpurposes.AT89S52theentiresystemusesasingle-chipmicrocomputercontrolcomponents,preferencescurrentvaluedatawillbesenttotheD/Aconverters(MAX531),thehardwarecircuitfortheconstanttransformationofDCoutput,butnotusingthebasictemperaturedriftConcordManganinresistorSilkasasophisticatedsamplingresistor.PerformanceisbetterthantheordinaryuseoftheFETtransistorasaconstantcurrentsourceofmajorcomponents,high-powertransistorsasexpandingthemaincircuitdevice,thecombinationofthree-terminalregulatorsandthemulti-filtermakesthewholesystemaperformanceboostlevelstoachieveahigh-precisionconstantcurrentsourcepurposes.Outputvoltageofthesystemtoconductreal-timesampling,throughtheA/DconverterswithsamplingtoMCUuserstosetlimitvaluestocomparepressuretocontroltheoutputvoltage.Atthesametime,thekeyboardcontrolandrealizedthevalueofoutputcurrentandvoltage-limitingvaluescanbepreset,steppingadjustment,thecurrentsignalandtheoutputvoltagesignalcanbedirectlyfiguresshowthatthefunction,andreal-timemonitoringoftheoutputvoltage,suchasover-voltagealarmfunction.InthepastcomparedtoDCcurrentsource,thedesignofahigh-precisionconstantcurrentsource,simplestructureandworkstability,andeasytooperate,lowcost,withapayloadcapacity,andotheradvantages.Keywords:CurrentsourceAT89S52MCUMAX531MAX187梧州学院III目录摘要............................................................I前言............................................................1第一章系统结构及功能介绍.......................................21.1系统工作原理概述..........................................21.2系统的特点和使用..........................................21.2.1系统的特点............................................21.2.2系统的使用说明........................................3第二章设计方案.................................................42.1方案比较..................................................42.1.1整体方案...............................................42.1.1.1方案一..............................................42.1.1.2方案二..............................................52.1.1.3方案三..............................................52.1.2恒流源方案.............................................62.1.2.1方案一.............................................62.1.2.2方案二.............................................62.1.2.3方案三.............................................72.2最终选用方案..............................................7第三章硬件系统设计.............................................83.1系统硬件基本组成..........................................83.2各模块单元电路设计.......................................83.2.1电源电路..............................................83.2.2扩流电路..............................................93.2.2.1电路的优点.......................................93.2.2.2电路工作原理...................................103.2.3恒流电路.............................................103.2.4采样电路.............................................113.3系统主要芯片介绍.........................................123.3.1AT89S52单片机.......................................123.3.2MAX531..............................................123.3.3MAX187..............................................133.3.4AT24C16.............................................14第四章软件设计................................................18梧州学院IV4.1概述.....................................................184.2主程序结构...............................................184.3各模块子程序设计原理.....................................204.3.1MAX531工作原理......................................204.3.2MAX187工作原理......................................204.3.2键盘扫描原理........................................214.3.3LCD12864显示.......................................22第五章系统调试................................................235.1硬件设计要点.............................................235.1.1共地问题.............................................235.1.2采样电阻选择.........................................235.1.3D/A及A/D电路处理...................................24第六章数据测试及分析..........................................256.1输出电流测试...........................................256.2步进电流测试...........................................266.3工作时间测试............................................276.4负载阻值变化测试........................................286.5输出电压值测试..........................................29第七章结束语..................................................31参考文献.......................................................32附录........................................................