Local Control or: How I Learned To Stop Worrying About Being Offline
Even if you’ve just been dabbling in Home Control. Have a full-blown whole-home system, or somewhere in between. You’ve probably heard a story or two about an Internet outage or a company shutdown effectively disabling someone’s system. By placing control in the hands of an entity external to ourselves. We make our systems slaves to our cloud overlords. Having local control brings the management of our systems in-house.
Let’s be 100% clear I am not anti-cloud. It’s perfectly acceptable for the odd smart plug or novelty lighting. Additionally for the foreseeable future things like Voice Assistants (Alexa, Google, Siri, etc) will require internet access to be able to process commands. Music, video and weather services also require similar access as all that data can’t reasonably be stored locally.
But what happens when the internet goes down, a service provider has an outage or as has become far too common shuts down their service entirely. The lights, switches, plugs, sensors, and scheduled events in our homes shouldn’t suddenly become expensive bricks. The landscape is littered with defunct equipment providers. Many of these were not small players either. Revolv, Iris, Insignia, or TCPi were all backed by some pretty big companies. So if you can’t trust that a large tech-savvy company can make this work. What are the chances that a smaller player can survive?
“The world is a raving idiot, … We must rescue ourselves as best we can.”
Thankfully it’s not all doom and gloom. Solid local communications standards do exist and are supported by the majority of consumer and DIY hubs. Some of these standards like Zigbee or Z-Wave are relatively complete solutions that offer device connectivity and software control as a single package. Other solutions like Wi-Fi or 433 MHz devices have only the connectivity portion in place. As a result, they need something like an API or MQTT in place to facilitate the software control portion. So let’s take a brief look at these options and a few of their pros and cons.
Local Control Protocols
433 MHz also commonly known as RF, is the oldest of these connectivity standards. Devices of this type have been around since at least the 1990s. While age has some benefits it also has drawbacks. Let’s take a look at both.
- Very long battery life
- Very inexpensive
- Best at wall penetration and distance at lower power
- A high variety of devices like security sensors, plugs or weather stations
- Weather stations almost exclusively existed in this format although that is rapidly changing
- One way communication
- This means you often can’t tell if a device is off, on, or even online
- No standard data format
- While there is some crossover most vendors have unique implementations
- Extra DIY hub or commercial unit with 3rd part firmware generally needed.
- Homey and Vera do have 433 MHZ radios built-in
- Depending on your automation controller a direct integration may be available but most often
- No security data is broadcast in the clear
- Generally, no battery status reported and must manually be confirmed
- Each device connects directly to the hub no mesh capabilities
Z-Wave broadcasts in the 900 MHz range. The exact frequency varies from country to country. It is a closed standard owned by Silicon Labs. First introduced in 2003 it wasn’t until the early 2010s that more than a handful of products were available. At this time there are 1000s of devices that are Z-Wave certified. The specification has received one significant upgrade in 2015 called Z-Wave Plus, which among other things promised increased battery life. For more on the standard see the Z-Wave Alliance Website
- The strictly controlled standard ensures excellent inter-device compatibility
- Long battery life
- Sub GHz frequency gives good distance and penetration. Up to 35m
- No interference from Wi-Fi
- Mesh network allows devices to be placed as far as 4 hops from the central hub
- Hard device limit of 232 devices including the hub
- Most expensive option due to it being a closed standard
- Lowest bandwidth of the modern standards
- It requires a central hub to facilitate communication.
- Because of country-specific frequencies devices from one area generally do not work in another.
- A hub is required although many home automation controllers have it built-in.
Zigbee broadcasts in the 2.4 GHz range. This frequency is effectively the same worldwide. It is an open standard with broad industry support. The first version was ratified by the IEEE in 2004. It has received consistent updates with the most recent being Zigbee Pro 2015 aka Zigbee 3.0. There are once again 1000s of available devices. Zigbee has 3 basic types of devices:
- The coordinator (ZC) This is the hub and there is only ever one. It defines the start of the mesh network.
- Routers (ZR) This can be any type of device plug, light, etc. It can pass data from one device to another
- A router is a device that is always powered on in order to maintain the mesh
- Some inexpensive devices are just routers to extend your mesh
- End Device (ZED) This will almost always be a battery-powered device. It connects only to one other device either a ZC or ZR. These devices can sleep for extended periods of time. Only waking to send a state change, allowing for very long battery life
- No official device limit but effectively capped at a whopping 65,535 devices.
- Different ZCs have varying maximums of ZEDs that can be directly connected to them. Generally 15-30 this number is extended by the introduction of ZR devices which can then take on a similar number of ZEDs
- Longest battery life
- Greater bandwidth than Z-Wave allows for more data to be sent in a shorter time.
- Due to the low cost of entry more and, more companies are creating Zigbee devices all the time
- Older devices have bad interoperability. The standard previously didn’t require full compliance to call your device Zigbee.
- Zigbee 3.0 changes that requirement. As such vendors who previously “did their own thing” are now releasing compliant devices
- Shorter range than Z-Wave at about 10m but with well-placed routers, this can be overcome.
- A hub (ZC) is required and can be found very inexpensively even in speakers like the “Echo Plus”.
Wi-Fi like Zigbee broadcasts in the 2.4 GHz and 5.8 range. With very few exceptions all smart home devices use bands in the 2.4 GHz range. While the network layer is standard, the actual communication varies dramatically from manufacturer to manufacturer. While Wi-Fi is generally considered a hub-less solution. It does require that you have better than average access points within your home. Beyond a half dozen or so devices the router that comes with your internet will not cut it.
Until recently the only way to achieve true local control was through various hardware and software hacks to load alternative firmware. In recent months a handful of manufacturers have started to provide methods of cloudless control. This is definitely a step in the right direction but will likely be limited to smaller independent companies.
- The cost of entry is lower than Z-Wave and Zigbee.
- Hub free connects to your existing wireless network.
- Devices are available everywhere.
- Most devices require hardware or software manipulation to enable local control.
- Local control usually comes at the cost of their cloud functions.
- Devices generally need a constant power source or very large batteries as Wi-Fi is power-hungry.
- Very dependant on router/access point quality a cheaper router will result in an unreliable network.
- The channels assigned to Wi-Fi are very crowded. Although as higher-powered devices like laptops and phones move to 5 GHz this should lessen.
- If you ever need to change your SSID or passphrase you will potentially have to re-setup all your devices.
So What Should I Choose?
There’s no right answer to this question, as everyone’s needs, home construction type and willingness to modify/tinker will differ. Also, I don’t generally consider the need for a hub a downside as Wi-Fi will require better access points. So it’s effectively the same issue. Often you will end up with a combination of a couple of technologies. So we’ll just go with a few points to consider.
- If starting from scratch avoid 433 MHz devices unless there’s no other option. The lack of security and standards make them undesirable in my mind.
- If you have a home that already exhibits issues with Wi-Fi signal you may want to consider Z-Wave as its lower frequency will potentially penetrate your walls better.
- If you intend to include sensors like door contacts, temperature/humidity or motion sensors. Then Z-wave or Zigbee will be better as they can run a long time on batteries and will alert you when they are low.
- Between Zigbee and Z-Wave. Zigbee seems to be getting the lion’s share of new devices and support from the bigger players. Also in most instances, the devices are cheaper as no licensing fees are required to create new products.
- Finally, if you are willing to take the time to replace the software on devices and build-out a better Wi-Fi infrastructure. Then for things like switches, lights and plugs Wi-Fi has the lowest cost of entry.