Tkool Electronics

I.IntroductionTheamplificationofweaksignalshashighrequirementsandhighdifficulty.Thesignalamplificationisrelatedtotherequirementsofstabilityandaccuracyofsignalamplification.Differentialamplificationtechnologyhasthecharacteristicsofsuppressingcommonmodesignalsandonlyamplifyingdifferentialmodesignalswithhighgain,soitisappliedtosmallsignalamplificationtechnology.ThesystemdesignadoptstheAD620chipwithdifferentialamplificationfunctiontoamplifytheweakvoltagesignalofthestrainsensortoachievethehighprecisionrequirementsofthesystem.Thisarticleusesvirtualinstrumenttechnologytocollectandanalyzetheamplifiedsignal,andwritethecorrespondingdisplayinterface.Themeasurementdataisanalyzedbythesecond-orderinterpolationmethodtoverifytheaccuracyofthecircuit.AD620CatalogI.IntroductionII.SystemDesignIII.SystemHardwareCircuitDesign3.1PressureMeasurementCircuit3.2VoltageSignalAmplifierCircuit3.3ReferenceVoltageSourceCircuitandVoltageZeroingCircuit3.4Voltage-currentConversionCircuitIV.TheOverallSoftwareDesignoftheSystemV.QuantitativeTestingandResultAnalysis5.1DataProcessingMethod5.2DataProcessingResults5.3ErrorAnalysisVI.ConclusionFAQOrdering&QuantityII.SystemDesignThesystemisprovidedwithtwovoltagesof12Vand5VfromaDCstabilizedsource.Whensetting12Vpowersupply,thesystemvoltageoutputfullrangeis5V,andthesensorwithstandsstaticpressurefullrangeis19.6N.Whenmeasuringwithinthefull-scalerange,themaximumabsoluteerrorofthestaticpressuresignalis9.810-3N,andtherelativeerroris0.02%.Theoutputsignaloftheloadcellprovidestwooutputmodes:voltageoutputandcurrentoutputaftertheamplifiercircuit.III.SystemHardwareCircuitDesignTheoveralldesignprocessofthesystemisshowninFigure1.ThesystemhardwarecircuitismainlycomposedofLC7012loadcell,AD620instrumentationamplifier,referencevoltagesource,voltagezeroingcircuit,signalfilteringandshapingcircuitandvoltage-currentconversioncircuit.Figure1Systemhardwarecircuitoveralldesignprocess3.1PressureMeasurementCircuitPressuremeasurementadoptsLC7012loadcell,withfullbridgemeasurementcircuit.LC7012loadcellhasthefollowingtwocharacteristicswhensubjectedtopressure:(1)Underthesamepressure,thestrainofthesensorstraingaugeandtheoutputvoltageofthebridgeareconstantandhavenothingtodowiththeprecisepositionofthepressureactingontheloadendofthesensor.(2)Theoutputvoltageandpressureofthefullbridgecircuitcomposedofstraingaugesarebasicallylinear.The4piecesofresistancestraingaugesintheLC7012loadcellareattachedtothestrainzoneofthedouble-holebeam.Whenthereisstaticpressure,thedouble-holebeamproducesquadrilateraldeformationundertheactionofthepressureandthesupportingforceofthesystemchassisonthedouble-holebeam.Thefourstraingaugesareconnectedtoafullbridgecircuitinafullbridgemode.Undertheexcitationofthebridgevoltage,differentweakvoltagesignalsareoutputwithdifferentpressures,andtheamplifiercircuitamplifiestheweakvoltagesignalssentbythebridge.Thefull-bridgeequal-armbridgehassimplestructure,strongsymmetry,highsensitivity,andgoodconsistencyoftheparametersofeacharm.Theeffectsofvariousinterferencescancanceleachother,forexample,itcansuppresstheeffectsoftemperaturechangesandsuppresstheinterferenceoflateralforces.Itiseasiertosolvetheproblemofcompensationoftheloadcell.Thefull-bridgemeasurementcircuitenablestheoutputoftheweakvoltagesignaltoeliminateerrorscausedbythecircuititselfasmuchaspossible,andprovidestheinitialguaranteefortheoverallaccuracyofthesystem.3.2VoltageSignalAmplifierCircuitInordertoimprovetheamplificationaccuracyoftheweakvoltagesignaloutputbythebridge,thesignalamplifyingcircuitselectstheAD620chipproducedbyADIasthecoreelement,anddesignsaspecialadjustablereferencevoltagesourceforittomeetthereferencevoltagerequirementsofdifferentvoltagesources.Andtheneedtoaccuratelyamplifyweaksignals.Figure2AD620PinoutAD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyneedsanexternalresistortosetthegain.Thegainrangeis1to10000dB.AndAD620powerconsumptionislow,themaximumoperatingcurrentis1.3mA.AD620hasthecharacteristicsofhighprecision(maximumlinearity4010-6),lowoffsetvoltage(maximum50V)andlowoffsetdrift(maximum0.6V/℃),makingitanidealchoiceforprecisiondataacquisitionsystemssuchassensorinterfaces.Figure2showsitspinarrangement.AD620monolithicstructureandlasercrystaladjustmentallowcircuitcomponentstobecloselymatchedandtracked,thusensuringtheinherenthighperformanceofthecircuit.AD620isathree-op-ampintegratedinstrumentationamplifierstructure,inordertoprotectthehighprecisionofgaincontrol,theinputtransistorprovidesdifferentialbipolarinput,andusesprocesstoobtainlowerinputbiascurrent,throughthefeedbackoftheinputstageinternalop-amp,Keepthecollectorcurrentoftheinputtransistorconstant,andaddtheinputvoltagetotheexternalgaincontrolresistorRG.AD620internalgainresistanceisadjustedtoanabsolutevalueof24.7k,soanexternalresistancecanbeusedtoachievepreciseprogrammingofthegain.ThegainformulaisThevoltagesignalamplifiedbytheAD620canpassthroughafilteringandshapingcircuitandbedisplayedindigitalformwithadigitaltubethroughtheanalog-to-digitalconvertermodule.Inordertofullyutilizeanddemonstratethefunctionsofvirtualinstruments,thesystemusesLabVIEWtodesignthecorrespondingsignalacquisitionandprocessingprogramanddisplayinterface.3.3ReferenceVoltageSourceCircuitandVoltageZeroingCircuitThereferencevoltagesourcecircuitismainlycomposedofaZenerdiodeLM285,alow-powerdualoperationalamplifierchipLM258,avariableresistorandanumberoffixedresistanceresistors,asshowninthelowerleftpartofFigure3.ThisreferencevoltagesourcecircuitcanprovideAD620with1.25Vor2.5Vaccuratereferencevoltage.Figure3VoltagesignalamplifiercircuitThevoltagestabilizingdiodeLM285providestheprimarystablevoltage,butthetemperaturedriftofthediodeislarge,andthevoltagestabilizationvalueofdifferentdiodesinthesamebatchisnotthesame,sothecorrespondingauxiliaryvoltagestabilizingcircuitmustbedesignedforit.TheoperationalamplifierLM258U1AamplifiesthevoltagefromtheZenerdiodeandfeedsbacktheoutputvoltagethroughthefeedbackresistorR2,makingtheoutputvoltagemorestable.ResistorR5andpotentiometerW1dividetheoutputvoltageoftheZenerdiode.PotentiometerW1hastwofunctions:(1)AdjustingW1canmakethevoltagefollowercomposedofoperationalamplifierLM258U1Bhavedifferentoutputvoltages,andthenprovidedifferentstablereferencevoltagestoAD620.(2)ThepotentiometerW1alsoplaysaroleofzeroadjustmentontheamplifyingcircuitcomposedofAD620.Thevoltagefollowerisusedbecausethevoltagefollowercanincreasetheinputimpedanceandreducetheoutputimpedance,andtherequirementofthepowersupplyisthatthecircuithasasmalleroutputresistance.AD620itselfhasaninternalzeroadjustmentfunction,butaccordingtoactualmeasurement,itisfoundthatwhenthedifferentialinputiszero,theoutputisnotzero,butaboutafewtenthsofmV.Therefore,inordertoimprovetheaccuracyoftheoutput,itisnecessarytoperformtheAD620Externalzeroadjustment,byprovidingdifferentreferencevoltagestotheAD620referencevoltagepins,theoutputvoltageoftheinstrumentationamplifierAD620canbezerowhenthedifferentialinputiszero.ThecircuitjustadjustsW1tomaketheoutputterminalofthevoltagefollowerhavedifferentvoltageoutput,adjuststhereferencevoltageofAD620,thusplaystheroleofzeroadjustmenttoAD620.TheinstabilityofthereferencevoltagewilldirectlyaffectthestabilityoftheamplifiercircuitcomposedofAD620,andleadtoinaccuracyofthefinaloutputresult.Therefore,thesystemdoesnotdirectlyusetherelativelystable-12Vor-5VprovidedbytheDCstabilizedsourceasthereferencevoltage.3.4Voltage-currentConversionCircuitThevoltage-currentconversioncircuitenablesthesystemtooutputintheformofcurrent.TheAD620iscombinedwithanAD705operationalamplifierandtworesistors(asshowninFigure4)toformaquietcurrentsource.AD705providesabufferforthereferencepin.Ensuregoodcommonmoderejection(CMR)performance.TheoutputvoltageofAD620appearsontheresistanceRL,thelatterconvertsitintoelectriccurrentoutput.Figure4Schematicdiagramofvoltage-currentconversioncircuitAD705isalow-power,bipolaroperationalamplifierwithabipolarfieldeffecttransistorinputstage.Therefore,ithasthecharacteristicsofhighinputimpedance,lowinputoffsetvoltage,smallinputbiascurrent,andsmallinputoffsetvoltagedrift.TheinputbiascurrenthasreachedthepAlevel.Itnotonlyhasmanyadvantagesofbipolarfieldeffecttransistorsandbipolaroperationalamplifiers,butalsoovercomesthedefectoflargebiascurrentdriftinthefulltemperaturerange.Inthefulltemperaturerange,thetypicalvalueofthebiascurrentofAD705onlyincreasesby5times,andthebiascurrentofthegeneralbipolarfieldeffecttransistoroperationalamplifierincreasesby1,000times.ComparedwithOP07,thetemperaturedriftvalueis1/2ofOP07,themaximuminputbiascurrentisonly1/5ofOP07,andtheinputoffsetvoltageisonly1/20ofOP07.Becauseitisabipolarfieldeffecttransistorinputpole,thesignalsourceimpedanceismuchhigherthanOP07,whileitsDCaccuracyremainsunchanged.IV.TheOverallSoftwareDesignoftheSystemThesystemsoftwareiswritteninLabVIEW.LabVIEWisagraphicalprogramminglanguage,whichiswidelyusedinvariousfieldsasastandardfordataacquisitionandinstrumentcontrolsoftware.LabVIEWisapowerfulandflexiblesoftware.Useittoeasilybuildyourownvirtualinstrument.Inthecaseofonepieceofhardware,differentfunctionsofdifferentinstrumentscanberealizedbychangingthesoftwareprogramming,whichisconvenientandfast.Combinedwiththenewdevelopmentdirectionofthecurrenttestingfieldinstruments,thefinaloutputanalogvoltagesignaliscollectedbyAdvantechsUSB4716universaldataacquisitionmoduleandtransmittedtothecomputer.UseNIvirtualinstrument(LabVIEW)todesignvoltagesignalacquisitioncontrolprogramandvoltagedatareal-timedisplayinterface.UseLabVIEWsoftwareplatformtoanalyzeandprocessthedigitalvoltagesignalfromUSB4716.ThepartprogramofLabVIEWvoltagesignalacquisitioncontrolanddisplayisshowninFigure5.Figure5VoltagesignalacquisitionprogramV.QuantitativeTestingandResultAnalysis5.1DataProcessingMethodSecond-orderinterpolation(parabolicinterpolation):select(x0,y0),(x1,y1),(x2,y2)correspondinginterpolationequationsfromasetofdata.5.2DataProcessingResultsInordertoobtainanaccuratecorrespondencebetweenpressureandvoltageandfacilitatesubsequentanalysisofabsoluteandrelativeerrors,theexperimentusesstaticmeasurementmethodstomeasureaseriesofstaticpressurevalues,andquantitativelyanalyzetheexperimentalresultstodeterminetheaccuracyofthecircuit.Commonlyusedwaveformtimedomainandfrequencydomainanalysismethods.Table1Brightness/ContrastComparisonPressure/N0...2.94...8.829.8...13.72...19.6219.6Voltage/V0...0.75...2.2472.498...3.498...4.755.001Measure20staticpressurevaluesfromsmalltolargewithinthefullscalerange,andmakethepressureincrement△thesame.Let△=0.98N,andusethesecond-orderinterpolationmethodtoanalyzetherelationshipbetweenvoltageandpressure.SelectthreerepresentativepointsfromTable1:(x0,y0)=(0,0);(x1,y1)=(2.498V,9.8N);(x2,y2):(5.001V,19.6N).Bringinsecond-orderinterpolationTherelationshipcurvebetweenthepressureonthesensorandthesystemoutputvoltageisY=(-1.56810-3)x2+3.927x(3)5.3ErrorAnalysisTheabsoluteerrorreflectsthedeviationofthemeasuredvaluefromthetruevalue,thatis,theabsolutevalueofthedifferencebetweenthemeasuredvalueandthetruevalue.Theabsoluteerrorcanbedefinedas:=|X-L|(4)Intheformula,istheabsoluteerror;Xisthemeasuredvalue;Listhetruevalue.Relativeerroristheratioofabsoluteerrortothemeasuredvalueortheaveragevalueofmultiplemeasurements,andtheresultisusuallyexpressedasapercentage,soitisalsocalledpercentageerror.Absoluteerrorcanindicatethereliabilityofameasurementresult,whilerelativeerrorcancomparethereliabilityofdifferentmeasurementresults.Whenmeasuringwiththesametool,thelargerthemeasuredvalue,thesmallertherelativeerrorofthemeasurementresult.TheabsoluteerrorandrelativeerrorofthestraingaugepressuresensortestsystemareshowninFigure6andFigure7.Thetwofiguresrespectivelyshowtheabsoluteerrorandrelativeerrorcurvesoftwootherdataprocessingmethods:linearinterpolationandaverageselectionmethod.ItcanbeseenfromFigure6andFigure7thatthecalculationaccuracyofthesecond-orderinterpolationmethodishigherthantheothertwomethods,whichalsoprovesthatthechoiceofthedataprocessingmethodiscorrect.Figure6AbsoluteerrorcurveFigure7RelativeerrorcurveVI.ConclusionKnownfromtherelativeerrorandabsoluteerrorgraphthat,themeasurementresulterrorofthecircuitintherangeof0~4.9Nisrelativelylarge,butitstillmeetsthesystemdesignrequirements.Afteranalyzingthesensorandtheexperimentalmeasurementcircuit,itisbelievedthatthereasonforthelargererrorcomesfromtherigidityofthecantileverbeammaterialofthesensorandtheflexibleinfluenceoftheviscousmaterialthatfixesthestraingauge.Becausetheaccuracyoftheweakvoltagesignaloutputbythebridgeisaffected,theerrorisalsoamplifiedafterpassingthroughtheamplifyingcircuit,resultinginalargererrorintheexperimentalresultwhenthemeasuredvalueissmall.Insummary,thepressuresignalamplificationsystemsatisfiesthedesignrequirementsofabsolutefull-scaleerror9.810-3Nandrelativeerror.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

