Custom Search

Monday, May 12, 2008

A User's Experiences of Z-Wave

Japi’s blog » Blog Archive » Home automation, or when laziness and geekiness collide.

Japi's post is earlier than my "use case flaw in Zigbee and Z-Wave", but I just cross it today. Though it is basically a positive story of Z-Wave (over Zigbee), it provides first hand proof to some of my points in my post, difficulty to setup and reliability. User interface issue is something implied. From the blog, I can easily assume that this system is only used by Japi himself.

I like the title.It is right on the point and hilarious. I wish I could use it for my post.

Here is Japi's post:

In the past I have attempted to control some key lights in my house using X10, which is a standard for home automation (HA) using control signals over your power lines. In theory it should work well, just toss a signal down the AC line on top of the regular 60Hz power signal, and have devices receive it. It is fairly cheap to implement (with modules/switches costing about $13-$32), has well-documented computer interfaces (which are also reasonably priced), but it fails miserably in my house. I have about 50 CFL bulbs inside and outside for lighting which add noise to the power lines, and have computers, UPSes, and pumps that also cause signaling problems. And to top it all off, with standard 220V US power systems, you have two separate power lines coming from the electrical company transformer (located on a pole outside my house), and the signals don’t easily transition from one power line to the other (needing to go out to the transformer to make the jump). All of this combines to create a system that is very unreliable, and since X10 is a rather old standard that doesn’t support message delivery confirmation, it makes computer-based automation rather annoying.

Since the X10 network is not working, I researched what newer standards are available to perform the same work. There are four newer, much better home automation methods now: Insteon, UPB, Z-Wave, and ZigBee. ZigBee (an RF-based mesh network, also known as 802.15.4) has almost no devices available for consumer use at this point. Insteon is a standard promoted by Smarthome, and uses the powerline for communication like X10, but devices act as repeaters to boast signal strength, and it has confirmation support for much greater reliability. It costs a bit more then X10, and has documented computer interfaces available. But, you still need to get a bridge to join the two power lines for whole-house signal reliability (and this adds significant cost to the setup), and can still have noise problems. UPB (Universal Powerline Bus) is another standard over the powerline, supposedly even more reliable then Insteon, but still not 100% perfect, still needs a bridge, and the devices are fairly expensive ($70-$125 for modules). The last standard is the one I am going with for now: Z-Wave. Z-Wave is a mostly proprietary design from Zensys, using RF mesh radios that they manufacture. Other vendors sell the actual consumer devices (including Cooper, Leviton, and Intermatic), prices are a bit on the high side ($30-$100), but you can find devices on ebay occasionally at better prices. Computer interfaces are a pain, most of them are for Windows use, using a .NET SDK, which doesn’t help me since I run Linux on my server. There is a Leviton serial interface (RZC0P) that does have documentation that I am working on developing Linux support for.

Z-Wave is a RF mesh protocol, meaning the commands are sent over a wireless network (908.42 Mhz in the USA, different frequencies are used in other regions), and the commands get routed through multiple nodes to get to the final destination, if it is not within direct range from the sender. It supports message delivery confirmation, and status checking of all devices. This means if I send a signal from the computer interface in my basement to the pond outside, it probably hops first to a module on my aquarium, then a module in my sunroom, then out to the pond. So far it seems to be working pretty good, with the pond being the only module that is difficult to reach (about a 10% failure rate at this point without tweaking). The problem from the pond appears to be return messages, if I send it a “turn lights on” message, occasionally the light will turn on, but I will get a “failed” response on the controller, presumably because the “success” response from the pond didn’t make it all the way back. But I can just query the status of the module, and generally that does pass.

The routes are all statically defined as devices are added to the network. Z-Wave has a concept of a “primary controller”, which is the remote control you use to set up the network. You walk around with this fancy remote control, and when you want to add or remove a device from the network, you do it on this remote (I am using a Leviton RZCPG-BSG). When the device is added/removed, the remote updates it’s internal list of known nodes and determines the best routes to that device from the other nodes, and tells the other nodes the routes it has calculated. If you want to use additional remote controls, then those are “secondary controllers”, which can’t do route generation, but instead just send control signals out across the network (”Turn on aquarium light”, etc). Adding a node to the primary controller doesn’t immediately make it controllable, you have to add it to an “area”, and then you can press buttons on the remote to make your lights go on/off and annoy the neighbors. The same needs to be done on any secondary remotes that you have, with different button assignments if you so desire.

So far my network is small (due to the cost of modules, and since I am just testing). Right now I am using it for controlling the lights in my pond (which I only want on when I am around the pond, extra light just promotes algae growth that I don’t need), and the light on my main aquarium (which will be controlled by the computer interface once the software is done, to turn the lights on in the morning, but I will be able to easily turn them on/off at other times when I want). There are some outdoor lights that I would also like to control (patio light, front lights, garage light), but still need to find cheap modules for the switches. Initially testing indicates that all of this will work much better then X10, and I get to play with new software/hardware too.


  1. Hi, I stumbled upon your BLOG and was impressed with the details. I was wonderng if you tried to have both X10 and zWave devices co-exist with each other and have some kind of a smart touchpanel (wifi enabled) to master control the entire home. any thoughts/ideas ?

  2. Thanks for the post. Insteon, for me, started working GREAT, and then, over time, the network degraded for some reason (I suspect it's the bridge between the power phases that's gone flakey - Insteon had a 'exchange for new refurb' program that seems a bit suspicious.)

    I'm thinking of giving Z-Wave a shot. Sounds like a good solution, if all the nodes are relatively close.