基于单片机数字电压表电路设计外文文献原稿和译文.docx
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基于单片机数字电压表电路设计外文文献原稿和译文
外文文献原稿和译文
原稿
Frontside
Copyrightofthiscircuitbelongstosmartkitelectronics。
Inthispagewewillusethiscircuittodiscussforimprovementsandwewillintroducesomechangesbasedonoriginalschematic
GeneralDescription
Thisisaneasytobuild,butneverthelessveryaccurateandusefuldigitalvoltmeter。
IthasbeendesignedasapanelmeterandcanbeusedinDCpowersuppliesoranywhereelseitisnecessarytohaveanaccurateindicationofthevoltagepresent。
ThecircuitemploystheADC（AnaloguetoDigitalConverter）I。
C.CL7107madebyINTERSIL.ThisICincorporatesina40pincaseallthecircuitrynecessarytoconvertananaloguesignaltodigitalandcandriveaseriesoffoursevensegmentLEDdisplaysdirectly.ThecircuitsbuiltintotheICareananaloguetodigitalconverter,acomparator,aclock,adecoderandasevensegmentLEDdisplaydriver.ThecircuitasitisdescribedherecandisplayanyDCvoltageintherangeof0-1999Volts。
TechnicalSpecifications-Characteristics
SupplyVoltage：
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....+/-5V（Symmetrical）
Powerrequirements：
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200mA（maximum）
Measuringrange:
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+/-0-1,999VDCinfourranges
Accuracy：
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..。
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..0。
1%
FEATURES
Smallsize
Easyconstruction
Lowcost。
Simpleadjustment.
Easytoreadfromadistance。
Fewexternalcomponents。
HowitWorks
InordertounderstandtheprincipleofoperationofthecircuititisnecessarytoexplainhowtheADCICworks.ThisIChasthefollowingveryimportantfeatures:
Greataccuracy.
Itisnotaffectedbynoise。
Noneedforasampleandholdcircuit。
Ithasabuilt—inclock.
Ithasnoneedforhighaccuracyexternalcomponents。
Schematic（fixed16-11—09）
7-segmentdisplaypinoutMAN6960
AnAnaloguetoDigitalConverter,（ADCfromnowon）isbetterknownasadualslopeconverterorintegratingconverter.Thistypeofconverterisgenerallypreferredoverothertypesasitoffersaccuracy，simplicityindesignandarelativeindifferencetonoisewhichmakesitveryreliable.Theoperationofthecircuitisbetterunderstoodifitisdescribedintwostages.Duringthefirststageandforagivenperiodtheinputvoltageisintegrated，andintheoutputoftheintegratorattheendofthisperiod，thereisavoltagewhichisdirectlyproportionaltotheinputvoltage.Attheendofthepresetperiodtheintegratorisfedwithaninternalreferencevoltageandtheoutputofthecircuitisgraduallyreduceduntilitreachesthelevelofthezeroreferencevoltage。
Thissecondphaseisknownasthenegativeslopeperiodanditsdurationdependsontheoutputoftheintegratorinthefirstperiod.Asthedurationofthefirstoperationisfixedandthelengthofthesecondisvariableitispossibletocomparethetwoandthiswaytheinputvoltageisinfactcomparedtotheinternalreferencevoltageandtheresultiscodedandissendtothedisplay。
AllthissoundsquiteeasybutitisinfactaseriesofverycomplexoperationswhichareallmadebytheADCICwiththehelpofafewexternalcomponentswhichareusedtoconfigurethecircuitforthejob。
Indetailthecircuitworksasfollows。
Thevoltagetobemeasuredisappliedacrosspoints1and2ofthecircuitandthroughthecircuitR3,R4andC4isfinallyappliedtopins30and31oftheIC.ThesearetheinputoftheICasyoucanseefromitsdiagram。
（INHIGH&INLOWrespectively）。
TheresistorR1togetherwithC1areusedtosetthefrequencyoftheinternaloscillator（clock）whichissetatabout48Hz。
Atthisclockratethereareaboutthreedifferentreadingspersecond。
ThecapacitorC2whichisconnectedbetweenpins33and34oftheIChasbeenselectedtocompensatefortheerrorcausedbytheinternalreferencevoltageandalsokeepsthedisplaysteady。
ThecapacitorC3andtheresistorR5aretogetherthecircuitthatdoestheintegrationoftheinputvoltageandatthesametimepreventanydivisionoftheinputvoltagemakingthecircuitfasterandmorereliableasthepossibilityoferrorisgreatlyreduced.ThecapacitorC5forcestheinstrumenttodisplayzerowhenthereisnovoltageatitsinput。
TheresistorR2togetherwithP1areusedtoadjusttheinstrumentduringset—upsothatitdisplayszerowhentheinputiszero。
TheresistorR6controlsthecurrentthatisallowedtoflowthroughthedisplayssothatthereissufficientbrightnesswithoutdamagingthem。
TheICaswehavealreadymentionedaboveiscapabletodrivefourcommonanodeLEDdisplays. Thethreerightmostdisplaysareconnectedsothattheycandisplayallthenumbersfrom0to9whilethefirstfromtheleftcanonlydisplaythenumber1andwhenthevoltageisnegativethe«—«sign。
Thewholecircuitoperatesfromasymmetricalρ5VDCsupplywhichisappliedatpins1（+5V），21（0V）and26（—5V）oftheIC。
Construction
Firstofallletusconsiderafewbasicsinbuildingelectroniccircuitsonaprintedcircuitboard.Theboardismadeofathininsulatingmaterialcladwithathinlayerofconductivecopperthatisshapedinsuchawayastoformthenecessaryconductorsbetweenthevariouscomponentsofthecircuit。
Theuseofaproperlydesignedprintedcircuitboardisverydesirableasitspeedsconstructionupconsiderablyandreducesthepossibilityofmakingerrors. Toprotecttheboardduringstoragefromoxidationandassureitgetstoyouinperfectconditionthecopperistinnedduringmanufacturingandcoveredwithaspecialvarnishthatprotectsitfromgettingoxidisedandalsomakessolderingeasier。
Solderingthecomponentstotheboardistheonlywaytobuildyourcircuitandfromthewayyoudoitdependsgreatlyyoursuccessorfailure。
Thisworkisnotverydifficultandifyousticktoafewrulesyoushouldhavenoproblems.Thesolderingironthatyouusemustbelightanditspowershouldnotexceedthe25Watts。
Thetipshouldbefineandmustbekeptcleanatalltimes.Forthispurposecomeveryhandyspeciallymadespongesthatarekeptwetandfromtimetotimeyoucanwipethehottiponthemtoremovealltheresiduesthattendtoaccumulateonit.
