In my last post, I mentioned that a “Good” home automation system requires the right protocols and infrastructure. What do I mean by this?
Most DIY home automation uses one of several wireless systems. While wired systems exist (KNX is supposed to be very good), they require pulling physical wires to every switch and outlet you want to automate, an undertaking beyond the scope of most of us, especially in an existing house. Most of the devices for such systems are generally only available through commercial system installers at very high prices. (There are also powerline-based systems, such as X10 and Insteon, which are technically wired, but they don’t require any additional wiring, just your home’s existing electrical wires. However, these are considered fairly outdated by today’s standards, so we won’t be discussing them here.)
The four most common protocols in my experience are Z-Wave, Zigbee, WiFi and 433 MHz. There are also several proprietary protocols. Let’s talk about their pluses and minuses.
Z-Wave
Z-Wave is a wireless protocol designed for home automation. It uses a low-energy radio and a mesh network, which allows each device to re-transmit signals to a central control unit.
Advantages:
Due to it’s mesh architecture, having more devices makes the network stronger. In theory at least.
Z-Wave devices are available from many manufacturers, so you are not locked in to any one vendor. So far, all of them seem to be interoperable with one another if they use the same frequency.
Z-Wave is entirely local – the signals don’t go much past your house and don’t end up on the Internet, so it’s impossible to spy on or hack the Z-Wave system directly without being inside, or just outside, your house. (However, your hub is almost certainly exposed to the Internet in some way, so an attack is certainly possible).
Z-Wave operates on frequencies in the 869-926 MHz range which are not used by WiFi or most cell phone systems, so interference between them is less likely. (Note that the exact frequency depends on the country where it’s being used, so be sure to buy devices meant for your country of residence as they aren’t cross-compatible and it’s illegal to use the wrong frequencies.)
Z-Wave is a protocol designed for automation, and as such is very low powered. This means that you can have battery-powered devices whose batteries last for many months or even years.
Z-Wave will often work straight out of the box. Plug in (or wire-in) the device, pair it with the controller, and it should just work.
Disadvantages:
In my experience, Z-Wave is not very stable. I have devices constantly dropping off the network and coming back. Originally I was using an Aeotec Z-Stick as a controller with my Home Assistant system, and later switched to a Vera Pro. Vera has proven much more stable, but still far from perfect.
I also find Z-Wave to be very slow. With switches, from the time I issue a command in the HA UI, to the time they actually turn on/off, there’s a significant delay. There’s also a significant delay in the acknowledgment, from when the switch actually cycles to when it informs HA of the status change. Similarly, I have two PIR motion sensors, one Z-Wave, one WiFi. The reaction time of the WiFi one is much faster.
To be fair, I’ve been told that both of the above problems are configuration issues – that the devices have to be assigned to correct classes and have various settings tuned. That may be so – I’ve not investigated this deeper, yet. But if so, it significantly reduces Z-Wave’s ease of use advantage. Which also brings me to:
Configuring devices is annoying. While most work ok out of the box, changing a setting is complicated. You have to lookup which numbered parameter on a given device controls the setting you want, and then the value of the setting, and transmit that to the device from the controller. For example, I have some Aeotec Smart Plugs that by default have a bright green ring when “on” and bright “red” ring when off. Annoying in the bedroom. It’s configurable, but the code isn’t in the manual it ships with. You have to download the “Engineering Specifications and Advanced Functions for Developers” document, which tells you that you want to change parameter 0x51 (81 dec) from 0 to 1. But that’s only on that specific device. A different plug may have a different parameter.
The devices seem to learn their locations, so while more devices strengthens the mesh, moving a device to another locations seems to cause disruption of the network, as the routing information stored in the system is now incorrect. There are commands to repair the mesh, but they don’t seem to always work well.
Finally, there’s price. Z-Wave devices tend to be more expensive than many other types, especially WiFi ones.
Zigbee
Zigbee is a wireless protocol designed for various short-range, low-power applications, including home automation. It uses an ad-hoc network, which is similar to the mesh used by Z-Wave, but while in Z-Wave systems every device is a re-transmitter, in Zigbee systems only some devices have that function. Disclaimer: I’ve not used Zigbee so far, so my knowledge here is purely theoretical.
Advantages:
Like Z-Wave, Zigbee is designed for low-power usage and is thus well suited to battery-powered applications.
If enough devices can act as relays, then adding additional devices strengthens the mesh.
Zigbee devices vary in price, but some, like those from Xiaomi, are quite inexpensive compared to Z-Wave, though often more expensive than WiFi.
