One of the things that really grabbed me when I started out in home automation many yers ago was the notion of lights coming on in a room when you were in it and, going off when you weren’t.
Back then it was nigh on impossible to do. Kinda.
Using hard-wired PIRs, I sorta managed to get that to work, but it was a bit of a kludge and wasn’t 100% reliable and could sometimes confuse people in the house, especially those that didn’t know the lights were automated.
Over the years, this got easier as I wasn’t the only person looking for solutions to this problem and, I know, it’s such a first-world problem it’s unreal but once you start down this rabbit hole you learn quickly there’s no end to it.
We started to see wireless PIRs that actually worked and were reliable as well as sensitive, but still, even to this day, for near-instantaneous recognition of the movement in a room, it’s hard to beat a pukka-wired PIR.
But where they fall down is where people don’t move for a long time, watching TV, reading a book and so on as if there is no movement, they do not react, and regardless of how clever you are with motion detection lights will go off as the system thinks there’s nobody in the room.
All sorts of solutions came up, using cameras with facial recognition, Bluetooth sensors and a host of other things, but what’s come to the fore is mmWave radar presence sensors.
I use these now, a lot. They are unobtrusive, easily hidden, don’t have privacy issues and have proven to be very reliable. You can go find out loads more online with your favourite search engine or video platform about how they work etc.
But not all are equal and here I will share my thoughts on the ones I’ve used but, after the Aqara FP1 and FP2’s all I’ve only used in Home Assistant so your mileage outside that system may vary. And, all Zigbee ones are used using Zigbee2MQTT, not tested on any other platform.
Aqara FP1
This was the first presence sensor I got a few years ago and it’s been okay.
It detects presence accurately most of the time but there have been a number of occasions where there’s been someone in the room but it hasn’t “seen” them if they’ve been still for some time. Or, if the sensor is blocked by anything at all, evensmall enoguh you’d not think it’d be a problem, it can be.
There’s a temperature sensor in it and it seems okay, out a bit but not horrifically but as I don’t use it for anything it doesn’t bother me at all.
On th whole though, a nice solid little sensor that is pretty reliable for the most part if not the best.
Aqara FP2
I have two of these, and as far as presence detection goes, the FP2 is a cut above the FP1, way, way more reliable in my experience.
The PITA bit is that, although in the Aqara hub you can see “targets” (people, pets etc) I need to connect these using Homebridge and you lose that functionality, that’s a shame.
Oddly unlike the FP1, the FP2 has a luminance sensor as opposed to a temperature sensor and it seems okay fo general use and I suspect so that you can run automations like, if the light level is XXX then turn on the lights and so on.
Don’t do that with the sensor in the room if you can avoid it; it’s very unreliable, use a luminance sensor somewhere that you know the light level will not swing wildly when lights go on or off.
But the FP2 I can heartily recommend if all you need to know is, is a warm body in the room or not though, do be aware that even a small dog or cat will register as a presence on them.
Tuya ZG-205Z
Cheap, cheerful and one of those “I’ll give it a go as it’s cheap” things from Aliexpress and named on my system as the “Dodgy Presence Sensor”, it’s used in my office and whilst I slag it off a fair bit as it looks awful, it does work and has proved to be pretty reliable. Just not as a presence sensor per say.
It does have some quirks though.
For example, it can trigger when it detects a presence outside the office, on the front driveway which is just plain weird.
Sometimes, it takes an age to recognise presence, if it does at all as it seems to depend on how close you are to it.
In my office, it’s fine; I sit pretty close to the sensor, so it works for me most of the time, but it’s not great at all and if you need to use this where you really need to have reliable presence detection, think about using something better.
They are cheap, there’s a plethora of formats they come in and are unobtrusive but, not that good.
On the upside, it acts as a Zigbee router.
Everything Presence Lite
This is a great sensor.
Rock solid and, I mean ROCK SOLID performance with all the calibration you could wish for, bar one thing.
Height.
I wish I could get the sensor to ignore objects above or below a height (no clue how you’d do it) if you could, you could get it to ignore pets, ceiling fans and the like, but sadly, you can’t, and it will pick these up.
But, that’s the only negative with this sensor I have.
You can set different zones up so that when you move from oen zone to another, different things happen or, where there’s more then one target it can recognise that and you can automate based on that. Given it’s so damned accurate this is possible and it’s easy to say, bring on different lights or groups based on where presence is detected in a larger room.
I can’t recommend this sensor enough and at the time of writing, for £28 it’s fantastic value as well.
Sonoff SNZB-06P
I’ve only recently started using this one but, so far it’s been pretty good.
I got it for use in my kitchen and after settling on the medium sensitivity as high was too much, it’s been good. It sees people fine and reports well and fast enough, so far very reliable.
And, for as little as £9 odds on Aliexpress I’d call it a bargain
In addition to the variable sensitivity (low/medium/high) you get an odd illumination of just bright or dim, I’ve no idea what thats about or if it’s any use as I don’t use it. And, you get the timeout for detection set in seconds.
It also acts as a Zigbee router, which is nice.
All round, a good little sensor so far.
Xiaomi XMOSB01XS
I took a punt on a couple of these because I wasn’t sure about the whole BLE thing or how that’d work and at £19 for one of these that detects presence using a battery, I was dubious about them.
It turns out I needn’t have worried.
These are, in my view, fantastic little sensors, so much so that I bought another couple of them as they proved to be very, very good, fast and reliable. Even if I don’t get the claimed 3 years out of the battery, I don’t care just so long as I'm not swapping batteries every few months, it’s fine as I get presence detection in areas where there are no mains, or it’d be unsightly to run cable.
It uses a PIR to fire up when motion is detected, and this helps with the long battery life, then it detects presence using the radar, genius.
So now, in all three bath/shower rooms, I don’t have to rely on motion detection but have full-on presence detection, making the automated lights, etc, in these areas far more reliable and consistent.
All you need to install it is a flat surface, use the included stickers to secure the (very good) magentic swivel mount and you’re done. After that ti’s just a case of connecting it to Hass with Bluetooth.
I rate this sensor highly as well, it’s unobtrusive to the point nobody noticed I had installed them, works very well indeed and is reliable in all my testing.
If you need sensors where there’s no power, these are a no-brainer.
Hobeian ZG-302ZM
This was another punt on Aliexpress. And, there’s no doubt a plethora of copies under different brands etc as there often is on there.
Essentially, this is a wall switch (no neutral) that has a mWave radar sensor built into it.
It’s not great. Not at all.
As a Zigbee switch it works fine, no issues other than for a mains-powered device it’s an end device, not a router.
As a presence sensor, it’s pretty woeful.
It seems to act more like a PIR than a presence sensor with near-instant detection of movement, which is great, but it times out really quickly and does not recognise that someone is in the room, even sitting right in front of it after a minute or two.
So these, if you think it’d be a neat solution as I did, are not the answer you’re looking for as it’s far from reliable other than to perhaps detect motion close to the sensor.