I'm in the process of building a 16x16x16 LED cube and am looking for a way to connect two wires at a 90 degree angle (e.g. +) without soldering them together. The connection does not need to be electrical, it can be structural only. The reason I don't want to solder them is that I'm constructing the cube as 16 vertical planes. If and LED goes out somewhere in the middle of the cube, I'd like to be able to take the entire 16x16 plane out, fix it and put it back. The 16x16 planes will be soldered, as will at least one horizontal connection on each level, but I need more horizontal connections for structural support and don't want to try de-soldering a joint in the middle of the cube.
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2\$\begingroup\$ What leads you to believe that an LED might go out? Driven properly, they should have lifetimes that will outlast any expense or time taken to make the cube repairable. \$\endgroup\$– Kevin VermeerJun 29, 2011 at 1:07
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\$\begingroup\$ @Kevin Vermeer - Because they're cheap LEDs :). I built an 8x8x8 and one went out about a month later. About 1% are dead or dim out of the box, some others are close. \$\endgroup\$– NoneJun 29, 2011 at 2:41
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2\$\begingroup\$ I'd hazard a guess that they're just not properly derated by the manufacturer, or you're running them too close to their maximums. You can get a lot more life out of an by simply running them cooler. \$\endgroup\$– Kevin VermeerJun 29, 2011 at 2:51
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\$\begingroup\$ @Kevin Vermeer - Thanks for the suggestion, I don't think that's the issue, however. I bought 5,000 LEDs at around $.01 each, so I don't exactly expect them to be top-of-the-line. The packaging says 3.5V/25mA, I'm running them a bit below that (5V through an 100ohm resistor to kill the brightness a bit) 1/16th of the time (the layers cycle quickly). \$\endgroup\$– NoneJun 29, 2011 at 16:26
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2\$\begingroup\$ This question seems to be off topic: It is about mechanical, not electrical engineering. Can you explain how your question is on topic? See the FAQ on what questions to ask for some tests you can run. \$\endgroup\$– Kevin VermeerJun 30, 2011 at 13:30
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2 Answers
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The first thing I would try is a spring, like the ones used in those old Radio Shack electronics kits from the 80's.
If you can source one long enough, then it might be pretty easy to remove a wire from the middle, provided that you have reasonable spacing between layers.
Maybe some continuous-length extension springs from McMaster will do the trick.
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\$\begingroup\$ Hey, I had one of those in the seventies! A less luxurious version, though. It had a real "IC", something like two transistors and 4 resistors. \$\endgroup\$– stevenvhJun 29, 2011 at 6:41
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\$\begingroup\$ @stevenvh Mine was also less fancy. It was just in a cardboard box. Unfortunately, back then I didn't have any appreciation for electronics, nor someone to really explain it to me, so I just blindly followed the instructions. I think my favorite was the one that make a siren sound. :) \$\endgroup\$– DaveJun 29, 2011 at 13:13
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\$\begingroup\$ I'm not quite sure I follow what you mean by removing a wire from the middle -- with a spring? The 16x16 vertical planes are "solid", in that they're soldered together. The only "free" wires are connecting the planes together (electrical ground & structural) \$\endgroup\$– NoneJun 29, 2011 at 16:18
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1\$\begingroup\$ @cwolves I guess I'm a little confused about what you're trying to do here. So I guess you don't care about the electrical connections between layers, and you only want to know how to quickly replace an LED on a given layer? Do you have a schematic or sketch that you can post? \$\endgroup\$– DaveJun 29, 2011 at 16:30
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\$\begingroup\$ @Dave - I can post a sketch in a bit, let me see if I can explain it better first (on a ferry at the moment): I have a 16x16 vertical grid of LEDs with the anodes of each vertical column soldered together and the cathodes of each horizontal row soldered together. This grid gets placed vertically with the bottom LED's anode sticking through a hole in a board to hold it up. Next to this plane, another 16x16 grid of LEDs gets placed. Each 16x1 cathode line gets soldered together via a single wire on the outside-most layer between the two planes. \$\endgroup\$– NoneJun 29, 2011 at 16:47
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So your cube is comprised of 16 rigid "slices", each one with 16x16 LEDs? And the problem is that the slices wobble and fall over? Try putting some connecting rods through the gaps between LEDs, as shown in this ASCII diagram that I apologise abjectly for.
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You may need to put some kind of spacer on the top of the cube too, to keep them at the right distance. To extract a slice, lift off the "lid", pull out the connecting rods and withdraw the slice.
The other option is to reinforce the very bottom of the slice and mount it like a circuit card in a backplane.
