Instructables
Picture of LED Flashlight Conversion 2
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

Picture of 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:  http://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.
Rouverius6 months ago

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.

mr1141 year ago
Wow, I actually have this exact flashlight laying around! Will give this a shot :]
ProfMuggs1 year ago
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?
russ_hensel (author)  ProfMuggs1 year ago
You could, but you would need to use a rectifier to get DC instead of the AC it is generating.
ehudwill1 year ago
Great idea setting them in wood. I will be using this one.
Orkekum1 year ago
Awesome work awesome idea!