Modern LED flashlight

April 22, 2023

A flashlight is a portable, handheld electric lamp. Previously, the light source was usually a miniature incandescent bulb, but these have been replaced by LED bulbs since the mid-2000s.

LED lamps

LEDs have existed for decades, primarily as low-power indicators. In 1999, Lumileds Corporation of San Jose, California introduced the Luxeon LED, a high-power white light bulb. This made it possible for LED flashlights to offer improved power and runtime over incandescent bulbs. The first Luxeon LED flashlight was the Arc LS, designed in 2001. Multiple units can be grouped together to provide additional lighting. Higher-power LEDs, each drawing more than 100 milliamps, simplify the optical design problem of producing a powerful and tightly controlled beam.

Flashlight composition

A typical flashlight consists of a light source mounted in a reflector, a transparent cover (sometimes combined with a lens) to protect the light source and reflector, a battery, and a switch, all enclosed together in a box.

The invention of the dry cell and miniature incandescent electric lamps made possible the first battery-powered flashlights around 1899. Early flashlights operated on zinc-carbon batteries, which could not provide a constant electric current and required periodic rest periods to continue functioning. Because these early flashlights also used energy-inefficient carbon filament lamps, the rest periods were short. Consequently, they could only be used for short periods of time.

Incandescent electric lamps

Incandescent flashlights use incandescent bulbs, which consist of a glass bulb and a tungsten filament. The bulbs are either vacuum-filled or filled with argon, krypton, or xenon. Some high-power incandescent flashlights use halogen bulbs, where the bulb contains a halogen gas such as iodine or bromine to improve the life and efficiency of the bulb.

Today, flashlights mostly use light-emitting diodes and are powered by disposable or rechargeable batteries. Some have solar panels to charge the battery. Flashlights are used as a light source during power outages or when a portable light source is needed.

In addition to general-purpose flashlights, many forms of handheld flashlights are adapted for specialized uses. Head- or helmet-mounted flashlights, designed for miners and campers, leave the hands free. Some flashlights can be used underwater or in flammable atmospheres.

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