Fenix Flashlights | How Does a Flashlight/Torch Work?

A Basic Guide on Flashlight Operation



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This week we will be discussing how modern flashlights work, including light source, power source, and functions. Most modern flashlights use LEDs or Light-emitting Diodes as a light source. There are still a few companies that use incandescent light bulbs as the light source, even though they have a shorter life and have to replace more often. Most flashlights have the light source either LED or Bulb mounted around a reflector. This part of the flashlight is usually covered by a lens or transparent cover. This area is then connected to the power source. Most common power sources for modern flashlights are rechargeable and non-rechargeable batteries. The power source then makes contact with a switch usually located on the rear part of the flashlight. The switch will allow the power source to make a full circuit to the light source, thus giving power to the flashlight. 90% of the world's flashlights operate this same way.

Light Sources

Incandescent Light Source - As we had mentioned before there are still a few companies that use incandescent light bulbs as the their light source. Incandescent Light Bulbs were the first light source of flashlights. The lifetime of an incandescent lights bulb is very short, sometimes only lasting a few hours. Most flashlight companies that use incandescent light bulbs make it easy for the user to replace the bulb. Lumen output on incandescent light bulbs varies from a low to mid range. Some have been able to reach capacities near 500 Lumens. Some flashlights that use incandescent light bulbs can use rechargeable batteries also. The most common power source for these flashlights is D Cell batteries and AAs and AAA’s on the smaller flashlights.

LED Light Source- Next we have Light-emitting diodes or LEDs for short. This light source for flashlights has become very popular over that last two decades. In comparison to incandescent light bulbs, LEDs have much greater Lumen outputs and a much longer life and are less fragile. Another advantage of LEDs is that they produce a longer battery life, and have a wide range of color temperatures. LEDs can also be powered by rechargeable and non-rechargeable batteries. Most modern LED flashlights will require a voltage anywhere between 3.2 to 3.9 to power on. Many LED flashlights have been equipped to be rechargeable battery. One example would be the Fenix PD36R, which is a rechargeable flashlight that has a max output of 1600 Lumens.

Power Source

You will find that most modern flashlights will use disposable batteries as their power source. Other flashlights have the option of using either rechargeable or non-rechargeable power sources. A prime example of this would be the Fenix PD35 TAC, which uses two nonrechargeable CR123A or a rechargeable 18650 battery. One main thing to consider is how often the light is going to be used. If it is used frequently then a rechargeable option may be the best option. You also want to consider that regular alkaline batteries can be dangerous, and should not be left inside a battery for long periods of time. Many advancements have been made to provide a reliable power source to modern flashlights, some companies have even designed solar powered flashlights. The most common batteries that you will find for flashlights will be AAs, AAAs D-Cell, CR123, 18650s, 14500s 16340s and 26650s. Some of the mentioned batteries are available in a non-rechargeable or rechargeable option.

Flashlight Reflectors

A reflector is a very important part of a flashlight, which contributes to its functionality. Depending on the reflector type this will determine if the flashlight is a floodlight or spotlight. There are also flashlights that have focusing reflectors, which allows a flashlight to transition between spotlight and floodlight.

The most common reflector types are “orange peel” reflectors, these allow for a very uniform light beam but create a floodlight effect. Smooth and polished reflectors are used to create a spotlight effect for the flashlight. Depending on the reflector type of each flashlight you make have a different throw distance for each. Throw represents the visible reach of the light source, a smooth and polished reflector that creates a spotlight beam will have a farther throw or visible distance compared to an orange peel reflector.  Another aspect of flashlight reflectors is the angle at which they are positioned, this also determines beam distance or throw.

Flashlight Switches

This is also a very crucial part of any flashlight. The switch not only allows you to make a complete circuit of the power source to the light source but in some cases, it will also regulate the amount of Lumens the flashlight will output. Depending on the brand of flashlight some will have a rear switch or a side switch or both. Some examples are the Fenix E30R which has only a side switch operation. Another example is the Fenix TK16 V2 which has only a rear switch operation.

The switch as mentioned before will allow you to turn the flashlight on and off. It can also allow you to increase or decrease a number of lumens. Some modern flashlights are digitally regulated, this means that they will automatically step down from their current lumen output they reach a certain temperature or when a certain amount of power has been lost. Many flashlight companies do this a protective and preventative measure.

Body Structure

You will find that most flashlights today are made of an aluminum, steel, or plastic casing. The most common being aluminum specifically in LED flashlights since they allow for even heat dissipation and weight considerably less than steel or copper. There are usually two or three parts to a body casing for a flashlight. The headpiece will hold the LED or bulb, circuit board, and reflector. This part can be sometimes integrated with the body of the flashlight. The body of a flashlight will hold the batteries securely in place, and depending on the model may also have a switch. Last is the tail cap, this part screws into the body and holds the battery inside. Some tail caps may have a spring or switch in the rear.

All these components work together to make a flashlight work. Hopefully, you've gained some important information from our blog today. Thanks for joining us!