2--1-中英文對(duì)照外文翻譯(文檔含英文原文和中文翻譯)基于單片機(jī)的步進(jìn)電機(jī)控制流水線設(shè)計(jì)摘要：通過采用電子化和智能化技術(shù)，本文實(shí)現(xiàn)了力學(xué)和電子產(chǎn)品流水線包裝控制的有效整合。要達(dá)到這個(gè)目的，步進(jìn)電機(jī)是由一個(gè)單片微型計(jì)算機(jī)（SCM）式STC89C516RD+的控制。一旦LJ-JT02的光電開關(guān)型檢測(cè)產(chǎn)品合格，信號(hào)給出了以供應(yīng)鏈管理為指導(dǎo)的步進(jìn)電機(jī)。此外，剪刀用于切斷包裝帶，這是由HRS4H-S-DC5V的繼電器類型實(shí)現(xiàn)。實(shí)驗(yàn)結(jié)果表明，上述設(shè)計(jì)的有效性。關(guān)鍵詞：?jiǎn)纹瑱C(jī)（SCM）；步進(jìn)電機(jī)；驅(qū)動(dòng)芯片；接力1引言在20世紀(jì)50年代到70年代，隨著電子和合成化學(xué)品的快速發(fā)展，對(duì)用合成材料作為包裝材料的一系列新的包裝技術(shù)和設(shè)備有很大的影響。例如，有高速自動(dòng)包裝機(jī)的機(jī)電一體化，容易操作的多功能包裝機(jī)和高生產(chǎn)率的自動(dòng)包裝機(jī)。這些機(jī)器使包裝機(jī)械行業(yè)成為被看好的機(jī)械制造行業(yè)。雖然早在20世紀(jì)50年代中期就已經(jīng)有一些包裝機(jī)械廠出現(xiàn)在中國(guó)，然而生產(chǎn)率很低。在改革開放之初，許多食品機(jī)械和包裝機(jī)械被介紹到中國(guó)，極大地促進(jìn)了行業(yè)發(fā)展。20世紀(jì)80年代后期，國(guó)民經(jīng)濟(jì)的快速發(fā)展對(duì)包裝機(jī)的需求量很大。而與此同時(shí)，很多傳統(tǒng)的用于生產(chǎn)農(nóng)業(yè)機(jī)械的工廠，開始生產(chǎn)包裝機(jī)械。在1997年底，包裝機(jī)械制造廠的數(shù)目已增至1600個(gè)左右，并有大約75個(gè)研究機(jī)構(gòu)從事包裝機(jī)械的研究和開發(fā)。更重要的是，大約有21所高校引入關(guān)于包裝機(jī)械的專業(yè)。因此，該行業(yè)在中國(guó)不僅要推進(jìn)，還應(yīng)進(jìn)一步提高。未來具有微電腦和機(jī)電一體化的包裝機(jī)械將呈現(xiàn)增長(zhǎng)的趨勢(shì)。一個(gè)完整的機(jī)電一體化系統(tǒng)是一個(gè)系統(tǒng)集成multidisciplines，如機(jī)械、微電子計(jì)算機(jī)和傳感器。它帶來了深刻的變化，通過設(shè)計(jì)、制造和包裝機(jī)械的控制和改變industry.In來達(dá)到更快速地開發(fā)。事情應(yīng)該這樣做才能提高包裝機(jī)械，機(jī)電一體化，產(chǎn)品的可靠性和穩(wěn)定性的水平，因此，現(xiàn)代包裝產(chǎn)業(yè)將會(huì)進(jìn)一步得到改善。在這項(xiàng)工作中，我們?cè)谀M包裝流水線的基礎(chǔ)上，由單片機(jī)驅(qū)動(dòng)步進(jìn)電機(jī)控制。首先我們介紹的是硬件電路的整體設(shè)計(jì)和硬件的主要連接，然后描述了軟件設(shè)計(jì)和編程過程，最后我們證明了產(chǎn)品設(shè)計(jì)實(shí)驗(yàn)的可行性，以及對(duì)包裝機(jī)械未來的展望。2硬件電路設(shè)計(jì)2.1總體電路設(shè)計(jì)為了便于實(shí)驗(yàn)，用剪刀和發(fā)光二極管代替部分由步進(jìn)電機(jī)控制的器件。當(dāng)發(fā)光二極管發(fā)光，這意味著相應(yīng)的端口輸出高電平。如果他們不亮，這意味著相應(yīng)的端口輸出低電平。一種光電開關(guān)被安裝在傳送帶上，如果沒有產(chǎn)品通過時(shí)，光電開關(guān)的紅外線接收器和發(fā)射設(shè)備被關(guān)閉，并且輸出為高電平。如果某些對(duì)象被傳遞，紅外線被中斷，它會(huì)立即輸出一個(gè)負(fù)脈沖。一旦單片機(jī)的輸入端口檢測(cè)到光電開關(guān)傳輸?shù)呢?fù)脈沖，單片機(jī)的輸出端會(huì)產(chǎn)生由程序控制的特殊電平，傳輸?shù)津?qū)動(dòng)芯片，使步進(jìn)電機(jī)工作。當(dāng)包裝的時(shí)間到了，單片機(jī)輸出脈沖信號(hào)給繼電器，使剪刀接近，切斷包裝帶。在這之后，剪刀再次打開，等待下一次的行動(dòng)。2.2主要組件2.2.1步進(jìn)電機(jī)步進(jìn)電機(jī)是一臺(tái)將電脈沖信號(hào)轉(zhuǎn)變?yōu)榻俏灰苹蚓€位移的機(jī)器。步進(jìn)電機(jī)可以作為一個(gè)特殊的電機(jī)，用于控制其他機(jī)器。因?yàn)槠湔`差將不會(huì)被累積，所以被廣泛應(yīng)用于各種開環(huán)控制電路。2.2.2STC89C516RD+SCM是單片微型計(jì)算機(jī)的縮寫，其也被稱為微控制器。它是一種半導(dǎo)體芯片，集成了CPU，ROM，RAM，I/O接口，定時(shí)器/計(jì)數(shù)器，中斷系統(tǒng)和其他一些部件于一身，構(gòu)成了一個(gè)完整的數(shù)字計(jì)算機(jī)。