From Wikipedia, the free encyclopedia
- " Flashlight" is also the NATO designation for the
Yakovlev Yak-25 Soviet military jet.
A flashlight or torch is a hand-held portable
spotlight. It is known as a flashlight mainly in the
United States and
Canada and as a torch or electric torch in
An 1899 Eveready flashlight, one of the earliest
Joshua Lionel Cowen invented a decorative lighting fixture
for potted plants which consisted of a metal tube housing a
light bulb and a dry cell battery. It failed commercially, and
so Cowen sold his company and patents to
Conrad Hubert that same year and turned his attention to
building and selling model trains. Hubert renamed Cowen's
company the American Electrical Novelty & Manufacturing Company
and, recognizing the true potential of Cowen's invention, hired
David Misell to produce a tubular flashlight for portable use.
They donated some models to the New York City police, who
responded favorably to it.
These early flashlights ran on zinc-carbon batteries, which were
poor at providing sustained currents; they would run down after
a while and needed to rest before being useable again.
Since these early flashlights also used energy-inefficient
carbon filament bulbs, this happened rather quickly, and
consequently they could only be used in brief flashes (hence
A typical flashlight consists of a small incandescent
lightbulb with associated
reflector, powered by
electric batteries, and with an
electric power switch. The components are mounted in a
housing that contains the necessary
electric circuit and provides ease of handling, a means of
access to the batteries for replacement, and a clear covering
over the lightbulb for its protection.
Although a relatively simple device, its invention did not
occur until the late 19th century because it depended upon the
earlier invention of the electric battery and
incandescent light bulb.
Electronically regulated, variable output LED
Recently, flashlights which use
light-emitting diodes (LEDs) instead of conventional
lightbulbs have become available. LEDs have existed for decades,
mainly as low-power indicator lights. In 1999,
Lumileds Corporation of San Jose, CA, introduced the Luxeon
LED, a high-power white-light emitter. For the first time this
made possible LED flashlights with power and running time better
than some incandescent lights. The first Luxeon LED flashlight
Arc LS in 2001.
LEDs can be significantly more efficient at lower power
levels, hence use less battery energy than normal lightbulbs.
Such flashlights have longer battery lifetimes, in some cases
hundreds of hours, although the LED efficiency advantage
diminishes at higher power levels. LEDs also survive sharp blows
that often break conventional lightbulbs.
LED flashlights are often electronically regulated to
maintain constant light output as the batteries fade. By
contrast a non-regulated flashlight becomes progressively
dimmer, sometimes spending much of the total running time below
50 percent brightness level.
A common misconception about LED-based flashlights is that
they generate no heat. While lower-power LED flashlights
generate little heat, more powerful LED lights do generate
significant amounts of heat – although not as
radiant energy – as the
junction inherently dissipates heat. For this reason
higher-powered LED flashlights usually have aluminum bodies and
can become quite warm during use. The use of aluminum is largely
due to its thermal properties, acting as a
heatsink for the high-power LED. Very few high-output LED
flashlights use a plastic body due to plastic being a thermal
insulator rather than a conductor.
Other flashlight designs
A headlamp is a flashlight worn on the head for hands-free
operation. Powerful headlamps mounted on
helmets have been used in
mining for decades, but general-purpose ones with fabric
straps are now also available.
Sometimes a light is mounted to a handgun or rifle.
Most flashlights are cylindrical in design, with the lamp
assembly attached to one end. However, early designs came in a
variety of shapes. Many resembled
lanterns of the day, consisting largely of a box with a
handle and the lamp attached to the front. Some others were made
to have a similar appearance to
candles. It is possible that future developments of battery
LED technology will bring interesting new designs. For
instance, one very small light consists of a few LEDs with a
switch, designed to be an endcap for a
High-quality flashlights go for as much as several hundreds
of dollars. Such flashlights are very advanced, using special
batteries, have adjustable brightness levels, dive-depth
waterproof ratings, interchangeable
optics, and are very bright.
Other power sources
Since batteries can be a burdensome cost in developed
countries, let alone in the third world, the development of
self-powered flashlights is a welcome advance. Some use solar
panels to recharge their batteries during the day.
- Main article:
Mechanically powered flashlight
Some flashlights have an
electrical generator built into them. Dynamo-powered
flashlights have a winding crank connected to a stepper
motor that feeds several
diode bridges with their outputs connected in parallel
field effect transistor that charges a capacitor that
connects to one or more LEDs. Others generate electricity using
electromagnetic induction. They use a strong permanent
magnet that can freely slide up and down a tube, passing
through a coil of wire as it does. Shaking the flashlight will
capacitor or a rechargeable
battery that supplies a
current to a
light source, typically a
light-emitting diode or, more rarely, an
incandescent light bulb.
Give Me a Light. Island Breeze. Retrieved on
Nonrechargeable Batteries. The Electrochemistry
Encyclopedia. Retrieved on
Wikimedia Commons has media related to:
Philips Lumileds Lighting Company
http://www.flashlightmuseum.com/ — flashlight Museum
http://www.ledmuseum.org/ — review website for lights
http://www.flashlightreviews.com/ — review website for
http://www.flashlightnews.org/ — flashlight industry