Circuit Design _ SMN Technology

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20DEC2013LeaveacommentbySMNawaz inCircuitDesign Tags:12VDCmotor,bangladesh,Electronics,motor,speedThiscircuitisdesignedforindicatingoverspeedanddirectionofrotationofthemotorusedinminihandtools,waterpumpmotors,toysandotherappliances.A12VDCmotor(M1)iscoupledtotherotatingpartoftheappliancewithasuitablefixingarrangement.Whenthemotorrotates,itdevelopsavoltage.ThisoverspeedindicatorisbuiltaroundoperationalamplifierCA3140(IC1).Setthereferencevoltage(dependingonthedesiredspeed)byadjustingpresetVR1atpin2ofIC1.Whenthevoltagedevelopedatpin3ofIC1ishigherthanthereferencevoltageatpin2,outputpin6ofcomparatorIC1goeshightosoundpiezobuzzerPZ1andlightupLED3.TherotationindicatorcircuitisbuiltaroundANDgate74LS08(IC2).Pin2ofgateN1goeshighwhenthemotorrotatesinforwarddirection,whilepin1ofgateN1ispulledhighviaresistorR2.Whenbothpins1and2arehigh,outputpin3ofgateN1goeshightolightupLED1.Similarly,pin5ofgateN2goeshighwhenthemotorrotatesinreversedirection.Whenbothpins4and5arehigh,outputpin6ofgateN2goeshightolightupLED2.

ReferenceElectronicsForYou.

Circuit Design | SMN Technology http://smnawaztech.wordpress.com/category/circuit-design/

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20MAR2013LeaveacommentbySMNawaz inCircuitDesign Tags:bangladesh,BuckConverter,Electronics,LED,LEDDriver,Power,PWMPoormansBuckisasimple,constantcurrenthighpowerLEDdrivercapableofdriving350mAto1Aofoutputcurrent.Itiscompact(footprintis1x1.5inches)andeasytobuild,yetveryversatile.Inputpowersupplyvoltagecanbeanywherebetween5to20V(mustbehigherthantheconnectedLEDsforwardvoltagedrop).Upto5LEDscanbeconnectedinseries,andbyparallelconnectingtheseriesconnectedLEDs,upto18WtotalofLEDscanbedriven(with20Vpowersupply).Outputcurrentisconfigurable;350mA,700mA,or1Ausingincludedparts.Inboardpotentiometercanlowertheoutputcurrentdowntoabout9%levelwhichcanbeusedasadimmer.FulldimmingcontrolcanalsobedoneviathePWMinput,makingPoormansBuckaperfectbuildingblockforArduinoorothermicrocontrollerprojects.Reerence:http://www.instructables.com/id/PoormansBuck/

BuckledcircuitInductorswitchmode(buck)converterforhighenergyeciency.Widesupplyvoltagerangeof5to20V.GreatwithbatteriesaswellasACadaptors.Cyclebycycle,trueconstantcurrentcircuitConfigurableoutputcurrentupto1AUpto15Wmaximumoutputpower.(atsupplyvoltage20Vwithfive3WLEDsconnected)Currentcontrolpotentiometer(trimstheoutputcurrentdowntoabout9%)CurrentcontrolcanbeusedasabuiltindimmerOutputshortcircuitprotectionPWMcontrolinputcontrollableviaexternalmicrocontrollerincludingArduino.Compactdesignonly1x1.5x0.5inches(excludingthepotshaft)

BuckLEDDriverComponentCircuitDesignThecircuitisbuiltaroundaverycommondualcomparatorIC:LM393usingbuckconvertertopology.TheoutputLEDcurrentflowsthroughR10andR11(currentsensingresistors).TheresultingvoltageisproportionaltothecurrentaccordingtotheOhmsLaw.Thisvoltageiscomparedtothereferencevoltagebyacomparator.AstheQ3turnson,currentflowsthroughL1,LEDs,andthecurrentsensingresistors.Inductordoesnotallowcurrenttoshootupimmediately,sothecurrentincreasesgradually.Asthecurrentgetshigher,thevoltageatthecomparatorsnegativeinputpinincreasesaswell.Whenitgetshigherthanthereferencevoltage,thecomparatortrips,whichturnsoQ3,whichturnsocurrentflowingintotheinductor.


