Data Sheet

12/23/2015 PowerOverEthernetforArduino|Freetronics
http://www.freetronics.com.au/pages/poweroverethernetforarduino#.VnqWJrZ97IU 4/6
evenACinput)andconvertsittoplaceDC+onpins4/5andDConpins7/8.
Thisparticularmidspaninjectordoesnotattempttodoanyvoltageregulation,sowhatevervoltageyouputintoitisthe
voltagethatwillbesentdownthewiretoyourpowereddevices.Makesureyouuseapowersupplythatisappropriatefor
thedevicesyouwillconnect,asdescribedbelow.
SettingUpAPoweredDevice
IfyourPoweredDevicedoesnothavebuiltinPoEsupportyouwillneedtoseparateoutthepowerfromtheEthernet
cableandconnectittothedevice'spowersocket.AcommonscenarioisusinganArduinowithanEthernetshieldthat
doesnotsupportPoE.
Justlikewhensettinguptheinjector,therearetwocommonwaystodothis.ThecheapestistocutintotheLANcable
andattachaDCplugthatcanthenbepluggedintotheArduino'sDCpowerjack.Usethetechniquedescribedaboveto
stripbackthecable,determinethecorrectconductors,separatethemout,andsolderona2.1mmDCplug.Youcanthen
plugtheRJ45connectorintotheEthernetshieldandtheDCplugintotheArduinoasshownbelow.Thepowerinjectedinto
thenetworksegmentwillneverevenreachtheEthernetshieldsothere'slittledangerofitbeingdamaged.
Aneaterwaytoachievethesameendresultwithoutdoinganycablecuttingorsolderingistouseadevicecalleda"PoE
splitter"thatconnectsbetweentheLANcableandthedevice.IthasasocketintowhichyoucaninserttheLANcable,
andthenconnectstotheRJ45portontheEthernetshieldandtheDCjackontheArduino.
IfyouhaveaPoweredDevicewithbuiltinPoEsupportthenyourjobisreallyeasy.Forexample,theFreetronics
EthernetShieldincludesbuiltinPoEsupportandcanextractthevoltagesuppliedonthePoEpairsandsenditthroughto
yourArduino'sonboardvoltageregulator.Withthisapproachyoudon'tneedanythingadditionalatthePDend:justplugit
intothepowerednetworksegmentandyou'rereadytogo.Nomess,nofuss.
Ifyourpowersourcingequipment(suchasamidspaninjector)suppliesavoltagethatissafeforyourArduinotouse
directly,suchasaDCvoltagefromabout7Vtoabout14V,youcansimplyputapairofjumpersacrossthePoEheaderof
theEthernetshieldsothatthePoE"+"headerconnectstoArduinoVIN,andthePoE""headerconnectstoArduinoGND.
ThepicturebelowshowsanEthernetshieldfittedtoaFreetronicsTwentyTenandbeingsuppliedwithapproximately9Vvia
theEthernetcable.TheTwentyTenispoweredupandrunningfromthepowersuppliedviatheLAN: