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I.IntroductionAsweallknow,theionnitridingprocessrequiresrelativelyhighcontrolofthepressureinsidethefurnace,sothispaperdesignsagasflowcontrollerbasedontheL298NchipdrivenDCmotorcontrol,whichcanbeusedtocontrolthegasflowofthereactor.Soletsfirstunderstandtheionnitridingtheory.CatalogI.IntroductionII.IonNitridingTheoryIII.SystemFlowandPressureMeasurementandControlBlockDiagramIV.L298NChipIntroductionV.ControllerPrincipleVI.ConclusionFAQOrdering&QuantityII.IonNitridingTheoryNitridingisachemicalheattreatmentmethodtostrengthenthemetalsurface.Itistoplacemetalpartsinanactivenitrogenmedium,andatacertaintemperatureandholdingtime,thenitrogenelementcanpenetrateintothemetalsurface,therebychangingthechemicalcompositionofthemetallayertomakeithavehighwearresistance,fatiguestrength,corrosionresistanceandburnresistance,etc.,soitiswidelyusedinindustry.Ionnitridingiscarriedoutinalow-temperatureplasma.Thelow-pressuregasisionizedundertheactionofanelectricfieldtoproducehigh-energyionsandhigh-energyneutralatoms.Thesehigh-energyparticlescanimprovethestructureoftheinfiltrationlayer,promotethechemicalreactionprocess,andacceleratethenitridinglayerformation.Ionnitridingiscarriedoutinglowdischarge.Intheprocessofionnitriding,thepressurecontrolaccuracyofthefurnaceisrelativelyhigh,andthecontroldeviationreachesseveraltensofPa.AccordingtoPaschensLaw:Amongthem:Pisthegaspressure;Disthedistancebetweenparallelplateelectrodes;Visthecathodesecondaryelectronemissioncoefficient;BisStolevsconstant;Aisaconstant.Takingthederivativeofformula(1),thebreakdownvoltageexpression(2)canbeobtained:Itcanbeseenfromformula(2)thatthebreakdownvoltageVisrelatedtothegaspressureandd,andingeneralexperiments,disfixed,soionnitridingisextremelyimportantforpressurecontrol.III.SystemFlowandPressureMeasurementandControlBlockDiagramTheflowmetercontrolsthegasflowattheinlet.Whentheinletandexhaustflowsarebalanced,thefurnacepressureremainsstable.Duetotheinternalinfluenceoffurnacegasleakageandotherinterferencefactors,theinternalpressureofthefurnacefluctuatesupanddown,andthesystemdeviatesfromtheequilibriumstate,whichaffectstheplasmaprocessinseverecases.WeuseanordinaryDCmotortodrivetheDCmotorthroughtheL298N,andthemotordrivestheconetorotatethroughthereductionlever.Whentheconeisscrewedin,thegaspumpedoutperunittimeisreduced;whenitisscrewedout,thegaspumpedoutincreases,sothatthepressureinsidethefurnaceisstabilizedattherequiredvalue.Thechangeoffurnacepressureismeasuredbythepressuresensorandpassedthroughthetransmitter,whichsendsthegasflowcontrollertothefeedbackvoltage.Theelectricvacuumbutterflyvalveusedforthesuctionportisexpensive,asshowninFigure1.Figure1BlockdiagramofsystemflowandpressuremeasurementandcontrolIV.L298NChipIntroductionL298NcanacceptstandardTTLlogiclevelsignalVSS,andVSScanbeconnectedto4.5~7Vvoltage.4pinVSisconnectedtothepowersupplyvoltage,andtheVSvoltagerangeVIHis+2.5~46V.Theoutputcurrentcanreach2.5A,whichcandriveinductiveloads.Theemittersofpin1andpin15areseparatelyledouttoconnectthecurrentsamplingresistortoformacurrentsensingsignal.L298candrivetwomotors,OUT1,OUT2andOUT3,OUT4canbeconnectedtoeachmotor,thisexperimentaldevicewechoosetodriveonemotor.Pins5,7,10and12areconnectedtotheinputcontrolleveltocontroltheforwardandreverserotationofthemotor.EnAandEnBareconnectedtothecontrolpotentialenergyendtocontrolthestallingofthemotor.Figure2istheL298Nfunctionallogicdiagram,Table1istheL298Ninternalfuntionalmodule.Figure2L298NfunctionallogicdiagramEnAIn1In2OperativeCondition0Stop110Rotatingforward101Inversion111Brake100StopTable1L298NinternalfunctionalmoduleThefunctionalmoduleofIn3andIn4isthesameasTable1.ItcanbeseenfromTable1thatwhenEnAislowlevel,theinputlevelhasaneffectonmotorcontrol.WhenEnAishighlevel,whenEnAishigh,theinputlevelisonehighandonelow,andthemotorrotatesforwardorreverse.Iftheyarebothlowlevel,themotorwillstop,andiftheyarebothhighlevel,themotorwillbrake.V.ControllerPrincipleFigure3istheschematicdiagramofthecontroller,composedof3dashedblockdiagrams:Figure3TheschematicdiagramofthecontrollerThefollowingarethefunctionsofthe3dashedblockdiagrams:(1)Thedashedblockdiagram1controlstheforwardandreverserotationofthemotor,U1AandU2Aarecomparators,andVIcomesfromthevoltageofthefurnacepressuresensor.WhenVIVRBF1,U1Aoutputshighlevel,U2Aoutputhighlevelturnsintolowlevelthroughinverter,andthemotorrotatesforward.Similarly,whenVIVRBF1,themotorreverses.Theforwardandreverserotationofthemotorcancontroltheflowofgasextractedbytheairextractor,therebychangingthepressureinsidethefurnace.