In my last post I talked about watching a talk by Steven Goodwin at Barcamp Berkshire this year. He’s been into Home Automation for quite a while now, and his system is based around a X10 for network. X10 has been around for a while (since 1975 apparently) and despite its critics it still remains one of the dominant protocols used today. But as I knew from doing a little reading, it’s far from the only contender.
The big three:
- X10 – sends it’s signals through the mains power lines – so naturally all devices need to be attached to the mains. As it’s been around for so long there are a huge number devices from lots of different manufactures; and as the protocol is fairly simple, compatibility between manufactures seems to be fairly good. Its main drawback is that the protocol does not include any (easy) way for devices to acknowledge a message, so when you get an intermittent fault, it can be hard to diagnose.
- Z-Wave is seen by many to be the current de-facto standard. As with X10 there are multiple manufactures creating devices (which is helping to slowly inch prices down) and it’s (generally) controlled by a central server. However rather than use wires, Z-Wave uses low-power radio waves (868MHz in Europe and 900MHz in USA) in a mesh network.
- ZigBee could, in time, become the next big thing in automation. Backed by the IEEE 802.15.4 standard, it’s sometimes touted as one of the core protocols of the Internet of Things. Much like Z-Wave it’s radio based, but it has a far more robust security model, making it attractive for manufactures who want to use it for health and smart metering. Unfortunately, although the core specifications are mature, there is not a huge range of devices available so far; this coupled with a restrictive licence (which makes it hard for open source software to use it) means it’s not quite ready for hobbyists to start experimenting with.
The other contenders
There really are too many systems to mention them all here. Whilst INSTEON and LightwaveRF (and others) are popular, they suffer because there is only one (or a small number) of companies creating the devices. So there just isn’t the range to base an entire system on. There are also older systems like C-Bus which are just too disruptive to consider using for all but the biggest systems (C-Bus requires CAT 5 cabling to each switch to work).
We could also consider more specialised protocols like the ones used by the Philips Hue (LED lighting) or Sonos (multi-room audio), which don’t even attempt to provide a general solution but instead are focused on one specific function.
So which protocol to go for?
I came away from the weekend torn between X10 and Z-Wave. But then I realised; whichever protocol I chose, it was going to be a compromise. None of the available protocols support everything I wanted to do, and none could give me all of the devices I wanted.
But whichever protocol I chose, I’d still need a central controller to actually do the automation and modern controllers now support multiple protocols; so it’s the choice of controller that is the crucial thing.