Converting a Mini Maglite to an LED Flashlight

bulbsI was recently given a broken mini maglite (the one that runs on two AA batteries and twists to turn on and off). It was in good shape except for the fact that it was missing the reflector and lens. Due to the peculiar was the switch works on this flashlight, without those two parts the flashlight was pretty much useless.

I decided to convert the flashlight to use an LED instead of an incandescent bulb. Initially my plan was to do the best job I could regardless of (reasonable) costs, but I found the total cost for my conversion was less than $5. The end result is a surprisingly good LED flashlight.

Required materials:

Part Cost
Mini-Maglite flashlight
10mm Ultra-High Brightness White LED (Radioshack part #276-005) $2.79
Three Nylon Washers (0.680″ OD, 0.375″ ID, 0.125″ Thickness) $0.36 each
One steel washer (.875″ OD, 0.375″ ID) $0.33 each
Total $4.20

3Assembly is very simple. Snip the leads of the LED to approximately the same length as the maglite bulb’s leads (a bit less than half an inch). Make sure the maglite has good batteries, and unscrew the flashlight head. Insert the LED leads into the two holes meant for the bulb leads. LEDs only work if the current flows in the correct direction. If you insert the bulb the wrong way, it won’t light up. If you get the bulb the wrong way round, simply try the other way (getting it wrong won’t hurt the LED).2

Next I screwed the flashlight head back on (but not all the way down). I then unscrewed the lens cap. Insert the three nylon washers over the LED bulb. You may want to sand the inside diameter a bit to make them fit easier. I also put a few drops of lubricating oil on the washers so they can slide against each other more easily. This is necessary because flashlight head rotates, but the bulb will stay still.4

Lastly, put the metal washer on top of the nylon washers. Note that I painted my steel washer black with some spray paint, but this isn’t necessary. Put the lens on top of this, then screw the lens cap back on. Screw the flashlight head down until the bulb turns off. Your LED conversion is now done!

5

I tested the performance of the flashlight against several other flashlights. Compared to a standard mini-maglite with the incandescent bulb, the LED conversion is definitely brighter and more tightly focused. I haven’t tested the battery life, but I believe it will be better than the incandescent version (1200maH AAA’s plus 20 mA bulb means 60 hours of continuous use, while the standard bulbs are quoted for 5-6 hours).

6

Compared to a $15 9-LED flashlight I have lying around, both maglites are significantly dimmer. I took the following three photos in complete darkness, with each of the flashlights aimed at a white wall from the same position. The camera does not accurately capture the differences between the flashlights. The LED maglite was definitely brighter than the standard maglite, but it was also more focused. The 9-LED flashlight was definitely brighter and less focused than both.

comp-mled comp-mag comp-led
Maglite LED Conversion Standard Maglite 9-LED Flashlight

 

I have seen similar mods done with 3mm LEDs that keep the reflector. This would work fine and cost even less than my mod (if you have the reflector), but 3mm LEDs are significantly dimmer than the 28,500 mcd 10mm LED I used. Radioshack’s brightest 3mm LED is 5 mcd (5700x dimmer), and their brightest 5mm LED is 7000 mcd (4.1x dimmer). The reflector is not necessary for LED flashlights. Incandescent bulbs put off light in all directions, making the reflector necessary, LEDs are highly directional.

Other possible maglite mods would be to use several 5mm LEDs (I think 4 would fit) on a small circuit board, running them in parallel. With white LED’s, this would lead to about the same brightness as my single LED mod. But it opens the door up to the possibility of using non-white LED’s. For instance, you could use red LED’s for night vision, infrared LEDs for heating or night use of video cameras, or ultra-violet LEDs for scientific use or for black light effects.

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