Lighting Research Center Lighting Research Center
    Volume 10 Issue 1
May 2010     
LED Lighting Products for Consumers
A-lamp - The incandescent lamp most commonly used in North American households. The "A" designation refers to the lamp's bulbous shape. line voltage - The voltage supplied by the electric power infrastructure, typically 110-120 Vac at 60 Hz for homes in North America. color rendering index (CRI) - A rating index commonly used to represent how well a light source renders the colors of objects that it illuminates. For a CRI value of 100, the maximum value, the colors of objects can be expected to be seen as they would appear under an incandescent or daylight spectrum of the same correlated color temperature (CCT). Sources with CRI values less than 50 are generally regarded as rendering colors poorly, that is, colors may appear unnatural. lamp rated life - The number of operating hours at which half of a large group of product samples are expected to fail. The rated life is a median value of life expectancy; individual lamp life may vary considerably from the published rated life and operating conditions (e.g., temperature, hours per start) may affect actual life because rated life is based on standard test conditions. In addition, the way a product fails can vary by technology. For example, incandescent lamps abruptly stop producing any light while LEDs are considered to have failed when their light output drops below a certain fraction of the initial level. luminaire - A complete lighting unit consisting of a lamp or lamps and the parts designed to distribute the light, to position and protect the lamp(s), and to connect the lamp(s) to the power supply. (Also referred to as fixture.) correlated color temperature (CCT) - A specification for white light sources used to describe the dominant color tone along the dimension from warm (yellows and reds) to cool (blue). Lamps with a CCT rating below 3200 K are usually considered warm sources, whereas those with a CCT above 4000 K usually considered cool in appearance. Temperatures in between are considered neutral in appearance. Technically, CCT extends the practice of using temperature, in kelvins (K), for specifying the spectrum of light sources other than blackbody radiators. Incandescent lamps and daylight closely approximate the spectra of black body radiators at different temperatures and can be designated by the corresponding temperature of a blackbody radiator. The spectra of fluorescent and LED sources, however, differ substantially from black body radiators yet they can have a color appearance similar to a blackbody radiator of a particular temperature as given by CCT. power - The power used by a device to produce useful work (also called input power or active power). In lighting, it is the system input power for a lamp and ballast or driver combination. Power is typically reported in the SI units of watts. luminous flux - Luminous radiant power, measured in lumens. The overall light output of a lamp or luminaire. light-emitting diode (LED) - A solid-state electronic device formed by a junction of P- and N-type semiconductor material that emits light when electric current passes through it. LED commonly refers to either the semiconductor by itself, i.e. the chip, or the entire lamp package including the chip, electrical leads, optics and encasement. color rendering index (CRI) - A rating index commonly used to represent how well a light source renders the colors of objects that it illuminates. For a CRI value of 100, the maximum value, the colors of objects can be expected to be seen as they would appear under an incandescent or daylight spectrum of the same correlated color temperature (CCT). Sources with CRI values less than 50 are generally regarded as rendering colors poorly, that is, colors may appear unnatural. There are two ways to produce white light using LEDs. The first is to use a combination of red, green, and blue LEDs which produce white light in an additive process. The second method, developed in the late 1990s, covers a blue or ultraviolet LED with a phosphor which reemits the light in a broad, white-light spectrum. These phosphor-based white LEDs are used in most consumer products available today.

Abstract

Lighting Answers: Availability of LED Lighting Products for Consumers provides information about the general illumination LED products that were available in consumer-oriented retail stores in the Albany, New York area in the spring and fall of 2009. The types of products available for sale were power failure lights, task lights, replacement lamps (commonly referred to as light bulbs), night-lights, and under-cabinet luminaires.

Introduction

An interesting transition has occurred recently in the world of lighting: light-emitting diode (LED) general illumination products are starting to appear on retail shelves. The first luminous LEDs were built in 1962 (MIT 2009), but it was not until around 2000 that an LED that produced white light was developed (Shimizu 2000). Since that time, white-light LEDs have become more widely used. These products have the potential to reduce emission of carbon dioxide and other pollutants from power plants because, when designed properly, they can generate light more efficaciously than many other sources. Also, they are free of mercury, a toxic metal, and promise a longer life than traditional incandescent or compact fluorescent lighting products (U.S. ENERGY STAR 2009).

 

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