Disadvantages:
Unlike Z-Wave, Zigbee devices don’t interoperate well across brands. Most brands have their own hubs/controllers that only work with devices from that brand, and, conversely, devices only work with that brand’s hubs. There is some overlap, and there may be some devices that are more broadly compatible, but be verious cautious in your choice of brand if choosing to use Zigbee.
Most Zigbee units operate on 2.4GHz, which means they can interfere with WiFi or not work well in WiFi-heavy environments. I do not know if this is actually a problem in real applications.
WiFi
WiFi is familiar to most of us – 802.11(b) and it’s successors, WiFi is a general purpose protocol meant for connecting devices to local networks and the Internet. Unlike Z-Wave and Zigbee, it’s very high bandwidth, and fairly high power.
Advantages:
WiFi-based devices are generally among the cheapest IoT devices of their kind, with only 433MHz devices rivaling them in price.
WiFi devices are higher powered, allowing them to work at longer ranges than Z-Wave or Zigbee when no re-transmitters are present.
WiFi devices are very fast. In my experience, far faster than Z-Wave.
WiFi devices can be extremely stable, provided one has the right firmware and architecture.
Most WiFi devices on the market use an ESP8266 or ESP32 chip, which allow them to be fairly easily flashed with alternate firmware, giving one complete control over the device.
Especially with after-market firmware, WiFi devices can communicate with the system hub using several well-established, very efficient protocols such as MQTT.
Some WiFi devices can communicate directly, bypassing the system hub, which can allow a more distributed system. While I don’t find this of much use personally, it’s an interesting option.
WiFi devices are very DIY-friendly. A board like a NodeMCU or Wemos D1 Mini can be bought for $3-4 on Amazon or a fraction of that on Banggood or AliExpress, and can be connected to nearly any sensor, relay, or other component. The “Bruh multisensor” is a popular project that pairs a NodeMCU with a PIR motion sensor as well as temperature, humidity, and lux (light level) sensors in a very small package.
Disadvantages:
As the WiFi protocol was not designed for home automation uses, WiFi devices are power-hungry. While it’s possible to power them from batteries, the batteries rarely last long – days to weeks. An alternative, for some devices, is to shut down until needed, but that causes delays, as the amount of time necessary to re-connect to a WiFi network is significant. Therefore, if there’s no way to run power (5V via USB is usually sufficient) to a particular device, WiFi is a poor choice for the application.
Most WiFi devices, as purchased, use firmware that talks only to the manufacturer’s cloud server, leading to all of the problems discussed in my prior article. Flashing aftermarket firmware is a must, and that requires some computer knowledge and a willingness to tinker. There are two specific FOSS firmware projects that I use: Tasmota, which is the more established, and more universally usable firmware (but requires an MQTT server), and ESPHome, which is newer and is meant to work specifically with Home Assistant – not sure if it can be used with any other hub. This is one of the two places we lose the “Easy” designation. The other place is:
Most home WiFi infrastructure is insufficient for a WiFi-based smart home. If you are only using a handful of devices, you’ll likely be fine, but if you plan to have dozens, or hundreds, you’ll probably need to upgrade to better routers, switches, and access points. I am planning on another article dedicated to just this topic, but it’s the other major place where WiFi fails to be “Easy”. The good news is that putting in the right infrastructure is very doable and will not only give you the ability to use hundreds of WiFi IoT devices, but will also improve your WiFi performance in general and improve the security of your home WiFi network.
433MHz
Devices based around 433MHz are mostly used by older alarm systems, ceiling fan controllers, wireless doorbells, and other older and lower-end systems. However, this doesn’t make the outdated – for some applications they are still top notch. They will require a 433MHz receiver or transceiver to connect to the rest of your system.
Advantages:
Very cheap. Purchased on Banggood, a 433MHz door/window sensor can be had for as little as $1. Even on Amazon they can be had for $3-4.
Very low power usage. These devices are built to work with batteries and a single AAA battery can last for a year or more in a door sensor, even a frequently used one. In part, this is because the device often shuts down completely between uses.
Can sometimes be used to connect old, “dumb” devices to your smart home. A number of old systems that use 433MHz for internal communications can be repurposed. For example, some ceiling fans that came with proprietary remote controls use 433MHz signals. Your system can learn that signal and put the fan under the system’s controls without needing to rewire anything.
Uses the 433MHz frequency range which is fairly quiet and not subject to interference from WiFi or cell phones.
