LED显示屏IC脚位功能.docx
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LED显示屏IC脚位功能.docx
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LED显示屏IC脚位功能
LED显示屏IC脚位功能
Theroleof74HC245:
signalpoweramplification.
FirstfeetDIR,fortheinputandoutputportconversion,DIR=,"1"highpowersignalbythe"A"endinput"B"sideoutput,DIR="0"lowpowersignalbythe"B"endinput"A"endoutput.
2~9pin"A"signalinputandoutput,A1=B1,,,,,and,A8=B8,A1andB1areagroup,andifDIR="1","G=","0",A1enterB1output,theothersimilar.IfDIR="0","G=","0",B1enterstheA1output,whichissimilar.
The11~18pin"B"signalinputandoutputfunctionisnotthesameasthe"A"end.
NineteenthfeetG,enablingtheend,ifthefootis"1",theA/Bsideofthesignalwillnotbeconnected,onlyfor"0"whentheA/Bterminalisenabled,thefootisplayedtheroleoftheswitch.
TenthfeetGND,powerground.
TwentiethfeetVCC,powerpositive.
Theroleof74HC04:
6bitinverter.
SeventhfeetGND,powerground.
FourteenthfeetVCC,powerpositive.
ThesignalisinputfromtheAterminal,theYendisinvertingoutput,theA1andtheY1areonegroup,andtheotherisanalogous.Example:
A1="1",Y1="0","A1=""0",Y1="1",andothergroupfunctions.
Theroleof74HC138:
eightbitbinarytranslationdecimaldecoder.
EighthfeetGND,powerground.
FifteenthfeetVCC,powerpositive
Pin1~3,A,B,C,binaryinputpins.
The4~6pinchipselectsignalcontrol,onlyin4,5feetto0feet6to1,willbegatedbyA,B,Coutputsignalcontrol.Anyothercombinationwillnotbeselected,andtheY0~Y7outputwillbe"1"".
Cascadethroughcontrolgatingtoextendittosixteenbits.
Example:
G2A=0,G2B=0,G1=1,A=1,B=0,C=0,Y0is"0"and"Y1~Y7"is"1".Seethetruthtablefordetails.
Theroleof74HC595:
LEDdriverchip,8bitshiftlatch.
EighthfeetGND,powerground.
SixteenthfeetVCC,powerpositive
FourteenthfeetDATA,serialdatainput,displaydatafromthisentry,mustbeaccompaniedbyaclocksignalinordertomove.
ThirteenthfeetEN,enablethemouth,whenthepinis"1",theQA~QHportisall"1",andwhen"0",theoutputofQA~QHiscontrolledbytheinputdata.
TwelfthfeetSTB,latchthemouth,whentheinputdataintheincomingregister,onlythesupplyofalatchsignal,inordertomovedatatotheQA~QHportoutput.
EleventhfeetCLK,theclockport,eachclocksignalwillbemovedtoadataregister.
TenthfeetSCLR,resetport,aslongasthereisresetsignal,thedatamovedintheregisterwillbeempty,thescreendoesnotusethisfoot,generallyconnectedtoVCC.
NinthfeetDOUT,serialdataoutput,thedatapassedtothenext.
Fifteenth,1~7feet,paralleloutputport,thatis,thedriveroutput,drivingLED.
4953function:
linedrivetube,powertube.
TheinterioristwoCMOS,1,2,4VCC3feet,2feetfootfootcontrol,outputcontrolof7,8feet,4feet,6feet5controloutput,onlywhenthe2foot,4to0,7,8,5,6willbeoutput,otherwisetheoutputisinthehighimpedancestate.
TheroleofTB62726:
LEDdriverchip,16bitshiftlatch.
FirstfeetGND,powerground.
Twenty-fourthfeetVCC,powerpositive
SecondpinDATA,serialdatainput
ThirdfeetCLK,clockinput
FourthpinSTB,latchedinput
Twenty-thirdpinoutputcurrentadjustmentend,resistanceadjustment
Twenty-secondpinDOUT,serialdataoutput
Twenty-firstfeetEN,enableinput
Otherfunctionsaresimilartothe74HC595,exceptthattheTB62726isa16bitshiftlatchwithanoutputcurrentadjustmentfunction,butthereisnohighlevelontheparalleloutputport,onlythehighimpedancestateandthelowlevelstate.The74HC595paralleloutputporthasahighandlowleveloutput.TheTB62726issimilarinstructuretothe5026pinfunction.
Two,LEDelectronicdisplaycommonsignalunderstanding
CLKclocksignal:
ashiftpulsesuppliedtoashiftregister,eachpulsecausingdatatobemovedinoroutofonebit.Thedataonthedataportmustbecoordinatedwiththeclocksignaltotransmitthedatanormally.Thefrequencyofthedatasignalmustbe1/2timesoftheclocksignal.Inanycase,whentheclocksignalisabnormal,itwillmakethewholeboarddisplaydisorganized.
STBlatchsignal:
thedataintheshiftregisterissenttothelatch,andthedatacontentisilluminatedbythedrivecircuittodisplaytheLED.ButbecausethedrivecircuitiscontrolledbytheENenablesignal,thepremiseofitslightingmustbetomakeitopen.Thelatchsignalalsoneedstobecoordinatedwiththeclocksignaltodisplaythefullimage.Inanycase,whenthelatchsignalisabnormal,itwillcausetheentireboardtodisplayconfusion.