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Nowbecauseinductorischarged,currentdoesntstopflowingimmediately.CurrentthenflowsthroughtheSchottkydiodeD3topowertheLEDs.Thiscurrentgraduallydecays,andasthecurrentdecayssodoesthevoltageacrossthecurrentsenseresistors.Eventuallythecomparatorflipsbackagain,andthecyclestartsover.Thismethodofcontrollingcurrentisoftencalledcyclebycyclecurrentlimiting.(Thistruecurrentlimitingalsoworksasabuitinshortcircuitprotection.Shortingtheoutputdoesntharmthecircuit.)Thiswholecycleabovehappensveryquicklyasfastas500,000timesasecond.(ThisfrequencychangesdependingonthesupplyvoltageandLEDsforwarddropvoltageandcurrent.Anywherebetween100k500kHz.)Thereferencevoltageisgeneratedbyanordinarydiode.Forwardvoltagedropofadiodeisabout0.7Vandstaysrelativelyconstant.ThenpotentiometerVR1trimsthevoltagebecausetheoutputcurrentiscomparedagainstthisvoltage,thisinturncontrolstheoutputcurrent.Therangeofthechangeisabout11:1or100%9%.Thisisprettynarrowcomparedtoarealdimmer,howeveritisquitehandy.SometimesafterinstallingthelightyourealizethatLEDsaremuchbrighterthanexpected.Thenyoucansimplytrimthecurrentdownuntilthebrightnessisjustright.Youcanomitthepotentiometerandreplacewithresistorsifyourprojectdoesntcallforit.Thebeautyofaswitchmodecontrolleristhatitcontrolstheoutputcurrentwithoutburningtheexcessenergy.Energyfromthepowersupplyisusedonlyasmuchasneededtogettherequiredoutputcurrent.Someenergyislostinthecircuitduetotheresistanceandotherfactors,butnotthatmuch.Atypicalbuckconverterhaseciencyof90%orhigher.ThePoormansBuckdoesntgetveryhotwhenoperatingonlygetwarm.Unlikelinearregulators,noheatsinkingneeded.ReferencesBuckConverter:http://en.wikipedia.org/wiki/Buck_converter(http://en.wikipedia.org/wiki/Buck_converter)Comparator:http://en.wikipedia.org/wiki/Comparator(http://en.wikipedia.org/wiki/Comparator)ConfiguringOutputCurrentThePoormansBuckcanbeconfiguredtodeliveranywherebetween350mAto1Aofoutputcurrent.CombinationofR2svalueandwetheryouconnectR11,youcanchangetheoutputcurrent.Herearesamplesofafewconfigurations:

OutputCurrent R2Value UseR11?350mA(1WLED) 10k No700mA(3WLED) 10k Yes1A(5WLED) 2.7k Yes

ThecurrentcontrolpotVR1controlstheoutputcurrentfromabout9100%ofthesetcurrent.Soifyouconfiguretheunittodeliver1A,youcantrimitdowntoabout90mAjustbyturningthepot.Thiscanbeusedasadimmer(althoughthedimmingrangeissomewhatlimited).PWMInputThebasicoperationofthiscircuitcanbedonewithjustonecomparator.HoweverthemostpopularcomparatorIC(LM393)hastwocomparatorsinit.Soratherthanlettingoneofthecomparatorssittingdoingnothing,IaddedafewextrapartstomakeitPWMcontrollable.thesecondcomparatorinthe


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circuitworksasanANDgatesothatthePWMinputhastobeopen(orlogichigh)fortheoutputLEDstoturnon.Usuallythispincanbeleftopen(noconnection)andthePoormansBuckwilloperatewithoutPWM.Butwhenyouneedthatextracontrol,youcanconnectArduinoorothermicrocontrollerandcontrolthehighpowerLEDsconnectedtoPoormansBuck.WithArduino,controlisjustaseasyasusingAnalogWrite()command.Upto6PoormansBuckcanbecontrolledbyoneArduino.ThisPWMcontrolworkswithinthecurrentlevelsetbythecurrentcontrolpot.Soifyoulowerthecurrent,thesame10%PWMlevelcanbedarker,forexample.ThesourceofthePWMcontrolisnotlimitedtomicrocontrollers.Anythingthatproducevoltagebetween0around5Vcanbeusedtoturntheoutputonando.Becreativeusephotoresistors,timers,logicICsTheupperlimitofPWMfrequencyisabout2kHz,butIthink1kHzwouldbetheoptimum.

