What Are LED Lights? June 28 2017
When you hear the letters LED in association with lighting, what does that mean and what is LED light?
The letters are an acronym for Light Emitting Diode, a two-lead semiconductor light source which emits light when electricity passes through it. You can find a more in-depth explanation here (Wikipedia LED definition). What makes this type of light so miraculous and why are we hearing more and more about LEDs?
Well, they consume less energy, are very durable, they last a long time, produce very little heat and are tiny. Plus, with the combination of red, green and blue LEDs, an infinite number of colors are possible.
Let’s go back to the question, what are LED lights. We now know the LED consists of a diode of semiconducting material attached to electrical leads. This material is a crystalline solid, which contributes to LED technology having a classification as solid-state lighting. Solid-state lighting differs from other conventional lighting sources such as in incandescent, using heat to light a filament or as in fluorescent, using electric to excite gas discharge.
Scientists found crystals “light up” or illuminate when voltage flows through them; this is electroluminescence. Early light emitting diodes (LEDs) were made from a chip of the semiconductor substrate gallium arsenide found to emit a low intensity invisible infrared (IR) light. The first visible LED light was also low intensity and limited to red in color. This technology is still used today in electrical components such as television remote controls and as indicator lights.
Over time, new substrates were tested to create the lighting emitting diode. Blue was the next color to be developed from gallium nitride on a sapphire substrate. Shortly after that, white light LEDs were created from the addition of a phosphor coating. The coating absorbed some of the blue light and cast a yellow light through fluorescence. The remaining blue light combined with the fluorescent yellow light appears white to the naked eye. LEDs at this point were high in cost to produce and an inefficient, low-intensity light source.
More colors appeared from differing substrates; tuning the composition of the emitted light region, thereby changing the photon energy wavelength or color. Packages were created to encase the light emitting diodes, giving them more protection and more durability. These encasements can be made of epoxy, resin, plastic or ceramic. Even though LEDs do not radiate heat as compared to halogen or incandescent lighting, which releases 90% of its energy as heat, they do produce heat that needs to be drawn away. This heat can be dissipated by the addition of a metal heat sink on the back of the chip. Thermal control is equal to the lifetime of the LED, meaning operating at low temperatures and low electrical currents, the standard LED can last 25,000 to 100,000 hours. Higher temperature or applying a higher current will shorten the lifespan. Sudden loss of light hardly ever occurs; however, gradual loss of efficiency and light output is normal.
LEDs are still considered directional lighting, meaning light emits in a specific direction, making them more energy efficient and capable of producing more light. For example, a typical 60-watt incandescent bulb would produce around 14 lumens (lm) per watt (w) and last approximately (~) 1000 hours. The standard 60w fluorescent tube would produce ~63 lm/w and last 8000 hours. A 60w LED would produce ~94 lm/w and could last for 25-100 thousand hours. Special optic lenses have been developed for placement on the encasements allowing for higher power output and the high-brightness LED, a claimed 300 lm/w.
The advances in projection of emitted light and specific design placement have allowed the LED to illuminate a wider area than before. Use in lamps, ceiling troffers, hi-bay lighting and street lamps are common, to name a few. Now with the new mini LED component housed in a very small footprint, 1- x 0.8- x 0.2-millimeter, LEDs are showing up everywhere. You will find them lighting our Christmas trees, artificial flower arrangements, wall art, behind stained glass to create an artificially lit window, stone on countertops, or basically, anything you can think up LEDs can light up.
What started out in expensive laboratory and electronic test equipment has crossed the gambit of technology to achieve a beautiful, super bright, inexpensive, lighting resource. Explore for yourself, brighten up your life.
Want to see the process for manufacturing a LED crystal?
Below, Osram Opto Semiconductors has produced a great informational video covering their process.
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