您的当前位置:首页 >OPA4227 >OPA4227 正文

OPA4227

时间:2021-04-23 00:26:41 来源:网络整理编辑:OPA4227

核心提示

IDescriptionAD620isalow-power,high-precisioninstrumentationamplifier.BasedontheinformationprovidedbytheADcompany,thisblogintroducesthecharacteristicsandtypicalusageofAD620.Besides,thisblogalsointroducestheapplicationofAD620.Theapplicationsaremainlyaboutphotoelectricdetection,ultrasonictesting,etc.Figure1.AD620IDescriptionIIIntroductionIIIAD620PinoutandWorkingPrincipleIVAD620TypicalUsageVAD620Application5.1ApplicationinPhotoelectricDetection5.2ApplicationinUltrasonicTestingVIConclusionFAQOrdering&QuantityIIIntroductionAD620isalow-power,high-precisioninstrumentationamplifier.Anditcansettheamplificationfactorfrom1to1000withonlyanexternalresistor.Itissmallinsize,inan8-pinSOICorDIPpackage;thepowersupplyrangeis2.3V~18V;themaximumpowersupplycurrentisonly1.3mA.AD620hasgoodDCandACcharacteristics.Itsmaximuminputoffsetvoltageis50V,themaximuminputoffsetvoltagedriftis1V/℃,andthemaximuminputbiascurrentis2.0nA.WhenG=10,itscommon-moderejectionratioisgreaterthan93dB.Theinputvoltagenoiseisat1kHz,thepeak-to-peakvalueoftheinputvoltagenoiseis0.28Vintherangeof0.1Hz~10Hz,andtheinputcurrentnoiseisWhenG=1,itsgainbandwidthis120kHz,andthesettlingtimeis15s.Ingeneral,thecharacteristicsofAD620canbesummarizedasfollows:AD620canensuretheperformanceindicatorsrequiredforhigh-gainprecisionamplification.Forexample,lowoffsetvoltage,lowoffsetvoltagedrift,andlownoise,etc.;Withonlyoneexternalresistor,themagnificationcanbesetfrom1to1000;Smallsize,with8pins;Lowpowerconsumptionanditsmaximumsupplycurrentare1.3mA.IIIAD620PinoutandWorkingPrincipleThepinofAD620isshownasinFig.2,itsstructurediagramisshownasinFig.3.Figure2.AD620PinoutFigure3.AD620StructureDiagramAD620isamonolithicinstrumentamplifier.Itisdevelopedonthebasisoftheimprovementofthetraditionalthree-opamplifiercombination.TheinputtransistorsQ1andQ2providetheonlybipolardifferentialinput.Duetotheinternalsuperprocessing,itsinputoffsetcurrentis10timeslowerthannormal.ThroughthefeedbackoftheQ1-A1-R1loopandtheQ2-A2-R2loop,thecollectorcurrentsofQ1andQ2arekeptconstant.Thus,theinputvoltageisequivalenttothetwoendsoftheexternalresistorRg.AndthedifferentialamplificationfactorfromtheinputtotheA1/A2outputisG=(R1+R2)/Rg+1.TheunitygainsubtractorcomposedofA3eliminatesanycommon-modecomponents.Andthenitproducesasingle-channeloutputrelatedtothepotentialoftheREFpin.ThevalueofRgalsodeterminesthetransconductanceofthepreviousstageopamp.WhenRgdecreases,theamplificationfactorincreases.Andthetransconductancetotheinputtransistorgraduallyincreases.Thishasobviousadvantages:theincreaseintheamplificationfactorincreasestheopen-loopgain.Thus,theerrorrelatedtogainisreduced.Thegain-bandwidthproductdeterminedbyC1,C2andthepre-opamptransconductanceincreases.Thus,thefrequencyresponseisimproved.Theinputvoltagenoiseismainlydeterminedbythecollectorcurrentoftheinputtransistorandthebaseresistance.Andtheinputvoltagenoiseisreducedto.TheinternalgainresistorsR1andR2areaccuratelydeterminedas24.7k.Inthiscase,theoperationalamplifiergainisaccuratelydeterminedbyRg.G=49.4k/Rg+1orRg=49.4k/(G-1)IVAD620TypicalUsage(1)Theinputbiascurrentisthecurrentrequiredtobiastheinputtransistoroftheopamp,anditmusthaveareturnloop.Therefore,whenamplifyinganAC-coupledsignalsourcelikeatransformer,eachinputpointmusthaveaDCpathtoground.AsshowninFigure4-6.Figure4.BiasCurrentLoopwithTransformerCoupledInputFigure5.BiasCurrentLoopforThermocoupleInputFigure6.BiasCurrentLoopWhenACCoupledInput(2)Allinstrumentamplifiersrectifythesignaloutsidethechannel.Ifasmallsignalisamplified,thisrectifiedvoltagebecomesaDCoffsetvoltage.ThestructureofAD620allowsafirst-levelfiltertobeinsertedbetweenthebaseandemitteroftheinputtransistortofilteroutunwantedrectifiedsignals,asshowninFigure5.RC=1/2f,fisgreaterthanorequaltothebandwidthofAD620,C150pF.Figure7.PrimaryFilterPrincipleDiagram(3)TheoutputvoltageofAD620isrelatedtothereferenceterminal.ConnectingtheREFterminaltoanappropriategroundingpointcansolvemanygroundingproblems.Manydataacquisitionsystemsseparatetheanaloggroundfromthedigitalground.Howcome?Justaimingtoisolatethelow-levelanalogsignalfromthenoisydigitalenvironment.Thegroundingprincipleisasfollows:eachindependentgroundloopminimizesthecurrentflowingfromthesensitivepointtotheground.Thesegroundloopsmustbeconnectedtogetheratsomepoint,usuallyontheADC.LetstakealookatFigure7.Thereferenceterminal5oftheAD620,thegroundterminalofthesample-and-holdAD585.Andthegroundterminaloftheanalogpowersupplyarerespectivelyconnectedtotheanaloggroundterminaloftheanalog-to-digitalconverterAD574A.Thegroundterminalofthedigitalpowersupplyisconnectedwiththedigitalgroundoftheanalog-to-digitalconverterAD574A.Finally,theanaloggroundanddigitalgroundareconnectedtotheAD574A.Inmanyapplications,shieldedcablesareoftenusedtoreducenoiseinterferenceattheinput.Properdrivetotheshieldcanreducethedifferentialphaseshiftcausedbycablecapacitanceandstraycapacitance.AndensurethattheACcommon-moderejectionratiodoesnotdrop.Figure8showsthedifferentialshielddriveconnection.Figure9showsthecommon-modeshielddriveconnection.Figure8.DifferentialShieldDriveFigure9.CommonModeShieldDriveVAD620Application5.1ApplicationinPhotoelectricDetectionPhotoelectricdetectioniswidelyusedintheindustry.Theprincipleofdesigningaphotoelectricdetectionsystemistoreducethetotalsystemnoisetoaminimum.Thenoiseofthesystemmainlyincludesdetectornoise,resistancenoise,andoperationalamplifiernoise.Becausetheyareindependentofeachother,thetotalnoisecanbeexpressedasUn(T)=[Un2(D)+Un2(L,F)+Un2(A)]1/2Intheformula:Un2(D)Detectornoisevarieswithdifferentphotodetectors.Theappropriatedetectorshouldbeselectedaccordingtothesystemrequirements;Un2(L,F)Loadresistancenoise;Un2(A)Opampnoise.ThenoiseofAD620isverysmall.Therefore,itisoftenusedasthepre-opamplifierofthephotoelectricdetectioncircuit.Takethephotodiodeasthedetectorasanexampletoillustrate.Here,supposethecurrentofthephotodiodeisID,thenID=ISC+IdarkIntheformula:ISCPhotocurrent.Itisproportionaltothelightintensity,whichistheeffectiveinformationdetected;IdarkDarkcurrent.ItconsistsofthecurrentonthesurfaceofthediodeandtheusualPNjunctioncurrent.Itbelongstoinvalidinformationinthesystem.Weneedtoeliminatetheinfluenceofdarkcurrent.TwodiodesD1andD2withthesameperformanceandtworesistorsR1andR2withtheresistancevalueofRareselectedtoformabridge.AsshowninFigure10.Figure10.PhotoelectricDetectionPreamplifierCircuitWhenD1haslightandD2hasnolight,theinputvoltageatbothendsoftheop-ampis(ISC+Idark)-R1-Idark-R=ISC-R1.Itisonlyrelatedtothephotocurrent,thuseliminatingtheinfluenceofthedarkcurrent.5.2ApplicationinUltrasonicTestingInthefieldofultrasonictesting,especiallywhenultrasonicwavespropagateinanon-uniformandattenuatedmedium,theechoafterencounteringtheinterfaceisveryweak.Ifageneralop-ampisusedforpre-processing,thenoiseisoftenlargeandeffectivesignalscannotbeobtained.ChoosingAD620asthepre-amplifiercircuithasasimpleconnectionandlownoise.AsshowninFigure11.Figure11.UltrasonicDetectionReceivingFrontCircuitVIConclusionAD620isahighprecisioninstrumentationamplifier.Intheapplication,wealsoneedtopayattentiontopreventtheblockageoftheamplifier.IfastrongDCsignalissuperimposedontheweaksignal,wemustsetupaseparationcircuit.Inthisway,theDCsignalcanbeseparated.FAQWhatisAD620?AD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyrequiresanexternalresistortosetthegain.Thegainrangeis1to10,000.CanIchangeAD620toAD623whenmakingMCUproducts?BothAD620andAD623aresingleinstrumentationamplifiers,andthepinarrangementisexactlythesame.Themaindifferenceis:AD620mustusepositiveandnegativepowersupplies,AD623canbeapositiveandnegativepowersupplyorasinglepowersupply.IftheoriginalboardisAD620,youcanreplaceitwith623;iftheoriginalboardisAD623,youmaynotbeabletoreplaceitwith620(itdependsonwhetherthepowersupplyoftheoriginalboardcircuitisdualpowersupplyorsinglepowersupply).AfterreplacingAD620andAD623insingle-chipproducts,theprogramcanworknormallywithoutmodification.WhatisthedifferencebetweenAD620BRandAD620AN?Theirpackagesaredifferent.WhatistheoutputresistanceofAD620?Howtoadjustit?AD620isakindoflowpowerconsumptioninstrumentamplifier,itsoutputresistanceisabout10K,thisistheinherentcharacteristicofthischip,generallyitisdifficulttoadjust.Ifyouhaverequirementsforoutputresistance,youcangenerallyuseanexternalcircuittosolveit.IsAD620apositivephaseamplificationorareversephaseamplification?AD620isaninstrumentamplifier,theoutputvoltageis[(Vin+)-(Vin-)]*gain.Ifthedesiredsignalis(Vin+)-(Vin-),thegainispositive,whichisequivalenttopositiveamplification.Conversely,ifthedesiredsignalis(Vin-)-(Vin+),thegainisequivalenttonegative,whichisequivalenttoreverseamplification.Whatisaninstrumentationamplifier?Instrumentationamplifier,animprovementofthedifferentialamplifier,hasaninputbuffer,doesnotrequireinputimpedancematching,sothattheamplifierissuitableformeasurementandelectronicinstruments

IDescriptionAD620isalow-power,high-precisioninstrumentationamplifier.BasedontheinformationprovidedbytheADcompany,thisblogintroducesthecharacteristicsandtypicalusageofAD620.Besides,thisblogalsointroducestheapplicationofAD620.Theapplicationsaremainlyaboutphotoelectricdetection,ultrasonictesting,etc.Figure1.AD620IDescriptionIIIntroductionIIIAD620PinoutandWorkingPrincipleIVAD620TypicalUsageVAD620Application5.1ApplicationinPhotoelectricDetection5.2ApplicationinUltrasonicTestingVIConclusionFAQOrdering&QuantityIIIntroductionAD620isalow-power,high-precisioninstrumentationamplifier.Anditcansettheamplificationfactorfrom1to1000withonlyanexternalresistor.Itissmallinsize,inan8-pinSOICorDIPpackage;thepowersupplyrangeis2.3V~18V;themaximumpowersupplycurrentisonly1.3mA.AD620hasgoodDCandACcharacteristics.Itsmaximuminputoffsetvoltageis50V,themaximuminputoffsetvoltagedriftis1V/℃,andthemaximuminputbiascurrentis2.0nA.WhenG=10,itscommon-moderejectionratioisgreaterthan93dB.Theinputvoltagenoiseisat1kHz,thepeak-to-peakvalueoftheinputvoltagenoiseis0.28Vintherangeof0.1Hz~10Hz,andtheinputcurrentnoiseisWhenG=1,itsgainbandwidthis120kHz,andthesettlingtimeis15s.Ingeneral,thecharacteristicsofAD620canbesummarizedasfollows:AD620canensuretheperformanceindicatorsrequiredforhigh-gainprecisionamplification.Forexample,lowoffsetvoltage,lowoffsetvoltagedrift,andlownoise,etc.;Withonlyoneexternalresistor,themagnificationcanbesetfrom1to1000;Smallsize,with8pins;Lowpowerconsumptionanditsmaximumsupplycurrentare1.3mA.IIIAD620PinoutandWorkingPrincipleThepinofAD620isshownasinFig.2,itsstructurediagramisshownasinFig.3.Figure2.AD620PinoutFigure3.AD620StructureDiagramAD620isamonolithicinstrumentamplifier.Itisdevelopedonthebasisoftheimprovementofthetraditionalthree-opamplifiercombination.TheinputtransistorsQ1andQ2providetheonlybipolardifferentialinput.Duetotheinternalsuperprocessing,itsinputoffsetcurrentis10timeslowerthannormal.ThroughthefeedbackoftheQ1-A1-R1loopandtheQ2-A2-R2loop,thecollectorcurrentsofQ1andQ2arekeptconstant.Thus,theinputvoltageisequivalenttothetwoendsoftheexternalresistorRg.AndthedifferentialamplificationfactorfromtheinputtotheA1/A2outputisG=(R1+R2)/Rg+1.TheunitygainsubtractorcomposedofA3eliminatesanycommon-modecomponents.Andthenitproducesasingle-channeloutputrelatedtothepotentialoftheREFpin.ThevalueofRgalsodeterminesthetransconductanceofthepreviousstageopamp.WhenRgdecreases,theamplificationfactorincreases.Andthetransconductancetotheinputtransistorgraduallyincreases.Thishasobviousadvantages:theincreaseintheamplificationfactorincreasestheopen-loopgain.Thus,theerrorrelatedtogainisreduced.Thegain-bandwidthproductdeterminedbyC1,C2andthepre-opamptransconductanceincreases.Thus,thefrequencyresponseisimproved.Theinputvoltagenoiseismainlydeterminedbythecollectorcurrentoftheinputtransistorandthebaseresistance.Andtheinputvoltagenoiseisreducedto.TheinternalgainresistorsR1andR2areaccuratelydeterminedas24.7k.Inthiscase,theoperationalamplifiergainisaccuratelydeterminedbyRg.G=49.4k/Rg+1orRg=49.4k/(G-1)IVAD620TypicalUsage(1)Theinputbiascurrentisthecurrentrequiredtobiastheinputtransistoroftheopamp,anditmusthaveareturnloop.Therefore,whenamplifyinganAC-coupledsignalsourcelikeatransformer,eachinputpointmusthaveaDCpathtoground.AsshowninFigure4-6.Figure4.BiasCurrentLoopwithTransformerCoupledInputFigure5.BiasCurrentLoopforThermocoupleInputFigure6.BiasCurrentLoopWhenACCoupledInput(2)Allinstrumentamplifiersrectifythesignaloutsidethechannel.Ifasmallsignalisamplified,thisrectifiedvoltagebecomesaDCoffsetvoltage.ThestructureofAD620allowsafirst-levelfiltertobeinsertedbetweenthebaseandemitteroftheinputtransistortofilteroutunwantedrectifiedsignals,asshowninFigure5.RC=1/2f,fisgreaterthanorequaltothebandwidthofAD620,C150pF.Figure7.PrimaryFilterPrincipleDiagram(3)TheoutputvoltageofAD620isrelatedtothereferenceterminal.ConnectingtheREFterminaltoanappropriategroundingpointcansolvemanygroundingproblems.Manydataacquisitionsystemsseparatetheanaloggroundfromthedigitalground.Howcome?Justaimingtoisolatethelow-levelanalogsignalfromthenoisydigitalenvironment.Thegroundingprincipleisasfollows:eachindependentgroundloopminimizesthecurrentflowingfromthesensitivepointtotheground.Thesegroundloopsmustbeconnectedtogetheratsomepoint,usuallyontheADC.LetstakealookatFigure7.Thereferenceterminal5oftheAD620,thegroundterminalofthesample-and-holdAD585.Andthegroundterminaloftheanalogpowersupplyarerespectivelyconnectedtotheanaloggroundterminaloftheanalog-to-digitalconverterAD574A.Thegroundterminalofthedigitalpowersupplyisconnectedwiththedigitalgroundoftheanalog-to-digitalconverterAD574A.Finally,theanaloggroundanddigitalgroundareconnectedtotheAD574A.Inmanyapplications,shieldedcablesareoftenusedtoreducenoiseinterferenceattheinput.Properdrivetotheshieldcanreducethedifferentialphaseshiftcausedbycablecapacitanceandstraycapacitance.AndensurethattheACcommon-moderejectionratiodoesnotdrop.Figure8showsthedifferentialshielddriveconnection.Figure9showsthecommon-modeshielddriveconnection.Figure8.DifferentialShieldDriveFigure9.CommonModeShieldDriveVAD620Application5.1ApplicationinPhotoelectricDetectionPhotoelectricdetectioniswidelyusedintheindustry.Theprincipleofdesigningaphotoelectricdetectionsystemistoreducethetotalsystemnoisetoaminimum.Thenoiseofthesystemmainlyincludesdetectornoise,resistancenoise,andoperationalamplifiernoise.Becausetheyareindependentofeachother,thetotalnoisecanbeexpressedasUn(T)=[Un2(D)+Un2(L,F)+Un2(A)]1/2Intheformula:Un2(D)Detectornoisevarieswithdifferentphotodetectors.Theappropriatedetectorshouldbeselectedaccordingtothesystemrequirements;Un2(L,F)Loadresistancenoise;Un2(A)Opampnoise.ThenoiseofAD620isverysmall.Therefore,itisoftenusedasthepre-opamplifierofthephotoelectricdetectioncircuit.Takethephotodiodeasthedetectorasanexampletoillustrate.Here,supposethecurrentofthephotodiodeisID,thenID=ISC+IdarkIntheformula:ISCPhotocurrent.Itisproportionaltothelightintensity,whichistheeffectiveinformationdetected;IdarkDarkcurrent.ItconsistsofthecurrentonthesurfaceofthediodeandtheusualPNjunctioncurrent.Itbelongstoinvalidinformationinthesystem.Weneedtoeliminatetheinfluenceofdarkcurrent.TwodiodesD1andD2withthesameperformanceandtworesistorsR1andR2withtheresistancevalueofRareselectedtoformabridge.AsshowninFigure10.Figure10.PhotoelectricDetectionPreamplifierCircuitWhenD1haslightandD2hasnolight,theinputvoltageatbothendsoftheop-ampis(ISC+Idark)-R1-Idark-R=ISC-R1.Itisonlyrelatedtothephotocurrent,thuseliminatingtheinfluenceofthedarkcurrent.5.2ApplicationinUltrasonicTestingInthefieldofultrasonictesting,especiallywhenultrasonicwavespropagateinanon-uniformandattenuatedmedium,theechoafterencounteringtheinterfaceisveryweak.Ifageneralop-ampisusedforpre-processing,thenoiseisoftenlargeandeffectivesignalscannotbeobtained.ChoosingAD620asthepre-amplifiercircuithasasimpleconnectionandlownoise.AsshowninFigure11.Figure11.UltrasonicDetectionReceivingFrontCircuitVIConclusionAD620isahighprecisioninstrumentationamplifier.Intheapplication,wealsoneedtopayattentiontopreventtheblockageoftheamplifier.IfastrongDCsignalissuperimposedontheweaksignal,wemustsetupaseparationcircuit.Inthisway,theDCsignalcanbeseparated.FAQWhatisAD620?AD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyrequiresanexternalresistortosetthegain.Thegainrangeis1to10,000.CanIchangeAD620toAD623whenmakingMCUproducts?BothAD620andAD623aresingleinstrumentationamplifiers,andthepinarrangementisexactlythesame.Themaindifferenceis:AD620mustusepositiveandnegativepowersupplies,AD623canbeapositiveandnegativepowersupplyorasinglepowersupply.IftheoriginalboardisAD620,youcanreplaceitwith623;iftheoriginalboardisAD623,youmaynotbeabletoreplaceitwith620(itdependsonwhetherthepowersupplyoftheoriginalboardcircuitisdualpowersupplyorsinglepowersupply).AfterreplacingAD620andAD623insingle-chipproducts,theprogramcanworknormallywithoutmodification.WhatisthedifferencebetweenAD620BRandAD620AN?Theirpackagesaredifferent.WhatistheoutputresistanceofAD620?Howtoadjustit?AD620isakindoflowpowerconsumptioninstrumentamplifier,itsoutputresistanceisabout10K,thisistheinherentcharacteristicofthischip,generallyitisdifficulttoadjust.Ifyouhaverequirementsforoutputresistance,youcangenerallyuseanexternalcircuittosolveit.IsAD620apositivephaseamplificationorareversephaseamplification?AD620isaninstrumentamplifier,theoutputvoltageis[(Vin+)-(Vin-)]*gain.Ifthedesiredsignalis(Vin+)-(Vin-),thegainispositive,whichisequivalenttopositiveamplification.Conversely,ifthedesiredsignalis(Vin-)-(Vin+),thegainisequivalenttonegative,whichisequivalenttoreverseamplification.Whatisaninstrumentationamplifier?Instrumentationamplifier,animprovementofthedifferentialamplifier,hasaninputbuffer,doesnotrequireinputimpedancematching,sothattheamplifierissuitableformeasurementandelectronicinstruments

