Then a lux sensor should work. There are lots of these: zwave, Zigbee, matter…
- Eve has a thread-based motion/lux sensor that works with matter, so should work with SmartThings out of the box with no custom code required.
https://www.amazon.com/Eve-Motion/dp/B0BZT5W3V5?th=1
If this is your first matter device, read the community FAQ so you’ll know what you’ll need:
FAQ: What do I need to add a Matter device to the SmartThings app? Do I need a bridge router device?
- If you prefer a plug-in sensor, third reality has a Zigbee option, but that one does require a custom edge driver, which you can get from them.
https://www.amazon.com/dp/B0C9LNXYLL/
- And yet another option is an Aeotec multi sensor, which is z wave. Some models can run off USB power or batteries. They have several different models with slightly different features. The new Tri sensor 8 is supposed to have the most accurate Lux sensor.
The Aeotec also has an optional add-on recessor plate which Some people prefer the looks of.
