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
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.