74LS05

I.IntroductionTheamplificationofweaksignalshashighrequirementsandhighdifficulty.Thesignalamplificationisrelatedtotherequirementsofstabilityandaccuracyofsignalamplification.Differentialamplificationtechnologyhasthecharacteristicsofsuppressingcommonmodesignalsandonlyamplifyingdifferentialmodesignalswithhighgain,soitisappliedtosmallsignalamplificationtechnology.ThesystemdesignadoptstheAD620chipwithdifferentialamplificationfunctiontoamplifytheweakvoltagesignalofthestrainsensortoachievethehighprecisionrequirementsofthesystem.Thisarticleusesvirtualinstrumenttechnologytocollectandanalyzetheamplifiedsignal,andwritethecorrespondingdisplayinterface.Themeasurementdataisanalyzedbythesecond-orderinterpolationmethodtoverifytheaccuracyofthecircuit.AD620CatalogI.IntroductionII.SystemDesignIII.SystemHardwareCircuitDesign3.1PressureMeasurementCircuit3.2VoltageSignalAmplifierCircuit3.3ReferenceVoltageSourceCircuitandVoltageZeroingCircuit3.4Voltage-currentConversionCircuitIV.TheOverallSoftwareDesignoftheSystemV.QuantitativeTestingandResultAnalysis5.1DataProcessingMethod5.2DataProcessingResults5.3ErrorAnalysisVI.ConclusionFAQOrdering&QuantityII.SystemDesignThesystemisprovidedwithtwovoltagesof12Vand5VfromaDCstabilizedsource.Whensetting12Vpowersupply,thesystemvoltageoutputfullrangeis5V,andthesensorwithstandsstaticpressurefullrangeis19.6N.Whenmeasuringwithinthefull-scalerange,themaximumabsoluteerrorofthestaticpressuresignalis9.810-3N,andtherelativeerroris0.02%.Theoutputsignaloftheloadcellprovidestwooutputmodes:voltageoutputandcurrentoutputaftertheamplifiercircuit.III.SystemHardwareCircuitDesignTheoveralldesignprocessofthesystemisshowninFigure1.ThesystemhardwarecircuitismainlycomposedofLC7012loadcell,AD620instrumentationamplifier,referencevoltagesource,voltagezeroingcircuit,signalfilteringandshapingcircuitandvoltage-currentconversioncircuit.Figure1Systemhardwarecircuitoveralldesignprocess3.1PressureMeasurementCircuitPressuremeasurementadoptsLC7012loadcell,withfullbridgemeasurementcircuit.LC7012loadcellhasthefollowingtwocharacteristicswhensubjectedtopressure:(1)Underthesamepressure,thestrainofthesensorstraingaugeandtheoutputvoltageofthebridgeareconstantandhavenothingtodowiththeprecisepositionofthepressureactingontheloadendofthesensor.(2)Theoutputvoltageandpressureofthefullbridgecircuitcomposedofstraingaugesarebasicallylinear.The4piecesofresistancestraingaugesintheLC7012loadcellareattachedtothestrainzoneofthedouble-holebeam.Whenthereisstaticpressure,thedouble-holebeamproducesquadrilateraldeformationundertheactionofthepressureandthesupportingforceofthesystemchassisonthedouble-holebeam.Thefourstraingaugesareconnectedtoafullbridgecircuitinafullbridgemode.Undertheexcitationofthebridgevoltage,differentweakvoltagesignalsareoutputwithdifferentpressures,andtheamplifiercircuitamplifiestheweakvoltagesignalssentbythebridge.Thefull-bridgeequal-armbridgehassimplestructure,strongsymmetry,highsensitivity,andgoodconsistencyoftheparametersofeacharm.Theeffectsofvariousinterferencescancanceleachother,forexample,itcansuppresstheeffectsoftemperaturechangesandsuppresstheinterferenceoflateralforces.Itiseasiertosolvetheproblemofcompensationoftheloadcell.Thefull-bridgemeasurementcircuitenablestheoutputoftheweakvoltagesignaltoeliminateerrorscausedbythecircuititselfasmuchaspossible,andprovidestheinitialguaranteefortheoverallaccuracyofthesystem.3.2VoltageSignalAmplifierCircuitInordertoimprovetheamplificationaccuracyoftheweakvoltagesignaloutputbythebridge,thesignalamplifyingcircuitselectstheAD620chipproducedbyADIasthecoreelement,anddesignsaspecialadjustablereferencevoltagesourceforittomeetthereferencevoltagerequirementsofdifferentvoltagesources.Andtheneedtoaccuratelyamplifyweaksignals.Figure2AD620PinoutAD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyneedsanexternalresistortosetthegain.Thegainrangeis1to10000dB.AndAD620powerconsumptionislow,themaximumoperatingcurrentis1.3mA.AD620hasthecharacteristicsofhighprecision(maximumlinearity4010-6),lowoffsetvoltage(maximum50V)andlowoffsetdrift(maximum0.6V/℃),makingitanidealchoiceforprecisiondataacquisitionsystemssuchassensorinterfaces.Figure2showsitspinarrangement.AD620monolithicstructureandlasercrystaladjustmentallowcircuitcomponentstobecloselymatchedandtracked,thusensuringtheinherenthighperformanceofthecircuit.AD620isathree-op-ampintegratedinstrumentationamplifierstructure,inordertoprotectthehighprecisionofgaincontrol,theinputtransistorprovidesdifferentialbipolarinput,andusesprocesstoobtainlowerinputbiascurrent,throughthefeedbackoftheinputstageinternalop-amp,Keepthecollectorcurrentoftheinputtransistorconstant,andaddtheinputvoltagetotheexternalgaincontrolresistorRG.AD620internalgainresistanceisadjustedtoanabsolutevalueof24.7k,soanexternalresistancecanbeusedtoachievepreciseprogrammingofthegain.ThegainformulaisThevoltagesignalamplifiedbytheAD620canpassthroughafilteringandshapingcircuitandbedisplayedindigitalformwithadigitaltubethroughtheanalog-to-digitalconvertermodule.Inordertofullyutilizeanddemonstratethefunctionsofvirtualinstruments,thesystemusesLabVIEWtodesignthecorrespondingsignalacquisitionandprocessingprogramanddisplayinterface.3.3ReferenceVoltageSourceCircuitandVoltageZeroingCircuitThereferencevoltagesourcecircuitismainlycomposedofaZenerdiodeLM285,alow-powerdualoperationalamplifierchipLM258,avariableresistorandanumberoffixedresistanceresistors,asshowninthelowerleftpartofFigure3.ThisreferencevoltagesourcecircuitcanprovideAD620with1.25Vor2.5Vaccuratereferencevoltage.Figure3VoltagesignalamplifiercircuitThevoltagestabilizingdiodeLM285providestheprimarystablevoltage,butthetemperaturedriftofthediodeislarge,andthevoltagestabilizationvalueofdifferentdiodesinthesamebatchisnotthesame,sothecorrespondingauxiliaryvoltagestabilizingcircuitmustbedesignedforit.TheoperationalamplifierLM258U1AamplifiesthevoltagefromtheZenerdiodeandfeedsbacktheoutputvoltagethroughthefeedbackresistorR2,makingtheoutputvoltagemorestable.ResistorR5andpotentiometerW1dividetheoutputvoltageoftheZenerdiode.PotentiometerW1hastwofunctions:(1)AdjustingW1canmakethevoltagefollowercomposedofoperationalamplifierLM258U1Bhavedifferentoutputvoltages,andthenprovidedifferentstablereferencevoltagestoAD620.(2)ThepotentiometerW1alsoplaysaroleofzeroadjustmentontheamplifyingcircuitcomposedofAD620.Thevoltagefollowerisusedbecausethevoltagefollowercanincreasetheinputimpedanceandreducetheoutputimpedance,andtherequirementofthepowersupplyisthatthecircuithasasmalleroutputresistance.AD620itselfhasaninternalzeroadjustmentfunction,butaccordingtoactualmeasurement,itisfoundthatwhenthedifferentialinputiszero,theoutputisnotzero,butaboutafewtenthsofmV.Therefore,inordertoimprovetheaccuracyoftheoutput,itisnecessarytoperformtheAD620Externalzeroadjustment,byprovidingdifferentreferencevoltagestotheAD620referencevoltagepins,theoutputvoltageoftheinstrumentationamplifierAD620canbezerowhenthedifferentialinputiszero.ThecircuitjustadjustsW1tomaketheoutputterminalofthevoltagefollowerhavedifferentvoltageoutput,adjuststhereferencevoltageofAD620,thusplaystheroleofzeroadjustmenttoAD620.TheinstabilityofthereferencevoltagewilldirectlyaffectthestabilityoftheamplifiercircuitcomposedofAD620,andleadtoinaccuracyofthefinaloutputresult.Therefore,thesystemdoesnotdirectlyusetherelativelystable-12Vor-5VprovidedbytheDCstabilizedsourceasthereferencevoltage.3.4Voltage-currentConversionCircuitThevoltage-currentconversioncircuitenablesthesystemtooutputintheformofcurrent.TheAD620iscombinedwithanAD705operationalamplifierandtworesistors(asshowninFigure4)toformaquietcurrentsource.AD705providesabufferforthereferencepin.Ensuregoodcommonmoderejection(CMR)performance.TheoutputvoltageofAD620appearsontheresistanceRL,thelatterconvertsitintoelectriccurrentoutput.Figure4Schematicdiagramofvoltage-currentconversioncircuitAD705isalow-power,bipolaroperationalamplifierwithabipolarfieldeffecttransistorinputstage.Therefore,ithasthecharacteristicsofhighinputimpedance,lowinputoffsetvoltage,smallinputbiascurrent,andsmallinputoffsetvoltagedrift.TheinputbiascurrenthasreachedthepAlevel.Itnotonlyhasmanyadvantagesofbipolarfieldeffecttransistorsandbipolaroperationalamplifiers,butalsoovercomesthedefectoflargebiascurrentdriftinthefulltemperaturerange.Inthefulltemperaturerange,thetypicalvalueofthebiascurrentofAD705onlyincreasesby5times,andthebiascurrentofthegeneralbipolarfieldeffecttransistoroperationalamplifierincreasesby1,000times.ComparedwithOP07,thetemperaturedriftvalueis1/2ofOP07,themaximuminputbiascurrentisonly1/5ofOP07,andtheinputoffsetvoltageisonly1/20ofOP07.Becauseitisabipolarfieldeffecttransistorinputpole,thesignalsourceimpedanceismuchhigherthanOP07,whileitsDCaccuracyremainsunchanged.IV.TheOverallSoftwareDesignoftheSystemThesystemsoftwareiswritteninLabVIEW.LabVIEWisagraphicalprogramminglanguage,whichiswidelyusedinvariousfieldsasastandardfordataacquisitionandinstrumentcontrolsoftware.LabVIEWisapowerfulandflexiblesoftware.Useittoeasilybuildyourownvirtualinstrument.Inthecaseofonepieceofhardware,differentfunctionsofdifferentinstrumentscanberealizedbychangingthesoftwareprogramming,whichisconvenientandfast.Combinedwiththenewdevelopmentdirectionofthecurrenttestingfieldinstruments,thefinaloutputanalogvoltagesignaliscollectedbyAdvantechsUSB4716universaldataacquisitionmoduleandtransmittedtothecomputer.UseNIvirtualinstrument(LabVIEW)todesignvoltagesignalacquisitioncontrolprogramandvoltagedatareal-timedisplayinterface.UseLabVIEWsoftwareplatformtoanalyzeandprocessthedigitalvoltagesignalfromUSB4716.ThepartprogramofLabVIEWvoltagesignalacquisitioncontrolanddisplayisshowninFigure5.Figure5VoltagesignalacquisitionprogramV.QuantitativeTestingandResultAnalysis5.1DataProcessingMethodSecond-orderinterpolation(parabolicinterpolation):select(x0,y0),(x1,y1),(x2,y2)correspondinginterpolationequationsfromasetofdata.5.2DataProcessingResultsInordertoobtainanaccuratecorrespondencebetweenpressureandvoltageandfacilitatesubsequentanalysisofabsoluteandrelativeerrors,theexperimentusesstaticmeasurementmethodstomeasureaseriesofstaticpressurevalues,andquantitativelyanalyzetheexperimentalresultstodeterminetheaccuracyofthecircuit.Commonlyusedwaveformtimedomainandfrequencydomainanalysismethods.Table1Brightness/ContrastComparisonPressure/N0...2.94...8.829.8...13.72...19.6219.6Voltage/V0...0.75...2.2472.498...3.498...4.755.001Measure20staticpressurevaluesfromsmalltolargewithinthefullscalerange,andmakethepressureincrement△thesame.Let△=0.98N,andusethesecond-orderinterpolationmethodtoanalyzetherelationshipbetweenvoltageandpressure.SelectthreerepresentativepointsfromTable1:(x0,y0)=(0,0);(x1,y1)=(2.498V,9.8N);(x2,y2):(5.001V,19.6N).Bringinsecond-orderinterpolationTherelationshipcurvebetweenthepressureonthesensorandthesystemoutputvoltageisY=(-1.56810-3)x2+3.927x(3)5.3ErrorAnalysisTheabsoluteerrorreflectsthedeviationofthemeasuredvaluefromthetruevalue,thatis,theabsolutevalueofthedifferencebetweenthemeasuredvalueandthetruevalue.Theabsoluteerrorcanbedefinedas:=|X-L|(4)Intheformula,istheabsoluteerror;Xisthemeasuredvalue;Listhetruevalue.Relativeerroristheratioofabsoluteerrortothemeasuredvalueortheaveragevalueofmultiplemeasurements,andtheresultisusuallyexpressedasapercentage,soitisalsocalledpercentageerror.Absoluteerrorcanindicatethereliabilityofameasurementresult,whilerelativeerrorcancomparethereliabilityofdifferentmeasurementresults.Whenmeasuringwiththesametool,thelargerthemeasuredvalue,thesmallertherelativeerrorofthemeasurementresult.TheabsoluteerrorandrelativeerrorofthestraingaugepressuresensortestsystemareshowninFigure6andFigure7.Thetwofiguresrespectivelyshowtheabsoluteerrorandrelativeerrorcurvesoftwootherdataprocessingmethods:linearinterpolationandaverageselectionmethod.ItcanbeseenfromFigure6andFigure7thatthecalculationaccuracyofthesecond-orderinterpolationmethodishigherthantheothertwomethods,whichalsoprovesthatthechoiceofthedataprocessingmethodiscorrect.Figure6AbsoluteerrorcurveFigure7RelativeerrorcurveVI.ConclusionKnownfromtherelativeerrorandabsoluteerrorgraphthat,themeasurementresulterrorofthecircuitintherangeof0~4.9Nisrelativelylarge,butitstillmeetsthesystemdesignrequirements.Afteranalyzingthesensorandtheexperimentalmeasurementcircuit,itisbelievedthatthereasonforthelargererrorcomesfromtherigidityofthecantileverbeammaterialofthesensorandtheflexibleinfluenceoftheviscousmaterialthatfixesthestraingauge.Becausetheaccuracyoftheweakvoltagesignaloutputbythebridgeisaffected,theerrorisalsoamplifiedafterpassingthroughtheamplifyingcircuit,resultinginalargererrorintheexperimentalresultwhenthemeasuredvalueissmall.Insummary,thepressuresignalamplificationsystemsatisfiesthedesignrequirementsofabsolutefull-scaleerror9.810-3Nandrelativeerror.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

IntroductionTheLM393comparatorcanberegardedasequivalenttothemostpopularversionoftheLM358operationalamplifier.Althoughanyoperationalamplifiercanbeusedasavoltagecomparator,theLM393comparatorprovesitsadvantagebyprovidinganopencollectoroutputtomakeitsuitablefordrivingloads.Theoutputtransistorcandriveloadsupto50Vand50mAandissuitablefordrivingmostTTL,MOSandRTLloads.Thetransistorcanalsoisolatetheloadfromthesystemground.ThisVedioIntroducesLM393DualComparatorwithOpenCollectorOutputfromIntegratedCircuitCatalogIntroductionCADCAESymbolsDocumentandMediaECCNUNSPSCLM393PinConfigurationandFunctionsPopularitybyRegionBasicParametersProductManufacturerFeaturesProductRangeAdvantagesAlternativeModelsFunctionalBlockDiagramOrdering&QuantityDocumentandMediaComponentDatasheetLM393DatasheetApplicationNotesApplicationDesignGuidelinesforLM393LM393PinConfigurationandFunctionsTheLM393datasheetprovidedaboveisforyourreference,sothatyoucanunderstandthephysicaldimensionsofallpackagesinmoredetail.Theconfigurationofall8pinsandthefunctionofeachpinareasfollows:ThefunctionofLM393pinsareasfollows:BasicParametersNumberofchannels2OutputtypeOpen-collectorPropagationdelaytime1.3sVs(Max)36VVs(Min)2VVos(offsetvoltage@25C)(Max)5mVIqperchannel(Typ)0.225mAInputbiascurrent(+/-)(Max)50nARail-to-railOutRatingCatalogOperatingtemperaturerange0℃to70℃FeaturesStandardcomparatorVICR(Max)34.5VVICR(Min)0VApprox.price1ku|0.06US$FeaturesImprovedspecificationsofB-versionMaximumrating:upto38VESDrating(HBM):2kVLowinputoffset:0.37mVLowinputbiascurrent:3.5nALowsupply-current:200ApercomparatorFasterresponsetimeof1secExtendedtemperaturerangeforLM393BAvailableintiny2x2mmWSONpackageB-versionisdrop-inreplacementforLM293,LM393andLM2903,AandVversionsCommon-modeinputvoltagerangeincludesgroundDifferentialinputvoltagerangeequaltomaximumratedsupplyvoltage:38VLowoutputsaturationvoltageOutputcompatiblewithTTL,MOS,andCMOSAdvantagesVacuumrobotSinglephaseUPSServerPSUCordlesspowertoolWirelessInfrastructureApplicancesBuildingAutomationFactoryautomationcontrolMotordrivesInfotainmentclusterFunctionalBlockDiagramCADCAESymbolsPackagePinsDownloadPDIP(P)8ViewoptionsSO(PS)8ViewoptionsSOIC(D)8ViewoptionsTSSOP(PW)8ViewoptionsVSSOP(DGK)8ViewoptionsECCNUNSPSCDescriptionValueECCNCodeEAR99HTSCode8542.39.00.01PopularitybyRegionProductManufacturerTexasInstrumentsInc.(TI)isanAmericantechnologycompanythatdesignsandmanufacturessemiconductorsandvariousintegratedcircuits,whichitsellstoelectronicsdesignersandmanufacturersglobally.ItsheadquartersareinDallas,Texas,UnitedStates.TIisoneofthetoptensemiconductorcompaniesworldwide,basedonsalesvolume.TexasInstrumentssfocusisondevelopinganalogchipsandembeddedprocessors,whichaccountsformorethan80%oftheirrevenue.TIalsoproducesTIdigitallightprocessing(DLP)technologyandeducationtechnologyproductsincludingcalculators,microcontrollersandmulti-coreprocessors.Todate,TIhasmorethan43,000patentsworldwide.ProductRangeDevicesBoardsDeveloperToolsARMPROCESSORSAUTOMOTIVEPRODUCTSIDENTIFICATIONSECURITYKinetisCortex-MMicrocontrollersIn-VehicleNetworkNFCLPCCortex-MMicrocontrollersMicrocontrollersandProcessorsRFIDAlternativeModelsLM741LM358LM339LM324Afterreadingtheblog,haveyoubetterunderstandLM393?IfyouarealsointerestedinhowtoDIYyoursolartrackingcarbyusingLM393,youmaywishtobrowserighthererightnow!Finally,ifyouhaveanyquestionsaboutLM393,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!IIntroductionTheLM393isadualvoltagecomparator.thismeansthatitaccepts2inputsforcomparison.TheoutputloadresistanceofLM393comparatorcanbeconnectedtoanypowersupplyvoltagewithintheallowablepowersupplyvoltagerange,andisnotlimitedbythevoltagevalueoftheVccterminal.ThisoutputcanbeusedasasimpleopencircuittogroundSPS(whentheloadresistorisnotused),thesinkcurrentoftheoutputpartislimitedbythevalueofthedriverandthedevicethatcanbeobtained.Whenthelimitcurrent(16mA)isreached,theoutputtransistorwillexitandtheoutputvoltagewillrisequickly.Inthisblog,wewilldiscuss3waystousetheLM393comparatortobuildcircuits,including:InfraredObstacleAvoidanceModule,Ni-CdBatteryCharger,andPWMModulationCircuit.LM393imagesareforreferenceonly.Figure1.LM393ComparatorCatalogIIntroductionIILM393BasedInfraredObstacleAvoidanceModule2.1ModuleDescription2.2DescriptionofModuleParameters2.3ModuleInterfaceDescriptionIIILM393Ni-CdBatteryChargerIVLM393PWMModulationCircuitOrdering&QuantityIILM393BasedInfraredObstacleAvoidanceModuleFigure2.LM393InfraredObstacleAvoidanceModule2.1ModuleDescriptionThesensormodulehasstrongadaptabilitytoambientlight.Ithasapairofinfraredemittingandreceivingtubes.Thetransmittingtubeemitsinfraredraysofafrequency.Whenitencountersanobstacle(reflectingsurface)inthedetectiondirection,itwillbereflectedbackandreceivedbythereceivingtube.Afterthereceivedinfraredlightisprocessedbythecomparatorcircuit,thegreenindicatorlightwilllightup,andthesignaloutputinterfaceoutputsadigitalsignal(alow-levelsignal).Thedetectiondistancecanbeadjustedbythepotentiometerknob.Theeffectivedistancerangeis2-30cm,andtheoperatingvoltageItis3.3V-5V.Thedetectiondistanceofthesensorcanbeadjustedbyapotentiometer,whichhasthecharacteristicsofsmallinterference,easyassemblyandconvenientuse.Itcanbewidelyusedinmanysituationssuchasrobotobstacleavoidance,obstacleavoidancetrolley,pipelinecountingandblackandwhitelinetracking.2.2DescriptionofModuleParametersWhenthemoduledetectsanobstaclesignalinfront,thegreenindicatoronthecircuitboardlightsup,andtheOUTportcontinuouslyoutputsalow-levelsignal.Thedetectiondistanceofthismoduleis2~30cm,andthedetectionangleis35.Inaddition,thedetectiondistancecanbeadjustedbythepotentiometer:Byadjustingthepotentiometerclockwise,thedetectiondistanceincreases;Byadjustingthepotentiometercounterclockwise,thedetectiondistancedecreases;Thesensorisactiveinfraredreflectiondetection,sothereflectivityandshapeofthetargetisthekeytothedetectiondistance.Amongthem,theblackdetectiondistanceissmallandthewhiteislarge;thedistanceofsmallareasissmall,andthedistanceoflargeareasislarge;TheoutputportOUTofthesensormodulecanbedirectlyconnectedtotheIOportofthesingle-chipmicrocomputer,oritcandirectlydrivea5Vrelay;connectionmode:VCC-VCC;GND-GND;OUT-IO;TheLM393comparatorhasthecharacteristicsofstableoperation;3-5VDCpowersupplycanbeusedtopowerthemodule.Whenthepoweristurnedon,theredpowerindicatorlights;has3mmscrewholesforeasyfixingandinstallation;Circuitboardsize:3.2CM*1.4CM;Themodulehasadjustedthethresholdcomparisonvoltagethroughthepotentiometer.Unlessunderspecialcircumstances,pleasedonotadjustthepotentiometeratwill.2.3ModuleInterfaceDescriptionVCCexternal3.3V-5Vvoltage(canbedirectlyconnectedto5vmicrocontrollerand3.3vmicrocontroller);ConnectGNDexternallytoGND;OUTsmallboarddigitaloutputinterface(0and1);Theworkingcurrentiswithin10ma;BarriersensormoduleasshowninFigure3.Figure3.InfraredReflectiveSensorModuleIIILM393Ni-CdBatteryChargerThecost-effectivenickel-cadmiumbatterychargerformedbyLM393comparatorisshowninFigure4,whichhasthefollowingcharacteristics:Figure4.Nickel-CadmiumBatteryChargerConstantcurrentchargingisinterspersedwithlargecurrentdischarge.Theconstantcurrentchargingcurrentisabout300mA,andthedischargecurrentincreasesasthebatteryvoltageincreases.Whenthebatteryisnearlyfull,thedischargecurrentreaches400mA.Chargefor1.5secondsanddischargefor0.5secondsatintervals.Afterthehighcurrentchargingiscompleted,thereisabout5mAtricklecharging.Thebatteryvoltageisdetectedduringdischarge.Becausethevoltageduringchargingisalwayshigherthanthevoltageduringdischarging.Ifthereisanerrorbetweenthedetectionandtheactualworkingstateofthebatteryduringcharging,thedetectioncanmorereflectthecapacityofthebatterywhendischarging.Thenumberofrechargeablebatteriescanbe1to4.For500mAhnickel-cadmiumbatteries,thechargingtimeisabout2hours,whichcanmeetthegeneralneeds.IVLM393PWMModulationCircuitWeknowthatPWMgenerallyrequiresasawtoothwaveandacontrolvoltagetobecomparedwithacomparatortoobtainaPWMpulse.Thecomparator2ofLM393votagecomparatorwillbeusedasaPWMcomparator,whosenon-invertinginputendisthecontrolvoltageinputend,andtheinvertinginputendisthesawtoothwaveinputend.Theoutputterminal(pin7)isusedastheoutputterminaltosendthePWMdimmingsignaltotheIRNpinoftheIRS2540/1viatheisolationdiodeVD.TheLM393circuitofPWMModulationisshowninFigure5below.Figure5.PWMModulationCircuitThegenerationofthesawtoothwaveisrealizedbythecomparator1ofLM393.IfyoudonotlookatthecapacitorC1,thecomparator1isamultivibratorwithasquarewaveoutput.Inordertoobtainthesawtoothwave,acapacitorC1isconnectedinparallelwiththeCOMendoftheoutputendofthecomparator1.ThisisactuallythechargingprocessoftheoutputterminalsR1andC1ofthecomparator1.Ifthecapacitanceofthiscapacitorislargeenough,butbecausethechargingofC1requiresR1,andthedischargeofC1istheoutputtransistorofthecomparator,thentheriseandfallofthevoltageattheoutputofthecomparatorwillbeasymmetric,whichwillformanoscillatingsawtoothwave.Figure6.OscillatingSawtoothWaveDuetotheVBUSapplicationofthepowersupplyofthecircuitinthefigure,itneedstobesteppeddownwithRS,andthevoltageregulationofVD2andthepowersupplybypasscapacitorsC3andC4arerequired.Afterreadingtheblog,haveyoubetterunderstandLM393?IfyouarealsointerestedinhowtoDIYyoursolartrackingcarbyusingLM393,youmaywishtobrowserighthererightnow!Finally,ifyouhaveanyquestionsaboutLM393,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!

