Schinckel.net

I really like home automation. Being able to see when things are turned on, and being able to turn them off remotely, or build automations around events in the home is fun. I’ve built a garage door opener, a bunch of temperature, humidity and air pressure sensors, and played around with various light bulbs and switches.

I haven’t invested deeply in any platform: for a couple of reasons. I have some of the Sonoff devices, and like that it’s possible to flash my own firmware. This allows me to lock down the device so it can only connect to the one MQTT broker in my network: indeed, my IoT devices are all on a seperate network that has very strict limits.

But that’s not what I want to talk about today. I want to talk about smart lights and smart switches, and why switches are superior.

I don’t live by myself. I have a family, none of whom share my level of excitement about smart devices, but all of whom need to still turn lights on and off. They don’t have an Apple Watch (or iPhone, in most cases), and should not have to use one to turn the lights on.

In fact, I should not have to use my watch or phone to toggle the lights either. We have managed as a society to come up with a really simple system for controlling lights: you flick the switch, and the light toggles.

Direct control of lights using the existing switches is the number one priority of a smart light system. Having a smart bulb that you can turn off using Siri, but then means you need to turn the switch-off-and-then-back-on to get it to turn on is not acceptable.

Likewise, requiring someone to use a smart device to turn a light on is unacceptable.

Having a switch that prevents the smart light from being smart (ie, when it’s off, you have to use the switch to turn it on) is also unacceptable.

This makes existing smart bulbs a non-event for me. Even if you have a duplicate “smart” switch next to an existing switch, there’s still the chance someone will turn off the switch that needs to stay on.

What is a much better solution is to have the switch itself be smart. In most cases, that means the switch will no longer be mechanical, although it could be a press button. There are a bunch of smart switches that perform this way: they work manually, but also still allow an automated or remote toggle of the state.

These switches will not work in my home.

Pretty much all of these (except one exception from Sonoff, see this video for a really nice description of how this works) require a neutral wire at the switch. It seems that my house is wired up with the neutral at the light only, and then only a pair of wires (live, and switched live) that travel down to the switch. Thus, the switch is wired in series with the live wire, and the neutral is only connected directly to the fitting. Jonathon does a really good job in the above-linked video of describing the problem.

There is an alternative solution. Sonoff also make another device, the Sonoff Mini. This one is pretty small (much smaller than the Sonoff Basic), and can be wired up and programmed to behave just like a traditional hallway switch: toggling either the manual or smart switch will result in the lights toggling. The nice thing about these is that they have the new DIY mode (just pop them open, add a jumper, and you can flash them without having to connect header pins). In fact, I even wrote a script to automate the process. It’s not quite perfect, but it’s been good for flashing the five of these that I currently own.

You can then have the mini connected up to the light (at least, in other countries you can do this yourself: in Australia this is illegal unless you are an electrician, so be aware of that), and have the switch connected just to the switch pins on the mini. Bingo, smart switches the right way. When the smart fails, the switch still works the same as they have for generations.

(Unless the microcontroller itself dies, but that’s a problem I have not as yet solved).

As an aside, I wanted to comment on the setup from Superhouse. It’s quite nifty: all of the switches are low voltage, and control relays back in the switchboard. However, it relies on the logic running in a computer (and running JavaScript!) to connect which switch to which light.

This to me feels wrong. It’s better than having those connections over WiFi, but it still means there is a single point of failure. I think the architecture I have used - smart switches that are independent, and if they fail to connect to WiFi continue to work just the same as an old dumb switch - is superior. It’s more like the philosophy I have with web pages: the pages should still work when all of the JavaScript breaks, but when it doesn’t break, they can be nicer (and have some cool affordances).

To that end, I’ve tried to make each little module of my smart home somewhat independent. For instance, having an IR sensor connected to the same microcontroller that controls the lights that sensor means that even if WiFi breaks, the lights still behave exactly the same way.