PoE Fundamentals

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I’ll start by saying that I love Power Over Ethernet (PoE). 

Yeah, yeah, it’s what I do for a living, but, really, how cool is it that you can take the ethernet cable you have in your wall and get it to power up cameras, iPads, or even TV’s?  I see PoE as Potential (okay, yeah, I couldn’t resist the nerd joke, and be forewarned they keep coming).

In all seriousness, though, Power Over Ethernet can save you 30% on any given project where you would otherwise have to call a licensed electrician out to pull a permit just to put an outlet somewhere so you can hang a camera.  Even better, because PoE runs  on low voltage power (less than 56 volts) you can safely do the work yourself, or at least get your techie nephew to do it.

If it’s so cool, why doesn’t everyone do this all the time?  Frankly I’m stumped.  However, I blame it on it sounding too technical because it has to do with computers talking to each other.

That ends today. I help a lot of people find the right PoE solution, and believe me when I say you can understand PoE. Once you have a few basic terms and principles, you’ll blow minds! To make that magic happen for you I will simplify Power Over Ethernet (PoE) in an easy to understand way even if you’ve never worked on a network before.

Let’s start off with a pronunciation guide.  This is worth your time.  You drop this your friends and coworkers, and you become the de facto expert on PoE. 

  • PoE – pronounced PEE – OH – EEE.  Not like Edgar Allan “Poe”.
  • IEEE 802.3af – pronounced EYE TRIPLE EEEE EIGHT OH TWO DOT THREE AYE EF.
  • Okay, so say it with me now . . .  EYE TRIPLE EEEE EIGHT OH TWO DOT THREE AYE EF.

Great work!!

So what does that all mean?  Working from the ground up (another engineer joke!), PoE means putting electricity onto an ethernet cable along with a data signal.  You can use that electricity to power all kinds of things: cameras, lights, wifi access points, iPads, phones, TV’s, computers, media players, Raspberry Pi’s.  Warning: once you get into what you can power with PoE, it goes deep, like X-Files deep.
 
 
Oh, about the IEEE thing (yeah, you heard how cool you sound saying it).  Simply put, you have a very smart guy making cameras and you have another smart guy like me – ahem, why thank you – making devices that can power those devices over a network cable.  To make sure we all work together without having to constantly fight over things, we called our friends at the Institute of Electrical and Electronics Engineers (IEEE – “EYE TRIPLE EEE”) and asked them to help us create a standard way of doing things.  They agreed and added us to the 802nd section part three subsection “af” of their standard. 
 
You don’t need to read it, but if you do – SPOILER ALERT – data and power get together by the end.  
 
That standard is how engineers agree how the PoE will work, so we both make devices that talk the same PoE.  As time past we kept coming up with better and better ideas, like MORE POWER!  So now we have a few more standards.  Here’s a table of the PoE standards as they stand today (don’t worry, I will explain it all so just bask in the glory of it):
PoE Type or Standard Nickname Power Per Port
(at the device)
Types of Devices
IEEE 802.3af PoE 12.9 watts
IP Cameras
IP phones
iPads and Tablets
(<10″)
IEEE 802.3at PoE+ 25.5 watts
Outdoor PTZ Cameras
Dual Radio Wifi Access Points
USB Type C phones and tablets
(>10″)
IEEE 802.3bt PoE++
4Pair PoE
79 watts
Televisions
Lights
Blinds
Laptops
*Passive PoE 24 Volt PoE
Passive
Up to 55 watts
Ubiquiti or Mikrotik
Wireless Internet PtP or PtMP
(big Wifi Radios)

*Passive PoE can operate anywhere from 12 volts up to 58 volts. You’ll want to check your specifications carefully to make sure they match your device.