Tkool Electronics

L298DescriptionTheL298isanintegratedmonolithiccircuitina15-leadMultiwattandPowerSO20packages.Itisahighvoltage,ahighcurrentdualfull-bridgedriverdesignedtoacceptstandardTTLlogiclevelsanddriveinductiveloadssuchasrelays,solenoids,DCandsteppingmotors.Twoenableinputsareprovidedtoenableordisablethedeviceindependentlyoftheinputsignals.Theyaremostlyused:whenitisneededtooperatedifferentloadslikemotorsandsolenoidetcwhereanH-BridgeisrequiredwhenhighpowermotordriverisrequiredwhenthecontrolunitcanonlyprovideTTLoutputswhencurrentcontrolandPWMoperablesingle-chipdeviceisneededCatalogL298DescriptionL298CircuitDiagramL298FeaturesandSpecificationsL298PinConfigurationsandFunctionsL298PackageOutlineandMechanicalDataWheretouseL298ICHowtouseL298ICL298ApplicationsL298ComparewithOtherMotorsProductManufacturerComponentDatasheetFAQOrdering&QuantityL298CircuitDiagramL298FeaturesandSpecificationsOperatingsupplyvoltageupto46vTotalDCcurrentupto4A25wratedpower2enablecontrolterminalstoenableordevicewithoutinputtingsignals.Abletodriveatwo-phasesteppermotor,four-phasesteppermotorortwoDCmotorsLowsaturationvoltageOvertemperatureprotectionLogical0inputvoltageupto1.5V(highnoiseimmunity)Operatingtemperature:-23Cto130CStorageTemperature:-40Cto150CL298PinConfigurationsandFunctionsPinoutFunctions:L298PackageOutlineandMechanicalDataL298(Multiwatt15V)L298(Multiwatt15H)L298(PowerSO20)WheretouseL298ICHereareafewareaswhereL298ispreferred:L298isbasicallyusedwhereH-BRIDGEisrequired.Whereahighpowermotordriverisrequired.Inthemarked,thereareH-bridgeslikeL293whichareusedforthelowpoweredapplicationwhileL298isspeciallydesignedforthehighpowerapplications.WherecurrentcontrolandPWMoperablesingle-chipdeviceisneeded.ThechipispreferredwhencontrolunitcanonlyprovideTTLoutputAlso,thechipdoesnotneedanyadditionalcomponentstobeinstalledforoperating.HowtouseL298ICForunderstandingtheworkingofL298IC,considerthesimplecircuitconfigurationshownbelow.HereweareusingoneofH-BRIDGESofl298IC.AsshowninthecircuitwehavetwopushbuttonsQ1andQ2whichactascontrolsinputsforbridge-A.TheselogicinputsareprovidedbyMicrocontrollerorMicroprocessorinapplicationcircuits.ThefourdiodesareFLYBACKdiodesusedforprotectingtheICforminductivevoltagespikes.Theenablepinispulledhighthrougharesistorsobridge-Awillbefunctioningallthetime.Ifitspulledtogroundthebridge-Awillbedisablednomattertheinputcontrollogic.AfterallthecircuitaresetupweneedtopressthebuttonsQ1andQ2tochangetheflowofcurrentbetweenpinsOUT1andOUT2.Thelogiccontroltableisgivenbelow.INPUTSFUNCTIONQ1=HIGH,Q2=LOWForwardcurrentQ1=LOW,Q2=HIGHReversecurrentQ1=Q2FastMOTORstopSoifonlyQ1ispressed,thecurrentflowsfromOUT1toOUT2.WiththatMOTORrotatesclockwisedirection.IfonlyQ2ispressed,thecurrentflowsfromOUT2toOUT1.WiththatMOTORrotatesanti-clockwisedirection.IfbothbuttonsarepressedorreleasedsimultaneouslytheMOTORcomestostopimmediately.Inthisway,wecancontrolthemotorrotationusingtheL298chip.L298ApplicationsRoboticarmsRobotsRelaydriversVendingmachinesIndustrialmachinesEngineeringsystemsMeasuringinstrumentsHobbyprojectsL298ComparewithOtherMotorsWithsomanymotordriverscurrentlysuchasServoMotorsandsteppermotors,whatreallyarethedifferencesbetweenthemotordriversandwhichonetochoose?Noworries,aswehavecraftedatablejustforyoutocomparethevariousmotordriverssoyouknowwhichmotordriverfitsthebestforyourproject.TypeMotorDriversChipActuatorWorkingVoltageWorkingCurrentGroveGroveI2CMotorDriverL298N2DCmotoror1Stepper6v-15v2.0Aeach(Max)GroveI2CMotorDriver(TB6612FNG)TB6612FNG2DCmotoror1Stepper2.5v-13.5v(5Avg,15vMax)1.2A(Avg)to3.2A(Max)GroveI2CMiniMotorDriverDRV88302DCMotor2.75v-6.8v0.2Ato1AeachShieldMotorShieldV2.0L298N2DCmotoror1Stepper6v-15v2.0Aeach(Max)4AMotorShieldMC339322DCMotor6v-28v5.0Aeach(Max)BrushlessMotorShield(TB6605FTG)TB6605FTG1DCBrushlessMotor9v-24v-ProductManufacturerSTmicroelectronics(ST)groupwasestablishedinJune1988asaresultofthemergerofSGSMicroelectronicsofItalyandThomsonOfFrance.InMay1998SGS-ThomsonMicroelectronicschangeditsnametoSTmicroelectronicsLimited.Itistheworldslargestmanufacturerofdedicatedanalogchipsandpowerconversionchips,theworldslargestsupplierofindustrialsemiconductorsandset-topboxchips,andaworldleaderindiscretecomponents,mobilephonecameramodules,andautomotiveintegratedcircuits.ComponentDatasheetL298DatasheetFAQWhatisl298n?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.Whatistheuseofl298n?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.Howdoesl298ncontrolDCmotorspeed?1.IfyousendaHIGHsignaltotheenable1pin,motorAisreadytobecontrolledandatthemaximumspeed;2.IfyousendaLOWsignaltotheenable1pin,motorAturnsoff;3.IfyousendaPWMsignal,youcancontrolthespeedofthemotor.Themotorspeedisproportionaltothedutycycle.Whatisl298nmotordrivermodule?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.Howdoesl298nmotordriverwork?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.HowdoIuseanl298motordriverwithArduino?Startbyconnectingpowersupplytothemotors.Inourexperiment,weareusingDCGearboxMotors(alsoknownasTTmotors)thatareusuallyfoundintwo-wheel-driverobots.Theyareratedfor3to12V.So,wewillconnecttheexternal12VpowersupplytotheVCCterminal.WhatisthefunctionoftheHbridge?AnH-bridgeisanelectroniccircuitthatswitchesthepolarityofavoltageappliedtoaload.ThesecircuitsareoftenusedinroboticsandotherapplicationstoallowDCmotorstorunforwardsorbackwards.Whatisthedifferencebetweenl293dandl298n?L293isaquadruplehalf-HdriverwhileL298isdualfull-Hdriver,i.e,inL293allfourinput-outputlinesareindependentwhileinL298,ahalfHdrivercannotbeusedindependently,onlyfullHdriverhastobeused....Hence,heatsinkisprovidedinL298.

TPS73701

L298DescriptionTheL298isanintegratedmonolithiccircuitina15-leadMultiwattandPowerSO20packages.Itisahighvoltage,ahighcurrentdualfull-bridgedriverdesignedtoacceptstandardTTLlogiclevelsanddriveinductiveloadssuchasrelays,solenoids,DCandsteppingmotors.Twoenableinputsareprovidedtoenableordisablethedeviceindependentlyoftheinputsignals.Theyaremostlyused:whenitisneededtooperatedifferentloadslikemotorsandsolenoidetcwhereanH-BridgeisrequiredwhenhighpowermotordriverisrequiredwhenthecontrolunitcanonlyprovideTTLoutputswhencurrentcontrolandPWMoperablesingle-chipdeviceisneededCatalogL298DescriptionL298CircuitDiagramL298FeaturesandSpecificationsL298PinConfigurationsandFunctionsL298PackageOutlineandMechanicalDataWheretouseL298ICHowtouseL298ICL298ApplicationsL298ComparewithOtherMotorsProductManufacturerComponentDatasheetFAQOrdering&QuantityL298CircuitDiagramL298FeaturesandSpecificationsOperatingsupplyvoltageupto46vTotalDCcurrentupto4A25wratedpower2enablecontrolterminalstoenableordevicewithoutinputtingsignals.Abletodriveatwo-phasesteppermotor,four-phasesteppermotorortwoDCmotorsLowsaturationvoltageOvertemperatureprotectionLogical0inputvoltageupto1.5V(highnoiseimmunity)Operatingtemperature:-23Cto130CStorageTemperature:-40Cto150CL298PinConfigurationsandFunctionsPinoutFunctions:L298PackageOutlineandMechanicalDataL298(Multiwatt15V)L298(Multiwatt15H)L298(PowerSO20)WheretouseL298ICHereareafewareaswhereL298ispreferred:L298isbasicallyusedwhereH-BRIDGEisrequired.Whereahighpowermotordriverisrequired.Inthemarked,thereareH-bridgeslikeL293whichareusedforthelowpoweredapplicationwhileL298isspeciallydesignedforthehighpowerapplications.WherecurrentcontrolandPWMoperablesingle-chipdeviceisneeded.ThechipispreferredwhencontrolunitcanonlyprovideTTLoutputAlso,thechipdoesnotneedanyadditionalcomponentstobeinstalledforoperating.HowtouseL298ICForunderstandingtheworkingofL298IC,considerthesimplecircuitconfigurationshownbelow.HereweareusingoneofH-BRIDGESofl298IC.AsshowninthecircuitwehavetwopushbuttonsQ1andQ2whichactascontrolsinputsforbridge-A.TheselogicinputsareprovidedbyMicrocontrollerorMicroprocessorinapplicationcircuits.ThefourdiodesareFLYBACKdiodesusedforprotectingtheICforminductivevoltagespikes.Theenablepinispulledhighthrougharesistorsobridge-Awillbefunctioningallthetime.Ifitspulledtogroundthebridge-Awillbedisablednomattertheinputcontrollogic.AfterallthecircuitaresetupweneedtopressthebuttonsQ1andQ2tochangetheflowofcurrentbetweenpinsOUT1andOUT2.Thelogiccontroltableisgivenbelow.INPUTSFUNCTIONQ1=HIGH,Q2=LOWForwardcurrentQ1=LOW,Q2=HIGHReversecurrentQ1=Q2FastMOTORstopSoifonlyQ1ispressed,thecurrentflowsfromOUT1toOUT2.WiththatMOTORrotatesclockwisedirection.IfonlyQ2ispressed,thecurrentflowsfromOUT2toOUT1.WiththatMOTORrotatesanti-clockwisedirection.IfbothbuttonsarepressedorreleasedsimultaneouslytheMOTORcomestostopimmediately.Inthisway,wecancontrolthemotorrotationusingtheL298chip.L298ApplicationsRoboticarmsRobotsRelaydriversVendingmachinesIndustrialmachinesEngineeringsystemsMeasuringinstrumentsHobbyprojectsL298ComparewithOtherMotorsWithsomanymotordriverscurrentlysuchasServoMotorsandsteppermotors,whatreallyarethedifferencesbetweenthemotordriversandwhichonetochoose?Noworries,aswehavecraftedatablejustforyoutocomparethevariousmotordriverssoyouknowwhichmotordriverfitsthebestforyourproject.TypeMotorDriversChipActuatorWorkingVoltageWorkingCurrentGroveGroveI2CMotorDriverL298N2DCmotoror1Stepper6v-15v2.0Aeach(Max)GroveI2CMotorDriver(TB6612FNG)TB6612FNG2DCmotoror1Stepper2.5v-13.5v(5Avg,15vMax)1.2A(Avg)to3.2A(Max)GroveI2CMiniMotorDriverDRV88302DCMotor2.75v-6.8v0.2Ato1AeachShieldMotorShieldV2.0L298N2DCmotoror1Stepper6v-15v2.0Aeach(Max)4AMotorShieldMC339322DCMotor6v-28v5.0Aeach(Max)BrushlessMotorShield(TB6605FTG)TB6605FTG1DCBrushlessMotor9v-24v-ProductManufacturerSTmicroelectronics(ST)groupwasestablishedinJune1988asaresultofthemergerofSGSMicroelectronicsofItalyandThomsonOfFrance.InMay1998SGS-ThomsonMicroelectronicschangeditsnametoSTmicroelectronicsLimited.Itistheworldslargestmanufacturerofdedicatedanalogchipsandpowerconversionchips,theworldslargestsupplierofindustrialsemiconductorsandset-topboxchips,andaworldleaderindiscretecomponents,mobilephonecameramodules,andautomotiveintegratedcircuits.ComponentDatasheetL298DatasheetFAQWhatisl298n?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.Whatistheuseofl298n?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.Howdoesl298ncontrolDCmotorspeed?1.IfyousendaHIGHsignaltotheenable1pin,motorAisreadytobecontrolledandatthemaximumspeed;2.IfyousendaLOWsignaltotheenable1pin,motorAturnsoff;3.IfyousendaPWMsignal,youcancontrolthespeedofthemotor.Themotorspeedisproportionaltothedutycycle.Whatisl298nmotordrivermodule?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.Howdoesl298nmotordriverwork?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.HowdoIuseanl298motordriverwithArduino?Startbyconnectingpowersupplytothemotors.Inourexperiment,weareusingDCGearboxMotors(alsoknownasTTmotors)thatareusuallyfoundintwo-wheel-driverobots.Theyareratedfor3to12V.So,wewillconnecttheexternal12VpowersupplytotheVCCterminal.WhatisthefunctionoftheHbridge?AnH-bridgeisanelectroniccircuitthatswitchesthepolarityofavoltageappliedtoaload.ThesecircuitsareoftenusedinroboticsandotherapplicationstoallowDCmotorstorunforwardsorbackwards.Whatisthedifferencebetweenl293dandl298n?L293isaquadruplehalf-HdriverwhileL298isdualfull-Hdriver,i.e,inL293allfourinput-outputlinesareindependentwhileinL298,ahalfHdrivercannotbeusedindependently,onlyfullHdriverhastobeused....Hence,heatsinkisprovidedinL298.