IDescriptionThisblogintroducesapulsewidthmodulationtechnologywithTL494asthecontrolcore.AnditisappliedtoDCmotorcontrolsystem.Theworkingprincipleofthesystem,therealizationcircuitandthestructureandspecificapplicationofthePWMcontrolchipareanalyzedindetail.CatalogIDescriptionIIWorkingPrincipleandRealizationofControlSystem2.1HowSystemWorks2.2SelectionofPWMControlChip2.3RealizationCircuitofSystemIIISimulationResultsIVConclusionFAQOrdering&QuantityIIWorkingPrincipleandRealizationofControlSystem2.1HowSystemWorksThebasicdesignideaofthiscontrolsystemistouseastep-downchoppercircuitasshowninFigure1.Figure1.Step-downChopperCircuitanditsWaveformInthefigure,theDCpowersupplyisUd,andtheloadisamotor(M).Whentheswitchingdevice(VT)istriggeredandturnedon,theDCvoltageisappliedtothemotorforadurationoft1.Whenthefieldswitchingdeviceisturnedoff,thevoltageontheloadiszeroandlastsfort2time.IfwedefinethedutycycleT=t1+t2,andthedutycyclek=t/T,thewaveformdiagramandtheprincipleoftheDCchoppercircuitareasfollows:Theaveragevalue(Uo)ofthesystemoutputvoltageis:Theeffectivevalue(U)ofitsoutputvoltageis:Thepulsewidthmodulation(PWM)workingmodeadoptedbythissystemkeepsTunchangedandt1changes.TheprincipleblockdiagramofthecontrolsystemisshowninFigure2.Figure2.ControlSystemBlockDiagramThepowersupplyinthissystemmakesthemotorworkthroughthepowerdrivecircuit.Theon-offofthepowerdrivecircuitiscontrolledbythePWMcontrolchip.ThesystemsamplesthemotorcurrentfeedsitbacktothePWMcontrolchipandcomparesitwiththecurrentvalueofthecurrentcomparisoncircuit.TocontrolthePWMsignaloutputtoachievethepurposeofspeedregulation.ThesystemalsosamplesthepowersupplyvoltageandfeedsitbacktothePWMcontrolchip.Inthisway,itcanbecomparedwiththevoltagevalueofthevoltagecomparisoncircuittocontrolthePWMsignaloutputandachievetheeffectofUndervoltageprotection.WeusethecommonBUCKcircuitforthepowerdrivecircuitandPowerMOSFETfortheswitchtube.Theregulationofitsoutputvoltageisrealizedbycontrollingtheturn-ontimeofthedevice.Consideringtheinfluenceoftheinductanceofthemotor,theoutputcurrentisrelativelystableandtheenergyconsumptionislow.2.2SelectionofPWMControlChipInthecontrolcircuitofthemotorPWMcontrolsystem,theTL494chipisselected.TL494chiphasthefeaturesofstronganti-interferenceability,simplestructure,highreliabilityandlowprice.TheinternalcircuitofTL494(Figure3)consistsofthefollowingparts:Thereferencevoltagegeneratingcircuit;Oscillationcircuit;Intermittentadjustmentcircuit;Twoerroramplifiers;Pulsewidthmodulationcomparator;Outputcircuit;...Figure3.TL494InternalStructureAmongthem:Forpins1and2,theyarethenon-invertingandinvertinginputterminalsoferroramplifier1.Forpin3,itisphasecorrectionandgainscontrol.Forpin4,itisanintermittentperiodofconditioning,andthecut-offtimecanbechangedfrom2%to100%whenavoltageof0~3.3Visappliedtoit.Forpins5and6,theyareusedtoconnectexternaloscillationresistorRTandoscillationcapacitorCTtodeterminethefrequencyfoscofthesawtoothwavegeneratedbytheoscillator.Where:ThevaluerangeofRTandCT:RT=5~100kQ,CT=0.001~0.1F.Pin7isthegroundterminal;Forpins8,9and11,10,theyarethecollectorandemitterofthetwofinaloutputtransistorsinsideTL494;For12feet,itisthepowersupplyterminal;Forpin13,itistheoutputcontrolterminal.Whenthispinisgrounded,itisaparallelsingle-endedoutputmode.Whenpin14isconnected,itisapush-pulloutputmode;For14feet,itisthe5Vreferencevoltageoutputterminal,themaximumoutputcurrentis10mA;For15and16pins,theyaretheinvertingandnon-invertinginputterminalsoftheerroramplifier2.2.3RealizationCircuitofSystemTheconcreterealizationcircuitofthiscontrolsystemisshowninFig.4.Thesystemusescurrentnegativefeedbacktotrackthespeedofthemotor.Atthesametime,throughthenegativefeedbackofthevoltageofthepowersupply,thesystemhasthefunctionofundervoltageprotection.Figure4.SystemImplementationCircuitThemotorcurrentisdetectedandfedbacktopin1oftheerroramplifier1oftheTL494,comparedwiththecurrentreferencesignalofpin2tocontrolthePWMoutputofTL494.Soastorealizethefunctionofregulatingthespeedofthemotor.Byadjustingtheresistancevalueoftheadjustableresistor(RES1).Thatis,changethesizeofthesetcurrentreferencesignaltoadjustthedutycycleofthePWMoutputsignal.Soastoachievethepurposeofadjustingthemotorspeed.Bysamplingthevoltageofthepowersupply,itisfedbacktopin15oftheinternalerroramplifier2ofTI494.Thencomparewiththevoltagereferencesignalofpin16tocontrolthePWMoutputofTL494.Soastorealizetheundervoltageprotectionfunctionofthesystem.ThesystempowerisdrivenbyPowerMOSFET,whichhasahighinputimpedanceandcanbedirectlydrivenbyatransistor.Pin13ofTI494isusedtocontroltheoutputmode.Inthissystem,choosetoinputthisendaslowlevel.Atthistime,theflip-flopsQ1andQ2intheTL494donotwork,thetwooutputsarethesame,thefrequencyisthesameastheoscillatorfrequency,andthemaximumdutycycleis98%.IIISimulationResultsInordertoverifytheeffectivenessofthesystem,wecansimulatethecircuitoftheabove-mentionedDCmotorcontrolsystembasedonPWMtechnologybycomputer.WesetthesystemspowersupplyvoltageUcc=12V,DCmotorratedparameters:Un=12V,In=15A,4poles,armatureresistanceRa=0.21Q,momentofinertiaJ=0.57kg㎡.ThroughchangingtheadjustableresistanceRES1ofthecontrolcircuittorealizethedifferentdutyratioofthesystemoutput.Whentheoutputdutyratiois0.2,0.65/0.8,thevoltageandcurrentwaveformsofthemotorareshowninFigure5.Figure5.MotorVoltageandCurrentWaveformItcanbeseenfromFigure5thatwhenoutputtingdifferentdutyratios,thevoltageandcurrentwaveformsofthemotorarestable,whichisconducivetothelong-termstableoperationofthemotor.ThisshowsthattheTL494-basedPWMcontroltechnologyintroducedinthisarticleisfeasibleinpracticalapplicationsandrunsstably.IVConclusionThisblogsummarizesaPWMcontroltechnologybasedontheTL494chip.Thesimulationresultsshowthatthesystemhasasimplestructure,lowenergyconsumption,andstableoperation.AndthecharacteristicsoftheTL494chiphavebeenfullyutilizedsothatthesystemhastheadvantagesofundervoltageprotection.FAQWhatisTL494?TL494isaPWMcontrollerICusedforpowerelectronicscircuits.Itcomprisesofon-chiptwoerroramplifiersanoscillatorwithadjustablefrequencyfeature,anoutputflip-flophavingpulsesteeringcontrol,andanoutputcontrolcircuitwithfeedback.WhatisthedetaileddescriptionofTL494?TheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.WhatareTL494productfeatures?CompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeWhatisPWMIC?TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology....ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.HowdoesPWMICwork?Asitsnamesuggests,pulsewidthmodulationspeedcontrolworksbydrivingthemotorwithaseriesofON-OFFpulsesandvaryingthedutycycle,thefractionoftimethattheoutputvoltageisONcomparedtowhenitisOFF,ofthepulseswhilekeepingthefrequencyconstant.WhichICisbetterforabuckconverter,TL494orUC3843?TheymainlydifferintypeofcontrolTL494=voltagemodecontrol(Oneloopcontrol).whileUC3843usescurrentmodecontrol(Nestedloopcontrol,withainner/fastcurrentloopandanotherouter/slowervoltageloop)Typicallyvoltagemodeareusedinmultipleoutputconverterswithgoodcross-regulation.CurrentmodewhenyouwanttoparallelmultipleconverterstomakeasingleconverterwithhighercurrentratingTL494isaverypopularIC.IfyouhavesimplerequirementsTL494isrecommendedHowdoIproperlysetthefeedbackpinonaTL494SMPSIC?Thefeedbackpinistheoutputofbotherroramplifiers,usedincomparingandadjustingtheoutputpulsewidthtotheDCcontrolvoltage.OnvariouscircuitsIhavelookedup,theop-ampconnectedtopins23areusedtosetthegainofthefeedbackloop,using2resistorswithoneresistorconnectingto2.5Vpotentialdivideron5Vreferencevoltage.Withtheotherconnectingtotheoutput(viasuitableisolation)Thegainappearstobesetat101,usinga51kfeedbackwith510ohmstothe2.5Vreference.Itisusedtocontrolthegainofthefeedbackvoltage.NoliteratureIhaveyetfound,givesanindicationonhowthisgainbeset,exceptagraphshowinganopenloopgainof1000,presumablythegainissetforthebeststability,althoughtherewillalsobeatimeconstant.WhyistherenofrequencycompensationrequiredinTIsTL494examplebuckregulatordesign(operationalamplifier,buckphase,shiftphase,margin,TL494,electronics)?ItsafixedfrequencyPWMcontrollerwithinternaldeadtimetimer.Frequencycompensationisnotrequired.Takealookatthedatasheet.HowtouseTL494?DescriptionTL494wasdesignedandlaunchedbyTexasInstrumentsintheearly1980s.Itwaswidelyacceptedbythemarketimmediatelyafteritwaslaunched,especiallyontheATXhalf-bridgepowersupplyofPCs.Untiltoday,aconsiderableproportionofPCpowersuppliesarestillbasedontheTL494chip.HowtoTestTL494NCatalogDescriptionComponentDatasheetTL494PinoutTL494ParameterFeaturesAdvantagesApplicationsTL494SimplifiedBlockDiagramTL494PackageandPinsFunctionalBlockDiagramWheretouseTL494HowtouseTL494TL494TypicalApplicationFAQOrdering&QuantityComponentDatasheetDatasheetTL494Pulse-Width-ModulationControlCircuitsdatasheet(Rev.H)Applicationnotes1IsolatedMultipleOutputFlybackConverterDesignUsingTL494Applicationnotes2DesigningSwitchingVoltageRegulatorsWiththeTL494(Rev.E)TL494PinoutPinDescriptionNameNO.1IN+1Noninvertinginputtoerroramplifier11IN2Invertinginputtoerroramplifier12IN+16Noninvertinginputtoerroramplifier22IN-15Invertinginputtoerroramplifier2C18CollectorterminalofBJToutput1C211CollectorterminalofBJToutput2CT5CapacitorterminalusedtosetoscillatorfrequencyDTC4Dead-timecontrolcomparatorinputE19EmitterterminalofBJToutput1E210EmitterterminalofBJToutput2FEEDBACK3InputpinforfeedbackGND7GroundOUTPUTCTRL13Selectssingle-ended/paralleloutputorpush-pulloperationREF145-VreferenceregulatoroutputRT6ResistorterminalusedtosetoscillatorfrequencyVCC12PositiveSupplyTL494ParameterTopologyBoost,Buck,Flyback,Forward,Full-Bridge,Half-Bridge,Push-PullControlmethodVoltageVCC(Min)(V)7VCC(Max)(V)40Dutycycle(Max)(%)45UVLOthresholdson/off(V)Frequency(Max)(kHz)300Operatingtemperaturerange(C)-40to85,0to70Gatedrive(Typ)(A)0.2FeaturesAdjustableSwitchingFrequency,DeadTimeControl,ErrorAmplifier,Multi-topologyRatingCatalogFeaturesCompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeInternalRegulatorProvidesaStable5-VReferenceSupplyWith5%ToleranceCircuitArchitectureAllowsEasySynchronizationAdvantagesTheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.TheTL494Cdeviceischaracterizedforoperationfrom0Cto70C.TheTL494Ideviceischaracterizedforoperationfrom40Cto85C.ApplicationsDesktopPCsMicrowaveOvensPowerSupplies:AC/DC,Isolated,WithPFC,90WServerPSUsSolarMicro-InvertersWashingMachines:Low-EndandHigh-EndE-BikesPowerSupplies:AC/DC,Isolated,NoPFC,90WPower:Telecom/ServerAC/DCSupplies:DualController:AnalogSmokeDetectorsSolarPowerInvertersTL494SimplifiedBlockDiagramTL494PackageandPinsPackagePinsSizePDIP(N)16181mm19.3x9.4SOIC(D)1659mm9.9x6SOP(NS)1680mm10.2x7.8TSSOP(PW)1622mm4.4x5FunctionalBlockDiagramWheretouseTL494TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology.TL494canbeusedtoprovideaconstantcurrentbyvaryingtheoutputvoltagetotheload.ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.SoifyouarelookingforanICtoproducePWMsignalsforcontrollingapowerswitchbasedonthecurrentflowingthroughthecircuit,thenthisICmightbetherightchoiceforyou.HowtouseTL494AtestcircuitfromtheTL494datasheetisshownbelow.NoninvertingpinsareconnectedtotheRefpinwhileinvertingpinsareconnectedtotheground.TestinputsaregiventoDTCandFEEDBACKpins.Externalcapacitorandresistorareconnectedtopin56tocontroltheoscillatorfrequency.Theerroramplifiercomparesasampleofthe5-VoutputtothereferenceandadjuststhePWMtomaintainaconstantoutputcurrentTL494TypicalApplicationSwitchingandControlSectionsInputPowerSourceError-AmplifierSectionCurrent-LimitingCircuitSoft-StartCircuitSwitchingCircuitPower-SwitchSectionFAQWhatisTL494?TL494isaPWMcontrollerICusedforpowerelectronicscircuits.Itcomprisesofon-chiptwoerroramplifiersanoscillatorwithadjustablefrequencyfeature,anoutputflip-flophavingpulsesteeringcontrol,andanoutputcontrolcircuitwithfeedback.WhatisthedetaileddescriptionofTL494?TheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.WhatareTL494productfeatures?CompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeWhatisPWMIC?TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology....ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.HowdoesPWMICwork?Asitsnamesuggests,pulsewidthmodulationspeedcontrolworksbydrivingthemotorwithaseriesofON-OFFpulsesandvaryingthedutycycle,thefractionoftimethattheoutputvoltageisONcomparedtowhenitisOFF,ofthepulseswhilekeepingthefrequencyconstant.WhichICisbetterforabuckconverter,TL494orUC3843?TheymainlydifferintypeofcontrolTL494=voltagemodecontrol(Oneloopcontrol).whileUC3843usescurrentmodecontrol(Nestedloopcontrol,withainner/fastcurrentloopandanotherouter/slowervoltageloop)Typicallyvoltagemodeareusedinmultipleoutputconverterswithgoodcross-regulation.CurrentmodewhenyouwanttoparallelmultipleconverterstomakeasingleconverterwithhighercurrentratingTL494isaverypopularIC.IfyouhavesimplerequirementsTL494isrecommendedHowdoIproperlysetthefeedbackpinonaTL494SMPSIC?Thefeedbackpinistheoutputofbotherroramplifiers,usedincomparingandadjustingtheoutputpulsewidthtotheDCcontrolvoltage.OnvariouscircuitsIhavelookedup,theop-ampconnectedtopins23areusedtosetthegainofthefeedbackloop,using2resistorswithoneresistorconnectingto2.5Vpotentialdivideron5Vreferencevoltage.Withtheotherconnectingtotheoutput(viasuitableisolation)Thegainappearstobesetat101,usinga51kfeedbackwith510ohmstothe2.5Vreference.Itisusedtocontrolthegainofthefeedbackvoltage.NoliteratureIhaveyetfound,givesanindicationonhowthisgainbeset,exceptagraphshowinganopenloopgainof1000,presumablythegainissetforthebeststability,althoughtherewillalsobeatimeconstant.WhyistherenofrequencycompensationrequiredinTIsTL494examplebuckregulatordesign(operationalamplifier,buckphase,shiftphase,margin,TL494,electronics)?ItsafixedfrequencyPWMcontrollerwithinternaldeadtimetimer.Frequencycompensationisnotrequired.Takealookatthedatasheet.HowtouseTL494?

OPA4227

I.DesriptionInthefieldofmeasurementandcontrol,itisoftenencounteredthattheoutputsignalofthemonitoredobjectissmall,anditisdifficulttodirectlycollectit.Generally,itneedstobeamplifiedbeforeprocessing.Thisarticleintroducesamethodofimplementingasmallsignalacquisitionsystem.Thesmallestsystemisrealizedbyusingthesingle-chipSTC25A60S2withA/Dconversionfunctionandtheeasy-to-useamplifierAD620withpreciseamplificationfunction.Thesystemdesignandimplementationarediscussedandtheacquisitionisintroducedindetail.Theprocessofsmallsignal,andgivespracticalapplicationexamples,aswellastheapplicationofsmallsignalacquisitioninrelatedfields.AD620CatalogI.DesriptionII.AD620IntroductionIII.IntroductiontoSTC12C5A60S2IV.SystemHardwareDesign4.1SystemPrincipleBlockDiagram4.2PowerSupplyCircuitDesign4.3SignalConditioningCircuit4.4SystemDecouplingCircuit4.5RealizationofA/DConversion4.6Follow-upWorkV.PracticalApplicationVI.ConclusionFAQOrdering&QuantityII.AD620IntroductionAsamonolithicinstrumentamplifier,AD620haslowpowerconsumption,achipwithhighgainthroughexternalresistors,andfeatureslowinputdriftandtemperaturedrift.AD620isdevelopedfromthetraditionalthreeoperationalamplifiers,butsomeofthemainperformanceisbetterthanthedesignoftheinstrumentamplifiercomposedofthreeoperationalamplifiers,suchaswidepowersupplyrange(2.3~18V),smalldesignvolume,andverypowerconsumptionLow(themaximumpowersupplycurrentisonly1.3mA),soitissuitableforlow-voltage,low-powerapplications.Figure1SchematicdiagramofAD620principleThemonolithicstructureandlasercrystaladjustmentofAD620allowcircuitcomponentstobecloselymatchedandtracked,therebyensuringtheinherenthighperformanceofthecircuit.AD620isathree-op-ampintegratedinstrumentationamplifierstructure.Inordertoprotectthehighprecisionofgaincontrol,theinputtransistorprovidesasimpledifferentialbipolarinput,andusestheprocesstoobtainalowerinputbiascurrent.Throughtheinputstageinternalop-ampThefeedbacktokeepthecollectorcurrentoftheinputtransistorconstant,andtheinputvoltageisaddedtotheexternalgaincontrolresistorRG.ThetwointernalgainresistorsofAD620are24.7k8,sothegainequationis:G=49.4k/RG+1(1)Fortherequiredgain,theexternalcontrolresistancevalueis:RG=49.4/(G-1)k(2)III.IntroductiontoSTC12C5A60S2STC12C5A60S2isanewgeneration8051single-chipmicrocomputerwithA/Dconversionfunction.Theinstructioncodeisfullycompatiblewiththetraditional8051,butthespeedis8-12timesfaster.With8channelsofhigh-speed10-bitinputA/Dconversion(250k/s),itcanbeusedfortemperaturedetection,batteryvoltagedetection,keyscanning,spectrumdetection,etc.TheusercansetanychannelasA/Dconversion,andtheportsthatdonotneedtobeusedasA/DcancontinuetobeusedasI/Oports.Itscharacteristicsareasfollows:Figure2STC12C5A60S2(1)On-chipintegrated1280bytesRAM;(2)WithEEPROMfunction(STC12C5A62S2/AD/PWMwithoutinternalEEPROM);(3)Enhanced8051CPU,1T,singleclock/machinecycle,instructioncodeisfullycompatiblewithtraditional8051;(4)InternalintegratedMAX810dedicatedresetcircuit(whentheexternalcrystalisbelow12M,theresetpincanbedirectlyconnectedtothegroundwith1Kresistance);(5)Userapplicationspace8K/16K/20K/32K/40K/48K/52K/60K/62Kbytes;(6)ISP(In-SystemProgrammable)/IAP(In-ApplicationProgrammable),noneedforadedicatedprogrammer,noneedforadedicatedemulator,youcandownloadtheuserprogramdirectlythroughtheserialport(P3.0/P3.1),andonepiececanbecompletedinafewseconds;(7)STC12C5A60S2serieshavedualserialports,onlythosewiththeS2logosuffixhavedualserialports,RxD2/P1.2(canbesettoP4.2byregister),TxD2/P1.3(canbesettoP4.3byregister);(8)GeneralI/Oports(36/40/44),afterreset,theyare:quasi-bidirectionalport/weakpull-up(normal8051traditionalI/Oport),whichcanbesettofourmodes:quasi-bidirectionalport/weakPull-up,push-pull/strongpull-up,onlyinput/highimpedance,open-drain,eachI/Oportdrivecapacitycanreach20mA,butthewholechipshouldnotexceed120mA;(9)A/Dconversion,10-bitprecisionADC,8channelsintotal,conversionspeedupto250K/S(250,000timespersecond),universalfull-duplexasynchronousserialport(UART),becausetheSTC12seriesishigh-speed8051,canreusetimerorPCAsoftwaretorealizemultipleserialports.IV.SystemHardwareDesign4.1SystemPrincipleBlockDiagramGenerallyspeaking,beforethesignalisused,itneedstobefilteredandthenamplified,oramplifiedandthenfiltered,andthenobtained/perceivedbymeanssuchasA/D.Forsmallsignals,thesignalamplitudeisonlyafewmillivoltsorevensmaller.Iffilteredfirst,usefulsignalsmaybefilteredout.Therefore,inthiscase,youneedtoamplifyfirst,thenfilter,andthenperformA/Dconversionorotherprocessing.Accordingtothecharacteristicsofthissystem,theinterferenceinthesystemcanbeignored,sothesignalfilteringlinkisnotconsidered.Therefore,thesystemismainlyrealizedthroughthreeimportantlinks:signalextraction,signalamplification,andA/Dacquisition.Thedatageneratedinthethirdlinkcanguidepeoplesworkordisplayrelevantinformation.TheblockdiagramoftheentiresystemisshowninFigure3.Figure3Systemblockdiagram4.2PowerSupplyCircuitDesignAD620amplifiercanusesinglepowersupplyordualpowersupply,butwhenusingdualpowersupply,itsperformanceisbetterthansinglepowersupply.Inintegratedcircuitdesign,singlepowersupplyiseasytoimplement,butconsideringtheworkingperformanceofthechip,dualpowersupplyisusedinthissystem.UsetheICL7660Schiptoconvertanexternalsinglepowersupplyintoadualpowersupply.ICL7660Sisavoltageconversionchipthatcanrealizethefunctionofconvertingapositivevoltagetoanegativevoltage,anditsperipheralcircuitisrelativelysimple.ThespecificcircuitisshowninFigure4.Figure4PowersupplyimplementationschematicdiagramTheotherchipsinthesystemarepoweredbyasingle5Vpowersupply,andtheconnected5Vpowersupplycanbeusedwithoutanyprocessing,whichisnotdescribedhere.4.3SignalConditioningCircuitTheactualweaksignalisgenerallymVlevelorevensmaller.Beforeprocessing,itneedstobeamplifiedandthenA/Dcollected.AccordingtotheA/DfunctionofSTC12C5A60S2,itisnecessarytoaccuratelyamplifythesignaltoreachtheVlevel,sotheAD620amplifierisused.AD620hasagoodamplificationeffecton2inputdifferentialsignals.Inpracticalapplications,thesignalsaregenerallygeneratedbyelectricbridges.Inordertorealizesignalamplification,AD620needsanexternalresistor,whichdeterminestheamplificationfactortogetherwiththeinternalresistor.SupposethemagnificationisG,thenthereisthefollowingformula.G=(RG/R1)+1(1)canalsobewrittenasthefollowingformula:G=49.4k/RG+1(2)1)Intheformula,RGistheinternalresistanceofAD620,andR1istheexternalresistance.Itcanbeseenfromtheformulas(1)and(2)thatthesizeofRGintheformula(1)is49.4k.Theconditionedsignalisoutputthroughthe6-pinofAD620.Atthistime,itcanbedirectlyconnectedtotheA/Dconversionchiptorealizedatacollection.Itcanbereducedbythecorrespondingmultiplewhenusingit.TheprincipleofsignalconditioningisshowninFigure5.Figure5Signalconditioningcircuit4.4SystemDecouplingCircuitSincethesystemmainlyrealizessmallsignalamplificationandA/Dconversionafteramplification,thechipthatcompletestheA/Dfunctionofthissystem,namelySTC12C5A60S2,usesitsownworkingpowersupplyasthereferencevoltage.Inordertoensuretheconsistencyoftheconversionresults,itisnecessarytoensurethepowersupplyvoltagestability.Tofilterouttheinterferenceinthepowersupply,itcanbefilteredbymultiplecapacitorsinparallel.Afterthecapacitorsareconnectedinparallel,thecapacitancevalueincreases,buttheequivalentresistanceinsidethecapacitorisreducedduetotheparallelconnection,whichisbeneficialtoreducetheloss.Therefore,manycapacitorsareusedinparallel,andtherealizationprincipleisshowninFigure6.Figure6Powerdecouplingcircuit4.5RealizationofA/DConversionAsmentionedearlier,STC12C5A60S2isasingle-chipmicrocomputerwithA/Dconversionfunction,whichisconvenient,simple,andmulti-functional.ItsA/Dconversiononlyrequires90clockcycles(relatedtoitsoperatingfrequency)atthefastest.ThissystemUseittoachieveA/Dconversion.STC12C5A60S2usesportP1asan8-channelA/Dconversioninputinterface.Whenusingit,youonlyneedtosetitasananaloginterface.Bysettingthecorrespondingregister,theA/Dconversioncanbecompleted.Theunusedpinscanstillbeusedasordinarytubes.ThissystemrealizestheA/Dconversionofoneinputsignal,soitonlyneedstosetone.Inthissystem,P1.0portisusedasthesignalinputport.ThissystemrealizestheprincipleofA/DconversionasshowninFigure7.Figure7A/Dacquisitioncircuit4.6Follow-upWorkAftertheA/Dconversioniscompleted,dataanalysisisrequired.Generally,itcanbesenttotheuppercomputerthroughthecommunicationport(usuallyserialport),andthedataisprocessedbytheuppercomputer.Accordingtothedifferentcharacteristicsofthespecificsystem,thedataprocessingmethodsarealsodifferent,soitsnoneedtodiscussthemindetailhere.Table1ADconversiondataandactualdataAfterthesystemperformsA/Dconversiononsignalsofdifferentsizes,aseriesofactualdataandtheoreticaldataareobtained,asshowninTable1.DrawthecurveofA/DdatathroughExcel,andfoundthatthesystemA/Dconverterhasgoodlinearity.AsshowninFigure8.Figure8LinearityofA/DconverterV.PracticalApplicationThesmallsignalconditioning,A/Dconversion,andprocessingmethodsarediscussedinmoredetailabove.Thespecificapplicationisintroducedbelowthroughexamples.Asakindofsensingelement,resistancestraingaugeiscommonlyusedtomonitorthedeformationoftheobject.Generally,thestraingaugeisattachedtothesidepointofthecomponent.Afterthecomponentisstressed,duetothestrainofthemeasuringpoint,theresistancechanges,resultinginaweakvoltagechange.Thevoltagechangecanbecalculatedtoobtainthedeformationdegreeofthecomponent,soastoachievethepurposeofmonitoringtheconditionofthecomponentandguidetherelevantengineeringpersonneltodealwithit.Thissystemcanbeappliedtothevoltagegeneratedbytheelectricbridge.AschematicdiagramoftheelectricbridgeisshowninFigure9.Inthefigure,R4,R3,R1,andR2arethefourarmsofthebridge,R4andR3arefixedresistancesofimpedance,andR1andR2areinOneisaresistorwhoseresistancevaluechangesafterbeingstressed.R4andR3havethesameresistancevalue,andR1andR2havethesameresistancevaluewhentheyarenotstressed.Inthecaseofnoforce,thetwopointsofthebridge3and4areequipotential,thatis,thepotentialdifferenceis0.IfitisinputasAD620,theinputsignalisconsideredtobe0,andthebridgeissaidtobebalancedatthistime.WhentheforceofR1orR2changes,theresultofthechangeisreflectedinitsresistancevalue,whichcanbeobtainedbyOhmslaw.Thepotentialatpoints3and4isdifferent,thatis,thereisapotentialdifference.Atthistime,thebridgeisoutofbalance,butatthistimeThesignalisveryweakandcannotbecollecteddirectly.Therefore,thesignalisamplifiedthroughthesignalconditioningcircuitmentionedinthearticle,thatis,points3and4inthebridgeareconnectedtopins2and3ofAD620,afteramplification,thenA/Dacquisitionisperformed.Figure9SchematicdiagramofelectricbridgeThissystemusesasimpleelectricbridgebuiltbyitselfduringsimulation,asshowninFigure10.Figure10SimpleelectricbridgeByadjustingR2inthefigure,differentweaksignalsaregenerated,andthesimplebridge1and2areconnectedtothesignalconditioningcircuit,andthenafterA/Dconversion,weaksignalacquisitioncanberealized.The1,2endsofthesimpleelectricbridgecorrespondtothe3and4endsinthefigure.Inthissimulation,adjustR2togenerateabout5.35mVatbothendsof1,2andadjusttheexternalresistanceinthesignalconditioningcircuitto160.7.Thecalculatedmagnificationisabout308.4times,andtheA/Dreferencevoltageis4.256VBymeasuringtheoutputofAD620,itcanbeobtainedthatthevoltageis1.645V,andthemagnificationfactorG=1.647V/5.35mV308canbecalculated.Itcanbeseenthatthemagnificationeffectisgood(afterremovingthemagnificationeffect,theerrorisonlynVlevel).ThroughmultipleA/Dconversions,thereturnedresultsareallaround0