This instructable will show you how to decorate a pair of headphones with electroluminescent wires (EL wire) that react to the music. This project uses over the ear headphones, EL wire, an inverter taken from a T-shirt EL panel graphical equalizer display (T-qualizer knock-off), and an mp3 player. I call this project "Level Headed" because it dynamically displays the levels of the audio you're listening to on your headphones.
Materials and Tools
over the ear headphones
5 strands of EL wire
7x1 ribbon cable
7x1 crimp terminal housing
21 female crimp terminals (order extra in case you mess up)
220 ohm resistor
3.5 mm stereo cable with a male connector (cut a cheap loopback cable in half)
3.5 mm stereo splitter
clear heatshrink tubing
crimper or pliers with knurled jaws
knife (for removing phosphor)
xacto knife (for cutting PCB traces)
small phillips screwdriver (for disassembling the inverter)
Step 1: ATTACHING THE EL WIRE
To connect the EL wire to the inverter I simply copied the same type of connector used by the EL panel. This connector uses ribbon cable with female crimp terminals in a 7x1 housing. The downside to this approach is that all of the EL wires have to be together where they meet the ribbon cable so that the corona wires can share the common connection. If each EL wire had an individual common connection then the ribbon cable could be split and the EL wires separated. This would allow two EL wires to be used on opposite ends of the project without wasting EL wire to cover the distance from the shared common to the desired location. Since the EL wires will be grouped together in my headphone decorations the shared common is preferable. If you'd like to use the individual common technique then you'll need to rewire the inverter with a ribbon cable that has ten lines, with common connected to every other line.
My EL wire came pre-stripped, but I did have to scrap the phosphor off the core wire. The picture above shows a razor blade, but I think a regular pocket knife works better for removing the phosphor. Here's a link to a tutorial on EL wire which includes instructions on how to properly strip it. Please read it if you aren't familiar with how to work with EL wire. The main takeaway is to be careful not to cut the corona wires when removing the insulation and to run the inverter only when the EL wires are connected. I used electrical tape to isolate the core wires once they were soldered to the ribbon cable. You will probably have an easier time with heat shrink tubing. Then I hot-glued the soldering to insulate the corona wires/common and core wires. This made a nice, rigid connection. You may want to use a large piece of heat shrink to insulate the connection while preserving more flexibility than you get from hot glue.
To construct the connector, first examine a single female crimp terminal. The set of tabs at the edge are meant to wrap around the wire's insulation. The other set of tabs near the middle are meant to contact bare wire. Insert one strand of ribbon cable in to the connector to determine how much insulation you should remove. Remove that much insulation. Reinsert the wire and line it up so that the tabs will grab the proper part of the wire when they are crimped. Normally a crimping tool is used to press down the tabs but you can use pliers with knurled jaws to do the same thing. Here's a link to a very detailed article explaining how to attach female crimp-on terminals. Once all the terminals have been attached you can insert them in the housing. The terminals have a metal catch that springs out when it reaches the hole on the side of the housing. Therefore you should make sure all the terminals are facing the same way, that you insert them into the housing the proper way, and that you insert them far enough. Wrap some electrical tape around the housing to insulate any exposed metal since EL wire is driven by high voltage that can shock you.