Looking for a lux sensor but that simply doesn't exist. I've quickly learned that just relying on sunrise-sunset or something along that line for varying lighting or intensity isn't the best.
Right now all my motion sensors do NOT have lux sensors. Partially because I bought them early, but also specific model choices/form factors. Additionally, placement of the actual motion sensor may not be ideal compared to where I'd want to measure lighting. I've also heard that some of the cheaper ones that have motion+lux may not reliably report lux immediately before motion event, sort of making the lux reading pointless?
Yet it seems (or I am failing massively at finding) there is no such thing as a standalone lux sensor? Is there simply a really small and affordable zigbee/z-wave sensor I can have reporting lux periodically?
The Hue indoor motion sensor reliably reports lux without motion. I use one on a windowsill pointed out. Battery lasts over a year. It pairs directly, no Hue bridge required.
My Zooz ZSE11 multi sensors report lux. They do not require any motion to do so.
I have them primarily for humidity, but also use one to tell me if I forget to turn off the light in the crawl space. Mine are plugged in but they can also operate on battery.
They allow for setting the amount of change that triggers a report
I have it set to report at 1% humidity change, 1 degree F temp change, 10 Luminance change and motion set to sensitivity of 6. They report all of those changes, plus if there are no changes, they send a report every 4 hours.
So yes, you will get an event on change in lux, even if other things do or do not report. You can write automations based on the lux level reported from these.
There are stand alone lux sensors. For some reason this gets wrongly declared over and over.
Type LUX in search and you’ll find multiple posts about stand alone lux sensors.
For the cost of a fully stand alone vs a multi-sensor or a motion sensor with lux capability,
it is both more cost effective to produce a device that has multiple capabilities, and for the consumer to buy one.
In most devices they would be two separate things. So when using a combo unit just use the lux attribute as your trigger. That said, there really isn't a lux standard so you will have to eyeball things. What I mean is put the device where you want it, wait for the lighting you want and note the lux attribute, Once you have that , write your rule when lux=whateveryouwant do this...
It is correct that certain motion sensors only report LUX when there is motion. The HUE outdoor motion sensor is one such device that I know does report LUX regardless of motion. I have three of them and can confirm this is correct. The indoor Hue motion sensors may act the same, but I no longer own one of those and cannot recall if that is the case them as well. I never used the indoor Hue motion sensor outside of the Hue bridge, and didn't have the means or need to acurately track its LUX reporting at the time when I owned one.
Here's graphs of my three Outdoor Hue motion sensors. In the samples shown, only the front motion sensor would have been actuated by movement. The LUX of the front yard motion sensor fluctuates less becase it is shaded most of the day at this time of year, until a brief period when the sun shines directly on it.
I use the Xiaomi Mijia Smart Light Sensor Zigbee 3.0 linked above. I have it stuck facing west in a skylight well. I used lux/illuminance provided by a weather provider for a long time before this, but this works just as well. When it gets dark, the numbers drop pretty quickly, so finding where that threshold is takes a few days of trial and error.
The Aqara one you linked is different (newer) -- it's dome has a much larger bulge. But at least you can still buy it.
The Mijia link you gave is for the same GZCGQ01LM model I have. But it's out of stock (even at your link). And you can see that the price was nice - about $12 each, compared to almost double that for the Aqara.
Probably not enough demand for just a lux sensor so manufacturers added it to existing sensors. Honestly the gold standard, is probably the Phillips Hue indoor or outdoor motion sensor with lux. I only have the outdoor version though I use one indoors. It is also the only motion sensor I have found that works in my basement without false motion triggers. These extremely high quality sensors and are the only device from Phillips that I would pay the premium for.
Depending on your use case I use two lux sensors to cover my whole house. One is facing east to grab sunrise, the other is facing south to help my HVAC and motorized shades control temp in my house. I live rather far north so that direction doesn't matter and my neighbors house blocks direct light from the west. These are the only two lux sensors needed to reasonably build automations for me.
A different form factor is the Sensative Strips Comfort - Temperature and light sensor. It's an overgrown popsicle stick. Completely sealed and weather proof. It's a pretty unique design being almost flat, about 3/4 inch wide and about 8 inches long. Z-Wave Plus.
My experience with their contact sensors is that the battery lifetime claims are a bit excessive. I have one of these in my attic used to trigger the attic fan when the temperature exceeds 100°F. It reports Lux on a change which, in my application, is every time someone turns on the attic lights. I used their contact sensors for years and found them dependable but the pairing and resetting process, which is done by sliding a magnet along the body of the sensor, was very frustrating. Enough so that when the batteries died on those I replaced them with a different product.
Disregard my recommendation of the Tuya motion/lux sensor as it does not update lux until motion is detected. Just tested it myself. Put the sensor in a dark room. 30 minutes later I used HE to turn a light on in that room. Verified with a camera in that room the light was on. The Tuya sensor reported 0 lux.
"Only 0 left"
