Maximum PoE length?

Sh00t3r · 07-20-2002

Can anyone tell me what the maximum length is for PoE (Power Over Ethernet) applications?

TIA!!!

fordem · 07-20-2002

Maximum length for twisted pair - as per IEEE - is 100m or 328 feet, so maximum length for PoE can't be greater than that, it can however be a lot less depending on whose implementation you're using.

I don't know if there is a defined spec, but some implementations use a power injector and a picker - D-Link DWL-P100 that simply interconnect between your ethernet device - in this case an AP - and it's power adapter. This type of implementation results in a voltage drop across the twisted pair that may cause problems depending on the length of the run and the current draw of the device.

Other implementations use a power injector that puts 48VDC on the twisted pair and use a regulated picker at the other end to ensure that the ethernet device gets full voltage, Hyperlink makes this one, along with a wide variety of other types.

Some devices have PoE built in and these typically have an internal regulator that reduces the PoE voltage to the required operating level and will work with PoE switches - Cisco is one example.

Of course you can also homebrew some of this stuff - google will give you a few examples of the first type - and I of course built my own

Sh00t3r · 07-21-2002

Fordem,

Thanks for your post! I wasn't aware that the PoE is still on the same standards for twisted pair! Interesting. I'm making my own PoE as well and connecting it to a node about 90 meters away. It'll be nice to know I can run the PoE parrallel to all my networked devices! Thanks again!

Sh00t3r

07-20-2002	#1 (permalink)
Sh00t3r Registered Member Join Date: Apr 2002 Location: Michigan Posts: 199	Maximum PoE length? Can anyone tell me what the maximum length is for PoE (Power Over Ethernet) applications? TIA!!!

07-21-2002	#3 (permalink)
Sh00t3r Registered Member Join Date: Apr 2002 Location: Michigan Posts: 199	Thanks! Fordem, Thanks for your post! I wasn't aware that the PoE is still on the same standards for twisted pair! Interesting. I'm making my own PoE as well and connecting it to a node about 90 meters away. It'll be nice to know I can run the PoE parrallel to all my networked devices! Thanks again! Sh00t3r

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07-20-2002	#2 (permalink)
fordem Tropical Stumbler Join Date: Apr 2002 Posts: 575	Maximum length for twisted pair - as per IEEE - is 100m or 328 feet, so maximum length for PoE can't be greater than that, it can however be a lot less depending on whose implementation you're using. I don't know if there is a defined spec, but some implementations use a power injector and a picker - D-Link DWL-P100 that simply interconnect between your ethernet device - in this case an AP - and it's power adapter. This type of implementation results in a voltage drop across the twisted pair that may cause problems depending on the length of the run and the current draw of the device. Other implementations use a power injector that puts 48VDC on the twisted pair and use a regulated picker at the other end to ensure that the ethernet device gets full voltage, Hyperlink makes this one, along with a wide variety of other types. Some devices have PoE built in and these typically have an internal regulator that reduces the PoE voltage to the required operating level and will work with PoE switches - Cisco is one example. Of course you can also homebrew some of this stuff - google will give you a few examples of the first type - and I of course built my own