x018B,whichprovesthatthesystemhashighcredibility(ithasbeenusedinactualsystems).VI.ConclusionThisarticledescribesindetailthedesignandimplementationofsmallsignalacquisitionsystemsfromchipselection,circuitdesign,etc.,suchas8-bitsingle-chipSTC12C5A60S2asthecontrollerandA/Dconverter;AD620asthemainchipofthesignalconditioningcircuit;electricbridgeprincipleetc.Throughthetest,thecircuithasrealizeditsfunctionwell,andithasaccomplishedtheexpectedgoalexcellentlyintheactualsystem,whichhascertainpracticalvalue.FAQWhatisAD620?AD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyrequiresanexternalresistortosetthegain.Thegainrangeis1to10,000.CanIchangeAD620toAD623whenmakingMCUproducts?BothAD620andAD623aresingleinstrumentationamplifiers,andthepinarrangementisexactlythesame.Themaindifferenceis:AD620mustusepositiveandnegativepowersupplies,AD623canbeapositiveandnegativepowersupplyorasinglepowersupply.IftheoriginalboardisAD620,youcanreplaceitwith623;iftheoriginalboardisAD623,youmaynotbeabletoreplaceitwith620(itdependsonwhetherthepowersupplyoftheoriginalboardcircuitisdualpowersupplyorsinglepowersupply).AfterreplacingAD620andAD623insingle-chipproducts,theprogramcanworknormallywithoutmodification.WhatisthedifferencebetweenAD620BRandAD620AN?Theirpackagesaredifferent.WhatistheoutputresistanceofAD620?Howtoadjustit?AD620isakindoflowpowerconsumptioninstrumentamplifier,itsoutputresistanceisabout10K,thisistheinherentcharacteristicofthischip,generallyitisdifficulttoadjust.Ifyouhaverequirementsforoutputresistance,youcangenerallyuseanexternalcircuittosolveit.IsAD620apositivephaseamplificationorareversephaseamplification?AD620isaninstrumentamplifier,theoutputvoltageis[(Vin+)-(Vin-)]*gain.Ifthedesiredsignalis(Vin+)-(Vin-),thegainispositive,whichisequivalenttopositiveamplification.Conversely,ifthedesiredsignalis(Vin-)-(Vin+),thegainisequivalenttonegative,whichisequivalenttoreverseamplification.Whatisaninstrumentationamplifier?Instrumentationamplifier,animprovementofthedifferentialamplifier,hasaninputbuffer,doesnotrequireinputimpedancematching,sothattheamplifierissuitableformeasurementandelectronicinstrumentsDescriptionThe2N7000isaN-ChannelEnhancementModeFieldEffectTransistor,a.k.a.MOSFETforvoltagecontrolledsmallsignalswitching.2N7000NChannelEnhancementModeMOSFETSwitchCircuitBasicsCatalogDescription2N7000Pinout2N7000Parameters2N7000Features2N7000Applications2N7000Advantage2N7000SwitchingWaveformsandTestCircuit2N7000PackageInformation2N7000PopularitybyRegion2N7000AlternativesHowtouse2N7000Wheretouse2N7000ProductManufacturerFAQOrdering&Quantity2N7000PinoutPinNumberPinNameDescription1SourceCurrentflowsoutthroughSource2GateControlsthebiasingoftheMOSFET3DrainCurrentflowsinthroughDrain2N7000ParametersConfigurationSINGLEWITHBUILT-INDIODEContinuousDrainCurrent(ID)200mADrainCurrent-Max(ID)0.2ADraintoSourceResistance5RDraintoSourceVoltage(Vdss)60VDrain-sourceOnResistance-Max5DSBreakdownVoltage-Min60VElementConfigurationSingleFeedbackCap-Max(Crss)5pFFETTechnologyMETAL-OXIDESEMICONDUCTORGatetoSourceVoltage(Vgs)30VHeight5.33mmJEDEC-95CodeTO-92JESD-30CodeO-PBCY-T3LeadFreeLeadFreeLength5.21mmManufacturerMicrochipTechnologyIncManufacturerPartNumber2N7000-GP003MaxPowerDissipation1WNumberofChannels1NumberofElements1NumberofTerminals3OperatingModeENHANCEMENTMODEOperatingTemperature-Max150COperatingTemperature-Min-55CPackageTO-92-3PartLifeCycleCodeActivePolarity/ChannelTypeN-CHANNELReachComplianceCodeCompliantREACHSVHCNoSVHCRiskRank5.56SurfaceMountNOTerminalFormTHROUGH-HOLETerminalPositionBOTTOMTransistorApplicationSWITCHINGTransistorElementMaterialSILICONVoltageRating(DC)60VWeight0.00776ozWidth4.19mm2N7000FeaturesFreefromsecondarybreakdownLowpowerdriverequirementEaseofparallelingLowCISSandfastswitchingspeedsExcellentthermalstabilityIntegralsource-draindiodeHighinputimpedanceandhighgain2N7000ApplicationsMotorcontrolsConvertersAmplifiersSwitchesPowersupplycircuitsDrivers(relays,hammers,solenoids,lamps,memories,displays,bipolartransistors,etc.)The2N7000hasbeenreferredtoasaFETlingtonandasanabsolutelyidealhackerpart.ThewordFETlingtonisareferencetotheDarlington-transistor-likesaturationcharacteristic.Atypicaluseofthesetransistorsisasaswitchformoderatevoltagesandcurrents,includingasdriversforsmalllamps,motors,andrelays.Inswitchingcircuits,theseFETscanbeusedmuchlikebipolarjunctiontransistors,buthavesomeadvantages:highinputimpedanceoftheinsulatedgatemeansalmostnogatecurrentisrequiredconsequentlynocurrent-limitingresistorisrequiredinthegateinputMOSFETs,unlikePNjunctiondevices(suchasLEDs)canbeparalleledbecauseresistanceincreaseswithtemperature,althoughthequalityofthisloadbalanceislargelydependentontheinternalchemistryofeachindividualMOSFETinthecircuitThemaindisadvantagesoftheseFETsoverbipolartransistorsinswitchingarethefollowing:susceptibilitytocumulativedamagefromstaticdischargepriortoinstallationcircuitswithexternalgateexposurerequireaprotectiongateresistororotherstaticdischargeprotectionNon-zeroohmicresponsewhendriventosaturation,ascomparedtoaconstantjunctionvoltagedropinabipolarjunctiontransistor2N7000AdvantageTheSupertex2N7000isanenhancement-mode(normallyoff)transistorthatutilizesaverticalDMOSstructureandSupertexswell-provensilicon-gatemanufacturingprocess.Thiscombinationproducesadevicewiththepowerhandlingcapabilitiesofbipolartransistors,andthehighinputimpedanceandpositivetemperaturecoefficientinherentinMOSdevices.CharacteristicofallMOSstructures,thisdeviceisfreefromthermalrunawayandthermally-inducedsecondarybreakdown.SupertexsverticalDMOSFETsareideallysuitedtoawiderangeofswitchingandamplifyingapplicationswhereverylowthresholdvoltage,highbreakdownvoltage,highinputimpedance,lowinputcapacitance,andfastswitchingspeedsaredesired.2N7000SwitchingWaveformsandTestCircuit2N7000PackageInformation3-LeadTO-92PackageOutline(N3)FrontView3-LeadTO-92PackageOutline(N3)SideView3-LeadTO-92PackageOutline(N3)BottomView2N7000PopularitybyRegion2N7000AlternativesManufacturerManufacturerPartNo.LifecycleStatusIndicatorMicrochipSupertex2N7000-GVolumeProductionHowtouse2N7000AMosfethasthreeterminals:Drain,SourceandGate.ThecurrentalwaysentersthroughtheDrainandleavesthroughtheSource.TheGatepinactsasaswitchtoturntheMosfetonoroff.IftheGateisconnectedtoground,theMosfetisswitchedoff,i.e.thereisnoconnectionbetweentheDrainandtheSource(open).IftheGateissuppliedwithitssourcevoltage(VGS)thentheMOSFETwillbeON,i.e.theDrainandSourcepinswillbeconnectedtogether(Closed).Thus,bycontrollingthevoltage(VGS),wecanswitchtheMOSFET,makingtheMOSFETavoltage-controlleddevice.Thegate-sourcevoltage(VGS)isacriticalparameterwhenusingthetransistor.Forthistransistor,theVGSis20V,sowhenwesupplythisvoltage,theMOSFETwillbecompletelyclosed.Anyvaluebetween20VcausestheMOSFETtopartiallyclose,creatingapartialconnection.TheloadswitchedbytheMOSFETcanreach60V(VDS)andcanconsumeupto200mA(ID).GivenbellowisaverysimplecircuitunderneaththatusesthisMOSFETtocontrola24V2Aloadmotor.Thecurrentandvoltagevaluescanalsobeobservedwhentheswitchisclosedandopen.AsweknowthatthevoltageofthegridsourceofthisMosfetis20V,weused20VtoturnontheMOSFET.Whenthegateswitchisopen,theMosfetsgatepinmustbeconnectedtogroundtocuttheload,soweuseda10KresistortoturnofftheMOSFETafterturningiton.TheRGresistorisacurrentlimitingresistorthatlimitstherequiredgridcurrent.IftheloadcontrolledbytheMOSFETisaninductiveloadlikethemotorwehaveusedhere,thenitismandatorytouseaflywheeldiodetosafelydischargetheloadaccumulatedbytheinductivecoil.Wheretouse2N70002N7000isasmallN-channelMOSFET.MOSFETsareelectronicpowerswitches,justliketransistors,butwithahighercurrentandvoltagerating.The2N7000MOSFETcanbeusedtoswitchloadsthatoperateonlessthan60V(VDS)and200mA(ID).ThismosfetcomesinacompactTO-92packageandhasathresholdvoltageof3V,soifyouarelookingforasmallmosfettoswitchaload,thisICmightberightforyou.ProductManufacturerMicrochipTechnologyInc.isaleadingproviderofmicrocontrollerandanalogsemiconductors,providinglow-riskproductdevelopment,lowertotalsystemcostandfastertimetomarketforthousandsofdiversecustomerapplicationsworldwide.HeadquarteredinChandler,Arizona,Microchipoffersoutstandingtechnicalsupportalongwithdependabledeliveryandquality.FAQWhatisa2n7000Mosfet?2N7000isasmallsignalN-channelMOSFET.MOSFETsarepowerelectronicswitchesjustliketransistors,butwithahighercurrentandvoltagerating.The2N7000MOSFETcanbeusedtoswitchloadswhichoperatesonlessthan60V(VDS)and200mA(ID).Whatisamaximumoperatingvoltageforthe2n7002transistor?The2N7002isalogiclevelMOSFETwithalowon-stateresistance.Themosfethasalowgatetosourcethresholdvoltageof2.1Vtypicallythismakesthemosfetsuitableevenfor3.3Vapplicationcircuits.WhatisMosfetgatethresholdvoltage?ThethresholdvoltagerepresentsthevoltageatwhichtheMOSFETstartstoturnon,whilstthemaximumgate-sourcevoltageisthemaximumgate-sourcevoltagethattheMOSFETcanwithstandsafely.WhatisanchannelMosfet?TheN-ChannelMOSFEThasanN-channelregionlocatedinbetweenthesourceanddrainterminals.Itisafour-terminaldevicehavingtheterminalsasgate,drain,source,body.InthistypeofFieldEffectTransistor,thedrainandsourceareheavilydopedn+regionandthesubstrateorbodyareofP-type.DescriptionThe2N7002isalogiclevelMOSFETwithalowon-stateresistance.Themosfethasalowgatetosourcethresholdvoltageof2.1Vtypicallythismakesthemosfetsuitableevenfor3.3Vapplicationcircuits.Sincethemosfethaslowonstateresistanceithashighefficiencyduringwhenthemosfetinon.Duetothispropertyitcanmaintainhighswitchingperformanceandhenceusedwidelyinpowermanagementapplications.ThemosfetalsocomesinaSMDpackagehencecanbeusedforcompactapplications.Oneconsiderabledisadvantageofthemosfetisitslowdraincurrent;itcanprovideacontinuouscurrentof200mAandpeakscurrentsupto1Aatmaximumthresholdvoltage.Anythingmorethanthatwilldamagethemosfet.CatalogDescriptionPinConfigurationFeaturesDucumentsandMediaPackageOutlineApplicationsAlternativesProductManufacturerOrdering&QuantityPinConfigurationPinNo.PinNameDescription1GateControlsthebiasingoftheMOSFET2SourceCurrentflowsoutthroughSource3DrainCurrentflowsinthroughDrainFeaturesSuitableforlogiclevelgatedrivesourcesSurface-mountedpackageVeryfastswitchingTrenchMOSFETtechnologyDocumentsandMediaDatasheet2N7002N-ChannellogiclevelMOSFETDatasheetPackageOutlineApplicationsLowcurrentandLowVoltageswitchingapplicationsDC-DCconverterseMobilityapplicationsApplicationwherelowon-stateresistanceisrequired.PowermanagementapplicationsAlternativesNTR4003,FDC666,FDC5582N7002EquivalentP-Channel:BSS84,FDN358POtherN-ChannelMOSFETs:BS170N,IRF3205,2N7000,IRF1010E,IRF540NProductManufacturerNXPSemiconductorsN.V.(NXP)isaholdingcompany.TheCompanyoperatesasasemiconductorcompany.TheCompanyprovideshighperformancemixedsignalandstandardproductsolutions.TheCompanyssegmentsareHighPerformanceMixedSignal(HPMS),StandardProducts(SP),andCorporateandOther.Itsproductsolutionsareusedinarangeofend-marketapplications,includingautomotive,personalsecurityandidentification,wirelessandwirelineinfrastructure,mobilecommunications,multi-marketindustrial,consumerandcomputing.Itengageswithglobaloriginalequipmentmanufacturers(OEMs)andsellsproductsinallgeographicregions.NXPsHPMSsegmentincludesbusinesslines,suchasAutomotive,SecureIdentificationSolutions(SIS),SecureConnectedDevices(SCD),andSecureInterfacesandInfrastructure(SII).TheCompanysSPsegmentsuppliesarangeofstandardsemiconductorcomponents,suchassmallsignaldiscretesandpowerdiscretes.