DONOTfileorsandpaperadirtyorwornouttip.Ifthetipcannotbecleaned,replaceit。
Therearemanydifferenttypesofsolderinthemarketandyoushouldchooseagoodqualityonethatcontainsthenecessaryfluxinitscore,toassureaperfectjointeverytime.
DONOTusesolderingfluxapartfromthatwhichisalreadyincludedinyoursolder.Toomuchfluxcancausemanyproblemsandisoneofthemaincausesofcircuitmalfunction。
Ifneverthelessyouhavetouseextraflux,asitisthecasewhenyouhavetotincopperwires，cleanitverythoroughlyafteryoufinishyourwork。
Inordertosolderacomponentcorrectlyyoushoulddothefollowing:
Cleanthecomponentleadswithasmallpieceofemerypaper.
Bendthematthecorrectdistancefromthecomponent’sbodyandinsertthecomponentinitsplaceontheboard.
Youmayfindsometimesacomponentwithheaviergaugeleadsthanusual,thataretoothicktoenterintheholesofthep。
c.board.Inthiscaseuseaminidrilltoenlargetheholesslightly.Donotmaketheholestoolargeasthisisgoingtomakesolderingdifficultafterwards。
Takethehotironandplaceitstiponthecomponentleadwhileholdingtheendofthesolderwireatthepointwheretheleademergesfromtheboard.Theirontipmusttouchtheleadslightlyabovethep.c。
board.
Whenthesolderstartstomeltandflowwaittillitcoversevenlytheareaaroundtheholeandthefluxboilsandgetsoutfromunderneaththesolder。
Thewholeoperationshouldnottakemorethan5seconds。
Removetheironandallowthesoldertocoolnaturallywithoutblowingonitormovingthecomponent.Ifeverythingwasdoneproperlythesurfaceofthejointmusthaveabrightmetallicfinishanditsedgesshouldbesmoothlyendedonthecomponentleadandtheboardtrack.Ifthesolderlooksdull,cracked，orhastheshapeofablobthenyouhavemadeadryjointandyoushouldremovethesolder（withapump,orasolderwick）andredoit。
Takecarenottooverheatthetracksasitisveryeasytoliftthemfromtheboardandbreakthem.
Whenyouaresolderingasensitivecomponentitisgoodpracticetoholdtheleadfromthecomponentsideoftheboardwithapairoflong—noseplierstodivertanyheatthatcouldpossiblydamagethecomponent.
Makesurethatyoudonotusemoresolderthanitisnecessaryasyouarerunningtheriskofshort—circuitingadjacenttracksontheboard,especiallyiftheyareveryclosetogether.
Whenyoufinishyourwork，cutofftheexcessofthecomponentleadsandcleantheboardthoroughlywithasuitablesolventtoremoveallfluxresiduesthatmaystillremainonit.
0-2V..。
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R3=0ohm1％
0-20V。
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R3=1.2Kohm1%
0-200V。
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..R3=12Kohm1%
0—2000V...。
....。
R3=120Kohm1%
WhenyouhavefinishedallthesolderingontheboardandyouaresurethateverythingisOKyoucaninserttheICinitsplace。
TheICisCMOSandisverysensitivetostaticelectricity。
Itcomeswrappedinaluminiumfoiltoprotectitfromstaticdischargesanditshouldbehandledwithgreatcaretoavoiddamagingit。
Trytoavoidtouchingitspinswithyourhandsandkeepthecircuitandyourbodyatgroundpotentialwhenyouinsertitinitsplace.
Connectthecircuittoasuitablepowersupplyρ5VDCandturnthesupplyon。
Thedisplaysshouldlightimmediatelyandshouldformanumber。
Shortcircuittheinput（0V）andadjustthetrimmerP1untilthedisplayindicatesexactly«0»。
Ifitdoesnotwork
Checkyourworkforpossibledryjoints，bridgesacrossadjacenttracksorsolderingfluxresiduesthatusuallycauseproblems.
Checkagainalltheexternalconnectionstoandfrom
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