Blog

What Makes a Thermostat Smart?

Figure 22 – Making a device smart 

What makes a device smart? A thermostat is a great example. You can have dumb thermostats that that don’t do anything as well as thermostats on the wall that dial the temperature up and down. These dumb cheap thermostats don’t do much but are great for manual fiddling.

The user interface to a smart thermostat is provided by software, not hardware. This is an open-source thermostat interface which is similar to a nest, except that I still have a clunky programmable thermostat on the wall. But because it is a Z-wave thermostat I can find software for it that gives me the interface of a Nest thermostat, without the additional hardware cost. I can check on the thermostat through any device, cell phone or desktop, provided that smart hub is connected to a network. I can program with the thermostat. All of this advanced functionality does not come with the thermostat out of the box, it’s an  added value that comes with connection to a smart hub. 

Before getting started on a thermostat swap, be sure to power down not just the thermostat and outdoor unit, but the indoor unit as well. Failure to power down the system can blow a fuse in the indoor unit which will need replacement for the air conditioner to work. The fuse can be purchased at a local hardware store, but it is easily avoided by not rushing into the project.

Figure 23 – Thermostat Types 

Programmable thermostats are hated by many. They’re clunky and difficult to program but with the right peak versus off-peak rate structure, programming the thermostat correctly can result in real savings on the electric bill. But not all thermostat adjustments are easy. A proprietary “smart” thermostat may not have all the functions needed for easy programming.The Nest may be programmable for different zones at different times of day, but a regular programmable thermostat can do that too. But is a Nest solar friendly? Does it increase the air conditioner when the electricity is otherwise being sold for cheap back to the grid? Can its programming account for holidays or just days of the week?

Figure 24 – Smart Thermostat Functions 

A true smart device to me is one that can communicate with the other smart devices on your smart network, making it easy for this communication to result in computer-driven automations to do useful things. That doesn’t have to be a Nest. It can be a $40 clunky programmable thermostat so long as it has a Z-wave antennae.

After pairing a smart thermostat into the smart hub and enabling voice services, basic voice commands should work immediately. The smart hub provider often provides an automation menu for basic automation programming. But advanced programming features may require access to the software source code, so that you can program an energy automation such as to run the air conditioner harder when the solar array is being over-productive.

Zwave and Zigbee vs. Wifi

Figure 18 – Batteries vs. Hardwired 

When I jumped into a smart home project, I was taken in by the nber of battery-powered, wireless devices. I thought hardwiring all the devices was best avoided. But it is not just a matter of battery replacement although battery replacement is a big issue. And not every single device will experience the need for swapping the batteries, typically it is the regularly used devices that conse more power. But here is an example of a sensor that is not just a motion sensor, but also a vibration sensor, as well as a humidity sensor. It’s also measuring how much light is in the room, which could drive an automation to dim the light according to natural sunlight. 

That’s a lot of sensing stuff going on. The vibration sensor is an anti-theft device so is it needed in all cases? It might be better for energy consumption if a motion sensor is just a motion sensor. A multisensor may not be the right tool for the job, even if it only costs a little more than a more simple sensor. All those additional things take up more energy and that means you’re swapping out batteries more frequently.

Although, if you hardwire these sorts of devices, they’re great. Many battery-powered smart devices come with usb ports for hardwired power. Only detached sensors like window

or door sensors really need to be battery powered. Or perhaps there is some flexibility here, as the USB port would allow for a very large external battery pack if a sensor to reduce the need for frequent battery swaps. The user will simply have a better experience with hard wired powered devices. 

Figure 19 – Zwave and Zigbee 

Another problem with some wireless smart home devices, such as lower than wifi frequencies like Zwave or Zigbee, is that the wireless devices are mesh rather than point-to-point. This means the devices rely on neighboring devices to relay their messages throughout the network, but the important thing to know about that, is the repeater stations need to be hardwired.

You can’t have a 100% wireless zwave or zigbee network, some of the sensors need to be hard wired otherwise they won’t be able to relay their messages back to the hub. So if you jump into a smart home with a bunch of battery-powered, wireless devices you’re going to have a bad time. You need to throw at least some hardwired devices into the mix.

Non-wifi wireless platforms like Zwave and Zigbee aren’t necessary if you trust your wifi security system, and can have worse performance than their higher energy wifi counterparts. But ultimately I choose Zwave or Zigbee devices when I need a generic product that can be integrated into a smart home system without dragging me into a cloud service provider. So at the very least, these non-wifi platforms make a good starting point for a smart home build. 

