Introduction: Musically Animated Gift Box
Click here if you want to jump to the demonstration page where you can see other videos.
Most EL wire displays are static (and boring) because they use constant-on inverters. Of course, there are inverters that can flash the EL wire on and off at a fixed rate, but that's not very exciting. Another option is to use a sound activated inverter, but most of these are single channel, so they turn the wires (no matter how many colors you have) all on or all off. If you really want to make your EL projects lively you have to use an inverter with multiple output channels, but many of these cost $80 and up! Luckily, I've found that you can use an inverter taken from a "graphic equalizer" T-shirt (aka T-qualizer) to create an inexpensive five channel, sound activated EL wire display.
I've used this idea to create a musically animated gift box from EL wire, a T-qualizer inverter, portable speakers, and an MP3 player. I call this gift box an ELF box which is short for ElectroLuminescent Fun box. The ELF box is a very cool way to give someone an electronic device that plays music; just substitute it in place of the mp3 player and have the gift animate its own gift box! Of course, if you don't want to make a gift box, this instructable works equally well for making a musically driven display. Finally, an optional step gives instructions on how to modify the inverter so that it responds to an audio signal instead of sound, which will enable you to precisely control the animation with a custom audio file and make speakers unnecessary.
Materials and Tools
gift box or other suitable substrate
5 strands of EL wire (I used 20 ft for an 8x11 in box. metric: ~6.1 m for a box approx. sized 21x28 cm)
T-qualizer inverter (not exactly the same as the one I have, but similar)
7x1 ribbon cable (around 6 in or 15 cm)
7x1 crimp terminal housing
7 female crimp terminals
crimper or pliers with knurled jaws
medium phillips screwdriver (for poking holes)
knife (for removing phosphor)
Step 1: Attaching the EL Wire
There are many varieties of musically sensitive EL panel T-shirts. The one I have looks like a graphic equalizer display with five different levels. Since the T-qualizer is meant to display levels, the line which drives the lowest level (quiet music) will stay on more often than the line driving the highest level (loud music). For the remainder of the article I will use line and level mostly interchangeably. You should keep in mind how often a line stays on compared to the other lines when choosing which color to assign to a line. For example, if you are you want your display to be a Christmas tree with flashing ornaments then you should put the color that will outline the tree on the lowest level because it will remain the most static. I chose to use five different colors of EL wire. There is no reason why you can't use fewer colors, but every line need an EL wire connected.
To connect the EL wire to the inverter I simply copied the same type of connector used by the inverter. 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 grouped 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 display without wasting EL wire to cover the distance from the shared common to the desired location. I'm using the shared common approach because I'll be reusing the wires and inverter in another project where the shared common is preferrable. 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. The outer wires of the ribbon cable are soldered to the corona wires which are further back than the core wires. Therefore you should make the outer wires of the ribbon cable longer so they will reach. 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 termination to insulate the corona wires/common and core wires. This made a nice, rigid connection that I'll need when I reuse the EL wire in another project. You may want to use a large piece of heat shrink to insulate the connection while preserving more flexibility than you'd 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 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.
Step 2: Modifying the Inverter (optional)
This step is optional. It demonstrates how to modify the inverter so that it responds to an audio signal instead of sound waves. A ELF box should work fine without modifying the inverter as long as you place the inverter's microphone close enough to a speaker.
Materials and Tools for this step
220 ohm resistor
3.5 mm stereo cable with a male connector (cut a cheap loopback cable in half)
3.5 mm stereo splitter
small phillips screwdriver (for disassembling the inverter)
xacto knife (for cutting traces)
Before trying this mod you should see if an earbud placed over the inverter's microphone works well enough for your needs. My music player had to be unacceptably loud to get the inverter to respond to an earbud.
The T-qualizer inverter uses an electret microphone to sense sound and drives five lines connected to an EL panel made to look like a graphic equalizer. The number of lines it drives depends on the amplitude of the sound sensed. The inverter drives the lines additively which means if line three is being driven then lines two and one must also be driven. The first and last wires of the ribbon cable are both connected to common and the connector is not keyed, so it is possible to reverse the order in which the panel's colors light up. This section will explain how to modify the inverter so that is responds to an audio signal instead of sound.
A modded inverter has a couple of advantages. First, it allows the inverter to be triggered by a remote source via a headphone extension cable. Note that the audio source doesn't have to be outputting sound through a speaker for the inverter to work. Second, a custom waveform that steps its amplitude up or down can be used to precisely control which levels the inverter lights up. So you can use a specially-made audio file instead of music to animate the EL wire display.
