基于CAN和RS485总线工业用可燃性气体报警系统

本科生毕业设计（论文）I摘要在炼油厂、加油站、化工厂等对可燃性气体浓度要求很高的场所，需要一款能准确检测可燃性气体浓度并报警的可燃性气体报警系统。本文首先对课题的来源和背景作了简单的介绍，并且分析了气体报警系统设计的目的和意义。其次对气体报警系统的工作原理、功能要求作了概述，并依据设计要求对气体报警系统进行了总体设计。系统采用CAN总线与RS485总线相结合的两级通讯网络，主控制器、CAN/485转换器、气体探测器和控制模块相结合的三层结构模式。气体探测器和控制模块相结合的最下层网络，利用气体传感器对各个区域的气体浓度进行检测并进行数据处理，通过CAN/485转换器传送到主控器，实现终端显示，报警，打印等功能。同时根据信号分析得到结论，对报警系统的可靠性进行了具体设计。硬件方面，首先采用了一些性能优良的新型器件对各种防干扰电路进行了设计，并考虑了电路的电磁兼容，比如各种滤波电路、隔离电路和防雷电路等；然后对控制器机箱外壳和通讯线路等进行了设计。软件设计中主要采用了数字滤波以及干扰避开法等防干扰措施。关键词：气体报警系统；电磁兼容；CAN/485；可靠性本科生毕业设计（论文）IIAbstractIt’sdemandinginmanyplaces,suchasoilrefinery,fillingstationandchemicalplant,soasystemwhichcantestthecombustiblegasisnecessary.First,itintroducesthesourceandbackgroundinthethesisandanalysisthepurposeofthesystem.Thenworkingprincipleandfunctionalrequirementsarepresented,andoveralldesigniscompletedbasedongasalarmsystem.It’susedCANbusandRS485bus,structuremodelhasthreelayerswhichincludescontroller,CAN/485convert,gasdetectorandcontrolmodule.Thebottomaregasdetectorandcontrolmodule.GassensorsareusedtotestthegasandthenthedatawillbedeliveredtothecontrollerthroughtheCAN/485.Terminalcancompletethedisplay,alarm,printandotherfunctions.Alarmsystemisdesignedbasedontheconclusionwhichisgotfromthesignalanalysis.Somenewdevicesareusedinthesystemtoreduceinterference.GiventheEMCofcircuit,suchasfiltercircuit,isolationcircuitandprotectioncircuit,chassisshellandcommunicationlinesaredesigned.Thesoftwaredesignmainlyadoptsdigitalfiltering,interferenceavoidingmethodandantiinterferencemeasures.Keywords：Combustiblegasalarm；ElectromagneticCompatibility,；CAN/485；eliability本科生毕业设计（论文）III目录第1章绪论............................................................................................................11.1论文研究来源、目的和意义...................................................................11.2可燃性气体报警器的国内外现状...........................................................21.3本设计主要任务.......................................................................................2第2章可燃性气体检测报警系统的方案设计....................................................42.1方案论证...................................................................................................42.2系统工作原理...........................................................................................42.3系统功能要求...........................................................................................42.4气体传感器的选型...................................................................................52.4.1气体传感器介绍............................................................................62.4.2可燃性气体传感器的选定............................................................72.5探测器设计.............................................................................................102.6系统总体设计.........................................................................................112.7CAN的通信模型.....................................................................................112.7.1数据链路层..................................................................................112.7.2物理层..........................................................................................12第3章可燃性气体报警系统的硬件设计..........................................................133.1探测器和控制模块.................................................................................133.1.1单片机的选择..............................................................................133.1.2信号采集及前置放大电路..........................................................143.1.3声光报警电路..............................................................................163.1.4报警器故障自诊断电路..............................................................163.1.5控制模块......................................................................................173.2CAN/485转换器......................................................................................183.2.1RS485接口电路............................................................................183.2.2CAN总线控制器..........................................................................193.2.3CAN收发器..................................................................................213.3主控器.....................................................................................................223.4系统供电电路.........................................................................................273.5报警系统的电磁兼容设计.....................................................................28本科生毕业设计（论文）IV3.5.1元器件的选择..............................................................................283.5.2电路的电磁兼容性设计..............................................................29第4章可燃性气体检测报警系统的软件设计..................................................324.1STC12系列单片机调试及开发工具......................................................324.2可燃性气体探测器软件流程及设计.....................................................324.2.1探测器主程序设计及流程图......................................................324.2.2主程序初始化流程图..................................................................334.2.3中位值平均滤波法数字滤波子程序设计及流程图..................344.2.4插值法线性化处理子程序流程图...................