I like an automated house, with things happening automatically for convenience and simplicity.

For the most part, I try to have automations run with definite actions, such as when my office door locks or unlocks.

However, there’s a certain degree of power that comes from using motion detection, but I’ve found motion detectors to be inflexible for a lot of what I want, which is why I’m switching to presence detection.

What’s the difference?

Motion detectors are very simple devices that use PIR to pick up large movements, such as a person walking into a room. They’re good at generic things, such as turning on a security light or lights in a corridor that you’ve just entered.

But, motion sensors are terrible when it comes to someone sitting still, such as at a desk. I’m sure we’ve all had that situation where we’ve been the last person in an office, and the lights keep turning out. The general response is to quickly stand up and wave your hands, but who wants to do that?

Indeed, that’s the issue that I have in my office. I have a motion sensor that will turn off lights and the heating if motion isn’t detected, but I have to set the limit quite high, otherwise, tapping away at my keyboard will leave me in darkness.

A presence sensor is different, as they use millimetre wave (mmWave) sensing, a type of radar. This makes them more precise when it comes to detecting motion, but also allows them to detect tiny physical movements, such as a person breathing.

The difference is that you can sit absolutely still and a presence sensor will still know you’re in a room. It will only turn off when you move outside of the detection zone. So, you can sit there at your desk and your lights will turn on, and they’ll only go off when you leave the room.

More power

Presence detection is super powerful because it doesn’t rely on exaggerated movements, and my lighting example is just the first example. I’m currently building out my automation system with Homey and presence sensors to make my heating more efficient.

I use Tado X for heating, with individual room control. Largely, I have rooms set to a cooler temperature, and turn the heat up when I want to use one, using timers. That’s fine, but presence sensors are better.

Using Homey, I can tell Tado X to turn on a room when presence has been detected for more than five minutes (enough of a gap so that the heating doesn’t turn on when I walk in to grab something), and to turn off when presence isn’t detected for five minutes (again, enough time to pop out and grab a drink from the kitchen).

While presence is detected, the heating will stay on. And, because it’s presence detection, I can sit on the sofa and watch a film without worrying about the heating turning off.

Battery power for the win

A big difference with presence sensors is that there are now multiple battery-powered models available, whereas originally mmWave sensors were mostly USB-C powered. Battery sensors are cheaper and easier to locate, while Matter means you can connect them to the smart home system of choice.