rollease acmeda RS485 User manual

ROLLEASEACMEDA
RS485NetworkCablingStandard
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August2017
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CONTENTS
August2017
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Section1–RS485BUSOVERVIEW 3
Section2–NETWORKTOPOLOGIES 4
Section3–DIMENSIONALLIMITATIONS 5
Section4–CABLETYPES 7
Section5–PINOUTDEFINITION 8
Section6–GROUNDCONNECTIONSTRATEGY 10
Section7–INSTALLATIONOPTIONS 12
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DISCLAIMER
INTRODUCTION
ThisproductspecificationsmanualhasbeenproducedbyRolleaseAcmedatosupplythenecessaryinformationforsafeandcorrectassemblyandinstallationofthissystem.
DISCLAIMER
RolleaseAcmedahasusedreasonablecareinpreparingtheinformationincludedinthisdocument,butmakesnorepresentationsorwarrantiesastothecompletenessoraccuracyoftheinformation.Informationissuppliedupontheconditionthatthepersonsreceiving
theinformationwillmaketheirowndeterminationastoitssuitabilityfortheirpurposespriortouse.RolleaseAcmedaassumesnoliabilitywhatsoeverforanydamagesincurredbyyouresultingfromerrorsinoromissionsfromtheinformationincludedherein.Rollease
Acmedareservestherighttomakechangeswithoutfurthernoticetoanyproductstoimprovereliability,functionordesign.
COPYRIGHT
COPYRIGHT©ROLLEASEACMEDA2017
Allrightsreserved.Nopartofthisdocumentmaybereproducedorutilisedinanymeans,byanymeans,electronicormechanicalincludingphotocopying,recordings,orbyanyinformationstorageorretrievalsystem,withouttheexpresspermissionfromRolleaseAcmed
SECTIONNO.DESCRIPTIONPAGENO.

rolleaseacmedaRS485CablingStandard|August2017
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SECTION1 –RS485BUSOVERVIEW
Inordertoprovidereliable/robustcommunicationswithRolleaseAcmedaRS485‐enabledproducts,severalrecommendationsmustbecarefullyfollowed.Eachof
thesearelistedbelowandarecoveredindetailwithinthefollowingchapters.
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1. NetworkTopologies–howtoconnecthubstotheRS485bus.
2. DimensionalLimitations–thedistancesthattheRS485buscanreliablycommunicateover.S
3. CableTypes–typesofcablesthatcanbeused.
4. GroundConnectionStrategy–how/whygroundingisrequired.
5. InstallationOptions–simpleplug&playorcustomizedoptions.
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Diagram1.CompleteRS485network

rolleaseacmedaRS485CablingStandard|August2017
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SECTION2 –NETWORKTOPOLOGIES
Beforeaninstallationcanbegin,itisimportanttounderstandhowtoconnectRolleaseAcmedahubstotheRS485bus.Thefollowingdiagramdepictsseveralcommon
networklayouts,butnotethatonlytwoareusableforaRS485bus.
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Diagram2.RS485networktopologies
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SECTION3 –DIMENSIONALLIMITATIONS
ThemaximumlengthoftheRS485bus(includingstubslength)shouldnotexceed1000m(3281ft).Distancesgreaterthanthatwillresultinunreliable/error‐prone
communicationsandthereforeshouldbeavoided.Conversely,thedistancebetweennodesshouldbegreaterthan30cm(≈12in).
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(a) TypicalResidential/LightcommercialInstallations(<100m)
Formostresidentialenvironmentswherethetotalbuslength(includingstubs)islessthan100m(328ft)theterminationresistorsarenotrequired.
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Diagram3.Dimensionallimitations‐typicalresidential/lightcommercialinstallations

rolleaseacmedaRS485CablingStandard|August2017
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(b) Longdistance/CommercialInstallations(<1000m)
Forlongerdistancecommunications,theterminationresistorsRT=120Ω(RApartno.MT02‐0401‐000005)mustbefittedtotheextremeendsofthebus.
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Diagram4.Dimensionallimitations‐longdistance/commercialinstallations
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rolleaseacmedaRS485CablingStandard|August2017
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SECTION4 –CABLETYPES
RolleaseAcmedaonlyrecommendtheuseofTwistedPairethernetcables,thesecanbeeitherCAT5orCAT6.Formostresidentialenvironments,thecablecanbeof
eitherUTPorSTPtype.However,forlongdistanceorcommercialenvironmentsweonlyrecommendtheuseofSTPtypecables.
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Picture1.Recommendedcables
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SECTION5 –PINOUTDEFINITION
EitherTIA/EIA568Aor568Bconfigurationcable(oracombinationofboth)canbeconnectedinaRARS485network.Thisisbecauseonlythecoresthatsharethesame
pinout&color‐codeacrossbothstandardsareused(seeinTable1.PinoutdefinitionandDiagram5.ColorcoresofcableconnectedinRS485network).
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*Note:unusedcoresshouldbetiedtogroundiftheRS485busisgreaterthan100m.Refertopage15fordetails.
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Table1.Pinoutdefinition
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Diagram5.ColorcoresofcableconnectedinRS485network
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SECTION6 –GROUNDCONNECTIONSTRATEGY
Whileadifferentialsignaldoesnotrequireasignalgroundtocommunicate,thegroundwireservesanimportantpurpose.Overadistanceofhundredsorthousandsof
feettherecanbeverysignificantdifferencesinthevoltagelevelof"ground."RS‐485networkscantypicallymaintaincorrectdatawithadifferenceof‐7to+12Volts.If
thegroundsdiffermorethanthatamount,datawillbelostandoftentheportitselfwillbedamaged.Thefunctionofthesignalgroundwireistotiethesignalground
ofeachofthenodestoonecommonground.
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 Strategy(a):ShieldingAgainstLowFrequencyNoise 
Formostresidentialorlightcommercialenvironments,oneendoftheshieldshouldbeconnectedtogroundinordertoimproveshieldingagainstlowfrequency
electricalnoisesuchas50/60Hzmainsnoise.(refertoDiagram5)
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Diagram6.Groundconnection‐shieldingagainstlowfrequencynoise
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