IDescriptionThisblogintroducesthepoweramplifierwithNE5532andLM1875Tasthecorecomponents.Thepoweramplifierwearediscussinghereisahigh-fidelitytwo-channelstereosubwooferpoweramplifier.Here,wewilldiscussitsmethodsandprocedures,schematicdesign,assemblyanddebugging,andspeakerproduction.Hopethisblogcanprovideagoodreferenceforbeginners.Figure1.LM1875CatalogIDescriptionIILM1875TandNE5532Overview2.1PowerAmplifierLM1875T2.2Pre-amplificationComponentNE5532IIICompositionofPowerSupplyIVAssemblyandDebuggingSpeaker4.1ElectricalInspection4.2BoxProductionVIntheEndOrdering&QuantityIILM1875TandNE5532OverviewFirst,weintroducethecorecomponentsthatwewilluse.Andthen,thebasiccharacteristicsofthesecomponents.Audiopoweramplifierisgenerallycomposedofthefollowingthreeparts:powersupply,pre-amplifierandpost-amplifier.Here,wewillusehigh-efficiencyHI-FIpowerintegratedchipLM1875Tasthecoreoriginal.LM1875Tadoptsapositiveandnegative15Vdualpowersupply,theleft,andrightchannelsworkinOCLmode,andthebassworksinBTLmode.AsfarasthecharacteristicsofLM1875Tareconcerned,ithasthecharacteristicsofgoodsoundquality,goodfrequencyresponse,lowcostandrelativelysimplecircuit.Inaddition,thepre-amplifierpartusestheNE5532integratedoperationalamplifier.2.1PowerAmplifierLM1875TLM1875Thasexcellentperformance.Manyluxury-lookingactivespeakers,mid-rangepoweramplifiers,andsubwoofersonthemarketuseLM1875T.ThepoweramplifiercircuitcomposedofLM1875Tchiphasthefollowingcharacteristics:Theoutputpowerislarge,themaximumpowercanreachabout20W;Thestaticcurrentissmall,theloadcapacityisstrong,andthedynamiccurrentislarge,whichcandrive4~8speakers;Thecircuitissimple,easytomanufactureandlowcost;Withaninternalprotectioncircuit,itisahigh-fidelitypoweramplifiercomponentwithstableperformance.Theblogdesignofthisarticleisadual-channelstereosubwooferpoweramplifier,butLM1875Tisamono-channelpoweramplifierintegratedcircuit,sothedual-channelOCLworkingmodeusesoneLM1875Tforeachchannel.SincethebassworksinBTLmode,wehavetousetwopieces.LM1875Thas5pins.Theyarepositivepowersupply,negativepowersupply,positiveinput,reverseinput,andoutput.ThecircuitisshowninFigure2.Figure2.LM1875Circuit2.2Pre-amplificationComponentNE5532Beforethepoweramplifiercircuit,itisgenerallynecessarytoaddapreamplifier.Thepurposeofthisistoamplifythevoltageofvariousinputweakelectricalsignals.Inordertoensurethattheoutputelectricalsignalhashighfidelity,thepre-amplifierisNE5532.NE5532isahigh-performance,low-noise,dualoperationalamplifierintegratedcircuit.Comparedwithmanystandardopamps,NE5532hasbettersoundperformance,excellentoutputdrivecapability,relativelyhighsmallsignalbandwidth,andlargepowersupplyvoltagerange.Therefore,itisverysuitableforhigh-qualityandprofessionalaudioequipment,instruments,controlcircuitsandtelephonechannelamplifiers.Whenusedforaudioamplification,thetoneiswarmandhighfidelity.ThefunctionalblockdiagramofNE5532isshownasinFig.3.Figure3.NE5532FunctionalBlockDiagramIIICompositionofPowerSupplyLM1875Tadoptsapositiveandnegative15Vdualpowersupply.TheoperatingvoltageofNE5532isalso15V.Weneedtostepdownthemainspowerto15Vthroughastep-downtransformer,thenrectifyitthroughtherectifierbridgeKBL406,filteritthroughalargecapacitor,anddirectlysupplyittothepoweramplifier.Inthisway,largeroutputpowerisobtained.After7815and7915,theregulatedoutput15VisusedasthepowersupplyofthepreamplifierNE5532.ThecompositionofthepowersupplyisshowninFigure4.Figure4.PowerCircuitFigure5.PowerAmplifierCircuitBoardIVAssemblyandDebuggingSpeakerWhenstartingthecircuitinstallation,firstcheckthecircuitboardagainstthecircuitdiagram.Forexample,checkwhetherthemaincomponentsareinstalledcorrectly,andwhetherthesolderjointshavemissingsolderingorfalsesoldering.Thenturnonthepowertodebugthecircuit,andmakespeakersafterthedebuggingiscompleted.TheactualproductionisshowninFigure6.Figure6.PhysicalShootingPic4.1ElectricalInspectionUseanACsignalgeneratortoaddatinysinusoidalsignaltothesignalinput.Then,usetheoscilloscopetomeasurethethreeoutputsignalsofthepoweramplifierboard.Atthistime,observewhetherthesinemeetstherequirementsandwhethertheparametersinthetestarerelativelystable.Then,connecttwofull-rangespeakerstotheleftandrightchannels,andconnectawoofertothebassoutputport.Atthistime,addthesongsignaltocarefullycheckwhetherthethreespeakersareworkingproperlyandthesoundisgood.Iftheabovestepsarewellexpressed,thenproceedtothenextstep.4.2BoxProductionThekeytomakingspeakersistheselection,sizeandothersteps.Intheexperiment,weusedthelaminatesinthelaboratoryforsplicingandassembly.First,drawasketch.Thepaintingisdividedonthreedifferentsubstrates,andthenmadeintotwopartsrespectively.Afterdrilling,polishing,splicingandbonding,thecompletedcircuitpartsareinstalledintheirrespectiveparts.Then,wedividetheentirepoweramplifierintothreeparts.Twosatellitespeakers,aswellasawooferandpoweramplifierboard.Thesethreepartstogetherformacomplete2.1subwooferpoweramplifier.Here,thereisaplacethatneedsspecialattention.Whenmakingthebasspartofthecabinet,theimpactofvibrationshouldbefullyconsidered.Therefore,wehavetodesigndampingcomponents.VIntheEndAftertheinstallationisnormal,connectthemusicsignalsourceandlistentothemusiceffect.Thesoundreproducedbythiscircuithasastrongsenseofhierarchy,aclearsenseoforientation,andanobvioussenseofspaceanddistance.Inaddition,thesoundimageorientationisclear,thewidthisoutstanding,andthesounddynamicrangeislarge,givingpeoplearealfeeling.IntroductionLM3886isahigh-performanceaudiopoweramplifier.ItexhibitsextremelylowTHD+Nvaluesof0.03%attheratedoutputintotheratedloadovertheaudiospectrum,andprovidesexcellentlinearitywithanIMD(SMPTE)typicalratingof0.004%.Itisverysuitablefortheenthusiastswhopursuebothbeautifulsoundqualityandstrongvolume.ThisarticleintroducesseveralpracticalapplicationsofLM3886inhometheatersystems.ThisisatechnicalexaminationvediooftheLM3886Amplifier.CatalogIntroductionCatalogIHighQualityDual-channelPowerAmplifierIIPowerfulBTLPowerAmplifierIIISubwooferSpeakerOrdering&QuantityIHighQualityDualChannelPowerAmplifierLM3886outputsnearly70Wpoweratratedvoltageandthepeakpoweris150W.Thedualchannelpoweramplifieradoptssimpleandtypicalcircuit,whichcanreplaceavarietyofHI-FIpoweramplifier,andissuitablefortheleftandrightmainchannelofpoweramplifierinhomecinema.ThewholecircuitisinstalledonthesamePCB.EachofthetwoLM3886sisequippedwithaspecialaluminumradiator(length140,thickness50,height75(mm)),whicharefixedonbothsidesofthePCBtofacilitateheatdissipation.Thepowertransformercanchoosedouble24~28V,3~5A.IIPowerfulBTLPowerAmplifierApureBTLbridgeamplifieriscomposedofanoperationalamplifierNE5532,anLM3886in-phaseamplifierandanLM3886invertingamplifier,whichcaneasilyoutputmorethan200Wundistortedpower.Itcanbeusedindancehalls,karaoke,theatersandotheroccasions.Thiscircuitcankeepthesoundqualitynaturalandsmoothwhenplayingatlowvolume.BTLPoweramplifiercircuitisshowninFigure1.Onecircuitboardforeachchannel,withindependentrectification.Thesizeoftworadiatorsis140mminlength,50mminthicknessand100mminheight.Figure1.BTLPowerAmplifierCircuitIIISubwooferSpeakerFigure2isthecircuitofahouseholdsubwooferspeaker.Figure2.circuitofsubwooferspeakerInthepicture,theLinkwitzactivecompensatoraccuratelycontrolsthecenterfrequencyf1ofthecompensationpeakanditsQvalue,sothattheclosedbox(seeFigure3)withanaturalcornerfrequencyabout50Hzandthefrequencyresponsecurve(seeFigure4)extendsdownflatly.Thelowend-3dBpointreaches25Hz.Figure3.ClosedboxFigure4.frequencyresponsecurveInFigure4,curveAisnaturalfrequencyresponse;Biscompensationcurve;andCissystemfrequencyresponse.Theturningfrequencyofthelow-passfilteriscontinuouslyadjustablefrom80Hzto200Hz,sothattheactivesubwoofercanmatchthereadersdualchannelspeakerwithdifferentfrequencylimits.TheloudspeakerusessilverfluteYD310-43.Thebasindiameteris310mm.Themagnetdiameteris158mm.Theresonancefrequencyis25Hz.Q=0.35.Thecontinuouspoweris50W,andthesensitivityisashighas95dB.ComparedwiththeHiviS8unitwithasensitivityof88dB,thesensitivitydifferencebetweenthetwois7dB.Fortheclosedbox,theoutputsoundpressureofYindiYD310-43whenitinput50WisequivalenttotheoutputofHiviS8unitwhenitinput200W.YindicanalsobereplacedbytheBlueWhaleYD310-8XA.Insteadofthebassreflexwithpoortransientperformanceandlowsensitivity,itisbettertousethesimplestclosedbox.Theboxshallbesolidandairtight,filledwithglassfibercottonoracryliccottonforwarmthabsorption,andthesmallcavityatthebottomoftheboxshallbeusedtoinstallthecircuitpart.Forthesakeofsimpleinstallation,allcircuitsareinstalledonthePCB.ThePCB,radiator,switchandI/Oconnectorarefixedonthemetalpanel,andthenfixedonthespeakerwith6screws.Then,itcanworkafterconnectingtohornandtransformer.Connectthesubwooferactivespeakerwiththehomestereospeakertoforma3Dplaybacksystem.

