LED Flashlight Conversion 2




About: For now see me at: http://www.opencircuits.com/User:Russ_hensel

I have an old Russian generator flashlight that no longer worked, I figured the bulb was blown.  Rather than just replace the bulb I converted to an LED.  The LED does not use as much current so it is easier to crank the generator, and the LED will last longer than a bulb.

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Step 1: Tools and Materials

Broken Flashlight

Soldering, stripping cutting tools.

Hot glue gun

4 Super-bright LED's

Step 2: Plan

My project is very close to this one:  https://www.instructables.com/id/LED-Flashlight-Conversion  so I will just note the things that I did differently.

First I figured out the properties of the generator.  By connecting the LED with and without series resistors I discovered the internal resistance of the generator was effective in limiting the current, so I did not use a series resistor.  I also determined that the LEDs were better in parallel than series.  A o-scope showed that the generator generated AC.  That meant a couple of things, one is that reverse current might damage the LED's and the other that the LED was only on half the time.  I could have used 4 diodes in a full wave bridge, but I decided instead to use 4 LEDs in parallel 2 connected in each polarity.  This limits the reverse voltage and now 2 LEDs are on all the time.  I also made a little jig to hold the LEDs while I soldered them.

Step 3: The Wiring

I did the wiring using "dead bug style", no board, just soldered up the components.  The jig helped a lot.

Step 4: Finish

I removed the old bulb assembly, ( the bulb was ok, one of the leads had broken ), hot glued the LEDs in where the bulb had been.  I reassembled the flashlight, it works great.

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    9 Discussions


    5 years ago on Introduction

    Actually, I had a flashlight like this as well. I had hoped to do a similar project. Sadly, when I disassembled it, the cheap alloy flywheel had literally crumbled apart. Glad to know someone got to build this though.

    1 reply

    Reply 2 years ago

    I would try it, stick a single led in the circuit and pump gently. If it works go for a more complete circuit. Let us know.


    2 years ago

    Hello, I have a very similar flashlight to this one, in working condition. After removing the cover, I measured the voltage, and it seemed 1-2 V~ comes from the generator/dynamo, and it is way too few for white leds to light up. Or not?


    6 years ago on Introduction

    Wow, I actually have this exact flashlight laying around! Will give this a shot :]


    6 years ago on Introduction

    Nice job! Now that you are using less power for the LEDs, maybe you could add a capacitor and make it stay lit for longer?

    1 reply

    Reply 6 years ago on Introduction

    You could, but you would need to use a rectifier to get DC instead of the AC it is generating.


    6 years ago on Introduction

    Great idea setting them in wood. I will be using this one.


    6 years ago on Step 4

    Awesome work awesome idea!