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Prototyping: Copper Pendant Fixture


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General Lighting or Task Lighting?
There are multiple different types of lighting fixtures, most of which are better or worse at solving particular lighting problems.  Linear fixtures, either mounted directly in a ceiling or hanging down within a space, are a good way of providing general lighting.  Point-source fixtures, again mounted directly in a ceiling (like recessed lighting) or hanging down within a space (pendants), do a better job of spotlighting specific areas, items, or work surfaces.  So, linear fixtures are great in Walmart; point-source makes more sense for desk lighting.  I would not like to have my desk in a Walmart for many, many reasons, but for one, the lighting would be terrible.  So this will be a pendant fixture.
Materials
I'm planning some different ideas for these fixtures.  I don't want to have a bulb of any kind; instead, I'd like the entire fixture to glow.  So I'll be using LEDs inside copper tubing to spread the light out a bit instead of having it focused in the center of the fixture.  There are a number of different kinds of LEDs on the market; I'll be using these LED strip lights  to do the job.  They're flexible and easy to use.  Those are just the LEDs, though; I'll also need a way to power them.  LEDs are powered by power supplies which convert household power to the low-voltage direct current needed.
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First Steps: Slit Tubing
The design calls for the LEDs to sit inside the copper tube, with a slit cut in the tube to allow light to exit.  This is a trickier proposition than it might seem -- cutting a straight line in a tube isn't easy.  So here's the plan: I'll build a jig, which is a fixture that holds the workpiece steady to let me cut it correctly.  Jigs make fabrication quicker, more accurate, and (usually) safer.  
 
The classic jig for working with tubing is based on a vee.  The crux of the vee holds the tubing straight and in position.  I'll be running the tubing through a table saw -- more on that in a second -- so I'll also need some way to keep the tube from rotating while it goes through.  Here's the solution: a backing piece of wood, roughly as wide as the saw kerf (a "kerf" is the width of the cut), which will slot into the cut in order to keep the tubing straight as it runs through the jig.
 
Now, the table saw.  It's not a classic metalworking tool for a lot of different reasons, but it works here because most nonferrous metals like copper and aluminum can be cut fairly readily with carbide blades.  I won't be using my $100 Forrest blade, though; a cheapie will do the trick.  Disclaimer: using a table saw is dangerous, and this is a particularly dangerous way to use a table saw.  I recommend that you leave this to people with experience and insurance.
 
First Steps: Slit Tubing
Building the Jig
The jig itself is simple: a plywood base with a groove cut for alignment and to hold the piece of wood which will notch into the cut tubing; a piece of lumber ripped on a 45 degree angle into two pieces to form the vee; and some miscellanous scrap to allow the whole thing to be aligned on the table and clamped securely into place.
The Cut
With that done, the tubing can be buzzed through the jig.  Aside from the blizzard of hot shards of copper splintering into my face and arms -- a common hazard of metalworking with woodworking tools, and just one of the reasons why safety goggles are an imperative for table saw work -- it cut quickly and easily.  The cut is rough on the edges because the thin copper tends to hook a bit at the location of the cut, but that's easily cleaned up with a bit of sandpaper.  A pair of tweezers or needlenose pliers can pull strips of swarf (strips of waste metal from cutting) out of the tube as well.
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Lighting It
The easy part: setting the LEDs in place for this test is as simple as pulling the flexible strip through with pliers.  After connecting the leads soldered onto the end of the strip, the tube is an operational fixture.  
 
Obviously, this is pretty rough.  It's a proof-of-concept, a way for me to make sure that this looks the way I think it will and to examine potential problems with the part of the fabrication process.  The next steps will involve bending the tubing into the shapes needed for the fixture itself and securing the tubes together.  Check back for part two, which will take us the rest of the way.