Plants/Leds/And winter stuff

This probably doesn't have a lot to do with the last publication or the fact that there hasn't been anything here for a super long time but I wanted to share a few things that I have learned as a novice Arduino enthusiast, an amateur lighting hobbyist and an absolute fool on growing plants. My suspicion was that I needed a special kind of light source for my plants and, o was I schooled on how to properly grow plants.

First let me explain the situation. This year and last I got the opportunity to grow a garden close to home. It was all happy and stuff until the fall and it really made me upset that some of our plants hadn't grown sufficiently. Our onions didn't for sure. So we decided to bring them inside during winter.

I thought now the problem of keeping them inside is primarily that they don't get much of the sun. At first I thought that just any light would do. It turns out that plants make their own food through photosynthesis which is a very complicated process, and among all those complications, they have the need for a particular part of the light spectrum.

Light spectrum over a gray background to reduce chromaticity distortion (Thanks, Wikimedia)

At this point I was like fine any white light contains a mix of all the colors in the spectrum but it turns out that all sources of light have a color temperature and that color temperature also determines "how much" of a color that white light has. That's especially important for photographers as the quality of the color in pictures is largely determined by the presence of the right amount of colors in the light that they have available. In polar coordinates it looks a little like this

It turns out that plants have a very marked preference for red light but according to this awesome USU paper. I also learned that a pinch of blue light is also very important for the plant's growth. So in other words the temperature of the light color determines how much red, green and blue the plants will get and you want them to get plenty of red and some blue. I mention temperature because the way we measure the color of something is by estimating how hot it would have to be to glow that bright, as a general rule of thumb the bluer the hotter the light is.

As a small side note if you have ever taken a chemistry class you always use the blue part of the flame because that is the hottest part (unless you are burning something with copper).

Then I decided that for my plants I would use a relatively "warm" light. I specifically went with 3500K LEDs that produce a spectrum similar to this one

It has a pretty nice yield of red but I added a little bit of blue through a blue component in RGB ring of LEDs.
So far it's working great and plants seem to be enjoying their artificial and ugly sun.

Hi from the happy plants

Thanks to Adafruit for the NeoPixel ring
Thanks to Wikimedia and my phone for the pictures (All CC BY-SA 3.0)
And thanks to USU for the great paper on blue light and plants!