74LS05

IntroductionLM567isahigh-stabilitylow-frequencyintegratedphase-lockedloopdecoder.Duetoitsgoodnoisesuppressionabilityandcenterfrequencystability,itiswidelyusedinthedecodingofvariouscommunicationequipmentandthedemodulationcircuitofAMandFMsignals.LM567Imagesareforreferenceonly.LM567ToneDecoderCatalogIntroductionDocumentsandMediaPinConfigurationandFunctionsBasicParametersFeaturesApplicationsFunctionalBlockDiagramCircuitDiagramECCNUNSPSCProductManufacturerProductRangeOrdering&QuantityDocumentsandMediaComponentDatasheetsLM567(C)PinConfigurationandFunctionsThedatasheetprovidedaboveisforyourreference,sothatyoucanunderstandthephysicaldimensionsofallpackagesinmoredetail.Theconfigurationofall8pinsandthefunctionofeachpinareasfollows:PinConfigurationAndthefunctionofall8pinsandthefunctionofeachpinareasfollows:PinFunctionBasicParametersBrandNameTexasInstrumentsECCNCodeEAR99FactoryLeadTime1WeekHTSCode8542.39.00.01JESD-30CodeR-PDSO-G8JESD-609Codee3Length4.9mmManufacturerTexasInstrumentsManufacturerPartNumberLM567CMX/NOPBMoistureSensitivityLevel1NumberofFunctions1NumberofTerminals8OperatingTemperature-Max70CPackageBodyMaterialPLASTIC/EPOXYPackageCodeSOPPackageDescriptionSOP-8PackageEquivalenceCodeSOP8,.23PackageShapeRECTANGULARPackageStyleSMALLOUTLINEPartLifeCycleCodeActivePartPackageCodeSOICPbfreeCodeYesPeakReflowTemperature260℃PinCount8QualificationStatusNotQualifiedReachComplianceCodeCompliantRiskRank0.62RohsCodeYesSeatedHeight-Max1.75mmSupplyCurrent-Max15mASupplyVoltage-Nom5VSurfaceMountYESTelecomICTypeTONEDECODERCIRCUITTemperatureGradeCOMMERCIALTerminalFinishMatteTin(Sn)TerminalFormGULLWINGTerminalPitch1.27mmTerminalPositionDUALTime@PeakReflowTemperature-Max(s)NOTSPECIFIEDWidth3.91mmFeatures20to1FrequencyRangeWithanExternalResistorLogicCompatibleOutputWith100-mACurrentSinkingCapabilityBandwidthAdjustableFrom0to14%HighRejectionofOutofBandSignalsandNoiseImmunitytoFalseSignalsHighlyStableCenterFrequencyCenterFrequencyAdjustablefrom0.01Hzto500kHzApplicationsTheLM567tonedecoderisadevicecapableofdetectingwhetheraninputsignaliswithinaselectabledetectionrange.Thedevicehasanopencollectortransistoroutput,soanexternalresistorisrequiredtoreachtheappropriatelogiclevels.Whentheinputsignalisinthedetectionband,thedeviceoutputchangestotheLOWstate.TheinternalfreeoperatingfrequencyoftheVCOdefinesthecenterfrequencyofthedetectionband.AnexternalRCfilterisrequiredtoadjustthisfrequency.Thebandwidthinwhichthedevicewilldetectthedesiredfrequencydependsonthecapacityoftheloopfilterterminal.Usuallya1Fcapacitorisconnectedtothispin.LM567isgenerallyusedinthefollowingsituations:TouchToneDecodingPrecisionOscillatorFrequencyMonitoringandControlWideBandFSKDemodulationUltrasonicControlsCarrierCurrentRemoteControlsCommunicationsPagingDecodersFunctionalBlockDiagramCircuitDiagramThefollowingdescribestheclassiccircuitdiagramofthephase-lockedloopLM567usedincarriercommunicationapplications.Therearemanyapplicationsforit,butthethreecircuitsdescribedbelowhaveallbeentestedbypracticeforreferencebythosewholovecarriercommunication.ClassicCircuitDiagram(1)ClassicCircuitDiagram(2)ClassicCircuitDiagram(3)ECCNUNSPSCDescriptionValueECCNCodeEAR99HTSCode8542.39.00.01ProductManufacturerTexasInstrumentsInc.(TI)isanAmericantechnologycompanythatdesignsandmanufacturessemiconductorsandvariousintegratedcircuits,whichitsellstoelectronicsdesignersandmanufacturersglobally.ItsheadquartersareinDallas,Texas,UnitedStates.TIisoneofthetoptensemiconductorcompaniesworldwide,basedonsalesvolume.TexasInstrumentssfocusisondevelopinganalogchipsandembeddedprocessors,whichaccountsformorethan80%oftheirrevenue.TIalsoproducesTIdigitallightprocessing(DLP)technologyandeducationtechnologyproductsincludingcalculators,microcontrollersandmulti-coreprocessors.Todate,TIhasmorethan43,000patentsworldwide.ProductRangeDevicesBoardsDeveloperToolsARMPROCESSORSAUTOMOTIVEPRODUCTSIDENTIFICATIONSECURITYKinetisCortex-MMicrocontrollersIn-VehicleNetworkNFCLPCCortex-MMicrocontrollersMicrocontrollersandProcessorsRFIDAfterreadingtheblog,haveyoubetterunderstandLM567?IfyouarealsointerestedinhowtouseLM567totestthespeedofyourmotorcycle,youmaywishtobrowserighthererightnow!Finally,ifyouhaveanyquestionsaboutLM567,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!IIntroductionLM567isatonedecodingphase-lockedloopintegratedcircuit.Itiscompactindesign,simpleincircuit,andhasawiderangeofapplications.However,ifusingimproperly,itwillbringtroublesindebugging.ThisblogintroducestheworkingprincipleandtipsabouthowtouseLM567tonedecoderforreadersreference.Figure1.LM567ToneDecoderCatalogIIntroductionIILM567InternalStructurePinFunctionIIILM567WorkingPrincipleApplicationIVTipsofUsingToneDecoderLM567Ordering&QuantityIILM567InternalStructurePinFunctionThenameofLM567isphase-lockedlooptonedecoder,itspackageformuses8-pindualin-line,itsinternalstructureandpinfunctionsareillustratedinFigure2.Itsinternalcircuitstructureiscomposedofquadraturephase,detector,phase-lockedloop,amplifier,etc.TheoperatingvoltagerangeofLM567is4.75-9V,theoperatingfrequencycanreach500KHz,andthestaticoperatingcurrentisonly8mA.Thepin③isthesignalinputterminal,whichrequirestheinputsignaltobegreaterthan25mV.Thepin⑧isthelogicoutputterminal.Itcanbeseenfromthefigurethatitisanopencollectortransistoroutput,whichallowsamaximumsinkcurrentof100mA.Theexternalresistanceandcapacitanceofpins⑤and⑥determinethecenterfrequencyf01/1.1RCofICinternalvoltagecontrolledoscillator.Pins①and②areusuallyconnectedtothegroundseparatelytoformanoutputfilternetworkandalooplow-passfilternetwork.Thecapacitorconnectedtopin②determinesthecapturebandwidth.Thelargerthevalueofthecapacitor,thenarrowertheloopbandwidthis.Figure2.TopViewofLM567IIILM567WorkingPrincipleApplicationWhenthetonedecoderLM567works,itsphase-lockedloopinternalcurrent-controlledoscillatorgeneratesanoscillationsignalofacertainfrequencyandphase.Thissignalissenttothequadraturephasedetectortogetherwiththesignalinputatpin③forcomparison.Whenthefrequencyofthesignalfallswithinagivenpassband,thephase-lockedlooplocksthissignal,andatthesametimetheinternaltransistoroftheLM567iscontrolledtobepoweredup,andtheoutputterminaloftheLM567outputslowlevel.The⑤pinofLM567outputstherectangularsignaloftheinternaloscillator,andthe⑥pinoutputsthesawtoothpulse.Thefrequencyofbothisthesameasthecenterfrequencyoftheinternaloscillator.The②pinistheoutputofthephase-lockedloopphasedetector.ThevoltageonisthesignalafterF/Vconversion.Ifthetonesignalisinputtothe②pin,thenthe⑤pinoutputstheFMsquarewavesignalmodulatedbythe②pininputsignal.FromthebasicfunctionofLM567,LM567canbeusedasanoscillator,modulatorordemodulator.Therefore,itcanbeusedasabasicdeviceinthecircuit.TheapplicationofLM567hasthefunctionofdecodingaspecificfrequencyintheinputsignal,anditiswidelyusedincommunication,remotecontrol,measurement,frequencymonitoring,etc.Figure3.LM567ToneDecoderIVTipsofUsingToneDecoderLM567AlthoughLM567hasaverywiderangeofapplications,ifitisnothandledproperlyduringdesignandapplication,itstillfailstoachievetheexpectedresults,andevenbringstroubletothedebuggingoraffectsthereliabilityoftheproduct.Therefore,itshouldbeconsideredfromthefollowingaspectswhenusingit:1.SetOperatingFrequencyandBandwidthofLM567AccuratelyandAppropriatelyWeknowthattheinternaloscillationfrequencyf0ofLM567canbepre-setwithintherangeof0.1KHzto500KHz,anditscorrespondingbandwidthcanalsobedeterminedasrequiredwithinthefieldrangeof7%f0to14%f0.Therefore,afterthedetectedsignalisdetermined,theinternaloscillationfrequencyf0ofLM567shouldbesettocoincidewiththecenterfrequencyofthemeasuredsignal,andthetimingcomponentsRandCconnectedwiththe5and6feetofLM567shouldbeusedwithhighprecision.Amongthem,thesettingofthecenterfrequencycanbedeterminedbytheresistancevalueofthetunerR.Whenadjusting,itisnecessarytopreventRshortcircuitoropencircuit,otherwisetheoutputlevelof⑧pinwillbelowlevelwhetherthereisinputsignalornot.Theexternalcapacitanceofthe②pinofLM567determinesthecapturebandwidth.Thesmallerthecapacity,thewiderthecapturebandwidth.However,thecapacitancecannotbereducedblindlytoincreasethebandwidth,soasnottoreducetheanti-interferenceabilityoreventriggerfalsely,whichaffectsthereliabilityoftheproduct.2.MaketheCenterFrequencyofthePassbandCoincidewiththeCenterFrequencyoftheOscillationAsMuchAsPossibleItshouldbenotedthatthecenterfrequencyofthepassbanddoesnotalwayscoincidewiththecenterfrequencyoftheoscillator,andsometimesitwilldeviateseverely.Thiswillinevitablycauseadecreaseinreliabilityandsensitivity.Therefore,measuresshouldbetakentomakethetwocenterscoincideasmuchaspossible.ThecircuitshowninFigure4canminimizethefrequencyoffsetofthetwocenters.Figure4.CircuitofLM5673.WorkingVoltageofLM567ShouldBeStableThestabilityoftheoperatingvoltageoftheLM567hasafixedresponsetothestabilityofthecenterfrequencyofthetonedecoder.4.AvoidMisoperationWhentheOutputTerminalisPoweredOnLM567outputsalowlevelatthemomentwhenthepoweristurnedon.Therefore,forsomeremotecontrolcircuits,itisnecessarytoaddaCRintegrationdelaycircuittotheoutputendtoavoiderroneousoperationwhenthepoweristurnedon.Thisisespeciallyimportantintheon-offcontrolcircuit.Afterreadingtheblog,haveyoubetterunderstandLM567?Finally,ifyouhaveanyquestionsaboutLM567,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!IIntroductionWhentestingenvironmentalprotection,safety,andeconomicindicatorssuchasnoise,accelerationperformance,maximumspeed,andfuelconsumptionofmotorvehicles,itisnecessarytomeasureandcontrolthevehiclespeed.Mostexistingvehiclespeedmeasurementmethodsuseelectronictimingdevicesorstopwatchestomeasurevehicles.Thetimeittakestotravelafixeddistanceandthenfindtheaveragespeed.Generally,theprocessorandthedisplaypartoftheelectronictimingdevicearebasicallythesame,butthespeedsensorpartisdifferent,andthecharacteristicsofthesensordirectlyaffecttheaccuracyofthemeasurementresult.Atpresent,thecommonlyusedspeedsensorsincludepressuresensitivesensors,COMScamerasandparallellightsources.Theformerhasasimplestructure,butitiscumbersometolay,thesensoriseasilydamaged,andthesensitivityisreducedafterlong-termuse,whichaffectsthemeasurementresults.Thelatterhashighsensitivityandaccuratemeasurement.However,thecostistoohigh,involvesmoreequipment,andhashigherrequirementsfortheplacementofthelightsource.Consideringtheaboveproblems,itisafeasiblemethodtodesignanewinfraredspeedsensorusingLM567.Thesensorissmallinsize,lowincost,simpleinoperation,easytouse,hashighsensitivity,accuracy,stabilityandanti-interferenceability,andissuitableformeasuringtheaveragespeedofavehiclewithinafixeddrivingdistance.Figure1.LM567CatalogIIntroductionIIWorkingPrincipleofTraditionalSpeedMeasuringDevice2.1UsingPressureBeltRoadTester2.2UsingLaserRoadTesterIIIWorkingPrincipleofInfraredSpeedSensorBasedonLM5673.1InternalStructureandFunctionofLM5673.2PrincipleofInfraredSpeedMeasurementBasedonLM567IVConclusionOrdering&QuantityIIWorkingPrincipleofTraditionalSpeedMeasuringDeviceThefollowingusesthemeasurementofmotorcycleaccelerationnoiseasanexample,tointroducetheprinciplesandadvantagesdisadvantagesoftheconventionalspeedmeasuringdevicescurrentlycommonlyused.Figure1isasimplifiedlayoutofmotorcycleaccelerationnoisetest.2.1UsingPressureBeltRoadTesterForthespeedmeasurementmethodusingthepressurebeltroadtester,placethepressurebeltatAA,BB,CC,DDrespectivelyandstickthepressurebelttotheroadsurfacewell.ThedistancebetweenAAandBB,CCandDD(thatis,thespeedmeasurementzone)is1meter,andthepressurebeltandtheroadtesterareconnectedinsequencewithacable.WhenthevehiclepassesthepressurebeltatAA,thepressure-sensitivesensorinthepressurebeltistriggered,andthetriggersignalissenttotheroadtestertostartthetimingofitsinternaltimingdevice;WhenthevehiclepassesBB,atriggersignalisgeneratedagaintostopthetimingdevice.Usingtheinternalprocessoroftheroadtester,thetimetakentopassthedistancebetweenAAandBBisconvertedintovehiclespeedanddisplayedontheLCDscreen.Figure2.LayoutDiagramUsingPressureBeltRoadTesterSimilarly,avehiclespeedvaluecanbemeasuredbetweenCCandDDtomeettherequirementsofnoisemeasurement.Theworkingprincipleofthisspeedmeasurementmethodissimple,buttheequipmentismoretroublesometolay,andthesensoriseasilydamaged.Afterlong-termuse,thesensitivitywillbereduced,whichwillaffectthemeasurementresult.2.2UsingLaserRoadTesterForthespeedmeasurementmethodusingthelaserroadtester,fourparallellaserlightsourcesareplacedatfourpositionsofA,B,C,andD,andfourareplacedatfourpositionsofABCD.CMOScameraforreceivinglasersignals.Thelightsourcecanbeadjustedsothatthelaserlightemittedisalignedwiththecenterofthecamera,andthecameraisconnectedtotheroadtesterinsequence.WhenthevehiclepassesAA,thelightisblocked,andthecamerageneratesatriggersignaltomaketheinternaltimingdeviceoftheroadtesterwork;WhenthevehiclepassesBB,atriggersignalisgeneratedagaintostopthetimingdevice,andtheinternalprocessoroftheroadtesterisusedtoconvertthetimespentthroughthedistancebetweenAAandBBtothevehiclespeedanddisplayitontheLCDscreen.on.Figure3.LayoutDiagramUsingLaserRoadTesterSimilarly,aspeedvaluecanbemeasuredbetweenCCandDD.Thesensitivityandmeasurementaccuracyofthisspeedmeasurementmethodareveryhigh,buttheoperationisextremelyinconvenient.Notonlydoeseachlaserlightsourcerequireanindependentpowersupply,butalsothelasersignalmustbedirectedtothecenterreceivingpointofthecamera,whichplaceshighrequirementsontheplacementofthelightsource,otherwisethesensorwillbedifficulttoworkproperly.IIIWorkingPrincipleofInfraredSpeedSensorBasedonLM567Thisblogusesaphase-lockedloopaudiodecodingchipLM567todesignanewinfraredspeedsensor.Itscircuitdiagramandworkingprincipleareasfollows.3.1InternalStructureandFunctionofLM567LM567isspeciallyusedtodemodulateasingletonefrequencymodulationsignal,anditsoperatingfrequencycanbeashighas500kHz.Itiswidelyusedinindustrialautomaticcontrol,remotecontroltelemetry,securityalarmandotherfields.LM567ismainlycomposedofquadraturephasedetector,phase-lockedloopandamplifier.ItsinternalstructureisshowninFigure2.Pins5and6ofLM567areexternallyconnectedwithtimingresistorsandcapacitorsR,C.RandCdeterminethecenterfrequencyf0ofthephase-lockedloopinternalvoltagecontrolledoscillator,thatis,f0.ResistorRisconnectedbetweenpins5and6,ofwhichpin6isgroundedthroughcapacitorC(Uss).IfRis2~20k,theLM567canextractthetonesignalintherangeof0.01~500kHz.Pins1and2ofLM567arerespectivelyconnectedtothegroundwithacapacitortoformanoutputfilternetworkandaphase-lockedlooplow-passfilternetwork.ThecapacityoftheexternalcapacitorC2onpin2determinesthecapturebandwidthofthephase-lockedloop,anditssizeisBw1070.Uinistheeffectivevalueofthesinewavesignalvoltageinputfrompin3,andrequiresUin25mV,generallybetween100~200mV.TheexternalcapacitorC1ofpin1istheoutputfiltercapacitorofthequadraturephasedetector,anditscapacityismorethantwicethecapacityofthecapacitorC2connectedtopin2,whichshouldsatisfyC12C2.Figure4.TopViewofLM567(1)UsingLM567asFrequencyModulatorPin2isconnectedtotheinputofthelow-passfilterofthephase-lockedloop.Themodulatedsignaladdedfrompin2isfilteredbyalow-passfiltertoremoveout-of-bandnoiseandnoise,andthenaddedtothecenterfrequencyf0ofthevoltage-controlledoscillatorforfrequencymodulation,andthenthepin5outputstheFMsignal.Thecenterfrequencyf0oftheFMsignalisdeterminedbytheparametersoftheRCresistor-capacitornetworkconnectedtopins5and6.WhenLM567isusedasthefrequencymodulationcircuit,onlyitsinternalphase-lockedlooplow-passfilterandvoltage-controlledoscillatorareused.ChangingtheparametervalueoftheRCnetworkcanrealizemodulationtodifferentfrequencies.(2)UsingLM567asFrequencyDemodulatorThemodulatedsignalisinputfrompin3.Whenthecenterfrequencyoftheinputsignalisequaltothecenterfrequencyf0ofthevoltage-controlledoscillatorintheLM567,thelow-passfilter(pin2)oftheloopoutputsthedemodulatedsignal.3.2PrincipleofInfraredSpeedMeasurementBasedonLM567ThecircuitdiagramoftheinfraredspeedsensorbasedonLM567isshowninFigure3.TheinternaloscillatoroftheLM567providesasquarewavesignaltodrivefourLEDstoemitinfraredlight,anditsfrequencyisdeterminedbyR2andC4.Figure5.CircuitDiagramofInfraredSpeedSensorPlacethefoursensorsinthefourpositionsA,B,C,andDinFigure1.Whenthevehiclepassesthesensor,theinfraredraysemittedbytheLEDarereflectedbythevehiclebody.ThephotosensitivetubeQ1receivesthereflectedlight,isamplifiedbythetransistorandconvertedintoavoltagesignal,andissenttotheinternalphasedetectoroftheLM567forsynchronousdemodulation,andthenconvertedintoadigitalsignalbythecomparatorinsidetheLM567andoutputfrompin8.Theoutputsignalistransmittedtotheroadtester,whichtriggersthetimingdeviceintheroadtestertostarttiming.Similarly,whenthevehiclepassesthesensoratpointB,atriggersignalisgeneratedtostopthetimingdeviceandpasstheroadtester.TheinternalprocessoroperatestoobtainthespeedofthevehicleasitpassesAAandBB.LM567isaphase-lockedloopaudiodecodingcircuit.Inthecircuit,itisusedforfrequencyselection,thatis,thecircuitoutputslowlevelonlywhenthefrequencyofthe3-pininputsignalisconsistentwiththefrequencyoftheLM567internaloscillator,otherwisetheoutputishigh.Level.Inotherwords,onlywhenthereflectedinfraredlightreceivedbyQ1comesfromtheLEDinitsowncircuit,theLM567willoutputatriggersignalfromhightolowtotheroadtester.Thebiggestfeatureofthiscircuitistorealizetheautomaticsynchronizationoftheinfraredemissionfrequencyandtheworkingfrequencyofthereceivingcircuit;Thatis,thereisnospecialpulsegeneratingcircuitintheinfraredtransmittingpart,andthepulseisdirectlyintroducedfromthedetectioncircuitofthereceivingpart(LM567phase-lockedcenterfrequencysignal).Inthisway,thewiringanddebuggingworkissimplified,avoidinginconsistenttransmissionandreceptionfrequenciescausedbychangesinthesurroundingenvironmentandcomponentparameters,eliminatingmutualinterferencebetweenadjacentsensors,andgreatlyenhancingcircuitstabilityandanti-interferencecapabilities.IVConclusionTheinfraredspeedsensordesignedbasedontheLM567modulationanddemodulationfunctionrealizestheautomaticsynchronizationoftheinfraredtransmissionfrequencyandtheworkingfrequencyofthereceivingcircuit.Inaddition,ithasthecharacteristicsofstronganti-interferenceabilityandstability,lowcostandsimplestructure.Therefore,itcanbewidelyusedtomeasuretheaveragespeedofvehiclessuchasautomobilesandmotorcycles.Figure6.LM567Afterreadingtheblog,haveyoubetterunderstandLM567?Finally,ifyouhaveanyquestionsaboutLM567,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!