Figure 20 – Wifi vs. Zwave vs Zigbee 

Wi-fi operates at a 2400 megahertz or 2.4 gigahertz frequency, with new wifi going in at 5Ghz. Both Zwave and Zigbee are around 900 Megahertz. What does that really mean? Those old enough to remember hard-wired telephones as they transitioned to wireless corded handsets (before cell phones) might remember first generation product that didn’t have 20 or 30 feet of

range, replaced by a better phone later that had substantially more range allowing you to walk anywhere in the house.  Z-wave and zigbee use that same frequency range. 

So it’s not a new frequency and it’s not necessarily a better frequency than wifi. Wifi uses a higher frequency, which requires more energy for the same range. But wifi has a longer range than Z Wave overall, even if it means higher energy use. Maybe not all devices need that long of a range, but many do. Wifi can transmit more data, whereas Zwave tops out at around a 56k modem. Transmitting voice over Zwave would take up so much bandwidth it would not allow for any other Zwave devices to be on the network. Even though Zwave networks can hold about 200 devices at once, how chatty the devices are matters as do other considerations. 

Real time energy metering requires a lot of data. In the energy controller section to come, I select a Zwave consumption monitor, but I am using a small Zwave network. A commercial facility might opt for a wifi monitor instead. Alternatively, another common solution would be to run multiple Zwave networks. Part of the thrill and frustration of smart home design is like  computer programming, there are many solutions to the design.

I don’t think the technical argents of Zwave or Zigbee are enough to justify the technology over wifi. Having fine-tuned sensor settings is more important for energy consumption, and while these settings are adjustable in the open-source software I use, you still have to figure them out and then set them up for each device custom. Later we’ll talk about a security hub that even has a z-wave or zigbee antenna for external device compatibility, but the company’s own sensors are on the 2.4 gigahertz wifi frequency, so what does that tell you about their decision as to which is better? 

Z-wave or zigbee make a good starting point, and there aren’t many wifi solutions that don’t draw you into a cloud service, so again, Z-wave and Zigbee make popular smart home starting points and then ultimately a large project begins to look for wifi solutions for a more stable, less limited communication solution. 

Energy controls also make a good starting point, because smart technology can save the end user money. National Renewable Energy Labs states that the majority of the population will embrace energy efficiency products which yield a 1-2 year payback. Unlike solar, an energy controller will never eliminate 100% of an electric bill. But in a similar fashion to batteries, it can actively shift a portion of the electrical load from peak to off-peak use, for substantially less cost than batteries. 

With an energy controller, the energy data is not simply monitored, but also acted upon by turning the right devices on and off. If everything necessary to do so is on a z-wave

Network, then energy controls can be implemented without requiring access to custom wifi. 

This means the systems can be pre-programmed and tested offsite before installation, reducing the technical difficulty in the field. Certain customers may not allow smart devices to access their networks, yet nonetheless have a need for onsite energy controls. 

Figure 21 – Wireless Frequency Comparisons

Z-wave or zigbee systems represent less of a threat to a corporate network, especially if they do not have wifi capability. Without the right antennae, it makes it impossible for one smart wireless device to hack the other. Likewise hackers are less interested in these systems as there is less valuable information – wifi devices make for bigger fish.

But although Z-wave or Zigbee can have encrypted communication, that requires more data bandwidth so  a large encrypted z-wave or zigbee network is not feasible. Certain devices, such as door locks, require encryption. But encrypted pathways can only be relayed through encrypted relay stations. So for a door lock, is it more secure to be Zwave versus wifi? The answer might depend on user priorities, but I would lean towards higher end wifi. I would only recommend a Zwave door lock when the lock is located within the same room as the hub, so at the very least Zwave door locks may not be well suited for projects where more than one lock is required.

So even though Zwave may have encryption, that doesn’t necessarily mean you are going to use it. Wifi devices are simply more capable than Zwave at crunching the nbers through a data network. A better product may be one that accepts this fact and makes up for the increased energy use with a larger battery. Again, the main reasons I select Zwave or Zigbee devices is that I know the devices will be smart and not attach the system to yet another cloud service.

Smart Light Switch Basics

Figure 12 – Light Switch Locations 

But as to the devices themselves, there’s no reason to over do it while getting started. It’s nice to think about living in the Jetson’s home, but National electric code does require at least one switch controlling the light on the wall, and as a practical matter if the smart home network crashes, you want a manual override. 

