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Home  News Lighting What is LED (Light Emitting Diode)?
What is LED (Light Emitting Diode)?
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"LED" means "light emitting diode". It does not require filament to create light. It's an electronic device that lights up when electricity passes through it.
It needs to be placed on a circuit board or other material that allow electricity to pass through it at a specific voltage and current. LEDs do not come ready to plug into a 12v or 120v power source.
LED Applications include:
- Light Bulbs
- Streetlights
- Video displays
- Architectural lighting
- Mood lighting
- Status indicators on all sorts of equipment
- Traffic lights and signals
- Exit signs
- Motorcycle and Bicycle lights
- Toys and recreational sporting goods, such as the Flashflight
- Railroad crossing signals
- Continuity indicators
- Flashlights
- Emergency vehicle lighting
- Elevator Push Button Lighting
- Thin, lightweight message displays
- Red or yellow LEDs are used in indicator and alphanumeric displays in environments where night vision must be retained: aircraft cockpits, submarine and ship bridges, astronomy observatories, and in the field, e.g. night time animal watching and military field use.
- Red, yellow, green, and blue LEDs can be used for model railroading applications
- Remote controls, such as for TVs and VCRs, often use infrared LEDs.
- In optical fiber and Free Space Optics communications.
- Movement sensors, for example in optical computer mice
- Automotive high-mounted brake lights and truck and bus brake lights and turn signals
- Backlighting for LCD televisions and displays.
- LED-based Christmas lights
- Scanners, computers for hard drive activity and power on.
- Lanterns
Advantages of using LEDs:
- LEDs produce more light per watt than do incandescent bulbs; this is useful in battery powered or energy-saving devices.
- LEDs can emit light of an intended color without the use of color filters that traditional lighting methods require. This is more efficient and can lower initial costs.
- The solid package of an LED can be designed to focus its light. Incandescent and fluorescent sources often require an external reflector to collect light and direct it in a usable manner.
- When used in applications where dimming is required, LEDs do not change their color tint as the current passing through them is lowered, unlike incandescent lamps, which turn yellow.
- LEDs are ideal for use in applications that are subject to frequent on-off cycling, unlike fluorescent lamps that burn out more quickly when cycled frequently, or HID lamps that require a long time before restarting.
- LEDs, being solid state components, are difficult to damage with external shock. Fluorescent and incandescent bulbs are easily broken if dropped on the ground.
- LEDs have an extremely long life span. One manufacturer has calculated the ETTF (Estimated Time To Failure) for their LEDs to be between 100,000 and 1,000,000 hours. Fluorescent tubes typically are rated at about 30,000 hours, and incandescent light bulbs at 1,000-2,000 hours.
- LEDs mostly fail by dimming over time, rather than the abrupt burn-out of incandescent bulbs.
- LEDs light up very quickly. A typical red indicator LED will achieve full brightness in microseconds; LEDs used in communications devices can have even faster response times.
- LEDs can be very small and are easily populated onto printed circuit boards.
- LEDs do not contain mercury, while compact fluorescent lamps do.
Basic LED Lighting Terms and Measurement:
Flux/Luminous Flux - Amount of light emitted in all directions by a light source; measurement unit: lm (lumen)
Intensity/Luminous Intensity - Amount of light emitted in a specific direction by a light source; measurement unit: cd (candela)
Lunimous Efficacy - Lumens out divided by electrical power in; measurement unit: lm/w or LPW (lumens per watt)
Luminance - The intensity of flux leaving a surface in a given direction; measurement unit: cd/m2 or "nit" (candela per sq. m)
Illuminance - The density of light on a surface; measurement unit: lux=lm/m2 or fc=lm/ft2 (foot candle)
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