Tkool Electronics

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.

293D476X96R3B2TE3-VISHAY

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.

DescriptionLED,asthefirstbasicfunctiontobecompletedinMCUlearning,playsaveryimportantroleinMCUlearners,whichalsocalledmagiclampbyMCUlearners.IbelievethateveryoneseesmostandthesimplestLEDcircuitisthefigureshownbelow.Asshowninthefigure,notonlythecircuitissimple,butalsoitsoperationisverysimple.GiveselectricalleveltoI/OcorrespondingtoeightLEDs,andthecorrespondingLEDcanbeonoroff.Figure1.simpleLEDcircuitCatalogDescription74HC595Drives8BitsLEDSFAQOrdering&Quantity74HC595Drives8BitsLEDSButnotallLEDcircuitsaresosimple.Somecircuitswilluse74HC595chiptodrive8LEDsordrivethe8-bitdigitaltubesegmentcode,asshowninthefigurebelow.Figure2.74HC595drives8LEDsWhyisasimplecircuitsocomplicated?Thereasonisobvious.BeforetheeightLEDneedeightI/O,nowonlythreeI/OcandriveeightLED.Letsbrieflyintroduce74CH595anduseitsuccessfullytodriveeightLEDlights.The74HC595isan8-bitserial-inorparallel-outshiftregisterwithastorageregisterand3-stateoutputs.Boththeshiftandstorageregisterhaveseparateclocks.Thedevicefeaturesaserialinput(DS)andaserialoutput(Q7S)toenablecascadingandanasynchronousresetMRinput.SIisitsserialdatainput.Q0toQ7aredataoutput.SCK,istheclockfortheshiftregister.The595isclock-drivenontherisingedge.Thismeansthatinordertoshiftbitsintotheshiftregister,theclockmustbeHIGH.Andbitsaretransferredinontherisingedgeoftheclock.RCK,isaveryimportantpin.WhendrivenHIGH,thecontentsofShiftRegisterarecopiedintotheStorage/LatchRegister;whichultimatelyshowsupattheoutput.Sothelatchpincanbeseenaslikethefinalstepintheprocesstoseeingourresultsattheoutput.SQHisserialdataoutput.Whatwewanttoachievenowistomovethe8-bitsdataofSIinto74HC595onebyoneundertheactionofSCKandRCKandpresenttheminparallelonQ0-Q7.Figure3.How74HC595ShiftRegisterworksWheneverweapplyaclockpulsetoa595,thebitsintheShiftRegistermoveonesteptotheleft.Belowisitscode.FAQWhatis74HC595?74HC595isashiftregisterwhichworksonSerialINParallelOUTprotocol.Itreceivesdataseriallyfromthemicrocontrollerandthensendsoutthisdatathroughparallelpins.Wecanincreaseouroutputpinsby8usingthesinglechip.Whatisa74hc595n?8-bitShiftRegister74HC595NAshiftregisterisachipyoucanusetocontrolmanyoutputs(8here)atthesametimewhileonlyusingafewpins(3here)ofyourArduino.Howdoesashiftregisterwork?Shiftregistersholdthedataintheirmemorywhichismovedorshiftedtotheirrequiredpositionsoneachclockpulse.Eachclockpulseshiftsthecontentsoftheregisteronebitpositiontoeithertheleftortheright.How74HC595ShiftRegiesterworks?The595hastworegisters(whichcanbethoughtofasmemorycontainers),eachwithjust8bitsofdata.ThefirstoneiscalledtheShiftRegister.TheShiftRegisterliesdeepwithintheICcircuits,quietlyacceptinginput.Howdoesan8bitshiftregisterwork?TheSN74HC595Nisasimple8-bitshiftregisterIC.Simplyput,thisshiftregisterisadevicethatallowsadditionalinputsoroutputstobeaddedtoamicrocontrollerbyconvertingdatabetweenparallelandserialformats.YourchosenmicroprocessorisabletocommunicatewiththeTheSN74HC595Nusingserialinformationthengathersoroutputsinformationinaparallel(multi-pin)format.Essentiallyittakes8bitsfromtheserialinputandthenoutputsthemto8pins.Whatisadigitaltube?Lightemittingdiodeconnectstheanodetogetherandthenconnectedtothepowerofpositiveiscalledcommonanodedigitaltube,lightemittingdiodeconnectedtothecathodeandthenconnectedtothepowerofthecathodeiscalledcommoncathodedigitaltube.Whatisthedifferencebetweenshiftregisterandcounter?Inashiftregister,theinputofelementNistheoutputofelementN-1,andallelementsusethesameclock.Inacounter,theinputofelementNistheinverseofitsoutput,andtheclockofelementN+1istheoutputofelementN.IDescriptionDoyouknowwhattheDigitalTubeDisplayneeds?Thedisplayofthedigitaltuberequiresadigitaltubeandacontrolcircuitofmultipledigitaltubes.Takethesingle-chipmicrocomputercontrolcircuitofan8-bitdigitaltubeasanexample.Thesingle-chipmicrocomputerneedstoprovidean8-bitsegmentcodeandan8-bitcode.Thus,weusuallychoosetwoofthefourparallelI/Oportsinthe51single-chipmicrocomputertoprovidesegmentcodesandbitcodesrespectively.Althoughthiscircuithardwareconnectionandsoftwareprogrammingarerelativelysimple,therearealsoproblems.Thatis:ToomanyI/Oportsareoccupied,whichaffectstheoveralluseofthemicrocontroller,andisnotconducivetotheaccessofotherdevices.Howtosolvethisproblem?Wecanuseatypeofshiftregisterforauxiliarycontrol.Here,thisblogusesthe74HC595chip.Figure1.74HC595CatalogIDescriptionIIIntroductionto74HC595III74HC595DisplayControlofMulti-digitDigitalTube3.1HardwareConnection3.2SoftwareProgramming3.3SimulationDebuggingIVConclusionFAQOrdering&QuantityIIIntroductionto74HC59574HC595isaCMOSshiftregisterwithopen-drainoutput.Theoutputportisacontrollablethree-stateoutput.Itcanalsocontrolthenext-levelcascadedchipserially.Itsstructureisusuallya16-pinDIPpackageorSOpackage.The74HC595pinoutisshowninFigure2,andthecorrespondingpinfunctionsareshowninTable1.Figure2.74HC595PinoutThemainfeaturesof74HC595are:8-bitserialinput/8-bitparallelorserialoutput;Three-stateoutputregister(three-stateoutput:agatecircuitwiththreeoutputstatesofhighlevel,lowlevelandhighimpedance);High-speedlow-powerconsumption,high-speedshiftclockfrequencyFmax25MHz.Table1.74HC595PinFunctionPinNumberPinNamePinFunction15,1~7Q0~Q7Paralleltri-stateoutputpin8GNDPowerground9Q7Serialdataoutputpin10/MRClearendofshiftregister(activelow)11SH_CPSerialdatainputclockline12ST_CPOutputmemorylatchclockline13/OEOutputenable(activelow)14DSSerialdatainputline16VCCPowerendIII74HC595DisplayControlofMulti-digitDigitalTubeHere,thisblogtakesthesingle-chipmicrocomputercontrolmulti-digitdigitaltubeasanexample.Tousethechipcorrectly,youmustfirstcorrectlyunderstandthetimingdiagramortruthtableofthechip.Thetruthtableof74HC595isshowninTable2.InputPinOutputPinDSSHCP/MRSTCP/OEHQ0~Q7outputhighimpedanceLQ0~Q7outputeffectivevalueLClearshiftregisterLRisingEdgeHShiftregisterstorelowlevelHRisingEdgeHShiftregisterstorehighlevelFallingEdgeHShiftregisterstateretentionRisingEdgeStatevalueinoutputshiftregisterFallingEdgeOutputmemorystateretentionItcanbefoundthattheserialdataisconnectedtotheDSpin,butitisonlyinputtotheshiftregisterwhenSH_CPisarisingedge,andentersthestorageregisterwhenST_CPisarisingedge.Ifthetwoclocksareconnectedtogether,theshiftregisterisalwaysonepulseearlierthanthestorageregister.Theshiftregisterhasaserialshiftinput(Ds),aserialoutput(Q7),andanasynchronouslow-levelreset.Thestorageregisterhasaparallel8-bit,three-statebusoutput.WhenOEisenabled(lowlevel),thedataofthestorageregisterisoutputtothebus.3.1HardwareConnectionSincethe8-bitdigitaltubeneedstoprovideatotalof16bitsofsegmentcodeandbitcodeatthesametime,itcannotberealizedbyusingone74HC595.Tosolvethisproblem,weusetwo595chipstocascadeseriallytoprovidean8-bitsegmentcode(providedbyU2)andan8-bitcode(providedbyU3).ThesimulationhardwarecircuitisshowninFigure3.Theinputsignalof595isconnectedtothethreeI/OportsofP2.0~P2.2respectively.Amongthem,P2.0providesserialinputsignals,P2.1andP2.2provideoutputandinputclocksignalsrespectively.Figure3.SimulationHardwareCircuitDiagram3.2SoftwareProgrammingHere,weuse2piecesof74HC595chipsforserialcascading.Therefore,youmustpayattentiontothesequenceofserialdataoutputwhenprogramming.Theusualpracticeisasfollows:First,writethedata(iebitcode)ofthe74HC595chipatthenextlevel;Then,writethedata(iesegmentcode)ofthefirst-level74HC595chip;Finally,releasetheparalleloutputpinstogetheratonce.Thesampleprogramisasfollows(partial):voidOneLed_Out(uchari,ucharLocation){ucharj;OutByte=Location;for(j=1;j=8;j++){DS=Bit_Out;SH_CP=0;SH_CP=1;SH_CP=0;OutByte=OutByte1;}OutByte=~Segment[i];for(j=1;j=8;j++){DS=Bit_Out;SH_CP=0;SH_CP=1;SH_CP=0;OutByte=OutByte1;}ST_CP=0;ST_CP=1;ST_CP=0;}3.3SimulationDebuggingWecandrawthehardwarecircuitdiagramontheProteus7platform,andthenwritethesoftwareprogramontheKeil4.0platformandcompileanddebugit.Then,loadthegeneratedHEXfileintothesimulationchipandrunthesimulation.Ifallgoeswell,theresultswillbedisplayedcorrectly.Accordingtothedisplayrequirements,itcanrealize8-bitdigitaltubeshiftdisplayor8-bitdigitaltubesimultaneousdisplay.ThesimulationresultsareshowninFigures4and5.Figure4.ShiftDisplayof8-bitDigitalTubeFigure5.SimultaneousDisplayof8-bitDigitalTubesIVConclusionThetestresultsofthisblogshowthattherearemanyadvantagestothedisplaycontrolofmulti-digitdigitaltubesthroughthecascadeof74HC595chips.Thesebenefitsaremainlyreflectedinthefollowingaspects:Itcangreatlyreducethedisplaycontrolofthesingle-chipdigitaltube;ItcangreatlyreducetheoccupancyoftheMCUI/Oportline;Thecircuitissimpleandeasytoprogram.Themethodintroducedinthisblog,whetheritistoconductsimulationteachingonacomputer,ortobuildactualhardwarecircuits.Ingeneral,Thecurrent74HC595chipiscost-effective,andthecostofbuildingacircuitislow,makingitverysuitableforgeneraluse.FAQWhatis74HC595?74HC595isashiftregisterwhichworksonSerialINParallelOUTprotocol.Itreceivesdataseriallyfromthemicrocontrollerandthensendsoutthisdatathroughparallelpins.Wecanincreaseouroutputpinsby8usingthesinglechip.Whatisa74hc595n?8-bitShiftRegister74HC595NAshiftregisterisachipyoucanusetocontrolmanyoutputs(8here)atthesametimewhileonlyusingafewpins(3here)ofyourArduino.Howdoesashiftregisterwork?Shiftregistersholdthedataintheirmemorywhichismovedorshiftedtotheirrequiredpositionsoneachclockpulse.Eachclockpulseshiftsthecontentsoftheregisteronebitpositiontoeithertheleftortheright.How74HC595ShiftRegiesterworks?The595hastworegisters(whichcanbethoughtofasmemorycontainers),eachwithjust8bitsofdata.ThefirstoneiscalledtheShiftRegister.TheShiftRegisterliesdeepwithintheICcircuits,quietlyacceptinginput.Howdoesan8bitshiftregisterwork?TheSN74HC595Nisasimple8-bitshiftregisterIC.Simplyput,thisshiftregisterisadevicethatallowsadditionalinputsoroutputstobeaddedtoamicrocontrollerbyconvertingdatabetweenparallelandserialformats.YourchosenmicroprocessorisabletocommunicatewiththeTheSN74HC595Nusingserialinformationthengathersoroutputsinformationinaparallel(multi-pin)format.Essentiallyittakes8bitsfromtheserialinputandthenoutputsthemto8pins.Whatisadigitaltube?Lightemittingdiodeconnectstheanodetogetherandthenconnectedtothepowerofpositiveiscalledcommonanodedigitaltube,lightemittingdiodeconnectedtothecathodeandthenconnectedtothepowerofthecathodeiscalledcommoncathodedigitaltube.Whatisthedifferencebetweenshiftregisterandcounter?Inashiftregister,theinputofelementNistheoutputofelementN-1,andallelementsusethesameclock.Inacounter,theinputofelementNistheinverseofitsoutput,andtheclockofelementN+1istheoutputofelementN.

