Adding more sensors to your network? Zigbee or ZWave?


(John Essey) #1

Over the last few months most of my additional sensors/devices (all of them, actually) have been z-wave products.

If you’re expanding your network, are you buying and implementing both zigbee and z-wave, or one technology more than the other, and why?

I am finding z-wave more reliable…and I have my reasons, but I want to know what others are doing – if you don’t mind sharing!

Thanks!


Thread - a "new" home automation protocol
(Steve S) #2

The only zigbee devices I have are the ones that came with the starter kit and a ThingShield I just bought last week. The rest of my system: 13 switches (GE/Jasco), 4 motion sensors (Schlage), a door contact sensor (Schlage), 2 Smoke Detectors (First Alert ZCOMBO), and a micro smart switch - are all Z-wave. Even if you look at this list: http://build.smartthings.com/compatible-devices/ it’s mostly Z-wave.


(Jeremy Whittaker) #3

Plus I believe all ZWAVE devices act as repeaters to each other if the signal cannot make it from the hub directly to the device. The Zigbee ones I do not believe have this capability.


(Jeremy Whittaker) #4

One other thing I just thought about. I’m also pretty sure Zigbee uses the over crowded 2.4GHz network as to where ZWAVE uses 900mhz. 900mhz can penetrate objects a lot better as well.


(Todd Wackford) #5

Guys,

Only A/C Powered devices act as repeaters.

I find the zigbee devices more reliable and they can handle more data. But everyone’s environment is different. Your walls, hub location, distance from hubs and just what brand/device makes each one unique. I have over 50 devices and most are zwave, just because they are available and cheaper. Light switches, locks and outlets mostly. I also have numerous other RF devices in the house. Nothing is seeming to bother the zwave or zigbee transmissions (that I know of).

I did do a couple of zwave mesh repairs though and I think that it did improve zwave performance. By doing that, the hub and devices supposedly learn the best way to mesh and hand data back and forth to the hub. With as many devices as I have, it takes a few hours to complete. Each time I kicked it off before leaving for work.

Anyway, my 2 cents.
Twack


(John Essey) #6

I have a lot of issues with my zigbee devices, but never have any issues with zwave products (I only have 16 zwave, 5 zigbee). Though I wonder if only having one zigbee repeater/outlet is why I’m having issues (all my zigbee devices stop communicating with my hub, randomly…but they do work fine for weeks / months, then just stop). I do not know or have much experience with zigbee products outside of ST.

I have other RF devices around, another controller, no issues with the zwave stuff really.

I guess I wanted to get feedback on what others are buying, why, and how your network is shaped and set up, and maybe what your experience is like running a few different protocols and services.

I’ll end up buying more zwave, but I still have some interest in adding zigbee devices if I can find a compelling reason to do so.

Thanks!


(Col Hack) #7

I came across this old thread and thought I would add some more fuel to the fire. :slight_smile:

Aside from guesswork, opinions and speculation, here are some technical facts about Z-Wave and Zigbee:

  1. Frequency Band

Z-Wave - 908 MHz (US), 860 MHz (Europe)
Zigbee - 2.4 GHz (world-wade)

As a rule of thumb, the lower the frequency, the longer the range and better obstacle penetration. 2.4 GHz band is particularly bad for two reasons: (a) this is the frequency where all your WiFi, Bluetooth, wireless keyboards and most other consumer electronics gadgets transmit, so it’s indeed a crowded place. And (b), it’s a frequency used by microwave ovens. For example, one particularly nasty microwave in my kitchen practically kills all WiFi in my house. I give a score to Z-Wave on this one.

  1. RF Modulation

Z-Wave - FSK/GFSK (Gaussian Frequency Shift Keying)
Zigbee - O-QPSK (Offset Quadrature Phase Shift Keying)

Long story short, Z-Wave uses simple “run-of-the-mill” FSK modulation, while Zigbee sports more advanced modulation technique called spread spectrum, which makes Zigbee more noise-immune. This definitely helps it co-exist with all other radios in the 2.4 GHz band (see #1). Also, Zigbee network coordinator can choose one of 16 available channels, while Z-Wave is confined to a single frequency. Zigbee is definitely ahead on this one.

  1. Bandwidth

Z-Wave - 9.6 / 40 / 100 kbps (depending on version)
Zigbee - 250 kbps

This how fast data is being transmitted. So Zigbee is more than twice as fast as the fastest Z-Wave version. But home automation devices typically transmit tiny amounts of information, just a few bytes when a door contact opens or motion is detected. So does it matter if it takes 0.02 or 0.01 seconds to transmit a message? Yes, for battery-powered devices it does! Faster speed means that the radio has to be powered for shorter period of time to transmit the same message, leading (theoretically) to longer battery life. Zigbee has an advantage on this one too.

  1. Network Topology

Z-Wave - Mesh network with multiple controllers
Zigbee - Mesh network with single controller

Both Z-Wave and Zigbee are mesh networks, meaning that any mains-powered node can act as a re-transmitter, thus increasing network coverage. Z-Wave however has an advantage, allowing multiple controllers. I.e. a secondary controller (e.g. a remote control or a key fob) can talk directly to light switches or sockets. In Zigbee on the other hand, all communications must go through single coordinator. Z-Wave network will continue to function if the main controller goes down, but Zigbee will not. One more score for Z-Wave.

