I want to automatically switch on lights if room gets dark on a cloudy gloomy day. don't want to trigger based on motion - instead want to use light level. I installed a Philips Hue Motion sensor - which added a light level sensor in Home app - but not able to use that to trigger an automation. any suggestion?
time based automation works for sunset - but not sure how to handle cloudy days. additionally during fall and spring (when sunset time changes drastically), time based automation did not work quite well.
I've had my home set up this way for over a year and it works great. The key is different "on" and "off" levels, so you don't have flap happening during the time when the light level is right at the trigger point.
There's a free app in the app store called Hesperus that, with a long-press on the light level, lets you type in a value. Most other apps give you a slider, and are useless for light levels because you generally want triggers in the 20-30 lumen range and sliders don't give anywhere close to that level of fine control. Hesperus lets you set the whole automation up, and when done, it appears in the Home app. (Like all new automations, it takes time to propagate to the hub unless you log out/restart/log into the hub again).
Light thresholds depend on your windows/setup but for mine, I set the "on" at < 25 lux, and "off" at > 36 lux and I've been generally very happy with the results. I use a Hue sensor, coupled with hue lights and a lutron caseta dimmer, all via Homekit.
Hope this helps.