LED stands for "light emitting diode." A diode is an electrical component with two terminals which conduct the electricity only in one direction. With an electrical current, the diode emits a bright light around the small bulb. Typically, diodes have been used in many technologies such as radios, televisions and computers as an electrical component for conduction
How They Work
A light-emitting diode (LED) is a semiconductor device that emits visible light when an electric current passes through it. The light is not particularly bright, but in most LEDs it is monochromatic, occurring at a single wavelength. The output from an LED can range from red (at a wavelength of approximately 700 nanometers) to blue-violet (about 400 nanometers). Some LEDs emit infrared (IR) energy (830 nanometers or longer); such a device is known as an infrared-emitting diode (IRED).
An LED or IRED consists of two elements of processed material called P-type semiconductors and N-type semiconductors. These two elements are placed in direct contact, forming a region called the P-N junction. In this respect, the LED or IRED resembles most other diode types, but there are important differences. The LED or IRED has a transparent package, allowing visible or IR energy to pass through. Also, the LED or IRED has a large PN-junction area whose shape is tailored to the application.
In the search for energy-efficient lighting, LEDs have proven to be the most efficient bulbs available. Energy Star--rated LEDs use at least 75 percent less energy than traditional incandescent bulbs and last 25 times longer. LEDs even outdo CFL (compact fluorescent lighting) bulbs in efficiency, primarily because they have twice the lifespan of CFLs. LEDs are more efficient than both incandescent and CFLs because they emit light in a targeted direction --- instead of scattering it in all directions --- and they don't require or emit great amounts of heat. Incandescent and CFLs release most of their energy as heat --- 90 percent and 80 percent, respectively.
Benefits of LEDs and IREDs, compared with incandescent and fluorescent illuminating devices, include:
· Low power requirement: Most types can be operated with battery power supplies.
· High efficiency: Most of the power supplied to an LED or IRED is converted into radiation in the desired form, with minimal heat production.
· Long life: When properly installed, an LED or IRED can function for decades.
Typical applications include:
· Indicator lights: These can be two-state (i.e., on/off), bar-graph, or alphabetic-numeric readouts.
· LCD panel backlighting: Specialized white LEDs are used in flat-panel computer displays.
· Fiber optic data transmission: Ease of modulation allows wide communications bandwidth with minimal noise, resulting in high speed and accuracy.
· Remote control: Most home-entertainment "remotes" use IREDs to transmit data to the main unit.
· Optoisolator: Stages in an electronic system can be connected together without unwanted interaction.
The biggest problem for consumers when purchasing LEDs for residential lighting is the upfront cost. Depending upon the size and brand of the bulb, LEDs can cost two to six times the price of CFLs. When replacing bulbs for multiple lighting fixtures, the idea of spending hundreds of Rupees on bulbs deters many potential customers. However, LED production is not only improving but increasing, which will mean greater affordability for consumers in the near future.