While a smart home can add a wall switch for a light in a convenient place, to make up for an inconvenient place, it’s a little more complicated than meets the eye, so I do not recommend envisioning too many fundamental changes in the way we wire our homes. Light switches will still be on the walls, but perhaps we have fewer of them. Maybe the best solution is to have all the light switches in a room in one central location, as a manual override. With enough box space behind them for any kind of future lighting controller. But even if we swap out most of the light switches in the house with wifi-talking smart buttons, those smart buttons will still benefit from a hardwired power supply. That brings us back to what most would consider obvious, that one way or another we will still have hardwired power in our homes. 

Figure 13 – Traveler Circuits 

Dumb light switches, in cases where more than one switch controls a single light bulb, are like a double-side railroad line with only one train on the track. The light switch alternates from on to off, and that switches the side of the track (called traveler wires) that the electricity is on, down to the device itself. It is a literal, manual on-off switch. 

Figure 14 – Behind-the-switch Lighting Wiring

A smart switch is fundamentally different in that the power goes into the controller and then the power out to the device, skipping over the actual toggle switch on the wall. Not all switches physically regulate actual electricity, some are low voltage relays that trigger an external switch. When retrofitting an existing lighting circuit with smart switches, the power lines are intercepted by the control board, and the light switch itself is rewired as a low voltage relay. Rewiring the lighting circuit is always possible, but the installer might have to cannibalize the traveler wires to use as low voltage relay circuits and it’s not a simple process. 

Figure 15 – Different Lighting Styles 

While I have found these behind-the-box controllers to be better than the switch replacements, I have also found them too complex to install and recommend starting with a more basic switch replacement, where the controller is built into the switch itself.

We don’t have time to talk about all those nuances in two hours, but the basics is that the actual power output is routed from the controller into the device, with the switch rewired as a low voltage relay. The electricity is no longer coming from the switch itself, but the controller is in fact hardwired to the building power supply. 

Figure 16 – Qualified Persons

There is potential for safety improvements in this kind of design, but it is also work that an electrician really should be performing, if the building owner is not comfortable self-performing that kind of work. An electrician is better at doing cable management and placement than a do-it-yourselfer. The controllers are allowed to go inside the lighting junction box, but only if they take up less than 75 percent of the cross-sectional area of the box. On a finer note, most controllers have reset buttons which need to be pressed if the system or device fails. When I install these controllers, I make sure I can access that push button with a push pin of some sort, to prevent having to undo a whole bunch of wiring to access that push button on the controller.

Although the light switch replacements I’ve used have not had reset buttons of any kind, but instead require flicking the switch up and down rapidly to initiate a reset mode, and I find that method much less elegant despite the easier access. 

Another option is to have a smart light bulb, where the controller is built into the light bulb itself

Rather than a smart light switch. That’s really interesting because it doesn’t require electricians, and keeps the building wires in place. Smart light bulbs are expensive, but by the time you factor in labor they’re actually worth it. 

The  major downside to a smart light switch is that like the controller, they need to have an always on power supply to work. So if the dumb light switch kills the power to the light bulb, then lighting automations would no longer work until the analogy switch is changed. The accessible switch on the wall then becomes a hindrance – smart owners resort to taping their lights on to prevent guests from ruining the automation, which reduces the usability of the home. It’s not an easy problem to solve, although smart light bulbs often have more features such as color changing and dimming, some of which can not be delivered by a controller that controls a regular dumb light bulb. 

Figure 17 – Adding Push Buttons

I don’t really know which solution is optimal, maybe in the future all the lights in the room will be on one manual override panel, similar to a hotel conference room, with motion detectors and voice commands making up the difference. There are wireless touch plates you can get for the walls, but also, getting one manufacturer’s wireless touch plate to talk to another manufacturer’s lighting controller is not an easy task. At any rate, there are more simple solutions to implement today and we could get stuck trying to figure out the optimal wiring scheme of the future. Swapping out a few lightbulbs or wall switches and getting everything set up on voice commands is a pretty natural fit as a starting point and there are safe ways to do so without being an electrician, although other devices really do fall into the category of electrical work.