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ⅠIntroductionAlinefollowingcardesignedwithLM393VoltageComparatorcapableoftrackingonaspecificrunway.Thelinefollowingcarmainlyincludesasolarpowersupplypartandatrackingcontrolpart.Thecontrolcircuitpartmainlyincludesabattery,aswitch,firstandsecondlightsensitivecircuits,aDCmotor,acomparisoncircuit,andamotordrivecircuit.ThisblogtestshowsthatthelinefollowingcarcontrolledbytheLM393voltagecomparatorhasthecharacteristicsofhighcontrolaccuracy,faststartandstop,etc.,andsolvestheproblemsofthecomplicatedcontrolcircuitstructureofthelinefollowingcarandthelargedeviationofthedrivingtrajectory.CatalogⅠIntroductionⅡWhatisLM393?ⅢWhatisALineFollowingCar?3.1SolarPowerDesign3.2LineFollowingDesignⅣCircuitDesignofLineFollowingCarⅤTestⅥConclusionOrdering&QuantityⅡWhatisLM393?TheLM393offersexceptionalvalueforcost-sensitiveapplicationswithaloweroffsetvoltage,highersupplyvoltagecapability,lowersupplycurrent,lowerinputbiascurrent,shorterpropagationdelay,aswellasimproved2kVESDperformanceandinputrobustnesswithdedicatedESDclamps.TheLM393devicesconsistoftwoindependentvoltagecomparatorsthataredesignedtooperatefromasinglepowersupplyoverawiderangeofvoltages.Thequiescentcurrentisindependentofthesupplyvoltage,andtheoutputscanbeconnectedtootheropen-collectoroutputstoachieveawiredANDrelationship.Figure1.LM393ⅢWhatisALineFollowingCar?Alinefollowingcarisacarthatcantravelalongapresettrajectory.Intheprocessofdrivingthelinefollowing,howtomakethecarcanaccuratelyfollowthetrajectorywithoutlargedeviationsisthefundamentalapplicationofthelinefollowingcar.However,theexistinglinefollowingcargenerallyusestheinfraredreflectionmethodtofeedbackthedrivingtrajectoryofthecar,thecontrolcircuitstructureismorecomplicated,andtheinfraredreflectioniseasilyaffected,sonotonlythecostishigher,butalsothedrivingtrajectoryofthecarispronetodeviation,soitoftendoesnotmatchthedesigntrajectory.UsingLM393voltagecomparatorasthemaincontrolchipofthetrackingcarwillbeabetterway.UsetheresistancechangeofthephotoresistorunderthelightintensityandtheLM393voltagecomparatortocontroltheleftandrightdrivingwheelsofthecartorealizethetrackingdriveofthecar,andcooperatewiththedisplaycircuittounderstandthestatusofthecar.TheprincipleblockdiagramoflinefollowingcarbasedonLM393voltagecomparatorisshowninFigure3.Figure2.LineFollowingCarⅣCircuitDesignofLineFollowingCarThecircuitdesignoflinefollowingcarbasedonLM393voltagecomparatormainlyincludessolarpowersupplyandcartrackingdesign.Themaincomponentsofthelinefollowingcarincludeabatterybox,acontrolcircuitboardattachedtothebottomofthebatteryboxbydouble-sidedadhesive,andseveralwheelassembliesinstalledonbothsidesofthecontrolcircuitboardandasolarbatterypanelinstalledabovethebatterybox.Figure3.BlockDiagramofLineFollowingCar3.1SolarPowerDesignThelinefollowingcaradoptsbatterypowersupplyandstorage.Thesolarbatteryboardprovidespowerforthebattery,thatis,thebatteryinthecarischargedfirst,andonlywhenthebatteryhasenoughpoweroutputvoltage,therequiredvoltagecanbeoutputattheoutputendofthebatterytodrivethetracingcar.ThedesignofthepowersupplypartmentionedinthisblogusesasinglelithiumbatterychargingmanagementchipTP4057withaninputvoltageof4V9V(typicalvalue5V),whichcanbeusedtochangetheresistancetocontrolthechargingcurrent,anditsadjustmentrangeis100mm500mAandthecut-offvoltageis4.2V.Thechargingcircuithassimpleperipherals,noexternalswitchtubeisrequired,andhasfunctionssuchaschargingindicationandfullindication,anti-reversebatterypositiveandnegativepolereverseconnectionprotection,andpowersupplyundervoltageprotection.Inadditiontousingsolarpanelstopowerthecircuit,itcanalsoworkwithUSBpowerandadapterpower.Figure4.SchematicDiagramofChargingCircuit3.2LineFollowingDesignThecartrackingadoptstheLM393voltagecomparatorasthecontrolcenteroftheentiretrackingcircuit.LM393isadualvoltagecomparatorintegratedcircuit,whichiscomposedoftwoindependentprecisionvoltagecomparators.Itsfunctionistocomparetwoinputvoltagesandchangetheleveloftheoutputvoltageaccordingtothelevelofthetwoinputvoltages.TheschematicdiagramusingtheLM393voltagecomparatorasthetrackingcontrolcircuitisshowninFigure5.ThiscarchoosesredLEDlightasitslightsource.Whenthelightsourceshinesonwhiteobjectsandblackobjects(thepredeterminedtrajectoryofthecarisblack),thereflectivityisdifferent.Thelightisreflectedontothephotoresistorthroughtheground.WhentheredLEDlightisprojectedonthewhiteareaandtheblacktrackline,theresistanceofthephotoresistorwillbesignificantlydifferentbecauseofthedifferentreflectance;Bydetectingtheresistancechangeofthephotoresistor,itcanbejudgedwhetherthecarisdrivingontheblacktrackline.ThiscarchoosesredLEDlightasitslightsource.Whenthelightsourceshinesonwhiteobjectsandblackobjects(thepredeterminedtrajectoryofthecarisblack),thereflectivityisdifferent.Thelightisreflectedontothephotoresistorthroughtheground.WhentheredLEDlightisprojectedonthewhiteareaandtheblacktrackline,theresistanceofthephotoresistorwillbesignificantlydifferentbecauseofthedifferentreflectance;Bydetectingtheresistancechangeofthephotoresistor,itcanbejudgedwhetherthecarisdrivingontheblacktrackline.Figure5.SchematicDiagramofTracingIftheresistanceofthephotoresistorchanges,itmeansthatthewhiteareahasbeendetected,andthecarhasdeviated;atthistime,themotoroftheleftorrightwheelofthecarisdeceleratedorevenstoppedtomakethecarreturntotheblacktrack.ThetrackcarrunsonasimilarS-shapedroutetoachievethelinefollowingfunction.Whenthereisanimbalance(forexample,onewheelispressedontheblacktrackline),themotorononesideisstoppedimmediately,andthemotorontheothersideisacceleratedtorotate,sothatthecarcancorrectthedirectionandreturntothecorrectdirection.Thewholeprocessisaclosedloopcontrol,soyoucanquicklyandsensitivelycontrolthemovementofthelinefollowingcar.Atthesametime,thephotoresistorcandetecttheintensityoftheexternallight.Thestrongertheexternallightis,thesmallertheresistancevalueofthephotoresistoris.TheleftandrightwheeldriveofthistrackingcarusesaDCmotorwithareductiongear.TheDCmotordrivesthecartoslowdown,otherwisethecarwillruntoofastifthespeedistoohigh.Moreover,thetorqueistoosmalltorunevenwithoutdeceleration.Themotorusedinthislinefollowingcarhasintegratedareductiongeartogreatlyreducethedifficultyofproductionanddebugging.Comparedwiththeuseofasingle-chipmicrocomputerasthecontrolcircuit,thecontrolcircuitcomposedoftheLM393voltagecomparatorhasasimplerstructure,isconvenientforassemblyanddebugging,andhasalowercost.ⅤTestFirstofall,placethecaronthewhitebackgroundtestfieldoftheblacktrackline(theblackrunwayisthecarspresettrack),andturnontheswitchesS1,S2,solarpanels(orbatteries)toprovideelectricity,sothatthevoltagecomparatorcontrolsthestartoftwoDCmotorstodrivethewheelassembliesonbothsidesofthecar.OurDIYlinefollowingcarbegantodrivealongthedesignedtrack(blackrunway)!Duringthedrivingofthecar,thelight-emittingdiodesD2andD3ontheleftandrightsidesofthecarbothemitredlightsources.Becausethelightsourceirradiatestheblackrunwayandthewhiterunwaywithdifferentreflectivity,andthephotoresistorcandetecttheexternallightintensity,thestrongertheexternallight,thesmallerthephotoresistorresistance,theweakertheexternallight,thegreatertheresistance.Therefore,whentheredLEDlightisprojectedontotheblackandwhiterunway,becauseofthedifferentreflectance,theresistanceofthephotoresistorwillbesignificantlydifferent.Figure6.RedLEDWhenthelightsourceisreflectedbytherunwaytothephotoresistorsR14andR15,thecomparatorcandeterminewhetherthecarisdrivingontheblacktracklineorthewhiteareaaccordingtothechangesintheresistanceofthephotoresistorsonbothsides.Andthroughthediodesandphotoresistorsontheleftandrightsides,wecanalsodeterminewhichsidethecarisdeflectingatthistime.Whenanimbalanceoccurs(forexample,thesideofthecarispressedagainstthewhitearea),theDCmotorononesideisimmediatelystopped,andtheDCmotorontheothersideisacceleratedtorotate,sothatthecarcancorrectthedrivingdirectionandreturntothecorrectdrivingdirection(blacktrackon-line.Actually,wecanseethattheleftandrightdrivingwheelsofthecarrotateinturnandstopdrivingthecarforward;thereisaprocessofdeviation,correction,deviation,andcorrection;butitalwaysadvancesalongtheestablishedblacktrajectory.ⅥConclusionThesolartrackingcardiscussedinthisblog:Passedthetestandsuccessfullyrealizedthecarslinefollowing;Canbepoweredbysolarenergyorbattery;Strongstabilityandanti-interferenceability,highcontrolaccuracy,faststartandstop;Solvedtheproblemsofcomplicatedcontrolcircuitoflinefollowingcarandlargedeviationofdrivingtrajectory.UsingonlytheLM393voltagecomparatorasthecontrollercircuitallowsustoassembleanddebugconvenientlyandatalowercost.Theuseofnon-singlechipcontrolisafeatureofthislinefollowingcar.Figure7.LM393Insummary,thelinefollowingcarbasedonLM393controlissuitablefortechnologicalinnovationandtechnologypromotion.Afterreadingtheblog,haveyoubetterunderstandLM393?Finally,ifyouhaveanyquestionsaboutLM393,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!IDescriptionLM1875isapoweramplifierintegratedblockchip.Itssuperiorperformanceandattractivetonehavebeenacceptedbymanyenthusiasts,anditwasalltherageinthe1990s.LM1875adoptsTO-220packagestructure,whichisshapedlikeamid-powertube,smallinsize,simpleinperipheralcircuits,andlargeinoutputpower.Theintegratedcircuitintroducedinthisblogisequippedwithoverload,overheatingandinductiveloadreversepotentialsafetyprotection,whichisoneoftheidealchoicesforhigh-endaudio.Figure1.LM1875CatalogIDescriptionIILM1875ParametersIIILM1875CircuitPrincipleIVLM1875CircuitAssemblyandDebuggingVIntheEndOrdering&QuantityIILM1875ParametersVoltageRange16~60VQuiescentCurrent50MmAOutputPower25WHarmonicDistortion0.02%,whenf=1kHz,RL=8,P0=20WRatedGain26dB,whenf=1kHzWorkingVoltage25VConversionRate18V/SIIILM1875CircuitPrincipleThiscircuitiscomposedofanattenuatedtonecontrolcircuitcontrolledseparatelyforhighandlowsounds,LM1875amplifiercircuitandpowersupplycircuit.Amongthem,thesoundqualitycontrolpartusesanattenuatedtonecircuitcontrolledseparatelyforhighandlowsounds.Thespecificcomponentsareasfollows:R02,R03,C02,C01,W02formabasscontrolcircuit;C03,C04,W03formatreblecontrolcircuit;R04istheisolationresistance;W01isthevolumecontroller,whichadjuststhevolumeoftheamplifier;C05isanisolationcapacitortopreventthedownstreamLM1875DCpotentialelementfromaffectingtheprevioustonecircuit.TheamplifyingcircuitmainlyadoptsLM1875,whichiscomposedof1875,R08,R09,C066,etc.ThemagnificationofthecircuitisdeterminedbytheratioofR08toR09;C06isusedtostabilizethedriftoftheLM1875s4thpinDCzeropotential,butithasacertainimpactonthesoundquality;C07andR10functiontopreventtheamplifierfromgeneratinglow-frequencyself-excitation.InAddtion,theloadimpedanceofthisamplifieris416.Figure2.LM1875CircuitWhataboutthepowersupplycircuitofthepoweramplifier?Pleasetakealookatthepicturebelow.Inordertoensurethesoundqualityofthepoweramplifierboard,weneedtopayattentiontothefollowingwhendesigningthecircuit:Theoutputpowerofthepowertransformershallnotbelessthan80W;Theoutputvoltageis2*25V;Thefiltercapacitorusestwo4700UF/25Velectrolyticcapacitorsinparallel;Positiveandnegativepowersuppliesshare44700UF/25Vcapacitors;Thetwo104basecapacitorsarehigh-frequencyfiltercapacitors;Onlyiftheaboverequirementsaremet,theamplifiercanmaintainbettersoundquality.Figure3.LM1875CircuitIVLM1875CircuitAssemblyandDebuggingThisblogwillintroducethenecessarytoolsforcircuitassembly,howtoprepareforsoldering,andfinallyhowtodebugthecircuit.Ofcourse,ifyoustillfeellikeyouarestillcannotgetenough,intheendyoucanevenfollowourtipstotryanextrainterestingexperimentwiththiscircuit.ToolsThatYouNeedA20Welectricsolderingiron,preferablywithadjustabletemperature;Amultimeter;Apairofneedlenosepliers;Ascrewdriver;Somesolderwireandpineperfume.HowtoPrepareforWeldingWeldingsequence:①Weldingjumpers;②Weldingresistance;③Weldingcapacitor;④Weldedrectifiertube;⑤Weldingpotentiometer;⑥WeldLM1875.NotesFixtheLM1875withscrewsontheheatsinkbeforeweldingLM1875,otherwisethescrewswillbedifficulttodriveinwhentheheatsinkisinstalledattheend;ThepartofLM1875incontactwiththeheatsinkmustbecoatedwithasmallamountofheatdissipationgreasetofacilitateheatdissipation;Payattentiontotheweldingqualitywhenwelding.Forbeginners,youcanpracticeafewmoretimesontheoldcircuitboard,andthenformallysolder.HowtoDebugCorrectlyThedebuggingofthispoweramplifierboardisverysimple.Afterthecircuitboardissolderedwithelectroniccomponents,wemustcarefullycheckthecircuitboardforsolderingerrors.Specialattentionshouldbepaidtoelectronicpartswithpolarity,suchaselectrolyticcapacitorsandbridgerectifiers.Oncetheweldingisreversed,thereisariskofburningthecomponents.Whenthetransformerisconnected,theoutputterminaloftheamplifierisnotconnectedtothespeaker,butconnectedtoamultimeter(preferablydigitaldisplay,andthemultimeterissettoDC*2V).Inaddition,payattentiontothereadingofthemultimeterwhenpoweringonthepoweramplifierboard.Undernormalcircumstances,thereadingshouldbewithin30mV,otherwiseweshouldimmediatelycutoffthepowertocheckthecircuitboard.Ifthereadingoftheelectricmeteriswithinthenormalrange,itindicatesthatthefunctionofthepoweramplifierboardisbasicallynormal.Atthistime,weconnectedthespeaker,theninputthemusicsignal,andthenpoweronthetestmachine.Underthecorrectproceduresandspecifications,turnthevolumepotentiometer,thevolumeshouldchange,andturnthehighandlowknobs,thetoneofthespeakerwillchange.Figure4.LM1875ExperimentWorthTryingFirst,wewillshort-circuitC6andmeasuretheDCpotentialattheoutputofLM1875withamultimetertoseeifitiswithin30MV.Then,connectthespeakerandtestfortwohours.UseamultimetertomeasuretheDCpotentialattheoutputoftheLM1875toseeiftheDCpotentialiswithin30MV.IftheDCpotentialiswithin30MV,thecapacitorC6canbeomitted.Inthiscase,theamplifierboardbecomesapureDCpoweramplifier.VIntheEndSofar,thepoweramplifierboardhasbeensuccessfullyinstalledandadjusted.Lookingatthispieceofworkthatyoucanbeproudofandenjoyingthewonderfulmusic,areyousatisfied?IDescriptionThisblogintroducesthedesignofalithiumbatterybackuppowercontrolboardbasedonLM393,whichissimple,stable,reliable,andlow-cost.Itcandirectlyoutputthemainsvoltagewhenthereismainspower,andcontinuouslymonitorthemainsvoltage.Notonlycanthisdesignautomaticallyturnontheinverterwithin10msafterthemainspowerisoff,butitalsohasapowermanagementfunction:whentheinternallithiumbatteryvoltageislowerthanthesetvalue,itwillautomaticallycharge.ThisVediointroducesHowDoesLM393WorksCatalogIDescriptionIIDesignandWorkingPrinciple2.1Design2.2WorkingPrincipleIIITestIVConclsionOrdering&QuantityIIDesignandWorkingPrincipleThedetailsofLM393basedlithiumbatterybackupcircuitareasfollows:2.1Design2.1.1MainsPowerFailureWhenthereisnomainspowerinput,thecontrolpanelwillturnontheinverterandoutput220VACwithin10msofthemainspowerfailure.2.1.2ChargingManagementFigure1.FunctionDiagramWhenthereismainsinput,thecontrolboardfirstshutsdowntheinverteroutputandswitchestothemainsoutput;thenentersthechargingmanagementstate(duetothefeatureofthelithiumbatteryprotectionboard,theprotectionboardstopschargingafteroverchargeprotection.WhenthebatteryvoltageWhenitdropstotheoverchargerecoveryvalueorbelow,itwillautomaticallyresumecharging.Whenthereismainsinputforalongtime,thelithiumbatterychargerwillberepeatedlycharged,whichwillaffectthelifeofthelithiumbattery).Whenthelithiumbatteryisfullycharged,itwillstopcharging.Whenitdropstoacertainlevel(thisparameterislowerthantheoverchargerecoveryvalueofthelithiumbatteryprotectionboard,thespecificparametervalueisadjustable)andthenresumecharginguntilitisfullycharged,andrepeattheaboveprocess.2.2WorkingPrincipleAccordingtothedesignrequirements,theprincipledesignofthiscontrolboardisdividedintotwoparts:lithiumbatteryvoltagedetectionandcontrol,andmainsvoltagedetectionandcontrol.ThemainvoltagecomparisonpartofthecontrolboardusesthedualvoltagecomparatorintegratedchipLM393.LM393integrates2independentcomparators,itsoperatingpowersupplyvoltagerangeiswide,itcanworkfor2~36Vwhensinglepowerinput,and1~18Vwhendualpowerinput.Inaddition,itscurrentconsumptionissmall,only0.8mA.AndwhatisthepinoutofLM393?WecantakealookatFigure2below:Pins3,5arethenon-invertinginputterminalsofthetwocomparatorsrespectively;Pins2,6aretheinvertinginputterminalsofthetwocomparatorsrespectively;Pins1,7arethecorrespondingoutputterminalsofthetwocomparatorsrespectively.Figure2.LM393PinoutWhenusedasabasiccomparisoncircuit,ifthevoltageatthenon-invertinginputterminalisgreaterthanthevoltageattheinvertinginputterminal,thecorrespondingoutputterminaloutputsahighlevel,andviceversa.Forexample,whenU5U6,U7outputshighlevel;whenU5U6,U7outputslowlevel.2.2.1LithiumBatteryVoltageDetectionandControlLithiumbatteryvoltagedetectioncontrolisshowninFigure3.(1)PowerSupplyThepowersupplyofthecontrolpartistakenfromthelithiumbatteryofthebackuppowersupply,andthevoltageofthecontrolboardis12VDC.Becausethelithiumbatteryinthisdesignis48V,itsvoltagerangeis32Vto54.6V,whichishigherthanthelargeinputvoltagerequiredbythestabilizerblock7812.Therefore,inordertoprotectthevoltageregulatorblock7812,weneedtoconnecta20Vvoltageregulatortubeinseriesattheinputtostepdown.Here,diodeD5actsasreversevoltageprotection(2)VoltageComparisonThepowermanagementadoptsthecomparatorLM393,thesamplingvoltageofthelithiumbatteryisdividedbyresistorsR11andR12,andtheninputtothenon-invertinginputofLM393.Thereferencevoltagedivides12VthroughtheresistorR4andthepotentiometer,andthenenterstheinvertinginputofLM393.WhenthesamplingvoltageU1ishigherthanthereferencevoltageU2,theoutputterminalcorrespondingtoLM393outputsahighlevel,thetransistor9012isturnedoff,therelaydoesnotoperate,andtheinverterstopsworking.WhenthesamplingvoltageU1islowerthanthereferencevoltageU2,theoutputterminalcorrespondingtoLM393outputsalowlevel,thetransistor9012isturnedon,therelayacts,andtheinverteristurnedon.ThereferencevoltagecanbeadjustedaccordingtotheactualparametersthroughthepotentiometerR5.Figure3.LM393LithiumBatteryVoltageDetectionandControl(3)HysteresisComparatorCircuitInasingle-limitcomparator,iftheinputsignalUinhasaslightinterferencenearthethreshold,theoutputvoltagewillproducecorrespondingjitter(fluctuation).Forexample,inthedesignoflithiumbatteryvoltagedetection,ifthesamplingvoltageofthelithiumbatteryfluctuatesnearthetargetvoltage(seeFigure3),thevoltageofU1ishigherthanthevoltageofU2,andtheoutputofthecomparatorshouldoutputahighlevel.However,iftheU1voltageorU2voltagefluctuatesslightlyatthistime,thetransistor9012islikelytobeturnedonandofffrequentlyatthistime,andthecontroloutputwillbeveryunstable.Thenhowtoovercomethisshortcoming?Wecanintroducepositivefeedbackinthedesign(thatis,thewayofhardwaretoachievereturndifference).Ifweneedtofixatrippointatacertainreferencevoltagevalue,wecaninsertanon-linearelement(suchasacrystaldiode)inthepositivefeedbackcircuit.Byusingtheunidirectionalconductivityofthediode(inFigure2,D10diode1N4148),theaboverequirementscanbeachieved.2.2.2MainsVoltageDetectionandControlThedescriptionofthemainsvoltagedetectioncontrolpartisshowninFigure4.(1)PowerSupplyPartThepowersupplypartusesthesamepowersupplyDC12Vasthelithiumbatteryvoltagedetectionandcontrolpart.(2)MainsVoltageDetectionTakingintoaccountthecostofthemainsvoltagedetectionpart,thisdesignabandonsthetraditionaltransformerorvoltagetransformerdetectionmethod,andusestwooptocouplerchipsPC817todetectthemains.PC817isacommonlyusedlinearoptocoupler,whichisoftenusedinfunctionalcircuitsthatrequiremoreprecision.Whenanelectricalsignalisappliedtotheinputend,thelightemitteremitslightandilluminatesthelightreceiver.Thelightreceiveristurnedonafterreceivingthelight,andgeneratesaphotocurrentoutputfromtheoutputend,thusrealizingtheelectricity-optical-electricityconversion.Thisconversionisoftenappliedtovariouscivilindustrialproductssuchasswitchingpowersupplies,UPS,adapters,etc.Figure4.LM393MainsVoltageDetectionandControlTakeAC220Vasanexample.Inordertoprotecttheoptocoupler,weusea1Mresistorinthedesigntolimitthecurrentoftheoptocoupleremitter.TheoptocouplerchipsU1andU2arerespectivelyturnedonundertheactionofalternatingcurrent,andcooperatewiththecapacitorC6toensurethatthevoltageofthenon-invertinginputterminalU3isgreaterthantheinvertinginputterminalU4undertheconditionofnormalmainsinput.Theoptocouplerchipusedinthisdesigncanalsobeusedforelectricalisolationbetweenthecontrolboardandthemains.Whenthereismainspower:LM393snon-invertinginputterminalU3voltageisDC12VInvertinginputterminalU4voltageis9V(R2,R10dividedvoltage)ThecorrespondingoutputterminalishighThetransistor9014isturnedonTherelayoperatesThenormallyclosedpointisopenThereisoutputbetweenmainsvoltageWhenthereisnomainspower:Thevoltageatthenon-invertinginputterminalU3ofLM393isDC0VThevoltageattheinvertinginputterminalU4is9VThecorrespondingoutputterminalislowlevelThetransistor9014iscutoffTherelaydoesnotoperateThenormallyclosedpointisclosedTheinverteroutputs220V.IIITestAftertesting,thiscontrolcircuitmeetsthedesignrequirements:whenthereismainspowersupply,itoutputsmainsvoltage,andautomaticallyconvertstobackuppowersupplywithin10msinthecaseofmainspowerfailure,andhasgoodchargingmanagementfunctions,asshowninFigure5andFigure6.Figure5.LithiumBatteryVoltageDetectionWaveformFigure6.MainsVoltageDetectionWaveformInpracticalapplications,MOStubesandtriacscanalsobeusedtoreplacetherelaysinthevoltagedetectionandcontrolpartofthelithiumbatteryandtherelaysinthemainsvoltagedetectionandcontrolparttoachievethecontroloutput.IVConclsionThiscontrolboardisdesignedaccordingtothecharacteristicsofthelithiumbatterybackuppowersupplythatisgraduallypopularizedatpresent.Ithastheadvantagesofstronganti-interferenceandlowcost,andhasstrongmarketpromotionvalue.Insubsequentdesigns,wecanalsoaddprotectionfunctionssuchasbatteryunder-voltageprotection,short-circuitprotection,overloadprotection,over-voltageprotection,andover-temperatureprotectionaccordingtouserrequirementstocontinuouslyimprovetheproduct.Afterreadingtheblog,haveyoubetterunderstandLM393?Finally,ifyouhaveanyquestionsaboutLM393,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!

