The Inner Workings of LED Grow Light
You’ve seen them on TV screens, clocks, traffic lights, indicator lights on your phone that tell you the battery’s empty… LEDs. You can just as well think of them as teeny tiny light bulbs, only they don’t have a filament (that wire-thingy in the middle).
We could talk ad nauseam about the differences between the LEDs and incandescent lights in general, but as far as indoor growing goes, LEDs blow all other lights out of the water. They run far cooler (though they do need heat sinks), have better power-efficiency and they recreate sunlight much more successfully, which, as you can imagine, is pretty damn important for growing plants. They’re not without flaws, though (higher price pops to mind), and another, more technical issue. However, before we get to that, we need to cover the basics of LEDs – or Light Emitting Diodes.
How Do LED Grow Lights Work?
To answer this question, we first need to know what LEDs are. So, what are diodes? Well, here’s where things get a little bit technical.
Diodes are what the community calls semiconductor devices, meaning they only conduct electricity under certain conditions (keep this in mind for later). Now, ideally, an atom would bond to its neighbor without leaving spare electrons, but we don’t want ideal conditions. That’s why diodes are “doped” (yeah, I know – LED grow lights, Mary Jane, dope) – in other words, impurities are added to the semiconducting material.
There are two ways you can do this – adding electrons (doping germanium crystals with arsenic) or adding “holes” for electrons to go through (doping germanium crystals with indium). These are called an N-type and a P-type material, aka anodes and cathodes for those who paid attention in physics through elementary. Working together, these encourage the electricity to flow through the diode.
In a stasis, all the electrons are busy filling up the holes, and all the holes are filled up, so that the zone between the two materials (N-type and P-type), aka depletion zone, effectively acts as a buffer, or a dead zone, if you will. How to liven up the situation? Easy, just put some voltage through. Now, it’s imperative that the N-type (anode) is connected to the negative end of the electric circuit, and the P-type (cathode) to the positive one.
This is where the magic happens. As the electrons travel through the depletion zone, they become excited and pass through the holes to either lower or higher orbital (energy levels, essentially). These jumps release a form of energy which you might recognize as photons. The rule of thumb here says the greater the jump, the greater the energy, and the greater the energy, the brighter the light.
Now, choosing one semiconductor over the other will dictate the color of the diode. Granted, some types of LEDs, like pink ones, are essentially white with pink plastic around, but they are a small, small minority.
For example (not to get too technical), we get red (also orange and yellow) from aluminum gallium indium phosphide (AlInGaP) with slight changes in composition, while blue, green and white come from indium gallium nitride (InGaN), in case you want to start making one from scratch.
On a more serious note, though, LEDs have a spectrum of colors far superior to that of incandescent or other kinds of light bulbs, which makes them so well suited for indoor growing. They range from near-ultraviolet, through the entire visible spectrum, to infrared and white LEDs. So far, we know for a fact that reds do affect plant growth, but if you feed your plants only the red side of the spectrum, you get stunty growth. On the other hand, blues and greens encourage growth, but they’re virtually useless during blooming when reds come to the fore.