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Archive for the ‘About LED Lights’ Category

Imagine a shirt that changes color with your mood. A backpack that glows softly to make sure oncoming traffic can see you. Front stoop rugs that light up with the message ‘Welcome! Please Wipe Your Feet!’ The flexibility of LED lights is sparking designers and inventors to new heights of imagination in the areas of home and architectural lighting, as well as in the novelty market.

Novelty items lit by LED lights have been around for some years now. The small size of LEDs coupled with their low power usage and cool operating temperatures have made them popular for such things as t-shirts and belt buckles with programmable messages and funky shaped mood lights for your home. Until recently, though, the cost of LED lights made everyday applications using LED lighting technology impractical, and the low intensity of the illumination made LED lights unsuitable for whole room illumination.

Welcome to the new world of mood lighting using LED lights. LED, light emitting diodes, have been around since the early 1970s, when they made a splash lighting up the faces of digital clocks and calculators. By the Eighties, they’d made their way into various automotive uses, but LED lights were still too expensive – and didn’t emit enough light – for general illumination. Until recently, the biggest uses for LED lights have been for traffic signaling and automobile brake lights. Recent advances in color technology have changed all that. Over the past few years, several companies – notably Sanyo of Korea – have developed LEDs using RGB mixing that can create 16 million colors – and be mixed to create bright, pure white light.

A typical incandescent halogen bulb uses about 2.4 kilowatt hours per day to run. LED lights with the same lumens output use about .5 kilowatt hours per day. That’s nearly an 80% savings in cost to run each light in the city. As an example, the City of Sacrameno, California converted its first traffic light from incandescent light to LED lights in 1994. The first month, the city’s electric bill for that light dropped from $148 to $21.40. It’s taken nearly ten years for Sacramento to make the change county-wide, and as of 2004, 1,000 of the city’s 1,300 traffic signals use LED lights – for a savings in energy costs of $350,000 annually. Even for smaller cities, the savings in cash could run into the tens of thousands of dollars. That’s millions of dollars to spend on things like teachers and police presence.

LED lights also last longer than incandescent halogen lights – an average of 20-100 times longer. Most traffic light bulbs need replacing a few times a year. An LED light will last for years of continuous use. The savings in manpower alone adds up to thousands of dollars a year. In Kentucky, for instance, the state anticipates a savings of $1.5 million in maintenance costs – each time a crew goes out to change the bulb in a traffic light, the state pays a three man crew plus a traffic safety officer. By reducing those changes from once or twice per year per light to once per ten years per light, the savings are enormous.

The savings in energy goes even further than money, though. The use of LED lights in traffic signals opens the possibility of using solar panels and other passive forms of energy to power the lights. There’s an enormous savings in the cost to the Earth of the fuels used in the production of electricity to consider as well. The overall savings of converting from incandescent lighting to LED lights has prompted the United States government to create incentives for municipalities that decide to make the transfer. There are rebates available from many major power companies, and subsidies and low cost loans available to towns and cities that are switching from incandescent traffic signals to traffic signals that use LED lights.

Currently, there are two states – Delaware and Kentucky – who have taken full advantage of the savings available by converting all traffic signals on state highways to LED lights. Kentucky projects savings of over $3 million annually, just in energy costs. In other states, the change is taking place from city to city, often starting with lights at pedestrian crosswalks, and is supported with rebates from energy providers like Pacific Electric in California.

A semiconductor is a crystalline material that conducts electricity under certain conditions. LED lights are powered by a type of semiconductor called a light emitting diode. To create an LED crystal, manufacturers add an impurity to the mix as the crystals (usually aluminum-gallium-arsenide) grow. The type of impurity added creates either a p-type material, with extra positive electrons, or an n-type material with extra negatively charged electrons.

A diode is made by bonding an n-type material to a p-type material and putting an electrode at each end. Where the two materials meet, electrons from the negative end fill ‘holes’ in the positively charged end, creating a ‘depletion zone’ which doesn’t conduct electricity. When electricity is applied, electrons flow across the depletion zone and the resulting interaction between negative and positive electrons creates light.

