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485TBLED-0812-1/3PRODUCTINFORMATIONB&BELECTRONICSwww.
bb-elec.
comorders@bb-elec.
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comInternationalOffice:707DaytonRoadPOBox1040Ottawa,IL61350USA815-433-5100Fax433-5104EuropeanOffice:WestlinkCommercialParkOranmoreCo.
GalwayIreland+35391792444Fax+35391792445Model485TBLEDRS-232toRS-485ConverterThe485TBLEDconvertsunbalanced,full-duplexRS-232signalstobalanced,fullorhalf-duplexRS-422orRS-485signals.
RS-485isanenhancedversionoftheRS-422Standard.
Itallowsmultipledriversandreceiversonatwo-wireorfour-wiresystem.
TheRS-232port,configuredasaDCEport,hasafemaleDB25connectorwithpins2(TDinput),3(RDoutput),and7(SignalGround)supported.
Pins4(RTS)and5(CTS)aretiedtogether,andpins6(DSR),8(CD),and20(DTR)arealsotiedtogether.
Pins1(FrameGround)and7(SignalGround)areconnectedstraightthroughtotheRS-485terminalblocks.
TheRS-485terminalblockssupportTransmitData(A-)and(B+),ReceiveData(A-)and(B+),FrameGround,SignalGround,and+12VDCinput.
SeeSchematic.
LEDsThe485TBLEDhastwoLEDs:aTransmitDataLEDtoshowwhentheRS-485driverisenabledandaReceiveDataLEDshowingdataappearingatpin3oftheRS-232port.
Theseareveryusefulfordeterminingifdataisgettingthroughtheconverter.
NotethattheTDLEDindicatesthattheRS-485driverisenabled.
Datamustbepresentonpin2oftheRS-232sidefordatatobetransmittedoutoftheRS-485side.
Ifnodataispresent,nodatawillbetransmittedeventhoughtheTDLEDisilluminated.
FlowControlThe485TBLEDusestwodifferentmethodstoenabletheRS-485driver,eitherbytogglingRequesttoSend(pin4)oftheRS-232side,orbyautomaticsensingofthedataonTransmitData(pin2)oftheRS-232side.
Thisoptionisuserselectablebysettingpush-onjumperslocatednexttotheterminalblocks.
SeeFig.
1.
RemovingbothsetsofjumperscompletelycanalsoconstantlyenabletheRS-485driverandreceiver.
Thismakesthe485TBLEDactlikeanRS-422converter.
BaudRateThereisatimingcomponentontheconverter,aresistorR9,seeFig.
1.
Thiscomponentispartoftheautomaticsensingcircuit,andaffectsthebaudrateatwhichtheconvertercanbeusedinatwo-wiresetup.
Thiscomponent,isfactoryselectedtoallowtheconvertertorunat9600baudorhigher.
Withthiscomponent,theRS-485driverwillshutoffapproximately1msafterthelastcharacterhasbeensent.
Ifyouneedtochangethe485TBLEDtoabaudrateotherthan9600baud,youcanchangethiscomponent.
Tochangethebaudrate,removeR9andaddthroughholecomponentR14,seeTable1.
Figure2showshowtointerconnecttwoRS-485convertersusing4-Wireand2-Wires.
Figure2Figure1485TBLED-0812-2/3PRODUCTINFORMATIONB&BELECTRONICSwww.
bb-elec.
comorders@bb-elec.
comsupport@bb-elec.
comInternationalOffice:707DaytonRoadPOBox1040Ottawa,IL61350USA815-433-5100Fax433-5104EuropeanOffice:WestlinkCommercialParkOranmoreCo.
GalwayIreland+35391792444Fax+35391792445TheEchojumperisusedinthetwo-wiremode,andallowsyoutopreventdatabeingsentfromtheRS-232portfrombeingechoedbacktotheRS-232port.
Upto32receiverscanbedrivenbyanyoneRS-485driver,allowingyoutoputtogetherlargesystemswithmanydroppoints.
Ifyouareusingterminationresistors,theyshouldbelocatedatoppositeendsofthesystem.
ProperoperationofanyRS-485systemrequiresthepresenceofareturnpath.
TheRS-485Standardrecommendsthatathirdwirebeusedforthis.
Forsafety,a100ohmresistorshouldbeconnectedbetweenSignalGroundandthe"referencewire"ateverydroppoint.
WhileitmaybepossibletointerconnectSignalGroundsdirectly,thisisnotrecommendedduetothedangerofcirculatingcurrentspossiblybeingpresent.
NowiretypeormaximumrunlengthislistedintheRS-485Standard.
However,theRS-422Standard(whichisverysimilar)recommendsnumber24AWGtwistedpairtelephonecablewithashuntcapacitanceof16picofaradsperfoot,andnomorethan4000feetofdistance.
Specifications:Dimensions:2.
14"x3.
32"x.
725"(54.
5x84.
34x18.
43mm)SupplyVoltage:9–14VdcTemperatureRange:0°C–70°CDataRate:Upto115.
2kbpsConnector:DB25FemaleonRS-232sideDECLARATIONOFCONFORMITYManufacturer'sName:B&BElectronicsManufacturingCompanyManufacturer'sAddress:P.
O.
Box1040707DaytonRoadOttawa,IL61350USAModelNumber:485TBLEDDescription:RS-232toRS-485ConverterType:LightindustrialITEequipmentApplicationofCouncilDirective:89/336/EECStandards:EN55022EN61000-6-1EN61000(-4-2,-4-3,-4-4,-4-5,-4-6,-4-8,-4-11)RobertM.
Paratore,DirectorofEngineering485TBLED-0812-3/3PRODUCTINFORMATIONB&BELECTRONICSwww.
bb-elec.
comorders@bb-elec.
comsupport@bb-elec.
comInternationalOffice:707DaytonRoadPOBox1040Ottawa,IL61350USA815-433-5100Fax433-5104EuropeanOffice:WestlinkCommercialParkOranmoreCo.
GalwayIreland+35391792444Fax+35391792445MouserElectronicsAuthorizedDistributorClicktoViewPricing,Inventory,Delivery&LifecycleInformation:B&BElectronics:485TBLED