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I'm planning a light sculpture. It will consist of a large number of RGB LEDs mounted on a tree-like galvanized steel frame. Each LED has four wires -- GND, +5V, data-in and data-out. For aesthetic reasons, I would like to use magnet wire to connect the LEDs, intertwined with the steel frame. So if one looked closely at the sculpture, one would see a twisted bundle of thick steel wire (non-conducting!) and several strands of conducting magnet wire.

I'm worried that the thin insulation on the magnet wire might wear off and cause a short circuit, either with the steel wire frame or with other lengths of magnet wire.

How much jostling/rubbing/abrasion can magnet wire take before the insulation is compromised?

Once the sculpture is complete it will not be handled very much, but during assembly there could be a fair amount of jostling.


[edit] I know there is no way to give a precise answer. I was looking for something like "I've done project XYZ which subjected magnet wire to a certain amount of abrasion, and based on that experience I would guess this project will [or will not] work."

Also, I should have specified that I plan to use magnet wire with multiple coatings.

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Difficult to quantify. Is there a unit of jostling? (The Joss?) –  Stephen Collings Jul 31 at 13:21
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It's usually pretty tough unless you're sloppy or have sharp edges. One thing to consider is whether you want solder-through insulation or something that has to be removed with an abrasive (or chemical) stripper. –  Spehro Pefhany Jul 31 at 13:58
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One note is that if it's a static sculpture, it's more likely to work than if it's a kinetic sculpture as magnet wire is not well suited to repeated bending. –  Edward Jul 31 at 14:03
    
I'd expect it to probably work most times with few LEDs and start to get problematic when you got to hundreds of LEDs and tens of metres of frame. –  Russell McMahon Jul 31 at 16:14
    
Jeeze, usually my biggest problem is getting the dadburned insulation off of the stuff in the first place! Likely that will be the biggest frustration of your project - you will need to apply heat/solder to the mag wire to melt off that insulation before soldering it to the LEDs –  Nick Jul 31 at 20:28

3 Answers 3

There are two wire types that are ideal for your application. The first and best is called "heavy formvar" and is the type of wire that is used in the automatic winding machines that make motor stators and armature windings. This wire is available from many suppliers and costs around $50 a pound for #20 and up to $150 a pound for #44. (smaller diameters are much more expensive) The second choice would be "polytheremaleze" which is also a very durable wire that is used in high temperature applications. It has a nylon coating for insulation. (think of how tough a tywrap is!) This wire is also widely available from many manufacturers and distributors. (google magnet wire) It is approximately the same cost as formvar. Another possibility is to use a wire called "ltiz" wire, which is made up of multiple strands of fine wire. This is substantially more flexible before breaking than a solid wire of the same gauge. Litz wire is available with both formvar and polythermaleze insulation, as well as "soldereze" insulation, which is MUCH easier to use because it disintegrates at the temperature of hot solder. Thus you can solder it without having to strip it first. Stripping the end of a wire is a serious problem with formvar and polythermaleze because of their toughness.

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That's great -- thanks. Is the "soldereze" insulation tough enough to withstand two adjacent wires rubbing together (perhaps dozens of times, not hundreds of times)? I can keep sharp objects away from the wire, but I need to wrap the magnet wire onto the frame and then bend the frame a few times. –  Kevin Walker Jul 31 at 18:52
    
Litz wire is a total waste of money if all you're doing is passing DC (or 60 Hz) through it. –  Nick T Dec 12 at 23:18

There are all sorts of magnet wire. Cheap stuff from radio shack will scratch off easily. If you go to a wire supplier (MWS?) you can get triple (or maybe even quadruple?) layers. And lots of different materials.

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Thanks. Do you know how much abrasion the multi-layer insulation can withstand? –  Kevin Walker Jul 31 at 13:21
    
You might try the MWS website. I've got a catalog.. reading the insulation characteristics it says, "Polyurethane Nylon 180 offers excellent abrasion resistance for ferrite coils and transformers...." –  George Herold Jul 31 at 13:25
    
Looks like there's a lot of good information at the MWS site -- thanks. –  Kevin Walker Jul 31 at 13:30

It all depends on what insulation is used. There are lots of different kinds of insulation and manufacturers make them with different thicknesses (single build, double build, triple build, etc.). Most data sheets show the results of an scrape abrasion test. In this test, a sample of the magnet wire is secured firmly in place and a needle is scraped along the surface of the magnet wire. The datasheet usually records the number of scrapes the insulation can withstand until the needle breaks through the insulation and shorts the wire.

So that spec on the data sheets will give you a good relative feel for how different magnet wire types compare to each other. But it doesn't really answer your question of how well magnet wire will work for what you are doing. Here are a couple of thoughts. I think you'd be surprised how tough a good quality magnet wire can be. A popular type in the motor industry is a heavy build MW-35. It holds up pretty well and should be able to withstand being assembled. Just try not to use any sharp/pointed tools that could scrape or puncture the insulation. Also keep in mind that for many, many magnet wire applications like motors and transformers, the magnet wire gets coated with a varnish or epoxy to give it more long term protection against rubbing, vibration, etc. That doesn't mean your application would need varnish but magnet wire is very often used that way.

I think if you pick a good quality magnet wire and are careful not to nick or scrape it during assembly, you should be okay.

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Very helpful -- thanks. –  Kevin Walker Jul 31 at 13:41

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