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TheLM2940isacommonlow-dropout(LDO)linearregulator.ThisisacomprehensiveintroductiontoLM2940voltageregulator,fromitspinout,feature,parametertoitsapplication,itsdifferencebetweenLM7805andmore.CatalogLM2940DescriptionLM2940PinoutLM2940FeaturesLM2940ParametersLM2940EquivalentLM2940VSLM7805LM2940TypicalApplicationLM2940PackageLM2940ApplicationComponentDatasheetLM2940DescriptionTheLM2940isacommonlow-dropout(LDO)linearregulator.Thedropoutvoltageofaregulatoristhevoltagerequiredbetweentheinputandtheregulatedoutputvoltage.Theregulatorwastesthisvoltage(multipliedbycurrent),sothelowerthedropoutonalinearregulator,themoreefficientitis.ThismeansthattheLM2940,witha5Vdropoutat1amp,canbeusedwitha6voltwallwarttoprovidearegulated5Voutput.Thisalsomeansthattheregulatorwilloperateatamuchlowertemperaturethanastandard7805,whichwouldrequireamuchhigherinputvoltage(around7.5volts)foraregulated5Voutput.LM2940PinoutLM2940voltageregulatorLM2940PinoutPinNo.PinNameDescription1VinA(+ve)voltageisgivenasinputtothispin.2GNDCommontobothInputandOutput.3VoutOutputregulated12VistakenatthispinoftheIC.LM2940FeaturesInputVoltageRange=6Vto26VDropoutVoltageTypically0.5VatIOUT=1AOutputCurrentinExcessof1AOutputVoltageTrimmedBeforeAssemblyReverseBatteryProtectionInternalShortCircuitCurrentLimitMirrorImageInsertionProtectionP+ProductEnhancementTestedLM2940ParametersOutputoptionsFixedOutputIout(Max)(A)1Vin(Max)(V)26Vin(Min)(V)6Vout(Max)(V)15Vout(Min)(V)5Fixedoutputoptions(V)5,8,9,10,12,15Noise(uVrms)150Iq(Typ)(mA)10ThermalresistanceJA(C/W)23Loadcapacitance(Min)(F)22RatingCatalogRegulatedoutputs(#)1Features-Accuracy(%)2PSRR@100KHz(dB)48Dropoutvoltage(Vdo)(Typ)(mV)500Operatingtemperaturerange(C)-40to125,-40to85LM2940EquivalentTheequivalentforLM2940isLM7805.LM2940VSLM7805TheLM7805isapopularlinearvoltageregulatorbecauseitrequiresnoadditionalcomponentstooperate.Itisaverylow-costcomponent.Becauseofitscharacteristics,itreducestheoutputvoltageattheexpenseofheatdissipation,makingitinefficient.TheLM7805requiresaminimuminputvoltageof7.3Vtofunctionproperly.Itcanhandleamaximumcurrentof1A.Somemodelscanhandleupto1.5A.Itisrecommended,andinsomecasesrequired,tousecapacitorstoreduceoreliminatetheeffectsofthefrequenciesintroducedbytheotherelementsofthecircuit.Theyalsohelptoreducetheimpactofpeakconsumption.WhiletheLM2940isfromadifferentgeneration,butitspinisstillcompatiblewiththeLM7805.ItisaLow-dropout(LDO)LinearRegulatorthatismoreefficientthantheLM7805,butitwillrequirecapacitors.ThemaindifferencebetweenLM2940andLM7805isthatthemaximumoutputcurrentofLM2940is1A.ThemaximumoutputcurrentofLM7805is1.5A.Othersareveryclose,soifthecircuitonlyrequires1Aorbelow,LM2940canbeusedinsteadofLM7805.Whatsmore,the7805isexpendingtheexcesspowerasheat.Whichisverylossyespecialyifyourprojectusesbatteries.Theotherchipisabuckconverterissoitapproaches90%efficiencybyswitchingsothereisnowasteheat,thatswhyeventhoughLM7805ischeaperandeasiertousebuttheresstillalotofpeoplewouldgoforLM2940.LM2940LM7805SchematicComparisonLM2940SchematicLM7805SchematicLM2940TypicalApplicationLM2940PackageLM2940ApplicationPostregulatorforswitchingsuppliesLogicpowerSuppliesIndustrialInstrumentationComponentDatasheetLM2940DatasheetS8050isalow-powerNPNsilicontubewithamaximumcollector-base(Vcbo)voltageof40Vandacollectorcurrent(Ic)of0.5A.S8050isoneofthemostcommonlyusedsemiconductortransistormodelsincircuithardwaredesign.Name:S8050Type:NPNDissipatedpower:0.625W(SMD:0.3W)Collectorcurrent:0.5ABasevoltage:40VCatalogS8050PinoutS8050CircuitS8050ApplicationS8050FeaturesS8050AdvantageS8050AlternativesS8050EquivalentsWhereHowtouseS8050HowtoSafelyLongRunS8050inCircuitS8050PinoutPinNumberPinNameSymbolDescription1EmitterECurrentDrainsoutthroughemitter2BaseBControlsthebiasingoftransistor3CollectorCCurrentflowsinthroughcollectorS8050ApplicationAudioamplificationcircuitsClassBamplifiersPushpulltransistorsCircuitswherehighgainisrequiredLowsignalapplicationsS8050FeaturesLowVoltage,HighCurrentNPNTransistorSmallSignalTransistorMaximumPower:2WattsMaximumDCCurrentGain(hFE)is400ContinuousCollectorcurrent(IC)is700mABase-EmitterVoltage(VBE)is5VCollector-EmitterVoltage(VCE)is20VCollector-BaseVoltage(VCB)is30VHighUsedinpush-pullconfigurationdoeClassBamplifiersAvailableinTo-92PackageNote:CompleteTechnicalDetailscanbefoundattheS8050datasheetgivenattheendofthispage.S8050AdvantageS8050npntransistorS8050isaNPNtransistorhencethecollectorandemitterwillbeleftopen(Reversebiased)whenthebasepinisheldatgroundandwillbeclosed(Forwardbiased)whenasignalisprovidedtobasepin.Ithasamaximumgainvalueof400;thisvaluedeterminestheamplificationcapacityofthetransistornormallyS8050.Sinceitisveryhighitisnormallyusedforamplificationpurposes.However,atanormaloperatingcollectorcurrentthetypicalvalueofgainwillbe110.ThemaximumamountofcurrentthatcouldflowthroughtheCollectorpinis700mA,hencewecannotdriveloadsthatconsumemorethan700mAusingthistransistor.Tobiasatransistorwehavetosupplycurrenttobasepin,thiscurrent(IB)shouldbelimitedto5mA.Whenthistransistorisfullybiasedthenitcanallowamaximumof700mAtoflowacrossthecollectorandemitter.ThisstageiscalledSaturationRegionandthetypicalvoltageallowedacrosstheCollector-Emitter(VCE)orCollector-Base(VCB)couldbe20Vand30Vrespectively.Whenbasecurrentisremovedthetransistorbecomesfullyoff,thisstageiscalledastheCut-offRegion.S8050Alternatives2N3904,2N3906,2N2369,2N3055,S9014,MPSA42,SS8050,BC547S8050Equivalents2N5830,S9013S8050CircuitThisisavideointroducingtransistorsstereoamplifierS8050andS8550.WhereHowtouseS8050S8050transistorisageneral-purposetransistor,itisaperfecttransistortoperformsmallandgeneraltasksinelectroniccircuits.Youcanuseitasaswitchinelectroniccircuitstoswitchonloadsunder700mA.700mAisenoughtohandlevarietyofloadsforexamplerelays,LEDs,bulbsetc.Itcanalsobeusedasamplifierinsmallamplificationstagesorasaseparatesmallsignalamplifier.HowtoSafelyLongRunS8050inCircuitTosafelyrunS8050transistorinyourcircuitorelectronicprojectsdonotoperatethistransistorfromvoltagehigherthan20Vanddonotoperateanyloadmorethan700mAor0.7A.Useasuitablebaseresistorwhichwilllimitsthebasecurrenttoitsrequiredlevel.Donotexposeittoheatover150centigradeandbelow-60Centigrade.

74LS05

LM3914isamonolithicicthatsensesanalogvoltagelevelsanddrives10LEDs,providingalinearanalogdisplay.Asinglepinchangesthedisplayfromamovingdottoabargraph.ThisisanoverviewofLM3914dot/bardisplaydriver,wewillprovidetheinformationofitspinout,datasheet,parameter,andwherehowtousethisdeviceandsomuchmore.Top5electronicsProjectsusingLM3914-15IC|lm3914lm3915circuitsCatalogLM3914DescriptionLM3914PinoutLM3914FeaturesLM3914ParameterLM3914EquivalentWheretouseLM3914ICHowtouseLM3914ICLM3914CircuitLM3914PackageLM3914ApplicationComponentDatasheetLM3914DescriptionTheLM3914isamonolithicintegratedcircuitthatsensesanalogvoltagelevelsanddrives10LEDs,providingalinearanalogdisplay.Asinglepinchangesthedisplayfromamovingdottoabargraph.CurrentdrivetotheLEDsisregulatedandprogrammable,eliminatingtheneedforresistors.Thisfeatureisonethatallowsoperationofthewholesystemfromlessthan3V.TheLM3914isveryeasytoapplyasananalogmetercircuit.A1.2Vfull-scalemeterrequiresonly1resistorandasingle3Vto15Vsupplyinadditiontothe10displayLEDs.Ifthe1resistorisapot,itbecomestheLEDbrightnesscontrol.Thesimplifiedblockdiagramillustratesthisextremelysimpleexternalcircuitry.Wheninthedotmode,thereisasmallamountofoverlaporfade(about1mV)betweensegments.ThisassuresthatatnotimewillallLEDsbeOFF,andthusanyambiguousdisplayisavoided.Variousnoveldisplaysarepossible.TheLM3914isratedforoperationfrom0Cto+70C.TheLM3914N-1isavailableinan18-leadPDIP(NFK)package.LM3914PinoutLM3914LM3914PinoutPinNumberPinNameDescription1and10to18LED1,LED2,LED3.....LED10The10LEDswhichhastobecontrolledisconnectedtothesepins2V-/GroundGroundpinoftheIC3V+/VccSupplyVoltage(3-18)V4RLOLowlevelvoltageforpotentialdivider5SignalAnalogsignalInputpinbasedonwhichtheLEDiscontrolled.6RHIHighLevelvoltageforpotentialdivider7REFOUTOutputReferenceVoltageforLEDcurrentlimiting8REFADJAdjustpinforvoltagereference9ModeSelectbetweenDot/BarModeLM3914FeaturesAnalogControlledLEDDriverICNumberofcontrollableLEDs:10OperatingVoltage:3Vto18VInputAnalogvoltagerange:1.2Vto12VLEDsinkcurrent:2mAto30mA(programmable)BothDot/BarmodeavailableCanbecascadedtocontrolupto100LEDsAvailablein18-pinDIP,PLCCpackageItcandriveLCDs,LEDsotherwisevacuumfluorescents.Thedototherwisebotdisplaymodecanbeselectedbytheuserexternally.Itcanbeexpandableupto100displays.LM3914ParameterManufacturer:TexasInstrumentsSeries:-Packaging:TubePartStatus:ObsoleteDisplayType:LEDLCDVacuumFluorescent(VF)Configuration:Dot/BarDisplayInterface:-DigitsorCharacters:10StepsCurrent-Supply:6.1mAVoltage-Supply:3V~20VOperatingTemperature:0C~70CMountingType:ThroughHolePackage/Case:18-DIP(0.3007.62mm)SupplierDevicePackage:18-PDIPBasePartNumber:LM3914LM3914EquivalentLM3914EquivalentLEDDriver:LM3916AlternativeLEDDriverICs:CD4511,MAX7219,CD4054WheretouseLM3914ICTheLM3914isananalogcontrolledLEDdriverIC,whichmeansthatitcancontrol(turnonoroff)10LEDlightsusingananaloginputvoltage.Thisintegratedcircuiteliminatestheneedforamicrocontrollerandprogramming,aswellasthehardwarerequiredtocontroltenLEDs.Theanaloginputvoltagecanrangefrom3Vto18V,andtheLEDcurrentcanbecontrolledwithasingleresistoronpin7.(RefOut).TheICalsohastwooperatingmodes:DOTmodeandBARmode,andupto100LEDscanbecontrolledbycascadingmultipleICs.TheseICsarecommonlyusedinvisualalarmsandothermetering/monitoringapplicationsbecausetheLEDscanbecontrolledwithoutflickeringandflawlesslywithequalbrightness.So,ifyourelookingforanICtopoweryourbarLEDlightsoranother10-LEDsequence,thisICmightbeofinteresttoyou.HowtouseLM3914ICThebenefitofusingLM3914isthatitrequireslittlehardwareandissimpletosetup.Simplyconnectthe10LEDstotheIC,setthereferencevoltagesfortheinputvoltage,andlimitthecurrentthroughtheLED,andweredone.ThecircuitbelowisanexampleofanLM3914applicationcircuit.SimplyconnecttheV+andV-topowertheIC,andtheanalogsignalvoltageisconnectedtopin5.Inthiscase,weused9VtopowertheICandmonitorananalogyvoltagerangingfrom0to5V.AlwayskeepinmindthatthevoltageusedtopowertheIC(inthiscase,9V)shouldbeatleast1.5Vhigherthanthemonitoringvoltage(here5V).Becausewearemonitoring0-5Vhere,wesetthelowreferencevoltage(pin4)to0Vandthehighreferencevoltage(pin6)to5V.Asyoumayhavenoticed,weconnectedalltenLEDsdirectlytotheICwithoutusinganycurrentlimitingresistors.ThisisbecausetheIChasaninternalcurrentlimiterandthecurrentvaluecanbesetusingthepinVRO(pin7).Thecurrentcalculationformulasaregivenbelow,whereIisthecurrentflowingthrougheachLEDandRListheresistorconnectedtopin7.I=12.5/RLIntheprecedingexample,weuseda470ohmresistorasRl,sothecurrentthrougheachLEDwillbearound25mA;youcanchangethevalueasneeded.Also,thecathodeoftheLEDisconnectedtotheIC,whiletheanodeisconnectedto+5V.ThisisduetothefactthattheICoutputpinscanonlysinkcurrentandnotsourceit.Theintegratedcircuit(IC)canoperateintwomodes:dotmodeandbarmode.Indotmode,themodepin(pin9)mustbeleftfloating;inthismode,basedontheinputvoltage,onlyoneLEDwillbeturnedon.InBarmode,connectthemodepin(pin9)toV+,andtheLEDwillturnonandoffsequentiallybasedontheinputvoltage.Boththemodesareshowninthegiffileabove.LM3914CircuitThecircuitdiagramforICLM3914isshownbelow.Thecircuitcanbeconstructedusingbothbasicelectricalandelectroniccomponents.TheICLM3914isacriticalcomponentofthiscircuit.AnalarmdrivingswitchforoverrangecanbeconnectedtoabartypeLMseriesLEDdrivingdisplaycircuitinthefollowingcircuit.Thiscircuitissuitableforbardisplays.LM3914BasedAlarmDriverCircuitThecircuithereemploysaPNPtransistor,denotedbyQ1.ThistransistorcanbeconnectedbetweentheLEDpositiveandnegativeterminals,andthebaseterminalofthetransistorisconnectedtotheICspin-10todrivetheLED10.Inseries,analarmunitisconnectedtothetransistorscollectorterminal.Normally,Q1transistor,LED10,andthealarmunitareallturnedoff;however,ifLED10isactivated,itpullsQ1transistorthroughresistorR2andthusactivatesthealarmunit,indicatingthattheconditionisoutofrange.Intheabovecircuit,analarmunitgeneratesanacousticalarmsoundusingapiezosirenunit,otherwiseagatedastableswitchunitthatcontinuouslyactivatestheLEDbrightnessbetweenhighandlowlevelsbeneaththeover-rangestate,oracombinationofboth.Ifdesired,theunitcanbeswitchedtoanyoftheLEDdisplays,andthealarmwillsoundifthatoranyotherhighLEDisenergized.LM3914PackageLM3914ApplicationBatteryMeterforRobotMonitoringof12VCarBatteryTesterCircuitforSoilMoistureMonitoringofLeadAcidBatteryChargerChargeMonitoringCircuitforAtmosphericKitchenExhaustFanforControllingTemperatureMeterCircuitforTemperatureDigitalgaugesElectronicdisplaysLow-costmonitordevicesCrudeBatterylevelindicatorsFadebarsComponentDatasheetLM3914Datasheet

IDescriptionThisblogusestheuniversalintegratedchipTL494toconvertanalogsignalsintoPWM(pulsewidthmodulation)signals.Intheoutputpart,N-channelMOSFETandP-channelMOSFETareusedtoformaswitchingpoweramplifier.CatalogIDescriptionIIIntroduction2.1SwitchingPowerAmplifierOverview2.2TL494IntroductionIIISchemeDesign3.1DutyCycleAdjustmentCircuit3.2InputSignalCompressionCircuit3.3MOSFETDriveCircuit3.4WorkingPrincipleofOutputPartIVExperimentalResultsVConclusionFAQOrdering&QuantityIIIntroduction2.1SwitchingPowerAmplifierOverviewWiththerapiddevelopmentofhigh-speedpowerMOSFETproductiontechnology,theoperatingfrequencyofMOSFETisgettinghigherandhigher,thedrivingmethodisgettingsaferandthepriceisgettinglower.Therefore,alargenumberofswitchingpoweramplifiersappliedtovarioushouseholdappliancesandindustrialalarmshaveappearedonthemarketinrecentyears.Comparedwiththelinearpoweramplifier,althoughthecircuitoftheswitchingpoweramplifierisslightlymorecomplicated.Butitisveryefficientandcanreducethesizeoftheheatsink,evenwithoutusingtheheatsink.Therefore,thevolumeoftheproductcanbegreatlyreduced.2.2TL494IntroductionTL494isaswitchingpowersupplypulsewidthmodulation(PWM)controlchip.Formanyyears,asthecheapestdouble-endedPWMchip,TL494hasbeenwidelyusedindouble-endedtopologiessuchaspush-pullandhalf-bridge.Becauseofitsloweroperatingfrequencyandsingle-endedoutputportcharacteristics.Itisoftenusedwithpowerbipolartransistors(BJT).IfusedwithpowerMOSFET,anexternalcircuitisrequired.TL494worksinawidevoltagerangefrom7Vto40V,withamaximumoperatingfrequencyof200kHz,withtheinternalsawtoothgenerator,PWMgenerator,andlagtimeadjustmentfunctions.IIISchemeDesignFigure1isablockdiagramofaTL494-basedswitchingpoweramplifier.Thekeytothecircuitdesignisthedutycycleadjustmentcircuit,inputsignalcompressioncircuit,andMOSFETdrivecircuit.Figure1.TL494SwitchingPowerAmplifier3.1DutyCycleAdjustmentCircuitThedutycycleisthekeytoimprovingvoltageutilizationduringPWMsignalmodulation.BecauseTL494isanintegratedchipforswitchingpowersupply.Therefore,theminimumlagtimeissetto0.1Vinternally.Themaximumdutycycleisapproximately96%attheoutputofthetransmitterstage.Figure2showstheinputpartandpartofthecircuitforPWMsignalmodulation.Figure2.SignalInputsectionandPWMGeneratorInFigure2,whenC4=1000pFandR4=24k,theoperatingfrequencyisabout78kHz.IfthereisnodutycycleadjustmentcircuitD8,D17,R23,becausethecomparisonpointoftheinternaldelaytimecomparatoris0.1V.Sotheminimumon-timeisabout1.52s,andtheminimumdutycycleisD=1.52/1312%.Therefore,thevoltageutilizationratewilldecreaseduringPWM.IfD8,D17,andR23areused,a0.82VbiasvoltagewillbegeneratedatthepointEofthecapacitorC4forthesawtoothwavegeneration,andthestartingpointofthesawtoothwavewillbeincreasedfrom0Vto0.82V.Therefore,theon-timeisreducedto0.64s,andtheminimumdutycycleisreducedtoD=0.64/134.9%.Thiscansignificantlyimprovethevoltageutilization.Figure3istheoutputwaveformwhenthereisnodutycycleadjustmentcircuit.Figure4istheoutputwaveformwhenthereisadutycycleadjustmentcircuit.Figure3.OutputWaveformwithoutDutyCycleAdjustmentCircuitFigure4.OutputWaveformwithDutyCycleAdjustmentCircuit3.2InputSignalCompressionCircuitBecausetheinputsignalofthealarmhasalargevariationrange,itisnecessarytocompressthesignalwithalargeamplitudeaccordingtoacertainratio.InFigure2,R6,R16,D10,D11constitutetheinputsignalcompressioncircuit,anditskeyistousetheinputcharacteristicsofthediode.Figure5showsitsinputcharacteristics.Amongthem,D10andD11areconnectedinparalleltocompresssignalsinbothpositiveandnegativedirections.Figure5.OutputCharacteristicsofInputSignalCompressionCircuitThecompressionratiodependsonthevaluesofR6andR16.Thelargerthevalue,thelargerthecompressionratio.ByadjustingthevaluesofR6andR16,thechangerangeofthecompressedsignalissetto-0.82V~0.82V.Theamountofchangeis1.64V.WecanseeFigure4,thesawtoothvoltagevariationrangeis0.82V~3.25V.SotheoutputsignalvariationrangeoftheTL494internalerroramplifieris2.43V.ThegainoftheinternalerroramplifierdependsonR7andR20.Byadjustingtheirvalues,whentheamountofchangeofthecompressedsignalis1.64V,theoutputsignalchangerangeoftheinternalerroramplifiercanbesetto2.43V.Sincemostalarmsusetweeters,thebasswithalargeamplitudecanbegreatlyreduced.3.3MOSFETDriveCircuitP-channelMOSFETusesIRF9540.Ithasthecharacteristicsofthemaximumoperatingvoltageof100V,themaximumoperatingcurrentof18A,andsaturationwhenVGSvoltageis5V~15V.N-channelMOSFETusesIRF540.Ithasthecharacteristicsofthemaximumoperatingvoltageof100V,themaximumoperatingcurrentof27A,andsaturationwhenVGSvoltageis5V~15V.ThedrivingtransistorQ3adoptsNPNtypeC8050,andQ7adoptsPNPtypeC8550.Bothofthesetwodrivetransistorshavethecharacteristicsofamaximumoperatingvoltageof30V,amaximumoperatingcurrentof1A,andaVBEof12V.Figure6showstheMOSFETdrivecircuit.Figure6.MOSFETDriveCircuitFigure7showstheMOSFETdrivingprinciplewaveform.WhenthepulsevoltageatpointAislow,thecurrentflowsthroughthereversebiasoftheZenerdiodeD7andthetransistorQ3toformaVGSvoltage,andQHisturnedon.WhenthepulsevoltageatpointAishigh,thecurrentflowsthroughthereversebiasoftheZenerdiodeD9andthetransistorQ7toformaVGSvoltage,andQListurnedon.Inaddition,Figure7alsoshowsdetaileddrivingwaveforms.lWhenthepulsevoltageislow,thevoltageislowerthanVLtomakeQHturnon.lWhenthepulsevoltageishigh,itsvoltageishigherthanVHtomakeQLturnon.IttakesacertainamountoftimetochangefromVLtoVH.Atthistime,QHandQLwillbecutoffatthesametime.Therefore,thepulsechangeprocessisverysafe.Figure7.MOSFETDrivingPrincipleWaveformTheVGSofQHandQLisdeterminedbythefollowingformula:Where:VGSisthedrivingvoltageofMOSFET;VCisthepowersupplyvoltage;VDistheregulatedvoltageofZenertubesD7andD9(usuallythesameZenertubeisused);VBEisthecounterbreakdownvoltageofC8050andC8550.Figure8isthemeasureddrivewaveform.Whenthepulsevoltagechangesfromlowtohigh,thetimeforQHandQLtocutoffatthesametimeisabout100~300ns.Figure8.MeasuredDriveWaveform3.4WorkingPrincipleofOutputPartAsshowninFigure6,theoutputpartconsistsofQH,QLandL3,C8,C5,andC7.TheoutputvoltageistransmittedtotheloadafterfilteringhighfrequencywavesthroughL3andC8.Generally,anelectrolyticcapacitorisusedattheoutputend,butthiscircuitusesC5andC7toformahalfbridge,andthenconnectthemidpointtotheload.Theadvantageofthisconnectionmethodisthatthetwocapacitorsarenotonlythetransmissionpathoftheoutputsignal(thecapacitancevalueistheparallelvalueofthetwocapacitors),butalsohasafilteringeffectonthepowersupply(thecapacitancevalueistheseriesvalueofthetwocapacitorsatthistime),andreducetheinternalpressureofthecapacitorbyhalf.IVExperimentalResultsTable1showsthequiescentcurrentwhentheinputvoltageis35Vandtheoperatingfrequencyis78kHzwhenusingdifferentvoltageregulatordiodes.ItcanbeseenfromTable1:Whenthevoltageregulationvalueofthevoltagestabilizingdiodeis0V,5V,thedistancebetweentheconductionpointsofVLandVHistooclose,andtheconductiontimeistoolong,andthereisalargerstaticcurrent.Althoughthecurrentisrelativelysmallat20V,theMOSFETgeneratessevereheat.AscanbeseenfromTable1,whentheoperatingvoltageis35V,theselectionrangeoftheZenerdiodeis7.5V~15V.VConclusionTheexperimentalresultsshowthatthePWMsignalofTL494isusedforN-channelMOSFETandP-channelMOSFETtoformaswitchingpoweramplifierwithauniquedrivingmodetoovercometheshortcomingsofsimultaneousconductionoftwopowerMOSFETs.Notonlythat,italsohasidealdrivewaveforms,efficiencygreaterthan95%,goodbandwidthandlowprice,whichfullymeetstherequirementsofindustrialalarms.Andunder18Woutputpower,comparedwiththepoweramplifiercomposedofTDA7481,thereisnotmuchdifference,andthereisbasicallynoheatingphenomenon,andtheheatsinkcanberemoved.Ifyouwanttogetmoreoutputpower,youonlyneedtoincreasetheworkingvoltagetomorethan35VandfitaproperZenerdiode.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?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.I.74HC164Introduction74HC164adoptsDIP-14,SO-14,SSOP-14andTSSOP-14packagepinconfiguration.ItiscomplementarytoMOS8-bitserialinputandparalleloutputunidirectionalshiftregister,thelogicsymbolisshowninthefigure1.Thepowersupplyvoltageis2~6V.Inthefigure1,AandBaretheserialcodeinputterminals;CLRistheclearinputterminal;CLKistheclockpulseinputterminal.Withthearrivaloftherisingedgeoftheclockpulse,thestateofphaseA,phaseBandthesubsequentphaseshiftsfromQAtoQHinturn.CatalogI.74HC164IntroductionII.74HC164LogicSymbolIII.CircuitDesignIV.HowtoCheckandRepairtheCircuitFAQOrdering&QuantityII.74HC164LogicSymbolFigure174HC164LogicSymbolIII.CircuitDesignFigure2isaninstrumentcircuitcomposedofserialinputandparalleloutputdigitalintegratedcircuits.T2-T5,C5andresistancetogetherformaturnsignalflashingoscillationcircuit.WhentheDR(connectedtotheturnswitch)inJ8isdisconnected,thiscircuitwillnotworkandtheturnsignalwillnotflash;whenDRison,theoscillationcircuitstarttowork,theturnsignalstartstoflash.Figure2MetercircuitdiagramDRisathree-positionswitch,onepoleisconnectedtotheleftturnsignal,onepoleisconnectedtotherightturnsignal,onepoleissuspendedintheair,andtheotherendofthepolehitstheground.Theswitch-offcircuitiscomposedofTl,DLRllandR12.Aswitch-typeHallelementisinstalledinthefrontandrearbrakesoftheelectricbicycle.Whentheswitchisswitched,theHallelementoutputsalowpotential,thatis,theBRKterminalintheplugJ2isgrounded,Tlisturnedon,andthereisavoltageofnearly5VonthecollectorofTl.ThisvoltageissenttothecontrollerthroughtheBRKterminalinJ2,andthepowersupplycircuitofthemotoristurnedoff.Themotorstopsworkingandactsasabrake.Onthecontrary,whenthebrakeisnotpinched,theHallelementoutputsahighpotential,Tliscutoff,andthemotorrunsnormally.Because74HC164isan8-bitserialinputandparalleloutputshiftregister,itformsamovementmodeandbatterypowerdisplaycircuitwithlight-emittingdiodes.74HC164soutputpin13,pin11,andD5-D7formthesideofthesportsmodedisplaycircuit,andpins6and10andD8-D12formthebatterypowerdisplaycircuit.Thedisplaysignalfromthecontrollerissenttotheserialinputterminals1and2ofthe74HC164throughtheDATAterminalintheJ2,andthenshiftedbytheinternalcircuit,thedrivingsignalisoutputfromtherelevantoutputterminaltolightupthecorrespondinglight-emittingdiode,soastocompletethecontrolofthedisplaycircuit.IV.HowtoCheckandRepairtheCircuitThiscircuitisrelativelysimpleandeasytorepair.Themainbasisforrepairingistojudgethequalityof74HC164.First,checkwhetherthe+5Vvoltageisnormal,andthencheckwhetherthevoltageatpin③ofthe74HC164sclocksignalinputiscloseto+5V.Ifitislowerthan+5V,andafterdisconnectingR73,theCLKterminalvoltageofJ2isnormal,andthe74HC164isdamaged.IfthevoltageoftheCLKportisabnormal,thefaultisinthecontroller.Next,measurewhetherthevoltageoftheserialinputterminals①and②changesduringthetransitionofthemotionmode.Ifnot,thefaultisinthecontroller;ifthereis,the74HC164isdamaged.Fromtheactualrepairsituation,mostofthe74HC164failuresarecausedbydamagetotheinternalcircuitofthe⑩pin(powersupplyterminal).Inaddition,whenpurchasing74HC164,youcanfirstmeasuretheresistanceofthe⑩pin.Theresistancevalueshouldbeabout4kDinthepositivetestandinfiniteinthereversetest.FAQHowdoesthe74HC164transmitdatainthemicrocontrollercircuit?Onepinofthesingle-chipmicrocomputerislikeafaucet,andthedataissentonebyone,thatis,likethewaterfromthefaucet,drippingdropbydrop.The74H164islikeasmallbowlreceivingwater.Itisjustfullafterreceiving8dropsofwater.Atthistime,itissenttothedigitaltube.Thesingle-chipmicrocomputermustsendan8-bit(ormore)data,ifitissentatthesametime,itisaparalleltransmission,ifitisabitbybit,itisaserialtransmission.Thedataofthesingle-chipmicrocomputerissenttothe74HC164bitbybit,whichisserial,andthe74HC164sendsthedatatothedigitaltubeatonce,whichisparallel.So74HC164playsarolefromserialtransmissiontoparalleltransmission.Whatisthedifferencebetween74HC164Dand74HC164NMCU?TheDin74HC164Drepresentsachippackage.TheNin74HC164Nmeansdualin-lineplasticpackaging.Whatisthedifferencebetween74HC164and74LS164,cantheybeusedtogether?74ls164isaTTLcircuit,thepowersupplyvoltageis5V,thehigh-leveloutputcurrentIohis-0.4MA,andthelow-leveloutputcurrentis8MA.74HC164isaCMOScircuit,thepowersupplyvoltageis2V~6V,theoutputdrivecurrentcanreachplusorminus20MA.Ifthepowersupplyvoltageyouuseis5Vandtheoutputdrivecurrentissuitablefor74ls164,theycanbeusedtogether.Whatdevicescan74hc164bereplacedwith?74HC164isaCMOSdevicewithapowersupplyvoltageof2V-6V.Itcanbedirectlyreplacedby74HCT164,40H164.Ifthepowersupplyvoltageis5Vandtheoutputdrivecurrentissmall,itcanalsobereplacedby74164,74LS164,74F164,74ALS164.Whichof74LS164and74HC164hashigherdrivingcapability?74LS164isaTTLdevicewithahigh-leveldrivingcapabilityofabout0.4mAandalow-leveldrivingcapabilityofabout8mA.74HC164isaCMOSdevice,withhigh-levelandlow-leveldrivecapabilityupto20mA.TheabovedatacomesfromDATASHEET.Butgenerallyspeaking,thehigh-leveloutputcapabilityofmanyCMOSdevicesisweak,smallerthanTTL,andthelow-leveldrivecapabilityisstronger.Can74hc164nbeusedtodrivethedigitaltube?Ofcourse,youcanusethe164chiptodrivethenixietube,whichismostlyusedinsituationswheretheIOportresourcesaretightandthedisplaydatarefreshofthenixietubeisslow.Whendesigningthecircuit,multiple164chipsareusedincascade,nomatterhowmanydigitaltubesaredriven,only2IOportsofthesingle-chipmicrocomputerareoccupied.ItcanbesaidthatitisthemostIOport-savingdrivingmethod,anditisstilldrivenstatically,withoutstrobeandbrightnessLowphenomenon.Thedisadvantageisthatmultiple164sareusedincascadeconnection,whichwillcausethesingle-chipmicrocomputertosendalargeamountofdisplaydata(1bytepernixietube)atonetimewhenrefreshingthedisplaydata.Duringthisprocess,thenixietubewillbeallon,althoughthedataissentTheprocessdurationisveryshort,butitstillaffectsthedisplayeffect.Itisrecommendedtoturnoffthedigitaltubewhenrefreshingthedata.

I.DescriptionAutomaticgaintechnology(AGC)iswidelyusedinthefieldofindustrialautomationclosed-loopcontrol.Inindustrialcontrol,time-varyinggainamplifiersareoftenneededtomeetproductionneeds,ormadeithasacertainregularitytoensurethestabilityofthecontroloutputamplitude,therebyreducingtheinterferenceoftheinputinterferencenoisesignal.Forthesystemtoadjustquikly,thispaperdesignsanAGCcontrollerbasedonthecombinationofAGCchipAD603andswitchingpowersupplychipMC34063,cleverlyusingMC34063sstablereferencevoltageanddynamicvoltageadjustmentoutputtoaccessAD603gaincontrolterminaltocontroltheamplificationgain,thereforeachievethegoalofconstantsystemoutputamplitude.AD603CatalogI.DescriptionII.WorkingPrincipleoftheSystemIII.AD603IV.MC34063V.SystemHardwareCircuitDiagram5.1InputBufferAttenuationCircuit5.2AD603AutomaticGainAmplifier5.3OutputAmplitudeDetector5.4MC34063FeedbackCircuitVI.SystemOperationResultsVII.ConclusionFAQOrdering&QuantityII.WorkingPrincipleoftheSystemThesystemusesAD603asthecorecontroldevice,supplementedbytheswitchingpowersupplychipMC34063tocollecttheoutputofthecontroller,theoutputvoltageistransferredtothevoltagecontrolterminalofAD603throughMC34063tochangetheamplificationgain.ThesystemworkingprincipleblockdiagramisshownasinFig.1.Figure1SystemBlockdiagramInthisclosed-loopcontrolsystem,theMC34063circuitisusedasitsfeedbacklinktodynamicallycollecttheamplitudeoftheoutputsignalofthesystem,andcontroltheamplificationgainofAD603byadjustingthedutycycleoutputvoltageoftheinternalsignal.Thefeedbacklinkinthefigurecanbereplacedwithamicroprocessor.ThemicroprocessorcollectstheoutputvoltageamplitudethroughA/D,transfersittothemicroprocessorchipforsignalprocessing,andthenfeedsbacktotheinputoftheentiresystemthroughD/Aoutputcontrolvoltage.However,thismethodistoocomplicated,becausetheriseandfallofthedigitalchiptakealongtimetosetup,whichaffectstheresponsespeedoftheentiresystem,andrequiresrelativelyhighsignalprocessingalgorithms.Theswitchingpowersupplychipwidelyusedinpowersupplytechnologyisdynamicallyadjustedtoimproveitsoperatingspeed.Inaddition,itsdevelopmentcostislow,whichisconducivetothepromotionoftheindustrialcontrolfield.III.AD603AD603isachipwithprogrammablegain,lownoise,ithas3workingmodes,correspondingtodifferentgainranges.Inordertomakethecontrolmoreextensive,themaximumbandwidthmodeisselectedas90MHz.Thegainisexpressedindecibels,theamplificationgainiscontrolledbythecontrolvoltagetoalinearrelationshipof25mV/dB,andtheslewrateis275V/s.Thegaincontrolvoltageneedstobeinputduringnormaloperation.Thegainformulais:Intheformula:Gisthegain,dB;G0isthestartingpointofthegain,andthesizeofG0isdeterminedbythepinconnection.Thecircuitdesignedinthispapershort-circuitsVOUTandFDBK,G0=10dBisthewidebandmode(90MHzwideband),thegainrangeGofAD603is-11.09~+31.05dB,andVGisinthelinearrangewhentherangeis-500~500mV.ThegaincontrolvoltageVGiscontrolledbytheMC34063output.AD603inputsignalamplitudeUINP1.4V,theactualindustrialcontrolfieldofteninputplusinterferencesumisgreaterthan1.4V,ifthissignalisdirectlyaddedtothesystem,thedistortionislargeandlong-timeworkwilldamagetheAD603,soyoumustaddaninputbufferandattenuationcircuit.IV.MC34063MC34063isamonolithicbipolarintegratedcircuitusedinthefieldofDC-DCconvertercontrol.Itischeapandwidelyusedinthefieldofswitchingpowersupplies.Itcanuseaminimumofexternalcomponentstoachieveswitchingboostandbuck.Itsoperatingfrequencyis0.1-100kHz.ThetraditionalAGCcontrollerconstitutesaclosed-loopcontrolsystem,whichgenerallyneedstoperformA/Dsamplingontheoutputofthesystem,andthentransferthedatatothesingle-chiporcomputerforalgorithmdataprocessing,andjudgetheexecutionsignalD/Aoutputtomaketheactuatorexecute.Inthisfeedbackprocess,sampling,algorithmprocessingandexecutionobviouslyconsumetoomuchtime,andforsomecomplexcontrolsignals,algorithmdataprocessingrequirementsarehigh,andspecialDSPchipsarerequired,whichiscostly.Therefore,theuseofasingleanalogelectroniccircuittoachieveaclosed-loopcontrolsystemhashigherefficiencyandlowercost.InspiredbytheworkingmodeoftheMC34063step-downcircuit,itisanewdesignideatorealizethechangeoftheAD603gaincontrolvoltagebyusingthecharacteristicsoftheMC34063todynamicallyadjusttheoutputvoltage.Theexperimentalverificationisfeasibleanditissimplerandfasterthantheprogramcontrolmethod.Figure2showstheMC34063step-downcircuit.Figure2MC34063step-downcircuitAsshowninFigure2,theinputis+12V,theoutputis+5V,thereferencevoltageofpin5togroundis+1.25V,theresistanceofpin5togroundisR1=1.2k,andtheoutputandpin5areconnectedtoR2=3.6k,Accordingtotheresistancedividerratio,theoutputisclampedat+5V,thusachievingaregulatedoutput.AppliedinthefieldofAGCcontrol,youcanconnecttheoutputofMC34063tothecontrollergaincontrolterminal,andtheinputtotheoutputterminalofthecontroller.Accordingtoitsworkingprinciple,MC34063collectstheoutputoftheAGCcontrollerandtransmitsittopin5.ItsinternaldynamicallyadjuststhePWMdutycycle,dynamicallychangestheAD603gaincontrolvoltage,andcanavoidtheinterferenceofthesystem,andrealizethefunctionsimilartothePIDalgorithm.Itreplacesthealgorithmicdataprocessingmechanism,whichissimpleandeffective,andhascertainreferencesignificancetothefieldofindustrialautomationcontrol.V.SystemHardwareCircuitDiagramFigure3isthesystemhardwarecircuitdiagram.Thesystemismainlydividedintoinputbufferattenuationcircuit,AD603automaticgainamplifier,outputamplitudedetectorandMC34063feedbackcircuit.Figure3SystemHardwarecircuitdiagram5.1InputBufferAttenuationCircuitBecausetheAD603inputsignalamplitudeVINPislessthanorequalto1.4V,fourdiodeclampsareused.Accordingtotheunidirectionalconductivityofthediodeandtheforwardconductionvoltagedropofsilicon,theinputcharacteristicsarelimitedtomeettherequirementsofAD603.Theinputvoltagerequirements,thefollowerplaystheroleofisolatingthechip.AsshowninFigure3,part①.5.2AD603AutomaticGainAmplifierThe3pinofAD603isthesignalinputterminal,the2and4pinsareconnectedtothegroundwithR4=0,R5=0resistancetomakeitworkmorestable.The5and7pinsareconnectedtotheoutput,whichisthesystemoutputoftheAGCcontroller.Pin1isthegaincontrolvoltageVGterminal,thiscontrolvoltageisconnectedtotheoutputterminalofMC34063,MC34063generatesthecorrespondinggaincontrolvoltageVGaccordingtotheoutputofthesystem.5.3OutputAmplitudeDetectorInthefieldofindustrialcontrol,thesignalisonlyintheformofDC,andtheACsignalalsooccupiesacertainproportion.ForthecontroloftheDCsignal,thesystemoutputcanbedirectlytransmittedtotheMC34063forprocessing,buttheamplitudeoftheACsignalmustbedetected,sothedesignisshowninFigure3inpart③.Commonamplitudedetectors,suchasdioderectifierbridges,areonlysuitableforsituationswheretheinputvoltageisfargreaterthanthediodeconductionvoltagedrop.InAGCcontrol,thesignalinthesystemisoftenlowvoltage,soitcannotbeused,soitisverynecessarytodesignanamplitudedetectorthatcanavoiddiodeconductionvoltagedrop.AfterRCcharging,theDCvoltagevaluewithacertainrelationshipisobtained.InFigure3,thevoltageattheintermediatenodeofR13andR14isUf,andtheexpressionis:Intheformula,UINPistheinputamplitude,V.5.4MC34063FeedbackCircuitTheintermediatenodevoltageUfofR13andR14isproperlycalculatedbyasame-invertingamplifierandanadder,andthenconnectedtopin5ofMC34063.Atthistime,itisclampedat5V,andUf=1Vwhenreversed,thentheAGCcontrollersystemcanbedynamicallymaintainedstabilityofoutputvoltageamplitude.Whenthesysteminputisunstableorthereisnoiseinterference,MC34063dynamicallychangestheoutputvoltagevalueaccordingtotheamplitudedetectionresult,soastoachievethepurposeofchangingthegaincontrolvoltageVG.AsshowninthelowerpartofFigure3,theoutputvoltageofpin2ischargedanddischargedthroughswitchingandspecificSchottkydiodes,andtheattenuatedpartialvoltageistransmittedtopin1ofAD603,whichrealizestheautomaticadjustmentoftheamplificationgainandsuccessfullyrealizestheswitchingpowersupplytechnologyapplicationinthefieldofautomaticcontrolgain.VI.SystemOperationResultsTheexperimentalsettingisthatifthesysteminputsaDCsignal,theoutputwillbeaconstant+1VDC;ifanACsignalisinput,theoutputwillbeanACsignalwithaconstantamplitudeof+1V.Intheexperiment,twoinputmethodsweretestedandverified,andbothmetthedesignrequirements.Table1ispartoftheexperimentaldataoftheinputDCsignal.Intheexperiment,theinputoftheAGCcontrollerisconnectedtothevoltageregulatorsource,andtheinputvoltageiscontinuouslyadjusted.Table2ispartoftheexperimentaldataoftheinputACsignal.Intheexperiment,theAGCcontrollerinputisconnectedtotheUTG9002Csignalgenerator,theamplitudeoftheinputsinewaveiscontinuouslyadjusted,andtheoutputisconnectedtotheoscilloscopetoobservethewaveform.Observationfoundthatnomattertheinputamplitudebecomeslargerorsmaller,theoscilloscopewaveformisbasicallyunchanged.ReadtheoscilloscopewaveformamplitudeandfillinTable2.VII.ConclusionThisarticlesummarizesthedesignoftheAGCcontrollerbasedonAD603andMC34063.ExperimentshaveverifiedthattheAGCcontrolleriseffectiveandmeetsthedesignrequirements.Anewapplicationofswitchingpowersupplychipsinthecontrolfieldisproposed.BecausetheinternalPWMdutycycleisfaster,itcanreplacethetraditionalprogrammableAGCcontroller.Amongthem,MC34063canalsobereplacedbyotherswitchingpowersupplychips.Ithastheadvantagesofuniversalapplicability,simpledesign,lowcost,andithasimportantpracticalvalue