TPS73701

IntroductionInordertosolvetheproblemoftransientdistortion,thetypicalapplicationcircuitofLM3886poweramplifierischangedtothecurrentnegativefeedbacktype.Thecurrentsampleflowingthroughthespeakervoicecoilisfedbacktothepoweramplifierinputterminalviaresistance,andtheloudspeakersystemisalsoincludedinthefeedbacksystem.CatalogIntroductionCatalogITypicalpoweramplifiercircuitIIImprovedPowerAmplifierCircuitOrdering&QuantityITypicalpoweramplifiercircuitThepoweramplifiercircuitmadeofLM3886consistsoftwoparts:pre-amplifierandpoweramplifier.ThepreamplifierconsistsofanintegratedoperationalamplifierNE5534,whichprovidesavoltagegainofabout5times.ThepoweramplifieriscomposedofLM3886,whichprovidesavoltagegainofabout10times.Therefore,thefullpoweroutputcanbeachievedbyinputtingabout0.5Vsignalattheinputend.Figure1onlyshowstheLM3886dualpowersupplycircuit,whichcanalsoworkinasinglepowersupply.Consideringfromtheaspectofsoundquality,theaudioamplifiercircuitgenerallydoesnotusesinglepowersupply,butdualpowersupply.Figure1.typicalpoweramplifiercircuitThetypicalapplicationcircuitofLM3886adoptsthetraditionalnegativevoltagefeedbackmode.Negativevoltagefeedbackcanimprovethefrequencycharacteristicsofpoweramplifierandreducenonlineardistortion,butthesoundislackofstrength.Asthevolumeincreases,thelowfrequencywillbecometight,dryandhard,andthedistortionwillincrease.Atthesametime,thehighfrequencybecomessharpandharsh,andthemusicanditsdefinitionaregreatlyreduced.Thisistheso-calledTransientIntermodulationDistortion.Thetransientintermodulationdistortionismainlycausedbytheintroductionofdeepnegativefeedback.Voltagetypenegativefeedbackiseffectivetoimprovethenonlineardistortionofpoweramplifier,butitcannottakeintoaccountthetransientdistortionatthesametime.IIImprovedPowerAmplifierCircuitTheimprovedcircuitisshowninFigure2.Thelow-frequencyspectralgainofpoweramplifierisdeterminedbytheratioofR3andR4.C3andR5determinethehigh-frequencygainofpoweramplifier.DuetothelargecapacitancereactanceofC3atlowfrequency,thecurrentfeedbackisterminatedatlowfrequency,whilethehighfrequencyisimprovedbycurrentnegativefeedback.Theresultisthatthetotalbandwidthisimprovedandthetransientdistortionisgreatlyreduced.Theselectionoffeedbackcomponentsshouldbebasedontheimpedanceandinductanceoftheloudspeaker,sothatthelow-frequencygainis2-3timesofthehigh-frequencygain.Formerpoweramplifiersoftendesignedthefrequencycharacteristicstobeflat,whichdidnotachievegoodsoundeffects.Inordertoimprovethesoundeffectofthepoweramplifier,weshouldusethenegativefeedbackcircuittoconsciouslyincreasethelowfrequencygaintoachievethebesteffect,whichalsomeetstherequirementsofthelargedynamicsoundeffectoftodayshometheater.Figure2.schematicdiagramofpoweramplifiercircuitThesoundeffectofthismachineisexcellent.Thelowfrequencyextensionisincreasedanditisflexible.Thehighfrequencyisclearandsmooth.Theresolutionisgreatlyimproved,andthemetallicsoundiscompletelydisappeared.Evenifthevolumewasdoubled,nosignificantdistortionwasheard.DescriptionLM3886isahigh-performanceaudiopoweramplifier.Undertheratedworkingvoltage,itiscapableofdelivering68Wofcontinuousaveragepowertoa4loadand38Winto8with0.1%THD+Nfrom20Hz20kHz.TheperformanceoftheLM3886,utilizingitsSelfPeakInstantaneousTemperature(Ke)(SPiKe)protectioncircuitry,putsitinaclassabovediscreteandhybridamplifiersbyprovidinganinherently,dynamicallyprotectedSafeOperatingArea(SOA).SPiKeprotectionmeansthatthesepartsarecompletelysafeguardedattheoutputagainstovervoltage,undervoltage,overloads,includingshortstothesupplies,thermalrunaway,andinstantaneoustemperaturepeaks.TheLM3886maintainsanexcellentsignal-to-noiseratioofgreaterthan92dBwithatypicallownoisefloorof2.0V.ItexhibitsextremelylowTHD+Nvaluesof0.03%attheratedoutputintotheratedloadovertheaudiospectrum,andprovidesexcellentlinearitywithanIMD(SMPTE)typicalratingof0.004%.CatalogDescriptionCADModelsFeaturesApplicationsParametersElectricalCharacteristicsPinoutCircuitDiagramPackageProductComplianceComponentDatasheetProductManufacturerOrdering&QuantityCADModelsLM3886SymbolLM3886FootprintFeatures68WCont.Avg.OutputPowerinto4atVCC=28V38WCont.Avg.OutputPowerinto8atVCC=28V50WCont.Avg.OutputPowerinto8atVCC=35V135WInstantaneousPeakOutputPowerCapabilitySignal-to-NoiseRatio92dBAnInputMuteFunctionOutputProtectionfromaShorttoGroundortotheSuppliesviaInternalCurrentLimitingCircuitryOutputOver-VoltageProtectionagainstTransientsfromInductiveLoadsSupplyUnder-VoltageProtection,notAllowingInternalBiasingtoOccurwhen|VEE|+|VCC|12V,thusEliminatingTurn-OnandTurn-OffTransients11-LeadTO-220PackageWideSupplyRange20V-94VApplicationsComponentstereoCompactstereoSelf-poweredspeakersSurround-soundamplifiersHifg-endstereoTVsParametersAudioinputtypeAnalogInputArchitectureClass-ABSpeakerchannels(Max)MonoPowerstagesupply(Max)(V)94Powerstagesupply(Min)(V)20Load(Min)(ohms)4Outputpower(W)68SNR(dB)110THD+N@1kHz(%)0.03Iq(Typ)(mA)50ControlinterfaceHardwareClosed/openloopOpenAnalogsupply(Min)(V)20Analogsupply(Max)(V)84Powertoparallelbridgetiedload(Max)(W)68PSRR(dB)120Operatingtemperaturerange(C)0to70NumberofTerminals11NumberofFunctions1BrandNameTexasInstrumentsElectricalCharacteristicsThefollowingspecificationsapplyforV+=+28V,V-=-28V,lMUTE=-o.5mAwithRL=4unlessotherwisespecified.LimitsapplyforTA=25℃.PinoutPin1isthepositivepowersupplyV+terminal;Pin2isanemptypin(NC);Pin3istheoutputterminalaftersignalamplification;Pin4isthenegativepowerV-terminal;Pin5isanemptypin(NC)(internallyindependent,butinthe150WLM3886,thispinshouldbeconnectedtoV+);Pin6isanemptypin(NC);Pin7istheground(GND)terminal;Pin8isthemuteend.Ifitisnotneeded,itshouldbeconnectedtothev-terminal.Pin9istheinvertinginputofthesignal;Pin10isthenon-invertinginputterminalofthesignal;Pin11isanemptypin(NC)CircuitDiagramPackageLM3886hastwopackagingmethods.Oneisthatthebackplateisnotinsulatedfromtheinnerelectrode,anditmustbeinsulatedwhenaheatsinkisadded.Theotheristhatthebackplateisinsulatedfromtheinternalelectrodes,sothereisnoneedtoconsiderinsulationwhenaddingaheatsink.ProductComplianceECCNEAR99USHTS8542330001ComponentDatasheetDatasheetLM3886DatasheetProductManufacturerTexasInstrumentsInc.(TI)isanAmericantechnologycompanythatdesignsandmanufacturessemiconductorsandvariousintegratedcircuits,whichitsellstoelectronicsdesignersandmanufacturersglobally.ItsheadquartersareinDallas,Texas,UnitedStates.TIisoneofthetoptensemiconductorcompaniesworldwide,basedonsalesvolume.TexasInstrumentssfocusisondevelopinganalogchipsandembeddedprocessors,whichaccountsformorethan80%oftheirrevenue.TIalsoproducesTIdigitallightprocessing(DLP)technologyandeducationtechnologyproductsincludingcalculators,microcontrollersandmulti-coreprocessors.Todate,TIhasmorethan43,000patentsworldwide.

