Power Over Ethernet Question

Narked Diver

macrumors regular
Original poster
Apr 8, 2014

I’ve run out of ports on the back of my AirPort Extreme so I’m looking to buy a switch to add some more ports

As I have a Hue Hub and a Raspberry Pi currently connected via Ethernet I figured I could buy a PoE switch and then add a couple of PoE splitters to power these devices

My question is is there anything particular that I need to look out for when buying the splitters other than ensuring that they have the correct power adapter fitting?

For example if the switch supplies 48v and the Pi requires 5v do I need to ensure that the splitter only supplies 5v or can I buy any old splitter and the Pi will only draw the voltage that it needs?

Thanks in advance


macrumors 603
Aug 15, 2005
No longer logging into MR
The voltage must be near identical, usually within 5-10%. Amperes, or amps, can be different but the supply side must exceed the load, usually by 10-20%. Usually all PoE devices conform to one of the specs at 24 or 48 volts.


macrumors 68020
Jun 2, 2016
Cornwall UK
we use PoE here at work.

we find the extractors do not work very well in some cases.
how ever injector/extractor kits do work.

we mainly use PoE for our cisco IP phones which are 48v.

Narked Diver

macrumors regular
Original poster
Apr 8, 2014
Thanks for the help folks

I’ll make sure the splitters have an output voltage that matches the input requirements of the two devices


macrumors 6502a
Jan 9, 2010
South Congress AZ
Despite the bit of extra clutter (which is in the laundry room anyway), I much prefer PoE injectors for each device. You can match the devices's PoE power standard/requirement exactly (there are a few standards), but you also eliminate the PoE switch, which runs hot and uses fans, which can fail over time.