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I need to parallel connected couple dozen cut LED strips. The total current reaching them won't exceed around 2 amps.

My constraint:

  • I can not order any more components for the job.

My tools:

  • Lots of cable, soldering wire, solder, aluminum tape.

My question:

  • Instead of soldering wires for each strip piece and later connecting them together, can I get hard plastic, put on two parallel lines of aluminum tape and solder cables directly from strip there?

  • Or: Can I glue stripped cable on plastic and solder cables coming from strips on it?

That way I have the parallel aluminum or just one set of cables at the end.

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  • \$\begingroup\$ What's wrong with copper wire and solder? \$\endgroup\$ – George Herold Jan 4 '15 at 23:20
  • \$\begingroup\$ 1. What kind of "Lots of cable"? 2. How far apart are the ends of the LED strips you want to connect together? 3. Are the ends of the LED strips you want to connect together all in line? \$\endgroup\$ – EM Fields Jan 5 '15 at 6:49
  • \$\begingroup\$ 1. I have access to variety of gauges, high-temp cables. 2/3. LED strips are laid parallel, same length. Space in between can vary. \$\endgroup\$ – Phil Jan 5 '15 at 22:39
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Aluminum forms a layer of aluminum oxide as soon as it is exposed to air. This is good because aluminum oxide is sapphire or corundum and is very tough. This is bad because it is in insulator. Electrical connections to aluminum chassis use pointy lock washers or press-fit terminals to cut through the oxide. Silver is OK. Silver oxide is a conductor.

Stripped solid copper sounds easy. Or cut away rings of insulation at the needed intervals. If you look inside mass produced low voltage lights you will see lots of the bare copper method.

Here is a way to use solid copper wire with vinyl (or similar) insulation. Using wire that is not too big - say #22 - tie one end to something solid. I use a door knob. Unroll about 6 feet and tie to a screw driver or dowel. Apply strain and try to stretch. Increase the pressure slowly until you feel the copper "yield". You have exceeded the elastic limit and it will stay completely straight. If someone can help, clip it at each end and carry to a table and cut to convenient lengths with an Xacto or razor blade.

Not only are the pieces straight and great for bread-boarding, but the copper has stretched and reduced in diameter so that the insulation will slide freely. You can make little rings of open copper by rolling the wire under the blade to cut the insulation then making a lengthwise cut and peel out the piece. I have been doing my bread-board wire this way since the solderless breadboard was invented, or maybe before? On the bread-board thing, I always had a pair of hemostats to bend the wire and hold it to insert in a hole and make bends so every thing is nice. Neat but not gaudy. If you want to do it with heavy wire, add a little leverage with a broom handle or a jack. You can add that nice science fair or Hack-a-Day look.

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  • \$\begingroup\$ Brilliant explanation, much appreciated! I thought of cutting stripping parts where cables would connect but I am not sure how to part strip in the middle. \$\endgroup\$ – Phil Jan 4 '15 at 23:30
  • \$\begingroup\$ Also, can you please expand what do you mean by an insulator? What kind? I am confused because it is conductive. \$\endgroup\$ – Phil Jan 4 '15 at 23:34
  • \$\begingroup\$ @Phil -- Aluminum in its pure form is an excellent conductor, but Aluminum Oxide is a very good insulator. If you expose pure Aluminum to air, it will oxidize very quickly and soon you will have a coating of Aluminum Oxide on your wire (e.g. the touchable outside surface) and pure Aluminum inside. So your "Aluminum wire" would conduct just fine if you could get to it's interior, but you will have great difficulty connecting to it. \$\endgroup\$ – DrFriedParts Jan 5 '15 at 0:16
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    \$\begingroup\$ What @DrFriedParts said. Think of the white "alumina" gymnasts use on their hands or potters use to keeps pots from sticking in a kiln. It is all the same thing. Alumina, carborundum/corundum as in sharpening stones and grinding wheels, and crystal form sapphire. Good insulator and also makes great IR lenses. Hard to shape. It is the second hardest thing next to diamond - and is already oxidized so handles hot atmosphere. Oxidized layer on aluminum is only a few atoms thick. (I think Star Trek writers didn't know about sapphire when they had Scotty make transparent aluminum). \$\endgroup\$ – C. Towne Springer Jan 5 '15 at 1:28
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Aluminium is probably a bad idea, for two reasons:

Firstly, aluminium oxidizes on contact with air. This is good because it forms a protective patina preventing further oxidization of the metal (unlike iron, which just keeps rusting), but it's bad because aluminium oxide is an excellent insulator. It's not impossible to make a good electrical connection to aluminium, but it takes some care. Ordinary electrical solder is not designed for bonding aluminium.

Secondly, aluminium in contact with copper is subject to significant galvanic corrosion, probably causing your connections to fail prematurely.

In the 60s, copper was very expensive and some people had the great idea of using aluminium for home electrical wiring instead of copper. You can read about all the problems that caused.

You can use copper just fine, though. As long as your wire is thick enough to have low enough resistance that running 2A through it won't waste too much energy (or worse, catch fire), then the particular geometry of the wire doesn't matter much as long as everything is touching the same piece of copper. Take a look at a wire gauge chart: anything less than 18 AWG is probably not a great idea for 2A.

Of course, if the wire is bare you should be confident that nothing will come in contact with it and do bad things. It would be bad, for example, if a metal object touched both at once, since this would short the power supply. At the voltages you are probably using for LEDs (I'm guessing 12V), it's unlikely to present any severe safety hazard, but there's easily the potential for some everyday occurrence to break your device.

If you don't have heavy enough wire, you can always run multiple wires in parallel and the current will split between them, just as current splits between parallel resistors. Remember, wire is just a very small valued resistor.

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  • \$\begingroup\$ Thanks @PhilFrost, again an excellent answer and brilliant explanation! Is there any chance you could tell me if Gorilla tape OR regular electrical tape would be a good idea to sandwich / cover (back and front) the bare copper "bridge" to join the cables coming from the strip? \$\endgroup\$ – Phil Jan 4 '15 at 23:33
  • \$\begingroup\$ @Phil I guess electrical tape could work, but even better might be heat-shrink tubing, or even better, potting the whole thing. \$\endgroup\$ – Phil Frost Jan 4 '15 at 23:35

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