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This web site is intended to show people, step-by-step, how to make an LED "bulb" to replace the lamp in any 3 cell flashlight or headlamp, in particular the Petzl "Zoom" headlamp is what I designed it for. I have run this lamp for over 50 hours in my kitchen freezer and still had enough light to walk around outside with it, although at that point it was annoyingly dim enough that you would be looking for the next chance to change out the batteries.
You will need basic soldering skills and you must be able to do finely detailed work with your hands. Having an extra pair of hands from a helper would be good too. Have fun and let me know if you try it and how it works for you! (Note: This is not really economically reasonable unless you make several of them, get together with a friend and make a few together.) It takes me about an hour to make one now that I've done a few. If you value your time then this becomes an expensive lamp, think of it as a hobby and you will have a fun and useful item when you are done.
Click on the images for a larger and higher resolution version of the images.
1. Get the parts together. You will need: perf board, an old bulb that fits the flashlight or headlamp that you are making this for, a resistor to limit the current (for a 4 LED system running on 3 standard 1.5 V batteries you will need a 13 ohm resistor), a little bit of small heat shrink tubing and four super-bright white light LEDs.
The circuit that you want to create looks like this:
The batteries are from your headlamp the rest will be packaged as part of the lamp. Fit the four LED's next to each other poking the leads through the holes in the small square of perf board. You will want to snug the LED's right up to the board tightly so that your device is no bigger in length than absolutely needed. Think ahead about which way you put the leads into the holes so that you can connect the leads together properly in the next step.
Next you want to bend the leads around to wire all the anodes (positive leads) together and all the cathodes (negative leads) together. Make sure you check your particular LED data sheet to determine which lead is + and which is -. Make sure the plus lead (anode) comes out in the center. Use tiny pieces of heat shrink tubing to insulate the leads from each other. Solder the leads together and trim off the excess except for one anode lead in the center and one cathode on the edge. It should look something like this:
Next clip most of the center lead (the anode or plus lead) off and nip off most of one lead on the resistor. You should have only a few millimeters of lead on each. You will solder these together as shown in the picture below. Cut a small notch in the bulb base to allow the remaining LED cathode (negative lead) to poke out. (You will eventually wrap this lead tightly around the outside near the rim of the base and solder it there.)
Here is another view: 
Now insert the LED assembly into the old bulb base that you have prepared. Let the remaining lead of the resistor poke through the hole in the bottom of the bulb base. Have the LED cathode come out the notch.
Again, here is another view: 
It is time to (1) solder the anode to the base (the resistor wire poking out of the base) then (2) wrap the cathode around the top rim (trim as needed) and solder it to the rim. Next you need to trim things up a bit, snip off the excess wires as close as possible. File off any sharp points or burrs.
After you have soldered both leads then use some epoxy or other solid and strong material and force it into the spaces around the resistor, underside of the perf board and inside the base. Note: do not use fast curing epoxy, you will need some working time here! You can use a disposable syringe or just use a toothpick and dap it into the open spaces. Try to keep the epoxy off the exterior of the base so that you don't create an insulating layer on the outside of the base. The better you do this step the stronger your LED bulb will be. Carefully align your four LED's so that they are all pointing in the same direction, you can either "eyeball it" or you can power it up and actually align the spots, I've found that I can do a pretty good job by just "eyeballing it." If the LED's look like they are all pointing in the same direction they probably are. Now, put a bit of epoxy between the LED's to hold them in alignment. Warning: Do not get any epoxy on the front lens of the LED's or you will ruin the spot quality!
Once the epoxy has completely cured, the last step is to use your file or sand paper (emery board works well) and round off the corners of the perf board and possibly a bit of the LED's themselves. If you are careful and don't mind risking your fingers you can use a bench/floor style belt or disk sander, but go easy or you will remove too much material! You want to remove just enough material to allow it to fit inside the lens cover of your flashlight/headlamp.
Here is the final result as a bare bulb and installed inside a Petzl Zoom headlamp (with the front off so you can see it).
You are now done! Congratulations, you now have an LED lamp that you can exchange for your battery eating halogen lamp. Enjoy!
Send Dr. Sohl a message at jsohl "at" weber "dot" edu (The email address is written this way to help reduce the amount of spam I get, sorry for the inconvenience.)
Please let me know about any dead links.
This page was last updated on April 12, 2006.