ThisPWMinputcanalsobeusedsimplyasaremoteon/oswitch.HowevertheLEDswillbeonwhentheswitchisopen,andowhenclosedoppositeofusualpowerswitch.

Assemblyisverystraightforward.Allpartsarestandard,otheshelftype.PartsList

1or2x1ohm1WR10,R11(useonlyonetoget350mA,or500mA(withR2=2.7k)outputcurrent)1x10ohmR82x1kohmR3,R93x4.7kohmR1,R4,R73x10kohmR2,R5,R6(changeR2to2.7kohmtoget1Aoutputcurrent)1x10kohmpotentiometerVR11x22pF/35VceramiccapacitorC5(optional)2x0.1uF/35VceramiccapacitorC2,C3(optional)1x2.2uF/10VelectrolyticcapacitorC11x100uF/35VelectrolyticcapacitorC41x47100uH/1.2AL11xGPN(5551,2222,3904,etc.)Q11xGPP(5401,2907,3906,etc.)Q2


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1xPchMOSFET(NTD2955orIRFU9024)Q32x1N4148diodeD1,D21xSB140or1N5819SchottkydiodeD31xLM393dualcomparatorIC1

*Allresistorsare1/8Wor1/4Wcarbonfilmunlessotherwisenoted.SubstitutionsInductorL1canbeanywherebetween47to100uH,ratedatleastat1.2A.C1canalsobeanywherefrom1to10uF.C4canbeassmallas22uF,makingsurethatitsratedatleastat35VDC.Similarly,Q1andQ2canbealmostanygeneralpurposetypetransistors.Q3canbesubstitutedbyotherPchMOSFETscapableofminimum2Aofdraincurrent,drainsourcevoltageatleast30V,andgatethresholdlowerthan4V(logicgate).AssemblySolderthepartsstartingwiththelowestprofileones,inthiscase,IC1.Allresistorsanddiodesareinstalledvertically.Becarefulwiththeorientationofpolarizedparts,suchasdiodes,transistors,andMOSFET.

12JUN2011LeaveacommentbySMNawaz inCircuitDesign Tags:bangladesh,circuit,infraredsensor,Microcontroller,speedmeasurementsystem,speedometerADIYGatsometerwithinfraredlightbarriersThelightbarriersystemdescribedinthisarticleallowsaccuratemeasurementoftheabsolutespeedofmodelcars,planesandothermovingobjects.Ineducationandtrainingprograms,thesystemformsaperfectcontactlessspeedometer.Overtoyoutofootballandgolffanstoseewhohasthemeanestballkickorclubswing.FeaturesSpeedmeasurementwithinrangeof0.01to999km/hSpeedreadoutinm/sorkm/hon116characterdotmatrixdisplayElapsedtimereadout(max.16.777215seconds)Resolution1sLightbarrierdistanceadjustablebetween1and255cmOpticalalignmentaidSingleorcontinuousmeasurementsPoweredby9VbatteryCurrentconsumptionapprox.45mA.


