LED Flashlight Conversion

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As hurricane Sandy was nearing the New York area, I gathered up all of our flashlights including the cheap giveaway ones like this Mets flashlight.  I made sure they all had batteries, but one flashlight had a bad bulb even though I had plenty of C batteries to use in it. I thought of a way to make my own LED replacement bulb using the base of the burnt out bulb, some LEDs I salvaged from some yard lights and a corner of a PC board.
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Step 1: Yard Light

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When we bought our house, there were a bunch of these lights all over the yard. Only one of them still worked, so I tried to fix the rest of them. It seemed like they wouldn't charge, and I guessed it was because the plastic over the solar cells had become hazy and light wouldn't shine through anymore. I tried sanding the plastic, but it turned out to be a thin coat of resin that the cells were set in. A little rubbing with some fine sandpaper went right down to the cells and they were useless. The haziness never cleared up, and the cells were catching on the sandpaper. Luckily, I was able to salvage the LEDs and a few of the rechargeable batteries. The rest of the parts went to the recycling center.

Step 2: Burnt-Out Bulb

Picture of Burnt-Out Bulb
I had plenty of flashlights, but this one had a burnt-out bulb. I had plenty of batteries, but that wouldn't make this light work. I figured I could use the base of the bulb and make my own LED replacement. Originally, I thought I would use the 2 prongs that electrify the filament but as it turns out, the solder doesn't like to stick to these. I broke the glass gently with some pliers, keeping the filament leads intact, but eventually I pulled the leads out of the base because they were too delicate.

I used the continuity setting on my multimeter while I was still planning to use the filament leads, this isn't really necessary.
eyesee1 year ago
I did something similar right before Sandy. Was charging all the cordless tool batteries, and realized I had a flashlight that came with an old 9.6v drill. The clutch on the drill bit the dust, but the 2 batteries were still fine. Bulb was burned out on the flashlight, so I found 3 big LEDs in the parts box, which happened to have a voltage drop of 3.2V each. Wired them in series, and used that flashlight for the entire 2 weeks we were without power and didn't even make a dent in the first batter.

I did not think of the idea to reuse the old bulb base, though. I believe I'll go back and make that change.
Your salvage instincts are great, Nice project. Bulbs use up batteries so fast they are not economic to use any more.

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