More LED lights

I broke down and decided to experiment with Luxeon Lumileds. (From a pure value and ease perspective, I still recommend re-purposing a 12v LED worklight.)

I choose the 3 Watt Lumiled, and purchased individual emitters, which must be soldered onto an appropriate heat-sync. (I felt that this would give me more mounting options, in retrospect, I should have chosen the pre-build Luxion Stars, with integrated heat-sync.) I choose a large diameter copper wire to be my heat-sync and mounting system. Soldering anything to copper is difficult, because it works so well as a heat-sync.

By the time you get one part of the wire hot enough to melt solder, the entire wire is very hot! This is a problem when soldering sensitive electronics (such as LED’s) that can be burnt out by too much heat for too long. Technically, the Lumileds are rated for 260 degrees C for a maximum of 5 seconds. In practice, I really baked them, and only one broke! (note that in my 3 LED array, I ended up using only two working LEDS ). To make things slightly easier to solder, I tinned the copper wire in three places, and the back of the LEDS individually before soldering them together.

The lumileds themselves are not cheap, but the main thing that makes this led array much more expensive than my previous one is the PowerPuck constant current driver. This driver circuit is supposed to provide a constant 700 mA (0.7A) to the LED’s, which keeps them operating at their peak output without causing them to burn out prematurely. Unfortunately, when I used an ampmeeter on the array I found that it was only drawing 0.4A. This is twice what my 12V worklight array draws, but 0.3A lower than it should be.

The LED’s are quite bright, easily brighter than the 1W incandescent bulb they replace. In the second image above you can see the LED’s lit up between the two remaining 1W bulbs. I only ran into one problem when installing the LED’s. I placed it in a light fixture that was mounted on the bottom of the penthouse pop-up top. These two lights are powered by a 2 conductor cable that comes up from Van body. The SportsMobile installer reversed the conductors at some point, because when I turned on my new LED with PowerPuck, I heard a sharp “pop” and the magic smoke escaped! Unlike the previous fixture that was on the van body, the fixtures up top have +12V on the “white” ground wire (that shorts to the frame!) instead of the “red” hot wire that is switched. It didn’t matter for incandescent bulbs, but the reversed polarity blew out my first powerpuck. Just another reminder, never assume that the guy before you used the correct polarity!