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(http://postimage.org/image/1rllai5no/)Lightbarrierssystemsarearoundusinmoresituationsthanyouwouldexpect.Unnoticed,theydotheirjobscanningitemsatthesupermarketcheckout,detectingvehiclesinparkinglots,videotapesinVCRsorpersonsenteringorleavingbuildings.Usually,infraredlightisemployedbecauseitisinvisibletothehumaneyeandensuresahighdegreeofimmunityagainstinterferinglightsources.Whereassimplelightbarriersoperatingwithoutmodulation,liketheslottedlightbarriersthatcheckifaCDordiskisinsertedinthePC,haverelativelysimplefunctions,theabovementionedapplicationsinparkinglots,garagesandsecuritysystemshavefarmorechallengingrequirementsinrespectofnoiseimmunity.Thesolution,innearlyallcases,istoemploya36kHzcarrier.Thereceiversarethendesignedtorespondonlytochangesinthefrequency.Amicrocontrollersystemisthenthrownintoanalysethereceiveroutputsignalandevaluatethelengthofanyinterruption.Thisisdonetopreventerroneoustriggeringofanalarminthecaseof,say,aninsectflyingorcrawlingthroughthebarrier.

AsillustratedinFigure1,speedmeasurementusingalightbarriermaybeachievedwithjustonesenderandonereceiver.Adisadvantageofthissystemistheriskofinconsistentmeasurementresultsifthemovingobjecthasanirregularshapecausingmultiple

SeveralinfrareddetectorICshavebeenusedinmanyprojectspublishedinthismagazineoverthepastfewyears.Oneofthese,theSFH505fromSiemens,hasbecomeakindofstandardcomponentforthisfunction.TheSFH505andaotherfunctionallycompatibledevices(includingIS1UdetectorsfromSharp)arefoundinlotsofequipmentoftheconsumerelectronicsvariety.Althoughthesecomponentsareversatileandcosteective,theyarelesssuitablefortheprojectwehaveinmind,mainlybecauseofthe


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followingaspects.Theoutputresponsetimetobeaminterruptionissubjecttotoomanytimetolerancefactors;Foranacceptablerange,theinfraredlightmaynotbemodulatedallthetime.Pulsesneedtobeinsertedtopreventthecontrolelectronicsfromconsiderablyreducingthereceiversensitivity.Becauseoftherequiredpauseswithinthemodulatedsignal,reproduciblespeedmeasurementisnotfeasiblemainlybecausebeaminterruption(bytheobject)cannotbedistinguishedfromapause(insertedbythesystem).Despitetheextrahardware,thesystemproposedinFigure2isthebetteralternative,ifonlyforitsmuchhigheraccuracyandmorereliablemeasurementresultswhenusedtomeasurethespeedofobjectspassingthroughthebarrier.Tomakereallifeapplicationoftheabovesystemasflexibleaspossible,thedesignallowstheusertosetupthelengthofthepaththeobjecthastotravelalonginordertointerruptthetwolightbeams.Inpractice,thisisdonebyplacingthefirstandsecondbarrieratasuitabledistancefromeachother,andinformingthesystemabouttheexactdistancebeforethemeasurementcommences.SenderandreceiverTheKodenshiCompanyfromKoreahavedevelopedtwomodules(EmitterPIE310andDetectorPID310)forlightbarrierapplications.Thankstotheirhighdegreeofintegration,thesemodulescontainallcomponentsnecessaryforalongrangeyetnoiseimmunelightbarriersystem.Fromthedatasheets(inKorean)wewereabletodistilthefollowingimportantcharacteristics:IRLEDwithinternalmodulationandassociatedphotodetectorinaseparate,compactcasewithalenssystem.Sizeapprox.1787mmRange1to8.5m(3to25ft.)ActivelowopencollectoroutputControlinputonsenderHighlytolerantofambientlightthankstoopticalfiltersandinternalmodulation.LowcostsensorapplicationsatlargedistancesSuitableforuseinReflectionmode3pinwireconnectionSupplyrequirements5V/5mA(receiver)and5V/15mA(transmitter)Switchingspeed0.5msHalfsensitivityangle+/5degreesoperatingtemperature10to+60CThemodules,whosepinoutsaregiveninFigure3,areintendedforuseinpapersensors,distancesensorsinreflectionmode,counterandregistrationsystemsorproximitydetectors.Thesimplicity,relativelylowcostandreliabilityofthecircuittobediscussedismainlyduetothesereadymademodulesfromKodenshi.Themoduleconnectioncablesareavailableasaccessories.Theyareessential,however,becauseitisverydiculttosolderwirestothedevicepins.