Disadvantages:
You will need a 433MHz transceiver. I am currently aware of three: the Broadlink RM Pro series of IR and 433MHz units, the Sonoff RF Bridge, and RFLink. I’ve not used the Broadlink units, but both the Sonoff and the RFLink have some issues. The Sonoff works very well, but is very limited in which devices it can work with. Unfortunately, there’s no way to tell ahead of time, except by asking around on the forums or trial and error. On receive, it just won’t “hear” some devices. On transmit, it’s limited to only some devices and also has a limit of a maximum of 16 commands it can send. There is a hardware modification that can be done to it that allows much broader capability, but I’ve not tried it yet. The RFLink is by far the most capable one, but the RFLink project itself is only the software – you need hardware to run it on. You can build it yourself, or there’s one vendor for ready to go kits, Nodo Shop. Unfortunately, both the project and the store are based in the Netherlands, and while there are English-language versions of most of the docs, some are missing and some are outdated. I got one working after a lot of poking at it, but never got sufficiently good performance to justify using it over the Sonoff. I might go back to it at some point.
You will also need the codes for the devices you use. Some can be found on-line, others you can try to capture by reading the raw data received by the transceiver. Not horrible, but a significant pain in the neck.
Lutron Caseta
Although not a standard protocol, this one deserves a mention for the sole reason that I use it. Lutron is a major lighting company with at least three lines of “smart” switches and dimmers, none of which work together. Caseta is their cheapest offering. While it violates some of my preference for FOSS and completely local control, the advantages of Caseta outweighed it for me.
Advantages:
Extremely reliable. All of my Caseta units have just worked. Every time. Well, except the one that arrived with physical damage to the unit, but even that one worked as a smart switch, it was just the physical button that didn’t function.
Extremely fast. Probably even more responsive than WiFi units, these change state and report changes back instantly.
Uses 431-437MHz frequency range which is fairly quiet and not subject to interference from WiFi or cell phones.
Works in some complicated 3-way and 4-way lighting situations. Many smart switches, and almost all smart dimmers require a neutral connection to function. In the US, many older houses (or poorly wired newer houses) don’t have a neutral wire in the electrical boxes holding some light switches. This can cause problems for any smart switch, but when you start talking about 3-way or 4-way switches, you often need neutral in every switch box to make things work. Additionally, there are some ways to wire a 3-way light switch that make it impossible to use with most smart switches. This page shows most of the different ways to do so. If your home, like mine, has one of the two bottom ways, the ones labeled “3-Way Switch (Power into Light) most smart dimmers just won’t work. Caseta dimmers, however, work because they “cheat”. Essentially, you can install just one Caseta switch or dimmer to control the light, and take the rest of the switches out of the circuit entirely. You can then use Caseta’s Pico remotes to fake the other switches. These little remotes can be installed into an electrical junction box and look and act just like the full-blown switch, but with no physical connection at all. The remotes are battery powered but the batteries are supposed to work for years.
Disadvantages:
Proprietary protocols. Nothing else uses Caseta signals and it can’t use any other devices.
You will need a Caseta hub. Specifically, you’ll want the Caseta Smart Bridge Pro hub, not the cheaper Smart Bridge. This is because only the Pro hub can be connected locally to other systems, like Home Assistant.
You are not completely independent of the manufacturer or the internet. With the Pro hub, all control is local, with Home Assistant (or other device) communicating directly with the hub, which then transmits to the switches/dimmers. However, to pair new devices with the hub you have to use Lutron’s mobile app. So if Lutron shuts down the product line, you’ll be unable to add new devices, but at least existing ones won’t stop working.
Expensive. At the time of this writing, the cheapest switches and dimmers are about $50 and $60 respectively, and the more expensive ones that handle LED lights better are $60 and $110.
Conclusion
So, what should you use? Well, that’s for you to decide. My personal approach is this: I use Caseta for in-wall switches and dimmers. This is partly because of the 3-way issue, partly because I didn’t know about the WiFi options when I started down the home automation road, and partly because my spouse has gotten used to them and wants all the switches to be consistent)
For all other applications, I use WiFi devices anywhere that I can run some power. Where I absolutely cannot run power, I use either 433MHz devices (mostly for door sensors and basement flood sensors) or Z-Wave (mostly multi-sensors).
You should choose what fits your needs best, but, as I’ve said several times now, if you decide to follow my path down the WiFi road, do it right. Upgrade your infrastructure and flash the devices with open source firmware.