There are a couple ways to do this but I use this formula based on the “kelvin” value of this app (sorry it’s in Dutch, it’s the “calculate” build in logic thingy):
This exact formula gives a value between 0 (cold) and 1 (warm) depending on how strong the sunlight should be without clouds on any given day (so it’s not ACTUAL sunlight, FIY). Als keep in mind that 0 is really cold, so you might want to tweak it to only let it go to 0.25 or something in your case if you don’t like the “hospital” light the 0 value gives. For me it translates to something like this (the curve is obviously bigger in summertime because the days are longer):
And to change any given lamp you just let a flow run every five minutes (or on “kelvin change” or on “lamp on”) to change the temperature of all the lights to the relevant kelvin value of the moment:
I also let this kelvin value have a tiny effect on the brightness of my lamps (a gradual +0.1 when kelvin is highest and +0 when it’s lowest), besides also mainly using lux sensors to auto change the brightness (where more light outside means the lights inside get brighter as well). Because only changing the temperature was not enough for me. I also want bright lights during the day and dim lights when it’s night (automagically).
This works really well in my case but you might have to experiment a bit for your specific setup (I use mostly non Philips Hue brands of smart lights).