TPS73701

IIntroductionLM1875isapoweramplifierintegratedblock.Ithasfewperipheralcircuits,largedistortion-freepower,andcanworkwithbothsingleanddualpowersupplies.Italsohasasafeworkingareaprotection(inductiveload)foroverload,overheatingandreversepotentialsuppressioninthecircuit,suitableforhigh-gradeaudiocircuits.AndLM1875isalsosuitableforaudioamplification,servoamplification,bridgeamplification,andpoweramplificationintestsystems.ThisVedioTakeLM1875asanExampletoExplaintheBridgedAudioAmplifierCatalogIIntroductionIIDCNegativeFeedbackBTLPowerAmplifierCircuitIII20WSingle-powerAmplifierCircuitIVLM1875PowerAmplifierCircuitwithHighandLowAdjustmentVCurrentFeedbackPowerAmplifierCircuitOrdering&QuantityIIDCNegativeFeedbackBTLPowerAmplifierCircuitTheLM1875amplifiercircuitissimple,wherethesoundisbeautiful,andhasthetimbreoftheamplifier.Thepoweramplifierproducedbyitcanoutputpowerupto25Wunderpositiveandnegative25Vvoltage.Inordertooutputmorepower,itcanbeconnectedtoBTLcircuit.Theoutputpowerofthefollowingcircuitexceeds60W(8ohmspeaker),whichisdesignedasacurrentnegativefeedbackcircuit,andthesoundismorebeautiful.Inaddition,themainrecommendationofthisboardistocancelC11andC21inFigure1,andaddacapacitorattheinput(changeC11here).ChangethecircuittoaDCamplifier,thesoundeffectwillbebetter.Figure1.LM1875CuircuitIII20WSingle-powerAmplifierCircuitThecircuitisshowninFigure3.ThebasicworkingprincipleoftheLM1875singlepowersupplyandthedualpowersupplyisthesame.Thedifferenceisthatwhenthesinglepowersupplyisused,R1andR2areusedforvoltagedivision,while1/2VCCistakenasthebiasvoltageandaddedtoR3topin1,makingtheoutputvoltagechangeupanddownbasedon1/2VCC.Therefore,themaximumdynamicrangecanbeobtained.Figure2.LM1875CuircuitIVLM1875PowerAmplifierCircuitwithHighandLowAdjustmentFigure3.LM1875CuircuitThecircuitaboveiscomposedofthreeparts:AnattenuatedtonecontrolcircuitcontrolledbyhighandlowsoundsAnLM1875amplifiercircuitApowersupplycircuit.Thetonepartusesattenuatingtonecircuitscontrolledbyhighandlowbassrespectively,amongwhichR02,R03,C02,C01,W02formabasscontrolcircuit;C03,C04,W03formatreblecontrolcircuit;R04istheisolationresistance,W01isthevolumecontroller,adjustingthevolumeoftheamplifier;C05istheDCblockingcapacitor,topreventtheLM1875DCpotentialofthesubsequentstagefromaffectingthetonecircuitoftheprecedingstage.TheamplifyingcircuitadoptsLM1875,R08,R09,C06.Amongthem,themagnificationofthecircuitisdeterminedbytheratioofR08andR09;andC06isusedtostabilizetheDCzeropotentialdriftofthe4thpinofLM1875,butithasacertainimpactonthesoundquality;C07,R10istopreventtheamplifierfromgeneratinglow-frequencyself-excitation.Theloadimpedanceofthisamplifieris416.Figure4.LM1875CuircuitAsforthepowersupply,inordertoensurethesoundquality,theoutputpowerofthepowertransformershouldnotbelessthan80W,andtheoutputvoltageis2*25V.Thefiltercapacitorusestwo2200F/25Velectrolyticcapacitorsinparallel,andthepositiveandnegativepowersuppliessharefour2200F/25Vcapacitors.Thetwo104monolithiccapacitorsarehigh-frequencyfiltercapacitors,whicharebeneficialtothesoundqualityoftheamplifier.VCurrentFeedbackPowerAmplifierCircuitThecurrentmodepoweramplifierhasbettersoundquality.ThecurrentmodepoweramplifiercircuitusingthepoweramplifierintegratedcircuitLM1875isshowninFigure5.Inthefigure,theresistorR3connectedinserieswiththespeakerRLhasaverysmallvalue.ThecurrentflowingthroughthespeakerflowsthroughR3,andthesamplingfeedbackvoltagegeneratedatbothendsisproportionaltotheoutputcurrent.ThevoltageformedonR3issenttothefeedbackinputoftheamplifierthroughR2toformacurrentnegativefeedback,whichincreasestheoutputimpedanceoftheamplifierandreducesthedampingcoefficient.Theso-calledRubernetworkwascancelledinthecircuit,andonlyC4wasusedastheleadcompensation.AlthoughthesettingofR2preventstheoutputfeedbackcurrentfrombeingfedback100%tothenegativeinputterminal,itpreventstheharmfuleffectsoflargefeedbackontheinputterminal;Atthesametime,thebiasofthepositiveandnegativeinputterminalsisbalanced,andtheDCoffsetoftheoutputterminaliseliminated.Figure5.LM1875CuircuitFirstsoldertwosmall0.22uFcapacitorstothepin③and⑤,andweldtheotherendsofthemtogetherasthegroundterminal.Regardingtheresistancetogrounding,allarebentandweldedatthispoint.The24Vpowercordandoutputcordaredirectlysolderedtotherelevantpins.Short-circuittheinputterminaltoground,soldera10resistortotheRLspeaker,andtestthevoltageoftheoutputterminaltogroundafterpower-on.Ifitislessthan100mVandthereisbasicallynodeviationafterhalfanhour,youcandisconnecttheinputshortcircuitandconnectthespeaker.Afterreadingtheblog,haveyoubetterunderstandLM1875?IfyouarealsointerestedindetailedintroductiontoLM1875,youmaywishtobrowserighthererightnow!Finally,ifyouhaveanyquestionsaboutLM1875,pleasedonothesitatetoleaveamessageinthecommentsectionbelow!

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!DescriptionTheTDA2822isadual-channel,single-chippoweramplifierintegratedcircuitdevelopedbyStMICROelectronics.Itiscommonlyusedasanaudioamplifierinportablecassetteplayers,cassetterecorders,andmultimediaactivespeakers.Ithasthecharacteristicsofsimplecircuit,goodsoundquality,widevoltagerangeandsoon.Itcanworkinthecircuitformofstereosoundandbridgeamplification(BTL).HowtoMakeaStereoAmplifierUsingICTDA2822?CatalogDescriptionTDA2822PinoutTDA2822CADModelTDA2822ParameterTDA2822ApplicationsTDA2822FeaturesTDA2822AdvantagesWheretouseTDA2822AmplifierICHowtouseTDA2822AmplifierTDA2822SchematicDiagramTDA2822DocumentsandMediaTDA2822EnvironmentalandExportClassificationsTDA2822CircuitOrdering&QuantityTDA2822PinoutPinNumberPinNameDescription1,3OutputProvidestheamplifiedAudiooutput5,8InvertingInput(IN-)TheInvertingPinofanamplifierisnormallygrounded6,7Non-InvertingInput(IN+)TheNon-Invertingpinisprovidedwiththeaudiosignal4Vcc-Connectedtothenegativesupplyrail2Vcc+ConnectedtoPositiveSupplyRailTDA2822CADModelTDA2822SymbolTDA2822FootprintTDA2822ParameterAudio-LoadImpedance8OhmsBaseProductNumberTDA2822BrandSTMicroelectronicsCategoryIntegratedCircuits(ICs)Linear-Amplifiers-AudioClassClass-ABDescription/FunctionHeadphone/SpeakerFactoryPackQuantity25Features-Gain39dBHeight4.59mmIb-InputBiasCurrent0.1uAInputTypeSingleLength20mmManufacturer:STMicroelectronicsMaxOutputPowerxChannels@Load3.2Wx1@8Ohm;1.7Wx2@4OhmMaximumOperatingTemperature:+150CMfrSTMicroelectronicsMinimumOperatingTemperature-40CMountingStyleThroughHoleNumberofChannels2ChannelOperatingSupplyCurrent12mAOperatingSupplyVoltage5V,9V,12VOperatingTemperature-40C~150C(TJ)OutputCurrent1500mAOutputPower3.2WOutputSignalTypeDifferential,SingleOutputType1-Channel(Mono)or2-Channel(Stereo)PackageTubePackage/Case16-DIP(0.300,7.62mm)Package/CasePDIP-16PackagingTubePartStatusObsoletePd-PowerDissipation4000mWProductAudioAmplifiersPSRR-PowerSupplyRejectionRatio40dBSeriesTDA2822SubcategoryAudioICsSupplierDevicePackage16-PowerDIPSupplyTypeSingleSupplyVoltageMax15VSupplyVoltageMin3VTHDplusNoise0.2%TypeClassABType1-ChannelMonoor2-ChannelStereoUnitWeight0.057419ozVoltageSupply3V~15VWidth7.1mmTDA2822ApplicationsAMandFMRadioamplifiersPortablemusicplayersLowPowerAudioamplifiersWienbridgeoscillatorPowerAmplifiersAudioboostersTDA2822FeaturesDualAmplifiersinoneDIP-8similarforLM368.Givepowerwattsat1W+1Wat4ohmsspeakers.Itisenough.WearehappyListeninginourcorner.Startvoltagesupplyof1.8Vto15V.Thewidealot.Saveenergywithonly6mA,Min.Thebandwidthexpansionratesat40dB120kHz.CheapandeasytouseTDA2822AdvantagesTDA2822isalowpowerstereoOpAmplifierusedinWalkmanplayersandHearingaids.Itcangive250mWoutput.TDA2822isanidealOpampforlowoutputapplications.Itisagoodchoiceasapreamplifierinstereohighpoweramplifiercircuits.Ithastwoinputsandtwooutputswhichcandeliver250milliwattsoutputpower.TheamplifiercircuitwithintheICiswellsetfornoisefreeoperation.Outputscanbedirectlycoupledtothespeakersthroughthedecouplingcapacitors.WheretouseTDA2822AmplifierICTheTDA2822isaDualAudioAmplifierIC,meaningithastwoOp-Ampsinsideitspackage,andtheyarecommonlyusedforaudioamplificationbecauseoftheirwidebandwidthgain.Thetwooutputscandeliver250milliwattsoutputpower.ThisICcanbeusedinportableaudiosystems,preamplifiers,hearingaidminiradio,headphoneamplifier,etc.SoifyouarelookingforadualpackageOperationalamplifierICwithhigh-gain,andwidebandwidthforaudioamplification,thenthisICmightbetherightchoiceforyou.HowtouseTDA2822AmplifierAnapplicationcircuitfromTDA2822datasheetisgivenbelowTheleftloadisconnectedtooutputpin1oftheICthroughelectrolyticcapacitorC4,andtherightloadisconnectedtooutputpin3throughelectrolyticcapacitorC5.TheInvertingInputPins(5and8)areconnectedtothegroundviaelectrolyticcapacitors.Non-InvertingInputPins(7and6)areconnectedtoinput1andinput2.Pin2isconnectedtoDCsupplyandpin4isconnectedtoground.ElectrolyticcapacitorC3connectedacrossVCCandground,workasafiltercapacitor.TDA2822SchematicDiagramTDA2822DocumentsandMediaDatasheetsTDA2822DesignResourcesDevelopmentToolSelectorHTMLDatasheetTDA2822TDA2822EnvironmentalandExportClassificationsAttributeDescriptionRoHSStatusROHS3CompliantMoistureSensitivityLevel(MSL)1(Unlimited)TDA2822CircuitTDA2822TestCircuit(Stereo)TDA2822TestCircuit(Bridge)TDA2822TypicalApplicationinPortablePlayersTDA2822LowCostApplicationinPortablePlayersTDA28223VStereoCassettePlayerwithMototSpeedControl

