Introduction: Industrial Style Display Lighting

By The Vecino Group
About: Professional Engineer with The Vecino Group.

Following how well my lighted pipe-supported shelves turned out, I wanted to do a similar style light fixture for lighting album artwork on my office wall. But this time I wanted flexible arms holding spotlights that could be more easily aimed.

That previous job used all 1/2" steel pipe. This time I wanted the arms holding the light bulbs to be copper tubing for a more delicate look and flexibility. Feeding wire and making connections inside 1/2" pipe had been difficult and I knew I'd have to do it differently with the thinner copper tubing, so decided to use 12V power and separate wire runs from each bulb back to a transformer. Separate runs meant I wouldn't have to make connections inside the pipes of more than two wires needing wire nuts. With only two wires, I could use splice connectors that could fit inside the copper tubing. And with low voltage, I could use wire with thinner insulation, allowing several runs of wire to easily fit in the 1/2" pipe.

Total parts cost was about $130.

Step 1: Parts & Tools

Parts:

For my design, I wanted three bulbs at about 24" spacing, but also chose to stick with regular stock items instead of bothering to get pipe custom cut, so the spacing turned out more like about 26".

Parts available off-the-shelf at Lowes and Home Depot (~ $80):

Online parts (~ $50):

Tools:

  • Wrenches to tighten the connectors
  • tube cutter or hacksaw to cut the copper tube
  • screwdriver
  • drill and bits
  • electrical tape
  • wire crimper or narrow pliers to crimp the wire connectors
  • wire cutters
  • Something rigid, about 4" diameter, to use as a bending form
  • 24" of RG6U quad shield coax cable (optional but recommended)
  • TSP, Trisodium Phosphate detergent powder (Lowes carries it.)
  • Spray paint

* As an alternative, you might consider doing the three tees that the copper tubes connect to in brass (also available at Lowes). They're triple the price of black iron tees, but it might look pretty cool.

Step 2: Cut and Bend the Copper Tube

Cutting:

I found a heavy cardboard tube to use as a bending form that was about 4" diameter (2" radius). The formula for finding the length of an arc is πAr/180 where (A) is the angle of arc, (r) is the radius, and if your calculator doesn't have a π button, just use 3.14. So for a 180 degree bend like I want, it's just π*radius. For my 2" radius, the bend length would be 6.3". I chose to cut my tubing to 12" lengths which would leave about 3" straight at each end.

Tube cutters always crimp the opening closed a bit and you'll need to ream it back out to full size or the wires won't fit. If you don't have a reaming tool, you'll have to improvise. I used a screwdriver that had a tapered head, twisting it around and around as I pushed it into the opening until it was back to full size.

Bending:

I suspected bending the tube without crimping it might be tricky, so I watched a few videos to learn how to do it. The idea is to fill the pipe with something that will prevent it from crimping or flattening into an oval shape as it bends. A tool called a bending spring that slides inside the pipe is available, or there were videos of people using ice, salt, and sand.

My bends were made using ice (water filled and frozen solid before bending) with so-so results. It melted very quickly and still left me with some small crimps and a little flattening. After my fixture was finished and mounted, I had what I thought might be a better idea for bending, and did some experiments with my leftover tubing using coax cable pushed through the tubing. It worked better and if I were doing more of these, it's definitely how I'd do it.

Coax Cable Method:

The inside of 3/8" OD tubing is about 0.3". RG6/U quad shield coax cable is 0.29" and fits nicely inside the tubing. Lowes cut me 2 feet for less than $1. With the cable pushed through the tubing, I was able to bend the tube around my 4" form with no crimping at all. The tube flattened a bit, but not so much that I don't think the wires would fit through. With a vice, I was able to easily squeeze it back to round.

Step 3: Add Copper Tube End Fittings

The compression fittings I got at Lowes have a captive sleeve inside them and work a little different than a traditional compression fitting. You're supposed to screw the nut onto the fitting finger tight and push it as far as it will go onto the end of the tube, then tighten 1/2 turn with a wrench. Do this for a female fitting at one end, and a male fitting at the other for each copper pipe.

Step 4: Lamp and Wire Connections

My parts list shows using red and black wire, but you'll see from my pictures that I used white and black. That's because I bought my wire before the LED driver had arrived and I didn't know it would have terminals marked red and black. For simplicity, you may as well stick with it's colors when you build this. However, to keep my instructions matching the pictures, I'll refer to white(red) wires. The wire I got is 16 gauge, which various sources indicate is safe for under 10A. The maximum I'm running is 15 watts or 15W ÷ 12V = 1.25 amps.

Cut two pieces of primary wire for each bulb and of each color, long enough to reach from the bulb through the pipe, into the ceiling, plus an an extra foot or so, so you have enough to work with above the ceiling. To keep track of wire pairs, I taped them together about every 12".

With a 12" copper tube and 12" legs on the sockets, the connectors will be inside the copper tube. The tube isn't big enough for two connectors side-by-side, so cut one leg of each bulb socket 2" shorter than the other to stagger them. Strip 1/4" off all wire ends and push one socket leg and black wire into opposite ends of a connector, and squeeze at each end with your pliers to make a crimp that holds the wires firmly. Repeat for the other leg and white(red) wire. I use a tool that is a combo wire cutter, stripper, and crimper, like this one.

