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:
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
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:
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.
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!