I.Description74LS138isa3-lineto8-linedecoder/demultiplexer.Thechipisdesignedtobeusedinhigh-performancememory-decodingordata-routingapplications,requiringveryshortpropagationdelaytimes.Inhighperformancememorysystemsthesedecoderscanbeusedtominimizetheeffectsofsystemdecoding.Thethreeenablepinsofchip(inwhichTwoactive-lowandoneactive-high)reducetheneedforexternalgatesorinverterswhenexpanding.CatalogI.DescriptionII.DigitalVoltmeterCircuitFAQOrdering&QuantityII.DigitalVoltmeterCircuitWeuseAD574andAT89C2051toformahighprecisiondigitalvoltmeter.TheschematicdiagramisshowninFigure1.AD574isa12-bitsuccessivecomparisonA/Dconverterwith12datalinesintotal.P1ofAT89C2051isdirectlyconnectedtothehigh8-bitdatalineofAD574.Thelow4-bitdatalineofAD574isdirectlyconnectedwiththeupperhalf4-bitp1.4-p1.7ofsingle-chipmicrocomputer.Datareadingisbasedonthecontrollineofsinglechipmicrocomputer.P3.5isconnectedtoAD574byteshortperiodcontrolline(A0).P3.4isconnectedtoreadconversiondatacontrolpin.AndP3.7isdirectlyconnectedwiththeterminalofindicatingworkingstatus(STS).Suchstructuredeterminesthatitcanonlybe8-bitoutput,sothedatamodeselectionendcanbedirectlygrounded.AT89C2051hasonly15I/Oportwires,11ofwhichareusedabove,andonly4ofthemareleft.Theoutputdataisoutputthroughtheserialportofthesingle-chipmicrocomputer,andanexternal74LS164(serialinandparallelout)decoderisconnectedforexpansion.Atthesametime,thedatadisplayedis4bits,andtheremaining2portlinesstillcannotmeettherequirements.A74LS138decoderisneededtogatetheaddressofthedisplayLED.Hereweusetheinputmodeof10Vrange.Pin13ofAD574istheinputterminalofthemeasuredvoltage.BecauseonlyoneAD574conversionchipisused,theCSterminalcanbedirectlygrounded.Theconverteruses12Vpowersupplyvoltageandtheworkingvoltageis+5V.74LS164isaserialinputandparalleloutputdecoder.TheBCDserialcodeoutputbyAT89C2051throughtheserialportisdecodedby74LS164andoutputasaseven-segmentBCDcode,whichisdirectlyconnectedtoa-goftheLED,andthedatalinesofthefourLEDsareconnectedonebyone.LEDdigitaltubeusescommonanodetype.Theaddresscodeoutputby74LS138isconnectedtothecommonterminalofLEDviaatransistor2SA1015(PNP).Thedisplayofthefour-digitLEDistime-sharingstrobethroughtheaddressline,whichisourcommonlyuseddynamicscanningdisplaymethod.Itisworthmentioningthatinthedynamicscanningdisplaymode,thefrequencyofdynamicscanninghascertainrequirements.Ifthefrequencyistoolow,theLEDwillflicker.Ifthefrequencyistoohigh,thelightingtimeofeachLEDistooshort,andthebrightnessoftheLEDistoolow.Itcantbeseenclearlywithnakedeye.Soitisgenerallyappropriatetotakeabout10ms.Thisrequiresthatwhenwritingaprogram,acertainLEDshouldbeonandkeptforacertainperiodoftime.Theprogramoftenusesthecalldelaysubroutine.FAQWhatisthedifferencebetween74hc138and74LS138?Bothhavethesamefunction.74HC138ismadeofhigh-speedCMOSprocess,withlowpowerconsumption,highoutput,lowlevelandwiderange.74LS138adoptstheearlybipolarprocess,anditsdrivingcapabilityisrelativelylarger.Whatisthefunctionaldifferencebetween74ls138decoderand74ls148?74ls138isa3-8wiredecoder/multiplexer,74ls148isan8-3wireoctalpriorityencoder.Oneisdecodingandtheotherisencoding.OppositeeffectWhatsthedifferencebetween74LS138Dand74LS138N?Thosetwoarethesamechip,DisSOPpackage,NisDIPpackage.Whataretheoutputcharacteristicsof74LS138decoder ?UnderthepremisethattheenableterminalsS1(activehigh),S2(activelow),andS3(activelow)arevalidatthesametime,onlyoneoutputterminalislowatatime(therestarehigh);Iftheenableterminalisinvalid,theoutputisallhighlevel.Whatdothelettersandnumbersin74ls138standfor?74ls138isa3-8-linedecoder.Thenumber74representsthe74seriesofthe54/74series,andthe74serieshasanoperatingtemperatureof0degreesto70degrees.LSisaseries,representingthelow-powerSchottkyseries.138isthevarietycode.Whatstheworkingprincipleof74ls138?74LS138workingprinciple①Whenonestrobeterminal(E1)ishighlevel,andtheothertwostrobeterminals(E2)and(E3)arelowlevel,attheoutputterminalscorrespondingtoY0toY7,thebinarycodeofaddressterminals(A0,A1,A2)canbedecodedatlowlevel.Forexample:whenA2A1A0=110,theY6outputterminaloutputsalow-levelsignal.②UsingE1,E2andE3,itcanbecascadedtoexpandintoa24-linedecoder;ifanexternalinverterisconnected,itcanalsobecascadedtoexpandintoa32-linedecoder.③Ifoneofthestrobeterminalsisusedasadatainputterminal,74LS138canalsobeusedasadatadistributor.④Itcanbeusedin8086decodingcircuittoexpandmemory.Introduction74LS138isa3-lineto8-linedecoder/demultiplexer.Thechipisdesignedtobeusedinhigh-performancememory-decodingordata-routingapplications,requiringveryshortpropagationdelaytimes.Inhighperformancememorysystemsthesedecoderscanbeusedtominimizetheeffectsofsystemdecoding.Thethreeenablepinsofchip(inwhichTwoactive-lowandoneactive-high)reducetheneedforexternalgatesorinverterswhenexpanding.CatalogIntroductionIFullAdderCircuitIIResponderCircuitIIILogicFunctionIVFullSubtractorCircuitVThree-inputMajorityVotingFAQOrdering&QuantityIFullAdderCircuitThefulladderhas3inputterminals:An,Bn,Cn-1;2outputterminals:Sn,Cn.The74LS1383-lineto8-linedecoderhas3datainputterminals:A,B,C;3enableterminalsand8outputterminals.Here,the3datainputterminalsofthe3-lineto8-linedecodercanberegardedasthe3inputterminalsofthefulladder.Thatis,theinputsA,B,andCofthe3-lineto8-linedecodercorrespondtotheinputsAn,Bn,andCn-1ofthefulladderrespectively.Setthe3enableterminalsofthe3-lineto8-linedecodertotheeffectiveleveltomaintainnormaloperation.Thekeypointhereistodealwiththerelationshipbetweenthe8outputterminalsofthe3-lineto8-linedecoderandthe2outputsofthefulladder.UsetheoutputOUT(1,2,4,7)ofthe3-lineto8-linedecoderasa4-inputorgateinput,andthegateoutputasthesumoftheadder.UsetheoutputOUT(3,5,6,7)ofthe3-lineto8-linedecoderasa4-inputorgateinput,thegateoutputisusedasthecarryoutputoftheadder.Whentheinputoftheadderis:a=1,b=0,ci=1,theinputofthecorresponding3-lineto8-linedecoderisA=1,B=0,C=1.Theoutputofthedecoderisout(5)=1andtherestis0.Accordingtotheconnectionrelationshipdesignedabove,S=0,CO=1,whichsatisfiesthefunctionoffulladder.Figure1.FullAdderCircuitIIResponderCircuitFigure2.ResponderCircuitIIILogicFunctionF=ABC+ABC+ABC=111+110+101=Y7+Y6+Y5Accordingtotheruleof74LS138,Aisthelowbit(LSB)andDisthehighbit(MSB).The74LS138decodingoutputislowleveleffective.With74LS10NANDgate,theactuallogicisinputlowleveleffectiveorgate.Figure3.CircuitofLogicFunctionIVFullSubtractorCircuitFigure4.FullSubtractorCircuitVThree-inputMajorityVotingThedeviceconsistsofa3-lineto8-linedecoder(74LS138)andtwo4-inputNANDgates(74LS20).Therearethreebuttonsforuser.Pressthebuttontoagree,nottopressmeanstoreject.Whennoonepressesthebutton,orwhenonlyonepersonpressesthebutton,forexample,S1ispressed,butS2andS0arenotpressed.Theredlightison,thegreenlightisoff,andthebuzzerissilent,indicatingveto.Whentwoormorepeoplepressthebutton,forexample,ifS1andS2arepressed,theredlightwillbeoff,thegreenlightwillbeon,andthebuzzerwillsoundtoindicateapass.Use74LS138decoderandfour-inputNANDgate74LS20torealizethislogicfunction.Figure5.CircuitofThree-inputMajorityVotingFAQWhatisthedifferencebetween74hc138and74LS138?Bothhavethesamefunction.74HC138ismadeofhigh-speedCMOSprocess,withlowpowerconsumption,highoutput,lowlevelandwiderange.74LS138adoptstheearlybipolarprocess,anditsdrivingcapabilityisrelativelylarger.Whatisthefunctionaldifferencebetween74ls138decoderand74ls148 ?74ls138isa3-8wiredecoder/multiplexer,74ls148isan8-3wireoctalpriorityencoder.Oneisdecodingandtheotherisencoding.OppositeeffectWhatsthedifferencebetween74LS138Dand74LS138N?Thosetwoarethesamechip,DisSOPpackage,NisDIPpackage.Whataretheoutputcharacteristicsof74LS138decoder?UnderthepremisethattheenableterminalsS1(activehigh),S2(activelow),andS3(activelow)arevalidatthesametime,onlyoneoutputterminalislowatatime(therestarehigh);Iftheenableterminalisinvalid,theoutputisallhighlevel.Whatdothelettersandnumbersin74ls138standfor?74ls138isa3-8-linedecoder.Thenumber74representsthe74seriesofthe54/74series,andthe74serieshasanoperatingtemperatureof0degreesto70degrees.LSisaseries,representingthelow-powerSchottkyseries.138isthevarietycode.Whatstheworkingprincipleof74ls138?74LS138workingprinciple①Whenonestrobeterminal(E1)ishighlevel,andtheothertwostrobeterminals(E2)and(E3)arelowlevel,attheoutputterminalscorrespondingtoY0toY7,thebinarycodeofaddressterminals(A0,A1,A2)canbedecodedatlowlevel.Forexample:whenA2A1A0=110,theY6outputterminaloutputsalow-levelsignal.②UsingE1,E2andE3,itcanbecascadedtoexpandintoa24-linedecoder;ifanexternalinverterisconnected,itcanalsobecascadedtoexpandintoa32-linedecoder.③Ifoneofthestrobeterminalsisusedasadatainputterminal,74LS138canalsobeusedasadatadistributor.④Itcanbeusedin8086decodingcircuittoexpandmemory.