Cloud Services are Hard to Avoid

Cloud services are a popular model, because the manufacturer can deliver a consumer grade product at a relatively low price, in order to sell you subscription services. This isn’t all nefarious – there are some real time saving advantages to that business model. The convenience of buying a cloud service versus setting up a more technically difficult local service, or the stability or out-of-the-box functionality of a company with profit motive can result in a more finished product than when you build your own smart home network .

But sometimes for smart technology to do what you want it to do, you have to understand the nuts and bolts, so you can take these different parts and put them together into a system that is greater than the some of its parts. This may not mean a local system is more stable than a cloud service, but it can eliminate the need for an internet connection or reliance upon the manufacturer for support.

There are users who embrace the cloud and focus on internet security and that is a perfectly reasonable path to take, but there is also a smaller but healthy contingent of residential and commercial users who under no circumstance want smart devices and their companies spying on the network. While sometimes the local hardware can be cheaper, by the time you put in the programming, the local device will cost a little more and might be even a little less functional than its cloud counterparts. 

But there aren’t too many products out there for energy management, and to some extent it is a project that needs to be designed and built custom to the particular jobsite, so it can make sense to build a local energy controller. 

Now, a local device can still use wifi for wireless local communication. That can be a completely isolated wifi network on its own hub or antennae, or it can share the existing wifi, or most high end wifi routers can issue a separate virtual network, called a VLAN, for the smart wifi devices. We don’t have time today to talk in depth about network security issues, but it all comes down to password management and inevitably some user is going to want to connect to both the smart home network and the normal building internet and potentially bridge the two networks together. These points of connection can even be intentional – dedicated security gateways can be installed to monitor and control these points where the literal internet cable comes into the building. Well, we will have to talk about that further in another time and place.

But even Amazon and Google are working on getting their devices to store enough data on them locally to enable offline functionality, which means that some cloud devices do have local functionality. That’s not that’s not uniform across the board. But how often do you actually lose the internet anyway? 

Whereas backup power management begs for local communication. The internet might have failed because of bad weather. Adding a UPS system to the energy manager is not a bad idea. We’ll get to that later. For now, let’s simply agree there are a few reasons why an energy controller should be a local device. 

Turning your home into a living computer creates opportunities for hacking. A cloud connection can be hacked on the other end, which cedes up some user privacy inherently. But to some extent cloud services are inevitable. Voice command services are in demand – these can be local, but the local voice command services are being bought up by smart product developers, such as Sonos with Snips. Stanford has an open-access voice command service called Almond that is privacy oriented but it still requires more computing power than what most tiny computers are capable of running on their own. A local device might be capable of running a few voice commands, but inevitably the smart intelligence is going to be outsourced to a heftier machine. If you want a $40 thermostat to have voice features, it’s going to use a cloud service.

Voice commands are valuable – they promote health safety and welfare. They also promote laziness and comfort. You can get into bed and then turn the lights off rather than actually flicking the switch on the wall. Which to some might be ridiculous but for those of us who can’t keep the TV remote in the same place, being able to talk to your television to turn it on and off is quite wonderful. Voice commands are convenient and then from a disability standpoint voice commands can be liberating. One emerging smart application is enabling the elderly to live in their homes longer, because computers can automate some of the essential tasks such as locks, keys, and even speaking.

Getting voice commands onto devices that don’t have them already built in is what the “internet of things” technology is supposed to do, and it is actually easy to do. You don’t need to do much programming. Basically as long as the cloud service is compatible with the smart hub, then it is a matter of password management. Permission is given both within the cloud service software and the smart hub software, after which google or amazon or whomever sucks in all the smart devices from the hub into their platform (or vice versa), and the end result is the basic commands issued from the hub, like turning on or off a lightswitch or television, now become voice activated commands within Alexa or Google. It almost feels like magic.

One of the cutting edge features of smart homes is facial recognition. People can be disappointed by facial recognition because it requires so much computing processing power. It’s not an instant response that people expect with their sensors, and so facial recognition is likely going to be a cloud service. What I’m saying is that for those comfortable with cameras inside their homes, where facial recognition can be used for really advanced automations based on who is in the room, keeping the smart network local without any kind of cloud interaction is not be practical. And while  a simple local smart home service that is custom built doesn’t need to have privacy issues oriented with cloud services, a local service can still benefit from online interconnectivity whether it’s bringing in voice services or facial recognition or even just remote monitoring if you want to check in on your smart home when you’re away from the house. In most circumstances, you’re going to want an internet connection even with a local network. It’s hard to avoid.