Advantages of LED Lights Over Traditional Light Sources
The advantages of LED lights over incandescent and fluorescent light sources include better energy efficiency, lower overall cost of light and unimagined flexibility. More specifically:

LED lights last longer than traditional lights. Because there’s no tungsten filament to burn out or gasses to get depleted, LED lights last 20-100 times longer than traditional bulbs or tubes. Imagine only having to change your light bulbs once every 10 years. That’s the sort of function that LED lights promise.

LED lights use less energy than traditional lights. Because LED lights require fewer watts per lumens, the cost in energy savings is substantial. A traffic light using an incandescent light, for example, costs $72 per year to run. One using LED lights costs only $45. Multiply that by the hundreds and thousands of traffic lights in a city and you have an idea of the magnitude of energy savings possible. Developers estimate that replacing JUST the lighted EXIT signs in public buildings with LED lights would result in a savings of $3.5 BILLION per year.

LED lights can be directly controlled via a digital interface, making them ideal for using with computer generated displays and applications. This makes LED lights ideal for signaling and messaging applications. LED lights are already being used for scoreboards, traffic signals and other message mediums, and are making a big splash in the novelty markets. Wearable LED lights are one of the hottest new fashion trends on the dance club circuit. Tshirts and belt buckles with LED lights can display preprogrammed messages or flash in pattern with the music or movement of the person wearing them.

LED lights are sturdier than other lighting sources. Their construction makes them perfect for use in mobile applications and vehicles, where they withstand the bumps and jolts of traveling far better than traditional incandescent bulbs. Automobile manufacturers have been using LED lights in brake lights since the early 1980s, but the new applications include headlights that change focus and direction as the steering wheel is turned.
As manufacturing processes are developed that allow the large-scale production of LED lights and their newest ‘little sister’ OLEDs (organic light emitting diodes), the cost of using them for everyday home purposes will drop into the affordable range. Within 20 years, we may be telling our children, “When I was your age, we used to have to change the light bulb every six months!”

Kentucky recently replaced 77,000 incandescent traffic lights with LED traffic signals. The state expects to save over $3 million in energy costs, but that’s just the start of the advantages of the new LED lights. The LED lights in the new traffic signals will only need replacing every 8-10 years rather than every 11 months. That means huge potential savings in replacement costs – as well as reducing the number of times that hazard work crews have to run out to replace failed lights.

At the Rensselaer Polytechnic Institute, the Otis Elevator company installed newly developed white solid state LED lights in an elevator. The new lights use 45% less energy than the old incandescent lighting – but there’s more. Their compact size means that elevator cabins need several inches less headroom – lower weight cabins mean less stress on the elevator machinery and further cost savings over time. One set of LED lights will last about 4 years. In that time, traditional incandescent lights would be replaced 10 to 20 times.

Concert-goers in the UK were treated to one of the latest innovations in LED lights – Soft-LED. The touring dance band Basement Jaxx backed their stage show with an enormous ‘curtain’ consisting of thousands of LED lights that could be programmed to display graphics, light shows, text messages and graphic montages to complement the music. Soft-LED is a flexible ‘drape’ which may someday – in the not too distant future – be used in home interior decorating and window coverings.

Children undergoing treatment at Boston Children’s Hospital can have their own panel light show. Color Kinetics, a leading manufacturer of LED lights for specialized industries like architecture and theater lighting, created ceiling panels for rooms at BCH which change color according to a preprogrammed pattern or randomly. Children staying at the hospital can adjust the ceiling tiles according to their moods or creativity. One advantage, doctors say, is in giving children some control over their environments which leads to a decrease in depression among children undergoing cancer therapy and other treatments.

The common factor in all the above examples is the use of a technology that was, as late as last year, seen as decades away from popular adoption. In 2003, one leading pioneer in the field of LED lights, Arpad Bergh stated in an article for The World and I Online, “We erred in presuming only incremental advances and excluding the possibility of the kind of major breakthroughs in technology that have so often created new paradigms.” He went on to add that the coming decade would see the replacement of tungsten based and fluorescent lighting with LED lights and solid state lighting, as well as radically different approaches to lighting that aren’t possible with today’s technology.