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PROGRAMMABLELOGICCONTROLLERSPLC1ABOUTPROGRAMMABLELOGICCONTROLLERSPLCEVERYONEKNOWSTHERESONLYONECONSTANTINTHETECHNOLOGYWORLD,ANDTHATSCHANGETHISISESPECIALLYEVIDENTINTHEEVOLUTIONOFPROGRAMMABLELOGICCONTROLLERSPLCANDTHEIRVARIEDAPPLICATIONSFROMTHEIRINTRODUCTIONMORETHAN30YEARSAGO,PLCHASBECOMETHECOMERSTONEOFHUNDREDSOFTHOUSANDSOFCONTROLSYSTEMSINAWIDERANGEOFINDUSTRIESATHEART,THEPLCISANINDUSTRIALIZEDCOMPUTERPROGRAMMEDWITHHIGHLYSPECIALIZEDLANGUAGES,ANDITCONTINUESTOBENEFITFROMTECHNOLOGICALADVANCESINTHECOMPUTERANDINFORMATIONTECHNOLOGYWORLDSTHEMOSTPROMINENTOFWHICHISMINIATURIZATIONANDCOMMUNICATIONSPROGRAMMABLELOGICCONTROLLERSI/OCHANNELSPECIFICATIONSINCLUDETOTALNUMBEROFPOINTS,NUMBEROFINPUTSANDOUTPUTS,ABILITYTOEXPAND,ANDMAXIMUMNUMBEROFCHANNELSNUMBEROFPOINTSISTHESUMOFTHEINPUTSANDTHEOUTPUTSPLCMAYBESPECIFIEDBYANYPOSSIBLECOMBINATIONOFTHESEVALUESEXPANDABLEUNITSMAYBESTACKEDORLINKEDTOGETHERTOINCREASETOTALCONTROLCAPACITYMAXIMUMNUMBEROFCHANNELSREFERSTOTHEMAXIMUMTOTALNUMBEROFINPUTANDOUTPUTCHANNELSINANEXPANDEDSYSTEMPLCSYSTEMSPECIFICATIONSTOCONSIDERINCLUDESCANTIME,NUMBEROFINSTRUCTIONS,DATAMEMORY,ANDPROGRAMMEMORYSCANTIMEISTHETIMEREQUIREDBYTHEPLCTOCHECKTHESTATESOFITSINPUTSANDOUTPUTSINSTRUCTIONSARESTANDARDOPERATIONSSUCHASMATHFUNCTIONSAVAILABLETOPLCSOFTWAREDATAMEMORYISTHECAPACITYFORDATASTORAGEPROGRAMMEMORYISTHECAPACITYFORCONTROLSOFTWAREAVAILABLEINPUTSFORPROGRAMMABLELOGICCONTROLLERSINCLUDEDC,AC,ANALOG,THERMOCOUPLE,RTD,FREQUENCYORPULSE,TRANSISTOR,ANDINTERRUPTINPUTSOUTPUTSFORPLCINCLUDEDC,AC,RELAY,ANALOG,FREQUENCYORPULSE,TRANSISTOR,TRIACPROGRAMMINGOPTIONSFORPLCINCLUDEFRONTPANEL,HANDHELD,ANDCOMPUTERPROGRAMMABLELOGICCONTROLLERSUSEAVARIETYOFSOFTWAREPROGRAMMINGLANGUAGESFORCONTROLTHESEINCLUDEIEC611313,SEQUENTIALFUNCTIONCHARTSFC,FUNCTIONBLOCKDIAGRAMFBD,LADDERDIAGRAMLD,STRUCTUREDTEXTST,INSTRUCTIONLISTIL,RELAYLADDERLOGICRLL,FLOWCHART,C,ANDBASICTHEIEC611313PROGRAMMINGENVIRONMENTPROVIDESSUPPORTFORFIVELANGUAGESSPECIFIEDBYTHEGLOBALSTANDARDSEQUENTIALFUNCTIONCHART,FUNCTIONBLOCKDIAGRAM,LADDERDIAGRAM,STRUCTUREDTEXT,ANDINSTRUCTIONLISTTHISALLOWSFORMULTIVENDORCOMPATIBILITYANDMULTILANGUAGEPROGRAMMINGSFCISAGRAPHICALLANGUAGETHATPROVIDESCOORDINATIONOFPROGRAMSEQUENCES,SUPPORTINGALTERNATIVESEQUENCESELECTIONSANDPARALLELSEQUENCESFBDUSESABROADFUNCTIONLIBRARYTOBUILDCOMPLEXPROCEDURESINAGRAPHICALFORMATSTANDARDMATHANDLOGICFUNCTIONSMAYBECOORDINATEDWITHCUSTOMIZABLECOMMUNICATIONANDINTERFACEFUNCTIONSLDISAGRAPHICLANGUAGEFORDISCRETECONTROLANDINTERLOCKINGLOGICITISCOMPLETELYCOMPATIBLEWITHFBDFORDISCRETEFUNCTIONCONTROLSTISATEXTLANGUAGEUSEDFORCOMPLEXMATHEMATICALPROCEDURESANDCALCULATIONSLESSWELLSUITEDTOGRAPHICALLANGUAGESILISALOWLEVELLANGUAGESIMILARTOASSEMBLYCODEITISUSEDINRELATIVELYSIMPLELOGICINSTRUCTIONSRELAYLADDERLOGICRLL,ORLADDERDIAGRAMS,ISTHEPRIMARYPROGRAMMINGLANGUAGEFORPROGRAMMABLELOGICCONTROLLERSPLCLADDERLOGICPROGRAMMINGISAGRAPHICALREPRESENTATIONOFTHEPROGRAMDESIGNEDTOLOOKLIKERELAYLOGICFLOWCHARTISAGRAPHICALLANGUAGETHATDESCRIBESSEQUENTIALOPERATIONSINACONTROLLERSEQUENCEORAPPLICATIONITISUSEDTOBUILDMODULAR,REUSABLEFUNCTIONLIBRARIESCISAHIGHLEVELPROGRAMMINGLANGUAGESUITEDTOHANDLETHEMOSTCOMPLEXCOMPUTATION,SEQUENTIAL,ANDDATALOGGINGTASKSITISTYPICALLYDEVELOPEDANDDEBUGGEDONAPCBASICISAHIGHLEVELLANGUAGEUSEDTOHANDLEMATHEMATICAL,SEQUENTIAL,DATACAPTURINGANDINTERFACEFUNCTIONSPROGRAMMABLELOGICCONTROLLERSCANALSOBESPECIFIEDWITHANUMBEROFCOMPUTERINTERFACEOPTIONS,NETWORKSPECIFICATIONSANDFEATURESPLCPOWEROPTIONS,MOUNTINGOPTIONSANDENVIRONMENTALOPERATINGCONDITIONSAREALLALSOIMPORTANTTOCONSIDER2INTRODUCTIONFORSIMPLEPROGRAMMINGTHERELAYMODELOFTHEPLCISSUFFICIENTASMORECOMPLEXFUNCTIONSAREUSEDTHEMORECOMPLEXVONNEUMANMODELOFTHEPLCMUSTBEUSEDAVONNEUMANCOMPUTERPROCESSESONEINSTRUCTIONATATIMEMOSTCOMPUTERSOPERATETHISWAY,ALTHOUGHTHEYAPPEARTOBEDOINGMANYTHINGSATONCECONSIDERTHECOMPUTERCOMPONENTSSHOWNINFIGURE1FIGURE1SIMPLIFIEDPERSONALCOMPUTERARCHITECTUREINPUTISOBTAINEDFROMTHEKEYBOARDANDMOUSE,OUTPUTISSENTTOTHESCREEN,ANDTHEDISKANDMEMORYAREUSEDFORBOTHINPUTANDOUTPUTFORSTORAGENOTETHEDIRECTIONSOFTHESEARROWSAREVERYIMPORTANTTOENGINEERS,ALWAYSPAYATTENTIONTOINDICATEWHEREINFORMATIONISFLOWINGTHISFIGURECANBEREDRAWNASINFIGURE2TOCLARIFYTHEROLEOFINPUTSANDOUTPUTSFIGURE2ANINPUTOUTPUTORIENTEDARCHITECTUREINTHISFIGURETHEDATAENTERSTHELEFTSIDETHROUGHTHEINPUTSNOTEMOSTENGINEERINGDIAGRAMSHAVEINPUTSONTHELEFTANDOUTPUTSONTHERIGHTITTRAVELSTHROUGHBUFFERINGCIRCUITSBEFOREITENTERSTHECPUTHECPUOUTPUTSDATATHROUGHOTHERCIRCUITSMEMORYANDDISKSAREUSEDFORSTORAGEOFDATATHATISNOTDESTINEDFOROUTPUTIFWELOOKATAPERSONALCOMPUTERASACONTROLLER,ITISCONTROLLINGTHEUSERBYOUTPUTTINGSTIMULIONTHESCREEN,ANDINPUTTINGRESPONSESFROMTHEMOUSEANDTHEKEYBOARDAPLCISALSOACOMPUTERCONTROLLINGAPROCESSWHENFULLYINTEGRATEDINTOANAPPLICATIONTHEANALOGIESBECOMEINPUTSTHEKEYBOARDISANALOGOUSTOAPROXIMITYSWITCHINPUTCIRCUITSTHESERIALINPUTCHIPISLIKEA24VDCINPUTCARDCOMPUTERTHE686CPUISLIKEAPLCCPUUNITOUTPUTCIRCUITSAGRAPHICSCARDISLIKEATRIACOUTPUTCARDOUTPUTSAMONITORISLIKEALIGHTSTORAGEMEMORYINPLCISSIMILARTOMEMORIESINPERSONALCOMPUTERSITISALSOPOSSIBLETOIMPLEMENTAPLCUSINGANORMALPERSONALCOMPUTER,ALTHOUGHTHISISNOTADVISABLEINTHECASEOFAPLCTHEINPUTSANDOUTPUTSAREDESIGNEDTOBEMORERELIABLEANDRUGGEDFORHARSHPRODUCTIONENVIRONMENTS3OPERATIONSEQUENCEALLPLCHAVEFOURBASICSTAGESOFOPERATIONSTHATAREREPEATEDMANYTIMESPERSECONDINITIALLYWHENTURNEDONTHEFIRSTTIMEITWILLCHECKITSOWNHARDWAREANDSOFTWAREFORFAULTSIFTHEREARENOPROBLEMSITWILLCOPYALLTHEINPUTANDCOPYTHEIRVALUESINTOMEMORY,THISISCALLEDTHEINPUTSCANUSINGONLYTHEMEMORYCOPYOFTHEINPUTSTHELADDERLOGICPROGRAMWILLBESOLVEDONCE,THISISCALLEDTHELOGICSCANWHILESOLVINGTHELADDERLOGICTHEOUTPUTVALUESAREONLYCHANGEDINTEMPORARYMEMORYWHENTHELADDERSCANISDONETHEOUTPUTSWILLBEUPDATEDUSINGTHETEMPORARYVALUESINMEMORY,THISISCALLEDTHEOUTPUTSCANTHEPLCNOWRESTARTSTHEPROCESSBYSTARTINGASELFCHECKFORFAULTSTHISPROCESSTYPICALLYREPEATS10TO100TIMESPERSECONDASISSHOWNINFIGURE3FIGURE3PLCSCANCYCLESELFTESTCHECKSTOSEEIFALLCARDSERRORFREE,RESETWATCHDOGTIMER,ETCAWATCHDOGTIMERWILLCAUSEANERROR,ANDSHUTDOWNTHEPLCIFNOTRESETWITHINASHORTPERIODOFTIMETHISWOULDINDICATETHATTHELADDERLOGICISNOTBEINGSCANNEDNORMALLYINPUTSCANREADSINPUTVALUESFROMTHECHIPSINTHEINPUTCARDS,ANDCOPIESTHEIRVALUESTOMEMORYTHISMAKESTHEPLCOPERATIONFASTER,ANDAVOIDSCASESWHEREANINPUTCHANGESFROMTHESTARTTOTHEENDOFTHEPROGRAMEG,ANEMERGENCYSTOPTHEREARESPECIALPLCFUNCTIONSTHATREADTHEINPUTSDIRECTLY,ANDAVOIDTHEINPUTTABLESLOGICSOLVE/SCANBASEDONTHEINPUTTABLEINMEMORY,THEPROGRAMISEXECUTED1STEPATATIME,ANDOUTPUTSAREUPDATEDTHISISTHEFOCUSOFTHELATERSECTIONSOUTPUTSCANTHEOUTPUTTABLEISCOPIEDFROMMEMORYTOTHEOUTPUTCHIPSTHESECHIPSTHENDRIVETHEOUTPUTDEVICESTHEINPUTANDOUTPUTSCANSOFTENCONFUSETHEBEGINNER,BUTTHEYAREIMPORTANTTHEINPUTSCANTAKESASNAPSHOTOFTHEINPUTS,ANDSOLVESTHELOGICTHISPREVENTSPOTENTIALPROBLEMSTHATMIGHTOCCURIFANINPUTTHATISUSEDINMULTIPLEPLACESINTHELADDERLOGICPROGRAMCHANGEDWHILEHALFWAYTHROUGHALADDERSCANSTHISPROBLEMCOULDHAVESEVEREEFFECTSONCOMPLEXPROGRAMSTHATAREDEVELOPEDLATERINTHEBOOKONESIDEEFFECTOFTHEINPUTSCANISTHATIFACHANGEININPUTISTOOSHORTINDURATION,ITMIGHTFALLBETWEENINPUTSCANSANDBEMISSEDWHENTHEPLCISINITIALLYTURNEDONTHENORMALOUTPUTSWILLBETURNEDOFFTHISDOESNOTAFFECTTHEVALUESOFTHEINPUTS4THEINPUTANDOUTPUTSCANSWHENTHEINPUTSTOTHEPLCARESCANNEDTHEPHYSICALINPUTVALUESARECOPIEDINTOMEMORYWHENTHEOUTPUTSTOAPLCARESCANNEDTHEYARECOPIEDFROMMEMORYTOTHEPHYSICALOUTPUTSWHENTHELADDERLOGICISSCANNEDITUSESTHEVALUESINMEMORY,NOTTHEACTUALINPUTOROUTPUTVALUESTHEPRIMARYREASONFORDOINGTHISISSOTHATIFAPROGRAMUSESANINPUTVALUEINMULTIPLEPLACES,ACHANGEINTHEINPUTVALUEWILLNOTINVALIDATETHELOGICALSO,IFOUTPUTBITSWERECHANGEDASEACHBITWASCHANGED,INSTEADOFALLATONCEATTHEENDOFTHESCANTHEPLCWOULDOPERATEMUCHSLOWER5THELOGICSCANLADDERLOGICPROGRAMSAREMODELLEDAFTERRELAYLOGICINRELAYLOGICEACHELEMENTINTHELADDERWILLSWITCHASQUICKLYASPOSSIBLEBUTINAPROGRAMELEMENTSCANONLYBEEXAMINESONEATATIMEINAFIXEDSEQUENCECONSIDERTHELADDERLOGICINFIGURE4,THELADDERLOGICWILLBEINTERPRETEDLEFTTORIGHT,TOPTOBOTTOMINTHEFIGURETHELADDERLOGICSCANBEGINSATTHETOPRUNGATTHEENDOFTHERUNGITINTERPRETSTHETOPOUTPUTFIRST,THENTHEOUTPUTBRANCHEDBELOWITONTHESECONDRUNGITSOLVESBRANCHES,BEFOREMOVINGALONGTHELADDERLOGICRUNGFIGURE4LADDERLOGICEXECUTIONSEQUENCEITALSOBECOMESIMPORTANTWHENCONSIDERINGOUTPUTUSAGECONSIDERFIGURE5,THEFIRSTLINEOFLADDERLOGICWILLEXAMINEINPUTAANDSETOUTPUTXTOHAVETHESAMEVALUETHESECONDLINEWILLEXAMINEINPUTBANDSETTHEOUTPUTXTOHAVETHEOPPOSITEVALUESOTHEVALUEOFXWASONLYEQUALTOAUNTILTHESECONDLINEOFLADDERLOGICWASSCANNEDRECALLTHATDURINGTHELOGICSCANTHEOUTPUTSAREONLYCHANGEDINMEMORY,THEACTUALOUTPUTSAREONLYUPDATEDWHENTHELADDERLOGICSCANISCOMPLETETHEREFORETHEOUTPUTSCANWOULDUPDATETHEREALOUTPUTSBASEDUPONTHESECONDLINEOFLADDERLOGIC,ANDTHEFIRSTLINEOFLADDERLOGICWOULDBEINEFFECTIVEFIGURE5ADUPLICATEDOUTPUTERRORS6PLCSTATUSTHELACKOFKEYBOARDANDOTHERINPUTOUTPUTDEVICESISVERYNOTICEABLEONAPLCONTHEFRONTOFTHEPLCTHEREARENORMALLYLIMITEDSTATUSLIGHTSCOMMONLIGHTSINDICATEPOWERONTHISWILLBEONWHENEVERTHEPLCHASPOWERPROGRAMRUNNINGTHISWILLOFTENINDICATEIFAPROGRAMISRUNNING,ORIFNOPROGRAMISRUNNINGFAULTTHISWILLINDICATEWHENTHEPLCHASEXPERIENCEDAMAJORHARDWAREORSOFTWAREPROBLEMTHESELIGHTSARENORMALLYUSEDFORDEBUGGINGLIMITEDBUTTONSWILLALSOBEPROVIDEDFORPLCHARDWARETHEMOSTCOMMONWILLBEARUN/PROGRAMSWITCHTHATWILLBESWITCHEDTOPROGRAMWHENMAINTENANCEISBEINGCONDUCTED,ANDBACKTORUNWHENINPRODUCTIONTHISSWITCHNORMALLYREQUIRESAKEYTOKEEPUNAUTHORIZEDPERSONNELFROMALTERINGTHEPLCPROGRAMORSTOPPINGEXECUTIONAPLCWILLALMOSTNEVERHAVEANONOFFSWITCHORRESETBUTTONONTHEFRONTTHISNEEDSTOBEDESIGNEDINTOTHEREMAINDEROFTHESYSTEMTHESTATUSOFTHEPLCCANBEDETECTEDBYLADDERLOGICALSOITISCOMMONFORPROGRAMSTOCHECKTOSEEIFTHEYAREBEINGEXECUTEDFORTHEFIRSTTIME,ASSHOWNINFIGURE6THEFIRSTSCANINPUTWILLBETRUEONTHEVERYFIRSTTIMETHELADDERLOGICISSCANNED,BUTFALSEONEVERYOTHERSCANINTHISCASETHEADDRESSFORFIRSTSCANSINAPLC5ISS21/14WITHTHELOGICINTHEEXAMPLETHEFIRSTSCANWILLSEALONLIGHT,UNTILCLEARISTURNEDONSOTHELIGHTWILLTURNONAFTERTHEPLCHASBEENTURNEDON,BUTITWILLTURNOFFANDSTAYOFFAFTERCLEARISTURNEDONTHEFIRSTSCANBITISALSOREFERREDTOATTHEFIRSTPASSBITFIGURE6APROGRAMSTHATCHECKSFORTHEFIRSTSCANOFTHEPLC7MEMORYTYPESTHEREAREAFEWBASICTYPESOFCOMPUTERMEMORYTHATAREINUSETODAYRAMRANDOMACCESSMEMORYTHISMEMORYISFAST,BUTITWILLLOSEITSCONTENTSWHENPOWERISLOST,THISISKNOWNASVOLATILEMEMORYEVERYPLCUSESTHISMEMORYFORTHECENTRALCPUWHENRUNNINGTHEPLCROMREADONLYMEMORYTHISMEMORYISPERMANENTANDCANNOTBEERASEDITISOFTENUSEDFORSTORINGTHEOPERATINGSYSTEMFORTHEPLCEPROMERASABLEPROGRAMMABLEREADONLYMEMORYTHISISMEMORYTHATCANBEPROGRAMMEDTOBEHAVELIKEROM,BUTITCANBEERASEDWITHULTRAVIOLETLIGHTANDREPROGRAMMEDEEPROMELECTRONICALLYERASABLEPROGRAMMABLEREADONLYMEMORYTHISMEMORYCANSTOREPROGRAMSLIKEROMITCANBEPROGRAMMEDANDERASEDUSINGAVOLTAGE,SOITISBECOMINGMOREPOPULARTHANEPROMSALLPLCUSERAMFORTHECPUANDROMTOSTORETHEBASICOPERATINGSYSTEMFORTHEPLCWHENTHEPOWERISONTHECONTENTSOFTHERAMWILLBEKEPT,BUTTHEISSUEISWHATHAPPENSWHENPOWERTOTHEMEMORYISLOSTORIGINALLYPLCVENDORSUSEDRAMWITHABATTERYSOTHATTHEMEMORYCONTENTSWOULDNOTBELOSTIFTHEPOWERWASLOSTTHISMETHODISSTILLINUSE,BUTISLOSINGFAVOREPROMSHAVEALSOBEENAPOPULARCHOICEFORPROGRAMMINGPLCTHEEPROMISPROGRAMMEDOUTOFTHEPLC,ANDTHENPLACEDINTHEPLCWHENTHEPLCISTURNEDONTHELADDERLOGICPROGRAMONTHEEPROMISLOADEDINTOTHEPLCANDRUNTHISMETHODCANBEVERYRELIABLE,BUTTHEERASINGANDPROGRAMMINGTECHNIQUECANBETIMECONSUMINGEEPROMMEMORIESAREAPERMANENTPARTOFTHEPLC,ANDPROGRAMSCANBESTOREDINTHEMLIKEEPROMMEMORYCOSTSCONTINUETODROP,ANDNEWERTYPESSUCHASFLASHMEMORYAREBECOMINGAVAILABLE,ANDTHESECHANGESWILLCONTINUETOIMPACTPLC8SOFTWAREBASEDPLCTHEDROPPINGCOSTOFPERSONALCOMPUTERSISINCREASINGTHEIRUSEINCONTROL,INCLUDINGTHEREPLACEMENTOFPLCSOFTWAREISINSTALLEDTHATALLOWSTHEPERSONALCOMPUTERTOSOLVELADDERLOGIC,READINPUTSFROMSENSORSANDUPDATEOUTPUTSTOACTUATORSTHESEAREIMPORTANTTOMENTIONHEREBECAUSETHEYDONTOBEYTHEPREVIOUSTIMINGMODELFOREXAMPLE,IFTHECOMPUTERISRUNNINGAGAMEITMAYSLOWORHALTTHECOMPUTERTHISISSUEANDOTHERSARECURRENTLYBEINGINVESTIGATEDANDGOODSOLUTIONSSHOULDBEEXPECTEDSOON9SUMMARYAPLCANDCOMPUTERARESIMILARWITHINPUTS,OUTPUTS,MEMORY,ETCTHEPLCCONTINUOUSLYGOESTHROUGHACYCLEINCLUDINGASANITYCHECK,INPUTSCAN,LOGICSCAN,ANDOUTPUTSCANWHILETHELOGICISBEINGSCANNED,CHANGESINTHEINPUTSARENOTDETECTED,ANDTHEOUTPUTSARENOTUPDATEDPLCUSERAM,ANDSOMETIMEEPROMSAREUSEDFORPERMANENTPROGRAMS10PRACTICEPROBLEMSDOESAPLCNORMALLYCONTAINRAM,ROM,EPROMAND/ORBATTERIESWHATARETHEINDICATORLIGHTSONAPLCUSEDFORAPLCCANONLYGOTHROUGHTHELADDERLOGICAFEWTIMESPERSECONDWHYWHATWILLHAPPENIFTHESCANTIMEFORAPLCISGREATERTHANTHETIMEFORANINPUTPULSEWHYWHATISTHEDIFFERENCEBETWEENAPLCANDADESKTOPCOMPUTERWHYDOESPLCDOASELFCHECKEVERYSCANWILLTHETESTTIMEFORAPLCBELONGCOMPAREDTOTHETIMEREQUIREDFORASIMPLEPROGRAMWHATISWRONGWITHTHEFOLLOWINGLADDERLOGICWHATWILLHAPPENIFITISUSEDWHATISTHEADDRESSFORAMEMORYLOCATIONTHATINDICATESWHENAPLCHASJUSTBEENTURNEDON11PRACTICEPROBLEMSOLUTIONSEVERYPLCCONTAINSRAMANDROM,BUTTHEYMAYALSOCONTAINEPROMORBATTERIESDIAGNOSTICANDMAINTENANCEEVENIFTHEPROGRAMWASEMPTYTHEPLCWOULDSTILLNEEDTOSCANINPUTSANDOUTPUTS,ANDDOASELFCHECKTHEPULSEMAYBEMISSEDIFITOCCURSBETWEENTHEINPUTSCANSSOMEKEYDIFFERENCESINCLUDEINPUTS,OUTPUTS,ANDUSESAPLCHASBEENDESIGNEDFORTHEFACTORYFLOOR,SOITDOESNOTHAVEINPUTSSUCHASKEYBOARDSANDMICEALTHOUGHSOMENEWERTYPESCANTHEYALSODONOTHAVEOUTPUTSSUCHASASCREENORSOUNDINSTEADTHEYHAVEINPUTSANDOUTPUTSFORVOLTAGESANDCURRENTTHEPLCRUNSUSERDESIGNEDPROGRAMSFORSPECIALIZEDTASKS,WHEREASONAPERSONALCOMPUTERITISUNCOMMONFORAUSERTOPROGRAMTHEIRSYSTEMTHISHELPSDETECTFAULTYHARDWAREORSOFTWARETHESELFCHECKHELPSDETECTTHESETYPESOFFAULTS,ANDSHUTTHESYSTEMDOWNSAFELYYES,THESELFCHECKISEQUIVALENTTOABOUT1MSINMANYPLC,BUTASINGLEPROGRAMINSTRUCTIONISABOUT1MICROSECONDTHENORMALOUTPUTYISREPEATEDTWICEINTHISEXAMPLETHEVALUEOFYWOULDALWAYSMATCHB,ANDTHEEARLIERRUNGWITHAWOULDHAVENOEFFECTONYS21/14FORMICROLOGY,S21/15FORPLC512PLCTECHNIQUEDISCUSSIONANDFUTUREDEVELOPMENTALONGWITHTHEDEVELOPMENTOFTHEAGES,THETECHNIQUETHATISNOWADAYSISALSOGRADUALLYPERFECT,THECOMPETITIONPLAYSMORESTRONGTHEOPERATIONTHATLISTDEPENDSTHEARTIFICIALHASALREADYCANTSATISFIEDWITHTHECURRENTMANUFACTURINGINDUSTRYFOREGROUND,ALSOCANTGUARANTEETHEREQUESTOFTHEHIGHERQUANTITYANDHIGHNEWTHEIMAGEOFTHETECHNIQUEBUSINESSENTERPRISETHEPEOPLESEEINPRODUCEPRACTICE,AUTOMATEBROUGHTTHETREMENDOUSCONVENIENCEANDTHEPRODUCTQUANTITIESFORPEOPLEUPOFASSURANCE,ALSOEASEDTHEPERSONNELSLABORSTRENGTH,REDUCETHEESTABLISHMENTONTHEPERSONNELTHETARGETCONTROLOFTHEHARDREALIZATIONINMANYCOMPLICATEDPRODUCTIONLINES,WHOLEANDEXCELLENTTURN,THEBESTDECISIONETC,WELLTRAINEDOPERATIONWORK,TECHNICALPERSONNELOREXPERT,GOVERNORBUTCANJUDGEANDOPERATEEASILY,CANACQUIRETHESATISFIEDRESULTTHERESEARCHTARGETOFTHEARTIFICIALINTELLIGENCEMAKESUSEOFTHECALCULATOREXACTLYTOCARRYOUT,IMITATETHESEINTELLIGENCESBEHAVIOR,MODERATINGTHEWORKTHROUGHPERSONSBRAINANDCALCULATORS,WITHTHEMODETHATPERSONSMACHINECOMBINE,FORRESOLVETHEVERYCOMPLICATEDPROBLEMTOLOOKFORTHEBESTPATHWECOMEINSIGHTOFTHECONTROLTHATLINKSAFTERTHEELECTRICAPPLIANCESINVARIOUSSITUATION,THATISALREADYTHETHATTIMEGENERATIONPAST,NOWOFAFTERUSEINTHEMOLDAPERHAPSSIMPLEEQUIPMENTSOFGRASSROOTSCONTROLTHATTHEELECTRICAPPLIANCESCANDOFORTHELOWLEVELONLYANDTHEPLCEMERGENCEALSOBECAMETHEEPOCHMAKINGTOPIC,ADDINGTHEVIVIDSOFTWARECONTROLTHROUGHAVERYANDSTABLEHARDWARE,MAKINGTHEAUTOMATIONHEADFORTHENEWHIGHTIDETHEPLCBIGGESTCHARACTERISTICSLIEINTHEELECTRICALENGINEERINGTEACHERALREADYNOLONGERELECTRICHARDWAREUPTOOMANYCALCULATIONSOFCOST,ASLONGASORDERTHEIMPORTATIONTHATTHEBUTTONSWITCHORTHEIMPORTATIONOFTHESENSORSORDERTOLINKTHEPLCUPCANSOLVEPROBLEM,PASSTOOUTPUTTOORDERTHECONJUNCTIONCONTACTMACHINEORCONTROLTHESTARTEQUIPMENTSOFTHEBIGPOWERAFTERTHEELECTRICAPPLIANCES,BUTTHEEXPORTATIONEQUIPMENTSDIRECTCONJUNCTIONOFTHESMALLPOWERCANPLCINTERNALCONTAINMENTHAVETHECPUOFTHECPU,ANDTAKETOHAVEANI/OFOREXPANDOFEXTERIORTOCONNECTAPEOPLESADDRESSANDSAVINGMACHINETHREEBIGPIECESTOCONSTITUTE,CPUCOREISFROMANORMANYISTIREDTOADDTHEMACHINETOCONSTITUTE,MATHEMATICSTHATTHEYHAVETHELOGICOPERATIONABILITY,ANDCANREADTHEPROCEDURESAVETHECONTENTSOFTHEMACHINETODRIVETHEHOMOLOGOUSSAVINGMACHINEANDI/OSTOCONNECTAFTERPASSTHECALCULATIONTHEI/OADDINNERPARTISTIREDTHEINPUTANDOUTPUTSYSTEMOFTHEMACHINEANDEXTERIORLINK,ANDDEPOSITTHERELATEDDATAINTOTHEPROCEDURESAVINGMACHINEORDATASAVINGMACHINETHESAVINGMACHINECANDEPOSITTHEDATATHATTHEI/OINPUTINTHESAVINGMACHINE,ANDINWORKADJUSTINGTOBECOMETIREDTOADDTHEMACHINEANDI/OSTOCONNECT,SAVINGMACHINESEPARATELYSAVINGMACHINERAMOFTHEPROCEDURESAVINGMACHINEROMANDDATES,THEROMCANDODEPOSITOFTHEDATAPERMANENCEINTHESAVINGMACHINE,BUTRAMONLYFORTHECPUCOMPUTESTHETEMPORARYCALCULATIONUSAGEOFHOUROFBUFFERSPACETHEPLCANTIINTERFERENCEISVERYANDEXCELLENT,OURROOTNEEDNOTCONCERNITSSERVICELIFEANDTHEWORKSITUATIONBAD,THESEALLPROBLEMSHAVEALREADYNOLONGERBECOMETHETOPICTHATWEFAIL,BUTSTAYTOOURISACONCERNTOCOMETOINTERNALRESOURCESOFMAKEUSEOFTHEPLCTOSTRENGTHENTHECONTROLABILITYOFTHEEQUIPMENTSFORUS,MAKEOUREQUIPMENTSMOREGENTLEPLCLANGUAGEISNOTWEIMAGINEOFEDITCOLLECTEDMATERIALSTHELANGUAGEORLANGUAGEOFCSTOCARRYONWEAVINGTHEDISTANCE,BUTTHETRAPEZOIDDIAGRAMTHATTHEADOPTIONISORIGINALAFTERTHEELECTRICAPPLIANCESTOCONTROL,MAKETHEELECTRICALENGINEERINGTEACHERWHILEWEAVINGTOWRITETHEPROCEDUREVERYEASYCOMPREHENDEDTHEPLCLANGUAGE,ANDALOTOFNONELECTRICITYPROFESSIONALALSOVERYQUICKLYKNOWANDGODEEPINTOTOTHEPLCISPLCONEOFTHEADVANTAGEABOVEANDONLY,THISISALSOONEPARTTHATTHEPEOPLECOMPREHENDMOREANDEASILY,INALOTOFEQUIPMENTS,THEPEOPLEHAVEALREADYNOLONGERHOPEDTOSEETOOMANYCONTROLBUTTONS,THEYDAMAGENOTONLYANDEASILYANDPRODUCETHEARTIFICIALERROREASIEST,SMALLISNOTAMAINERRORPERHAPSYOUCANSTILLACCEPTBUTLEADEVENISAFATALERRORGREATLYISWHATWECANTISTOLERANTOFNEWTECHNIQUEALWAYSFORBRINGINGMORESAFEANDCONVENIENTOPERATIONFORUS,MAKEWEALOTOFPROBLEMSFORFACEONSWEEPBUTLIGHT,DOYOUUNDERSTANDTHEHMISAYSTHEHMIHEREYOUBASICALLYNOTCLEARWHATITIS,ALSOHAVENOINTERESTUNDERSTANDING,CHANGEONEINSIDETEXTEXPLAINSITINTOTHETOUCHTOHOLDORMANMACHINEINTERFACEYOUKNEW,ITCOMBINESWITHTHEPLCTOOURLARGERSPACEHMITHECONTROLNOTONLYISREDUCEDTHECONTROLPRESSBUTTON,INCREASETHEVIVIDOFTHECONTROL,MOREMAINOFITISCANSEQUENCEOF,ANDATCANTHECHANGEDATAINPUTTOOUTPUTTHEFEEDBACKWITHDATA,CONTROLINTHETEMPERATURECURVEOFIMITATEBUTALSOCANKEEPTHEMANIFESTATIONOFVIEWTOCOMEOUTANDCANWRITETHEFUNCTIONHELPPROCEDURETHROUGHAPLAITTOPROVIDETHEHELPOFVARIOUSWHATLIESINONESPOWER,THEONEWHOMAKEOPERATEREDUCESTHEOTIOSEERRORCURRENTLYTHEHMIFACTORYISALSOMOREANDMORE,THEFUNCTIONISALSOMOREANDMORESTRONG,THEPRICEISALSOMOREANDMORELOW,THENOODLESOFTHEUSAGEAREWIDEMOREANDMORETHEHMIFOREGROUNDCANSAYTHATTHI