OPA4227

DescriptionTheweatherinthepasttwodayshassuddenlycooleddown,andIforgottoinstallaswitchonthebedside,andIdontwanttogetoutofbedtoturnoffthelightbecauseofthecold.Atthistime,itwouldbenicetohaveanintelligentcontrolswitch.ThisblogintroducesasmartswitchcontrollerbasedonATMEGA328P-PU.Thecontroller,withoutchangingtheexistingswitchesandcircuits,canautomaticallyturnoffthelightsafterapowerfailure.Atthesametime,thewirelesscontrollightswitchfunctioncanalsoberealizedthroughtheBluetoothmodule,andthelightcanbeturnedonandoffwhilelyingdown,andthereisnoneedtogetoutofbed.ATMEGA328P-PUCatalogDescriptionIIntroductionIIATmega328P-PUBasedSystemPricipleIIIATmega328P-PUBasedSystemHardwareDesign3.1Centralcontrolmodule3.2Lightdetectioncircuit3.3BluetoothmoduleIVATmega328P-PUBasedStructureDesignVATmega328P-PUBasedSystemSoftwareDesignVIConclusionComponentDatasheetFAQOrdering&QuantityIIntroductionThesmartswitchlightcontrollerbasedonATmega328P-PUintroducedinthisblogconsistsofthefollowingmodules:LightDetectionModule:Perceivethechangeofindoorlightintensity;BluetoothModule:controlandrealizeautomaticlightswitch;SteeringGearandMechanicalLinkageMechanism:Itcanalsoautomaticallyturnoffthelights.Thecontrollerusestheorganiccombinationofmechatronics,whichisreliableandeasytocontrol.IIATmega328P-PUBasedSystemPricipleTheintelligentswitchlightcontrollersystemismainlycomposedoflightdetectionmodule,Bluetoothmodule,steeringgearandArduinocontrolsystem.Thesystemcontrolprocessisasfollows:Thelightdetectionmoduleperceivestheenvironmentfrombrighttodark;ThelightdetectionmodulesendsthesensedinformationtotheArduino;Arduinoturnsoffthelightingequipmentbycontrollingthesteeringgearaccordingtothisinformation;Or,tocompletetheoperationofturningoffthelights,youcanalsodirectlycontrolitthroughthemobilephoneAPPBluetooth.ThesystemprinciplediagramoftheintelligentswitchlightcontrollerisshowninFigure1.Figure1.SystemschematicdiagramIIIATmega328P-PUBasedSystemHardwareDesign3.1CentralcontrolmoduleThemostwidelyusedmicrocontrollersforthecentralcontrolmoduleareAVRand51microcontrollers.Fromtheperspectiveoffunctionandupgradepotential,theAVR8-bitmicrocontrollerATMEGA328P-PUwasselectedasthecentralcontrolmodule.So,whataretheadvantagesofATMEGA328P-PUcontrolmodule?Whychooseit?ATMEGA328P-PU,asacentralcontrolmodule,hasflexibleI/Oportresourcesandpowerfulfunctions.Itnotonlyhaslowpowerconsumptionbutisreliable,andcanmeettheneedsofsubsequentequipmentupdates.Figure2showstheminimumsystemdiagramofATMEGA328P.Figure2.ATMEGA328Pminimumsystem3.2LightdetectioncircuitHere,thelightdetectioncircuitisafour-wiresystem.TheAOportisananalogsignaloutputport,whichconvertstheexternallightintensityintoacontinuousoutputvoltagevalue.Whenthebrightnessofthelightchanges,howdoestheDOportactasadigitalsignaloutputport?Whentheambientlightbrightnessdoesnotreachthesetthreshold,theDOterminaloutputsahighlevel;Whenthebrightnessoftheambientlightexceedsthesetthreshold,theDOterminaloutputsalowlevel.Becausethesignaloutputbythecircuitisstableandreliable,thecontrollerselectsthedigitalsignaloutputbytheDOportastheinputsignalofthecontrolmodule.Inthisway,thesensitivityandreliabilityofthesystemcanbeimproved.IlluminationdetectioncircuitdiagramshowninFigure3.Figure3.Illuminationdetectioncircuitdiagram3.3BluetoothmoduleThisblogusestheHC-05master-slaveintegratedBluetoothmodule.ItscircuitdiagramisshownasinFig.4.Figure4.BluetoothdetectioncircuitThemoduleadoptsCSRmainstreamBluetoothchip,BluetoothV2.0protocolstandard,andcanworkwith3.3Vlowvoltage.Itischeap,smallinsize,stableinsignal,lowinpower,andcanbeusedinconjunctionwithmobileAPPtorealizewirelesscontrolofthesystem.Inthisdesign,Bluetoothonlyactsasaslave,receivinginstructionsfromthemobilephone.IVATmega328P-PUBasedStructureDesignTakethedormitoryasanexampletodesignthecontrollerfortheswitch(asshowninFigure5).Figure5.PowerswitchAftermeasurement,whentheswitchisintheequilibriumposition,thatis,betweentheclosedandopenpositions,ifthelight-offpositionispressedmorethan2mm,thebuttonwillturnoffthepower.Whenthelight-onpositionispresseddownmorethan2mm,thebuttonwillturnonthepower.Wecandesignalinkmechanismconnectedwiththesteeringgeartomake:Whenthesteeringgearrotatesto180,theconnectingrodpositionisthehighest;Whenthesteeringgearrotatesto0,theconnectingrodpositionislowest.Then,settheinitialpositionofthesteeringgearto90,sothatthebuttonisatthevalueofthebalanceposition.Atthistime,coincidethemiddlepositionoftheT-shapedfixingbracketwiththemiddlepositionofthebutton.Inaddition,inordertofacilitatetherealizationoffunctions,thecentralpositioncanbesetasachute.Figure6showsthedesignandinstallation.Figure7showsthatthecontrollerisdesignedasarectangularbox.Figure8showsthelayoutofeachmodule.Figure9showsthephysicalobjectandinstallationdiagramofthesmartswitchcontroller.Figure6.DesignandinstallationdrawingofconnectingrodpartFigure7.OverallviewofthecontrollerFigure8.SchematicdiagramofeachmoduleinstallationFigure9.PhysicalimageofsmartswitchcontrollerVATmega328P-PUBasedSystemSoftwareDesignThesoftwarepartcompletestheprocessingofthesignalsreceivedbythelightdetectionmoduleandtheBluetoothmodule,andthencontrolsthemechanicalstructuretoswitchthelights.Figure10showsthesystemsoftwareflowchart.Thelightdetectionmodule(theschematicdiagramofthelightdetectionmoduleisshowninFigure11)isusedtodetectchangesinbrightnessanddarknessofthesurroundingenvironment.Whenthesurroundingenvironmentisalwaysinalightstate,thelightdetectioncircuitwillcontinuouslysendalow-levelsignal0tothecentralcontrolmodule;Whenthesurroundingenvironmenthasbeeninadarkstate,thelightdetectioncircuitwillcontinuouslysendahighlevelsignal1tothecentralcontrolmodule.Whenthesurroundingenvironmentchangesfromnolighttolight(judgingthedaybreak),inthiscase,thesystemdoesnotact.Whenthesurroundingenvironmentchangesfromlighttonolight(judgedasamomentofpowerfailure),thelightdetectioncircuitwillstarttosendahighlevelsignal1tothecentralcontrolmodule.Atthemomentoftransition,thecentralcontrolmodulewillcontrolthesystemtoexecuteaworkcycle.Afterturningoffthelight,thesystemwillautomaticallyresetandwaitforthenextchangefromlighttonolight.Becausetheportmemoryofthecentralcontrolmoduleislimited,andthelightdetectioncircuitcontinuouslytransmitsdatatotheport.Thiswillcausethecentralcontrolmoduletorestartinashorttimeduetoexhaustionofmemory,makingthesystemunstableandunreliable.Therefore,aportclearingfunctionisspeciallywrittenwhencompilingthesystemtoensurethattheexpireddatasentbythelightdetectioncircuitisclearedintime.Therebyimprovingthestabilityandreliabilityofthesystem.Figure10.SystemsoftwareflowchartAftertalkingaboutthelightdetectionmodule,howdoestheBluetoothmoduleprocessthereceivedsignaltocontroltheswitch?WecanusemobilephoneAPPandBluetoothmoduletocontrolthesystemtoturnonandoffthelightsthroughwirelesstransmission.WhenthemobilephonesendsthecommandcharacterAtothecentralcontrolmodulethroughtheBluetoothmodule,thesystemwillexecuteacycleofturningoffthelights,andthenautomaticallyreset;Inthesameway,whenthemobilephonesendsthecommandcharacterBtothecentralcontrolmodulethroughtheBluetoothmodule,thesystemexecutesalight-oncommandforaworkingcycle,andthenautomaticallyresets.Figure11.SchematicdiagramofthelightmoduleVIConclusionThesmartswitchlightcontrollerdiscussedinthisbloghassignificantadvantages:*Donotchangethecircuitoftheoriginalpush-typepowerswitch.Therefore,itisnotonlysafe,butalsoeasytodisassembleandassemble;*TurnonandoffthelightsviaBluetoothwirelesscontrol.Therefore,ithasstrongoperability;*Aftercompletingtheswitchlampworkcycle,realizeautomaticreset.Inaddition,whilerealizingautomation,wecanalsomoveourfingerstoeasilyswitchlightsonthebed;*ATmega328P-PUhasgreatdevelopmentpotential.Thereasonforusingitistomeettheneedsofexpandingfunctionsinthefuture.suchas:CooperatewithWIFImodule:canrealizeultra-remotecontrol;Cooperatewithtimer:itcanrealizethefunctionofturningonthelightsatatime.Insummary,theintelligentswitchlightcontrollerbasedonATmega328P-PUweintroducedissimpleandreasonableinstructure,easytoinstall,safe,convenientandefficienttooperate.WiththesmartswitchlightcontrollerofATmega328P-PU,whenwelazilylieonthebedandplaywiththemobilephone,weusethemobilephonetocontrolthelightswitch.Atnight,weareafraidthatweforgettoturnoffthelightswhenwefallasleep,andwedontneedtogetoutofbed.Itcanalsoautomaticallyturnoffthelightswhenitgetsdark.ComponentDatasheetATMEGA328PDatasheetFAQWhatismeantbyATMEGA328P?ATMEGA328Pishighperformance,lowpowercontrollerfromMicrochip.ATMEGA328Pisan8-bitmicrocontrollerbasedonAVRRISCarchitecture.ItisthemostpopularofallAVRcontrollersasitisusedinARDUINOboards.WhatisthedifferencebetweenATMEGA328andATMEGA328P?ATMEGA328PandATMEGA328arethesameeverysensearchitecturally.ATMEGA328PjustconsumeslowerpowerthanATMEGA328,whichmeansthatthe328Pismanufacturedinafinerprocessthanthe328.WhyATMEGA328isusedinArduino?TheATMEGA328/Pisalow-powerCMOS8-bitmicrocontrollerbasedontheAVRenhancedRISC(reducedinstructionsetcomputer)architecture.InOrdertomaximizeperformanceandparallelism,theAVRusesHarvardarchitecturewithseparatememoriesandbusesforprogramanddata.HowdoyoucodeATMEGA328P?IsATMEGA328Pamicrocontroller?TheATMEGA328isasingle-chipmicrocontrollercreatedbyAtmelinthemegaAVRfamily(laterMicrochipTechnologyacquiredAtmelin2016).IthasamodifiedHarvardarchitecture8-bitRISCprocessorcore.CantheATMEGA328PmicrocontrollerbeusedwithouttheArduinoboard?Yes.YoucanuseATMega328Pwithoutarduinoboard....YoucanusearduinoboardwiththeIC.ProgramtheICandthentakeitoutanduseitinyourcircuit.Youwillhavetouse16MHZOscillatorwithcapacitors.HowdoIprogramAtmega328Pwithoutbootloader?ProgrammingAVRWithArduinoAsISPWithoutBootloaderandExternalCrystalStep1:ThingsYouNeed....Step2:UploadArduinoISPCodeonArduinoBoard....Step3:OpenCommandPrompt(inWindowsOS)...Step4:RequiredDownloads.....Step5:InstallationofWinAVR(onlyHelpforWindowsOSIsCoveredforNow)DescriptionTheCD405xBanalogmultiplexersanddemultiplexersaredigitally-controlledanalogswitcheshavinglowONimpedanceandverylowOFFleakagecurrent.ThesemultiplexercircuitsdissipateextremelylowquiescentpoweroverthefullVDDVSSandVDDVEEsupplyvoltageranges,independentofthelogicstateofthecontrolsignals.TheCD4051Bisasingle8-Channelmultiplexerhavingthreebinarycontrolinputs,A,B,andC,andaninhibitinput.Thethreebinarysignalsselect1of8channelstobeturnedon,andconnectoneofthe8inputstotheoutput.CatalogDescriptionPinoutConfigurationandFunctionCD4051BlockDiagramDocumentsandMediaFeaturesApplicationCD4051TypicalApplicationCircuitsOrdering&QuantityPinoutConfigurationandFunctionCD4051BlockDiagramThelogicdiagramofCD4051iscomposedofthreeparts:logiclevelconversioncircuit,8select1decodingcircuitand8CMOSswitchunits.A,BandCare3-bitbinaryaddressinputterminals,and8combinationsof3-bitbinarycanbeusedforselection8channels;INHistheaddressinputprohibitionterminal,whenitishigh,theaddressinputterminalisinvalid,thatis,nochannelisstrobed.TheinputlevelsofA,B,CandINHarecompatiblewithTTL.CD4051has8input\outputterminals,1output/inputterminal,digitalcircuitpowersupply+Eand-E1,analogcircuitpowersupply+Eand-E2.ThemainfunctionofthelogiclevelconversioncircuitistoinputtheaddressA,B,CandaddressinputinhibitterminalINHinputTTLlogiclevelisconvertedintoCMOSlevel,sothattheswitchunitcanbecontrolledbyTTLlevel.Themainfunctionofthe8-to-1addressdecodingcircuitistoconverttheaddressinputsignalfromthelogiclevelconversioncircuitintothecorrespondingswitchunitstrobesignalandturnonthecorrespondingswitchunit.DocumentsandMediaDatasheetCD405xBCMOSSingle8-ChannelAnalogMultiplexer/DemultiplexerwithLogic-LevelConversiondatasheet(Rev.I)FeaturesWideRangeofDigitalandAnalogSignalLevelsDigital:3Vto20VAnalog:20VP-PLowONResistance,125Ω(Typical)Over15VP-PSignalInputRangeforVDDVEE=18VHighOFFResistance,ChannelLeakageof100pA(Typical)atVDDVEE=18VLogic-LevelConversionforDigitalAddressingSignalsof3Vto20V(VDDVSS=3Vto20V)toSwitchAnalogSignalsto20VP-P(VDDVEE=20V)MatchedSwitchCharacteristics,rON=5Ω(Typical)forVDDVEE=15VVeryLowQuiescentPowerDissipationUnderAllDigital-ControlInputandSupplyConditions,0.2W(Typical)atVDDVSS=VDDVEE=10VBinaryAddressDecodingonChip5V,10V,and15VParametricRatings100%TestedforQuiescentCurrentat20VMaximumInputCurrentof1Aat18VOverFullPackageTemperatureRange,100nAat18Vand25CBreak-Before-MakeSwitchingEliminatesChannelOverlapApplicationAnalogandDigitalMultiplexingandDemultiplexingA/DandD/AConversionSignalGatingFactoryAutomationTelevisionsAppliancesConsumerAudioProgrammableLogicCircuitsSensorsCD4051TypicalApplicationCircuits1.CD4051,CH3130multi-channeldemodulatorcircuitdiagramThiscircuitismainlycomposedof8-channelanalogswitchCD4051andvoltagefollowerCH3130,etc.TheinputsignaloftheprohibitionterminalINHofanalogswitchCD4051isusedtocontrolthegatingofvoltagefollowerCH3130,therebyperformdemodulationtomultipleanalogsignals.2.CD4051constructs32-channelcircuitBecausetheCD4051hasonlyeightinputports,fourCD4051sareneededtobuilda32-waymultiplexer,labeledINH1,INH2,INH3,andINH4.The32-waymultiplexershouldhave5controlports,ofwhichthefirstthreearetheinputportsofCD4051andthelasttwoarecontrolports.(BecauseCD4051hasthreeinputports),labelthemasD1,D2,D3,D4,D5(0000011111,00000channel0,11111channel31).Thebasicideaistorealizethechoiceof32channelports(0-7,8-15,16-23,24-31)byselecting4CD4051s.IfyouchoosethethirdCD4051,youcanchoose16-23(10000-10111)channelport.However,theselectionofCD4051isachievedbycontrollingtheINHlevelofeachCD4051.Forexample,ifyouwanttoturnonthethirdCD4051,makeitsINHhigh(atthistimeD5=1,D4=0,thenINH3=D5!D4).Therefore,thechoiceofINHisachievedbycontrollingthelogicalrelationshipbetweenD5andD4.WhereINH1=!D5!D4;INH2=!D5D4;INH3=D5!D4;INH4=D5D4.

OPA4227

DescriptionLM317isaadjustable3-terminalpositive-voltageregulator,thisbolgcoversLM317regulatoralternative,datasheet,applications,featuresandotherinformationonhowtouseandwheretousethisdevice.ABasicIntroductiontoLM317VoltageRegulatorCatalogDescriptionLM317PinoutLM317FeaturesLM317ApplicationsLM317CircuitLM317ParametersLM317CADModelLM317AdvantageLM317ElectricalCharacteristicsLM317PackageLM317AlternativesLM317EquivalentsWheretouseLM317HowtouseLM317LM317ManufacturerComponentDatasheetFAQOrdering&QuantityLM317PinoutPinNumberPinNameDescription1AdjustThispinsadjuststheoutputvoltage2OutputVoltage(Vout)Theregulatedoutputvoltagesetbytheadjustpincanbeobtainedfromthispin3InputVoltage(Vin)TheinputvoltagewhichhastoberegulatedisgiventothispinLM317FeaturesOutputvoltagerangeadjustablefrom1.25Vto37VOutputcurrentgreaterthan1.5AInternalshort-circuitcurrentlimitingThermaloverloadprotectionOutputsafe-areacompensationLM317ApplicationsATCAsolutionsDLP:3Dbiometrics,hyperspectralimaging,opticalnetworking,andspectroscopyDVRandDVSDesktopPCsDigitalsignageandstillcamerasECGelectrocardiogramsEVHEVchargers:levels1,2,and3ElectronicshelflabelsEnergyharvestingEthernetswitchesFemtobasestationsFingerprintandirisbiometricsHVAC:heating,ventilating,andairconditioningHigh-speeddataacquisitionandgenerationHydraulicvalvesIPphones:wiredandwirelessIntelligentoccupancysensingMotorcontrols:brushedDC,brushlessDC,lowvoltage,permanentmagnet,andsteppermotorsPoint-to-pointmicrowavebackhaulsPowerbanksolutionsPowerlinecommunicationmodemsPoweroverethernet(PoE)PowerqualitymetersPowersubstationcontrolsPrivatebranchexchanges(PBX)ProgrammablelogiccontrollersRFIDreadersRefrigeratorsSignalorwaveformgeneratorsSoftware-definedradios(SDR)Washingmachines:high-endandlow-endX-rays:baggagescanners,medical,anddentalLM317CircuitLM317ParametersOutputoptionsAdjustableOutputIout(Max)(A)1.5Vin(Max)(V)40Vin(Min)(V)3Vout(Max)(V)37Vout(Min)(V)1.25Noise(uVrms)38Iq(Typ)(mA)5ThermalresistanceJA(C/W)24Approx.price(US$)1ku|0.14Loadcapacitance(Min)(F)0RatingCatalogRegulatedoutputs(#)1FeaturesAccuracy(%)5PSRR@100KHz(dB)38Dropoutvoltage(Vdo)(Typ)(mV)2000Operatingtemperaturerange(C)0to125IhsManufacturerTEXASINSTRUMENTSINCBrandNameTexasInstrumentsLM317CADModelPackagePinsDownloadDDPAK/TO-263(KTT)3ViewoptionsSOT-223(DCY)4ViewoptionsTO-220(KCS)3ViewoptionsTO-220(KCT)3ViewoptionsLM317ElectricalCharacteristicsOverrecommendedrangesofoperatingvitualjunctiontemperature(unlessotherwisenoted)LM317PackageDDPAK/TO-263(KTT)SOT-223(DCY)TO-220(KCS)TO-220(KCT)LM317AlternativesSharethesamefunctionalityandpinoutbutisnotanequivalenttothecompareddevice:LM7805,LM7806,LM7809,LM7812,LM7905,LM7912,LM117V33,XC6206P332MR.LM317EquivalentsLT1086,LM1117(SMD),PB137,LM337(NegativeVariableVoltageregulator)WheretouseLM317WhenitcomestovariablevoltageregulationrequirementsLM317wouldmostlikelybethefirstchoice.Apartfromusingitasavariablevoltageregulator,itcanalsobeusedasafixedvoltageregulator,currentlimiter,Batterycharger,ACvoltageregulatorandevenasanadjustablecurrentregulator.OnenotabledrawbackofthisICisthatithasavoltagedropofabout2.5acrossitduringregulation,soifyoulookingtoavoidthatproblemlookintotheotherequivalentICsgivenabove.So,ifyouarelookingforavariablevoltageregulatortodelivercurrentupto1.5AthenthisregulatorICmightbetherightchoiceforyourapplication.HowtouseLM317LM317isa3-terminalregulatorICanditisverysimpletouse.Ithasmanyapplicationcircuitsinitsdatasheet,butthisICisknownforbeingusedasavariablevoltageregulator.So,letslookintohowtousethisICasavariablevoltageregulator.AssaidearliertheIChas3pins,inwhichtheinputvoltageissuppliedtopin3(VIN)thenusingapairofresistors(potentialdivider)wesetavoltageatpin1(Adjust)whichwilldecidetheoutputvoltageoftheICthatisgivenoutatpin2(VOUT).Nowtomakeitactasavariablevoltageregulatorwehavetosetvariablevoltagesatpin1whichcanbedonebyusingapotentiometerinthepotentialdivider.Thebelowcircuitisdesignedtotake12V(youcansupplyupto24V)asinputandregulateitfrom1.25Vto10V.TheResistorR1(1K)andthepotentiometer(10k)togethercreatesapotentialdifferenceatadjustpinwhichregulatestheoutputpinaccordingly.TheformulaetocalculatetheOutputvoltagebasedonthevalueofresistorsisVOUT=1.25(1+(R2/R1))Now,letsverifythisformulafortheabovecircuit.ThevalueofR1is1000ohmsandthevalueofR2(potentiometer)is5000becauseitisa10kpotentiometerplacedat50%(50/100of1000is5000).Vout=1.25(1+(5000/1000))=1.256=7.5VAndthesimulationshows7.7Vwhichisprettymuchclose.Youcanvarytheoutputvoltagebysimplyvaryingthepotentiometer.Inourcircuit,amotorisconnectedasaloadwhichconsumesaround650mAyoucanconnectanyloadupto1.5A.Thesameformulaecanalsobeusedtocalculatethevalueofresistorforyourequiredoutputvoltage.Oneeasywaytodothisistousethisonlinecalculatortorandomlysubstitutethevalueofresistorsyouhaveandcheckwhichoutputvoltageyouwillget.LM317ManufacturerTexasInstrumentsInc.(TI)isanAmericantechnologycompanythatdesignsandmanufacturessemiconductorsandvariousintegratedcircuits,whichitsellstoelectronicsdesignersandmanufacturersglobally.ItsheadquartersareinDallas,Texas,UnitedStates.TIisoneofthetoptensemiconductorcompaniesworldwide,basedonsalesvolume.TexasInstrumentssfocusisondevelopinganalogchipsandembeddedprocessors,whichaccountsformorethan80%oftheirrevenue.TIalsoproducesTIdigitallightprocessing(DLP)technologyandeducationtechnologyproductsincludingcalculators,microcontrollersandmulti-coreprocessors.Todate,TIhasmorethan43,000patentsworldwide.ComponentDatasheetLM317DatasheetFAQWhatislm317usedfor?TheLM317servesawidevarietyofapplicationsincludinglocal,oncardregulation.Thisdevicecanalsobeusedtomakeaprogrammableoutputregulator,orbyconnectingafixedresistorbetweentheadjustmentandoutput,theLM317canbeusedasaprecisioncurrentregulator.Whatisthemaximuminputvoltageoflm317?TheLM317isanadjustablevoltagelinearregulatorthatcanoutput1.2537Vatupto1.5Acurrentwithaninputvoltagerangeof340V.Whatisthedifferencebetweenlm317andlm317t?Member.Thereisnofunctionaldifferenceastheyareoneinthesame.TheTattheendjustindicatesthatitsinaTO-220package.Theyusuallytagonextrathingsafterthepartnametoreferencethingslikepackage,temprange,etc.Islm317atransistor?TheLM317isanadjustablethree-terminalpositive-voltageregulatorcapableofsupplyingmorethan1.5Aoveranoutput-voltagerangeof1.25Vto32V....Byusingaheat-sinkedpasstransistorsuchasa2N3055(Q1)wecanproduceseveralampsofcurrentfarabovethe1.5ampsoftheLM317.Howdoesanlm317work?Thecircuitconsistsofalow-sideresistorandhigh-sideresistorconnectedinseriesformingaresistivevoltagedividerwhichisapassivelinearcircuitusedtoproduceanoutputvoltagewhichisafractionofitsinputvoltage.WhatisIClm317?TheLM317deviceisanadjustablethree-terminalpositive-voltageregulatorcapableofsupplyingmorethan1.5Aoveranoutput-voltagerangeof1.25Vto37V.Itrequiresonlytwoexternalresistorstosettheoutputvoltage.Thedevicefeaturesatypicallineregulationof0.01%andtypicalloadregulationof0.1%.HowdoIknowifmylm317isworking?Testinglm317t.Ifyoulooktotheic,thelegstowardsyou,therightoneistheinputpin.youmustseeadifferenceofminimum1.2Vbetweenthetwopins,otherwisetheICisfaulty.furthermore,thefirsttestistoseeifyouhaveinputvoltage!Whatistheworkingpricipleoflm317?LM317worksonaverysimpleprinciple.Itisavariablevoltageregulatori.e.supportsdifferentoutputvoltagelevelsforaconstantappliedinputvoltagesupply.HowtomakeasimplevoltageregulatorcircuitusingLM317?