.FAQWhatisAD603?AD603isalow-noise,voltage-controlledamplifierforradiofrequency(RF)andintermediatefrequency(IF)automaticgaincontrol(AGC)systems.Itprovidesprecisepin-selectablegain,withagainrangeof-11dBto+31dBat90MHzbandwidth,andagainrangeof+9dBto+51dBat9MHzbandwidth.Anyintermediategainrangecanbeobtainedwithanexternalresistor.Thenoisespectraldensityreferredtotheinputisonly1.3nV/Hz,andthepowerconsumptionis125mWwhenusingtherecommended5Vpowersupply.WhataretheproblemsthatneedtobepaidattentiontowhenusingAD603?Thevoltagecannotbetoohigh.Generally,thevoltageisplusorminus5V,andthemaximumvoltagecannotexceedplusorminus7.5V.Theoutputvoltagecannotexceed2V.Howtosolvetheself-oscillationproblemofAD603?Forhigh-frequencyoperationalamplifiers,thefollowingpointsarethebasicwaystosolveself-excitation.Thepowersupplyisstableandnoripple.Theelectricalconnectionwiresareasshortaspossible.Thead603circuitshouldbefarawayfromthepowercircuit,especiallyawayfromthetransformer.Thepowertransformerandthecircuitboardofad603shouldbeshieldedwithametalboxandgroundedifpossible.Onepointisveryimportant.Foropamps,toolargemagnificationcaneasilycauseself-excitation,soreducethemagnificationasmuchaspossibleandminimizethenumberofmagnificationlevels(generallynotgreaterthan4).Reverseamplificationcansuppressself-excitationinmulti-stageamplification.Ifyouwanttoconnecttothepoweramplifierandthenamplify,itisbesttousetwopowersupplies,andthecircuitshouldbeconnectedtothesameground.WhatisthedifferencebetweenAD603AQandAD603AR?Theirdifferencesareinmodel,Temperature,Package.AD603AQ-40Cto+85C8-LeadCERDIPAD603AR-40Cto+85C8-LeadSOIC_NAfterinputtinganACsignalandbeingamplifiedbyAD603,whydoestheoutputcontainaDCsignal?HowtoeliminatetheDCsignal?WhentheDCblockingcapacitorisnotused,thebiasvoltageoftheinputcircuitneedstobeadjustedforcompensation.IftheDCvoltageoftheACsignalisnotfixed,onlyaDCblockingcapacitorcanbeused,ortheaveragevaluecanbeusedtoeliminateitaftersamplingthenumber.I.IntroductionForlargesystemssuchasmissileweaponsandequipment,theirperformanceisoftenaffectedbytheexternalenvironmentandtheirownoperatingconditions.Amongthem,theinfluenceoftemperatureoftenplaysaveryimportantrole.Therefore,temperaturedetectionandcontrolhasalwaysbeenthefocusofmanyresearchers.However,sometemperaturemeasurementandcontroldeviceshavelowaccuracyandinaccuratetemperaturecontrol,andsomenewinstrumentsareexpensiveanddifficulttopromote.Itshouldbeparticularlypointedoutthatthetemperaturemeasurementandcontrolsystemdevelopedinthepastisusuallyanindependentsystem,onethingforoneuse,itisdifficulttobeadoptedbyothersystems,andthereareproblemssuchasmaintenancedifficultiesandinconvenience.Tothisend,theauthordevelopedahigh-precisiontemperaturemeasurementandcontroldevicesuitableforresearchanddevelopmentunderlaboratoryconditionsbasedonthecurrentlypopularmodulardesignprinciple.ThedeviceusesanewintegratedtemperaturesensorAD590asthetemperaturemeasurementelement,andprovidestwocontrolunitsforexperimentalcomparison.Bymeasuringandcontrollingthetemperatureinthethermostat,satisfactoryresultshavebeenobtained.CatalogI.IntroductionII.WorkingPrincipleIII.IntegratedTemperatureSensorAD590IV.TemperatureMeasuringBridgeV.PIDRegulatorVI.ProgramDesignVII.ExperimentalAnalysisandConclusionFAQOrdering&QuantityII.WorkingPrincipleFigure1istheelectricalschematicdiagramoftheWCZ-98temperaturemeasurementandcontroldevice.Itsworkingprincipleis:thetemperaturesignaltakenbythetemperaturemeasuringbridgewithAD590asabridgearmisdifferentiallyamplifiedandbufferedandthensentallthewaytothedigitaldisplayfordigitaltemperaturedisplay,andtheotheriscomparedwiththesetvalue.ThecompareddifferenceiscontrolledbyswitchKandcanchoosetosendtotwo-wayadjustmentcontroller.Onerouteiscomposedofacomparisonamplifierandarelay,whichcanbeusedasanadjustmentcontrollertoformanindependenttemperaturemeasurementandcontrolequipmentwithoutconnectingtoacomputer;theotherrouteisaPIDregulator(composedofA/D,D/AandComputercompositionofPIDadjustmentsoftware)andSCRcomposition.Thesignalfromtheregulatingcontrollerrealizestemperaturecontrolthroughthetemperaturecontrolactuator.Figure1ElectricalschematicdiagramoftemperaturemeasurementandcontroldeviceIII.IntegratedTemperatureSensorAD590AD590isadedicatedintegratedtemperaturesensorproducedbyAmericanADcompany,whichbelongstothecurrentoutputtype.Figure2showsthecurrent-voltagecharacteristiccurveofAD590atthreedifferenttemperatures.Inacertaintemperaturerange,itisequivalenttoahighresistancecurrentsource,anditscurrenttemperaturesensitivityislA/K.Itisnotsusceptibletointerferencefromcontactresistance,leadresistance,voltagenoise,etc.Inaddition,italsohasthecharacteristicsofsmallsize,hightemperaturemeasurementaccuracy,goodlinearityandstronginterchangeability.Itisverysuitableforlong-distancemeasurementandcontrol.Itisalsosuitableforthecharacteristicsofmodularandsplitstructurerequiredbythisarticle.Themaintechnicalindicatorsare:Temperaturemeasurementrange:hCurrentoutput(calibrationfactor):lA/K;Powersupplyvoltage:DC4-30V;Linearity:lessthan0.5℃inthefullscalerange;Repeatability:0.1℃;Outputimpedance:about10MQLong-termdrift:0.1℃/monthFigure2I-VcurveofAD590ThecurrentIrflowingthroughtheAD590isasingle-valuedfunctionoftheabsolutetemperatureofitsenvironment,andthemicroampereofIrisequaltotheabsolutetemperatureT,namely:Ir=T10-6A=TA(1)IV.TemperatureMeasuringBridgeFigure3istheschematicdiagramofthetemperaturemeasurementbridge.ThevoltageformedonthecurrentIiR2andRw2flowingthroughtheAD590is:Ul=Ii(R2+Rw2)(2)Figure3SchematicdiagramoftemperaturemeasuringbridgeByadjustingRw2tomake(R2+Rw2)equalto10K,substitutingformula(1)intoformula(2),wecanget:U1=Ii(R2+Rw2)=T10-2V(3)U2=2.732VbyadjustingRwl.Thentheoutputofthebridgeis:UAB=U1﹣U2=T10-2﹣2.732=(T﹣273.2)10-2V(4)BecauseTistheabsoluteambienttemperaturemeasuredbyAD590,aftersubtracting273.2fromit,theCelsiustemperaturetcanbeobtained,namely:UAB=t10-2V(5)Atthispoint,thetemperaturemeasuringbridgeconvertstheambienttemperatureintoavoltagevaluethatisproportionaltothetemperatureinCelsius.V.PIDRegulatorOneoftheadjustmentcontrollersofthetemperaturemeasurementandcontroldeviceusesaPIDregulator(proportionalintegralderivativeregulator),whichcandeterminethesizeofthecontrolquantityaccordingtotheproportionalvalue,integralvalue,andderivativevalueofthedifferencebetweenthetemperaturesetvalueandtheactualvalue.Thetemperaturemeasurementandcontroldeviceadoptstheoutputfeedbacktypecontrol.Extractingthispartfromthegeneralprinciplediagram,youcangetthePIDcontrolprinciplediagramasshowninFigure4.Inthefigure,UdandUarethesetvalueandactualvalueofthethermostatrespectively,theerrore=Ud﹣KT,Kisthemagnificationofthemeasuringtransducer,andYistheadjustmentvalueofthePIDoutput.Figure4PIDcontrolprinciplediagramThesimulationexpressionofPIDalgorithmis:Intheformula,Y(t):regulatoroutputvalue;E(t):inputdeviation;KP:regulatorproportionalcoefficient;Tl,TD:verseunitintegral,derivativetimeAfterdiscretizingequation(6),thePIDincrementalcontrolequationisobtained:Intheformula,theintegralcoefficientKl=KPT/T1,thedifferentialcoefficientKD=KPTD/r,andTisthesamplingperiod.thenapply(7)toZ-transform,andget:Intheexperiment,theauthorusedastepsignaltoroughlymeasuretheresponseintheopen-loopstate.Fromthestepresponsecurve,itisknownthatthethermostatisafirst-orderinertialinkplusapuretimedelaylink,namely:Thelagtimerofthesystemisdeterminedtobeapproximately20seconds,andthetargettimeconstantTPisapproximately50seconds.Selectthecontroldegreetobe1.5,accordingtothestepresponsecurvetuningparametermethod(refertoliterature[1]),obtain:T=0.34z=6.8sKr=0.85Tr,/r=2.125T1=1.62r=32.4sTD=0.65r=13sSubstitutingtheabovevalueforequation(9),wecanobtain:Q0=6.41Q1=-5.96Q2=4.06TheequationofPIDregulatoris:VI.ProgramDesignThePIDcontrolprogramflowoftheWCZ-98temperaturemeasurementandcontroldeviceisshowninFigure5.ThebasicideaisthesameasthegeneralPIDcontrolflow.Itsnoneedtorepeathere.Figure5PIDcontrolprogramflowchartVII.ExperimentalAnalysisandConclusionPutthetemperaturemeasurementandcontroldeviceintoathermostatwithanexternaldimensionof248208262(mm).Thethermostatuses50mmthickpolystyreneastheheatinsulationmaterialandwaterasthemedium.Theheatingdeviceiscomposedof2SRS3-220/0.5heatingtubesandauxiliarypartstopreventleakage.Thetemperaturecanbepresetoutsidethethermostatandthereisaswitchtoselectthetypeofcontroller.Throughexperiments,comparingthecontroleffectsofthetwoadjustmentcontrolmethods,wefoundthatthetemperatureoftheadjustmentcontrollercomposedofacomparisonamplifierandarelayisnotstableduringthetemperaturecontrolprocessandalwaysfluctuateswithinacertainerrorrange.ThetemperaturecontrolperformanceoftheregulatingcontrollercomposedofPIDregulatorandthyristorisverygood.Takingtemperaturecontrolof60Casanexample,thetemperaturechangecurveobtainedbytheexperimentisshowninFigure6.Figure6PIDtemperaturecontrolexperimentresultcurveItcanbeseenthattheuseofanalogcircuitsforadjustmentandcontrolisbeneficialtomakethemeasurementandcontroldeviceanindependentinstrument(noneedtoconnecttoacomputer),anditstemperaturemeasurementandcontrolaccuracycanmeetthegeneralrequirements;andthroughPIDcontrol,itsprecisionoftemperaturemeasurementandcontrolisveryhigh.Itisusedinconjunctionwiththethermostatandtheself-developedSYZJX-2experimentaladapterbox.TheanaloginputboardPCL-818LandtheanalogoutputboardPCL-726areconnectedtothecomputertoachievehigh-precisiontemperaturecontrol.FAQWhatisAD590?AD590isatemperaturesensor,thecurrentoutputsensitivityis1A/℃,thestandardoutputvalueis298.2Aat25℃,andtheworkingvoltagerangeis4~30V.WhatarethecharacteristicsofAD590temperaturesensor?Singlefunction(onlytemperaturemeasurement),smalltemperaturemeasurementerror,lowprice,fastresponsespeed,longtransmissiondistance,smallsize,micropowerconsumption,etc.Itissuitableforremotetemperaturemeasurementandtemperaturecontrolwithoutnon-linearcalibration.Theperipheralcircuitissimple.HowtodetectthequalityofAD590?AD590hasacurrentof273mAat0.Because2113isaWensensitiveresistor5261,itmeansthatitisgreatlyaffectedbythesurroundingtemperature4102.Itisverydifficulttomeasurewithoutrelyingon1653othertools.Giveyousomesuggestions.Whentheambienttemperaturerisesbyonedegree,thecurrentofAD590increasesby1uA.WhatyouhavetodoistoworkwithAD590simultaneouslywiththehelpofahigh-precisiontemperaturetestinstrument.AfterAD590series10Kresistance,measureitsvoltage,thatistosay,itshouldbe2.73Vat0,and2.98Vatroomtemperature25.Forhigheraccuracy,itisrecommendedthatyouusetheelectronicbuildingblocksoftwareArdunioformeasurement,andputthecorrespondingdataintoMATLABforlinearregression.Thebetterthelinearity,themorestablethemeasurement.AD590isnotahigh-precisiontemperaturetestingdevice.Ifhigh-precisiontestingisrequired,othercomponentsarerecommended.WhatisthedifferencebetweenAD590andPT100?AD590isacurrent-typetemperaturesensor.Itconvertstemperaturechangesintocurrentconversion.Thesimplestprocessingistopassaresistor(10K)aftertheoutputtoconvertthecurrentintoavoltage,andthenthroughthedetectionvoltage,thecurrentatthistimecanbededuced.Usetherelationshipbetweencurrentandtemperatureinthesensordatatocalculatethecurrenttemperature.PT100isaresistancetypetemperaturesensor,whichconvertstemperaturechangesintoresistancechanges.ThesimplestprocessistoplacePt100inabridge,usethevoltagedifferenceatthemidpointofthebridgearm,anduseadifferentialamplifiercircuit(instrumentamplifiercircuit)Amplifythevoltage,usetheamplifiergainandbridgestructuredata,andusethedetectedvoltagetoinverselycalculatethecurrentresistancevalue,andusetherelationshipbetweenresistanceandtemperatureinthePT100datasheettocalculatethecurrenttemperature.IsAD590athermocoupleorathermalresistance?Itisneitherathermocouplenorathermalresistance.Themainprincipleistodetectthetemperatureaccordingtothetemperaturechange,theoutputcurrentchange,andthecurrentsize.

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