How to Mod and Old Flashlight Into an LED One




In this instructable, I will show how to mod this classic model of flashlight into a new LEDs flashlight. Basically replacing the old light bulb with a bunch of LEDs.

Step 1: Material

This is a pretty cheap instructable (provided you have the flashlight already!).

You'll just need:

-The flashlight
-18 LEDs
-A bit of a styrofoam tray (or anything that could work as a frame for the LEDs but also that can be pierced, like wood, cardboard, plastics...);
-Some thin wire

And as tools:

-Wire cutter
-Cutter knife

Step 2: Assembling the LEDs

You just need to cut a circle of the white foam and drive the LEDs into it. There's one in the middle, six in the inner circle and 11 in the outer circle.

Make it in a way that pins with the same polarity are all in the same circle as shown on the circuit scheme. (Notice that in the circuit scheme there are more LEDs than I finally put).

Step 3: Wiring

I'm not changing anything in the flashlight except the lightbulb so the voltage provided remains the same, that is 3 volts (two batteries of 1,5V each). Each LED needs a bit more than that*, so we'll just need to connect them altogether in a shunt configuration (i.e. all positive pins together and all negative pins together). We won'to need any current limiting resistor as the intensity will be less than the maximum, because of the low voltage applied.

The simpler way to do it is as you can see in the pictures. Arrange them in circles, and then connect the circles with the same polarity. Then connect the circles to the battery terminals.

*The voltage will be less than required, and so it will be the light output. In case you want more voltage you'll need to hack the batteries system too. For example fitting 3 smaller batteries of 1,5V each. In that case you would need a current limiting resistor, but that's out of the scope of this instructable).

Step 4: Close and Enjoy

Now just close the lid in which you fitted the LEDs and be ready for the light!!

If you decide to do it, please try to do it cleaner than mine!! Consider mine as a first attempt to be improved.



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    14 Discussions


    4 years ago on Step 4

    I did basically the same thing, but also bought a 3v to 5v DC/DC converter. It's the size of a small postage stamp and fits nicely inside the head of the flashlight. Really helps with the brightness and, I don't know if yours did this as well or not, it solves the problem of the flashlight not providing full brightness until you've wiggled the switch around a bit.

    1 reply

    Reply 4 years ago on Introduction

    I should clarify since I didn't realize this when I posted my comment - I was working with the 2xD Cell version of this flashlight, so it was a bit roomier.


    7 years ago on Introduction

    so what you are saying is, the physical size of the batteries does not matter?
    all that matters is the voltage,watts & amps? is that right?

    Sir this was a great read, but, being the uneducated man I am, I still get confused easily.

    TY for sharing Sir. :)

    1 reply

    Reply 5 years ago on Introduction

    All standard batteries, AAA, AA, C or D have the same voltage, 1.5 volts. The only difference the size makes is the amount of Ah (amp hours) which is a measure of how long the battery will continue to supply the rated voltage. For projects such as this the physical size does not matter, only the voltage. The larger batteries will power the light longer, but as LEDs are so much more efficient than the original bulbs two AAA batteries will keep the light on several hours more than the 2 C or D cells did for the original light.


    8 years ago on Introduction

    This seems like the "mini" version of the full size Army flashlight we carried. You're right, it was carried on the belt, or set on a table or ground. There was, and is in this mini model, and extra bulb in the base. And the different lenses. I just got one each from 2 different Army/Navy stores, one w/ a "prism" reflector. I discovered that the CR 123 or other 3V batteries also fit w/o adaption! So I put a KPR 118 7.2 V bulb from "The Shack" in it and had an Instructable version of a Tactical flashlite that I have been making from various flashlites that I could find. With some trial and error. Like tearing up the insides of the chamber meant for 2 AA batts with a 5/8 " bit. With this flashlite and others, I found I was melting the reflector if I left it on more than a few seconds. So I took off the lens to let it breathe. Working OK so far. I'm having trouble finding even cheap flashlites that are NOT an LED.

    It's a US military flashlight; we were issued them in the US Army. The bottom portion can be unscrewed and has a blue, red, green, and clear lens to change the color of the light.

    it´s angled because you would use it in your pocket or belt, i think

    esta en angulo porque se usa metida en el bolsillo o en el cinturon, si no me equivoco


    9 years ago on Introduction

    Very cool. I have been trying to do the same thing with one of my old Army lights, and a 9 LED light that broke on me. I like your idea of just using a larger amount of lights together. How long do the two D Cells last now? I know the old bulbs you would get between two and four hours.

    2 replies

    Reply 9 years ago on Introduction

    Thanks mate! Well the old lightbulb was working at 3 volts, 0.5 amps, that is 1.5 watts, now at the same voltage there are 18 LEDs at 20 miliamps each, that is 1,08 watts, so if my calculations are correct it should last for more. And thanks for the word!