POE Splitters Revisited
Around here we make significant use of power-over-ethernet. If something can be powered from the network…it is. Sometimes that means the device itself supports POE. Occasionally it means the device is connected to a “POE splitter.” That’s a little device that receives 802.11af standard p.o.e. and breaks out a 5v or 12v DC feed. This is how we power the little IoT hubs from Philips Hue and Lutron, and some Raspberry Pi’s.
Some time ago I did a little exploration of POE extenders. These are like little network switches that receive ethernet with power from one cable, allowing it to be passed onward to 2-3 POE capable devices. The theory here is that a single run of Cat 5E can power 2-3 IP cameras, up to the load limit of the port on the switch. If the switch is capable of POE+ it can readily handle two or three cameras connected to a single port.
Recently I learned of a different kind of POE splitter. These are a wholly passive arrangement. Just some wires and connectors. They leverage the fact that Ethernet does not use all 8 conductors in the cable. So, by shifting which pins use which wires at both ends of the cable, you can effectively turn one cable pull into two Ethernet drops.
At the switch, a combiner component connects two ports to a single cable. At the far end, a splitter component breaks the feeds out to separate Ethernet jacks. Power can be delivered over both connections.
It’s dead common to have a camera position at the peak of a roof gable, or the corner of a house, where you might like to have cameras looking in each direction. This harness makes that possible without pulling two Ethernet cables. And retains the ability to power cycle each camera by cycling power to the associated port.
While not fancy, these wee beasts are simple and cheap. Just $15 a set. That seems quite attractive for some common situations.
Since the crazy storm of May 16th took out power for much of Houston, there has been a lot of chatter about strategies for backup power. So much so that 
It now seems half-a-lifetime ago that I used to commit an hour or two every Friday to join Randy Resnick’s VoIP Users Conference (VUC) calls. That long-running project developed a global community of like-minded geeks, addressing a broad range of technology topics.