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ThemicrocontrollerByvirtueofaprogrammedmicrocontroller,thecircuitisrelativelyuncluttered.ThecircuitshowninFigures3and4consistsoftwolightbarriers,adisplayforthespeedreadoutandsystemsettings,fourpushbuttonsand,ofcourse,thecentralmicrocontroller.Alowpower,lowprice,lowpincountmicrocontroller(tousethewordsofPhilips)type87LPC762isemployedhere.Thisdeviceisbasedonthewellestablished8051architecture.Here,itisclockedat6MHz(1uscycletime),inviewofthecalculationloadandthehightimeresolutionrequiredbythesystem.

Themainfeaturesofthe87LPC762maybefoundinthedatasheet:2KBytesROM128BytesRAM32BytesuserprogrammableEEPROM2.7to6VsupplyvoltageTwo16BitTimer/CounterIntegratedResetInternalRCoscillatorforoptionaluse20mAdrivecapacityatallportpinsupto18I/Opins2analoguecomparatorsI2CinterfaceFullduplexUARTSerialincircuitprogrammableBecausetherearenotenoughI/OpinsavailablefordirectconnectionofthepushbuttonsandtheLCDin8bitmode,somepinshavebeengivenadoublefunctionbycleverprogramming.Pushbuttonconnections+andshareaportpinlinewiththedisplaycontrollines.Forthedisplaycontrolthese


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pinsareprogrammedaspushpullstages,whileinputonlymodeisbrieflyselectedwhenpollingthepushbuttonsforactivity.ResistorsR1andR2limittheshortcircuitcurrentwhenapushbuttonispressedatthesametimethedisplayisbeingcontrolled.Thelightbarrierreceiveroutputsaredirectlyconnectedtothemicrocontrollerinputs.Theinternalpullupresistorsareusedbecausethelightbarrierhasanopencollectoroutput.CircuitandconstructionThedisplayisanalphanumericdotmatrixtypewithonelineof16characters.Thisversionshouldbewidelyavailablebecauseitrepresentsakindofindustrystandard,includingtheuseoftheHitachiHD44780LCDcontrolleranditscommandset.Thedisplayrequiresasinglesupplyvoltageof+5V(noadditional5V!).Importantthingstowatchoutforarethepinoutandwithittheorderoftheconnections(upperleftcorner),aswellastheinternalRAMaddressallocation.OnlyLCDmoduleswithamultiplexrateof1/16havetherightaddressorder00,01,02,03,04,05,06,07,40,41to47.Althoughmoreinformationhastobedisplayedthancanbefittedonasingleline,a1linedisplayisusedinsteadofa4linetypebecausetheuserispromptedtopressabuttontoviewtheinformation.ThedisplaycontrastisadjustedbypresetP1.TurnP1acrossitsfulltravelifnocharactersaredisplayedwhenthecircuitisfirststartedandyouaresurethatnoconstructionerrorshavebeenmade.Asusualthecircuitispoweredviaa7805fixedvoltageregulator.Withsimplicityandcostinmind,thesenderandreceiverareconnectedtotheprocessingelectronicsviaasingle9waysubDconnector.ThelightbarrierwireshavetobeconnectedinaccordancewithFigure3.Inthisapplication,thesendercontrolinputsarenotusedtheyareeithernotconnectedorhardwiredtoground.PracticaluseToenablethecontrollertorespondinstantlytochangesatthelightbarrieroutputs,themeasurementroutineisinterruptdriven.Asaconsequence,portpinsP1.3andP1.4arenotconstantlypolledbythesoftware.Instead,apieceoflogicinsidethemicrocontrollerissetuptocontrolthetimemeasurement.Theadvantageofthisarrangementisthatinadditiontoinstantreactiontoevents,thesoftwarehassucientsparetimeforotherchoreslikedrivingthedisplayandscanningthepushbuttonsforactivity.ThisisnotpossiblejustlikethatandusinganyinputpinP1.3andP1.4arespeciallypreparedtohandlesuchexactingjobs.Atafallingpulseedge,theinternalprogramhaltsinstantlyandjumpstoaspecialroutinewrittentohandlethetaskonhand.Anyspeedmeasurementstartswhenthefirstlightbeamisinterrupted.Instantly,the16bitcounterinsidethemicrocontrollerisstartedatacountrateof1us.Overflowsthatoccurareaddedinan8bitregister,allowingamaximumperiodof16.777215secondstobemeasured.Theobjectvelocity,v,isthencomputedbythemicrocontrollerusingthesimpleequationv=d/tusingthedistance,d,betweenthebarriersandthetimerstate,t.Usingthedefaultsettings,thesoftwareassumesabarrierdistanceof0.1m,areadoutinm/sandcontinuousasthemeasurementmode.Tosimplifythecalculations,theresolutionislimitedtotwodecimals,whichshouldbesucientinmost