目前該供應(yīng)鏈管理已成功應(yīng)用于智能儀表，機(jī)電設(shè)備，過程控制，數(shù)據(jù)處理，自動(dòng)檢測(cè)，家用電器和其他一些領(lǐng)域。在本設(shè)計(jì)中，我們使用了宏景科技公司生產(chǎn)STC89C516RD+。STC89C516RD+的工作電壓為5V，工作頻率范圍為0-80MHz，其實(shí)際的工作頻率一般為48MHZ。2.2.3L297為了簡(jiǎn)化外圍電路，在此設(shè)計(jì)中，我們采用步進(jìn)電機(jī)驅(qū)動(dòng)芯片L297來驅(qū)動(dòng)它。L297是步進(jìn)電機(jī)的一個(gè)專用控制器。它不僅可以生成四個(gè)控制信號(hào)，還可以控制兩相雙極和四相單極步進(jìn)電機(jī)。L297為20引腳塑料雙列直插器件。2.2.4繼電器一個(gè)中繼被稱為一個(gè)開關(guān)，它關(guān)閉時(shí)可在特殊條件下打開。繼電器的開關(guān)特性已被廣泛應(yīng)用于控制系統(tǒng)，尤其是在離散控制系統(tǒng)。在這個(gè)設(shè)計(jì)中，我們選擇電壓繼電器HRS4H-S-DC5V，這是常用的電路保護(hù)器件，它可以提供過壓保護(hù)和低壓閉鎖。HRS4H-S-DC5V的施加電壓為5V，它的吸合電壓為3.75V。2.3主設(shè)備的連接2.3.1單片機(jī)與L297之間的連接步進(jìn)電機(jī)驅(qū)動(dòng)芯片L297，它只需要輸入的時(shí)鐘，方向和模式信號(hào)是有效的。因此，在軟件編程的過程中，應(yīng)該做的唯一一件事就是從單片機(jī)的P1.1口產(chǎn)生高低電平交替的脈沖。與此同時(shí)，根據(jù)控制轉(zhuǎn)向和模式，使P1.3和P1.4端口都設(shè)置為高級(jí)或符合要求的狀態(tài)。理論上P1.3和L297可以直接連接，但實(shí)際上微控制器的負(fù)荷使P1口的輸出電壓低且不穩(wěn)定。系統(tǒng)不能識(shí)別的高低電壓之間的過渡，因而P1.1不能輸出理想的脈沖到L297。為了解決這個(gè)問題，我們使用電壓跟隨器來連接單片機(jī)的輸出端口。它們可以維持和穩(wěn)定電壓。電壓跟隨器具有良好的抗干擾性，并且可以穩(wěn)定地輸出，因此它可以使電壓達(dá)到其驅(qū)動(dòng)電路的標(biāo)準(zhǔn)。2.3.2L297與步進(jìn)電機(jī)之間的連接7904是一個(gè)普通的門電路芯片，它由四個(gè)AND門構(gòu)成。IRLZ44N是增強(qiáng)型NMOS器件。2.3.3單片機(jī)與繼電器之間的連接原則上單片機(jī)的輸出端口可以直接連接到繼電器，但實(shí)驗(yàn)中單片機(jī)的輸出信號(hào)實(shí)際上是非常不穩(wěn)定的。由于負(fù)載的原因，P1.5的輸出電壓被拉低，因此它不能驅(qū)動(dòng)繼電器。為了解決這個(gè)問題，我們使用光電耦合器來驅(qū)動(dòng)繼電器。光電耦合器具有良好的抗干擾性能，可以解決輸出的問題，這使得電路變得可靠。繼電器VCC為12V，當(dāng)單片機(jī)P1.5輸出高電壓時(shí)，由于繼電器的作用，開關(guān)打開；當(dāng)P1.5輸出低電壓時(shí)，開關(guān)閉合。3軟件設(shè)計(jì)3.1程序流程當(dāng)沒有物體通過時(shí)，光電開關(guān)輸出高電壓。一旦某些物體被檢測(cè)到，這個(gè)光電開關(guān)的輸出立即產(chǎn)生一個(gè)下降沿信號(hào)，并將其輸入到單片機(jī)的P1.0口。然后單片機(jī)輸出的信號(hào)給步進(jìn)電機(jī)驅(qū)動(dòng)器芯片的三個(gè)控制端口：CLK（P1.1），CW（P1.3），HALF（P1.4），以此來控制步進(jìn)電機(jī)的工作。我們可以通過單片機(jī)定時(shí)器設(shè)定具體的包裝時(shí)間。包裝完成后，從P1.5口產(chǎn)生低電壓使繼電器立即導(dǎo)通，然后再次關(guān)閉打開的開關(guān)。這樣就完成切割包裝帶的工作。3.2編程本設(shè)計(jì)中的程序是用C語(yǔ)言編寫的。C語(yǔ)言與匯編語(yǔ)言相比具有較靈活，方便和緊湊的優(yōu)點(diǎn)。更重要的是它可以在一個(gè)大的領(lǐng)域中應(yīng)用，具有良好的便攜性。我們選擇KeilC集成開發(fā)環(huán)境，它具有Windows界面，有效地生成目標(biāo)代碼的特點(diǎn)。大多數(shù)匯編語(yǔ)言代碼生成非常緊湊，易于理解。然后，該程序是由具有操作方便的ISP，STC軟件下載到單片機(jī)的。主程序如下所示：Voidmain(){ports();Time()_init();While(1){if(P1^0==0)…….}}光電開關(guān)的信號(hào)由查詢模式檢測(cè)。與中斷子程序中，相應(yīng)的微控制器產(chǎn)生轉(zhuǎn)換的高低電壓。中斷子程序如下圖所示：P1^1=0;delay(m);P1^1=1;delay(m);P1^3=0;P1^4=0;在主程序中該中斷子程序被調(diào)用多次。被用來產(chǎn)生脈沖，以驅(qū)動(dòng)步進(jìn)電機(jī)工作。