DescriptionLM339(Quaddifferentialcomparator)consistoffourindependentvoltagecomparators.Itisacommonintegratedcircuitandismainlyusedinhigh-voltagedigitallogicgatecircuits.UsingLM339caneasilyformvariousvoltagecomparatorcircuitsandoscillatorcircuits.CatalogDescriptionComponentDatasheetLM339PinoutBasicParametersFeaturesApplicationPinFunctionListCircuitDiagramPackageElectricalCharacteristicsInstructionsProductManufacturerFAQOrdering&QuantityComponentDatasheetComparatorDatasheetLM339DatasheetLM339PinoutLM339PinoutBasicParametersParameternameSymbolNumericalvalueunitsupplyvoltageVCC18or36VDifferentialmodeinputvoltageVID36VCommonmodeinputvoltageVI-0.3~VCCVPowerdissipationPd570mWWorkingenvironmenttemperatureTopr0to+70℃StoragetemperatureTstg-65to150℃FeaturesLowvoltageoffset,generally2mVThecommon-modevoltagerangeisverylarge,from0vtothepowersupplyvoltageminus1.5vTheinternalresistancelimittothesignalsourceisverywideSingleSupplyOperation:2-36VDualSupplyOperation:1V-18VThepotentialofoutputcanbeselectedflexiblyandconvenientlyLM339issimilartooperationalamplifierwithnon-adjustablegain.Eachcomparatorhastwoinputsandoneoutput.Oneofthetwoinputterminalsiscalledthenon-invertinginputterminal,whichisrepresentedby+,andtheotheriscalledtheinvertinginputterminal,whichisrepresentedby-.Whencomparingtwovoltages,addafixedvoltageasareferencevoltageatanyinputterminal,andaddasignalvoltagetobecomparedattheotherterminal.Whenthevoltageatthe+terminalishigherthanthe-terminal,theoutputtubewillcutoff.Whenthevoltageofthe-terminalishigherthanthe+terminal,theoutputtubeissaturated.Thevoltagedifferencebetweenthetwoinputterminalsisgreaterthan10mV,whichcanensurethattheoutputcanbereliablyswitchedfromonestatetoanotherstate.Therefore,itisidealtousetheLM339inweaksignaloccasions.TheoutputterminalofLM339isequivalenttoacrystaltransistorthatisnotconnectedtothecollectorresistor.Whenusing,theoutputterminaltothepositivepowersupplygenerallyneedstobeconnectedtoaresistor(calledpull-upresistor).Choosingpull-upresistorswithdifferentresistancevalueswillaffectthevalueofthehighpotentialattheoutput.Becausewhentheoutputtransistorisoff,itscollectorvoltagebasicallydependsonthevalueofthepull-upresistorandtheload.Inaddition,theoutputofeachcomparatorisallowedtobeconnectedtogether.ApplicationIndustrialAutomotiveInfotainmentandClustersBodyControlModulePowerSupervisionOscillatorsPeakDetectorsLogicVoltageTranslationPinFunctionListPinNumberPinfunctionSymbolPinNumberPinfunctionSymbol1Output2OUT28Invertinginput31N-(3)2Output1OUT19Forwardinput31N+(3)3PowerSupplyVCC+10Invertinginput41N-(4)4Invertinginput11N-(1)11Forwardinput41N+(4)5Positiveinput11N+(1)12PowerSupplyVcc6Invertinginput21N-(2)13Output4OUT47Forwardinput2OUT2(2)14Output3OUT3CircuitDiagramLM339CircuitDiagramPackageLM339PackageElectricalCharacteristicsVCC=5.0V,Tamb=25℃,unlessotherwisestatedParameternameSymbolTestconditionsMinimumTypicalMaximumunitInputoffsetvoltageVIOVCM=0toVCC-1.5VO(P)=1.4V,Rs=0-1.05.0mVInputoffsetcurrentIIO--550nAInputbiascurrentIb--65250nACommonmodeinputvoltageVIC-0-VCC-1.5VQuiescentCurrentICCVCC=+5V,noload-1.12.0mAVCC=+30V,noload-1.32.5mAVoltagegainAVVCC=15V,RL>15k-200-V/mVSinkcurrentIsinkVi(-)>1V,Vi(+)=0V,Vo(p)<1.5V616-mAOutputleakagecurrentIOLEVi(-)=0V,Vi(+)=1V,VO=5V-0.1-nAInstructionsTheLM339seriesarehighgain,widebandwidthdeviceswhich,likemostcomparators,caneasilyoscillateiftheoutputleadisinadvertentlyallowedtocapacitivelycoupletotheinputsviastraycapacitance.Thisshowsuponlyduringtheoutputvoltagetransitionintervalsasthecomparatorchangesstates.Powersupplybypassingisnotrequiredtosolvethisproblem.StandardPCboardlayoutishelpfulasitreducesstrayinput-outputcoupling.Reducingthisinputresistorsto10kreducesthefeedbacksignallevelsandfinally,addingevenasmallamount(1to10mv)ofpositivefeedback(hysteresis)causessucharapidtransitionthatoscillationsduetostrayfeedbackarenotpossible.SimplysocketingtheICandattachingresistorstothepinswillcauseinput-outputoscillationsduringthesmalltransitionintervalsunlesshysteresisisused.Iftheinputsignalisapulsewaveform,withrelativelyfastriseandfalltimes,hysteresisisnotrequired.Allpinsofanyunusedcomparatorsshouldbetiedtothenegativesupply.ThebiasnetworkofLM339establishesadraincurrentwhichisindependentofthemagnitudeofthepowersupplyvoltageovertherangeoffrom2Vto30V.Itisusuallyunnecessarytouseabypasscapacitoracrossthepowersupplyline.ThedifferentialinputvoltagemaybelargerthanV+withoutdamagingthedevice.Protectionshouldbeprovidedtopreventtheinputvoltagesfromgoingnegativemorethan-0.3VDC(at25℃).Aninputclampdiodecanbeusedasshownintheapplicationssection.TheoutputoftheLM339istheuncommittedcollectorofagrounded-emitterNPNoutputtransistor.ManycollectorscanbetiedtogethertoprovideanoutputORingfunction.Anoutputpull-upresistorcanbeconnectedtoanyavailablepowersupplyvoltagewithinthepermittedsupplyvoltagerangeandthereisnorestrictiononthisvoltageduetothemagnitudeofthevoltagewhichisappliedtotheV+terminaloftheLM1339package.TheoutputcanalsobeusedasasimpleSPSTswitchtoground(whenapull-upresistorisnotused).Theamountofcurrentwhichtheoutputdevicecansinkislimitedbythedriveavailable(whichisindependentofV+)andtheofthisdevice.Whenthemaximumcurrentlimitisreached(approximately16mA),theoutputtransistorwillcomeoutofsaturationandtheoutputvoltagewillriseveryrapidly.Theoutputsaturationvoltageislimitedbytheapproximately60RSAToftheoutputtransistor.Thelowoffsetvoltageoftheoutputtransistor(1mV)allowstheoutputtoclampessentiallytogroundlevelforsmallloadcurrents.ProductManufacturerTexasInstrumentsInc.(TI)isanAmericantechnologycompanythatdesignsandmanufacturessemiconductorsandvariousintegratedcircuits,whichitsellstoelectronicsdesignersandmanufacturersglobally.ItsheadquartersareinDallas,Texas,UnitedStates.TIisoneofthetoptensemiconductorcompaniesworldwide,basedonsalesvolume.TexasInstrumentssfocusisondevelopinganalogchipsandembeddedprocessors,whichaccountsformorethan80%oftheirrevenue.TIalsoproducesTIdigitallightprocessing(DLP)technologyandeducationtechnologyproductsincludingcalculators,microcontrollersandmulti-coreprocessors.Todate,TIhasmorethan43,000patentsworldwide.FAQWhatisLM339?LM339isavoltagecomparatorICfromLMx39xseriesandismanufacturedbymanyindustries.Thedevicesconsistoffourindependentvoltagecomparatorsthataredesignedtooperatefromasinglepowersupply.WhatisthedifferencebetweenLM324andLM339?TheLM324hasacomplementaryoutputwhiletheLM339isopencollector.Inthecomplementaryoutput,currentcanflowineitherdirectionasrequired(eithersourceorsink)whiletheopencollectoroutputcanonlysinkcurrent.HowdoesLM339comparatorwork?TheLM339isaquadopampcomparator.Acomparatorworksbyasimpleconcept.Eachopampofacomparatorhas2inputs,ainvertinginputandanoninvertinginput.Iftheinvertinginputvoltageisgreaterthanthenoninvertinginput,thentheoutputisdrawntoground.Whatiscomparatoric?Acomparatorisanelectroniccircuit,whichcomparesthetwoinputsthatareappliedtoitandproducesanoutput.Theoutputvalueofthecomparatorindicateswhichoftheinputsisgreaterorlesser.Pleasenotethatcomparatorfallsundernon-linearapplicationsofICs.WhatisthereplacementforLM339?LM311,LM324,LM397,LM139,LM239,LM2901Whatisacomparatorcircuit?Acomparatorcircuitcomparestwovoltagesandoutputseithera1(thevoltageattheplusside;VDDintheillustration)ora0(thevoltageatthenegativeside)toindicatewhichislarger.Comparatorsareoftenused,forexample,tocheckwhetheraninputhasreachedsomepredeterminedvalue.WhatistheuseofLM339?LM339isusedinapplicationswhereacomparisonbetweentwovoltagesignalsisrequired.Inadditionwithfourofthosecomparatorsonboardthedevicecancomparefourpairsofvoltagesignalsatatimewhichcomesinhandyinsomeapplications.DescriptionUC3842isacurrentcontrolpulsewidthmodulationchipwithexcellentperformance.UC3842modulatorsingle-endedoutputcandirectlydriveabipolarpowertubeorfield-effecttube.CatalogUC3842BDocumentsandMediaUC3842BAdvantagesUC3842BFeaturesUC3842BSimplifiedBlockDiagramUC3842BPinoutUC3842BPackageInformationUC3842BBlockDiagramUC3953BTimingDiagramUC3953BPackagesUC3842BCircuitProductManufacturerOrdering&QuantityUC3842BDocumentsandMediaPCNAssembly/OriginPDIP-8AssemblyRevised03/Sep/2013DatasheetsUC384(2,3)B,UC284(2,3)BHTMLDatasheetUC384(2,3)B,UC284(2,3)BEnvironmentalInformationMaterialDeclarationUC3842BNGEDA/CADModelsDownloadfromUltraLibrarianOnlineCatalogMulti-TopologyUC3842BAdvantagesTheUC3842B,UC3843Bseriesarehighperformancefixedfrequencycurrentmodecontrollers.TheyarespecificallydesignedforOffLineandDCDCconverterapplicationsofferingthedesigneracosteffectivesolutionwithminimalexternalcomponents.Theseintegratedcircuitsfeatureatrimmedoscillatorforprecisedutycyclecontrol,atemperaturecompensatedreference,highgainerroramplifier,currentsensingcomparator,andahighcurrenttotempoleoutputideallysuitedfordrivingapowerMOSFET.Alsoincludedareprotectivefeaturesconsistingofinputandreferenceundervoltagelockoutseachwithhysteresis,cyclebycyclecurrentlimiting,programmableoutputdeadtime,andalatchforsinglepulsemetering.Thesedevicesareavailableinan8pindualinlineandsurfacemount(SOIC8)plasticpackageaswellasthe14pinplasticsurfacemount(SOIC14).TheSOIC14packagehasseparatepowerandgroundpinsforthetotempoleoutputstage.TheUCX842BhasUVLOthresholdsof16V(on)and10V(off),ideallysuitedforofflineconverters.TheUCX843BistailoredforlowervoltageapplicationshavingUVLOthresholdsof8.5V(on)and7.6V(off).UC3842BFeaturesTrimmedOscillatorforPreciseFrequencyControlOscillatorFrequencyGuaranteedat250kHzCurrentModeOperationto500kHzAutomaticFeedForwardCompensationLatchingPWMforCycleByCycleCurrentLimitingInternallyTrimmedReferencewithUndervoltageLockoutHighCurrentTotemPoleOutputUndervoltageLockoutwithHysteresisLowStartupandOperatingCurrentThisisaPbFreeandHalideFreeDeviceUC3842BSimplifiedBlockDiagramUC3842BPinout8Pin14PinFunctionDescription11CompensationThispinistheErrorAmplifieroutputandismadeavailableforloopcompensation.23VoltageFeedbackThisistheinvertinginputoftheErrorAmplifier.Itisnormallyconnectedtotheswitchingpowersupplyoutputthrougharesistordivider.35CurrentSenseAvoltageproportionaltoinductorcurrentisconnectedtothisinput.ThePWMusesthisinformationtoterminatetheoutputswitchconduction.47RT/CTTheOscillatorfrequencyandmaximumOutputdutycycleareprogrammedbyconnectingresistorRTtoVrefandcapacitorCTtoground.Operationto500kHzispossible.5GNDThispinisthecombinedcontrolcircuitryandpowerground.610OutputThisoutputdirectlydrivesthegateofapowerMOSFET.Peakcurrentsupto1.0Aaresourcedandsunkbythispin.712VCCThispinisthepositivesupplyofthecontrolIC.814VrefThisisthereferenceoutput.ItprovideschargingcurrentforcapacitorCTthroughresistorRT8PowerGroundThispinisaseparatepowergroundreturnthatisconnectedbacktothepowersource.Itisusedtoreducetheeffectsofswitchingtransientnoiseonthecontrolcircuitry.11VCTheOutputhighstate(VOH)issetbythevoltageappliedtothispin.Withaseparatepowersourceconnection,itcanreducetheeffectsofswitchingtransientnoiseonthecontrolcircuitry.9GNDThispinisthecontrolcircuitrygroundreturnandisconnectedbacktothepowersourceground.2,4,6,13NCNoconnection.Thesepinsarenotinternallyconnected.UC3842BPackageInformationDocumentTitleDocumentID/SizeRevisionRevisionDate8LEADPDIP626-05(51kB)POct,2019SOIC-14NB751A-03(49kB)LOct,2019SOIC-8NarrowBody751-07(53kB)AKOct,2019UC3842BBlockDiagramUC3953BTimingDiagramUC3953BPackagesUC3842BCircuitOscillatorConfigurationExternalClockSynchronizationExternalDutyCycleClampandMulti-UnitSynchronizationAdjustableReductionofClampLevelSoft-StartCircuitAdjustableBufferedReductionofClampLevelwithSoft-StartCurrentSensingPowerMOSFETCurrentWaveformSpikeSuppressionMOSFETParasiticOscillationsBipolarTransistorDriveIsolatedMOSFETDriveLatchedShutdownErrorAmplifierCompensationSlopCompensation27WOff-LineFlybackRegulatorProductManufacturerONSemiconductor(Nasdaq:ON)isdrivingenergyefficientinnovations,empoweringcustomerstoreduceglobalenergyuse.Thecompanyoffersacomprehensiveportfolioofenergyefficientpowerandsignalmanagement,logic,discreteandcustomsolutionstohelpdesignengineerssolvetheiruniquedesignchallengesinautomotive,communications,computing,consumer,industrial,LEDlighting,medical,military/aerospaceandpowersupplyapplications.ONSemiconductoroperatesaresponsive,reliable,world-classsupplychainandqualityprogram,andanetworkofmanufacturingfacilities,salesofficesanddesigncentersinkeymarketsthroughoutNorthAmerica,Europe,andtheAsiaPacificregions.