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ifnotallcases.Ifyourequirebetteraccuracy,getoutyourpocketcalculatorandusetheindicatedcountervalueandthelightbarrierdistance.Youshould,however,alwaystakethe0.5msdelayofthelightbarriersintoaccount.Note,however,thatthisdelayisaboutequalonbothreceiverssothatshouldnotbeaproblem.Moreimportantthantweakingthenumbersbehindthedecimalpoint(orcomma,inthiscase)istomakesurethatthesendersandreceiversarecorrectlyalignedandproperlysecured,whiletheirdistanceremainseasilyadjustableforthespeedmeasurementyouwanttoperform.Withthebarriersinstalled,connectedupandthesoftwareswitchedon,thesoftwaretakesover,guidingyouthroughamenuinwhichvariousoptionsmaybeselected.MODEkeyPressthiskeytostepthroughthefourmenuitems,asfollowsTESTDISTANCEMODESPEEDTESTTESTcausesthestateofthelightbarrierreceiverstobedisplayed.ThemessageOKmeanshighlevelmeasuredandindicatesthatthelightbeamfromthesenderisbeingpickedup.ALowindicatesthatthebeamiseitherinterruptedornotproperlyaimedatthereceiver.Beforeanymeasurementisstarted,bothoutputsshouldflagOK.Afteraresetorafterthecircuitisswitchedon,thismenualwaysappearsfirst.ItshouldbenotedthataunconnectedlightbarrierreceiverwillalsocauseOKtobedisplayed,simplybecauseoftheinternalpullupresistorsatthecontrollerinputs.Therefore,asasecuritycheck,makeahabitofinterruptingthelightbeammanuallywhilewatchingthedisplayindication.Anothersourceoferrorsisthelobeshapeofthelightbeam,whichmayreachtheotherreceiverwhenthebarriersareplacedatarelativelysmalldistance.WhenDISTANCEisdisplayed,thevaluetobeprocessedbythemicrocontrollerisenteredincentimetres.Thedefaultvalueis10cm.Asamatterofcourse,youhavetomakesurethatthedisplayedvalueistherealdistancebetweenthelightbarriers.MODEallowsyoutoselectthemeasurementmode:SINGLEperformsjustonemeasurement.Whenthebarriersaretriggeredagain,nonewmeasurementisperformed.CONTINUOUSenablesresultstoberefreshedbyanynewmeasurement.Thecurrentmeasuredvalueisalwaysoverwritten.SPEEDindicatesthemeasuredvelocityoftheobject.Threeunitsareavailabletochoosefrom:m/s,km/handseconds.Themaximumtimeis16.777215seconds.ExceedingthisvaluecausesERRORtobedisplayed.

STARTkeyThispushbuttonisonlyreadinSINGLEmode.Itlaunchesameasurementwhenneitherofthelightbarriersisinterrupted.ThedisplaythenindicatesREADY.Ifabarriersfailstodetectasignal,thesoftwarejumpstoTEST,wheretheusercansee


