单片机控温系统英文文献

0020-4412/02/4503-$27.00©2002ŒAIKÒNauka/Interperiodica”0408InstrumentsandExperimentalTechniques,Vol.45,No.3,2002,pp.408–411.TranslatedfromPriboryiTekhnikaEksperimenta,No.3,2002,pp.127–130.OriginalRussianTextCopyright©2002byTeplov,Anisimov.Thisworkdescribesathermostattingsystemforatemperaturerangeof–20to+70¡Cwithauniversalcontrolcircuitbasedonasingle-chipmicrocomputer.Tocoolandheataheatcarrier,thermoelectricmodulesbasedonthePeltiereffectareused[1,2].ThedescribedliquidthermostattingsystemisdevelopedforaNMRrelaxometer–diffusometerbutcanbeusedtocontroltemperaturesofanyvolume-comparableobjectsalmostwithoutmodifications.AsappliedtotheNMRsetup,theblockdiagramofthesystemisshowninFig.1.Thetemperature-controlledobjectisanampoulewiththestudiedsample1placedintothesensoroftheRFspectrometerbetweenthepolesofmagnet2.Thetemperatureoftheampouleiscontrolledbytheliquidheatcarriercirculatinginaclosedsealedcontour.Thesealedliquidcontourofthethermostattingsystemcon-sistsofthermojacket3surroundingtheampoulewiththesampleandathermounit(designatedinFig.1byadottedframe),whichcontainstheelectricheater4,thermoelementsbasedonthePeltiereffect5,pump6,heat-carrier-volumevariationcompensator7,andcon-nectingpipes8.Theelectronicsectionofthesystemconsistsofathermalconverter9,personalcomputer10beingthepartoftheNMRsetupandcontrollingtheoperationofitsunits11,andcontrolandinterfacecircuits12basedonasingle-chipmicrocomputer(SCM).Intheprocessoftheoperation,theSCMoftheunit12calculatestheoptimumpoweroftheheaterandcoolerfromthecur-renttemperaturedataobtainedfromthethermalcon-verter9placednearthesampleintheNMRsensor.Theheater4togetherwiththePeltier-effect-basedthermoelements5heatstheheatcarrier,while,inthecoolingmode,theelectricheaterautomaticallyturnsoff,andthePeltier-effect-basedthermoelementscon-nectedintheoppositepolaritycooltheheatcarrier.Thedesignversionsofthethermounitandthermojacketaredescribedin[3,4].Itisratherimportantthat,duetotheprogrammedcontrolusedinthedescribedthermostattingsystem,thetemperaturemeasurementandstabilizationpointandheatcarrierheating–coolingplacecanbeseparatedbysignificantdistances(inthiscase,thedistanceis250–300mm).Thisissometimesnecessary,forexample,forLABORATORYTECHNIQUESThermostattingSystemUsingaSingle-ChipMicrocomputerandThermoelectricModulesBasedonthePeltierEffectV.Yu.Teplov*andA.V.Anisimov***KazanStateUniversity,ul.Kremlevskaya18,Kazan,420008Russia**KazanInstituteofBiochemistryandBiophysics,KazanScienceCentre,RussianAcademyofSciences,box30,Kazan,420111RussiaReceivedMay16,2001;infinalform,October22,2001Abstract—Aflexibletemperature-controllingsystemmatchedwiththeliquidthermostattingcircuitisbasedonasingle-chipmicrocomputer.ThermoelectricmodulesbasedonthePeltiereffectareusedforsamplecoolingandheating.Theaccuracyofthetemperaturemaintenanceisbetterthan0.1Cinarangeof–20to+70C.ThesystemisdesignedforNMRrelaxometersbutcanbealsousedtocontrolthetemperaturesofanyvolume-com-parableobjects(~50cm3).11101291NS4567823Fig.1.Blockdiagramofthethermostatingsystem:(1)ampoulewiththesamplestudied;(2)magnetoftheNMRsetup;(3)thermojacket;(4)heater;(5)Peltier-effect-basedthermoelements;(6)pump;(7)heatcarriervolumetemper-aturevariationcompensator;(8)connectingpipes;(9)ther-malconverter;(10)personalcomputer;(11)electronicunitsoftheNMRsetup;and(12)controlandinterfacesystem.INSTRUMENTSANDEXPERIMENTALTECHNIQUESVol.45No.32002THERMOSTATTINGSYSTEMUSING409theeliminationofelectromagneticinterferencescausedbyheating–coolingdevicesnearathermostaticallycontrolledobject.Theviolationofthesystemstabilityduetoatimedelayintheliquidcontourisexcludedbyanintegrallinkinthethermostattingalgorithm.AblockdiagramoftheelectroniccontrolunitforthethermostattingsystemisshowninFig.2.Thepro-grammablecontrollerofthedigitalpowerregulatorbasedontheSCM[5,6]controlsthetemperatureandkeepsitataconstantlevel.Thecurrenttemperatureofthethermostatismea-suredbytheSCMperformingthebit-by-bitbalancingalgorithmofthedigital-to-analogconverter(DAC)sig-nalandoutputpotentialofthetemperatureconverter(TC),whicharecomparedbytheanalogcomparator(AC).ThesameDACisusedtosetthepowertrans-ferredbytheactuatingamplifier(AA)totheheater.FortheDACswitching-overtimetothetemperaturemea-surementmode,thesignaldeterminingaheaterpowerlevelisstoredbythesampleandholddevice(SHD).Thelinefrequencysynchronizationunit(LFSU)deter-minesthemomentswhenthelinevoltageat50Hzcrossesthezeroaxisandisusedinthecaseofthepulse-durationortime-pulsecontroloverheatingelements.Thelogic-levelconverter(LLC)matchestheelectricpotentialsattheSCMoutputwiththerequirementsoftheRS-232serialinterface.Figure3showstheelectriccircuitofthecontrolunitofthethermostaticsystem.ItsbasiccomponentsaretheSCMM1oftheMCS-51familyand12-bitdigital-to-analogconverterM7.Theserviceprogramofthetem-peraturestabilizationsystemisinterweavedintotheexternalread-only-memory(ROM)(M2).Themicro-controlleroperationissynchronizedbytheinternaloscillatoroftheSCMwiththestabilizationfromaquartzresonatorat12MHz.ThebusformerM3andROMM2areconnectedinastandardcircuitandensureapossibilityoftheSC