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How do LED Grow Lights Work?

Most simply, LED lights use a current passing through a semiconductor to produce light. The energy (in the form of light) is released from moving electrons inside the semiconductor. They used to only be available in the red, but now they are available in any color, ranging from ultraviolet to infrared wavelengths.

The invention of LED lights is credited to H. J. Round, a British man from Marconi Labs who, in 1907, was the first to experiment with, and observe electroluminescence. Fast forward twenty years to when the actual invention of the first LED light finally came about. But even the Russian inventor, Oldeg Vladimirovich Losev, couldn’t find a practical way to use the light. It wasn’t until 1955 that Rubin Braunstein observed semiconductor alloys, and six years later, Texas Instruments took over with a patent.

LED Colors

LED colors are made via electronic action occurring at the p-n junction. This junction is where the n-type and p-type semiconductor materials emit energy, resulting in the color of the light. This light wasn’t even observed until 1962, when Nick Holonyak, Jr., working with General Electric, witnessed the red LED light. His graduate student, named Craford, then invented the yellow LEDs and also made the reds and orange LEDs ten times as bright by the year 1972. Blue and white followed similar development, via other experimenters and companies.

The different colors of LED lights actually stimulate and trigger different types of growth in plants, for example:

-LED lights within the blue spectrum spur vegetative growth.

-LED lights within the yellow, amber, red, and far-red spectrums spur pre-flowering and flowering stages, which includes reproductive growth.

If you choose an LED light that has only red or blue lights, it simply will not get your plants to grow to their full potential, like a white LED light (also known as a full spectrum LED light) would. White LED lights contain closer to the full spectrum, making them more similar to the sun than single color LED lights. Even red and blue lights together will not do it. You need white LED lights.

So what exactly are the other types of LED lights, such as the 3, 5, 6, 11, or 12 band LEDs that are advertised? These LEDs have a spectrum that includes those gaps. They might be 440, 470, 525, 640, 660, or 740 nanometers. These lights do not offer the same full spectrum that a proper white LED light would provide.

Instead of white LED lights, you will often find many different diodes on store shelves, or online. Some claim to be able to match the PAR spectrum more accurately than a white LED. When you shop for an LED light for your plants, you should be aware of the exact spectrum that it covers, and know whether it coincides with the PAR spectrum as closely as possible.

The fact about the PAR spectrum is that the better an LED light matches it, the more efficient the light will be. Less light will be wasted since there will be a higher ratio of usable light for your plants. This helps plants growers save on their power bill while simultaneously spurring better growth in your plants. There is also less heat loss, which means cooling your grow room is much easier with LED lights.

Thermal management of LED grow lights

LEDs don’t get as hot as other types of lights, and they are also far more efficient than other lights. This efficiency is because they don’t burn filament. The vast majority (95%) of an HID lamp’s energy is actually wasted as heat or radiation, therefore reducing its efficiency significantly. Since LEDs are generally cooler in temperature, they waste far less energy as heat.

When using LEDs or HIDs as grow lights, it’s important to take these heat differences into account. HIDs need to be situated several feet above the tops of your plants, for example, while LEDs can be kept really close to them (between one foot and 18 inches).

This does not mean, however, that LEDs have absolutely no heat issues associated with them. While they don’t feel warm because they aren’t emitting infrared radiation, the high powered LEDs are actually less efficient and, therefore, waste more heat than low powered ones.

If you have high-quality LEDs, they should have heat sinks that keep the heat under control. These heat sinks allow for the dissipation of unwanted heat. Any LED lights that are below 700 watts should use heat sinks to cool them. For high powered LED lights, heat sinks should include aluminum, copper, thermoplastics, or even graphite (for the most expensive option). A large surface area is required for the heat sinks to work efficiently, so don’t be surprised by odd fin shapes designed into some of the more expensive lights.

Because of the requirement for a large surface area, heat sinks will not be as practical of an option for the largest LED lights on the market. Therefore, some of these larger lights use passive heat sinks combined with fans to keep cool, although the best designs don’t need a fan at all because the sinks work well enough.

Whatever type of cooling system your LED light has, make sure it is high in quality. Low-quality cooling systems will cause your LED lights to deteriorate fast, so it’s better to pay the higher upfront costs to get your money’s worth in the long run.

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