Category Archives: Kelvin

Hackitt and Bodgitt discover Healthy Lighting

Hackitt and BodgittThere has been a lot of talk in the press recently about the colour of lighting and it’s relevance to health.

As far back as 2012, the BBC reported that NASA were to test “space-sleep colour-changing lights” on the international space station and since then there have been a number of articles in the press suggesting that the colour of light at certain times of the day can affect everything from sleep to prostate cancer.

Of course newspapers have also claimed at one time or another that aliens landed on the moon but there is a certain amount of obvious logic in selecting the right colour for the right time of day. Everyone knows that due to atmospheric filtering, the sun appears shifted toward red at night – and it is quite feasible that our bodies respond to those colour changes. No, I don’t follow my star signs!!

KelvinRecently the papers were full of the news (as it there’s nothing more important going on in the world) that our lighting and our various devices such as tablets can affect our sleep and that you should avoid blue light in the evening and that light shifted toward blue in the morning can aid waking up etc. I subsequently found, thanks to readers, a boatload of APPs that do this colour shifting on phones – not a lot of use when you’re trying to take a photo and you’re mobile has gone all red, but probably a good idea when you’re trying to read yourself to sleep.

And with that in mind I set off trawling the web for more information and finally ended up with a set of RGB values which match “colour temperature” in degrees Kelvin. Now I would not be one to claim 100% accuracy here because for that to work with modern LEDs you’d have to be assured that the RGB values you poked into the LEDs would render accurate colours and I doubt very much that this is the case.  However, I’m going to suggest that what I’ve done here is “near enough”.

In our “Hackitt and Bodgitt” board described in the blog article “Home Control 2015” I’ve added a new command to provide white light from RGB LEDs which can be “shifted” by providing a value in degrees Kelvin from 1,000K (very orange-ish) to 40,000K (very blue-ish).  At 6400K you have a perfect representation of the more garish compact Fluorescent lighting and at 1,100K you have a pretty good match for dim candle-light – with all the subtle variations in between.

Hence with a simple command to alter the hue of white lighting, in our case initiated no doubt in a node-red command, we gain the ability to alter the lighting to the time of day.  Now, WHY would you use more expensive RGB lighting as against simple WHITE LED strip in your home of the future? I have a theory about white LEDs and it’s a theory increasingly backed up by anecdotal evidence that white LEDs don’t last as long as some manufacturers might have you believe. RGB LEDs on the other hand don’t seem to have that problem and have the benefit (we’re talking about modern integrated LED, not separate red, green and blue LEDs) of allowing just about any shade of any colour and in this case, any shade of “white”.

I doubt very much that due to this new lighting interest you’ll read “Peter Scargill becomes the first person to live to 150” but you never know, it might just be an aid to better sleeping and that has to be a good thing.

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