  1. Interoperability

Z-Wave - Good
Zigbee - Bad

Z-Wave is a proprietary protocol designed by a single company for a single purpose (home automation). It is therefore more focused and more to the point. Zigbee, on the other hand, was designed by a committee with two dozen players pulling in two dozen different directions. There are multiple domains within Zigbee specification, called “profiles” which are in fact different and sometimes incompatible “standards” in its own right. What’s even worse, there are multiple, competing profiles that essentially do the same thing. There is for example, the Home Automation Profile, the Building Automation Profile and the Light Link Profile, all of which do essentially the same thing - turn the lights on and off. That’s why it’s hard to find Zigbee devices from different vendors that can talk to each other. Z-Wave definitely wins this one.

  1. Availability

Z-Wave - High
Zigbee - Low

Z-Wave has been accepted as technology of choice by several major manufacturers, including GE. I read somewhere recently that up to 80% of all home automation products in US use Z-Wave. Don’t know if its true, but it’s definitely easier to find a Z-Wave switch or socket
than Zigbee one. One more score for Z-Wave on this one.

  1. Cost

Zigbee radios tend to be more complex and hence more expensive, leading to higher end-product price, although production volume probably has bigger impact on the final price tag. Z-Wave is slightly ahead on this one, but I’ll call it a tie.

  1. Total Score

Z-Wave - 5
Zigbee - 3

So, it looks like Z-Wave comes ahead in this simple contest. Personally, I think that although Zigbee is technically superior, all its advantages are less important then almost universal adoptance and commercial success enjoyed by Z-Wave. After all, in my experience Z-Wave works very reliably. What do you think?


(Ajf) #8

John as I understand it, they were having trouble with the Zigbee outlets early on so they switched over to Zwave outlets in the kit. I believe the only piece in the kit that will act as a Zigbee repeater now is the SmartSense Motion but as Twack said it MUST be plugged in to the AC using the adapter; it won’t act as a repeater while on battery.


(John Essey) #9

@kernelhack

Man, that was very informative, easy to follow and make sense of things! I appreciate your feedback here (and other items).

@tonyfalcone, I had a ton of issues early on with the Outlet they shipped, but have since returned and swapped out for a z-wave outlet. Oh wells…

Cheers!


(Chrisb) #10

Agreed John, on both accounts:

Thanks much @kernelhack for that breakdown. Some of the concepts and info I already knew but getting all of it laid out there nicely is great. My one question is re: points 1 and 2. Do you think the two cancel each other out to some degree? I can see a Zigbee advocate saying: “Sure, 2.4 is a bit crowded, but we’ve got some REALLY robust modulation to deal with this noise. Far more than Z-wave does!” And then seeing a Z-wave advocate countering: “Okay, sure… Zigbee has more robust modulation… but that’s because they HAVE to have it. Or freq. is used so much less that there just isn’t a need for a complex (and therefore more expensive) modulation.”

Looking at just point one and two… which one wins in your opinion?

And @tonyfalcone, I was in the same situation as John. Lots of problems with the Zigbee outlet interfering with motion sensors as well as presence tags. After getting rid of the outlet now I have no problems.


(Col Hack) #11

@chrisb, It’s a tough question and the answer will depend on the actual deployment environment. Zigbee performs very well in open space, where there’s no hard obstacles (e.g. concrete walls) and can easily cover large areas thanks to its mesh topology. However, in a typical residential environment (a home or an apartment) with a lot of walls and very strong sources of interference in 2.4 GHz band, Zigbee will likely perform worse than Z-Wave. Spread spectrum definitely saves Zigbee’s ass from total jamming by the WiFi router, but if you place your Zigbee coordinator close enough to a busy WiFi router you’re almost certain to have communication issues. Also, no mater what, Z-Wave is definitely better at penetrating thick walls.


(Scott) #12

I’ve got 2 older Zwave plug-in switches in my setup currently, they keep going inactive every few days. I have to unplug them, and let them sit for a few minutes. When I plug them back in, they start working again for a few days.

I have done Zwave mesh repairs from the IDE site, but the inactivity / dropouts keep occurring.

Both of these Zwave plug-ins are very close to the hub (probably the closest devices to the hub in fact - one mere feet away, the other in the room right above the hub). I think I’m going to replace one of them (probably the one upstairs) with a ST Smartpower outlet (which I think is Zigbee, not Zwave) to see if it stays connected better.

Once I remove the Zwave plug-in I’m going to replace with the Smartpower outlet, should I repair the Zwave mesh again?

And on that front … if I pull the power from the hub for a few minutes, do the mesh networks rebuild themselves when the hub is plugged back in? Or is it necessary to go to the IDE and do the repair mesh utility?


#13

@Goldndoodle
Zigbee will rebuild when you unplug the hub but for Zwave you have to run the repair.