designandimplementofaprogrammablelogiccontr

IntelligentControlandAutomation,2012,3,44-49()DesignandImplementofaProgrammableLogicController(PLC)forClassicalControlLaboratory*YousifI.AlMashhadanyElectricalEngineeringDepartment,CollegeofEngineering,UniversityofAnbar,Baghdad,IraqEmail:[e-mail]31,2011;revisedDecember1,2011;acceptedDecember9,2011ABSTRACTThedesignandimplementationofaclassicalcontrolsystemlaboratorybasedonPLCcontrolsystemisintroducedinthispaper.Todesignandimplementthesystem,twopartsmustbeproduced.ThefirstissoftwareforPLCandthesec-ondishardwareforexperimentsrelatedtotheprograms.ThePLCcontrolsystemusedinthedesignisLSindustrialsystemcompanyGM7-DR40A24/16DigitalI/OandsingleAnalogI/Omodule,twophotoelectricsensorsfromAtoniccompany’:thefirstwiththemodelBR100-DDT-P,andthesecondBEN10M-TFR.Anapproximatesensorwith5-sidesisdetected,fourofCMOSBCD-7-SegmentdrivenbyCD4511B,tworelays:2-polesand3-poles,sixvoltagesandanammetermeasurement,DCmotorand24VDCpowersupplyandmanyconnectersandpinions.SatisfactoryresultsareobtainedbyexecutingtwentyfourexperimentsforclassicalcontroltheorythatfulfilltherequirementsofcontroltheoryinundergraduatestageandreplacetheoldexperimentsexecutedbyPIDcontrollerwherethepracticesystemisimple-mentedbyPLCcontrolnow.Keywords:PLCControlSystem;PhotoelectricSensor1.IntroductionPLC’sweredevelopedinthelate1960’stoeliminatethelargecostinvolvedinchangingcomplicatedrelaybasedmachinecontrolsystems.Thesesystemswereinflexible.Theirmajorrewiringorcompletereplacementwasnec-essaryeverytimewhentheproductionrequirementschangedandcontrolsequenceshadtobemodified.Itbecameveryexpensivewhenchangeswerefrequent.Theideatoreplacerelaysystemswithflexiblemicroproces-sorbasedProgrammablelogiccontrollersPLC’swasarevolutionarystepintheindustrialcontrolbusiness[1].PLC’shavebeenusedformanyyearsatmanyappli-cations.Theyarethemaincontrolelementsofseveralsubsystemswhichrequirerelativelyslowdatamonitor-ing:theradiationcontrol,personalsafety,fireandsmokealarm.Allthesesubsystemsareverycosteffectiveandreliable.Addingnewequipmenttocontrolorchangingoperatingconditionstoimplementnewcontrolfeaturescaneasilybedonebytheskilledtechnicianstaff,withoutanyhelpfromtheControlsSoftwareGroup.Thesoftwaredevelopmenttoolandsomeideasofde-vicesupportforDirectNetPLC’sbecamethebasisofanewPLCcontrolsoftwarelibraryatcontrolLab.ThesoftwareactsasaDirectNetmasterthroughanyRS-232portandconsistsofthreemainparts:aPLCdriverwithastatemachinecontrolblock,adevicesupportmodule,andacommonserialdriver[2,3].BasicPLC’sareavailableonasingleprintedcircuitboardasshowninFigure1.TheyaresometimescalledsingleboardPLC’soropenframePLC’s.Theseareto-tallyself-contained(withtheexceptionofapowersup-ply)and,wheninstalledinasystem,theyaresimplymountedinsideacontrolscabinetonthreadedstandoffs.Screwterminalsontheprintedcircuitboardallowfortheconnectionoftheinput,output,andpowersupplywires.Theseunitsaregenerallynotexpandable,meaningthatextrainputs,outputs,andmemorycannotbeadded*ImplementthePLCastraineratundergraduatelaboratory.Figure1.OpenframePLC[4].Copyright©2012SciRes.ICAY.I.ALMASHHADANY45tothebasicunit.However,someofthemoresophisti-catedmodelscanbelinkedbycabletoexpansionboardsthatcanprovideextraI/O.Therefore,withfewexcep-tions,whenusingthistypeofPLC,thesystemdesignermusttakecaretospecifyaunitthathasenoughinputs,outputs,andprogrammingcapabilitytohandleboththepresentneedofthesystemandanyfuturemodificationsthatmayberequired.SingleboardPLC’sareveryinex-pensive,easytoprogram,small,andconsumelittlepo-wer,but,generallyspeaking,theydonothavealargenumberofinputsandoutputs,andhaveasomewhatlim-itedinstructionset.Theyarebestsuitedtosmall,rela-tivelysimplecontrolapplications[4].2.HardwareDesignfortheModelInputsto,andoutputsfrom,aPLCarenecessarytomo-nitorandcontrolaprocess.Bothinputsandoutputscanbecategorizedintotwobasictypes:logicalorcontinuous.Considertheexampleofalightbulb.Ifitcanonlybeturnedonoroff,itislogicalcontrol.Ifthelightcanbedimmedtodifferentlevels,itiscontinuous.Continuousvaluesseemmoreintuitive,butlogicalvaluesarepre-ferredbecausetheyallowmorecertainty,andsimplifycontrol.Asaresultmostcontrolsapplications(andPLC’s)uselogicalinputsandoutputsformostapplica-tions[5].OutputstoactuatorsallowaPLCtocausesomethingtohappeninaprocess.Ashortlistofpopularactuatorsisgivenbelowinorderofrelativepopularity.SolenoidValves—logicaloutputsthatcanswitchahydraulicorpneumaticflow.MotorStarters—motorsoftendrawalargeamountofcurrentwhenstarted,sotheyrequiremotorstarters,whicharebasicallylargerelays.ServoMotors—acontinuousoutputfromthePLCcancommandavariablespeedorposition.OutputsfromPLC’sareoftenrelays,buttheycanalsobesolidstateelectronicssuchastransistorsforDCout-putsorTriacsforACoutputs.Continuousoutputsre-quirespecialoutputcardswithdigitaltoanalogconvert-ers,orcanbeusedanothermoduleforPLCanalogueo/p.Inputscomefromsensorsthattranslatephysicalphe-nomenaintoelectricalsignals.Typicalexamplesofsen-sorsarelistedbelowinrelativeorder