Types of Light Bulbs Used in Spotlights and Flashlights
There are three types of light sources in common use today in flashlights and spotlights:
- Incandescent bulbs, which operate by providing an electric charge to a tungsten filament inside of a bulb. Krypton, halogen, and xenon bulbs are types of incandescent bulbs that use a filament; HID bulbs use a spark instead of a filament.
- Fluorescent lights, which operate by providing an electric charge to a gas in a glass container. They come in a variety of shapes and are not limited to a "bulb" shape.
- Light-emitting diodes (LEDs), which operate by providing an electric charge to a solid-state diode.
The primary advantage of incandescent bulbs is that they are inexpensive because they require no external regulatory equipment and are inexpensive to manufacture. They have been in use for over 100 years.
However, incandescent bulbs have some serious drawbacks for flashlights and battery-powered spotlights. They can break if the flashlight or spotlight is dropped or jarred. Even if not jarred, they aren't designed to last more than 1,000 hours because the filament burns out. Some inexpensive bulbs are designed to last as little as 50 hours. Most of the energy produced is lost as heat rather than light; they are not very energy-efficient. The gas used in traditional incandescent bulbs is argon, nitrogen, or a combination. Small bulbs often have a vacuum instead of a gas.
Incandescent bulbs that are filled with krypton gas conduct less heat than the argon-nitrogen bulbs and are therefore more efficient. Krypton lights last longer and put out more light than argon/nitrogen bulbs.
Xenon gas conducts even less heat than krypton gas and therefore xenon lights are more efficient than krypton lights. Xenon lights last longer than argon-nitrogen lights and are the brightest of the three incandescent bulbs.
A halogen lamp also uses a tungsten filament but uses a much smaller bulb that is made of quartz instead of glass. It uses halogen gas instead of argon, nitrogen, krypton, or xenon. The chemical interaction between the tungsten vapor and the halogen gas keeps recycling the tungsten into the filament, strengthening it. A halogen lamp, therefore, lasts twice as long as a normal incandescent bulb. However, the halogen lamp gets extremely hot, up to 4,500 degrees F. Because of the extreme heat, the halogen lamp must be located away from human contact.
Some flashlights or spotlights are called "halogen" because they use a quartz bulb and a tiny amount of halogen gas; in these bulbs the gas used is primarily xenon or krypton. The amount of halogen gas used may be as little as one percent.
High Intensity Discharge (HID)
HID lights use electrical sparks instead of a filament surrounded by gases to create light. An HID flashlight can generate 3,500 or more lumens and can cost over $500.00. The brightest LED light "bulb," in comparison, generates less than 1,000 lumens. There is a danger of getting burned by a HID flashlight or spotlight because the lens gets very hot.
Fluorescent Light Bulbs
Fluorescent lamps work by exciting a gas with an electrical charge; since most of the energy is used to generate light instead of heat, a fluorescent bulb provides light several times more efficiently than an incandescent bulb. However, since a fluorescent bulb is made of glass, it is more fragile than an LED light. In addition, fluorescent bulbs use mercury, an environmental hazard.
Fluorescent lamps require a ballast to control the charge and so they are more expensive than incandescent bulbs. Compared to LED lights, they provide more diffuse light; this may be better for general lighting, such as in a tent, compared to hiking where more focused light might be more desirable.
LED Light Bulbs
LED (light emitting diode) is a semiconductor 'chip' that converts electrical energy directly into light. It has no gas or liquid components like the above mentioned bulb types.
Flashlights makers are rapidly converting over from Krypton, Xenon, and Incandescent bulbs to LEDs. There are several reasons:
- LEDs have no delicatemechanical parts, glass bulbs, filaments and are resistant to vibrationand shock.
- They put out no infrared(heat) radiation and, therefore, are much more efficient at producinglight compared to incandescent bulbs; a battery in a flashlight with anLED bulb will last 10 times or longer than an incandescent bulb.
- LEDs can last decadescompared to 1,000 hours for an incandescent bulb.
- LEDs do not use mercuryor lead and so are more environmentally friendly than fluorescent bulbs
The primary limitations of LED bulbs used to be cost, color, and brightness. Costs have come down dramatically for flashlights and spotlights so they are no longer expensive enough to change the overall cost of a flashlight or spotlight.
White LED lights were not available from a single diode until 1993 when Nichia invented a way to coat a chip with phosphor that then generates white light. LEDs are now available in "natural" light, matching sunlight on the color spectrum.
Another limitation of LED flashlights in the past was that they did not put out a very strong light. Now, for under $50, LED flashlights can be found that put out 200 lumens of focused light, similar to the output of a 40 to 60 watt incandescent bulb--but focused in one direction. An LED flashlight putting out 200 lumens is very bright and should not be shined in someone's face. Earlier versions of LED flashlights had very focused beams that did not provide much light away from the beams. For most uses, this was undesirable. Many of the newer LED flashlights have designs that place a "halo" of light around the focused light, a better design for most uses.
LED flashlights come in a variety of brightness levels and levels of energy efficiency. Small flashlights can yield as little as 10 lumens of light while the most powerful ones can provide 600 lumens or more. Some LEDs, especially those requiring 3 watts or more of power, can discharge the batteries in less than two hours. Some of the smaller LED's can allow the batteries to last over 100 hours. An LED flashlight providing good light, over 100 lumens, should be able to last six or more hours per charge, assuming three rechargeable AAA Ni-MH batteries or equivalent.