Light-emitting diodes (LEDs) has become more and more common these days for indoor lighting solutions due to their human and environmental safety, cost, and longevity. LEDs are widely used as indicator lights on electronic devices and increasingly in higher power applications such as flashlights and area lighting.
An LED is a solid-state semiconductor diode that emits light when an electrical current is applied in the forward direction of the device, as in the simple LED circuit. The effect is a form of electro-luminescence where incoherent and narrow-spectrum light is emitted.
An LED is usually a small area light source, often with optics added to the chip to shape its radiation pattern and assist in reflection. The color of the emitted light depends on the composition and condition of the semi-conducting material used, and can be infrared, visible, or ultraviolet.
There many benefits using LED as the lighting source. For example:
- LEDs produce more light per watt than 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 the 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.
- 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 can very easily be dimmed either by Pulse-width modulation or lowering the forward current.
- 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 mostly fail by dimming over time, rather than the abrupt burn-out of incandescent bulbs.
- LEDs can have a relatively long useful life. One report estimates 35,000 to 50,000 hours of useful life, though time to complete failure may be longer. Fluorescent tubes typically are rated at about 30,000 hours, and incandescent light bulbs at 1,000–2,000 hours.
- LEDs, being solid state components, are difficult to damage with external shock, unlike fluorescent and incandescent bulbs which are fragile.
- LEDs can be very small and are easily populated onto printed circuit boards.
- LEDs do not contain mercury, unlike fluorescent lamps.
- Due to the human eye's visual persistence LEDs can be pulse width or duty cycle modulated in order to save power or achieve an apparent higher brightness for a given power input. The eye will tend to perceive the peak current light level rather than the average current light level when the modulation rate is higher than approximately 1000 hertz and the duty cycle is greater than 15 to 20%
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