在這個(gè)實(shí)驗(yàn)中，我們?cè)O(shè)置全步和反向模式，它在中斷子程序中可以看出。4測(cè)試結(jié)果最后將程序燒寫到單片機(jī)中，來完成完整的硬件電路。為了便于實(shí)驗(yàn)，單片機(jī)的三個(gè)輸出端口：P1.1，P1.3，P1.4，應(yīng)連接到L297再連接到三個(gè)發(fā)光二極管，如圖6，光發(fā)光二極管以發(fā)光來判斷輸出高電壓。因此，他們滅，表示從單片機(jī)輸出低電壓。為了便于觀察，該繼電器的輸出端連接一個(gè)發(fā)光二極管，而不是剪刀。在開始時(shí)，四個(gè)光發(fā)二極管全都發(fā)光。實(shí)驗(yàn)的結(jié)果表明，當(dāng)光電開關(guān)檢測(cè)到某些對(duì)象時(shí)，P1.1的發(fā)光二極管開始閃爍，表示產(chǎn)生脈沖，同時(shí)P1.3和P1.4的發(fā)光二極管立即熄滅，表示步進(jìn)馬達(dá)開始正向和半步模式工作。一段時(shí)間后，連接到所述延遲器輸出的發(fā)光二極管亮起后立即熄滅，表示開關(guān)打開，然后再關(guān)閉。該行為是指剪刀切斷包裝膠帶，然后再打開，等待下一步的行動(dòng)。5結(jié)論該實(shí)驗(yàn)?zāi)Mpipeling控制的進(jìn)程，由單片機(jī)驅(qū)動(dòng)步進(jìn)電機(jī)。值得注意的是，在實(shí)踐中，輸出電壓被下拉是因?yàn)樨?fù)載低且不穩(wěn)定，因此，電壓跟隨器和光電耦合器在這里是為了防干擾。本文結(jié)合單片機(jī)和步進(jìn)電機(jī)來模擬包裝生產(chǎn)線控制。可以通過用單片機(jī)編程，而不是模擬通道或數(shù)字電路來實(shí)現(xiàn)。這種控制技術(shù)，可以提高系統(tǒng)的性能，不依賴于硬件，但需要軟件評(píng)測(cè)，這就是所謂的微控制技術(shù)。隨著微控制技術(shù)的發(fā)展，全自動(dòng)和智力水平將在包裝行業(yè)得到不斷的提高。PipeliningDesignControlledbyStepperMotorBasedonSCMAbstract:Byemployingelectronicsandintelligenttechnology,thispaperrealizesaneffectiveintegrationofmechanicsandelectronicsinpipeliningpackingcontrol.Toachievethisaim,steppermotoriscontrolledbyasingle-chipmicrocomputer(SCM)typeofSTC89C516RD+.OncethephotoelectricswitchtypeofLJ-JT02detectsproductspassing,signalsaregivenouttoSCMtodirectthesteppermotor.Furthermore,thescissorsareusedtocutoffthepackagetape,whicharerealizedbyarelaytypeofHRS4H-S-DC5V.Theexperimentalresultsshowtheeffectivenessofabovedesign.Keyword:Single-chipMicrocomputer(SCM);StepperMotor;Driving-chip;Relay1INTRODUCTIONDuringthe1950sto1970s,withtherapiddevelopmentofelectronicsandsyntheticchemicals,thepackagingmachineryhasbeeninfluencedalot,andtherewereaseriesofnewpackagingtechnologyandequipmentbasedonsyntheticmaterialsaspackingmaterials.Forexample,therewerehigh-speedautomatedpackagingmachinesofelectromechanicalintegration,multi-functionalpackagingmachineswhichareeasytooperateandautomaticpackagingmachineswithhighproductivity.Thosemachinesmadethepackagingmachineryindustrypromisinginthemachinerymanufacturingindustry.Althoughtherewerealreadysomepackagingmachineryfactoriesasearlyasthemid1950sinChina,theproductivityisverylow.Atthebeginningofthereformandopeningup,anumberoffoodmachinesandpackagingmachineshavebeenintroducedtoChina,whichpromotedtheindustrygreatly.Duringthelate1980s,therapiddevelopmentofthenationaleconomyhadagreatdemandforpackagingmachines.Andatthesametime,alotoftraditionalfactoriesforagriculturalmachineryproduction,begantheproductionofpackagingmachinery.Attheendof1997,thenumberofpackagingmachineryfactorieshasincreasedtomorethan1,600,andthereareabout75researchinstitutesengaginginresearchanddevelopmentofpackagingmachinery.What’smorethereareapproximatelymorethan21collegesanduniversitiesconcerningpackagingmachineryprofessionally.However,theindustryinChinadoesnotadvanceenoughanditshouldbefurtherimproved.Inthefuturethepackagingmachineryhasagrowingtendencyfortheapplicationofmicrocomputerandelectromechanicalintegration.Acompletemechatronicssystemisasystemtointegratemultidisciplinessuchasmachinery,computersmicroelectronicsandsensors.Itbringsprofoundchangestothedesign,manufacturingandcontrolofpackagingmachineryandchangesthesituationoftheindustry.Inordertodevelopmorequickly,somethingshouldbedonetoimprovethelevelofpackagingmachinery,electromechanicalintegration,productreliabilityandstability,andthusthemodernpackagingindustrywillbeimproved.Inthiswork,wesimulatethecontrolprocessofpackagingassemblylinebasedonsteppermotorwhichisoperatedbySCM.Firstweintroducetheoveralldesignofhardwarecircuitandthemainconnectionofhardware,andthendescribethesoftwaredesignandprogrammingideas,atlastwetestifythefeasibilityofthedesignbyexperiment,aswellasprospectforthefuturepackagingmachinery.2HARDWARECIRCUITDESIGN2.1OverallCircuitDesignTofacilitatetheexperiment,thepartsofscissorsandsteppermotorareinsteadbylight-emittingdiodes.Whenthelight-emittingdiodesarelight,thatmeansthecorrespondingportsoutputhighlevel.Whiletheyarenotlight,thatmeansthecorrespondingportsoutputlowlevel.Aphotoelectricswitchisinstalledontheconveyorbelt.Ifthereisnoproductpassing,theinfraredreceiverandtransmitterdevicesofthephotoelectricswitchareclosedandtheoutputishighlevel.Ifsomeobjectispassing,theinfra-redisinterruptedanditoutputsanegativepulseimmediately.OncetheinputportofSCMdetectsthenegativepulsetransmittedbythephotoelectricswitch,theoutputsofSCMwillproducespecialelectricallevelscontrolledbyprogram,transmittingtoadriverchiptomakesteppermotorwork.Whenthepackingtimeisup,SCMoutputsapulsetotherelay,makingthescissorsclosesothatcuttingoffthepackingtape.Afterthatthescissorsopenagain,waitingforthenextaction.2.2MainComponents2.2.1StepperMotorAsteppermotorisamachinewhichtransmitselectricalpulsesignalsintoangularorlineardisplacement.Thesteppermotorcanbeusedasaspecialmotorforcontrollingothermachinesbecauseitserrorswillnotbeaccumulated.Itiswidelyusedinavarietyofoccasionsofopen-loop.2.2.2STC89C516RD+SCMisanabbreviationofasingle-chipmicro-computer,whichisalsoknownasamicro-controller.Itisasemiconductorchip,integratedbyaCPU,ROM,RAM,I/Ointerface,timer/counter,interruptionsystemsandsomeothercomponents,constitutingacompletedigitalcomputer.AtpresentSCMhasbeensuccessfullyusedinintelligentinstruments,electromechanicaldevices,processcontrols,dataprocessing,automaticdetection,householdappliancesandsomeotherfields.InthisdesignweuseSTC89C516RD+producedbyHongJingTechnologyCompany.STC89C516RD+hasworkingvoltageof5V,workingfrequencybetween0to80MHZ,anditsactualworkingfrequencycanbeupto48MHZ.2.2.3L297Tosimplifytheexternalcircuit,inthisdesignweuseasteppermotordriverchipL297todriveit.L297isaspecialcontrollerforsteppermotors.Itcangeneratefourcontrolsignals.Itcancontroltwo-phasebipolarandfour-phaseunipolarsteppermotors.Thedeviceis20-pinofplasticdualin-line.2.2.4RelayArelayisknownasaswitch.Itclosesoropensinspecialconditions.Theswitchingcharacteristicsoftherelayhasbeenwidelyappliedinmanycontrolsystems,especiallyinadiscretecontrolsystem.InthisdesignweselectvoltagerelayHRS4H-S-DC5Vwhichiscommonlyusedincircuitprotectiondevicesforover-voltageprotectionorlow-voltagelockout.TheappliedvoltageofHRS4H-S-DC5Vis5V,anditspick-upvoltageis3.75V.2.3ConnectionoftheMainDevices2.3.1ConnectionbetweenSCMandL297ThesteppermotordriverchipL297hasanadvantagethatitjustneedsinputtingsignalsofclock,directionandmode.Sointheprogressofsoftwareprogramming,theonlythingwhichshouldbedoneistoproducehigh-lowalternatingpulsesfromP1.1portofSCM.Atthesametime,tocontrolthesteeringandmode,P1.3andP1.4portsaresettohigh-levelorlow-levelonrequest.TheoreticallyspeakingP1.3andL297canbeconnecteddirectly,butactuallytheloadsofmicrocontrollermaketheoutputvoltageofP1portlowandunstable.ThesystemcouldnotidentifythetransitionbetweenthehighandlowvoltagesandthusP1.1cannotoutputidealpulsestotheL297.Inordertosolvethisproblem,weusevoltagefollowerstoconnecttheoutputportsofSCM.Theyaretomaintainandstabilizevoltage.Thevoltagefollowerhasgoodinterferenceimmunityandcanoutputstablysoitcanmakethevoltageachievethestandardwhichdrivesthefollowingcircuit.2.3.2ConnectionBetweenL297andStepperMotor7904isacommongatecircuitchip,whichisformedbyfourANDgates.IRLZ44NisenhancedNMOS.2.3.3ConnectionBetweenSCMandRelayInprincipletheoutputportsofSCMcanbeconnectedtotherelaydirectly.IntheexperimenttheoutputofSCMisactuallyveryunstable,andtheoutputvoltageofP1.5ispulleddownlowbecauseoftheloads,soitcannotdrivetherelay.Tosolvetheproblem,weuseoptocouplertodrivetherelay.Theoptocouplerhasgoodanti-interferenceperformanceandcaneffectlysolvetheoutputproblem,whichmakesthecircuitmorereliable.ThenVCCofrelayis12V.whenP1.5ofSCMoutputshigh-voltage,therelaypowersandthustheswitchisopen.WhenP1.5outputslow-voltage,theswitchisclosed.3SOFTWAREDESIGN3.1ProgramFlowWhenthereisnoobjectpassing,thephotoelectricswitchoutputshigh-voltage.Oncesomeobjectisdetected,theoutputofthephotoelectricswitchgeneratesafallingedgesignalimmediately,andinputittoP1.0ofSCM.ThenSCMoutputsdesiredsignalstothethreecontrolportsofsteppermotordriverchip:CLK(P1.1),CW(P1.3),HALF(P1.4)tocontrolthesteppermotortowork.WecansetspecificpackagingtimethroughtheSCMtimer.Afterfinishingpackaging,amomentlow-voltagefromP1.5isgeneratedtotherelayandmakestheswitchwhichisnormallyclosedopenimmediatelyandthencloseagain.Thatcompletestheactionofcuttingpackingtape.3.2ProgrammingInthisdesigntheprogramiswritteninClanguage.Chastheadvantagesofboththehigh-levellanguageandassemblelanguage.Itisflexible,convenientandcompactinstructure.What’smoreitcanbeappliedinalargeoffieldsandhasgoodportability.WechooseKeilClanguageintegrateddevelopmentenvironmentwhichshowsWindowsinterfacethatgeneratesobjectcodesefficiently.Themajorityofassemblylanguagecodesgeneratedareverycompactandeasytounderstand.ThentheprogramisburntintoSCMbyISP,aSTCdownloadprogrammingsoftware,whichiseasytooperate.Themainprogramisshownasbelow.Voidmain(){ports();Time()_init();While(1){if(P1^0==0)…….}}Thesignalsofphotoelectricswitcharedetectedbyquerymode.Withinterruptionsubroutine,thecorrespondingmicrocontrollerproducesconversionofhighandlowvoltages.Theinterruptionsubroutineisshownasbelow.P1^1=0;delay(m);P1^1=1;delay(m);P1^3=0;P1^4=0;Inmainprogramthisinterruptionsubroutineiscalledforseveraltimes.Thatgeneratespulsestodrivethesteppermotortowork.Inthisexperimentwesetfull-stepandreversemode,whichcanbeseenintheinterruptionsubroutine.4TESTRESULTSAfterthehardwarecircuitisbuiltcompletely,theprogramisburntintotheSCM.Inordertoeasytheexperiment,thethreeoutputportsofSCM,P1.1,P1.3,P1.4,whichshouldbeconnectedtoL297,isconnectedtothreelightemittingdiodes,asshowninFigure6.Thatthelightemittingdiodesarelightmeanstooutputhighvoltage.AndthattheyareoffmeanstooutputlowvoltagefromSCM.Inordertofacilitateobservation,theoutputoftherelayisalsoconnectedtoalight-emittingdiodeinsteadofs