PoE Secret Strengths

 Posted by at 1:09 pm  Gadgets
Oct 212013

As I build out the network in our home and other buildings on our farm property, I’m rapidly becoming a fan of Power over Ethernet. I got interested in it for the normal reasons (placing wifi access points in places without easy access to power) but now that I have it I’m finding additional perks even on my office desktop that no one seems to talk about.

Power over Ethernet (PoE) is a standard (802.3af) for powering devices using voltage carried on “spare” wires in the Ethernet cable.  For devices that support being powered by PoE, it means you only need one cable to the device to connect it to network and provide power.  Only one cable to snake through walls and attics, and the device can be placed without regard to access to a power outlet.

PoE is rightfully marketed to business IT and is particularly well suited to devices such as IP security cameras, wireless access points, and IP phones. Unfortunately, targeting the business IT audience meant the devices tended to be a lot more expensive than consumer equivalents.

That is now changing. I’m finding a fair number of PoE PSE switches (PSE = Power Source Equipment, that supply power on the Ethernet wire) and PoE PD devices (PD = Powered Device) in the consumer price range.  They’re still listed under “business networking” rather than “home networking”, but at least they exist.

Netgear is getting into the PoE game.  I picked up a Netgear GS108P gigabit switch to provide PoE power from the wiring closet for my planned network build-out at home. It works like a regular unmanaged gigabit ethernet switch for network devices that don’t care about PoE, but there are 4 ports available which provide PoE power for those that do care.

Most of Ubiquiti Networks’ wifi access points can be PoE powered, though the devices themselves are not 802.3af compliant. Ubiquiti uses a proprietary fixed voltage equivalent of PoE for their devices. You’ll either need to use Ubiquiti’s proprietary power injector at the switch end of the line or get a Ubiquiti PoE inline adapter as a separate purchase. Eliminating another power brick in the wiring closet makes the PoE converter well worth the extra $20 bucks.  Ubiquiti Unifi Outdoor AP + 802.3AF inline adapter. Done.

And that brings us to the secret strength of PoE: it eliminates power bricks. Sure, this is critical when you’re trying to mount a wifi access point on the gable of a roof, but losing the power brick is just as liberating at your desk. Power bricks require an outlet, and frequently block adjacent outlets. Even with a multi-outlet UPS and sidecar power strip, power outlets are at a premium.

I’m planning to do some work with network-connected microdevices in the near future. Tinkering with a networked gadget at my desk means I’ll need another Ethernet port. I currently just have the one Cat6 wire running from my desk to the wiring closet. Not a long run, but convoluted enough that I would not want to have to run another wire back to the wiring closet.

So, I need to add an ethernet switch at my desk. And the switch will have a power brick in need of a power outlet. Ugh.

Or will it?  An Ethernet switch powered by PoE wouldn’t add a power brick to the rat’s nest of wiring under my desk. Something like the Netgear GS108T gigabit switch works beautifully.

The funny thing is, you’d never know that switch can be PoE powered by reading the product description on Amazon. The bright yellow label on one of the Ethernet ports in the product photo is a PoE hint, but you have to dig into the product spec sheets on the Netgear site to confirm it.

PoE can be a bit complex to implement, since it is a power negotiation protocol. Now that all the PoE protocol logic is wrapped up in mass produced IC chips (like this Texas Instruments TPS23750) for less than $1.50 each in quantity, I hope we will see more PoE equipment in the consumer price range.

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