Color Temperature Sensor

So here's my situation: I have a fake window in my newly finished basement. Looks exactly like a window... blinds, curtains, window sill, etc. Except instead of an actual window it's LED tape lighting behind the blinds. I currently have it timed based on sunrise and sunset, and it works fantastically. (Almost everyone who has seen it has said they would never have known it was fake)

I'm looking to take the automation a bit further, and adjust the color temperature of the LED lights to match what's actually outside. My thought was I could add a z-wave device (or something similar) that would read the outdoors color temperature. So sunrise/sunset would be a much warmer color temperature, mid-day would be cooler, etc. Being able to adjust the brightness would also be nice.

Is anyone aware of a z-wave (or zigbee) device that can report color temperature?


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You're talking about circadian lighting. Several people have already done it. Some through RM or other means but I think this is probably your best bet. He is working on a new app and was looking for beta testers. You might want to send him a DM if you are interested. Although that was a little while ago.


Yes :slight_smile:

Still looking.

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What a cool idea! I'd have never thought of it. My office is on the top floor with a real window so I don't need it but I know others that do and I'll send them a link to this. Thanks!
:+1: :+1:

I’ve got a few windows in our house like that. I’m going to write a virtual sun app, since CD isn’t really designed for that purpose.


Adam's app sounds really promising, and I'd love to be included in a beta test phase.

A couple of qualifying questions: Do you plan on including the ability to support a device that can read color temperature (if one exists)? If not, is there another mechanism to determine light temperature? (e.g. weather service API that includes light index/temperature)

Another interest of mine, which is specifically why I was looking at a device, was to not only adjust the color temperature based on time of day, but also weather. Example: Yesterday it was overcast/raining the entire day here. Yet at 9am the fake window had some nice warm light coming through, but the real windows in the rest of the house were much dimmer with cooler light.

I have a very rough CL schedule already setup for the fake window through routines (sunrise is 2700k, 1 hour later is 3200k, 11am is 4000k, -2 hours sunset is 3200k, -30 minutes sunset is 3000k, sunset is 2700k). But this obviously assumes "normal" weather.

Thanks for the feedback so far!

If you can find a device that can read color temperature, you bet I'll add support. Otherwise, CCT is more or less just simulated across time of day. Unfortunately, there's a lot that can go into CCT calculation (keep in mind the sky can shift outside of the CCT range (pink skies), and then there is G/M shift...), and sometimes the simplest solutions work the best :slight_smile: In conjunction with a luminosity sensor, this approach has been somewhere along the lines of good enough---especially for considering current cloud coverage.

You know.. I saw a sensor like this somewhere.. It wasn’t z-wave or zigbee, but could easily be converted.. I’m going to have to search for it again, this is an interesting idea.


It is. If there is a sensor it could probably be brought in via hubduino, mona lisa board, or similar easily enough.

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Or even fibaro smart implant

Digi-Key has this in stock.

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I think that is qty 3500 only though. but looking quickly, it seems that there are a bunch of potential other options.

Need to find a few minutes and do some google-fu and see which one makes the most sense.

how bout this:

Looking at the schematic, that should work - electrically anyway. Whether it is a good sensor/works worth a flip is TBD. :slight_smile:

if these spit out rgb discrete values, converting that to ct is not impossible, @bcopeland worked up some code for that before joining staff if I remember...

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