IDescriptionThisblogintroducesasimplemethodtodrivesteppermotorsusingL297andL298chips.Thesteppingmotordrivesystemdesignedbythismethodhasthefollowingcharacteristics:simplehardwarestructure,easysoftwareprogrammingandlowprice.IDescriptionIIIntroductionIIIL297andL298Hardwarecircuit3.1L297Overview3.2L298Overview3.3L297andL298CircuitIVSoftwaredesignFAQOrdering&QuantityIIIntroductionSteppermotorisoneofthecommonlyusedembeddedmotioncontrolequipmentinindustrialcontrol.Thisisbecausesteppermotorscanmoveatdiscretesteps,provideaccurateangularpositioninformation,andareeasiertocontrol.WiththeuseofL297andL298chipstogether,arelativelylowpricecanbeusedtoformasteppermotordrivecircuitwithgoodperformance.StandardsteppermotordriverusingL297andL298ICIIIL297andL298Hardwarecircuit3.1L297OverviewL297isasteppermotorcontroller.Itissuitableforthecontrolofbipolartwo-phasesteppermotorsorunipolarfour-phasesteppermotors.Therearethreedrivemodes:half-step,full-step,andwave.Theon-chipPWMchoppercircuitallowsswitchingcontrolofthewindingcurrent.Anotablefeatureofl297isthatonlyclock,direction,andmodeinputsignalsarerequired.Thephaserequiredbythesteppingmotorisgeneratedinsidethecircuit,whichgreatlyreducestheburdenontheCPU.L297hasthefollowingcharacteristics:Normal/wavedriveHalf/fullstepmodesClockwise/anticlockwisedirectionSwitchmodeloadcurrentregulationProgrammableloadcurrentFewexternalcomponentsResetinputhomeoutputEnableinput3.2L298OverviewL298isahigh-voltageandhigh-currentdualfull-bridgedriverwithtwoH-bridges.ItacceptsstandardTTLlogiclevelsignalsandcandrivesteppermotorswithavoltageof46Vand2.5Aperphaseorbelow.Eachbridgehasanenableinput,whichallowsorprohibitsthedevicetoworkwithoutbeingaffectedbytheinputsignal.Theemittersofthetwolow-endtransistorsofeachbridgeareconnectedtogetherandledoutforexternaldetectionresistance.Itsetsanadditionalpowerinputterminaltomakethelogicpartworkatlowvoltage.Figure1.L298internallogicdiagram(halfofthediagram)L298hasthefollowingcharacteristics:Operatingsupplyvoltageupto46vTotalDCcurrentupto4A25wratedpower2enablecontrolterminalstoenableordevicewithoutinputtingsignals.Abletodriveatwo-phasesteppermotor,four-phasesteppermotorortwoDCmotorsBuilt-instabilivolttube78M05canbeusedtoobtain5vfrompowersupply.(Mustbeusedwithanexternal5vlogicsupplywhendrivevoltageisgreaterthan12vtoprotectthechip)LowsaturationvoltageOvertemperatureprotectionLogical0inputvoltageupto1.5V(highnoiseimmunity)Operatingtemperature:-23Cto130CStorageTemperature:-40Cto150C3.3L297andL298CircuitL297andL298canbeusedtomakeatwo-phasebipolarsteppermotordrivecircuit.Itisdrivenbyaconstantcurrentmode,andthepeakcurrentofeachphasecanreach2A.L297isasteppermotorcontrollerthatisusedtogeneratetwo-phasebipolar.Drivesignal(A,B,C,D)andmotorcurrentsettings.L298isusedtodrivethepoweroutputofthesteppermotor.Itisdrivenbyadoublefullbridgemode.Duetothebipolardrive,themotorcoilisfullyutilizedtoenableintothemotorcanachievethebestdrive.WhentwopiecesofL297areusedtodrivethetwowindingsofasteppingmotorthroughL298,andtheVrefcorrespondingtoeachwindingischangedthroughtwoD/Aconverters,asteppingmotorsubdivisiondrivingcircuitisformed.TheprincipleofL297+L298drivewiringisshowninFigure2.PortsP0~P4arerespectivelyconnectedtothecorrespondingcontrolterminalsofL297.Then,throughthereasonablearrangementofthesoftware,thepurposeofcontrollingthemotortorotateintheexpecteddirectionisachieved.Figure2.ElectricalschematicdiagramInaddition,theterminal1ofL297isthesynchronousterminal,whichcanbeconnectedtotheterminal1ofanothergroupofL297andL298drivecircuits.Inthisway,thetwosetsofdriverscanbesynchronizedtoachievetheeffectofdrivingmultiplemotorsatthesametime.IVSoftwaredesignUseClanguagetowriteprogramcode:P0_0=1;//CWP0_1~1;//HALFP0_3=1;//ENABLEP0_2=1;//RESETP0_7=1;//CLOCKTMODone0X01;//TlTH0=(a4000/256);TL0=one(4000%256);TR0=1;for(;;){TH0=one(4000/256);TL0=one(4000%256);do{}while(!TF0);P0_7=!P0_7;//CLOCKTF0=0;}Thespeedofthemotorspeedcanbecontrolledbythetimer.Figure3.WaveformdiagramgeneratedbyL297AccordingtothewaveformgeneratedbyL297,infact,whentheCPUportresourcesarenottight,theCPUcanbeusedtosimulateoutput.Theabovehardwarecircuitsandsoftwareprogramshavebeentestedandarecompletelypractical.FAQWhatisl298n?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.WhatisL297?TheL297integratesallthecontrolcircuitryrequiredtocontrolbipolarandunipolarsteppermotors.UsedwithadualbridgedriversuchastheL298Nformsacompletemicroprocessor-to-bipolarsteppermotorinterface.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.Whatistheuseofl298n?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.I.IntroductiontoGalvanometerThegalvanometerisanimportanttestinginstrument.Itisahigh-sensitivitymechanicalindicatingmeterfordetectingweakelectricity.Itisusedasazero-pointinginstrumentinbridgesandpotentiometers.Itcanalsobeusedtomeasureweakcurrents,voltagesandcharges..Accordingtotheinputmode,itcanbedividedintovoltagetypeandcurrenttype.Generally,voltagetypeismorecommonlyused.Fromthepaneldisplaymodeofthegalvanometer,itcanbedividedintothreetypes:pointertype,digitaltype,andmixedtype.Figure1ThegalvanometerThepointergalvanometercanconvenientlyobservethecontinuouslychangingcurrent,andintuitivelyjudgethedirectionofthecurrentfromthedeflectiondirection,soithasitsuniqueadvantagesinthebridgeexperiment.Thepointergalvanometerscurrentlyusedinphysicalexperimentshavethefollowingshortcomings:(1)Use9Vlaminatedbatterywithsmallcapacity,shortbatterylifeandhighcost;(2)ItsinternalamplifyingcircuitadoptsOP07orICL7650design,withoutpowermanagementcapability,itiseasytocausethebatterytobeconsumedunnecessarily;(3)Duetotheuseofmanydiscretecomponents,theamplifierispronetodriftandunstable.Thispaperusesagalvanometerdesignedbasedonthethree-op-amphighcommon-moderejectionratioandhighstabilityinstrumentationamplifierAD620andMicrochips6-pinMCUPIC10F206tosolvetheaboveproblems.CatalogI.IntroductiontoGalvanometerII.HardwareSystemDesign2.1HardwareSystemBlockDiagram2.2InstrumentationAmplifierAD6202.3MicrocontrollerPIC10F2062.4AmplifyingCircuitofGalvanometer2.5PowerMonitoringandPowerManagementCircuitofGalvanometerIII.SoftwareSystemIV.ConclusionFAQOrdering&QuantityII.HardwareSystemDesign2.1HardwareSystemBlockDiagramTheblockdiagramofthehardwaresystemisshowninFigure2.TheDCvoltagesignalfirstpassesthroughananti-radiofrequencyinterferencelow-passfiltercircuit,weakenstheinterferencesignal,andthensendsittotheinstrumentationamplifierAD620fordifferentialamplification,andthendrivesthepointermetertodisplay.The6-pinmicrocontrollerPIC10F206isresponsibleforthepowermonitoringandpowermanagementofthegalvanometer.Thewholegalvanometeronlyuses3VDCpowersupplyconnectedinserieswithtwoAAbatteries.Figure2Thehardwaresystemblockdiagramofthegalvanomete2.2InstrumentationAmplifierAD620AD620isalow-costandhigh-precisioninstrumentationamplifierlaunchedbytheAmericanADIcompany.Ithasthecharacteristicsofhighaccuracy,lowoffsetvoltage(maximum50uV)andlowoffsetdrift(maximum0.6uV℃/),anditsmaximumoperatingcurrentisonly1.3mA,onlyanexternalresistorisneededtosetthegain,andthegainrangeis1to10000.Inaddition,AD620adopts8-pinSOICandDIPpackage,thesizeissmallerthanthediscretecircuitdesign,andthepowerconsumptionislower,soitissuitableforbattery-poweredinstrumentapplications.Figure3AD620BecauseitsinputstageusesSuperetaprocessing,itcanachievealowinputbiascurrentofupto1.0nA.AD620hasalowinputvoltagenoiseof9nV/Hzat1kHz,apeak-to-peaknoiseof0.28Vinthefrequencybandfrom0.1Hzto10Hz,andaninputcurrentnoiseof0.1pA/Hz,soitcanbeusedasapreamplifierwell.Atthesametime,the0.01%settlingtimeofAD620is15s,whichisverysuitableformultiplexingapplications;andthecostisverylow,enoughtorealizethedesignofaninstrumentationamplifierperchannel.2.3MicrocontrollerPIC10F206PIC10F206isalow-cost,6-pin8-bitflashmicrocontrollerintroducedbytheUSMicrochipcompanythatusesRISCarchitecture.PIC10F206has512wordsofFLASH,24bytesofSRAM,watchdogtimer(WDT),power-onresetcircuit(POR)anddeviceresettimer(DRT)and4MHzinternaloscillator,thuseliminatingtheneedforexternalresetcircuitandthecrystaloscillator,reducessystemcostandpowerconsumption,andenhancessystemreliability.Italsohasawideoperatingvoltagerange(20Vto5.5V).Theabovecharacteristicsmakeitsuitableforapplicationsinprice-sensitiveandbattery-poweredareas.Figure4PIC10F2062.4AmplifyingCircuitofGalvanometerTheamplifyingcircuitofgalvanometertakestheinstrumentamplifierAD620asthecoreelement,asshowninFigure5.ThedifferentialsignaloutputbytheDCbridgeisinputfromthesocketJ1,passesthroughtheanti-radiofrequencyinterferencelow-passfiltercircuit[2]formedbyR1,R2,C1,C2,C3,andreachestheinstrumentationamplifierAD620afterweakeningtheinterferencesignal.D1,D2andR1,R2togetherformtheinputprotectioncircuitofthegalvanometer,whichcanwithstandinputvoltagesoftensofvolts.R3,R4providealoopfortheinputbiascurrentofAD620[1]toensurethatitcanworkstablyandreliably.TheresistanceR0andpotentiometerRP1betweenpin1andpin8ofAD620aregainadjustmentresistors,denotedasRG.R0isconnectedinserieswithRP1tolimittheupperlimitofthemagnificationto495times.ThepotentiometerRP2andR5,R6formthezeroadjustmentcircuitofthegalvanometertogether,realizezeroadjustmentbychangingthevoltageoftheREFpinofAD620.R7andC7formtheoutputlow-passfilterofAD620.R7,D3,D4constitutetheprotectioncircuitofthepointermeterhead.Figure5TheamplifyingcircuitofgalvanometerThemaximumsensitivityofagalvanometerisusually10uV/degreeto15uV/degree,whichcanwellmeettherequirementsoftheexperiment.TheinternalresistanceRgofthegalvanometermeterheadis4.7k,thegainadjustmentresistanceRG=R0+RP1,takeR0=100,R7=1k,whenRP1is0,theamplificationfactorofAD620isTakingintoaccountthepartialpressureofR7andtheinternalresistanceRgofthemeter,themagnificationofthegalvanometerisThecurrentsensitivityofthemeterheadis1Aminute/degree,sothevoltagesensitivityofthemeterheadis4700Vminute/degree.ThesensitivityofthegalvanometerisS=4700/G=115V/divisionMeettherequirementsofphysicalexperiments.2.5PowerMonitoringandPowerManagementCircuitofGalvanometerFigure6isthepowermonitoringandpowermanagementcircuitofthegalvanometer.TheGP2pinofthemicrocontrollerPIC10F206isconnectedwiththeP-channelMOSFETtubeQ1,thepurposeistocontrolwhethertosupplypowertotheamplifyingcircuitofthegalvanometer.WhenGP2outputislowlevel,Q1isturnedon,andthesystemsuppliespowertotheamplifiercircuit.TheroleofICL7660inpowerconversionhereistoconvert+VSto-VS.R8,R9andtheanalogcomparatorinsidePIC10F206togetherformthepowersupplyvoltagemonitoringcircuit.ThenegativeinputterminalCINoftheanalogcomparatorisconnectedtotheinternalreferencevoltageofthesingle-chipmicrocomputer(thenominalvalueofthevoltageis06V),andthepositiveinputterminalCIN+isconnectedwiththepartialpressureofR8andR9.BecausethelowestoperatingvoltageofAD620is23V,fromaconservativepointofview,thelowerlimitoftheoperatingvoltageissetto2.5V.Whenthepositivepowersupplyvoltageislessthan2.5V,thevoltageofCIN+islessthan0.6V,andthecomparatoroutputisreversed.Afterthemirocontrollerdetectsthisevent,theGP2outputshighlevel,turnsoffthepowersupplyoftheamplifiercircuit,andthenexecutestheSLEEPinstructiontomakethemicrocontrollerentersleepstatus.Figure6PowermonitoringandpowermanagementcircuitofgalvanometerInordertosavepowerconsumption,whentheworkingvoltageisnormal,thegalvanometershouldenterthesleepstate(iesoftshutdown)afterworkingforaperiodoftime,anditcanbeawakenedatanytimewhenitneedstowork.ButtonS1issetforthisfunction.Theworkingtimeofthegalvanometerispresetto15minutes.Whentheworkingtimeisup,theGP2ofthesingle-chipmicrocomputeroutputsahighlevel,shutsoffthepowersupplyoftheamplifyingcircuit,andthenexecutestheSLEEPinstructiontomakethemicrocontrollerenterssleepstate.Inthesleepstate,ifS1ispressed,thepinlevelofGP3willchange.Thiseventwillresetthemicrocontroller(note:PIC10F206hasnoconventionalinterruptfunction)andwakeupthemicrocontroller.Inthesleepstate,thecurrentconsumptionofthegalvanometerislessthan0.1A,whichisverypower-saving,sothereisnoneedtoworryaboutforgettingtoturnoffthepowersupplyofthegalvanometerandconsumingthebattery.III.SoftwareSystemWhenthegalvanometerispoweredon,themicrocontrollerfirstperformssysteminitialization,thensuppliespowertoICL7660andAD620,andthenturnsontheanalogcomparatortocheckwhetherthesupplyvoltageisappropriate.Ifthevoltageisappropriate,continuetosupplypowertotheamplifiercircuit,andthenexecutea15-minutecountdown.IfS1ispressedduringthisperiod,thetimingtimeisresetto15minutes.Whenthe15-minutecountdownisup,thesingle-chipmicrocomputerturnsoffthepowersupplyoftheamplifiercircuit,andthenentersthesleepstate(ie,softshutdown).TheflowchartoftheprocedureisshownasinFig.7.Figure7FlowchartoftheprocedureIV.ConclusionThisarticlediscussesthegalvanometerbasedoninstrumentationamplifierAD620andmicrocontrollerPIC10F206,whichhasstableperformanceandlowpowerconsumption.Thecurrentisabout4mAduringnormaloperation,andthecurrentconsumedinsleepmodeislessthan0.1uA,whichisverysuitableforbatterypowersupply.TheuseoftwoAAbatteriesforpowersupplysavesbatterycost.Thesoftshutdownfunctioncaneffectivelypreventbatteryconsumptioncausedbyforgettingtoturnoffthepower.FAQWhatisAD620?AD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyrequiresanexternalresistortosetthegain.Thegainrangeis1to10,000.CanIchangeAD620toAD623whenmakingMCUproducts?BothAD620andAD623aresingleinstrumentationamplifiers,andthepinarrangementisexactlythesame.Themaindifferenceis:AD620mustusepositiveandnegativepowersupplies,AD623canbeapositiveandnegativepowersupplyorasinglepowersupply.IftheoriginalboardisAD620,youcanreplaceitwith623;iftheoriginalboardisAD623,youmaynotbeabletoreplaceitwith620(itdependsonwhetherthepowersupplyoftheoriginalboardcircuitisdualpowersupplyorsinglepowersupply).AfterreplacingAD620andAD623insingle-chipproducts,theprogramcanworknormallywithoutmodification.WhatisthedifferencebetweenAD620BRandAD620AN?Theirpackagesaredifferent.WhatistheoutputresistanceofAD620?Howtoadjustit?AD620isakindoflowpowerconsumptioninstrumentamplifier,itsoutputresistanceisabout10K,thisistheinherentcharacteristicofthischip,generallyitisdifficulttoadjust.Ifyouhaverequirementsforoutputresistance,youcangenerallyuseanexternalcircuittosolveit.IsAD620apositivephaseamplificationorareversephaseamplification?AD620isaninstrumentamplifier,theoutputvoltageis[(Vin+)-(Vin-)]*gain.Ifthedesiredsignalis(Vin+)-(Vin-),thegainispositive,whichisequivalenttopositiveamplification.Conversely,ifthedesiredsignalis(Vin-)-(Vin+),thegainisequivalenttonegative,whichisequivalenttoreverseamplification.Whatisaninstrumentationamplifier?Instrumentationamplifier,animprovementofthedifferentialamplifier,hasaninputbuffer,doesnotrequireinputimpedancematching,sothattheamplifierissuitableformeasurementandelectronicinstruments

