|This article needs additional citations for verification. (January 2012)|
A headlamp (known as a headtorch in the UK) is a light source affixed to the head for outdoor activities at night or in dark conditions such as caving, orienteering, hiking, skiing, backpacking, camping, mountaineering or mountain biking. Headlamps may also be used in adventure races, if racing is done during dark periods. Headlamps are often used by workers in underground mining.
Headlamps are usually powered by three or four AA or AAA batteries. Systems with heavy batteries (4xAA or more) are usually designed so that the light emitter is positioned near the front of the head, with the battery compartment at the rear of the head. It is sometimes possible to completely disconnect a headlamp's battery pack, for storage on a belt or in a pocket.
Lighter headlamp systems are strapped to the user's head by a single band; heavier ones utilize an additional band over the top of the user's head. Headlamps used incandescent bulbs before power LEDs became available. Incandescent bulbs have the advantage of allowing more tightly focused beams and the use of more power than LEDs, with the disadvantages of high power consumption, fragility, poor beam pattern and inability to operate at lower power levels. Incandescent headlamps also have rapidly declining light output once the batteries start to lose voltage.
White, 5mm LEDs were quickly adopted for use in headlamps due to their smaller size, lower power consumption and less fragility compared with incandescent bulbs.
Power LEDs rated 1 watt or more have displaced incandescent bulbs in many models of headlamps. To avoid damage to electronic parts, a heatsink is usually required for headlamps that use LEDs that consume more than 1W. To regulate power fed to the LEDs, DC-DC converters are often used in 1W+ lights, sometimes controlled by microprocessors. That allows the LED(s) to provide brightness that is not affected by a drop in battery voltage and allows selectable levels of output.
Miner's cap lamps
Thomas Edison developed electric cap lamps for miners starting in 1914; by 1915, certain cap lamps were approved by the United States Bureau of Mines for safe use in gassy coal mines. These included features such as spring-loaded contacts to automatically disconnect broken bulbs. These lamps consisted of a reflector and incandescent lamp and a separate belt-mounted wet-cell storage battery. The battery was sized to power the lamp for the entire working shift. After 12 hours a 1917-era miner's lamp produced less than one candlepower and about 2 to 5 total lumens. This pattern became popular for similar lamps. Head lamps approved for use in coal mines are designed not to allow an internal spark to ignite flammable gas surrounding the headlamp.
|Wikimedia Commons has media related to Headlamps (headgear).|
- Jurgen Brune, Jürgen F. Brune Extracting the Science: A Century of Mining Research SME, 2010 ISBN 0-87335-322-6, pages 35-40
- http://kycoal.homestead.com/MineLighting.html Mine Lighting retrieved 2012 Jan 09