ENenablesignal:
fullscreenbrightnesscontrolsignal,alsousedforscreenblanking.Aslongasthedutycycleisadjusted,thebrightnesschangescanbecontrolled.Whentheenablesignalisabnormal,thewholescreenwillappeardim,dimortrailing.
Datasignal:
thedataneededtoprovidethedisplayimage.Thedatamustbecoordinatedwiththeclocksignaltotransmitdatatoanydisplaypoint.GeneralinthedisplaydatasignalRGBseparated,ifadatasignalisshortedtopositiveornegative,thenthecorrespondingcolorwillappearbrightornotbright,whenthecorrespondingdatasignalissuspendedwhenthecolordisplayisuncertain.
ABCDsignal:
onlyexistsinthedynamicscanningdisplay,ABCDisactuallyabinarynumber,Aisthelowest,ifthebinaryrepresentationofABCDsignaltocontrolthemaximumrangeis16(1111),1/4scanaslongastheABsignalcanbe,becausetheABsignalrangeis4(11).Whenthecontrolsignalisabnormal,therewillbeadislocation,highlightorimageoverlapphenomenondisplay.
Three,commontroubleshootingmeans(tools:
multimeter,electriciron,blade,screwdriver,tweezers......Etal.)
Thejudgmentproblemmustbedealtwithfirst,secondandsecond,andtheobviousandseriousfirstshouldbedealtwith.
Shortcircuitshouldbethehighestpriority.
1,resistancedetectionmethod,themultimetertodetectaresistanceprofile,anormalcircuitboardtogroundresistancevalue,andthendetectthesamepointanotherpieceofthesamecircuitboardtestandnormalresistancevaluesaredifferent,ifdifferentfromthescopeoftheproblem.
2,voltagedetectionmethod,themultimetertovoltagefiles,
Detectsthevoltageofapointatapointinasuspectedcircuit,andcompareswhetheritissimilartothenormalvalue.Otherwise,thescopeoftheproblemisdetermined.
3,shortcircuitdetectionmethod,themultimetertoshort-circuitdetectionblock(somefilesorfilediodedropresistance,withalarmfunction),checkwhetherthereisashort-circuitphenomenon,foundthatafterashortcircuitshouldgiveprioritytosolvingtheproblem,whichdoesnotburnotherdevices.Themethodmustoperateinthecaseofcircuitfailureandavoiddamagetothemeter.
4,thepressuredropmethod,themultimetertodetectdiodedropfiles,becauseallICiscomposedofmanysingleelements,onlysmall,sowhenapinitonacurrentispassed,willbeonthepinvoltagedropexists.Ingeneral,thesametypeofIC,thesamepressuredroponthepin,accordingtothevalueofthepressuredroponthepinisgoodorbad,thecircuitmustbeoperatedinthecaseofpowerfailure.Thismethodhassomelimitations,forexample,whenthedetecteddeviceishighimpedance,itcannotbedetected.
Four、themethodofunitboardroutingandthetreatmentofcommonproblems
1/16unitboardroutingmode:
1/8unitboard,3waysofrouting:
Staticlightplatewiringmode:
**thisisonlypartialrouting.Totheunknownunitboard,itisnecessarytomeasurebeforethemaintenance,toknowitswayofrunning,soastofacilitatethenextstepmaintenance,soastoimproveworkefficiency.
Boardfault:
A.thewholeboardisnotbright
1.Checkwhetherthepowersupplyisconnectedwiththesignalcable.
2,checkwhetherthetestcardtoidentifytheinterfacetestcardisnoredlightflashinglampplaterecognition,checkandtestwhetherthecomponentsofpower,orthelampboardinterfacesignalandshortcircuitleadtotheidentificationofinterface.(intelligenttestcard)
3,thereisnowelddetectionof74HC245shortcircuit,245correspondingenable(EN)signalinputandoutputpinwhetherweldorshortcircuittotheotherline.
Note:
themaincheckpowerandenable(EN)signal.
B.intheobliquescan,theregularlineisnotbright,thescreenoverlap
1,A,B,C,checktheDsignalinputportto245ifthereisadisconnectionorshortcircuit,.
2,detectionof245correspondingA,B,C,Doutputandthe138betweentheshort-circuitorweld.
3,detectA,B,C,D,whetherthesignalbetweentheshortcircuitorasignalandgroundshortcircuit.
Note:
ABCDlinesignalisdetectedmainly.
WhenC.isfull,oneormorelinesarenotlit
1,between138to4953ofthedetectioncircuitisshortcircuitorweld.
WhenD.scans,twoormorelines(usuallymultiplesof2,regular)arelitsimultaneously
1,detectA,B,C,D,whetherthesignalbetweentheshortcircuit.
2.Checkwhetherthe4953outputterminalisshortedtootheroutputterminals.
E.fulllightwithoneormoredots(irregular)notbright
1.Findthecontrolpincorrespondingtothismoduleandmeasureifitisshortedtothebank.
2.Replacemoduleorsinglelight.
WhenF.isfull,oneormorecolumnsarenotlit
1.FindthepinthatcontrolsthecolumnonthemoduleandmeasurewhetheritisconnectedwiththedriveIC(74HC595/TB62726,-)outputterminal.
G.hassingleorsinglecolumnhighlighting,orfulllinehighlighting,andisnotcontrolled
1.Checkwhetherthecolumnisshortcircuitedwiththepowersource.
2.Checkwhetherthelineisshortcircuitedwiththepowersupply.
3,replaceitsdriveIC.
TheH.displaysconfusion,buttheoutputtothenextboardisnormal
1.Checkwhetherthe245STBlatch
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