Here's how I did it.
Step 1: Supplies
- Soldering iron and solder
- Third hand
- Electrical tape (heat shrink tubing would be much more effective)
- Needle-nose pliers
- Two part epoxy
- Super glue (Krazy glue would be better)
- Heavy duty scissors
- 6 18mm nuts
- 18mm bolt
- 20mm nut
- White 5mm LED
- Tactile switch
- Switch cap
- Ring for keyring (I don't actually know what that is, I just found it in my junk box)
- Small spring
- Positive terminal plate
- 3 1.5V button cells
Step 2: Modifying the parts
For the nut with the switch, I drilled out a hole that would be big enough for the switch and the cap.
For the battery compartment I also had to drill out the nuts, because even though the cells would have fit inside, I couldn't fit in the insulation.
Step 3: Button
Then I attached a wire to one lead of the switch, which would go to the positive battery terminal.
To make sure that the switch stays, in place, I jammed in a small piece of cork (wood or plastic would work just as well).
Step 4: Battery Holder
To insulate the battery compartment I rolled up a small piece of paper pushed it inside the drilled out nuts.
I glued a piece of paper (insulation) to the sawed off end of the screw and glued a small spring on top of that.
Step 5: Glueing it Together
For the smaller parts of the flashlight (like the switch, the spring, etc) I used Scotch Super Glue, just because it's much easier to use it on very small surfaces, for details. Epoxy is much stronger, though, so use it whenever you can.
Step 6: LED
To insulate the two legs I used electrical tape. Not a very good choice, but I didn't have any heat shrink tubing.
When you get the LED to work you can glue on the rest of the nuts. To finish it off I added some washers at the front. The washers also hold the LED in place.
Step 7: Done
Even though it works, mines had a loose connection. Here are some potential improvements:
- Silver solder the nuts together: This will allow electricity to pass through the wall (nuts) of the flashlight, and will make the whole thing much more durable. That way you won't need to worry about the positive wire (the red one) getting entangled in the spring, and will create a much cleaner finish.
- Use heat-shrink tubing instead of electrical tape: My best guess is that the insulation of the LED is what causes the loose connection. Heat-shrink tubing would make it much cleaner and would probably eliminate any short circuits.
- Use bigger Nuts: Bigger nuts would make everything much easier to work with, and you wouldn't have to drill them out for the button cells to fit inside.