LEDs: A Challenge

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When I first came at my-tronic GmbH, I knew nothing about light emitting diodes. In my mind they were little green or red light bulbs inside my stereo showing that the power was on or off. But working at this company, even if as a simple media consultant, made me soon understand that, in order to do my job properly, I had to learn about the products the company is dealing with. My experience as a journalist helped: I knew that in order to get the best out of a subject one has to research a lot, to look for answers and to start “from the beginning”. I was, at first, not very thrilled to gain knowledge about the small light emitters. What can there be so spectacular about them? The answers were soon to prove how wrong I was when underestimating the potential of a little LED. These small devices have great proprieties that will revolutionize the light industry as we know it.

In fact, the revolution has begun with the release of the first LED, back in 1968, when 655 nm red (GaAsP) LEDs were introduced on the market by H-P and Monsanto. Since than till now LEDs were remarkably progressing and today they are displacing traditional bulbs and initiating new means of lighting. More and more these days fluorescent and incandescent bulbs and tubes are replaced by LED equipments and we also notice LEDs used in other applications.

Why are they so many times recommended over other traditional lights? Is it because LEDs manufacturers want to make money? Of course they do. But there are also other reasons to consider. Let’s have a brief look at some of the advantages:

LEDs are solid-state lighting semiconductors that produce light but little heat. For instance incandescent lights transform most of they energy they consume not in light, but in heat – only 5% of the electrical power is converted into the light we perceive. LEDs were optimised to release energy in the form of light. Since they need low voltage to operate, they are ideal for battery-powered appliances.

Safety: due to the fact that they produce light rather than heat, LEDs are perfect for applications where traditional lights are a potential safety hazard. For instance, traditional lights in natural Christmas trees may cause sometimes accidents: the heat dries the tree and so it can happen that it bursts to flames. LEDs do not get hot; there is no danger to let them run day and night. Sure, there is a question about correct use and connecting here.

LEDs are shock and vibration resistant. LED semiconductors are crystals consisting of combinations of two or three chemical elements such as aluminium gallium nitride (AlGaIn). When current passes through, they emit light. A traditional light bulb produces light when the current flows from one contact to the other through the wires and the tungsten filament. Break any of them (just shake the bulb a little) and you have no more light. Shake a LED, drop it, and step on it nothing happens.

Choice of viewing angles: LED light sources can be produced to emit light in the “right” viewing angles, each better fit for a specific application. For example, edge lighting will use 20° LEDs. Other available angles: 30°, 45°, 50°, 60°, 80°, 120°, and so on.

Choice of colours: Different LED chip technologies generate different colours, depending on the chip material used. For example, AlInGaP and InGaN, are used for creating high brightness LEDs in all colours from blue to red. LEDs light can be used either as is or with little modification. Fluorescent sources are different: their UV light must be converted to usable light by phosphors coated inside the tube. This is only one of the reasons why LEDs are a better choice than fluorescent tubes and bulbs.

One of the most remarkable features LEDs have is how they give users the possibility to control colours and light effects. They have a wide dimming range that will not affect the colour or their efficiency. All these features permit the creation of what we might call “smart” lights. A relatively “new release” is the RGB LED. RGB LEDs have three chips in one LED: red, green and blue. It’s like having three LEDs in one. So the “smart lights” grow even smarter: 16 million colours, more than human eye perceives, can be created using RGB LEDs. Amazing!

From the many important features LEDs possess is the “choice of wavelengths”. With LEDs is possible to eliminate wavelengths found in normal light and this way to reduce the amount of energy required to power other types of plant growth lamps. Each wavelength is crucial for certain aspects of plant growth: form is affected by blue light, photosynthesis by red light and seed sprouting by infrared (IR) light. LEDs provide flexibility: they offer the chance to combine wavelengths and to control intensity and light frequency.

LEDs influence growth in a positive way. In fact, the plants grow faster and taste the same as the ones raised with normal light. They do not mutate under the LEDs light, but they do benefit from it. Sea plants or other kinds of water plants can be grown with LEDs. The LED's light is not aggressive, so it can be also used in an aquarium or as night light for kids. Well, to make a long story short, NASA is growing plants in space, using LEDs. And if they can grow plants in space it means human life can be sustained anywhere in the Universe and if LEDs prove to be an economical mean, than why not?

LED therapy has been used successfully with diabetic skin ulcers, burns, and severe oral sores caused by cancer treatment. The redder the light, the longer the wavelength, and the longer the wavelength, the more deeply it can penetrate body tissues. LEDs practically boost energy to the cells and accelerate healing. See for reference an article about using LEDs at College's MACC (Midwest Athletes Against Childhood Cancer) Fund Research Centre at onepeoples.com.

The role light therapy has in our lives is not to be neglected: mental conditions were already treated with light therapy since the 1880s, when many hospitals around the world calmed their patients with blue light and stimulated others with red. It is already scientifically proved that coloured lights have different effects: red gives energy and strength, enhances sexuality, adds vitality and stimulates blood circulation. Orange invigorates the lymphatic system; yellow improves concentration and stimulates the circulatory system and skin; green heals and balances; blue reduces stress and violet calms the metabolic system and the nerves. Strobe light excites nerve endings (neural pathway report only changing stimuli). A non-colour strobe is recommended for children with learning difficulties and people with chronic pain. Colour strobe lights bring out deep-seated emotional problems. A licensed psychotherapist should always supervise this method. Bright light therapy was developed in the early 1980s to cure a seasonal affective disorder (SAD) also known as winter depression. Recently the method was applied to other disorders such as jet lag, food addiction, Alzheimer’s disease and attention deficit disorder in children.

And let’s not forget UV light therapy – used to cure psoriasis. One form of treatment is the Goeckerman regimen, combining UV-B light with coal tar applied to the affected skin. This medical treatment is also known as phototherapy and it may be also used for other skin conditions such as eczema, lymphoma, pruritis, atopic dermatitis, and so on. As UV-B, UV-A is also used to treat psoriasis. The method is called PUVA and it combines psoralen (a drug) and ultraviolet-A. UV LEDs can be successfully used for this purpose. One doesn’t call them “the next generation of lighting” for nothing.

All what was described above and even much more can be accomplished with LEDs. There are no limits, no restrictions. What we need is fantasy and courage to push the application area beyond what one can normally imagine. We are already talking about “smart” lights and light effects – not really accessible for the common user because this technology is still more expensive than the traditional one. But future will bring other possibilities, and what is today expensive will be, probably, considered old fashioned and cost less due to the technological progress. Already the standard 3 and 5 mm round LEDs are the cheapest one can get. Nowadays we talk about high efficiency LEDs that incorporate 40, 60 chips and are brighter than we could imagine one-two years ago. We talk about super-flux LEDs – the four-pin LEDs called sometimes Piranha or Spider LEDs – able to dissipate the heat better than the standard two-pin LEDs. We talk about the Luxeon Star and the examples continue with terms such as: ultra bright, super bright, high power… one general look will make us believe: that’s it; there is nothing else to be done. LEDs are at their peak. I doubt that. I have seen my-tronic GmbH working with LEDs for three years already. I have learned with my team and I know: tomorrow is another day. Tomorrow is the best day to start a new project, with new ideas and new challenges. This is what LEDs are: a challenge. And my-tronic GmbH welcomes chellanges.

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Mihaela Lica
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