IDescriptionTheperformanceandstructureofthesteppermotordriverchipL297/L298areanalyzed.Atthesametime,combinedwiththeAT89C52single-chipmicrocomputer,asimplemethodofdrivingasteppermotorisintroduced.Thisbloggivesthecontrolschematicdiagram.Theactualmeasurementshowsthatthesteppingmotordrivesystemdesignedbythismethodhasthecharacteristicsofsimplehardwarestructure,easysoftwareprogrammingandlowprice.CatalogIDescriptionIIIntroductionIIIWorkingprincipleVIHardwareVSoftwareCompositionVIConclusionOrdering&QuantityIIIntroductionWhatisasteppingmotor?Asteppingmotorisaprecisionactuatorthatconvertselectricalpulsesignalsintoangulardisplacementorlineardisplacement.Thesteppingmotorhasthecharacteristicsofconvenientcontrolandsmallsize.Therefore,itiswidelyusedinnumericalcontrolsystems,automaticproductionlines,automaticinstruments,plotters,andcomputerperipherals.L297andL298caneasilyformasteppingmotordriver,andcombinedwithAT89C52single-chipmicrocomputerforcontrol.Thatis,itispossibletoformasteppermotordrivecircuitwithgoodperformanceatarelativelycheapprice.IIIWorkingprincipleSinceasteppermotorisanactuatorthatconvertselectricalpulsesignalsintolinearorangulardisplacement,itcannotbedirectlyconnectedtoACandDCpowersupplies.Instead,aspecialdevice,asteppingmotor,mustbeusedtocontrolthedriver.AtypicalsteppingmotorcontrolsystemisshowninFigure1.Thecontrollercansendoutpulsesignalswhosepulsefrequencycanbecontinuouslychangedfromafewhertztotensofkilohertz.Itprovidesapulsetrainfortheringdistributor.Themainfunctionoftheringdistributoristodistributethepulsesequencefromthecontrollinkaccordingtoacertainrule.Thenitisamplifiedbythepoweramplifierandaddedtotheinputterminalsofthesteppingmotordrivepowersupplytodrivetherotationofthesteppingmotor.Therearetwomaincategoriesofringdistributors:Oneistousecomputersoftwaredesignmethodstoachievethefunctionsrequiredbytheringdivider,usuallycalledasoftringdivider.Theotherisaringdistributorcomposedofhardware.Usuallycalledahardringdistributor.Thepoweramplifiermainlyamplifiesthesmalleroutputsignaloftheringdistributortoachievethepurposeofdrivingthesteppermotor.Figure1.TypicalsteppermotorcontrolblockdiagramVIHardwarehesteppermotorcontrolledintheblogisafour-phaseunipolar35BY48HJ120decelerationsteppermotor.TheblockdiagramofthesteppermotorcontroldriverdesignedinthisblogisshowninFigure2.ItconsistsofAT89C52single-chipmicrocomputer,optocoupler,integratedchipsL297andL298.Figure2.BlockdiagramofsteppermotorcontroldriverThesteppermotorintroducedintheblogisafour-phaseunipolar35BY48HJ120decelerationsteppermotor.TheblockdiagramofthesteppermotorcontroldriverdesignedinthisarticleisshowninFigure2.ItiscomposedofAT89C52single-chipmicrocomputer,photoelectriccoupler,integratedchipsL297andL298.AT89C52isalow-voltage,high-performance8-bitCMOSmicrocontrollerfromATMELintheUnitedStates.Thechiphasabuilt-in8Kbytesofre-erasableFlashmemory,256bytesofRAM,three16-bittimers,andaprogrammableserialUARTchannel.Therefore,itissufficienttocompletethesimplecontrolofthesteppermotor.L297isasteppingmotorcontroller(includingringdistributor).L298isadoubleHbridgedriver.Theinterfaceofthemicroprocessortothedouble-bridgesteppingmotorcomposedofthemisshowninFigure3.Theadvantageofthiscombinationisthatitrequiresfewcomponents.Asaresult,theassemblycostislow,thereliabilityishigh,andthespaceissmall.Andthroughsoftwaredevelopment,theburdenofmicrocomputerscanbesimplifiedandreduced.Inaddition,L297andL298areindependentchips,sotheapplicationisveryflexible.TheL297chipisahardwareloopintegratedchipthatcangeneratefour-phasedrivesignalsforcomputer-controlledtwo-phasebipolarorfour-phaseunipolarsteppermotors.TheheartoftheL297isasetofdecodersthatcangeneratevariousrequiredphasesequences.Thispartiscontrolledbytwoinputmodes,directioncontrol(CW/CCW)andHALF/FULL,andsteppingclockCLOCK.Itadvancesthedecoderfromonesteptoanother.Thedecoderhasfouroutputpointsconnectedtotheoutputlogicsectiontoprovidethephasesequencerequiredbythesuppressionandchoppingfunctions.Therefore,L297cangeneratethree-phasesequencesignals,correspondingtothreedifferentworkingmodes:thehalf-stepmode(HALFSTEP).Basicstep(FULLSTEP,fullstep)one-phaseexcitationmethod.Basicsteptwo-phaseexcitationmethod.Insidethepulse,thedistributorisa3bitreversiblecounter,plussomecombinationallogictogenerate8stepsofGraycodetimingsignalpercycle.Thisisthetimingsignalofthehalf-stepworkingmode.Atthistime,theHALF/FULLsignalishigh.IfHALF/FULLissettoalowlevel,thebasicstepworkingmodeisobtained,thatis,thedoublefour-beatfull-stepworkingmode.Figure3.L297PictureAnotherimportantcomponentofL297isthetwoPWMchopperstocontrolthephasewindingcurrentstoachieveconstantcurrentchoppingcontroltoobtaingoodtorque-frequencycharacteristics.Eachchopperconsistsofacomparator,anRSflip-flopandanexternalsamplingresistor.Acommonoscillatorisalsoprovidedtoprovidetriggerpulsesignalstothetwochoppers.InFigure5,thefrequencyfisdeterminedbytheexternal16-pinRCnetwork.WhenR10k,f=1/0.69RC.Whentheclockoscillatorpulsesetsthetriggerto1,themotorwindingphasecurrentrises.WhenthevoltageonRsofthesamplingresistorrisestothereferencevoltageUref,thecomparatorflipstoresettheflip-flop,thepowertransistoristurnedoff,andthecurrentdrops,waitingforthearrivalofthenextoscillationpulse.Inthisway,theoutputofthetriggerisaconstantfrequencyPWMsignal,whichmodulatestheoutputsignalofL297,andthepeakvalueofthewindingphasecurrentisdeterminedbyUref.TheinputoftheCONTROLterminalofL297determinesthatthechopperactsonthephaselinesA,B,C,DorthesuppressionlinesINH1andINH2.WhenCONTROLishigh,ithascontroleffectonA,B,C,D;Whenitislowlevel,itcontrolsINH1andINH2,sothatthesteeringandtorqueofthemotorcanbecontrolled.TheL298chipisahigh-voltage,high-currentdualfull-bridgedriver.L298isdesignedtoacceptstandardTTLlogiclevelsignalsanddriveinductiveloads.Forexample,relays,cylindricalcoils,DCmotorsandsteppingmotors.Ithastwosuppressinputstomakethedeviceimmunetotheinputsignal.Theemittersofthetriodesofeachbridgeareconnectedtogether,andthecorrespondingexternalterminalscanbeusedtoconnectperipheralsensingresistors.Anotherinputpowersupplycanbeinstalledtoenablethelogictoworkunderlowvoltage.TheL298chipisanintegratedchipinamulti-wattin-linepackagewith15leads.Figure4.L298PictureInFigure5,AT89C52isconnectedtothemicrocomputerthroughtheserialportafterMAX232levelconversion,andacceptsinstructionsfromthehostcomputer.Thensendclocksignal,positiveandnegativesignal,resetsignalandenablecontrolsignaltoL297.Inthecircuit,resistorsR13andR15areusedtoadjustthereferencevoltageofthechoppercircuit.Thisvoltagewillbecomparedwiththemagnitudeofthepotentialfedbackthroughthepins13,14todeterminewhethertoperformchoppingcontrol.Inordertoachievethepurposeofcontrollingthepeakvalueofthemotorwindingcurrentandprotectingthesteppermotor.BecauseL297hasachoppingconstantcurrentcircuitinside,thepeakvalueofthewindingphasecurrentisdeterminedbyUref.WhentwopiecesofL297areusedtodrivethetwowindingsofthesteppingmotorthroughL298,andtheUrefofeachphasewindingischangedthroughtwoD/Aconverters,thesteppingmotorsubdivisiondrivingcircuitisformed.Inaddition,inordertoeffectivelysuppresselectromagneticinterferenceandimprovethereliabilityofthesystem,anisolationcircuitcomposedoftwo16-pinphotoelectriccouplingdevicesTLP521-4isusedinthesingle-chipandsteppingmotordrivecircuit.AsshowninFigure5.Figure5.SchematicdiagramofsteppermotorcontroldriverItsfunctionistocutoffthedirectelectricalconnectionbetweenthemicrocontrollerandthesteppingmotordrivecircuit.Inthisway,theseparateconnectionofthesingle-chipmicrocomputerandthedrivingcircuitsystemgroundisrealized,andtheinterferencesignalgeneratedbythedrivingcircuitworkingunderthehigh-currentinductiveloadandtheinterferencesignalgeneratedbythesuddenchangeofthegridloadisseriallyconnectedtothesingle-chipmicrocomputerthroughtheline,whichaffectsthenormaloperationofthesingle-chipmicrocomputer.VSoftwareCompositionInthiscircuit,setP1.0portasthemotorstartbutton.P1.1,P1.2,P1.3arespeedselectionbuttons,thespeedisfromlowtohigh.P1.4isthemotorstopbutton.Themaximumspeedofthethreespeedsis500pps,1000pps,and2000pps.RXD,TXDhavebeenconnectedtotheserialportbyMAX232levelconversion.Inaddition,thestartandstopfrequencyofasteppermotorislow,generallybetween100-250Hz.Themaximumoperatingfrequencyisrequiredtobehigher,usually1-3kHz.Inordertoensurethatitwillnotlosestepduringthewholeprocessofstarting,runningandstopping,butalsocanreachthetargetpositionaccuratelyassoonaspossible,therunningspeedmusthaveanacceleration-constantspeed-decelerationprocess.Here,thecommonlyuseddiscretemethodisusedtoapproximatetheidealtrapezoidalaccelerationanddecreasecurve,asshowninFigure5.Thatis,thetimerinterruptmodeisusedtocontinuouslychangethesizeofthetimerloadvalue.Inthisexample,fortheconvenienceofcalculation,theloadingvaluerequiredforthespeedofeachdiscretepointisconvertedintotherequiredtimingtimebytheformulaandsolidifiedintheROMofthesystem.Here,TH0=(65536-time)/256,TL0=(65536-time)%256isusedtocalculatetheloadingvalue,andtimerepresentsthetimingtimerequiredforeachstep.Thesystemusesthelook-uptablemethodtofindoutthetimerequiredduringoperation,therebygreatlyreducingthetimeoccupiedbytheCPUandimprovingthecorrespondingspeedofthesystem.Therefore,theprogramismainlycomposedofcontrolmainprogram,accelerationanddecelerationsubroutine,andthemainprogramblockdiagramisshowninFigure6.Figure6.MainblockdiagramVIConclusionTheinnovationofthisblogistoproposetheapplicationofsingle-chipmicrocomputerandL297,L298integratedcircuitstoformasteppermotorcontroldriver.Ithastheadvantagesoffewercomponents,highreliability,lessspace,andlowassemblycost.IDescriptionDoyouknowtheDCregulatedpowersupply?DCregulatedpowersupplyiswidelyusedinindustrialproductionanddailylife,anditsdesignoccupiesaveryimportantpositioninpowersupplytechnology.Therefore,basedontheanalysisoftheproblemsofthetraditionalDCstabilizedpowersupply,themethodandcalculationofeachpartofthe5V,1ADCstabilizedpowersupplybasedonL7805CTaredescribed.Besides,itcanalsoprovidea5VDCpowersupplyforcounters,decoders,anddigitaltubestorealizeadditionandsubtractioncounting.ThesystemcircuitbasedonL7805CTintroducedinthisblogissimple,stable,easytocontrol,cost-effective,andisofhighuse-value.CatalogIDescriptionIIIntroductionIIIDesignrequirementsforDCstabilizedpowersupplyIVHardwareunitcircuitdesign4.1Overallstructureofthepowersupply4.2ComponentselectionVApplicationVIConclusionFAQOrdering&QuantityIIIntroductionWiththecontinuousdevelopmentofelectronictechnology,thedesignrequirementsofelectronicequipmentforpowersupplyaregettinghigherandhigher,fromtraditionalrequirementstohigh-quality,high-efficiency,andhigh-stabilitytomeettheneedsofobjects.ThenormaloperationofelectronicdevicesrequiresDCpower.DCpowersourcesincludesolarbatteries,accumulators,anddrybatteries.Butdoyouknowwhichoneisthemostcost-effective?Ofcourse,themostcost-effectivemethodistoconverttheACpowerprovidedbythegridintotherequiredDCpower.Mostelectronicequipmentusesthismode,andthethree-terminalregulatoristhemostwidelyused.AlthoughpeopleusemanytypesofDCstabilizedpowersupplieswithdifferentfunctions,theprinciplesaresimilar.ThevoltageregulatorchipusedinthesystemintroducedinthisblogisL7805CT.L7805CThastheadvantagesofsmallsize,simpleexternalwiring,stableoperationandstrongapplicability.Itcanmeetpeoplesrequirementsinlife,study,andwork.IIIDesignrequirementsforDCstabilizedpowersupplyThedesignrequirementsoftheDCregulatedsingle-channelpowersupplybasedonL7805CTareasfollows:InputACvoltage220V;OutputDCvoltage+5V;OutputDCcurrent1A;Theoutputrippleofthecircuitislessthan50mV;Theequivalentinternalresistanceislessthan0.15;Ripplecoefficientislessthan0.002%;Voltageadjustmentrate0.001%;Voltagestabilizationcoefficient0.005%.IVHardwareunitcircuitdesign4.1OverallstructureofthepowersupplyThisdesignfocusesontheknowledgeandskillsinvolvedinthemainlinksoftheDCpowersupply,andcompletesthecircuitdesignandproductionof220VACinputand5V,1ADCoutput.TheDCpowersupplyisusuallycomposedoffourlinks:PowerTransformers;Rectifiercircuit;Filtercircuit;Regulatorcircuit.AsshowninFigure1.Figure1.BlockdiagramofDCpowersupply4.1.1PowertransformerThepowertransformerconvertsthehigh-voltageACmainspowerintotheappropriatevoltageACandsendsittothesingle-phasebridgerectifiercircuit.Whenchoosingapowertransformermodel,theparametersweneedtoconsiderarecapacityandoutputvoltage.4.1.2RectifiercircuitTherectifiercircuitusestheunidirectionalconductivityofthediodetocompletetherectification.Commonlyusedrectifiercircuitsareasfollows:single-phasehalf-waverectifiercircuit,single-phasefull-waverectifiercircuitandsingle-phasebridgerectifiercircuit.Throughcomparativeresearch,inordertoovercometheshortcomingsofhalf-waverectification,theL7805CT-basedsystemusesasingle-phasebridgerectifiercircuit.Itconsistsof4diodesVD1~VD4connectedintheformofabridge.Whetheritisapositivehalf-cycleoranegativehalf-cycle,thedirectionofthecurrentflowingtotheloadRListhesame.BothtransformtheACvoltageoutputbythesecondarywindingofthepowertransformerintoapulsatingDCvoltage.Thereversevoltagethateachdevicebearsisthepeakvalueofthepowersupplyvoltage,andsymmetricalcurrentflowsthroughthepositiveandnegativehalfcyclesofthetransformer,theutilizationrateishigherthanthatofthefull-waverectifiercircuit,andthecurrentrippleisreduced.Therefore,thereisnounidirectionalmagnetization.4.1.3FiltercircuitTherectifieddirectcurrentcontainsarelativelylargealternatingcurrentcomponent,andthepulsationcoefficientisrelativelylarge,soitcannotbedirectlyusedasthepowersupplyforelectroniccircuits.FiltercircuitsarecommonlyusedtoremoveorreducetheACcomponentintheoutputvoltage,sothatpureACpowerisusedonthedevice.Thisdesignusestheenergystoragecharacteristicsofcapacitorsandinductorstosetappropriateparameters.Whenthecircuitvoltagerises,theenergystorageelementstoresenergy.Whenthevoltagedrops,theenergystorageelementreleasesenergy,soastoachievethepurposeofreducingpulsation.Thecapacityofthecapacitorisrelatedtothedischargetime.Tomakethefilteringeffectbetter,acapacitorwithalargercapacitycanbeusedasthefiltercapacitor.ThefiltercapacitorisgenerallyselectedasRLC(3~5)T/2.4.1.4VoltagestabilizingcircuitTheDCvoltageobtainedaftertheACpowerisrectifiedandfilteredoftenfluctuateswiththefluctuationofthegridvoltage,temperaturechanges,andloadresistancechanges.Then,thequalityofpowersupplywillbereduced,affectingtheoperationoftheequipment.Therefore,avoltagestabilizingcircuitneedstobeaddedbetweenthefiltercircuitandtheloadlinktoachievethepurposeofstabilizingpowersupply.ThechipL7805CThasthecharacteristicsofgoodvoltageregulationperformance,highreliability,easyinstallationandlowcost.Therefore,thelinearstabilizedpowersupplyreplacesthediscretestabilizedcircuitandiswidelyused.Inordertoreducetheinterferenceandmakethevoltagestabilizingcircuitworknormally,theinputvoltageshouldbeatleast2.5~3Vhigherthantheoutputvoltage.4.2Componentselection4.2.1SelectionofpowertransformerConsideringthediodeforwardvoltagedrop,wireresistance,andpowergridfluctuations,theoutputvoltageUIofthethree-terminalintegratedregulatorshouldmeet:Where:Uomaxisthemaximumoutputofregulatedpowersupply;(UI-UO)ministheminimumvoltagedifferencebetweentheinputandoutputoftheintegratedregulator;UIisthechangeoftheinputvoltagecausedbythefluctuationofthepowergrid(generallytakenas10%ofthesumofUO,(UI-UO)min,andUIP).Fortheintegratedthree-terminalregulator,when(UI-UO)min=2~10V,ithasbettervoltageregulationcharacteristics.WhenU1=10VWhenU2=9VInasingle-phasebridgerectifiercircuit,therelationshipbetweenthetransformersecondarywindingcurrentI2andthecapacitorfilteroutputcurrentIIis:Insummary,chooseatransformerwithacapacityof15VAand9V.4.2.2SelectionofrectifierdiodeBecause,thecurrentflowingthrougheachrectifierdiodeinthebridgecircuitis:Themaximumreversepeakvoltageofeachrectifierdiodeis:Insummary,selectthetransistorIN4001,itsparametersare:ID=1A,URM=50V.4.2.3SelectionoffiltercapacitorAlthoughthecurrentpassingthroughthediodeisapulsatingcurrent,becausethecapacitorChasanenergystorageanddischargefunction,thisreducesthedegreeofvoltagepulsationacrosstheloadRLandincreasestheaveragevalue.TheaveragevalueandsmoothnessoftheDCvoltageontheloadarerelatedtothedischargetimeconstant=RLC.ThelargerthevalueofCorRL,theslowerthedischargeofC.ThelargertheoutputDCvoltagevalue,thebetterthefilteringeffect;otherwise,theworse.Generallytake:TheACpowersupplyinsomeAsiancountriesisa50Hzsinewave,with50identicalwaveformspersecond.Afterfull-waverectification,boththepositiveandnegativehalfwavesbecomepulsatingdirectcurrentinthesamedirection.Atthistime,thereare100identicalwaveformspersecond,thatis,f=100Hz.Sothefiltercapacitorcapacityis:amongthem,TheoutputDCvoltageofthecapacitorfiltercircuitisestimatedas:Insummary,twoelectrolyticcapacitorsof2200Fand50Vcanbeused,andtheyareconnectedinparallel.Inordertofilterouttheinterferenceofhigh-frequencysignalsandimprovethedynamiccharacteristicsofthepowersupply,a105pF,50Vhigh-frequencyceramiccapacitorisconnectedinparallelatbothendsofthefiltercapacitor.4.2.4Howtochooseathree-terminalintegratedvoltageregulatorTheconditionthatthepowerconsumptionofthethree-terminalintegratedvoltageregulatormustmeetisgreaterthan5Wandtheoutputvoltageis5V.ThisdesignchoosesL7805CT,theoutputvoltageis4.8~5.2V,thequiescentcurrentis4.2~8mA,andthemaximumoutputcurrentcanbe1.5A,whichmeetsthedesignrequirements.Consideringthelargeoutputcurrent,aheatsinkneedstobeadded.VApplicationAdoptthedesignbasedonL7805CTtoprovide5VDCpowersupplyforcounter,decoderanddigitaltube.Usethebuttontogenerateasingleclock,realizethecountofmodulo10throughthestandardcountercircuit,andgeneratethecorrespondingcode.Thevalueisoutputtotheintegrateddecodingcircuitthroughthedecodertodisplaythenumbers0-9.UsetheDPsectionoftheintegrateddecodingcircuitasapower-onindication.Thecounterhasaresetbutton,andtheintegrateddecodingcircuitadoptsacommoncathodestructuretorealizeadditionandsubtractioncounting.asshowninfigure2.Figure2.L7805CircuitVIConclusionThe5V,1ADCpowersupplydesignbasedontheL7805CTdescribedinthisblogcanprovide5VDCpowersupplyforcounters,decoders,anddigitaltubestoachieveadditionandsubtractioncounting.ThedesigncircuitoftheL7805CTissimple,withfewcomponents,lowpowerconsumptionandstable.Therefore,itcanbeextendedtootherobjectapplicationsasaDCstabilizedpowersupplytoprovideelectricalenergy.FAQWhatisl7805?AvoltageregulatorICmaintainstheoutputvoltageataconstantvalue.7805IC,amemberof78xxseriesoffixedlinearvoltageregulatorsusedtomaintainsuchfluctuations,isapopularvoltageregulatorintegratedcircuit(IC)....7805ICprovides+5voltsregulatedpowersupplywithprovisionstoaddaheatsink.WhatistheworkingprincipleofIC7805?AvoltageregulatorICmaintainstheoutputvoltageataconstantvalue.7805IC,amemberof78xxseriesoffixedlinearvoltageregulatorsusedtomaintainsuchfluctuations,isapopularvoltageregulatorintegratedcircuit(IC).Thexxin78xxindicatestheoutputvoltageitprovides.HowdoItesta7805withamultimeter?TurnontheDCpowersupplyandadjusttheoutputvoltageofabout8Vorslightlylarger.Oralternativelyyoucanuseabattery9V-12Vasvoltagesource.Lookatthevoltmeterpanelwhenyousetthevoltage.PrepareaDCvoltmeterreadingsonvoltagerange50VtomeasuretheoutputvoltageoftheIC7805.Howdoes7805regulatevoltage?For7805IC,itis+5VDCregulatedpowersupply.ThisregulatorICalsoaddsaprovisionforaheatsink.Theinputvoltagetothisvoltageregulatorcanbeupto35V,andthisICcangiveaconstant5Vforanyvalueofinputlessthanorequalto35Vwhichisthethresholdlimit.