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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 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.
> 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

> LEDs, being solid state components, are difficult to damage with

external shock. Fluorescent and incandescent bulbs are easily broken if

subjected to external shock.
> LEDs can have a relatively long useful life. Reports estimates 60,000

hours of useful life, though time to complete failure longer.2 Fluorescent

tubes typically are rated at about 30,000 hours, HID and MH are rated

anywhere between 10,000 and 24,000 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 or HID bulbs.3 This provides extra safety for any area

illuminated by LEDs. Even if the LEDs dim over time, they never fail

completely like HID sources before needing to be replaced. LEDs need to be

replaced only after they reach 30% lumen depreciation (17-20 years for

quality LEDs).
> LEDs light up very quickly. A typical red indicator LED will achieve

full brightness in microseconds; Philips Lumileds technical datasheet DS23

for the Luxeon Star states “less than 100ns.” LEDs used in communications

devices can have even faster response times.
> LEDs can be very small and are easily populated onto printed circuit

> LEDs do not contain mercury, unlike compact fluorescent lamps.
Disadvantages of using LEDs

> On an initial capital cost basis, LEDs are currently more expensive,

measured in price per lumen, than more conventional lighting technologies.

The additional expense partially stems from the relatively low lumen

output, combined with the cost of the drive circuitry and power supplies

needed. However, when considering the total cost of ownership (including

energy and maintenance costs), LEDs far surpass other sources. In December

2007, scientists at Glasgow University claimed to have found a way to make

Light Emitting Diodes brighter and use less power than energy efficient

light bulbs currently on the market by imprinting holes into billions of

LEDs in a new and cost effective method using a process known as

nanoimprint lithography.4 Around the same time, in Montreal Canada, Lumec

inc. developed an LED light engine that consumes 20% to 30% less energy

than HPS (high pressure sodium) and 40% to 50% less than MH (metal halide)

while delivering comparable photometric performance, if not better, than

HID lights.
> LED performance largely depends on the ambient temperature of the

operating environment. Driving the 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, outdoor, medical, and

military applications where the device must operate over a large range of

temperatures, and is required to have a low failure rate. The most heat

resistant LEDs available commercially, such as those used by Lumec inc. In

their light engine, the LifeLEDTMcan function at optimal efficiency from

-40°C to +50°C(-40°F to 122°F)