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 led 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 [15]. 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, as compact fluorescent lamps do.
Disadvantages of using LEDs
LEDs are currently more expensive, price per lumen, on an initial capital cost basis, than more conventional lighting technologies. The additional expense partially stems from the relatively low lumen output and the drive circuitry and power supplies needed. However, when considering the total cost of ownership (including energy and maintenance costs), LEDs far surpass incandescent or halogen sources and begin to threaten compact fluorescent lamps.
LED performance largely depends on the ambient temperature of the operating environment. "Driving" a LED "hard" in high ambient temperatures may result in overheating of the LED package, eventually leading to device failure. Adequate heat-sinking is required to maintain long life. This is especially important when considering automotive, medical, and military applications where the device must operate over a large range of temperatures, and are required to have a low failure rate.
LEDs must be supplied with the correct current. This can involve shunt resistors or regulated power supplies.
LEDs typically cast light in one direction at a narrow angle compared to an incandescent or fluorescent lamp of the same lumen level.
The spectrum of some white LEDs differs significantly from a black-body radiator, such as the sun or an incandescent light. The spike at 460 nm and dip at 500 nm can cause the color of objects to be perceived differently under LED illumination than other light sources.
LEDs cannot be used in applications that need a sharply directive and collimated beam of light. LEDs are not capable of providing directivity below a few degrees. In such cases LASERs (or LED lasers) may be a better option.
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