Description74LS138isa3-lineto8-linedecoder/demultiplexer.Thechipisdesignedtobeusedinhigh-performancememory-decodingordata-routingapplications,requiringveryshortpropagationdelaytimes.Inhighperformancememorysystemsthesedecoderscanbeusedtominimizetheeffectsofsystemdecoding.Thethreeenablepinsofchip(inwhichTwoactive-lowandoneactive-high)reducetheneedforexternalgatesorinverterswhenexpanding.A24-linedecodercanbeimplementedwithnoexternalinverters,anda32-linedecoderrequiresonlyoneinverter.74LS138isusedinde-multiplexingapplicationsbyusingenablepinasdatainputpin.Alsothechipinputsareclampedwithhigh-performanceSchottkydiodestosuppressline-ringingandsimplifysystemdesign.CatalogDescriptionCatalogCADModelsFeaturesApplicationPinoutLogicDiagramPackageParametersProductComplianceComponentDatasheetProductManufacturerFAQOrdering&QuantityCADModels74LS138Symbol74LS138FootprintFeaturesDesignedSpecificallyforHigh-Speed:MemoryDecodersDataTransmissionSystems3EnableInputstoSimplifyCascadingand/orDataReceptionSchottky-ClampedforHighPerformanceApplicationLinedecodersServersDigitalsystemsLineDe-multiplexingTelecomcircuitsMemorycircuitsPinoutPinFunctionPinNameDescription1A0Addressinputpin2A1Addressinputpin3A2Addressinputpin4E1Enableinput(activeLOW)5E2Enableinput(activeLOW)6E3Enableinput(activeHIGH)7O7Outputpin78GNDGround9O6Outputpin610O5Outputpin511O4Outputpin412O3Outputpin313O2Outputpin214O1Outputpin115O0Outputpin016VCCPowersupplypinLogicDiagramPackageParametersFunctionDecoder,DemultiplexerTechnologyFamilyLSVCC(Min)(V)4.75VCC(Max)(V)5.25Channels(#)1Voltage(Nom)(V)5F@nomvoltage(Max)(MHz)35ICC@nomvoltage(Max)(mA)10tpd@nomVoltage(Max)(ns)41Configuration3:8ProducttypeStandardIOL(Max)(mA)8IOH(Max)(mA)-0.4RatingCatalogOperatingtemperaturerange(C)0to70Bits(#)8Digitalinputleakage(Max)(uA)5ESDCDM(kV)0.75ESDHBM(kV)2ProductComplianceECCNEAR99USHTS8542390001ComponentDatasheetDatasheet74LS138DatasheetProductManufacturerTexasInstrumentsInc.(TI)isanAmericantechnologycompanythatdesignsandmanufacturessemiconductorsandvariousintegratedcircuits,whichitsellstoelectronicsdesignersandmanufacturersglobally.ItsheadquartersareinDallas,Texas,UnitedStates.TIisoneofthetoptensemiconductorcompaniesworldwide,basedonsalesvolume.TexasInstrumentssfocusisondevelopinganalogchipsandembeddedprocessors,whichaccountsformorethan80%oftheirrevenue.TIalsoproducesTIdigitallightprocessing(DLP)technologyandeducationtechnologyproductsincludingcalculators,microcontrollersandmulti-coreprocessors.Todate,TIhasmorethan43,000patentsworldwide.FAQWhatisthedifferencebetween74hc138and74LS138?Bothhavethesamefunction.74HC138ismadeofhigh-speedCMOSprocess,withlowpowerconsumption,highoutput,lowlevelandwiderange.74LS138adoptstheearlybipolarprocess,anditsdrivingcapabilityisrelativelylarger.Whatisthefunctionaldifferencebetween74ls138decoderand74ls148?74ls138isa3-8wiredecoder/multiplexer,74ls148isan8-3wireoctalpriorityencoder.Oneisdecodingandtheotherisencoding.OppositeeffectWhatsthedifferencebetween74LS138Dand74LS138N ?Thosetwoarethesamechip,DisSOPpackage,NisDIPpackage.Whataretheoutputcharacteristicsof74LS138decoder?UnderthepremisethattheenableterminalsS1(activehigh),S2(activelow),andS3(activelow)arevalidatthesametime,onlyoneoutputterminalislowatatime(therestarehigh);Iftheenableterminalisinvalid,theoutputisallhighlevel.Whatdothelettersandnumbersin74ls138standfor?74ls138isa3-8-linedecoder.Thenumber74representsthe74seriesofthe54/74series,andthe74serieshasanoperatingtemperatureof0degreesto70degrees.LSisaseries,representingthelow-powerSchottkyseries.138isthevarietycode.Whatstheworkingprincipleof74ls138?74LS138workingprinciple①Whenonestrobeterminal(E1)ishighlevel,andtheothertwostrobeterminals(E2)and(E3)arelowlevel,attheoutputterminalscorrespondingtoY0toY7,thebinarycodeofaddressterminals(A0,A1,A2)canbedecodedatlowlevel.Forexample:whenA2A1A0=110,theY6outputterminaloutputsalow-levelsignal.②UsingE1,E2andE3,itcanbecascadedtoexpandintoa24-linedecoder;ifanexternalinverterisconnected,itcanalsobecascadedtoexpandintoa32-linedecoder.③Ifoneofthestrobeterminalsisusedasadatainputterminal,74LS138canalsobeusedasadatadistributor.④Itcanbeusedin8086decodingcircuittoexpandmemory.I.IntroductionTheheartrateisakeyindicatorvaluereflectingthehealthofthebody.Simplyput,theheartratereferstothefrequencyofcardiovascularbeatswithin1minute.Thetestofheartratecanshowscientificevidenceinworksuchasdiseasediagnosis,patientcare,andathletetraining.Inrecentyears,manymedicalequipmentandfitnessequipmentdevelopedandmanufacturedbycountriesaroundtheworldhaveadoptedheartratetestpowercircuits.Thelowcostofproductdevelopmentandhighperformanceheartratetestpowercircuitshaveimportantapplicationvalues.ThearticleintroducesthiskindofheartbeatratedetectionsystembasedonAD620integratedICindetail.Usingtheexcellentlow-noisecharacteristicsofAD620integratedIC,pluseffectivefilteringandamplifyingcircuits,combinedwithmicroprocessorsolutions,ahigh-precisionheartratemonitoringsystemisobtained.Figure1AD620CatalogI.IntroductionII.AD620ChipIII.CircuitDesign3.1BlockDiagram3.2SignalExtractionCircuitBasedonAD6203.3FilterAmplifierCircuit3.4MicroprocessorCircuit3.5ExperimentalResultsandDiscussionIV.ConclusionFAQOrdering&QuantityII.AD620chipAD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyneedsanexternalresistortosetthegain,andthegainrangeis1to10000.Inaddition,AD620adopts8-pinSOICandDIPpackage,thesizeissmallerthanthediscretecircuitdesign,andthepowerconsumptionislower,soitisverysuitableforbattery-poweredandportableapplications.Itscharacteristicsareasfollows:EASYTOUSEGainSetwithOneExternalResistor(GainRange1to10,000)WidePowerSupplyRange(2.3Vto18V)HigherPerformancethanThreeOpAmpIADesignsAvailablein8-LeadDIPandSOICPackagingLowPower,1.3mAmaxSupplyLOWNOISE9nV/Hz,@1kHz,InputVoltageNoise0.28Vp-pNoise(0.1Hzto10Hz)EXCELLENTDCPERFORMANCE(BGRADE)50Vmax,InputOffsetVoltage0.6V/Cmax,InputOffsetDrift1.0nAmax,InputBiasCurrent100dBminCommon-ModeRejectionRatio(G=10)EXCELLENTACSPECIFICATIONS120kHzBandwidth(G=100)15sSettlingTimeto0.01%III.CircuitDesign3.1BlockDiagramThesurfaceofthehumanskincontainshumanECG,EMG,andpowerfrequencysignals.Generally,thenoiseoftheECGsignalcontainingheartrateinformationismuchsmallerthanthatofthepowerfrequencysignal.InordertoextracttheweakECGsignal,alow-noiseoperationalamplifiermustbeusedandareasonablefilteramplifiercircuitmustbedesigned.Figure2isablockdiagramoftheheartratedetectionsystem.Thewholeheartratedetectionsystemconsistsoffourparts:thesensorheadincontactwiththehumanskinsurface,thesignalextractioncircuit,thefilteramplifiercircuitandthemicroprocessorcircuit.Thesensorheadisgenerallyametalthatiseasytoconductelectricity.Aftercontactingthesurfaceofthehumanskin,ithascomplexelectricalsignalssuchashumanECGsignals,electromyographicsignals,andpowerfrequencysignals.Weusethelow-noiseAD620operationalamplifierasthecorechipoftheheartbeatrateextractioncircuit.Inthefilteringandamplifyingcircuitpart,asimplelow-passfilteringcircuitisused.Theexperimentalresultsshowthatthisfilteringcircuitissufficienttoextracttheheartratesignal.Afterfilteringtheamplifiedsignal,anadjustablecomparatorcombinedwithatransistorcircuitisusedtoforma5voltTTLlevelsignal,andfinallyconnectedtothemicroprocessor,theheartbeatsignalisprocessedbythemicrocomputer,andtheheartbeatrateiscalculatedanddisplayed.Figure2Blockdiagramofheartratedetectionprinciple3.2SignalExtractionCircuitBasedonAD620AD620operationalamplifier,usuallyusedinhigh-precisiontestinstruments,themaximumnonlinearerrorof40ppm,themaximumvoltageoffsetof50uV,themaximumtemperaturedriftof0.6uV/℃,becauseofitslownoise,lowbiascurrent,lowpowerconsumptioncharacteristics,itItiswidelyusedinmedicalfieldssuchaselectrocardiogram(ECG)andbloodpressuremonitoring.Figure3isasignalextractioncircuitbasedonAD620,inwhichtheLEFT_ARM,RIGHT_ARM,LEGthreeleadsareconnectedtothealuminumsheet(iethesensorhead),whicharerespectivelyconnectedtotheleftandrighthandsandrightfeetofthehumanbody.OurexperimentalresearchresultsshowthattheR4gainofLEFT_ARMis1K,thecorrespondingAD620operationalamplifiergainis50.Toomuchgainwillweakenthefinalsignal-to-noiseratio,sotheR4resistancevalueshouldbesetreasonablyintheexperiment.The0.1uFcapacitancebetweentheLEFT_ARMandRIGHT_ARMleadsistoeffectivelyweakenthepowerfrequencynoise.TheLEGleadisconnectedtoAD620throughTL082A,whichprovidesthereferencepotentialofthehumanbodyforthedifferentialsignalofLEFT_ARMandRIGHT_ARM.Figure3SignalextractioncircuitbasedonAD6203.3FilterAmplifierCircuitFigure4isafilteramplifiercircuit.Threeoperationalamplifiersconstituteathree-stageamplification,eachamplifying100times.Duetocircuitloss,especiallythelossoftheisolationcapacitor,theactualsignalamplificationislessthan1milliontimes.TheratiooftheresistancevaluesofR6andR5,R9andR8,R11andR10inthecircuitdeterminesthemagnificationfactor,andtheseresistancevaluesshouldbeadjustedreasonablyinpracticalapplications.Alow-passfiltercircuitshouldbeusedwhileamplifyingthesignaltoachievetheeffectoffilteringpowerfrequencynoise.Sincethefrequencyofthepowerfrequencynoiseis50Hz,thedesignedfiltercircuithasapassbandbandwidthoflessthan50Hz,thatis,theRCtimeconstantofthecapacitorresistormustbeofthesameorderofmagnitudeasthepowerfrequencysignalperiod.R7andC10inthecircuitformalow-passfilter.Weuse1uFcapacitorisolationbetweenlevelsofamplification.Thesecapacitorswillattenuatethesignalatthesametime,andthethreeoperationalamplifiersareselectedforsignalamplification,sothesignal-to-noiseratioisimproved.Itshouldbepointedoutthatiftheisolationcapacitoristoolarge,itiseasytocausetheoutputelectricalsignaltodrift.Figure4FilteramplifiercircuitFigure5istheshapingcircuit.Theheartbeatratesignalandsignal-to-noiseratioofthe2ND_OUTleadarelargeenough(thepulserateoftheheartbeatrateis1~5V),afterthehalf-waveshapingofD1,thentheadjustablecomparator,andfinallythetransistorQ1isconvertedtothemicrocontrollerlevel.Figure5Shapingcircuit3.4MicroprocessorCircuitThefinalsignalisprocessedbyAT89C51,andtheheartrateisdisplayedbyLEDdigitaltube.ThemicroprocessorcircuitwithAT89C51asthecoreisverymature,soitsnoneedtorepeathere.3.5ExperimentalResultsandDiscussionFigure6showstheactualmeasurementresultsofthehumanheartrateusingtheabovesystem.Figure6(a)isthevoltagesignalafterthesignal2ND_OUTisshapedbyD1.ItcanbeseenfromthefigurethatthisisactuallyacompleteECGsignal.Inacycleofsignals,therearetwomoreobviouspulsesignals.Thispulsecharacteristicvariesfrompersontoperson.ItisfoundthatthereisatleastonepulsesignalthroughactualmeasurementoftheECGsignalsofdifferentpeople.Figure6(b)showstheelectricalsignalofHEART_PULSE,whichisobtainedafterthesignalofFigure6(a)passesthroughthecomparatorandthetransistorswitch.Thesignalcanbedirectlyinputtotheportofthemicroprocessor,andthemicroprocessorcalculatesandoutputstheheartrate.Figure6HeartratesignaldiagramWhendevelopingtheabove-mentionedheartratedetectionsystem,thereareseveralkeypointstopayspecialattentionto:(1)ConnectingcapacitorstoLEFT_ARMandRIGHT_ARMcangreatlyimprovethesignal-to-noiseratio;themainenergyoftheheartratesignalonLEFT_ARMandRIGHT_ARMisatafrequencyofabout1Hz,andthecapacitorisalow-passfilterthatcanfilterandsuppressnoise;Choosealargecapacitortoeliminatehigh-frequencynoise.Intheexperiment,a10uFnon-polarcapacitorisused,andtheeffectisverygood;(2)Thelow-passfiltercircuiteffectivelyweakensthepowerfrequencysignalandimprovesthesignal-to-noiseratio;itadoptsacombinationofactivefilteringandpassivefilteringtofilterwhileamplifying,whichhasabettereffectthanfilteringafteramplification;(3)Capacitorisolationattenuationandmulti-stageamplificationarebeneficialtoimprovethesignal-to-noiseratio;themainnoiseis50Hzpowerfrequencysignals.Althoughthemulti-stageamplificationandfilteringincreasethermalnoise,ithasgreatsuppressionofpowerfrequencynoise.Ofcourse,thenumberofamplificationstagescannotbeinfinite,andthebestnumberofstagesistheminimumsumofpowerfrequencynoiseandthermalnoise;(4)SmallcapacitorisolationshouldbeusedtosuppressDCsignaldrift.Thisisshownbytheexperimentalresults,andthereasonneedstobefurtherstudied.IV.ConclusionThisarticlediscussesaschemebasedonAD620chipheartratedetection,andintroducesthecircuitdesignofthesensorhead,signalextraction,filteramplificationandmicroprocessorthatmakeupthesystem.Givesthemethodtoimprovethesystemperformance.ExperimentsshowthatthesystemcanobtainbetterECGsignalsandaccurateheartrate.Theheartbeatratedetectionsysteminthisarticlehasstronganti-interferenceability,simplestructureandlowcost.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

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