Flashlight Basics: Difference between revisions

Traditional flashlights have an incandescent bulb and are powered by a couple of alkaline batteries. They are On or Off. But in the past ten years or so [[LED]] flashlights have made enormous leaps in performance offering more light, longer bulb life, and greater efficiency, meaning you can use smaller batteries or that your batteries will last longer. There are also choices other than LED, including xenon bulbs.

Most flashlights include a reflector around the light source to gather the light and focus it out the front. Reflectors have a parabolic shape which can take light rays emitted from a light source in the parabola's focal point and send the reflected rays all in the same direction (rays that go out the front without htting the reflector will provide some spill). A bigger, deeper reflector is able to focus the light into a smaller hotspot and offer more throw and less spill. Smaller lights are easier to carry in a pocket but will generally have more floody light. [[Mag Instrument]]'s Maglites have a reflector that moves with respect to the light source allowing a variable focus that can yield a wider flood or a tighter spot of light.

Usually there is a flat glass lens over the reflector. Better lights have ultra clear glass with anti-reflective coatings that allow more of the light to pass through the lens rather than bounce back into the light. But some lights have a curvilinear lens that concentrates the light similar to a reflector. And still other lights let you move this lens and go from flood to throw, similar to Maglites.

Current from the batteries is controlled by the power switch. While traditional lights have this on the side, smaller lights usually put the switch on the tail of the light, so that it can be activated by your thumb. A tail clicky, when turned to On, completes a connection between the bottom, negative end of the batteries and the body of the flashlight where the electricity travels up to the head of the flashlight causing a difference in potential that is used to power the light source. Clickies can be "forward" (allowing momentary On when the switch is halfway pressed) or "reverse" (the light does not turn on until the switch clicks into place). Some lights feature electronic switches which work a little differently. There are also twisty switches where you twist the tail or head of the light to complete the electrical connection.

In the head of the light there might be a [[driver]] which regulates the voltage from the batteries to some value optimal for the light source. For instance many LED's need a voltage of about 3.6 volts, so if you only have one AA battery (1.2 to 1.5 volts), the driver will need to boost the voltage to something the LED can use. The driver also can control different brightness levels to the light and special modes for SOS or strobe functions.