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How Do LED Lights Work?

So you want to know about LED grow lights. 

And, as we’ve discussed, to make sure that you get the best grows ever, you should try to know everything there is to know about what your plants like (and don’t like).

What do plants love? (Repeat after me, class!)

Your “tomato” plants love soil, water, and light. There are two major varieties of grow lights that people use: LED and HID lights. We’re going to talk about LED lights.

LED stands for light-emitting diodes. They’re everywhere: TV screens, clocks, traffic lights… you name it. 

Diodes are semiconductor devices. Semiconductors are used to conduct electrical current.

Think of LEDs as itty, bitty light bulbs. Each light bulb is fit into an electrical circuit.

Unlike light bulbs, they don’t have a filament—you know, that little squiggly thing in the middle of a bulb?—so they don’t burn out.

Also unlike a light bulb, they don’t heat up in the same way. 

What the hell is a diode?

As we covered, diodes are semiconductor devices. They’re the simplest variety. Most have impurities to it. This process is called doping (we know, we know).

The conductor material in LEDs is aluminum gallium arsenide, aka a mouthful, aka AIGaAs. 

In its purest form, the atoms bond perfectly to their neighbours and leave no spare electron, which are negatively charged particles, behind. This creates a negative charge.

Sometimes people “dope” their semiconductors by adding more atoms to the mix. Either:

  • Extra electrons are added, creating an N-type material (because it has more negatively charged particles), or…
  • “Holes” are added for electrons to go to, creating a P-type material (because it has more positively charged particles)

Either way, this will leave your material more conductive.

N-type materials

In N-type semiconductors, free electrons move from negatively charged areas to positively charged areas.

P-type materials

In P-type materials, electrons “jump” around into holes and move to positively charged areas. The holes, therefore, seem like they’re moving from positively charged areas to negatively charged areas. 

Bringing it together

So, back to the diode: a diode is made of N- and P-type materials. 

Electrodes exist on both ends, but electricity only goes through in one direction. 

When there is no voltage going through it, electrons from the N-type material will fill the holes from the P-type material, as well as the little space between the two materials.

That little space, my friends, is called the depletion zone. Sounds hardcore, huh?

In the depletion zone, all the holes are filled in the diode. This means that all the holes are filled, and all the electrons are busy filling up holes. 

Bill Nye and Jay Z

Did things just get kind of nerdy-sexy here?

Anyway, because everything is filled, charge can’t flow, which means no light.

To light it up, you need to get rid of that depletion zone. And to do that, you need to force the electrons from the N-type area to the P-type area, and the holes to move in the reverse direction.

In sum, you need to get the N in the P and the P in the N. Nerdy-sexy, no?

Depleting the depletion zone

So, how do we do this? By connecting the N-side to the negative end of a circuit, and the P-side to the positive end of a circuit! (Note: if you connect P to the negative side, and N to the positive side, there won’t be a current. The depletion zone actually ends up increasing.)

Remember: the overall charge of the N should be negative, and the overall charge of the P side should be positive. 

The negative electrode repels the electrons in the N-type material (because remember, opposites attract, and samesies repel), and those electrons are attracted to the positive electrode on the other side.

The holes in the P-type material are then pushed towards the negative electrode. 

Once the voltage—which is the difference between two points in an electrical field—is high enough, or there’s enough of a difference between the electrodes are high enough, that’s where the magic is. 

The electrons in the depletion zone will come out to play once the voltage is high enough, getting rid of it altogether. This allows for a charge to move across the diode.

This is how LEDs light up.

How does it really work, though?

Light is actually made up of photons, which are the most basic units of light. They’re essentially the byproduct of moving electrons.

Imagine an atom. Inside that atom, electrons are moving around crazily around the nucleus, the “heart” of the atom. 

Think of electrons as cars, and the nucleus is the roundabout.

Electrons have differing energy, just like how some cars can go faster than others. The greater the energy, the farther away the electrons can move from the nucleus. 

Now, this gets a little confusing, so read closely.

Electrons can jump to higher or lower orbitals. 

To jump to a higher orbital, something needs to boost the electron’s energy. 

When an electron jumps to a lower orbital, the electron releases energy. This energy released is a photon.

The greater the drop, the greater the energy. The greater the energy, the brighter the LED.

Wait, come again?

Okay, remember when we talked about how electrons will move back and forth across an electrode? 

Remember how electrons will fill those holes in the P-type area? 

Well, those free electrons actually fall into those holes. And, like I said above, the greater the drop, the greater the energy. 

Having said that, photons are only seen when the diode is made out of a specific type of material, which will dictate how far the electrons would drop.

Infrared LEDs aren’t visible to the human eye; this is because the electrons in them drop a very short distance. This results in low frequency protons.

Visible LEDs, or VLEDs, use materials that have a greater gap, creating a greater drop, creating greater energy. 

That is how LEDs light up, and certain types of LEDs are invisible to the naked eye.

Except...

Okay, so now you know how it works.

But this is why you might not want to use them for your plants. 

LEDs are still a fairly new technology. Extensive studies have been done, and their effectiveness is still not really conclusive. 

A BCNL user/Resident Scientist Eldon Perdue led an experiment, and his results are pretty clear: 

  • LED-lit plants grew to be much shorter
  • 14 ounces of LED-lit plants were harvested
  • 21 ounces of HID-lit plants were harvested
  • HID-lit plants produced larger, denser buds from fewer plants

When it comes to LED, we advise that you use at your own discretion, and it’s not something BCNL recommends. 

Read Eldon’s entire study here:

http://www.bcnorthernlights.com/learn-to-grow-your-own/led-vs-hid-the-ultimate-showdown

And stay tuned for how HID lights work!

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