293D476X96R3B2TE3-VISHAY

IDescriptionTheinstrumentationamplifiercircuithasthefollowingfeatures:HighInputImpedance;HighCommon-modeRejectionRatio;LowDrift;...Theabovefeaturesmakeitwidelyusedinfieldsofsmallsignalamplificationofsensoroutput.Thisblogwillintroduce4implementationoptionsofinstrumentationamplifiercircuits.These4optionsaredesignedbasedondifferentelectroniccomponents.Andtheyarealsoonthebasisofexplainingthecircuitstructureandprincipleoftheinstrumentamplifier.Theelectroniccomponentsdiscussedinthisbloginclude:LM741,OP07,LM324,AD620.Wewillsummarizefeaturesofthe4circuitthroughtesting,analysisandcomparison.Ibelievethisblogcanprovideacertainreferenceforcircuitdesignbeginners.WhatAreInstrumentationAmpilfiers?CatalogIDescriptionIIIntroduction2.1InstrumentationAmplifierOverview2.2InstrumentationAmplifierStuctureandPrincipleIIIInstrumentationAmplifierCircuitDesign3.1LM741CircuitOption3.2OP07CircuitOption3.3LM324CircuitOption3.4AD620CircuitOptionIVPerformanceTestandAnalysisFAQOrdering&QuantityIIIntroduction2.1InstrumentationAmplifierOverviewThesignalsinputbysmartmetersthroughsensorsgenerallyhavethecharacteristicsofsmallsignals:Thesignalamplitudeisverysmall(millivoltorevenmicrovoltmagnitude);Oftenaccompaniedbyloudnoise.Forsuchsignals,thefirststepofcircuitprocessingisusuallytoamplifysmallsignalswithaninstrumentationamplifier.Themainpurposeofamplificationisnottogain,buttoimprovethesignal-to-noiseratioofthecircuit.Atthesametime,fortheinstrumentationamplifiercircuit,thesmallertheinputsignalthatcanberesolved,thebetter;thewiderthedynamicrange,thebetter.Therefore,theperformanceoftheinstrumentationamplifiercircuitdirectlyaffectstherangeoftheinputsignalthatthesmartinstrumentcandetect.2.2InstrumentationAmplifierStuctureandPrincipleThetypicalstructureoftheinstrumentamplifiercircuitisshownasinFig.1.Itismainlycomposedoftwo-stagedifferentialamplifiercircuit.Figure1.StructureofInstrumentationAmplifierAmongthem,theoperationalamplifierA1,A2arein-phasedifferentialinputmodes.Non-invertinginputcangreatlyincreasetheinputimpedanceofthecircuit.Atthesametime,itcanalsoreducetheattenuationofweakinputsignalsbythecircuit;Differentialinputcanmakethecircuitonlyamplifythedifferentialmodesignal,andonlyfollowthecommonmodeinputsignal.Inthisway,theratiooftheamplitudeofthedifferentialmodesignaltothecommonmodesignal(ie,thecommonmoderejectionratioCMRR)senttothesubsequentstageisimproved.Inthisway,inthedifferentialamplifiercircuitcomposedofoperationalamplifierA3asthecorecomponent,undertheconditionthattheCMRRrequirementsremainunchanged,theaccuracymatchingrequirementsforresistorsR3andR4,RfandR5canbesignificantlyreduced.Asaresult,theinstrumentationamplifiercircuithasbettercommonmoderejectioncapabilitythanasimpledifferentialamplifiercircuit.UndertheconditionsofR1=R2,R3=R4,Rf=R5,thegainofthecircuitinFigure1is:G=(1+2R1/Rg)(Rf/R3)ItcanbeseenfromtheformulathattheadjustmentofthecircuitgaincanbeachievedbychangingtheRgresistance.IIIInstrumentationAmplifierCircuitDesignAtpresent,theimplementationmethodsofinstrumentationamplifiercircuitsaremainlydividedintotwocategories:Thefirstcategoryiscomposedofdiscretecomponents;Thesecondcategoryisdirectlyimplementedbyasingleintegratedchip.Intheblog,withsingleopampLM741andOP07,integratedfouropampLM324andmonolithicintegratedchipAD620asthemainelectroniccomponents,4kindsofinstrumentationamplifiercircuitoptionsaredesigned.3.1LM741CircuitOptionConsistsofthreegeneral-purposeoperationalamplifiersLM741toformathreeoperationalamplifierinstrumentamplifiercircuitform.Andsupplementedbyrelatedresistorperipheralcircuits.Atthesametime,addthebridgesignalinputcircuitofthenon-invertinginputterminalsofA1andA2,asshowninFigure2.Figure2.SingleOpAmpInstrumentationAmplifierA1~A3inFigure2canbereplacedwithLM741respectively.Theworkingprincipleofthecircuitisexactlythesameasthatofatypicalinstrumentationamplifiercircuit.3.2OP07CircuitOptionComposedof3precisionoperationalamplifiersOP07,thecircuitstructureandprinciplearethesameasinFig.2(3OP07sareusedtoreplaceA1~A3inFig.2respectively).3.3LM324CircuitOptionTakeafouroperationalamplifierintegratedcircuitLM324asthemaincomponent,asshowninFigure3.Itscharacteristicistointegrate4functionallyindependentoperationalamplifiersintothesameintegratedchip.WhataretheadvantagesofusingLM324?Thatis,itispossibletogreatlyreducethedifferenceindeviceperformanceofeachopampduetodifferentmanufacturingprocesses.Inaddition,theuseofaunifiedpowersupplyisconducivetothereductionofpowersupplynoiseandtheimprovementofcircuitperformanceindicators.Andthebasicworkingprincipleofthecircuitremainsunchanged.Figure3.LM324InstrumentationAmplifier3.4AD620CircuitOptionThecircuitconsistsofamonolithicintegratedchipAD620asthemainelectroniccomponents,asshowninFigure4.Itischaracterizedbyasimplecircuitstructure:anAD620,againsettingresistorRg,andaworkingpowersupply.Therefore,thedesignefficiencyisveryhigh.ThecircuitgaincalculationformulainFig.4is:G=49.4K/Rg+1.Figure4.AD620InstrumentationAmplifierIVPerformanceTestandAnalysisThefouroptionsoftheinstrumentationamplifiercircuitalladopttheformofabridgecircuitcomposedof4resistors,whichchangesthedouble-endeddifferentialinputintoasingle-endedsignalsourceinput.Theperformancetestismainlytocarryoutsimulationandactualcircuitperformancetestfromthefollowingaspects:1.ThemaximuminputofthesignalsourceVs;2.VsminimuminputofsignalsourceVs;3.Themaximumgainofthecircuit;4.Commonmoderejectionratio.ThetestdataareshowninTable1andTable2.Amongthem,themaximum(small)inputofVsreferstothemaximum(small)inputofthesignalsourcewhenthecircuitoutputisnotdistortedundergiventestconditions.Themaximumgainreferstothemaximumgainvalueofthecircuitthatcanbeachievedwhentheoutputisnotdistortedunderthegiventestconditions.ThecommonmoderejectionratioiscalculatedbytheformulaKCMRR=20|g|AVd/AVC|(dB).Note:fisthefrequencyofVsinputsignal;Thevoltagemeasurementdatainthetableareallexpressedbypeak-to-peakvalue;Duetothesimulationdevice,thesimulationofoption3withMultisimfailedintheexperiment,and-inTable1indicatesthefailuredata;Options1to4inthetablerespectivelyrepresenttheinstrumentationamplifiercircuitcomposedofLM741,OP07,LM324andAD620respectively.FromthemeasureddatainTable2,wecanseefromit:Foroption2,ithasthebestperformanceintermsofsignalinputrange(thatis,themaximumandminimuminputofVs),circuitgain,andcommon-moderejectionratio.Intermsofcomponentprice,itisalittlehigherthanthecostoftheLM741option1andtheLM324option3,butitismuchcheaperthantheAD620option4.Therefore,amongthefouroptions,option2ofOP07hasthehighestcostperformance.Foroption4,inadditiontoitsrelativelysmallmaximumgain,itsotherperformanceissecondonlytooption2.option4hastheadvantagesofsimplecircuit,superiorperformance,andsavingdesignspace.However,thehighcostisitsbiggestdisadvantage.Foroption1andoption3,thereislittledifferenceintheirperformance.option3isslightlybetterthanoption1,andtheyalsohaveabsolutepriceadvantages,buttheirperformanceisnotasgoodasoption2andoption4.Basedontheaboveanalysis,option2andoption4aresuitableforoccasionswithhigherperformancerequirementsforinstrumentamplifiercircuits.Amongthem:Option2ofOP07isthemostcost-effectiveOption4ofAD620issimpleandefficient,butthecostishigh.Option1ofLM741andOption3ofLM324aresuitableforoccasionswhereperformancerequirementsarenothighandcostsavingsareneeded.Accordingtospecificcircuitdesignrequirements,differentoptionsareselectedtoachieveoptimalresourceutilization.Figure5.InstrumentationAmplifierICInaddition,afterthecircuitdesignplanisdetermined,thefollowingaspectsshouldbepaidattentiontointhespecificcircuitdesignprocess:1.Payattentiontotheselectionofkeycomponents.Forexample,forthecircuitshowninFigure2,thereareafewthingstopayattentionto:MakethecharacteristicsofopampA1andA2asconsistentaspossible;Whenselectingresistors,resistorswithalowtemperaturecoefficientshouldbeusedtoobtainthelowestpossibledrift;TheselectionofR3,R4,R5andR6shouldmatchasmuchaspossible.2.Payattentiontoaddingvariousanti-interferencemeasuresinthecircuit.suchas:Thepowersupplydecouplingcapacitorshouldbeaddedatthelead-inendofthepowersupply;RClow-passfilteringshouldbeaddedtothesignalinputterminalorhigh-frequencynoisecancelingcapacitorsshouldbeaddedtothefeedbackloopoftheoperationalamplifierA1andA2;ThePCBdesignshouldbecarefullylaidoutandroutedreasonably,andgroundwiresshouldbehandledcorrectly.FAQWhatislm324?LM324isaQuadop-ampICintegratedwithfourop-ampspoweredbyacommonpowersupply.Thedifferentialinputvoltagerangecanbeequaltothatofpowersupplyvoltage....Generally,op-ampscanperformmathematicaloperations.Whichisthedifferencebetweenlm324andlm339?TheLM324hasacomplementaryoutputwhiletheLM339isopencollector.Inthecomplementaryoutput,currentcanflowineitherdirectionasrequired(eithersourceorsink)whiletheopencollectoroutputcanonlysinkcurrent.Whatisopampusefor?OperationalamplifiersarelineardevicesthathaveallthepropertiesrequiredfornearlyidealDCamplificationandarethereforeusedextensivelyinsignalconditioning,filteringortoperformmathematicaloperationssuchasadd,subtract,integrationanddifferentiation.Howdoesanopampwork?Whatislm324usedfor?LM324ICApplicationsTheapplicationsofICLM324includethefollowing.ByusingthisIC,theconventionalop-ampapplicationscanbeimplementedverysimply.ThisICcanbeusedasoscillators,rectifiers,amplifiers,comparatorsetc.I.IntroductionAsweallknow,theionnitridingprocessrequiresrelativelyhighcontrolofthepressureinsidethefurnace,sothispaperdesignsagasflowcontrollerbasedontheL298NchipdrivenDCmotorcontrol,whichcanbeusedtocontrolthegasflowofthereactor.Soletsfirstunderstandtheionnitridingtheory.CatalogI.IntroductionII.IonNitridingTheoryIII.SystemFlowandPressureMeasurementandControlBlockDiagramIV.L298NChipIntroductionV.ControllerPrincipleVI.ConclusionFAQOrdering&QuantityII.IonNitridingTheoryNitridingisachemicalheattreatmentmethodtostrengthenthemetalsurface.Itistoplacemetalpartsinanactivenitrogenmedium,andatacertaintemperatureandholdingtime,thenitrogenelementcanpenetrateintothemetalsurface,therebychangingthechemicalcompositionofthemetallayertomakeithavehighwearresistance,fatiguestrength,corrosionresistanceandburnresistance,etc.,soitiswidelyusedinindustry.Ionnitridingiscarriedoutinalow-temperatureplasma.Thelow-pressuregasisionizedundertheactionofanelectricfieldtoproducehigh-energyionsandhigh-energyneutralatoms.Thesehigh-energyparticlescanimprovethestructureoftheinfiltrationlayer,promotethechemicalreactionprocess,andacceleratethenitridinglayerformation.Ionnitridingiscarriedoutinglowdischarge.Intheprocessofionnitriding,thepressurecontrolaccuracyofthefurnaceisrelativelyhigh,andthecontroldeviationreachesseveraltensofPa.AccordingtoPaschensLaw:Amongthem:Pisthegaspressure;Disthedistancebetweenparallelplateelectrodes;Visthecathodesecondaryelectronemissioncoefficient;BisStolevsconstant;Aisaconstant.Takingthederivativeofformula(1),thebreakdownvoltageexpression(2)canbeobtained:Itcanbeseenfromformula(2)thatthebreakdownvoltageVisrelatedtothegaspressureandd,andingeneralexperiments,disfixed,soionnitridingisextremelyimportantforpressurecontrol.III.SystemFlowandPressureMeasurementandControlBlockDiagramTheflowmetercontrolsthegasflowattheinlet.Whentheinletandexhaustflowsarebalanced,thefurnacepressureremainsstable.Duetotheinternalinfluenceoffurnacegasleakageandotherinterferencefactors,theinternalpressureofthefurnacefluctuatesupanddown,andthesystemdeviatesfromtheequilibriumstate,whichaffectstheplasmaprocessinseverecases.WeuseanordinaryDCmotortodrivetheDCmotorthroughtheL298N,andthemotordrivestheconetorotatethroughthereductionlever.Whentheconeisscrewedin,thegaspumpedoutperunittimeisreduced;whenitisscrewedout,thegaspumpedoutincreases,sothatthepressureinsidethefurnaceisstabilizedattherequiredvalue.Thechangeoffurnacepressureismeasuredbythepressuresensorandpassedthroughthetransmitter,whichsendsthegasflowcontrollertothefeedbackvoltage.Theelectricvacuumbutterflyvalveusedforthesuctionportisexpensive,asshowninFigure1.Figure1BlockdiagramofsystemflowandpressuremeasurementandcontrolIV.L298NChipIntroductionL298NcanacceptstandardTTLlogiclevelsignalVSS,andVSScanbeconnectedto4.5~7Vvoltage.4pinVSisconnectedtothepowersupplyvoltage,andtheVSvoltagerangeVIHis+2.5~46V.Theoutputcurrentcanreach2.5A,whichcandriveinductiveloads.Theemittersofpin1andpin15areseparatelyledouttoconnectthecurrentsamplingresistortoformacurrentsensingsignal.L298candrivetwomotors,OUT1,OUT2andOUT3,OUT4canbeconnectedtoeachmotor,thisexperimentaldevicewechoosetodriveonemotor.Pins5,7,10and12areconnectedtotheinputcontrolleveltocontroltheforwardandreverserotationofthemotor.EnAandEnBareconnectedtothecontrolpotentialenergyendtocontrolthestallingofthemotor.Figure2istheL298Nfunctionallogicdiagram,Table1istheL298Ninternalfuntionalmodule.Figure2L298NfunctionallogicdiagramEnAIn1In2OperativeCondition0Stop110Rotatingforward101Inversion111Brake100StopTable1L298NinternalfunctionalmoduleThefunctionalmoduleofIn3andIn4isthesameasTable1.ItcanbeseenfromTable1thatwhenEnAislowlevel,theinputlevelhasaneffectonmotorcontrol.WhenEnAishighlevel,whenEnAishigh,theinputlevelisonehighandonelow,andthemotorrotatesforwardorreverse.Iftheyarebothlowlevel,themotorwillstop,andiftheyarebothhighlevel,themotorwillbrake.V.ControllerPrincipleFigure3istheschematicdiagramofthecontroller,composedof3dashedblockdiagrams:Figure3TheschematicdiagramofthecontrollerThefollowingarethefunctionsofthe3dashedblockdiagrams:(1)Thedashedblockdiagram1controlstheforwardandreverserotationofthemotor,U1AandU2Aarecomparators,andVIcomesfromthevoltageofthefurnacepressuresensor.WhenVIVRBF1,U1Aoutputshighlevel,U2Aoutputhighlevelturnsintolowlevelthroughinverter,andthemotorrotatesforward.Similarly,whenVIVRBF1,themotorreverses.Theforwardandreverserotationofthemotorcancontroltheflowofgasextractedbytheairextractor,therebychangingthepressureinsidethefurnace.