全面了解红外遥控器

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1、全面了解红外遥控作者：SanBergmansIRRemoteControlTheoryThecheapestwaytoremotelycontroladevicewithinavisiblerangeisviaInfra-Redlight.Almostallaudioandvideoequipmentcanbecontrolledthiswaynowadays.Duetothiswidespreadusetherequiredcomponentsarequitecheap.Thusmakingitidealforushobbyiststouseforourownprojec

2、ts.ThispartofmyknowledgebasewillexplainthetheoryofoperationofIRremotecontrol,andsomeoftheprotocolsthatareinuseinconsumerelectronics.Infra-RedLightInfra-Redactuallyisnormallightwithaparticularcolour.Ushumanscan'tseethiscolourbecauseit'swavelengthof950nmisbelowthevisiblespectrum.That'soneoft

3、hereasonswhyIRischosenforremotecontrolpurposes,wewanttouseitbutwe'renotinterestedinseeingit.AnotherreasonisbecauseIRLEDsarequiteeasytomake,andthereforcanbeverycheap.Althoughwehumanscan'tseetheInfra-Redlightemittedfromaremotecontroldoesn'tmeanwecan'tmakeitvisible.Avideocameraordigitalcamera

4、can"see"theInfra-Redlightasyoucanseeinthispicture.UnfortunatelyforustherearemanymoresourcesofInfra-Redlight.Thesunisthebrightestsourceofall,buttherearemanyothers,like:lightbulbs,candles,centralheatingsystem,andevenourbodyradiatesInfra-Redlight.Infacteverythingthatradiatesheat,alsoradiatesI

5、nfra-Redlight.ThereforwehavetotakesomeprecautionstoguaranteethatourIRmessagegetsacrosstothereceiverwithouterrors.ModulationModulationistheanswertomakeoursignalstandoutabovethenoise.WithmodulationwemaketheIRlightsourceblinkinaparticularfrequency.TheIRreceiverwillbetunedtothatfrequency,soitc

6、anignoreeverythingelse.Youcanthinkofthisblinkingasattractingthereceiver'sattention.Wehumansalsonoticetheblinkingofyellowlightsatconstructionsitesinstantly,eveninbroughtdaylight.InthepictureaboveyoucanseeamodulatedsignaldrivingtheIRLEDofthetransmitterontheleftside.Thedetectedsignaliscomingo

7、utofthereceiverattheotherside.Inserialcommunicationweusuallyspeakof'marks'and'spaces'.The'space'isthedefaultsignal,whichistheoffstateinthetransmittercase.Nolightisemittedduringthe'space'state.Duringthe'mark'stateofthesignaltheIRlightispulsedonandoffataparticul