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One of my 12V fluorescent light ballasts in my RV burned out. I decided to replace it with LEDs using 6 cheap LEDs, a couple LED drivers, and using https://www.instructables.com/id/Replace-Low-Voltage-Bi-Pin-Halogens-with-LEDs/ as a guide. The parts were all purchased from DealExtreme.

This is Part 1 where I will hook up the LEDs. In Part 2, I dress up the exterior of the light with bamboo and acrylic.

Step 1: Tools & Materials

Tools & Materials:
Fluorescent Light
6x LEDs (or as many as you want, in multiples of 3 per driver) - $20.16
2x LED Drivers - 12V / 85-265V - $5.04-6.64
1x Switch - $2.99 (optional)
12x #4-40 x 1/4" Screws - $1.96 (Home Depot)
12x Non-conductive washers (optional, Home Depot or RadioShack may carry)
1x tube thermal paste - $7.77

Total: ~$30-35

You can re-use the switch but I chose to purchase a different switch so that I can install it on the outside of the bamboo box I plan to make in Part 2. The screws I initially used were computer screws I already had but I switched to the screws I found at Home Depot because they included nuts. I included the non-conductive washers because I had some issues with shorts with the large head of the screws I initially used. While there shouldn't be a problem with the #4-40 screws from Home Depot, I decided to play it safe.

Other Tools & Materials:
Solder Paste
Soldering Iron
Epoxy
Liquid Tape
Wire cutter/stripper
Wire
Drill and 1/8" bit (optionally, 7/32" bit, too)

This list is what I used but all you really need is solder/solding iron and some wire (you can salvage some from the fluorescent light but I chose to leave it intact).

Step 2: Prepare the Fixture

I started by removing the fluorescent light and measuring out 2.5" intervals (for an 18" light). I then placed the LEDs on the fixture and marked out two screw holes each. For the #4-40 screws, I used 1/8" bit to drill out each hole.

Step 3: Attach the LEDs

After drilling out the holes, make sure the LEDs line up with the holes. As long as they do, put a small amount of thermal paste (such as Arctic Silver) on the back, place the LEDs over the holes and attach the screws (use the optional non-conductive washers in this step if you wish).

Step 4: Prepare the LED Drivers

For this light I used two LED drivers, each driving three LEDs. To reduce the amount of wire and simplify things, I soldered the + pin of the drivers to each other and the - pin of the drivers to each other. This is only necessary if you get the 12V driver meant for halogen bi-pin lights (shown below). The 85-265V AC driver has wires soldered on. For the bi-pin drivers I used, the color of the wire on the same side of the pin lets you know which pin is + and which is -.

On one of the drivers, I soldered a switched wire (red) and a ground wire (black). If you are re-using the built-in switch, solder to that. Otherwise, in preparation for enclosing the fixture in a bamboo box (Part 2), I drilled a 7/32" hole in the side of the fixture and attached the red wire to the new switch. I also threaded a second red wire back from the switch into the fixture for attaching to 12V.

Step 5: Solder

I started with the "left" half of the light.
1. The - of the driver (upper right of photo) was soldered to the - of the closest LED.
2. The + of the same LED was soldered to the - of the middle LED.
3. The + of the middle LED was soldered to the - of the left LED.
4. The + of the left LED was soldered to an extension wire connected to the + of the driver.

I then repeated the above steps with the "right" half of the light.

Step 6: Clean Up

To finish up, I epoxy'd the drivers to the fixture, covered any exposed wire/solder I thought might short out with liquid tape, attached the driver's black wire and the switched red wire to a 12V source, attached the fixture to the ceiling, and put the cover back on. All done with Part 1!

Step 7: Done!

Done! Stay tuned for Part 2 where I enclose the fixture in a bamboo box and replace the plastic lens with a replacement made out of acrylic.


Troubleshooting:
I had a few issues with LEDs not lighting up due to shorts. I believe my problems had to do with using excessive amounts of soldering paste. Just scrape away all the excess and everything should work great!
How much would the florescent have cost to replace? and how much power did it use?
A new ballast would have cost $20-30 and used ~15 watts.
so your probably using less than 4W now, and it ends up being cheaper and brighter :)
Oh, and the LEDs are MUCH brighter!
$20 for 6 leds???? buy a led flashlight and you've got it for 5 instead ;)
These leds are "high intensity" leds. There BLINDINGly bright, and put out a lot of heat.
i didn't notice that were star-shaped :P
They're heat-sinks - high power LEDs

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