(2)Inthedashedblockdiagram2,twocomparatorsU3AandU4Aformadual-limitcomparator.WhenVBVIVA,itoutputslowlevel,andwhenVIVA,VIVB,itoutputshighlevel.VA,VBaretheupperandlowerlimitsofthevoltageconvertedbythefurnacepressuretransducer,thatis,thecontrolrangeofthereactionfurnacepressure.Accordingtoprocessrequirements,wecanspecifythevaluesofVAandVBbyourselves,aslongasthefurnacepressureiswithintherangedeterminedbyVAandVB,themotorstops(notethatVB<VRBF1<VA,ifitisnotinthisrange,thesystemisunstable).(3)Thedashedblockdiagram3isalongdelaycircuit.U5Aisacomparator,Rs1isthesamplingresistor,VRBF2isthemotorovercurrentvoltage.ThevoltageonRs1isgreaterthanVREF2,themotorisovercurrent,andU5Aoutputslowlevel.Itcanbeseenfromtheabovethatblock1controlstheforwardandreverserotationofthemotor,andblock2controlsthesizeoftherippleofthefurnacepressure.Whenthefurnacepressureistoosmallortoolarge,themotorturnstoafixedpositionatbothendstostop,accordingtothesteady-stateoperatingequationoftheDCmotor:Amongthem:Фisthemagneticfluxofeachpoleofthemotor;Ceistheelectromotiveforceconstant;Nisthenumberofmotorrevolutions;Iaisthearmaturecurrent;Raisthearmatureloopresistance.WhenthenumberofrevolutionsofthemotorNis0,thecurrentofthemotorincreasessharply,andthemotorwillburnoutifthetimeistoolong.Butwhenthemotorstarts,thecurrentinthecoilinthemotoralsoincreasessharply,sowemustseparatethesetwostates.Thelongdelaycircuitcandistinguishthesetwostates.Theworkingprincipleofthelong-delaycircuit:WhentheRs1overcurrentU5Ageneratesanegativepulseandisdifferentiated,thepulsetriggerspin2of555,thecircuitisset,andpin3outputshighlevel.Becausethedischargeterminal7pinisopen,C1,R5andU6Aformedasanintegration,thenstartworking,thechargingvoltageonthecapacitorC1riseslinearly,andtheintegrationconstantofthedelayoperationalamplifieris100R5C1.WhenthechargingvoltageonC1,thatis,thevoltageonpin6exceeds2/3VCC,the555circuitresetsandoutputsalowlevel.Themotorgenerallystart-upinlessthan0.8s,andtheC1chargingtimeisgenerally0.8~1s.TheoutputlevelofU5AisORedwiththeoutputlevelofpin3of555viaU7.IftheoutputlowlevelofU5AislongerthanthechargingtimeofC1,U7outputslowlevelafterC1ischarged.TheANDgateU8inputstothe6pinENAterminalofL298N.Themotorstops.IftheoutputlevelofU5AislessthanthechargingtimeofC1,pin6willnotactandthemotorwillstartnormally.Thelongdelaycircuitabsorbsthemotorstart-upovercurrentvoltagewaveform,sothatthemotorstartsnormally.VI.ConclusionThisarticlesummarizesthedesignschemeforthepressurecontrolofionnitridingbasedontheL298Nchip.Ithasbeenprovedthattheuseofthiscontrollertocontrolthegasflowcanreduceproductioncosts,increasethesystemcostperformance,andimprovethecontroldynamicperformanceandstabilityoftheentiresystemcontrol.FAQWhatisl298n?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.Whatistheuseofl298n?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.Howdoesl298ncontrolDCmotorspeed?1.IfyousendaHIGHsignaltotheenable1pin,motorAisreadytobecontrolledandatthemaximumspeed;2.IfyousendaLOWsignaltotheenable1pin,motorAturnsoff;3.IfyousendaPWMsignal,youcancontrolthespeedofthemotor.Themotorspeedisproportionaltothedutycycle.Whatisl298nmotordrivermodule?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.Howdoesl298nmotordriverwork?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.Howdoiuseal298motordriverwithArduino?Startbyconnectingpowersupplytothemotors.InourexperimentweareusingDCGearboxMotors(alsoknownasTTmotors)thatareusuallyfoundintwo-wheel-driverobots.Theyareratedfor3to12V.So,wewillconnectexternal12VpowersupplytotheVCCterminal.WhatisthefunctionofHbridge?AnH-bridgeisanelectroniccircuitthatswitchesthepolarityofavoltageappliedtoaload.ThesecircuitsareoftenusedinroboticsandotherapplicationstoallowDCmotorstorunforwardsorbackwards.Whatisthedifferencebetweenl293dandl298n?L293isquadruplehalf-HdriverwhileL298isdualfull-Hdriver,i.e,inL293allfourinput-outputlinesareindependentwhileinL298,ahalfHdrivercannotbeusedindependently,onlyfullHdriverhastobeused....Hence,heatsinkisprovidedinL298.I.IntroductionDCmotorsarewidelyusedinvariousfieldsduetotheirgoodspeedregulationperformance,largestartingtorqueandstrongoverloadcapacity.Inrecentyears,thestructureandcontrolmethodsofDCmotorshaveundergonegreatchanges.Withcomputersenteringthecontrolfieldandthecontinuousemergenceofnewpowerelectronicpowercomponents,PWM(pulsewidthmodulation)speedregulationhasbecomeanewwayofDCmotorspeedregulation.Andwiththeadvantagesofhighswitchingfrequency,stablelow-speedoperation,excellentdynamicperformance,andhighefficiency,itiswidelyusedinDCmotorspeedregulation.Therefore,thispaperproposesthedesignofaDCmotorPWMcontrolsystembasedon80C196KCandL298N.CatalogI.IntroductionII.PrincipleofPWMSpeedControlSystemIII.ControlSystemHardwareDesign3.1IntroductiontoPowerIntegratedCircuitL298N3.2DCMotorControlSystemHardwareCircuit3.3Anti-interferenceandElectromagneticCompatibilityDesignIV.ControlSystemSoftwareRealizationV.ConclusionFAQOrdering&QuantityII.PrincipleofPWMSpeedControlSystemPWM,orpulsewidthmodulation,referstotheuseoftheswitchingcharacteristicsofhigh-powertransistorstomodulateafixedvoltageDCpowersupply,whichisturnedonandoffatafixedfrequency,andthelengthoftheonandofftimeinacycleischangedasneeded.BychangingthedutycycleofthevoltageonthearmatureoftheDCservomotor,theaveragevoltageischangedtocontrolthespeedofthemotor.Therefore,itisoftencalledaswitchdrivedevice.TheschematicdiagramofPWMcontrolisshowninFigure1.Figure1PWMcontrolschematicdiagramThereareusuallytwowaystochangethedutycycle:PWMandPFM(pulsefrequencymodulation).PWMisbychangingthewidthoftheon-pulse,whichiscommonlyreferredtoasthefixedfrequencywidthmodulationmethod.PFMmeansthattheon-pulsewidthisconstantandthedutycycleischangedbychangingtheswitchingfrequency.Becausewhenitencountersmechanicalresonanceataparticularfrequency,itoftenresultsinsystemvibrationandhowling.Therefore,inthecontrolofDCmotors,thePWMcontrolmethodismainlyused.III.ControlSystemHardwareDesignTheDCmotorspeedcontrolsystembasedon80C196KCandL298Niscomposedofthesmallestsingle-chipmicrocomputersystem,R/Dconverter,PWMpoweramplifiercircuit,A/DandD/Aconversioncircuit,andreceivingcommandinterfacecircuit.Theminimumsystemofthesingle-chipmicrocomputeradoptsthe16-bitsingle-chip80C196KCexternalexpansioninterfacecircuit,whichismainlyusedtorealizethefunctionsofdataacquisitionandPWMsignalgeneration.TheblockdiagramofthespeedcontrolsystemisshowninFigure2.Figure2BlockdiagramofPWMspeedcontrolsystem3.1IntroductiontoPowerIntegratedCircuitL298NInordertoimprovesystemefficiencyandreducepowerconsumption,thepoweramplifierdrivecircuitadoptstheintegratedcircuitL298NbasedonthebipolarH-bridgepulsewidthmodulationmethod.L298Nisahigh-performancepulse-widthmodulationpoweramplifierproducedbySGS,whichhasthecharacteristicsofsmallsizeandstrongdrivingability.ItcontainstwoH-bridgehigh-voltageandhigh-currentbridgedrivers,whichcanrealizethefull-bridgedriveofthemotorwithasinglechip,whichcandrivemotorsbelow46Vand2A.TheinternalstructureofL298NisshownasinFigure3.Figure3L298Ninternalstructureblockdiagram3.2DCMotorControlSystemHardwareCircuitL298NcandrivetwoDCmotors,becausethespeedcontrolsystemisasingle-axisstructure,inordertomakefulluseoftheloadcapacityofthepoweramplifiercircuit,sothatthesystemstartsatthemaximumaccelerationandbrakesatthemaximumacceleration,inthedesign,theinputterminalandtheoutputterminalareconnectedinparalleltocontroltheDCmotor.Thesingle-chip80C196KCgivesaPWMsignalaccordingtothecalculationresultsofthepositionloopandthespeedloop.ThePWMsignalisdirectlyoutputtotheIN1(IN3)terminal,andthePWMsignalisinvertedandoutputtoIN2(IN4)through7406.WhenthedutycycleofthePWManalogsignalis50%,thepositiveandnegativevoltagesatbothendsofthemotorareappliedforthesametime.Themotorisinastateoftremoratthisposition,thatis,inthepowerlubricationstate.Whenthedutycycleisgreaterthan50%,thesignalvoltageOUTAisgreaterthanOUTB,andthemotorrotatesforward,otherwisereverse.Therefore,theoutputpolarityofeachlinkmustbestraightenedouttoformnegativefeedbackandcompleteclosed-loopcontrol.RelyingonchangingthePWMdutycycletocontrolthemotorspeedcanalsochangethemotorrotationdirection,thecontrolmethodissimpleandreliable.Inaddition,becausethemotorisofelectriccoiltype,reverseelectromotiveforcewillbeformedwhenthemotorhasanemergencystopandsuddencommutation.ToensurethenormaloperationoftheL298Ndrivechip,twopairsofcontinuationsareaddedbetweentheoutputterminalsOUTA,OUTBandtheDCmotor.TheflowdiodeshuntsthecurrenttothepositiveorgroundterminalofthepowersupplytopreventbackelectromotiveforcefromdamagingtheL298N.3.3Anti-interferenceandElectromagneticCompatibilityDesignWhenthemotorisdriven,therapidon-offofthepowermainswitchingelementleadstoalargerateofchangeofpowercurrentandvoltage,whichnotonlyaffectsthedrivecircuitbutalsoentersthecontrolcircuitthroughthepowersupplyandground.Inaddition,whenthemotorstartsandbrakes,thetransientvoltageisgeneratedatthesuddenchangeoftheload,itsamplitudewillbehigherthanthepowersupplyvoltage,andtheleadingedgeissteep,thefrequencybandisverywide,anditentersthecontrolcircuitthroughtheDCpowersupply.Therefore,anti-interferenceandelectromagneticcompatibilitydesignisalsoveryimportant.Thesystemhasadoptedmeasuressuchascurrentsmoothing,deburringandshielding.Currentsmoothing:BecausetheinstantaneousenergyofthePWMswitchisrelativelylarge,theRCfilterisusedattheoutputofthePWMpoweramplifiertofilter.Byselectingtheappropriateresistanceandcapacitancevalues,high-frequencyharmonicsareeffectivelysuppressedandthepeakvoltageofthePWMpoweramplifierisabsorbed.Therebyreducingtheinterference;Deburring:Thesystemincreasesthefiltercapacitoronthepowersupplyside,andusesonelargeandonesmallcapacitorinparallel.Thelargecapacitorisresponsibleforthedecoupling,filtering,andsmoothingoflow-frequencyalternatingsignals,andthesmallcapacitoreliminatesmid-andhigh-frequencyparasiticscouplinginthecircuitnetwork,whicheffectivelyreducesspikesandburrs;Shielding:Themotordrivecableadoptsdouble-shieldedcables,andthewiringshouldbeseparatedfromothercablesasmuchaspossible.Figure4DrivehardwarecircuitdiagramIV.ControlsystemsoftwarerealizationThecontrolsystemadoptsthespeed-positionclosed-loopcombinationmethod,takingthepositioncontrolmethodasanexampletointroducetherealizationmethodofthesoftware.ThepositioncontrolisbasedontheclassicPIcontrolalgorithm,andtheproportionalandintegralparametersaresimplifieddesign,andthesegmentedPIcontrolisintroduced.,Thatis,thecalculatederrorisdividedintosections,anddifferentproportionalandintegralparametersparticipateintheadjustmentwithintheerrorrangeofeachsection,whichensuresthesmootherandmorestableoperationofthesystem.ThederivationandsimplificationprocessofPIformulaisasfollows:ThespecificsoftwareimplementationflowchartisshowninFigure5.Thatis,afterreceivingagivenanglecommand,firstcalculatethedifferencebetweenthesampledpositioninformationandthegivenangle,andthendividethedifferenceintonequalparts,andeachsegmentcorrespondstoasetofparametersKp1andki1participateinmediationcontrol,calculatetheoutputofPIcontrolandthenconvertitintothecorrespondingPWMnumericaloutput.Figure5ThespecificsoftwareimplementationflowchartV.ConclusionThisarticlesumsupthedesignschemeoftheDCmotorPWMcontrolsystembasedon80C196KCandL298N.Thesingle-chipmicrocomputergeneratesPWMsignaltothepowerintegratedcircuitL298N.TheclassicPIsegmentcontrolisusedtocontrolthemotor.Ithasthecharacteristicsofsimplecircuitandconvenientcontrol.Theoperatingtestresultsshowthatthesystemworksstablyandreliably,meetstherequirementsofthespeedregulationfunction,andhasbeensuccessfullyappliedtomanyairborneproducts.FAQWhatisl298n?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.Whatistheuseofl298n?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.Howdoesl298ncontrolDCmotorspeed?1.IfyousendaHIGHsignaltotheenable1pin,motorAisreadytobecontrolledandatthemaximumspeed;2.IfyousendaLOWsignaltotheenable1pin,motorAturnsoff;3.IfyousendaPWMsignal,youcancontrolthespeedofthemotor.Themotorspeedisproportionaltothedutycycle.Whatisl298nmotordrivermodule?ThisL298NMotorDriverModuleisahighpowermotordrivermodulefordrivingDCandStepperMotors.ThismoduleconsistsofanL298motordriverICanda78M055Vregulator.L298NModulecancontrolupto4DCmotors,or2DCmotorswithdirectionalandspeedcontrol.Howdoesl298nmotordriverwork?TheL298NisadualH-BridgemotordriverwhichallowsspeedanddirectioncontroloftwoDCmotorsatthesametime.ThemodulecandriveDCmotorsthathavevoltagesbetween5and35V,withapeakcurrentupto2A.Howdoiuseal298motordriverwithArduino?Startbyconnectingpowersupplytothemotors.InourexperimentweareusingDCGearboxMotors(alsoknownasTTmotors)thatareusuallyfoundintwo-wheel-driverobots.Theyareratedfor3to12V.So,wewillconnectexternal12VpowersupplytotheVCCterminal.WhatisthefunctionofHbridge?AnH-bridgeisanelectroniccircuitthatswitchesthepolarityofavoltageappliedtoaload.ThesecircuitsareoftenusedinroboticsandotherapplicationstoallowDCmotorstorunforwardsorbackwards.Whatisthedifferencebetweenl293dandl298n?L293isquadruplehalf-HdriverwhileL298isdualfull-Hdriver,i.e,inL293allfourinput-outputlinesareindependentwhileinL298,ahalfHdrivercannotbeusedindependently,onlyfullHdriverhastobeused....Hence,heatsinkisprovidedinL298.