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whatswrong.Oncetheproblemissolved,anotherpressoftheSTARTkeycausestheSPEEDorDISTANCEmenutoappear.+andkeysIntraditionalfashionthesetwokeysareusedtoselectdierentparametersintheindividualmenus.IntheDISTANCEmenu,forexample,thekeysallowvaluesbetween1cmand255cmtobesetup.IntheMODEmenu,bothkeyshavethesamefunction,changingbetweenSINGLEandCONTINUOUS.IntheSPEEDmenu,finally,the+andkeysallowyoutochoosebetweenareadoutinm/s,km/horseconds(thelatterfortheconvenienceofpocketcalculatorusers).Components

Resistors:R1,R2=4kOhm7R3=10kOhmR4,R5=100kOhmP1=10kOhmpresetCapacitors:C1=10F16VC2C5=100nFC6,C7=15pFSemiconductors:IC2=7805IC3=87LPC762,programmed,downloadfromRapidsharepassword01020641Speed_Measurement_System_Hex_File(https://rapidshare.com/files/3021917140/Speed_Measurement_System.rar)Miscellaneous:K1=9waysubDsocket(female),angledpins,PCBmountK2=14waySILpinheaderS1S4=pushbuttonS5=on/oswitchX1=6MHzquartzcrystalLCDdotmatrixdisplay,116characters,44780compatible2combinationsofIRSenderPIE310andIRreceiverPID3104moduleconnectingcables


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Reference

Dotmatrixdisplay:http://www.datamodul.de/displaytechnik/lcdalpha/bt_11608.htm(http://www.datamodul.de/displaytechnik/lcdalpha/bt_11608.htm)http://electronicassembly.de/(http://electronicassembly.de/)http://www.schukat.com(http://www.schukat.com)(DisplayFa.Sharp)Microcontroller:wwwus.semiconductors.philips.com/mcu/Lightbarrierdatasheets:http://www.kodenshi.com/pdfs/g1.pdf(http://www.kodenshi.com/pdfs/g1.pdf)Electro032002

10JUN2011LeaveacommentbySMNawaz inCircuitDesign Tags:bangladesh,circuit,Microcontroller,Waterlevelcircuit,waterlevelindicatorMostwaterlevelindicatorsforwatertanksarebaseduponthenumberofLEDsthatglowtoindicatethecorrespondinglevelofwaterinthecontainer.Hereitispresentasadigitalversionofthewaterlevelindicator.


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Itusesa7segmentdisplaytoshowthewaterlevelinnumericformfrom0to9.Thecircuitworkso5Vregulatedpowersupply.ItisbuiltaroundpriorityencoderIC74HC147(IC1),BCDto7segmentdecoderICCD4511(IC2),7segmentdisplayLTS543(DIS1)andafewdiscretecomponents.Duetohighinputimpedance,IC1senseswaterinthecontainerfromitsnineinputterminals.Theinputsareconnectedto+5Vvia560kiloohmresistors.Thegroundterminalofthesensormustbekeptatthebottomofthecontainer(tank).IC74HC147hasnineactivelowinputsandconvertstheactiveinputintoactivelowBCDoutput.TheinputL9hasthehighestpriority.TheoutputsofIC1(A,B,CandD)arefedtoIC2viatransistorsT1throughT4.ThislogicinverterisusedtoconverttheactivelowoutputofIC1intoactivehighforIC2.TheBCDcodereceivedbyIC2isshownon7segmentdisplayLTS543.ResistorsR18throughR24limitthecurrentthroughthedisplay.Whenthetankisempty,alltheinputsofIC1remainhigh.Asaresult,itsoutputalsoremainshigh,makingalltheinputsofIC2low.DisplayLTS543atthisstageshows0,whichmeansthetankisempty.Similarly,whenthewaterlevelreachesL1position,thedisplayshows1,andwhenthewaterlevelreachesL8position,thedisplayshows8.Finally,whenthetankisfull,alltheinputsofIC1becomelowanditsoutputgoeslowtomakealltheinputsofIC2high.DisplayLTS543nowshows9,whichmeansthetankisfull.AssemblethecircuitonageneralpurposePCBandencloseinabox.Mount7segmentLTS543onthefrontpanelofthebox.ForsensorsL1thoughL9andground,usecorrosionfreeconductivemetal(stainlesssteel)strips.Reference

http://www.electronicsforu.com(http://www.electronicsforu.com)

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