(2)Inthedashedblockdiagram2,twocomparatorsU3AandU4Aformadual-limitcomparator.WhenVBVIVA,itoutputslowlevel,andwhenVIVA,VIVB,itoutputshighlevel.VA,VBaretheupperandlowerlimitsofthevoltageconvertedbythefurnacepressuretransducer,thatis,thecontrolrangeofthereactionfurnacepressure.Accordingtoprocessrequirements,wecanspecifythevaluesofVAandVBbyourselves,aslongasthefurnacepressureiswithintherangedeterminedbyVAandVB,themotorstops(notethatVB<VRBF1<VA,ifitisnotinthisrange,thesystemisunstable).(3)Thedashedblockdiagram3isalongdelaycircuit.U5Aisacomparator,Rs1isthesamplingresistor,VRBF2isthemotorovercurrentvoltage.ThevoltageonRs1isgreaterthanVREF2,themotorisovercurrent,andU5Aoutputslowlevel.Itcanbeseenfromtheabovethatblock1controlstheforwardandreverserotationofthemotor,andblock2controlsthesizeoftherippleofthefurnacepressure.Whenthefurnacepressureistoosmallortoolarge,themotorturnstoafixedpositionatbothendstostop,accordingtothesteady-stateoperatingequationoftheDCmotor:Amongthem:Фisthemagneticfluxofeachpoleofthemotor;Ceistheelectromotiveforceconstant;Nisthenumberofmotorrevolutions;Iaisthearmaturecurrent;Raisthearmatureloopresistance.WhenthenumberofrevolutionsofthemotorNis0,thecurrentofthemotorincreasessharply,andthemotorwillburnoutifthetimeistoolong.Butwhenthemotorstarts,thecurrentinthecoilinthemotoralsoincreasessharply,sowemustseparatethesetwostates.Thelongdelaycircuitcandistinguishthesetwostates.Theworkingprincipleofthelong-delaycircuit:WhentheRs1overcurrentU5Ageneratesanegativepulseandisdifferentiated,thepulsetriggerspin2of555,thecircuitisset,andpin3outputshighlevel.Becausethedischargeterminal7pinisopen,C1,R5andU6Aformedasanintegration,thenstartworking,thechargingvoltageonthecapacitorC1riseslinearly,andtheintegrationconstantofthedelayoperationalamplifieris100R5C1.WhenthechargingvoltageonC1,thatis,thevoltageonpin6exceeds2/3VCC,the555circuitresetsandoutputsalowlevel.Themotorgenerallystart-upinlessthan0.8s,andtheC1chargingtimeisgenerally0.8~1s.TheoutputlevelofU5AisORedwiththeoutputlevelofpin3of555viaU7.IftheoutputlowlevelofU5AislongerthanthechargingtimeofC1,U7outputslowlevelafterC1ischarged.TheANDgateU8inputstothe6pinENAterminalofL298N.Themotorstops.IftheoutputlevelofU5AislessthanthechargingtimeofC1,pin6willnotactandthemotorwillstartnormally.Thelongdelaycircuitabsorbsthemotorstart-upovercurrentvoltagewaveform,sothatthemotorstartsnormally.VI.ConclusionThisarticlesummarizesthedesignschemeforthepressurecontrolofionnitridingbasedontheL298Nchip.Ithasbeenprovedthattheuseofthiscontrollertocontrolthegasflowcanreduceproductioncosts,increasethesystemcostperformance,andimprovethecontroldynamicperformanceandstabilityoftheentiresystemcontrol.FAQWhatisl298n?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.Whatistheuseofl298n?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.Howdoesl298ncontrolDCmotorspeed?1.IfyousendaHIGHsignaltotheenable1pin,motorAisreadytobecontrolledandatthemaximumspeed;2.IfyousendaLOWsignaltotheenable1pin,motorAturnsoff;3.IfyousendaPWMsignal,youcancontrolthespeedofthemotor.Themotorspeedisproportionaltothedutycycle.Whatisl298nmotordrivermodule?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.Howdoesl298nmotordriverwork?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.Howdoiuseal298motordriverwithArduino?Startbyconnectingpowersupplytothemotors.InourexperimentweareusingDCGearboxMotors(alsoknownasTTmotors)thatareusuallyfoundintwo-wheel-driverobots.Theyareratedfor3to12V.So,wewillconnectexternal12VpowersupplytotheVCCterminal.WhatisthefunctionofHbridge?AnH-bridgeisanelectroniccircuitthatswitchesthepolarityofavoltageappliedtoaload.ThesecircuitsareoftenusedinroboticsandotherapplicationstoallowDCmotorstorunforwardsorbackwards.Whatisthedifferencebetweenl293dandl298n?L293isquadruplehalf-HdriverwhileL298isdualfull-Hdriver,i.e,inL293allfourinput-outputlinesareindependentwhileinL298,ahalfHdrivercannotbeusedindependently,onlyfullHdriverhastobeused....Hence,heatsinkisprovidedinL298.

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