I’m working on a pendant lamp design for the high intensity LEDs. The first challenge was locating the right LEDs. Currently, it looks like the best price to watt LED is the Luxeon Rebel. The problem (and virtue!) is that they’re amazingly tiny. They are also surface mount. This means that the only way to get these things both lit up and cooled is to mount them on a PC board. Like their cousins, they run hot.
Fortunately, a German company, LED-TECH, makes tiny PC boards for the rebels. They can mount one, or a cluster of three, wired in series. They also have boards which mount three so they can be powered individually, for RGB applications. Might be nice as a poor man’s dimmer, too. The trick was soldering the LEDs to these boards. Normally, you’d use a reflow oven. I ended up using a standard kitchen hot plate and one of those exceptionally cool remote thermometers with a frickin’ laser beam. I went blind making microscopic solder chips, and carefully dropping the LEDs in just the right place. Then, I cooked ‘em. I had the whole thermometer going, I’d done a dry run on the plate (raising it to the temperatures recommended in the Luxeon literature) and it turned out to be a waste of time. In the real world ™, the solder just melted, and that was that. I did 4 boards, and they all turned out perfectly, though you can see from the photos that the LEDs scooted around a little. Sparkfun has a guide that talks a little bit about reflowing with a skillet. It’s far simpler than I anticipated.
The next step was making glass shades. I found that the best source for glass shades are votive candle holders. They’re cheaper than glassware, and they already have light in mind. I used an airbrush to paint the insides of the votives (after chopping off the bottom and grinding it flat). The resulting look is in the pictures, but the photos don’t really do it justice; they look great. To avoid the spotlight effect (they currently cast a large and harshly defined “spot” of light) I’m going to fit them with a glass diffuser - just a piece of circular frosted glass that’ll fit into the end. The little closed glass dot is the bottom of one of the champagne flutes ($3, thanks, crate & barrel!). I thought it looked cool, so I saved it, and it’s really neat when it’s all lit up. I’m going to put a bunch of these alongside paths, on top of fence posts, etc.
The paint is a “glass paint” by Jurgen Industries. I ordered both the “Creamy white” and the “white opaque”. You want the White Opaque, stk #R66S. I’ll do the glass frosting with either the R71S (Lacquer base frost) or the R8FTX, “Frosted texture”. I’ve got enough going on without having to get into sandblasting to make a diffused. I’m damned if I can locate a source for frosted glass.
The next challenge is going to be turning these shades into hanging pendant lamps. I’ve come up with a combination copper heat sink and hanging fixture. It’s a 1.5″ cylinder which will hang on two solid brass welding rods, which will also provide the electricity. The rods will fit into Delrin (or nylon) sleeves, which will be press-fit into the heat sink. I’ll shim the difference between the outside of the sink and the inner diameter of whatever I end up using as the glass shade. I’m thinking that no two of these lights should be alike. If I want to hang the LED a little lower, I’ll thread some 20mm copper rod and tap the sink. That would leave the source point for the light lower, which will make the cast circle of light larger. This might be necessary for the champagne flutes, for instance.
I used this project as an excuse to buy some rapidograph pens, I’ve always wanted to try some out. I like the results.