*** All of the electrical connections in the secondary circuit of a low voltage lighting system must be very tight and secure. If an electrical splice is not very tight and secure, the wires may arc, create a great deal of heat, cause the entire lighting system to fail, and possibly become a fire hazard. ***

Thread the wire pair into the tube and pull it through until the socket fits into the female threaded fitting. The lamp base needs to fit snugly, so wrap it with a couple of layers of electrical tape or glue it in place. I tend to build things so they can be disassembled, so mine aren't glued.

Step 5: Prep the Steel Pipe

New black iron pipe and fittings are always filthy because they have an oil coating to keep them from rusting in damp warehouses. Before painting them or even handling them much, you'll want to wash them. Dishwashing liquid will work in a pinch, but 1/2 cup of TSP (Trisodium Phosphate) in 2 gallons of water and a little scrubbing works really well. Wear rubber gloves to protect your hands. The long pieces have a black paint-like coating that the TSP and scrubber will also remove. Be careful of sharp edges and protect your eyes and clothes from splashes of oily black water.

Once the pipe is clean and dry, give all the pieces a coat of paint. I went for a contempo-industrial look, so just used a coat of Krylon flat black. For a distressed look, you might want to look at these videos by Lowes.

Step 6: Final Assembly

Connect each copper tube assembly to a tee, paying attention to which direction the wires need to go, and lay out everything in it's correct place. From left to right, I put mine together like this.

  1. end cap
  2. 3" pipe
  3. tee with copper tube
  4. 24" pipe
  5. tee with copper tube
  6. 4" pipe
  7. tee with 3" pipe and flange (don't assemble until the very end)
  8. 18" pipe
  9. tee with copper tube
  10. 3" pipe
  11. end cap

I recommend assembling pieces 1 through 6 in that order. Then run those two sets of wires straight through the #7 tee and connect the tee. Running them straight through keeps them from getting twisted as you screw 7 onto 6. After 7 is tight to 6, fix the wires so they turn correctly through 7. They're limber enough that it isn't difficult.

Then start at 11 and work your way back to 8. Feed that single set of wires correctly through 7 and screw the 8-11 assembly to 7. That single set of wires will twist, but better one pair twisted than two. Finish connecting the 3" hanger pipe and mounting flange. I felt like I was able to screw everything together by hand, tightly enough that it wasn't going to come undone by itself.

At the end, you should have three pairs of wires coming through the flange.

Step 7: Mount and Connect to Power

Mounting:

Locate where you need the mounting plate to go and drill a hole through the ceiling at the center for the wires. If you have a drywall ceiling you'll want to reinforce the ceiling so the 4 mounting screws have something firm to go into. A piece of 2x4 blocking nailed flat between adjacent joists would work well. Use your own judgement on how to mount it to your ceiling firmly enough that it won't fall. I didn't think to weigh it, but the pipe weighs 0.85 lbs/ft, so it's only going to be around 6-7 lbs maybe. Since you're working over your head, eye protection is a good idea.

Wiring:

As this was my first time using a LED driver, I did a bench test when it arrived to make sure it worked with a bulb as expected and was relieved that it did. It came with no installation instructions, but I felt it would be smart to mount it in a place where it wouldn't get covered by insulation and potentially overheat.

*** All of the electrical connections in the secondary circuit of a low voltage lighting system must be very tight and secure. If an electrical splice is not very tight and secure, the wires may arc, create a great deal of heat, cause the entire lighting system to fail, and possibly become a fire hazard. ***

Bundle the three black fixture wires together and connect a fourth black 16 gauge wire. Do the same for the other set. Use orange wire nuts because they can fit four 16 gauge wires. The output terminals of the driver were labeled red(V+) and black(V-). Connect your wires accordingly (although actually for bi-pin bulbs like this it doesn't make a difference.)

I'm not going to get into how to hook up the 120V input side of the driver. If you have experience with electricity you'll know how to connect everything, and if you don't, get help from an electrician or someone experienced. There's the whole burning down the house or electrocution thing to consider.

Turn on the power, and gently adjust the copper tubes to aim the lights.


* A note on drivers vs transformers

Beginning this project, I assumed I'd use 12V AC LED bulbs and a 120V to 12V AC transformer, but as I shopped, I abandoned that idea in favor of DC power and a LED driver. What I learned was that AC transformers are generally for halogen lamps and higher wattages, with dimming capacity limitations. In fact, one of the smallest transformers I found had a 60 watt maximum and 10 watt minimum load, but with a dimmer it listed a 20 watt minimum load. The total load for my three LED bulbs is only 15 watts, so I suspect they may not have worked at all if I ever decided to use a dimmer. And if it did, it would probably flicker.

LED drivers come in lower wattages and can convert 120V AC to 12V DC. The one I used lists 26 watts maximum and can dim to 5% (1.3W). The only catch to using such a driver is that the bulbs MUST be designed to work on a DC circuit, and it seems like the typical LED MR16 is designed to be a replacement for AC halogen bulbs. Be careful when you make your purchase that you find ones that work on DC power. The ones I link to are capable of being used with AC or DC power, and are dimmable.