Monday, November 12, 2012

LED Retro-Hacking

If you've been around mountain bikes as long as I have, you probably remember halogen bike lights.  You know, the ones that sucked so much power (and turned it directly into heat) that to get more than a couple of hours of pathetic yellow light you needed a battery that replaced your water bottle?  (Don't worry, if this concept is new to you, you didn't miss much).   

Anyway, it turns out that I have one of these monstrosities in my basement, and being a die-hard New England cheapskate, it felt wrong to throw it away for something more modern.  A little internetting (yes it's a word), found these LEDs for a trivially small amount of bling, and I couldn't help but wonder if the gigantor heat-sink of old might be convertible to something usably modern.  

Spoiler:  it can.   and Here's how...

Step 1: Cut apart the original reflector and remove the bulb (yay, DREMEL).  

Step 2:  Solder some wires to the original pins and epoxy everything in place (forgot pic...)

Step 3:  Solder the LEDs in series on a little circuit board (I repurposed the board from an old garage door opener for this, cutting up the ground plane to make the layout I needed.  This was nice for heat dissipation too (then I forgot to take a picture).  Some thermal paste can be used here to make sure the board pulls heat from the LED, but it may not be necessary.  

Step 4:  Attach the power wires to the circuit board

Step 5:  Superglue the circuit board to the old reflector, which was ground down to have a bigger opening.  

Step 6: Superglue the base of the old bulb to the back of the circuit board 

Step 7:  Install modified bulb / reflector (with the right polarity!)

Step 8:  retake the night!

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