4LED PR bulb in rayovac 4AA w/pics,beamshot

I just finished my first real mod, I had a 4LED module from a cheap flashlight and I took the LEDs off of the board cut the board down and redid it and soldered the LEDs back to it after I ground down all the lipped edges on the bottom of all 4 LEDs. I then got a PR base from pulling a bulb apart I had no use for a PR17 and proceeded to drill a hole in the side of the bulb for wires to go out of it. My idea was an adjustable resistance 4LED bulb. I had to use a ream to hollow out the hole of the rayovac's reflector and replace the lense on the front with a piece of plastic I cut from an old CD case. I can revert the light back to original by replacing the bulb with the .75A 4.8v bulb and the lens.
Final cost: 1.09 for the light I got the LEDs from, 3.27 for the rayovac light at walmart and several hours of figuring things out.

I took the first two fuzzy pictures during construction of the bulb and wasa too tired to take more at that time, the rest I took when I was awake and made sure they were crisper although several shots I had to delete because of excess fuzziness.



The rayovac light is dark green 2x2AA format with rubber lanyard. I soldered a 10ohm resistor to the bulb but change change it easily anytime or even solder in a boost circuit or a dimming control.

I will try and take more pictures later if anyone is interested.

Here are some better pics, I am having problem with the autofocus on this borrowed toshiba 4.3mp camera.

Inside of the rayovac light.

Bulbs ready to swap.

Business end ready to go.

Finally the beam shot.

The reflector picks up a fair amount of spill causing an interesting pattern. I had to remove the orginal magnifier lens assembly because it skewed the 4 LEDs into a widening 4 seperate *splotches* of light not useful beyond about 5 feet.

It came out better than I expected and if I had new LEDS with longer leads the mod probably wouldn't have taken half as long to do. It is a nice light for under $5.00.

Anyone figured out an easier way to grind the lip off of LEDs? I used a utility knife and a fingernail emery board on these. Perhaps a dremel jig would work better. I also thought of putting a selector switch with seperate resistors so you could use a very low output setting to increase run time dramatically.

My next idea is figuring out a cheap 2D host this idea would work in that is common and decent enough to work with. The problem with the external wiring is a lot of lights wont work with it if they use screw on bulb holders and having to ream reflectors out is slow, I should figure out a large drill size to use instead.

Any comment on how to improve this idea would be welcomed.
My hope it somehow I could make these really fast and easily and cheap enough to offer to others.

Nice job!

Thanks, I have been playing with this light a lot since I made it. It is overdriving the LEDs at about 40ma each at 5.6v which is about what I wanted since after the heavy duty batteries die I am going to use nimh and they start out at about 5.6v and stabilize about 5v. I was looking for a 12ohm resistor but didn't have one and since I have hundreds of other resistors this works out fine. I am guessing run time on my nimh will be about 8-10 hours (1500mah).

Great job, i cant wait to start doing mods like that.

Me neither. Oh, wait I just did one. /ubbthreads/images/graemlins/crackup.gif
If I had not used LEDs pulled from a board I think this mod would have been easy except for making the round circuit board. The board I pulled the 4 LEDs off of had a center round copper trace smaller than a dime and an outer trace. I took the LEDs off of it and using a pair of dikes (cutters) I trimmed it down to the center size, notched out the 4 holes as slots and drilled a hole in the center as a pass through. I soldered the center + of the LEDs together (was hard with short leads) and then positioned the slots over the - leads. I used some poster putty to keep it in place while I soldered one lead to the bulb slot. Next one I plan on doing I will put a slot on the opposite side I think to make it stronger.
here is a pic of the 4LED module I modified to make this bulb (on the right in a light I plan to mod one day)

I have to make a boost circuit to fit which may require me to make a new LED board for it to put them a little closer together, maybe with room to mount stuff on the edges of the board.

My advice on modding is look around the dollar stores for cheap host lights.. 3 and 4 cell lights make for the easiest mods you can use resistors like I did, I plan on making a few boost circuits and use them in 1 and 2 cell lights I have collected. Also look for lights with LEDs in them you can tear apart for the LEDs, it may be cheaper than ordering them if you only need a few, when you get more confident and have the funds put an order in for a bunch like I plan to hopefully after the holidays.

Just thought I would add I just saw the host light of this project at Walmart on red tag (closeout) for $2.50 now. I may make another one of these lights for my car.

Just another update, the host for this light is now down to $1.50 at walmart with 4AA heavy duty rayovac cells. I also figured out an easier way to grind the lips off 5mm LEDs. I have some plastic tubing from water line I cut off a foot and the LED fits tightly in it. I use an upright belt sander and sand off the last 1/16 inch at a slight angle using the tubing to hold it. It took me close to an hour to clip and grind the LEDs for this mod and took me 12 minutes to grind a dozen 2600 mcd LEDs for my next project using this method.