Jumat, 12 September 2008

LED Green Power Technology

Why Indonesia doesnt care with semiconductor technology? while Nuclear technology still debatable and controversial let us think about green power technology based on it.

Why LED's?

LED's (Light emitting diodes) have begun to light the future with their capabilities of reducing power consumption by 80% over conventional lighting. Their "light" span is a minimum of 10 years for commercial usage, and a minimum of 25 years for residential applications. Besides eliminating the environmental hazards of mercury in fluorescents, LED's quietly illuminate with the closest look of natural daylight.

About LED Technology

Light emitting diodes (LEDs) were first developed in the1960s, but only in the past decade have LEDs had sufficient intensity for use in more than a handful of lighting applications (Stringfellow and Craford 1997), and specifiers are confronted with an increasing number of lighting products that incorporate LEDs for certain applications. Primarily, these applications have taken advantage of the characteristics of LEDs that have made them most suitable for indication, not illumination (Bierman 1998).

What determines the color of an LED?

The material used in the semiconducting element of an LED determines its color. The two main types of LEDs presently used for lighting systems are aluminum gallium indium phosphide (AlGaInP, sometimes rearranged as AlInGaP) alloys for red, orange and yellow LEDs; and indium gallium nitride (InGaN) alloys for green, blue and white LEDs. Slight changes in the composition of these alloys changes the color of the emitted light.

What are the electrical characteristics of LED's?

Individual LEDs are low voltage devices. Single indicator LEDs require 2 to 4 volts of direct current, with current in the range from 1 to 50 milliamperes. An illumination-grade LED containing a single semiconducting element requires the same voltage, but operating currents are much higher, typically several hundred milliamperes. A device containing multiple elements connected in series will require higher voltage corresponding to the larger number of individual elements in the device. LEDs require a specific electrical polarity. Applying voltage in reverse polarity can destroy them. Manufacturers provide specifications about the maximum reverse voltages acceptable for LED devices; 5 volts is a typical maximum rating.

Why is heat sinking important for LEDs?

It is common to refer to LEDs as "cool" sources in terms of temperature. This is because the spectral output of LEDs for lighting does not contain infrared radiation, unlike incandescent lamps that produce a large amount of infrared (of course, some LEDs for manufacturing purposes are designed to produce infrared energy, but these are not considered in this publication). LEDs are also often considered "cool" because they generate light through a mechanism other than thermal excitation of a substance, such as the tungsten filament in an incandescent lamp. Although LED lighting systems do not produce significant amounts of radiated heat, LEDs still generate heat within the junction, which must be dissipated by convection and conduction. Extracting heat from the device using heat sinks and by operating LEDs in lower ambient temperatures enables higher light output and longer life of the device.The need to ensure heat sinking with LED systems is also important to consider when these systems are installed in applications. There must be sufficient means to conduct the heat away from the system, or ventilation to cool heated surfaces by convection. Locating an LED lighting system in an insulated and relatively small space will likely result in rapidly increased junction temperature and suboptimal performance.

source : http://www.ledgreenpower.com/

Tidak ada komentar: