I’ve been busy, busy, busy designing parts for the chandelier. The picture to the left shows a rendering of the parts I modeled in CAD. I dragged my Dad into the project for the wooden parts – he has a lathe and I don’t, but mostly because he’s really good at woodworking. (Thanks Dad!) He also ended up helping with a lot of the other parts, and he had many good suggestions as we worked out how everything will fit together. As I write this, he’s finished the wood parts, but I haven’t picked them up yet. I can, however, show pictures of our progress on the other parts.
Each of the six arms of the chandelier will end in an acrylic flower. Inside each flower will be a cluster of three high-powered LEDs. (I’m using neutral white Luxeon® Rebel LEDs in LuxDrive’s Endor Star™modules.) These do get hot so they need heat-sinks. The picture on the left below shows how the parts of the light assembly fit together. The circular thing with the fins is the heat-sink, of course. The acrylic flowers will be attached to the metal disk. The metal cylinder with the threaded pipe-nipple screws into the heat-sink. The white flat thing on the green wire is the LED module. The little orange-ish thing nearby is a thermistor that I’ll be using to measure the temperature of the LEDs. The little clear plastic piece is a wide-angle lens. Finally, the rightmost cylinder is a hollow can that fits over the LEDs and the other metal cylinder. My Dad drilled and tapped everything so all the parts fit together quite nicely. The right picture below shows how all those parts once they are assembled. Between any parts that should conduct heat, I used thermal grease. The thermistor is attached to back of the LEDs with thermal adhesive.
Since my last article (see part 1), I made CAD drawings of all the acrylic parts and cut them out on a laser cutter. My Dad drilled and tapped those holes that need to be threaded. The pictures below show the parts for the flowers, the big down-swoops, and the up-swoops (assembled to a green acrylic disk; also showing the crystal bowl and break that will be on either side of said disk). As you can kind of see in the pictures, the finished leaves are made of a stack of three layers and the flowers are a stack of two layers.
I assembled the flower pieces onto a couple of the light assemblies and attached those to the crystal arms. The picture below shows those two arms hooked up to the electronics that will drive the chandelier. Off-picture are the other four light assemblies (as of yet without flowers and not attached to their crystal arms). Once I got everything hooked up to the driver circuitry, I fired it up – the light output is impressive! Photons blasting out everywhere! I don’t have any pictures of it lit up since the light would be rather blinding for the camera.
The temperatures are surprisingly close to what my calculations said they would be. I computed that the temperature would level out at about 60° C (140° F) when running the lights at full power. Now that I could test the actual parts, I let it run at full power for a while. After about an hour, the temperatures leveled out at a maximum of 58° C ± 8%. [note #1] So anyway, woot! The temperature is manageable and the chandelier won’t go up in flames! (Nor will the acrylic melt, nor will the LEDs exceed their recommended operating temperatures.)
note #1: For the curious, the tolerance I gave for the temperature readings is just that of the thermistors plus the resistors I’m using. I could calibrate out much of the resistor variance since that’s easy to measure but I probably won’t bother since I just need an approximate reading to ensure that the temperatures aren’t getting too high.