293D476X96R3B2TE3-VISHAY

IDescriptionDS18B20isawidelyuseddigitaltemperaturesensor,anditsoutputisadigitalsignal.DS18B20hasthecharacteristicsofsmallsize,lowhardwareoverhead,stronganti-interferenceabilityandhighprecision.TheDS18B20digitaltemperaturesensoriseasytowireandcanbeusedinmanyoccasionsafterbeingpackaged.Suchaspipe,thread,magnetadsorption,stainlesssteelpackageandsoon.ThisArduinoforbeginnerstutorialwillteachyouhowtoreadtheDS18B201-wiretemperaturesensor.CatalogIDescriptionIIIntroductiontoDS18B202.1DS18B20BasicInformation2.2DS18B20Features2.3DS18B20StructureIIIIntroductiontoComponents3.1Memory3.264-bitLithographyROM3.3ConnectionofExternalPowerSupply3.4ConfigurationRegister3.5TemperatureReadingIVDS18B20WorkingPrincipleVConclusionFAQOrdering&QuantityIIIntroductiontoDS18B202.1DS18B20BasicInformationDS18B20isanimprovedintelligenttemperaturesensornewlylaunchedbyAmericanDALLASSemiconductorafterDS1820.Comparedwiththetraditionalthermistor,DS18B20candirectlyreadthemeasuredtemperatureandcanrealizethe9-12-digitdigitalvaluereadingmodethroughsimpleprogrammingaccordingtoactualrequirements.Itcanalsocomplete9-bitand12-bitdigitalquantitiesin93.75msand750ms,respectively.Moreover,theinformationreadfromtheDS18B20ortheinformationwrittenintotheDS18B20onlyneedsoneportline(single-wireinterface)toreadandwrite,andthetemperatureconversionpowercomesfromthedatabus.ThebusitselfcanalsosupplypowertotheconnectedDS18B20withouttheneedforanadditionalpowersupply.Therefore,theuseofDS18B20canmakethesystemstructuresimplerandmorereliable.DS18B20hasgreatlyimprovedcomparedwithDS1820intermsoftemperaturemeasurementaccuracy,conversiontime,transmissiondistance,andresolution.Itbringsmoreconvenientuseandmoresatisfyingeffectstousers.2.2DS18B20FeaturesUnique1-WireInterfaceRequiresOnlyOnePortPinforCommunicationReduceComponentCountwithIntegratedTemperatureSensorandEEPROMMeasuresTemperaturesfrom-55Cto+125C(-67Fto+257F)0.5CAccuracyfrom-10Cto+85CProgrammableResolutionfrom9Bitsto12BitsNoExternalComponentsRequiredParasiticPowerModeRequiresOnly2PinsforOperation(DQandGND)SimplifiesDistributedTemperature-SensingApplicationswithMultidropCapabilityEachDeviceHasaUnique64-BitSerialCodeStoredinOn-BoardROMFlexibleUser-DefinableNonvolatile(NV)AlarmSettingswithAlarmSearchCommandIdentifiesDeviceswithTemperaturesOutsideProgrammedLimitsAvailablein8-PinSO(150mils),8-PinSOP,and3-PinTO-92Packages2.3DS18B20StructureTheexternalstructureofDS18B20isshowninthefigure1.Amongthem:VDDisthepowerinputterminal;DQisthedigitalsignalinput/outputterminal;GNDisthepowerground.Figure1.DS18B20ExternalStructureTheinternalstructureofDS18B20mainlyincludes4parts:64-bitlithographyROM;Temperaturesensor;Non-volatiletemperaturealarmtriggersTHandTL;Configurationregister.Figure2.DS18B20ExternalStructureInthe64-bitROM,themanufacturerhasa64-bitserialnumberburnedbythemanufacturerbeforetheproductleavesthefactory.TheserialnumbercanberegardedastheaddressserialcodeofDS18B20,usedtodistinguisheachDS18B20.Soastobetterrealizethemulti-pointmeasurementoffieldtemperature.IIIIntroductiontoComponents3.1MemoryThememoryofDS18B20includeshigh-speedscratchpadRAMandelectricallyerasableRAM.TheelectricallyerasableRAMalsoincludestemperaturetriggersTHandTL,andaconfigurationregister.Thememorycancompletelydeterminethecommunicationoftheone-lineport,andthenumberiswrittenintotheregisterwiththecommandofwritingtheregister.Thenyoucanusethereadregistercommandtoconfirmthesenumbers.Afterconfirmation,youcanusethecopyregistercommandtotransferthesenumberstotheelectricallyerasableRAM.Whenthenumberintheregisterismodified,thisprocesscanensuretheintegrityofthenumber.ThescratchpadRAMiscomposedof8bytesofmemory.Theninthbytecanbereadwiththereadregistercommand.Thisbyteistocheckthepreviouseightbytes.3.264-bitLithographyROMFor64-bitlithographyROM:Thefirst8bitsaretheowncodeofDS18B20Thenext48bitsareconsecutivedigitalcodesThelast8bitsaretheCRCcheckofthefirst56bits.The64-bitlithographyROMalsoincludes5ROMfunctioncommands:readROM,matchROM,skipROM,searchROMandalarmsearch.3.3ConnectionofExternalPowerSupplyDS18B20canuseexternalpowerVDDorinternalparasiticpower.WhentheVDDportisconnectedtoavoltageof3.0V-5.5V,anexternalpowersupplyisused.AninternalparasiticpowersupplyisusedwhentheVDDportisgrounded.Inaddition,whetheritisaninternalparasiticpowersupplyoranexternalpowersupply,theI/Oportlineshouldbeconnectedtoapull-upresistorofabout5K.3.4ConfigurationRegisterTheconfigurationregisteristoconfiguredifferentdigitstodeterminethetemperatureanddigitalconversion.ItcanbeknownthatR1andR0arethedeterminingbitsoftemperature.DifferentcombinationsofR1andR0canbeconfiguredas9-digit,10-digit,11-digit,and12-digittemperaturedisplay.Inthisway,theconversiontimecorrespondingtodifferenttemperatureconversionpositionscanbeknown.Theresolutionsofthefourconfigurationsare0.5C,0.25C,0.125Cand0.0625C,respectively,andareconfiguredto12bitsatthefactory.3.5TemperatureReadingDS18B20isconfiguredas12bitsatthefactory,and16bitsarereadwhenreadingtemperature.Thefirst5bitsaresignbits.Whenthefirst5digitsare1,thetemperaturereadisanegativenumber;whenthecurrent5digitsare0,thetemperaturereadisapositivenumber.Themethodofreadingwhenthetemperatureispositiveis:justconvertthehexadecimalnumbertodecimal.Whenthetemperatureisnegative,thereadingmethodis:invertthehexadecimalnumber,thenadd1onthisbasis,andthenconverttodecimal.Example:0550H=+85degrees,FC90H=-55degrees.IVDS18B20WorkingPrincipleThereadandwritesequenceandtemperaturemeasurementprincipleofDS18B20arethesameasDS1820.Onlythenumberofdigitsofthetemperaturevalueobtainedvarieswiththeresolution.Andthedelaytimeduringtemperatureconversionisreducedfrom2sto750ms.ThetemperaturemeasurementprincipleofDS18B20isshowninFigure3.Figure3.DS18B20TemperatureMeasurementPrincipleDiagramTheoscillationfrequencyofthecrystaloscillatorwithlowtemperaturecoefficientinthepictureislittleaffectedbytemperature.Itisusedtogenerateafixedfrequencypulsesignalandsendittothesubtractioncounter1.Thehightemperaturecoefficientcrystaloscillatorchangesitsoscillationfrequencysignificantlywithtemperaturechanges.Atthesametime,thegeneratedsignalisusedasthepulseinputofthesubtractioncounter2.Thefigurealsoimpliesacountinggate.Whenthecountinggateisopened,DS18B20countstheclockpulsesgeneratedbythelowtemperaturecoefficientoscillatortocompletethetemperaturemeasurement.Theopeningtimeofthecountinggateisdeterminedbythehightemperaturecoefficientoscillator.Beforeeachmeasurement,firstputthebasecorrespondingto-55℃intothesubtractioncounter1andthetemperatureregisterrespectively.Thesubtractioncounter1andthetemperatureregisterarepresettoabasevaluecorrespondingto-55℃.Thesubtractioncounter1subtractsthepulsesignalgeneratedbythelowtemperaturecoefficientcrystaloscillator.Whenthepresetvalueofthesubtractioncounter1isreducedto0,thevalueofthetemperatureregisterwillincreaseby1,thepresetofthesubtractioncounter1willbereloaded,andthesubtractioncounter1willrestartcountingthepulsesignalsgeneratedbythelowtemperaturecoefficientcrystaloscillator.Thisloopuntilthesubtractioncounter2countsto0,stoptheaccumulationofthetemperatureregistervalue.Thevalueinthetemperatureregisteristhemeasuredtemperatureatthistime.Figure4.DS18B20Theslopeaccumulatorisusedtocompensateandcorrectthenonlinearityinthetemperaturemeasurementprocess,anditsoutputisusedtocorrectthepresetvalueofthesubtractioncounter.Aslongasthecountinggateisnotclosed,repeattheaboveprocessuntilthetemperatureregistervaluereachesthemeasuredtemperaturevalue.ThisisthetemperaturemeasurementprincipleofDS18B20.Inaddition,becausetheDS18B20single-wirecommunicationfunctioniscompletedintimesharing,ithasastrictconceptoftimeslots.Therefore,thereadandwritetimingisveryimportant.VariousoperationsofthesystemtoDS18B20mustbecarriedoutaccordingtotheagreement.Theoperatingprotocolis:initializeDS18B20(sendresetpulse)sendROMfunctioncommandsendmemoryoperationcommandprocessdata.ThetimingdiagramofvariousoperationsisthesameasthatofDS1820.VConclusionInconclusion,thisblogsummarizesthefollowing3aspectsofDS1820:Features,structureandworkingprinciple.DS1820mainlychangesitsappearanceaccordingtodifferentapplications.ThepackagedDS18B20canbeusedinvariousnon-limitingtemperatureapplications.Includingcabletrenchtemperaturemeasurement,blastfurnacewatercirculationtemperaturemeasurement,boilertemperaturemeasurement,machineroomtemperaturemeasurement,agriculturalgreenhousetemperaturemeasurement,cleanroomtemperaturemeasurement,ammunitionstoragetemperaturemeasurement,etc.Inaddition,DS1820isabrasion-resistantandimpact-resistant,smallinsize,easytouse,anddiverseinpackaging,suitablefordigitaltemperaturemeasurementandcontrolofvariousnarrowspaceequipment.FAQWhatisDS18B20temperaturesensor?TheDS18B20isa1-wireprogrammabletemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.HowdoestheDS18B20work?Itworksontheprincipleofdirectconversionoftemperatureintoadigitalvalue.IsDS18B20athermistor?Athermistorisathermalresistor-aresistorthatchangesitsresistancewithtemperature....Thermistorshavesomebenefitsoverotherkindsoftemperaturesensorssuchasanalogoutputchips(LM35/TMP36)ordigitaltemperaturesensorchips(DS18B20)orthermocouples.HowaccurateisDS18B20?TheDS18B20readswithanaccuracyof0.5Cfrom-10Cto+85Cand2Caccuracyfrom-55Cto+125C.Whatisds1820?TheDS18B20isonetypeoftemperaturesensoranditsupplies9-bitto12-bitreadingsoftemperature....Thecommunicationofthissensorcanbedonethroughaone-wirebusprotocolwhichusesonedatalinetocommunicatewithaninnermicroprocessor.HowdoIconnectmyDS18B20tomyRaspberryPi?OnceyouveconnectedtheDS18B20,powerupyourPiandlogin,thenfollowthesestepstoenabletheOne-Wireinterface:1.Atthecommandprompt,entersudonano/boot/config.txt,thenaddthistothebottomofthefile:2.dtoverlay=w1-gpio.3.ExitNano,andrebootthePiwithsudoreboot.WhatistheworkingprincipleofDS18B20?TheDS18B20DigitalThermometerprovides9to12-bit(configurable)temperaturereadingswhichindicatethetemperatureofthedevice.Itcommunicatesovera1-Wirebusthatbydefinitionrequiresonlyonedataline(andground)forcommunicationwithacentralmicroprocessor.Inadditionitcanderivepowerdirectlyfromthedataline(parasitepower),eliminatingtheneedforanexternalpowersupply.ThecorefunctionalityoftheDS18B20isitsdirect-to-digitaltemperaturesensor.Theresolutionofthetemperaturesensorisuser-configurableto9,10,11,or12bits,correspondingtoincrementsof0.5C,0.25C,0.125C,and0.0625C,respectively.Thedefaultresolutionatpower-upis12-bit.WheretouseDS18B20Sensor?TheDS18B20isa1-wireprogrammableTemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.Itcanmeasureawiderangeoftemperaturefrom-55Cto+125withadecentaccuracyof5C.EachsensorhasauniqueaddressandrequiresonlyonepinoftheMCUtotransferdatasoitaverygoodchoiceformeasuringtemperatureatmultiplepointswithoutcompromisingmuchofyourdigitalpinsonthemicrocontroller.HowconnectDS18B20toArduino?FirstplugthesensoronthebreadboardtheconnectitspinstotheArduinousingthejumpersinthefollowingorder:pin1toGND;pin2toanydigitalpin(pin2inourcase);pin3to+5Vor+3.3V,attheendputthepull-upresistor.OnanATMega328P,whyisaDS18B20temperaturesensorreturningincorrecttemperaturevalues?Severalpossibilities:1.Ifitisjustreadingalittlehigh,itmightbecausedbyselfheating.Addaheatsinkand/ormakemeasurementslessfrequently.2.Especiallyifthevaluesarereallywhacky,itmightbecodewitherrorsormis-wiring.Useapublishedsketchtocheckoperation.3.TheDS18B20mightbedefective.Tryanother.4.Itsaccurateto0.5C.Areyouexpectingittobemoreaccurate(likedowntotheLSBofthereadvalue)?IDescriptionInthisblog,wewillintroduceamultifunctionalelectronicthermometer.Thiskindofthermometercannotonlyaccuratelyandconvenientlymeasurebodytemperatureandfoodtemperature,butalsocanbeusedtomeasureindoorandoutdoortemperature,refrigeratortemperature,etc.Inaddition,italsohasmultiplefunctionssuchastemperaturemeasurementtiming,temperaturememory,soundprompt,backlightdisplay,andautomaticshutdown.Moreover,ithasthecharacteristicsofaccuratemeasurement,simpleoperation,portabilityandlowprice.Therefore,itcanbewidelyusedinhospitalsandhomesasageneraltemperaturemeasuringinstrument.Intermsofitsworkingprinciple,thethermometerusesthedigitaltemperaturesensorDS18B20todetecttemperatureandtransmitsthedigitaltemperaturesignaltothesingle-chipmicrocomputer.Thetemperaturevalueandmeasurementtimecalculatedandcorrectedbythesingle-chipmicrocomputeraredisplayedinrealtimebytheliquidcrystaldisplay.AtutorialonhowtousetheDallasMaxim1-WireDS18B20digitaltemperaturesensorwiththeArduino.CatalogIDescriptionIIDS18B20IntroductionIIIHardwareCircuit3.1PowerCircuit3.2DigitalTemperatureSensorandCalibration3.3MCUCircuit3.4LCDDisplay3.5AudioCircuitIVSoftwareDesignVConclusionFAQOrdering&QuantityIIDS18B20IntroductionDS18B20isasingle-wiredigitaltemperaturesensorproducedbyDALLAS.Itintegratestemperaturesensing,signalconversion,A/Dconversionandheatingfunctionsintoonechip,andbelongstoanewgenerationofintelligentdigitaltemperaturesensorswithmicroprocessors.DS18B20hasatotalof3pins,(respectivelydigitalsignalinput/output,ground,powersupply),usingTO-92small-volumepackaging.DS18B20MainSpecifications:Thetemperaturemeasurementrangeis-55℃~+125℃;Programmableto9to12bitA/Dconversionaccuracy;Thetemperaturemeasurementresolutioncanreach0.0625℃,andtheerroris0.5℃;Theworkingpowersupplycanbeintroducedattheremoteend(3-wireworkingmode)orgeneratedbyparasiticpowersupply(2-wireworkingmode);Themeasuredtemperatureisseriallyoutputwithasign-extended16-bitdigitalquantity;Eachsensorhasaunique64-bitserialnumber,whichisstoredintheROMofthesensor;Thesensoralsohastwotemperatureupperandlowerlimitstorageunits.IIIHardwareCircuitThemultifunctionalelectronicthermometerismainlycomposedofthefollowingparts:PowercircuitDigitaltemperaturesensorSinglechipcomputerLCDMonitorAudiocircuit...ItshardwarecircuitschematicdiagramisshownasinFig.1.Figure1.HardwareCircuit(rightclicktoviewbigpicture)3.1PowerCircuitU1isthemicropowerconsumptionstep-downDC/DCconverterLT3470introducedbyLinearTechnology.Here,U1convertsthe9Vdrybatteryvoltageinto5VDCvoltagetopowertheentirecircuit.So,howtostartandshutdownautomatically?WeonlyneedtopressthestartbuttonS2.Afterstarting,pin1(SHDN)ofU1getsahighlevel,pin5ofU1outputsa5VstableDCvoltage,andthethermometerstartstoworkatthistime.Then,the14-pin(P1.2)oftheone-chipcomputeroutputsahighlevelthroughD2tokeepthe1pinofU1high.When6minutesareup,the14-pinofthesingle-chipmicrocomputeroutputsalowlevel,andthe1pinofU1becomesalowlevel,andthecircuitautomaticallypowersdown.3.2DigitalTemperatureSensorandCalibrationThedigitaltemperaturesensorDS18B20isusedasatemperaturemeasuringprobetocollecttemperaturesignals.Andthedigitizedtemperaturesignalisinputthroughthe19-pin(P1.7)ofthemicrocontroller.DS18B20adopts2-wireworkingmode,andtheworkingpowerisgeneratedbyparasiticpower.Forexample,usethisthermometertomeasurethetemperatureofababy.Wecanfixthetemperatureprobeonaspecialbandageandtieittothearm.Sothatthesensorislocatedunderthearmpit.Inthisway,itcanbeavoidedthatthetemperaturemeasuringprobeisdetachedfromthetestsite.Duetoinfantactivitiesorcryingwhenmeasuringthebodytemperatureoftheinfant,andthemeasurementisconvenient.Foranotherexample,thetemperatureprobecanalsomeasureindoorandoutdoortemperature,refrigeratortemperature,etc.Thespecialprobeformeasuringfoodtemperatureadoptsnon-toxicstrawandnon-toxicsilicagelpackage,whichiseasytoclean.SinceDS18B20isintherangeof-10℃~85℃,itsmeasurementerroris0.5℃.Inordertoaccuratelymeasurebodytemperature,thisblogusesaself-madeconstanttemperaturewaterbathsystemtodeterminethetemperaturecurveofeachsensor.WecancalibratetheDS18B20accordingtothetemperaturecurvetomakethemeasurementerrorwithintherangeof25℃~50℃be0.1℃.3.2.1ConstantTemperatureWaterBathSystemTheconstanttemperaturewaterbathsystemconsistsofthefollowingthreeparts:anelectriccookerwithheatpreservation,acylindricalcopperbodywithgoodheatconduction,andanautomatictemperaturecontroller.Weneedtomake50roundholeswithadiameterof5mmandaheightof30mmonacylindricalcopperbodywithadiameterof120mmandaheightof80mm.Inthisway,thetemperaturesensorcanbefixedandthetemperatureofallthesensorsinthecopperbodycanbekeptconsistent.Putthecylindricalcopperbodyintotheelectriccooker,andadddistilledwatertosubmergethecopperbody.3.2.2DS18B20ActualTemperatureCurveMeasurementInsertmultipleencapsulatedsensorstobetested(nomorethan49)intothesmallholesofthecopperbodyoftheconstanttemperaturewaterbath;Insertthehigh-precisiondigitalthermometerintothesmallholeofthecopperbodytoaccuratelymeasurethecurrenttemperature;Thewiresofallsensorsareledoutthroughtheuppercoverholeoftheelectriccookerandconnectedtotheuppercomputer.Covertheelectriccookerwithheatpreservationmaterial;Turnonthepower,changethetemperaturesettingoftheautomaticthermostat,andcontrolthetemperatureoftheconstanttemperaturewaterbath;Monitorthetemperaturevalueofthedigitalthermometer.Wheneverthespecifiedtemperaturevalueisreached,starttheuppercomputertemperaturemeasurementprogramandsimultaneouslymeasurethecurrenttemperatureofallthesensorstobetested;From25℃~60℃,measure1setofdataevery5℃,andautomaticallygeneratetheactualtemperaturecurveofeachsensor.3.2.3CorrectionofDS18B20Byanalyzingthemeasuredtemperaturecurveofthesensor,wecanfindthatwithintherangeof25℃~50℃,theerroris-0.1℃~-0.3℃.Inthedesignofthisblog,thecurrenttemperaturevalueofDS18B20plus0.2℃isusedastheactualmeasuredtemperature,sothatthemeasurementerrorintherangeof25℃~50℃isreducedto0.1℃.3.3MCUCircuitThemicrocontroller(U2)isthecorecomponentofthethermometer.Ithasthefollowingfunctions:Temperaturesignalreading,processingcalculation,correctionTemperaturemeasurementtimingTemperaturememorySoundprompt,Automaticshutdown...ThisdesignadoptsAT89C2051single-chipmicrocomputerproducedbyAmericanATMELcompany.Itisabuilt-inflashmemorymicrocontrollerthatisfullycompatiblewiththeMCS-51series,withonly20pins.Itisthemostcompact,smallest,andcheapestFlashROMmicrocontrollerintheAT89C51series.Providesthefollowingstandardfunctions:An8-bitCPU;2kBflashmemory;128bytesRAM;Two16-bittimers;Acomplete8-bitbidirectionalI/Oport;5interruptsources.Afterstartingthethermometer,themicrocontrollerstartsaninternaltimertorecordthetemperaturemeasurementtime.ItalsoreadsthedigitaltemperaturesignalsentbyDS18B20,processesandcorrectsittoobtainthereal-timetemperaturevalue.ThetemperaturevalueandtemperaturemeasurementtimearesenttotheLCDdisplayviaserialcommunicationviapin1(P3.0)andpin2(P3.1);Whenthetemperaturemeasurementtimereaches5minutes,thecurrenttemperaturevalueisautomaticallyregistered,andpin11outputsalowleveltocontroltheaudiocircuittogiveasoundprompt;Whenthetemperaturemeasurementtimereaches6minutes,thesingle-chip14pinoutputslowlevel,andthethermometerisautomaticallypoweredoff.3.4LCDDisplayThisblogusesa3andahalfliquidcrystaldisplay(LCD)todisplaytemperatureandtemperaturemeasurementtime.Thedisplayhasthefollowingcharacteristics:Useglassencapsulation;Thereare5pinsintotal;SerialcommunicationWith3andahalfdisplayareaand℃unitdisplay;Functionwithbacklight;Thepowersupplyvoltagerangeis2V~5V.Thisdesignusesthemaindisplayareatoindicatethetemperature,andthesub-displayareatoindicatethetemperaturemeasurementtime.3.5AudioCircuitTheaudiocircuitconsistsofthefollowingparts:TransistorQ2(9015)resistanceR12;CapacitanceC12;BuzzerB1;Whenthepin11ofthesingle-chipmicrocomputeroutputslowlevel,thetransistorQ2issaturatedandturnedon,andthebuzzergeneratesanaudibleprompt.IVSoftwareDesignTheprogramiswrittenin89C51seriesClanguageanddebuggedonthesingle-chipsimulationsystem.TheprogramflowchartisshowninFigure2.Figure2.BlockDiagramofMainProgramAfterpower-onreset,initializetheDS18B20,inputandoutputports,timers,etc.ReadthetemperaturevalueofthelastmeasurementandstoragefromthelowertemperaturelimitstorageunitofDS18B20anddisplayitfor3seconds.StarttheinternaltimerT0ofthemicrocontrollertorecordthetemperaturemeasurementtime.Obtainthetemperaturevalueandcorrecttheerror.AccordingtothecommunicationprotocolofDS18B20,thetemperaturesignalisreadfromthesensor,thesignisdistinguished,andthetemperaturevalueisobtainedaftercalculationandprocessing.Then,add0.2Ctothetemperaturevalueastheactualtemperature,andcorrectthemeasurementerrorwithintherangeof25Cto50Cto0.1C.Displayoftemperature.Accordingtothecommunicationprotocoloftheliquidcrystaldisplay,thetemperaturevalueandtemperaturemeasurementtimearesenttothedisplayfordisplay.Themaindisplayareaindicatesthetemperature,andthesecondarydisplayareaindicatesthetemperaturemeasurementtime.Whenthetemperaturemeasurementtimereaches5minutes,the11-pinofthesingle-chipmicrocomputeroutputsalow-levelcontrolaudiocircuittoemitapromptsound,andthecurrenttemperatureissenttothelowertemperaturestorageunitofDS18B20forregistration,andsenttothesecondarydisplayareafordisplay.Whenthetemperaturemeasurementtimereaches6minutes,the14-pinofthesingle-chipmicrocomputeroutputslowlevel,andthethermometerautomaticallypowersdown.VConclusionComparedwithtraditionalthermometers,theDS18B20Multi-functionElectronicThermometerdesignedinthisbloghasmanyadvantages.Thelatterovercomesthedifficultyofreadingmercurythermometersandiseasytobebrokenandpollutetheenvironment.Atthesametime,comparedwithsimpleelectronicthermometers,multifunctionalelectronicthermometersalsoovercometheshortcomingsofpoormeasurementaccuracy.Becauseofitscompletefunctions,stableperformance,smallsize,lightweight,lowpowerconsumption,andlowprice,itcanbeusedasageneraltemperaturemeasuringinstrumentandwidelyusedinhospitalsandhomes.FAQWhatisDS18B20temperaturesensor?TheDS18B20isa1-wireprogrammabletemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.HowdoestheDS18B20work?Itworksontheprincipleofdirectconversionoftemperatureintoadigitalvalue.IsDS18B20athermistor?Athermistorisathermalresistor-aresistorthatchangesitsresistancewithtemperature....Thermistorshavesomebenefitsoverotherkindsoftemperaturesensorssuchasanalogoutputchips(LM35/TMP36)ordigitaltemperaturesensorchips(DS18B20)orthermocouples.HowaccurateisDS18B20?TheDS18B20readswithanaccuracyof0.5Cfrom-10Cto+85Cand2Caccuracyfrom-55Cto+125C.Whatisds1820?TheDS18B20isonetypeoftemperaturesensoranditsupplies9-bitto12-bitreadingsoftemperature....Thecommunicationofthissensorcanbedonethroughaone-wirebusprotocolwhichusesonedatalinetocommunicatewithaninnermicroprocessor.HowdoIconnectmyDS18B20tomyRaspberryPi?OnceyouveconnectedtheDS18B20,powerupyourPiandlogin,thenfollowthesestepstoenabletheOne-Wireinterface:1.Atthecommandprompt,entersudonano/boot/config.txt,thenaddthistothebottomofthefile:2.dtoverlay=w1-gpio.3.ExitNano,andrebootthePiwithsudoreboot.WhatistheworkingprincipleofDS18B20?TheDS18B20DigitalThermometerprovides9to12-bit(configurable)temperaturereadingswhichindicatethetemperatureofthedevice.Itcommunicatesovera1-Wirebusthatbydefinitionrequiresonlyonedataline(andground)forcommunicationwithacentralmicroprocessor.Inadditionitcanderivepowerdirectlyfromthedataline(parasitepower),eliminatingtheneedforanexternalpowersupply.ThecorefunctionalityoftheDS18B20isitsdirect-to-digitaltemperaturesensor.Theresolutionofthetemperaturesensorisuser-configurableto9,10,11,or12bits,correspondingtoincrementsof0.5C,0.25C,0.125C,and0.0625C,respectively.Thedefaultresolutionatpower-upis12-bit.WheretouseDS18B20Sensor?TheDS18B20isa1-wireprogrammableTemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.Itcanmeasureawiderangeoftemperaturefrom-55Cto+125withadecentaccuracyof5C.EachsensorhasauniqueaddressandrequiresonlyonepinoftheMCUtotransferdatasoitaverygoodchoiceformeasuringtemperatureatmultiplepointswithoutcompromisingmuchofyourdigitalpinsonthemicrocontroller.HowconnectDS18B20toArduino?FirstplugthesensoronthebreadboardtheconnectitspinstotheArduinousingthejumpersinthefollowingorder:pin1toGND;pin2toanydigitalpin(pin2inourcase);pin3to+5Vor+3.3V,attheendputthepull-upresistor.OnanATMega328P,whyisaDS18B20temperaturesensorreturningincorrecttemperaturevalues?Severalpossibilities:1.Ifitisjustreadingalittlehigh,itmightbecausedbyselfheating.Addaheatsinkand/ormakemeasurementslessfrequently.2.Especiallyifthevaluesarereallywhacky,itmightbecodewitherrorsormis-wiring.Useapublishedsketchtocheckoperation.3.TheDS18B20mightbedefective.Tryanother.4.Itsaccurateto0.5C.Areyouexpectingittobemoreaccurate(likedowntotheLSBofthereadvalue)?

293D476X96R3B2TE3-VISHAY

DescriptionDS18B20isatemperaturesensorofMaxim.Thesingle-chipmicrocomputercancommunicatewithDS18B20through1-Wireprotocolandfinallyreadthetemperature.Thehardwareinterfaceofthe1-Wirebusisverysimple,justconnectthedatapinofDS18B20toanIOportofthemicrocontroller.ThisVideoIntroducesDS18B20withDatasheetCatalogDescriptionDocumentandMediaDS18B20PinoutParametersAdvantageFeaturesApplicationsDS18B20CircuitSchematicDS18B20TemperatureSensorDataDS18B20BlockDiagramHowtousetheDS18B20SensorWheretouseDS18B20SensorProductManufacturerFAQOrdering&QuantityDocumentandMediaComponentDatasheetDS18B20DatasheetDS18B20PinoutPinNameFunctionSOSOPTO-921,2,6,7,82,3,5,6,7-N.C.NoConnection383VDDOptionalVDD.VDDmustbegroundedforoperationinparasitepowermode.412DQDataInput/Output.Open-drain1-Wireinterfacepin.Alsoprovidespowertothedevicewhenusedinparasitepowermode(seethePoweringtheDS18B20section.)541GNDGroundParametersAccuracy(C)0.5ChannelsOneInterface1-WireMultiDroppableYesOper.Temp.(C)-55to+125Package/PinsSOIC(N)/8,TO92/3,UMAX/8ParasitePwr.YesPartNumberDS18B20SensorTypeLocalTemp.Resolution(bits)9,10,11,12Temp.Thresh.Programmable(NV)AdvantageTheDS18B20digitalthermometerprovides9-bitto12-bitCelsiustemperaturemeasurementsandhasanalarmfunctionwithnonvolatileuser-programmableupperandlowertriggerpoints.TheDS18B20communicatesovera1-Wirebusthatbydefinitionrequiresonlyonedataline(andground)forcommunicationwithacentralmicroprocessor.Inaddition,theDS18B20canderivepowerdirectlyfromthedataline(parasitepower),eliminatingtheneedforanexternalpowersupply.EachDS18B20hasaunique64-bitserialcode,whichallowsmultipleDS18B20stofunctiononthesame1-Wirebus.Thus,itissimpletouseonemicroprocessortocontrolmanyDS18B20sdistributedoveralargearea.ApplicationsthatcanbenefitfromthisfeatureincludeHVACenvironmentalcontrols,temperaturemonitoringsystemsinsidebuildings,equipment,ormachinery,andprocessmonitoringandcontrolsystems.FeaturesUnique1-WireInterfaceRequiresOnlyOnePortPinforCommunicationReduceComponentCountwithIntegratedTemperatureSensorandEEPROMMeasuresTemperaturesfrom-55Cto+125C(-67Fto+257F)0.5CAccuracyfrom-10Cto+85CProgrammableResolutionfrom9Bitsto12BitsNoExternalComponentsRequiredParasiticPowerModeRequiresOnly2PinsforOperation(DQandGND)SimplifiesDistributedTemperature-SensingApplicationswithMultidropCapabilityEachDeviceHasaUnique64-BitSerialCodeStoredinOn-BoardROMFlexibleUser-DefinableNonvolatile(NV)AlarmSettingswithAlarmSearchCommandIdentifiesDeviceswithTemperaturesOutsideProgrammedLimitsAvailablein8-PinSO(150mils),8-PinSOP,and3-PinTO-92PackagesApplicationsConsumerProductsIndustrialSystemsThermallySensitiveSystemsThermometersThermostaticControlsDS18B20CircuitSchematicDS18B20TemperatureSensorDataDS18B20canachievethehighest12-bittemperaturestoragevaluethroughprogramming.Thetemperaturestoragevalueisstoredintheregisterinacomplementformat.Thereare2bytesintotal,LSBisthelowbyteandMSBisthehighbyte.Amongthem,MSbisthehighbitofthebyte,andLSbisthelowbitofthebyte.Forbinarynumbers,themeaningofthetemperaturerepresentedbyeachofthemisexpressed.Amongthem,Srepresentsthesignbit,andthelower11bitsareallpowersof2,whichareusedtorepresentthefinaltemperature.ThetemperaturemeasurementrangeofDS18B20isfrom-55degreesto+125degrees.Themanifestationoftemperaturedatahaspositiveandnegativetemperatures.Eachnumberintheregisterisdistributedlikethescaleofacaliper.Thelowestbitofthebinarynumberchanges1,whichrepresentsthemappingrelationshipofatemperaturechangeof0.0625degrees.Whenthetemperatureis0℃,thecorrespondinghexadecimalnumberis0x0000.Whenthetemperatureis125℃,thecorrespondinghexadecimalnumberis0x07D0.Whenthetemperatureisminus55℃,thecorrespondinghexadecimalnumberis0xFC90.Conversely,whenthenumberis0x0001,thetemperatureis0.0625℃.DS18B20BlockDiagramHowtousetheDS18B20SensorThesensorworkswiththemethodof1-Wirecommunication.Itrequiresonlythedatapinconnectedtothemicrocontrollerwithapullupresistorandtheothertwopinsareusedforpowerasshownbelow.Thepull-upresistorisusedtokeepthelineinhighstatewhenthebusisnotinuse.Thetemperaturevaluemeasuredbythesensorwillbestoredina2-byteregisterinsidethesensor.Thisdatacanbereadbytheusingthe1-wiremethodbysendinginasequenceofdata.Therearetwotypesofcommandsthataretobesenttoreadthevalues,oneisaROMcommandandtheotherisfunctioncommand.TheaddressvalueofeachROMmemoryalongwiththesequenceisgiveninthedatasheetbelow.Youhavetoreadthroughittounderstandhowtocommunicatewiththesensor.IfyouareplanningtointerfaceitwithArduino,thenyouneednotworryaboutallthese.Youcandevelopthereadilyavailablelibraryandusethein-builtfunctionstoaccessthedata.WheretouseDS18B20SensorTheDS18B20isa1-wireprogrammableTemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.Itcanmeasureawiderangeoftemperaturefrom-55Cto+125withadecentaccuracyof5C.EachsensorhasauniqueaddressandrequiresonlyonepinoftheMCUtotransferdatasoitaverygoodchoiceformeasuringtemperatureatmultiplepointswithoutcompromisingmuchofyourdigitalpinsonthemicrocontroller.ProductManufacturerMaximIntegratedprovideseaseofdesign,andspeedstimetomarket,throughanalogintegration.ThecompanysanalogICsofferextrafeaturesandfunctionalitycarefullydesignedtostreamlinecircuitandsimplifydesign.LooktoMaximforsolutionsforconsumerelectronics,personalcomputersandperipherals,mobiledevices,wirelessandfibercommunications,testequipment,instrumentation,videodisplays,andautomotiveapplications.Maximsanalogandmixed-signalsolutionsincludedataconverters,interfacecircuits,power,RFwirelesscircuits,clocksandoscillators,microcontrollers(MCUs),operationalamplifiers(opamps),andsensors.FAQWhatisDS18B20temperaturesensor?TheDS18B20isa1-wireprogrammabletemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.HowdoestheDS18B20work?Itworksontheprincipleofdirectconversionoftemperatureintoadigitalvalue.IsDS18B20athermistor?Athermistorisathermalresistor-aresistorthatchangesitsresistancewithtemperature....Thermistorshavesomebenefitsoverotherkindsoftemperaturesensorssuchasanalogoutputchips(LM35/TMP36)ordigitaltemperaturesensorchips(DS18B20)orthermocouples.HowaccurateisDS18B20?TheDS18B20readswithanaccuracyof0.5Cfrom-10Cto+85Cand2Caccuracyfrom-55Cto+125C.Whatisds1820?TheDS18B20isonetypeoftemperaturesensoranditsupplies9-bitto12-bitreadingsoftemperature....Thecommunicationofthissensorcanbedonethroughaone-wirebusprotocolwhichusesonedatalinetocommunicatewithaninnermicroprocessor.HowdoIconnectmyDS18B20tomyRaspberryPi?OnceyouveconnectedtheDS18B20,powerupyourPiandlogin,thenfollowthesestepstoenabletheOne-Wireinterface:1.Atthecommandprompt,entersudonano/boot/config.txt,thenaddthistothebottomofthefile:2.dtoverlay=w1-gpio.3.ExitNano,andrebootthePiwithsudoreboot.WhatistheworkingprincipleofDS18B20?TheDS18B20DigitalThermometerprovides9to12-bit(configurable)temperaturereadingswhichindicatethetemperatureofthedevice.Itcommunicatesovera1-Wirebusthatbydefinitionrequiresonlyonedataline(andground)forcommunicationwithacentralmicroprocessor.Inadditionitcanderivepowerdirectlyfromthedataline(parasitepower),eliminatingtheneedforanexternalpowersupply.ThecorefunctionalityoftheDS18B20isitsdirect-to-digitaltemperaturesensor.Theresolutionofthetemperaturesensorisuser-configurableto9,10,11,or12bits,correspondingtoincrementsof0.5C,0.25C,0.125C,and0.0625C,respectively.Thedefaultresolutionatpower-upis12-bit.WheretouseDS18B20Sensor?TheDS18B20isa1-wireprogrammableTemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.Itcanmeasureawiderangeoftemperaturefrom-55Cto+125withadecentaccuracyof5C.EachsensorhasauniqueaddressandrequiresonlyonepinoftheMCUtotransferdatasoitaverygoodchoiceformeasuringtemperatureatmultiplepointswithoutcompromisingmuchofyourdigitalpinsonthemicrocontroller.HowconnectDS18B20toArduino?FirstplugthesensoronthebreadboardtheconnectitspinstotheArduinousingthejumpersinthefollowingorder:pin1toGND;pin2toanydigitalpin(pin2inourcase);pin3to+5Vor+3.3V,attheendputthepull-upresistor.OnanATMega328P,whyisaDS18B20temperaturesensorreturningincorrecttemperaturevalues?Severalpossibilities:1.Ifitisjustreadingalittlehigh,itmightbecausedbyselfheating.Addaheatsinkand/ormakemeasurementslessfrequently.2.Especiallyifthevaluesarereallywhacky,itmightbecodewitherrorsormis-wiring.Useapublishedsketchtocheckoperation.3.TheDS18B20mightbedefective.Tryanother.4.Itsaccurateto0.5C.Areyouexpectingittobemoreaccurate(likedowntotheLSBofthereadvalue)?

