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
restarting.
> 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
boards.
> 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)