IDescriptionFirst,thisblogwillintroducethe1wiredigitaltemperaturesensorDS18B20.Wemainlyintroduceitsstructure,characteristicsandworkingprinciplehere.Second,wewillintroduceatemperaturemeasurementsystembasedonDS18B20andAT89S52microcontroller.Herewemainlyintroduceitshardwarestructureandassembler.Third,therewillbepartofthesourceprogramthatisdetailedanalyed.Finally,theblogalsoexplainshowitperformstemperaturemeasurementintheagriculturalfield.Thetemperaturemeasuringdevicehasaseriesofadvantages.Suchas:highdisplayaccuracy,lowprice,simplestructure,convenientexpansionandwideapplication.DS18B20TemperatureSensorTutorialCatalogIDescriptionIIIntroductionIIIDS18B20Overview3.1DS18B20Advantages3.2DS18B20Features3.3DS18B20InternalStructureIVDS18B20MCUTemperatureMeasurementDevice4.1CompositionofSystemHardware4.2DesignofInterfaceVSoftwareDesignVIApplicationinAgriculturalProduction6.1TemperatureofMildew6.2TemperatureofAgriculturalProducts6.3TemperatureDetectioninGreenhouses6.4TemperatureofSoilVIIConclusionFAQOrdering&QuantityIIIntroductionWhatistemperature?Whataretherolesoftemperature?Temperatureisaphysicalquantitythatcharacterizesthedegreeofcoolingofanobject,anditisalsoabasicenvironmentalparameter.Inagro-industrialproductionanddailylife,themeasurementandcontroloftemperaturealwaysoccupyanextremelyimportantposition.Atpresent,atypicaltemperaturemeasurementandcontrolsystemconsistsofthefollowingparts:Analogtemperaturesensor;A/Dconversioncircuit;MCU.However,theanalogsignaloutputbytheanalogtemperaturesensorhastobeconverted.Itcaninterfacewithmicroprocessorssuchassingle-chipmicrocomputersonlyafterobtainingdigitalsignalsthroughtheA/Dconversionlink.Therefore,thehardwarecircuitstructureiscomplicatedandthecostishigh.ButDS18B20canhelpsolvethisproblem.Thenew1wiredigitaltemperaturesensorrepresentedbyDS18B20integratestemperaturemeasurementandA/Dconversion,anddirectlyoutputsdigitalquantities.Thestructureoftheinterfacecircuitwiththesingle-chipmicrocomputerissimple,anditiswidelyusedintheoccasionswithlongdistanceandmanynodes.Therefore,DS18B20hasstrongpromotionandapplicationvalue.IIIDS18B20Overview3.1DS18B20AdvantagesDS18B20type1wireintelligenttemperaturesensorproducedbyDALLASSemiconductorCompany.Itbelongstoanewgenerationofintelligenttemperaturesensorsadaptedtomicroprocessors.Comparedwiththetraditionalthermistor,ithasthefollowingadvantages:Itcandirectlyreadthemeasuredtemperature;Thereadingmodeof9-12digitscanberealizedthroughsimpleprogrammingaccordingtoactualrequirements;Itcanalsocomplete9-bitand12-bitdigitalquantitieswithin93.75msand750ms,respectively,withamaximumresolutionof0.0625C;ToreadorwritetheinformationofDS18B20,onlyoneportline(1wireinterface)isrequiredtoreadandwrite.3.2DS18B20FeaturesUnique1-WireInterfaceRequiresOnlyOnePortPinforCommunicationReduceComponentCountwithIntegratedTemperatureSensorandEEPROMMeasuresTemperaturesfrom-55Cto+125C(-67Fto+257F)0.5CAccuracyfrom-10Cto+85CProgrammableResolutionfrom9Bitsto12BitsNoExternalComponentsRequiredParasiticPowerModeRequiresOnly2PinsforOperation(DQandGND)SimplifiesDistributedTemperature-SensingApplicationswithMultidropCapabilityEachDeviceHasaUnique64-BitSerialCodeStoredinOn-BoardROMFlexibleUser-DefinableNonvolatile(NV)AlarmSettingswithAlarmSearchCommandIdentifiesDeviceswithTemperaturesOutsideProgrammedLimitsAvailablein8-PinSO(150mils),8-PinSOP,and3-PinTO-92Packages3.3DS18B20InternalStructureDS18B20adopts3-pinPR-35packageor8-pinSOICpackage.ItsDS18B20externalshapeandpindiagramareshowninFigure1.TheDS18B20internalstructureblockdiagramisshownasinFigure2.Thestructureof64-bitflashROMisshowninFigure3.Figure1.DS18B20PinoutFigure2.DS18B20InternalStructureFigure3.64bFlashROMStructureIVDS18B20MCUTemperatureMeasurementDevice4.1CompositionofSystemHardwareTheDS18B20single-chipmicrocomputerintelligenttemperaturemeasurementdeviceismainlycomposedofDS18B20temperaturesensor,AT89S52,displaymoduleandpowermodule,asshowninFigure4.Themaintechnicalindicatorsoftheproductare:MeasuringRange(℃):-55.0~+125.0MeasurementAccuracy(℃):0.1ResponseTime(s):1.5Figure4.SystemStructureDiagramThesystemusesDS18B20asatemperaturesensor.Theone-chipcomputerAT89S52ofATMELCompanyservesastheprocessor.Temperaturedisplayandlight-emittingdiodeastemperaturecontroloutputunit.Thewholesystemstrivestohaveasimplestructureandperfectfunctions.Theworkingprincipleofthesystemisasfollows:AfterDS18B20carriesonthefieldtemperaturemeasurement,themeasureddataissenttotheP3.5portofAT89S52.Thetemperaturevalueisdisplayedafterbeingprocessedbythemicrocontroller.Then,thistemperaturevalueiscomparedwiththeupperlimitofthesetalarmtemperature.Ifitishigherthanthesetupperlimit,theyellowLEDlightsup.ThemaincircuitdiagramofthesystemisshownasinFig.5.Figure5.DS18B20TemperatuerMeasurementDevice4.2DesignofInterfaceThereare2waystoconnectDS18B20tothehardwareofthemicrocontroller:Vccisconnectedtoexternalpowersupply,GNDisgrounded,andI/OisconnectedtotheI/Olineofthemicrocontroller;Useparasiticpowersupply,UDDandGNDaregroundedatthistime,andI/OisconnectedtoMCUI/O.Regardlessofthe1stor2ndpowersupplymode,theI/Olinemustbeconnectedtoapull-upresistorofabout4.7k.Figure6showsatypicalconnectionbetweenDS18B20andamicroprocessor.InFigure6(a),DS18B20adoptsparasiticpowersupply,anditsVDDandGNGterminalsarebothgrounded;InFigure6(b),theDS18B20usesanexternalpowersupply,anditsVDDterminalusesa3~5.5Vpowersupply.ThissystemadoptsthewiringmodeshowninFigure6(b),thatis,theworkingmodeofexternalpowersupply.TheactualconnectionpictureofthesystemisshowninFigure6.Figure6.PhysicalDiagramofSystemConnectionVSoftwareDesignItisworthnotingthatDS18B20hasveryhighrequirementsontwoaspects:timingandelectricalparameters.Therefore,theworkflowofthemainCPUaccessingtheDS18B20throughthesingle-businterfacemustfollowastrictoperatingsequence:first,initializetheDS18B20;second,sendROMcommands;andthen,sendfunctioncommands.Wecantakealookatthefollowingpartofthesourceprogramisasfollows:ORG0000HAJMPMAIN;StatementofMCUmemoryallocation!TEMPER_LEQU29H;usedtosavethelower8bitsofthereadtemperatureTEMPER_HEQU28H;usedtosavetheupper8bitsofthereadtemperatureFLAG1EQU38H;WhethertheDS18B20flagisdetectedPNFLAGEQU68H;DatapositiveandnegativeflagA_BITEQU20H;thesingledigitofthedigitaltubestoresthememorylocationB_BITEQU21H;ThetendigitsofthedigitaltubestorethememorylocationC_BITEQU22H;ThedecimalplacesofthedigitaltubestorethememorylocationT_INTEGEREQU26H;TheintegerpartafterFORMAT,whichintegratestwobytesoftemperatureintoonebyteT_DFEQU27H;ThedecimalfractionafterFORMAT,thedecimalfractionofnibbletemperature(therearelowfourdigits)MAIN:LCALLGET_TEMPER;CallthetemperaturereadingsubroutineLCALLT_FORMAT;Formattheread2bytetemperatureLCALLALARM;callthealarmsubroutineLCALLDISPLAY;callthedigitaltubedisplaysubroutineLCALLD1S;testafteradelayof0.5secondsAJMPMAIN;thisistheDS18B20resetinitializationsubroutineINIT_1820:SETBP3.5NOPCLRP3.5;thehostsendsoutaresetlowpulsewithadelayof537microsecondsMOVR1,#2TSR1:MOVR0,#250DJNZR0,$DJNZR1,TSR1SETBP3.5;thenpullupthedatalineNOPNOPNOPMOVR0,#25HTSR2:JNBP3.5,TSR3;waitingforDS18B20responseDJNZR0,TSR2;delayLJMPTSR4TSR3:SETBFLAG1;SettheflagbittoindicatethatDS1820existsLJMPTSR5TSR4:CLRFLAG1;cleartheflagbit,indicatingthatDS1820doesnotexistLJMPTSR7TSR5:MOVR0,#120TSR6:DJNZR0,TSR6;timingrequiresaperiodofdelayTSR7:SETBP3.5RET;readthetemperaturevalueafterconversionGET_TEMPER:;SETBP3.5LCALLINIT_1820;firstresetDS18B20JBFLAG1,TSS2RET;DeterminewhetherDS1820exists?IfDS18B20doesnotexistThenreturnTSS2:MOVA,#0CCH;skipROMmatchingLCALLWRITE_1820MOVA,#44H;IssuetemperatureconversioncommandLCALLWRITE_1820LCALLDISPLAYLCALLINIT_1820;resetbeforereadingtemperatureMOVA,#0CCH;SkipROMmatchingLCALLWRITE_1820MOVA,#0BEH;IssuereadtemperaturecommandLCALLWRITE_1820LCALLREAD_18200;savethereadtemperaturedatato28H/29HRET;WriteDS18B20subroutine(withspecifictimingrequirements)WRITE_1820:MOVR2,#8;atotalof8bitsofdata;CLRCWR1:CLRP3.5MOVR3,#6DJNZR3,$RRCAMOVP3.5,CMOVR3,#23DJNZR3,$SETBP3.5NOPDJNZR2,WR1SETBP3.5RET;readtheprogramofDS18B20,readtwobytesoftemperaturedatafromDS18B20READ_18200:MOV36H,#2;SetthehighandlowtemperatureReadfromDS18B20MOVR1,#29H;thelowbitisstoredin29H(TEMPER_L),thehighbitDeposit28H(TEMPER_H)RE00:MOVR2,#8;Thereare8bitsofdataRE01:;CLRCSETBP3.5NOPNOPCLRP3.5NOPNOPNOPSETBP3.5MOVR3,#9RE10:DJNZR3,RE10MOVC,P3.5MOVR3,#23RE20:DJNZR3,RE20RRCADJNZR2,RE01MOV@R1,ADECR1DJNZ36H,RE00RET;-----Integratethetwo-bytetemperaturereadout(pleaserefertotheinformationaboutthe2-bytetemperatureformatreadoutbyDS18B20)----------T_FORMAT:;AlarmsubroutineALARM:;DisplaysubroutineDISPLAY:;1MSdelay(calculatedby12MHZ)D1MS:MOVR7,#250llmm:nopnopDJNZR7,llmmRET;1MSdelay(calculatedby12MHZ)D1S:MovR6,#4LOOP2:movR5,#125;------------250LOOP1:LCALLD1mSDJNZR5,LOOP1DJNZR6,LOOP2RET;7-segmentdigitaltube0-9digitcommonanodedisplaycodeNUMTAB:DB0C0H,0f9H,0a4H,0b0H,99H,92H,82H,0f8H,80H,90H,0ffHXIAOSHU:DB00H,01H,01H,02H,03H,03H,04H,04H,05H,06H,06H,07H,08H,08H,09H,09HENDVIApplicationinAgriculturalProductionThistemperaturemeasurementsystemcandirectlyoutputdigitalquantities.Inaddition,ithasthecharacteristicsofsimplestructure,convenientuseandlowprice.Therefore,itcanbewidelyusedinagriculturalproduction.6.1TemperatureofMildewModerngrainwarehousescanusethissystemtomonitorthetemperatureofhundredsofpoints.Inthisway,youcaneasilygraspthetemperaturechangesatvariouspointsatdifferenttimes,increasestoragecapacity,andeffectivelyreducetheoccurrenceofmildew.6.2TemperatureofAgriculturalProductsAtpresent,low-temperaturerefrigerationmeasuresarewidelyadoptedforthepreservationoffruitsandvegetables.Thesystemcanbeinstalledinthetemperaturemeasurementpositionoftherefrigeratorcompartment.Inthisway,thetemperaturevaluecanbeconvenientlyobservedatanytimetocheckwhethertheoptimalpreservationtemperatureisreached.6.3TemperatureDetectioninGreenhousesThesystemisusedinplasticgreenhousesforgreenhousevegetablecultivationandflowerproduction.Inthisway,automatictemperaturedisplaycanberealized,andlaborandtimefortemperaturemeasurementcanbesaved.6.4TemperatureofSoilIntheprocessofplantingcropswithstrictrequirementsonsoiltemperature,thesystemcantestthechangesinsoiltemperatureasneededtofacilitatethegraspofaccuratetemperaturevalues.VIIConclusionThesingle-chiptemperaturemeasurementsystemtakesfulladvantageofthesimplicityofthehardwarestructureofDS18B20andAT89S52,using8-segmentdigitaltubedisplay,lowpriceandwideapplication.Accordingtoactualneeds,wecanalsouseLCDasadisplaydeviceorformadistributedtemperaturemeasurementandcontrolsystem.Althoughthedesigniseasytoexpand,italsohasitsshortcomings.Thesimplicityofthehardwarestructurecomesattheexpenseofsoftware.Therefore,specialattentionshouldbepaidtotheworkingsequencerequirementsofDS18B20duringprogramming.Inshort,thesystemcanbewidelyusedintemperaturemeasurementinagriculturalproduction.FAQWhatisDS18B20temperaturesensor?TheDS18B20isa1-wireprogrammabletemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.HowdoestheDS18B20work?Itworksontheprincipleofdirectconversionoftemperatureintoadigitalvalue.IsDS18B20athermistor?Athermistorisathermalresistor-aresistorthatchangesitsresistancewithtemperature....Thermistorshavesomebenefitsoverotherkindsoftemperaturesensorssuchasanalogoutputchips(LM35/TMP36)ordigitaltemperaturesensorchips(DS18B20)orthermocouples.HowaccurateisDS18B20?TheDS18B20readswithanaccuracyof0.5Cfrom-10Cto+85Cand2Caccuracyfrom-55Cto+125C.Whatisds1820?TheDS18B20isonetypeoftemperaturesensoranditsupplies9-bitto12-bitreadingsoftemperature....Thecommunicationofthissensorcanbedonethroughaone-wirebusprotocolwhichusesonedatalinetocommunicatewithaninnermicroprocessor.HowdoIconnectmyDS18B20tomyRaspberryPi?OnceyouveconnectedtheDS18B20,powerupyourPiandlogin,thenfollowthesestepstoenabletheOne-Wireinterface:1.Atthecommandprompt,entersudonano/boot/config.txt,thenaddthistothebottomofthefile:2.dtoverlay=w1-gpio.3.ExitNano,andrebootthePiwithsudoreboot.WhatistheworkingprincipleofDS18B20?TheDS18B20DigitalThermometerprovides9to12-bit(configurable)temperaturereadingswhichindicatethetemperatureofthedevice.Itcommunicatesovera1-Wirebusthatbydefinitionrequiresonlyonedataline(andground)forcommunicationwithacentralmicroprocessor.Inadditionitcanderivepowerdirectlyfromthedataline(parasitepower),eliminatingtheneedforanexternalpowersupply.ThecorefunctionalityoftheDS18B20isitsdirect-to-digitaltemperaturesensor.Theresolutionofthetemperaturesensorisuser-configurableto9,10,11,or12bits,correspondingtoincrementsof0.5C,0.25C,0.125C,and0.0625C,respectively.Thedefaultresolutionatpower-upis12-bit.WheretouseDS18B20Sensor?TheDS18B20isa1-wireprogrammableTemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.Itcanmeasureawiderangeoftemperaturefrom-55Cto+125withadecentaccuracyof5C.EachsensorhasauniqueaddressandrequiresonlyonepinoftheMCUtotransferdatasoitaverygoodchoiceformeasuringtemperatureatmultiplepointswithoutcompromisingmuchofyourdigitalpinsonthemicrocontroller.HowconnectDS18B20toArduino?FirstplugthesensoronthebreadboardtheconnectitspinstotheArduinousingthejumpersinthefollowingorder:pin1toGND;pin2toanydigitalpin(pin2inourcase);pin3to+5Vor+3.3V,attheendputthepull-upresistor.OnanATMega328P,whyisaDS18B20temperaturesensorreturningincorrecttemperaturevalues?Severalpossibilities:1.Ifitisjustreadingalittlehigh,itmightbecausedbyselfheating.Addaheatsinkand/ormakemeasurementslessfrequently.2.Especiallyifthevaluesarereallywhacky,itmightbecodewitherrorsormis-wiring.Useapublishedsketchtocheckoperation.3.TheDS18B20mightbedefective.Tryanother.4.Itsaccurateto0.5C.Areyouexpectingittobemoreaccurate(likedowntotheLSBofthereadvalue)?IntroductionTheCD4066isaquadbilateralswitchwhichcanbeappliedforswitchingofanalogsignalsanddigitalsignals.Itconsistsoffourindependentanalogswitches,eachwiththreeterminals:input,outputandcontrol.Whenthecontrolterminalisappliedwithhighpowerlevel,theswitchison.Whenthecontrolterminalisaddedwithlowpowerlevel,theswitchisclosed.Theinputterminalandoutputterminalcanbeusedinterchangeably.Thisconfigurationeliminatesthevariationoftheswitch-transistorthresholdvoltagewithinputsignaland,thus,keepstheon-stateresistancelowoverthefulloperating-signalrange.Theadvantagesoversingle-channelswitchesincludepeakinput-signalvoltageswingsequaltothefullsupplyvoltageandmoreconstanton-stateimpedanceovertheinput-signalrange.ThisarticleintroducestwoapplicationexamplesofCD4066analogswitch.CatalogIntroductionCatalogITrack-and-HoldCircuitofSignalIIInterchangingDisplayCircuitofFourWaysofElectronicSignalFAQOrdering&QuantityITrack-and-HoldCircuitofSignalFigure1.Track-and-HoldCircuitofSignalTheanalogsignalUiisfromthein-phaseinputoftheoperationalamplifier.Whenthecontrolterminaloftheanalogswitchisathighlevel,theanalogswitchison,andthecapacitorCischargedtoUi.Thisprocessiscalledthesamplingoftheinputsignal.Whenthesamplingisover,thecontrolterminaloftheanalogswitchislowlevelandtheanalogswitchisoff.Becausetheresistanceisashighas100Mwhentheanalogswitchisoff,andtheinputimpedanceofoperationalamplifierA2isalsoveryhigh,thesamplingsignalcanbemaintainedonthecapacitorC.IIInterchangingDisplayCircuitofFourWaysofElectronicSignalAgeneralsinglelineoscilloscopecanonlydisplayonecontinuoussignal.Butthisdevicecandisplayfourcontinuoussignalssimultaneouslyinasinglelineoscilloscope.Itisveryconvenienttocomparethetimerelationofdifferentsignals.Figure2.InterchangingDisplayCircuitofFourWaysofElectronicSignalFigure2isthecircuitdiagramofthedevice.ItusesaCD4017counterandoscillatortoformafour-beatcircuittocontrolthefouranalogswitchesintwoCD4066.AdjustableDClevelandoneinputsignalareaddedrespectivelyoneachpairofanalogswitches.Whenthecontrolendoftheanalogswitchishighlevel1,theanalogswitchison.TheDClevelandinputsignalaresenttothey-axisinputendoftheoscilloscope.BecausethefoursignalscorrespondtodifferentDClevels,thefoursignalsdisplayseparatelyontheoscilloscope.AlthoughthefourpairsofanalogswitchesarecontrolledbythecountersQ0,Q1,Q2,Q3outputterminal,theflickerofthewaveformissmallduetothehighoscillationfrequencyoftheoscillator.FAQWhatisCD4066?TheCD4066isaQuadBilateralSwitchIC,thatis,ithasfourswitcheswhichcanbecontrolledindividualusingacontrolpin.Theseswitchescanconductinboththedirectionsmakingitbilateral,itiscommonlyusedformultiplexinganalogordigitalsignals.HowtouseCD4066?TheCD4066ICconsistsoffourswitches.Itcanswitchanalogsignalsthroughdigitalcontrol.Ananalogsignalisappliedattheinputoftheswitch.IfaHIGHor1valueisfedintothecontrolinput,theanalogsignalwillbepassedfrominputtotheoutputofaswitch.HowCD4066work?The4066reallyfunctionsasananalogswitch.The4066isanICcomposedofswitcheswhicharedesignedtoswitchanalogsignalsviadigitalcontrol....The4066isaquadbilateralswitchcircuit,meaningthatiscomposedof4switches.Eachswitchhasasingleinputandasingleoutputterminal.WhataretheapplicationsofCD4066?TheCD4066isabi-directionalanalogswitchingICsimilartoCD4016,itiscommonlyusedinmultiplexingapplications;itcanalsobeusedtoisolatesignals.Theswitchisbilateralandhencecanbeusedforbothdigitalandanalogsignals.WhatsthedifferencebetweenCD4016andCD4066?ThemajordifferencebetweenbothisthatCD4066hasverylowinternalresistance,accordingtothedatasheetitcanonly5ofon-stateresistanceascomparedwith200ofCD4016IC.

IDescriptionIndailylife,calendarclocksareusedinvariousplaces.Suchasshoppingmalls,supermarkets,offices,homes,schools,etc.Comparedwiththetraditionalmechanicalclock,thedigitalcalendarclockhasaseriesofadvantages.Suchashighprecision,intuitivedisplay,andlonglife.ThisblogintroducesacalendarclockdesignedwithaDS1302rtcchip.DS1302RTCwithArduinoTutorialCatalogIDescriptionIISystemHardwareDesign2.1OverallStructure2.2DS1302ClockModule2.3LCD1602LCDModuleIIISystemSoftwareDesign3.1DesignofDS1302ClockSubprogram3.2LCD1602LiquidCrystalDisplaySubprogramDesignIVConclusionFAQOrdering&QuantityIISystemHardwareDesign2.1OverallStructureTakeAT89C51single-chipmicrocomputerasthemaincontroller,anduseDS1302clockchiptodesigncalendarclock.ItsoverallstructureisshowninFigure1.Figure1.OverallStructureofSystemThedesignedcalendarclockmustnotonlydisplayhours,minutesandseconds,butalsodisplayyears,months,daysandweeks.ThecoreofthesystemistheAT89C51microcontroller.Throughthesingle-chipcomputercontrolDS1302displaycalendarandtime.AndtheoutputresultisdisplayedonLCD1602liquidcrystalscreen.2.2DS1302ClockModuleTheDS1302clockchiphasthecharacteristicsoflowpowerconsumptionandhighperformance.Itcancommunicatewiththemicrocontrollerthroughasimplesynchronousserialmode,andonlyrequiresthreeI/Olines.Namelyreset(RST),I/Odatalineandserialclock(SCLK)2.2.1DS1302PinsandStructureFigure2showstheexternalpinsandfunctionsofDS1302.Figure2.DS1302PinoutVCC2-mainpowersupplypin;X1,X2-32.768kHzcrystaloscillatorpin;GND-ground;VCC1-batterypin;SCLK-serialclock;I/O-datainput/output;RST-reset.TheinternalstructureofDS1302isshowninFigure3,whichismainlycomposedofthefollowingparts:real-timeclock,datamemoryRAM,oscillatorcircuitandfrequencydivider,inputshiftregister,commandandcontrollogicandsoon.2.2.2DS1302RegistersandcontrolcommandsTheDS1302clockchiphas7registersrelatedtothecalendarclock,asshowninTable1.ThecommunicationsignalbetweenDS1302andsingle-chipmicrocomputerisrealizedthroughsimplesynchronousserialcommunication.AccordingtotheworkingtimingrequirementsofDS1302,whetherthesingle-chipmicrocomputerperformsreadoperationcommunicationfromDS1302orthesingle-chipcomputerperformswriteoperationcommunicationtoDS1302,eachcommunicationisinitiatedbythesingle-chipcomputerfirst.Inotherwords,beforeexecutingthecorrespondingreadorwriteoperation,themicrocontrollermustwriteabyteofcommandwordtoDS1302.Theeight-bitdataofthebytecommandwordisshowninFigure4.Figure4.CommandwordstructureofDS13022.3LCD1602LCDModuleTheLCD1602screencandisplaytwolinesofcharacters,16charactersperline,foratotalof32characters.Thereisan80*8-bitdisplaydatamemoryDDRAMbufferinLCD1602.SeeTable2forthecorrespondencebetweencharacterdisplaybitsandDDRAMaddress.TheaddressonthefirstlineofDDRAMstartsat00Handendsat27H.Theaddressesonthesecondlinestartat40Handendat67H,with40addressesperline.AndLCD1602displays16charactersperline.Therefore,whenwritingaprogram,selectthefirst16addressesofDDRAM.Itisimportanttonotethatthesecondlineaddressstartsfrom40H.IfyouwanttodisplayacharacterinacertainrowandcertaincolumnoftheLCD1602screen,writetheASCIIcodecorrespondingtothischaracterintothecorrespondingDDRAMaddressofacertainrowandcertaincolumn.Atthistime,youwillfindthatthecharactercannotbedisplayednormallyontheLCDscreen.Thereasonisthat80Hmustbeaddedtotheaddress.Forexample,todisplaythesymbolVinthesecondrowandsecondcolumnofthevoltageunitvolts,firstadd80HtothecorrespondingDDRAMaddress41Hinthesecondrowandsecondcolumn,thatis,C1H.ThenwritetheASCIIcode0x56correspondingtotheVcharacterintheC1Haddress.Onlythencanitbedisplayednormally.Thedisplayofothercharacterscanbededucedbyanalogyandwillnotberepeatedhere.IIISystemSoftwareDesignThesoftwareprogrammainlycompletesthefunctionsofdatareading,conversionandliquidcrystaldisplayofthecalendarclock.3.1DesignofDS1302ClockSubprogramsbitRST=P1^0;//DS1302resetportisdefinedinP1.0pinsbitSCLK=P1^1;//TheDS1302clockoutputportisdefinedontheP1.1pinsbitDATA=P1^2;//TheDS1302dataoutputportisdefinedontheP1.2pin(1)Theprogramthatthesingle-chipmicrocomputerwritesabyteofdatatoDS1302voidwright1302(unsignedchardate){Unsigneedchari;SCLK=0;//BepreparedfortherisingedgetowritedataDelaynus(2);for(i=0;i8;i++)//Writeeight-bitdatacontinuously{DATA=date0x01;//Writethebit0dataofdateintoDS1302Delaynus(2);SCLK=1;//WritedataonrisingedgeDelaynus(2);SCLK=0;//date=1;//moveoneplacetotheright}}(2)Theprogramforthesingle-chipmicrocomputertoreadabyteofdatafromDS1302unsignedcharreadd1302(void){Unsignedchari,date;Delaynus(2);for(i=0;i8;i++)//Continuouslyreadeight-bitdata{Date=1;//shiftonebittotherightif(DATA==1)//Ifthedatareadoutis1date|=0x80;//Takeout1andwriteitinthehighestbitofdateSCLK=1;//SetSCLKtoahighlevel,readoutforthefallingedgeDelaynus(2);SCLK=0;//PulldownSCLKtoformthefallingedgeofthepulseDelaynus(2);}returndate;//Returnthereaddata}3.2LCD1602LiquidCrystalDisplaySubprogramDesignThedriverprogramofLCD1602LCDscreenisrelativelycomplicatedtocompile,sowemustfigureouttheusageandmeaningofeachoperationinstructionof1602.Mainlyincludethefollowing:DisplaymodesettingDisplayswitchcontrolInputmodecontrolReaddatafromDDRAMWritedatatoDDRAMClearscreen,cursorhomesettingDataaddresspointersettingLCDscurrentbusyworksign...Partofthecodedesignisasfollows:voidLcd_initial()//InitializeLCD{E=0;Lcd_writecmd(0x38);//16*2display,5*7dotmatrixMsdelay(1);Lcd_writecmd(0x08);//displayoffMsdelay(2);Lcd_writecmd(0x01);//displayclearscreenMsdelay(2);Lcd_writecmd(0x06);//Setthecursor,afterreadingandwritingacharacter,thecursorincreasesby1Msdelay(1);Lcd_writecmd(0x0c);//displayison,nocursorisdisplayedMsdelay(1);}Figure5.HardwarepowersupplydiagramofDS1302calendarclockIntheMedwinV3.0developmentenvironment,useC51languagetocompilethesystemprogram,compileanddebug.AndloadtheHEXhexadecimalfilegeneratedbycompilingintotheMCUchip.StartthesimulationandyoucanseethesimulationrunningeffectoftheDS1302calendarclockdesignsystembasedon1602LCDdisplay.Forexample,thecurrenttimeis11:42:25onMay28,2019,andthesimulationresultisshowninFigure6.Figure6.SimulationresultsofcalendarclockItcanbeseenfromFigure6thatthecurrentdateandtimecanbedisplayedontheLCDscreeninrealtimeandaccurately.IVConclusionCalendarclocksareeverywhereinourlives.ThistexttakesAT89C51single-chipmicrocomputerasthemaincontroller,andusesDS1302real-timeclockchiptodesignthecalendarclocksystem.Inaddition,thehardwarecircuitwasdesignedintheProteussimulationsoftware,andthecorrespondingC51programwaswrittenintheMedwinV3.0developmentenvironment.Thejointuseofthesetwosoftwares,ProteusandMedWinV3.0,greatlyimprovestheefficiencyofsingle-chipsystemdesign,reducescosts,andshortensthedevelopmentcycle.FAQWhatisDS1302?DS1302isatickle-chargetimekeepingchipwhichcontainsareal-timeclock/calendarand31bytesofstaticRAM.DS1302usesserialcommunicationtointeractwithmicrocontrollers.Also,itautomaticallyadjustthedateforthemonthwithfewerdays.WhatdoesanRTCdo?Areal-timeclock(RTC)isacomputerclock(mostoftenintheformofanintegratedcircuit)thatkeepstrackofthecurrenttime.Althoughthetermoftenreferstothedevicesinpersonalcomputers,serversandembeddedsystems,RTCsarepresentinalmostanyelectronicdevicewhichneedstokeepaccuratetime.HowdoyouuseRTC?WiringItUp.5VisusedtopowertotheRTCchipwhenyouwanttoqueryitforthetime.Ifthereisno5Vsignal,thechipgoestosleepusingthecoincellforbackup.ConnectGNDtocommonpower/dataground.ConnecttheSCLpintotheI2CclockSCLpinonyourArduino....ConnecttheSDApintotheI2CdataSDApinonyourArduino.DescriptionDS1302isalow-powerreal-timeclockchipwithtricklecurrentchargingcapability.Itcantimetheyear,month,day,week,hour,minute,andsecond.ThisVideoIntroducesDS1302ArduinoRealtimeClockCatalogDescriptionDS1302PinoutDS1302DocumentsandMediaDS1302CADModelsDS1302ParametersDS1302FeaturesDS1302AdvantageDS1302ApplicationsDS1302TypicalOperatingCircuitDS1302EnvironmentalandExportClassificationsDS1302BlockDiagramHowtoUseDS1302DS1302RTCModuleDS1302CommandByteFAQOrdering&QuantityDS1302PinoutThefigurebelowshowsthepinarrangementofDS1302.Amongthem,Vcc2isthemainpowersupply,andVCC1isthebackuppowersupply.Thecontinuousoperationoftheclockcanbemaintainedevenwhenthemainpowerisoff.DS1302ispoweredbythelargerofVcc1orVcc2.WhenVcc2isgreaterthanVcc1+0.2V,Vcc2suppliespowertoDS1302.WhenVcc2islessthanVcc1,DS1302ispoweredbyVcc1.X1andX2aretheoscillationsourcesandanexternal32.768kHzcrystaloscillator.RSTisthereset/chipselectline.AlldatatransfersarestartedbydrivingtheRSTinputtohigh.RSTinputhastwofunctions:First,RSTturnsonthecontrollogic,allowingtheaddress/commandsequencetobesenttotheshiftregister;second,RSTprovidesamethodtoterminatesingle-byteormulti-bytedatatransmission.WhenRSTishigh,alldatatransfersareinitialized,allowingoperationsonDS1302.IfRSTissettoalowlevelduringthetransfer,thedatatransferwillbeterminatedandtheI/Opinwillbecomehighimpedance.Duringpower-onoperation,RSTmustremainlowbeforeVcc2.0V.OnlywhenSCLKislow,canRSTbesethigh.I/Oisaserialdatainputandoutputterminal(two-way),whichwillbedescribedindetaillater.SCLKistheclockinputterminal.PinNumberPinNameDescription1VCC2PrimaryPower-SupplyPininDualSupplyConfiguration.VCC1isconnectedtoabackupsourcetomaintainthetimeanddateintheabsenceofprimarypower.TheDS1302operatesfromthelargerofVCC1orVCC2.WhenVCC2isgreaterthanVCC1+0.2V,VCC2powerstheDS1302.WhenVCC2islessthanVCC1,VCC1powerstheDS1302.2X1ConnectionsforStandard32.768kHzQuartzCrystal.Theinternaloscillatorisdesignedforoperationwithacrystalhavingaspecifiedloadcapacitanceof6pF.Formoreinformationoncrystalselectionandcrystallayoutconsiderations,refertoApplicationNote58:CrystalConsiderationsforDallasReal-TimeClocks.TheDS1302canalsobedrivenbyanexternal32.768kHzoscillator.Inthisconfiguration,theX1pinisconnectedtotheexternaloscillatorsignalandtheX2pinisfloated.3X24GNDGround5CEInput.CEsignalmustbeassertedhighduringareadorawrite.Thispinhasaninternal40kΩ(typ)pulldownresistortoground.Note:PreviousdatasheetrevisionsreferredtoCEasRST.Thefunctionalityofthepinhasnotchanged.6I/OInput/Push-PullOutput.TheI/Opinisthebidirectionaldatapinforthe3-wireinterface.Thispinhasaninternal40kΩ(typ)pulldownresistortoground.7SCLKInput.SCLKisusedtosynchronizedatamovementontheserialinterface.Thispinhasaninternal40kΩ(typ)pulldownresistortoground.8VCC1Low-PowerOperationinSingleSupplyandBattery-OperatedSystemsandLowPowerBatteryBackup.Insystemsusingthetricklecharger,therechargeableenergysourceisconnectedtothispin.ULrecognizedtoensureagainstreversechargingcurrentwhenusedwithalithiumbattery.DS1302DocumentsandMediaDatasheetsDS1302OtherRelatedDocumentsTipsforWritingBulletproofReal-TimeClockControlCodeMfgApplicationNotesEstimatingSuperCapacitorBackupTimeonTrickle-ChargerReal-TimeClocksSelectingaBackupSourceforReal-TimeClocksOscillatorDesignConsiderationsforLow-CurrentApplicationsStateMachineLogicinBinary-CodedDecimal(BCD)-FormattedReal-TimeClocksEnvironmentalInformationHalogenCertificateRedPhosphorousCertificateMaterialDeclarationDS1302PCNObsolescence/EOLMultDevOBS15/Jul/2015HTMLDatasheetDS1302EDA/CADModelsDS1302bySnapEDADS1302byUltraLibrarianDS1302CADModelsDS1302SymbolDS1302FootprintDS1302ParametersBaseProductNumberDS1302BatteryBackupSwitchingBackupSwitchingCategoryIntegratedCircuits(ICs)Clock/Timing-RealTimeClocksCurrent-Timekeeping(Max)0.3A~1A@2V~5VDateFormatYY-MM-DD-ddFeaturesLeapYear,NVSRAM,Trickle-ChargerFunctionCalendar,Clock,NVTimekeepingRAM,TrickleChargerInterface3-WireSerialManufacturerMaximIntegratedMaximumOperatingTemperature+70CMinimumOperatingTemperature0CMountingStyleThroughHoleOperatingTemperature0C~70CPackageTubePackage/Case8-DIP(0.300,7.62mm)PackagingTubePartStatusObsoleteProductCategoryRealTimeClockRoHSNRTCBusInterfaceSerialRTCMemorySize31BSubcategoryClockTimerICsSupplierDevicePackage8-PDIPSupplyVoltage-Max5.5VSupplyVoltage-Min2VTimeFormatHH:MM:SS(12/24hr)TypeClock/CalendarVoltage-Supply,Battery2V~5.5VDS1302FeaturesCompletelyManagesAllTimekeepingFunctionsoReal-TimeClockCountsSeconds,Minutes,Hours,DateoftheMonth,Month,DayoftheWeek,andYearwithLeap-YearCompensationValidUpto2100o31x8Battery-BackedGeneral-PurposeRAMSimpleSerialPortInterfacestoMostMicrocontrollersoSimple3-WireInterfaceoTTL-Compatible(VCC=5V)oSingle-ByteorMultiple-Byte(BurstMode)DataTransferforReadorWriteofClockorRAMDataLowPowerOperationExtendsBatteryBackupRunTimeo2.0Vto5.5VFullOperationoUsesLessThan300nAat2.0V8-PinDIPand8-PinSOMinimizesRequiredSpaceOptionalIndustrialTemperatureRange:-40Cto+85CSupportsOperationinaWideRangeofApplicationsUnderwritersLaboratories(UL)RecognizedDS1302AdvantageTheDS1302trickle-chargetimekeepingchipcontainsareal-timeclock/calendarand31bytesofstaticRAM.Itcommunicateswithamicroprocessorviaasimpleserialinterface.Thereal-timeclock/calendarprovidesseconds,minutes,hours,day,date,month,andyearinformation.Theendofthemonthdateisautomaticallyadjustedformonthswithfewerthan31days,includingcorrectionsforleapyear.Theclockoperatesineitherthe24-houror12-hourformatwithanAM/PMindicator.InterfacingtheDS1302withamicroprocessorissimplifiedbyusingsynchronousserialcommunication.Onlythreewiresarerequiredtocommunicatewiththeclock/RAM:CE,I/O(dataline),andSCLK(serialclock).Datacanbetransferredtoandfromtheclock/RAM1byteatatimeorinaburstofupto31bytes.TheDS1302isdesignedtooperateonverylowpowerandretaindataandclockinformationonlessthan1W.TheDS1302isthesuccessortotheDS1202.InadditiontothebasictimekeepingfunctionsoftheDS1202,theDS1302hastheadditionalfeaturesofdualpowerpinsforprimaryandbackuppowersupplies,programmabletricklechargerforVCC1,andsevenadditionalbytesofscratchpadmemory.DS1302ApplicationsTheapplicationsofDS1302includeincorporateddigitalclocks/timersofvariousmodulesinourreallives.OtherequivalentsICsofRTCare:DS1307,DS3231,DS3232DS1302TypicalOperatingCircuitDS1302EnvironmentalandExportClassificationsAttributeDescriptionRoHSStatusRoHSnon-compliantMoistureSensitivityLevel(MSL)1(Unlimited)HowtoUseDS1302AtypicaloperatingcircuitforDS1302isgivenbelow.DS1302havetwopowerinput,oneisfromcellandotherisfromcontroller.Acrystaloscillatorof32.768kHzisusedtogeneraterequiredfrequency.ForinterfacingDataline,ResetPinandSerial-clockpinsofDS1302areconnectedwiththemicro-controller.DS1302BlockDiagramDS1302RTCModuleDS1302isatickle-chargetimekeepingchipwhichcontainsareal-timeclock/calendarand31bytesofstaticRAM.DS1302usesserialcommunicationtointeractwithmicrocontrollers.Also,itautomaticallyadjustthedateforthemonthwithfewerdays.Clockoperatesin24hror12hrformatwithanAM/PMindicator.DS1302chipisalsocommonlyusedasDS1302RTCmodulewhichcomeswitha32kHzcrystalandon-boardbatterybackupallinasmallSIPmodulethatiscompatiblewithabreadboard.DS1302moduleareusedbymakerswithArduino,RaspberryPiandotherMicro-controllers.ADS1302RTCmodulepinoutisshowninbelowimage.DS1302CommandByteAcommandbyteinitiateseachdatatransfer.TheMSB(bit7)mustbealogic1.Ifitis0,writestotheDS1302willbedisabled.Bit6specifiesclock/calendardataiflogic0orRAMdataiflogic1.Bits1to5specifythedesignatedregisterstobeinputoroutput,andtheLSB(bit0)specifiesawriteoperation(input)iflogic0orreadoperation(output)iflogic1.ThecommandbyteisalwaysinputstartingwiththeLSB(bit0).DS1302RegisterDS1302has12registers,ofwhich7registersarerelatedtocalendarandclock.ThestoreddatabitsareintheformofBCDcodes.Thecalendar,timeregistersandtheircontrolwordsareshowninTable1.Inaddition,DS1302alsohasyearregister,controlregister,chargingregister,clockburstregister,andRAM-relatedregisters.Theclockburstregistercanreadandwritethecontentsofallregistersexceptthechargingregisterinsequenceatonetime.TheDS1302andRAM-relatedregistersaredividedintotwocategories:OneisasingleRAMunit,with31intotal.Eachunitisconfiguredasan8-bitbyte,anditscommandcontrolwordisC0H~FDH.Amongthem,oddnumbersarereadoperations,andevennumbersarewriteoperations;theothertypeisRAMregistersinburstmode.Inthismode,all31bytesofRAMcanbereadandwrittenatonce,andthecommandcontrolwordsareFEH(write)andFFH(read).FAQWhatisDS1302?DS1302isatickle-chargetimekeepingchipwhichcontainsareal-timeclock/calendarand31bytesofstaticRAM.DS1302usesserialcommunicationtointeractwithmicrocontrollers.Also,itautomaticallyadjustthedateforthemonthwithfewerdays.WhatdoesanRTCdo?Areal-timeclock(RTC)isacomputerclock(mostoftenintheformofanintegratedcircuit)thatkeepstrackofthecurrenttime.Althoughthetermoftenreferstothedevicesinpersonalcomputers,serversandembeddedsystems,RTCsarepresentinalmostanyelectronicdevicewhichneedstokeepaccuratetime.HowdoyouuseRTC?WiringItUp.5VisusedtopowertotheRTCchipwhenyouwanttoqueryitforthetime.Ifthereisno5Vsignal,thechipgoestosleepusingthecoincellforbackup.ConnectGNDtocommonpower/dataground.ConnecttheSCLpintotheI2CclockSCLpinonyourArduino....ConnecttheSDApintotheI2CdataSDApinonyourArduino.

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)TDA2822TypicalApplicationinPortablePlayersTDA2822LowCostApplicationinPortablePlayersTDA28223VStereoCassettePlayerwithMototSpeedControlI.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.

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