I've only worked with one of these inverters, so I can't say how likely you are to have one just like mine. I'm hoping that these modifications are generic enough that you will be able to apply them to a different inverter. First I removed the screws holding the inverter's case together and inspected the circuit board. The sensitivity pot feeds power to the electret microphone's internal amp. The output of electret mic is then capacitively coupled to an inverting single transistor (M28S) amplifier. The output of the transistor is capacitively coupled to the EL driver IC. To make room for the audio cable I removed the barrel power socket. Mouseover the image notes to see the places on the board I'm describing.
Next I desoldered the electret microphone and cut the trace connecting the potentiometer (thumbwheel) to the IC's power pin. Doing this let me directly input an audio signal into the circuit. I had some success capacitively coupling an audio signal onto the microphone's output trace before making any modifications, but it didn't work quite right.
I found that the dynamics of the panel covered its full range nicely when the audio signal input was at a listening level that is slightly below normal. This means that if the volume was increased to a normal or loud listening level that the panel would be pinned to the red most of the time. Therefore I decided to reuse the potentiometer to attenuate the audio signal before it is input to the inverting transistor amplifier. To do this I cut the trace connecting the upper and middle legs of the pot and connected the left audio channel's wire to the upper leg and audio ground to the circuit board's ground. Now the thumbwheel allows control of the driver's dynamic range without having to change the listening volume of the music. My 2nd generation ipod shuffle has a noisy output, so it causes the lower level EL wires to light up even when music isn't playing. Using the thumbwheel to increase the input resistance fixes this problem.
Unfortunately, these modifications make the inverter susceptible to noise picked up by the audio cable. To fix this I used a 220 ohm resistor. I soldered the first leg to the audio line where it joins the thumbwheel and the second leg to where the negative battery terminal meets the PCB. Normally the barrel connector socket bridges the PCB's negative battery terminal pad to ground but since I removed it I used the remainder of the resistor's leg to connect them.
Step 3: Decorating the ELF Box
I'm not particularly artistic and this is my first EL wire project so I practiced a few designs on pieces of scrap cardboard before decorating the gift box. Practicing is a good way to get a feel for what sorts of designs look good and which techniques work well. I settled on a rather simplistic method for decorating my gift box. I just punched holes in the cardboard and threaded the EL wire through them to make a pattern. I'm certain there are other methods that would produce better looking results, such as using glue or sewing thread, but I wanted to make it easy to remove the EL wire so I could use it in another project. I was still quite happy with the way my box turned out. Note that EL wire is available in different thicknesses, with thinner wire being better for more intricate designs.
First, I sketched the pattern I wanted to outline with EL wire on the inside of the box. This is so the sketch doesn't show on the outside. However, placing the sketch inside the box means the pattern displayed by the EL wire will be flipped horizontally compared to the sketch. This can make it difficult to draw letters by hand since the text needs to be reversed. To overcome this problem you can use a bold sharpie to draw the pattern on a piece of paper as you want it to be shown by the EL wire, then simply flip the paper over before taping it to the inside of the box. You should still be able to see the pattern on the opposite side of the paper. Using a computer to design, flip, and print the pattern also works well.
Since the lower levels will be on more often than the higher levels, it is best to use the lower levels for the more fixed parts of the display. For example, if you want a Christmas tree with ornaments it makes more sense to use the lowest level EL wire to draw the tree and higher levels for the ornaments, because a display with fixed ornaments surrounded by a disappearing tree would look strange.
Next, I picked places along the pattern to punch holes for the EL wire to be threaded through. This step takes some thought because it's necessary to determine where along the pattern the EL wire will be outside or inside the box. Of course, when the EL wire is inside the box it can't be seen so it might disrupt the pattern. Where to punch holes is something you get a feel for with practice. I found the best tool for punching holes was a phillips screwdriver because it could be used to drill through the cardboard without having to worry about a sharp point. If you find a part of your pattern requires you to place holes too close together, consider using black electrical tape to block out part of the wire. For example, the dot at the bottom of an exclamation mark is difficult to make by threading wire through punched holes, but a bit of black electrical tape works very well to block out a bit of wire and create the space between the "bat" from the "ball".
Step 4: Demonstration
There are many ways you can use the ElectroLuminescent Fun box. You could use it to enhance the presentation of an ordinary gift and simply ask that the ELF box be returned. "Ta Da! Socks!" You could gift a particular component of the ELF box such as the portable speakers, mp3 player, or a smart phone (which could serve as both the speaker and mp3 player). However you could give the ELF box as part of the overall gift and the recipient could reuse it as a holiday display or to give a gift to someone else. You don't even have to give it to anyone; you could simply use it as your own festive display.
Here are a few videos of a couple ELF boxes in action.
If you modified your inverter to respond to an audio signal instead of sound waves, then you can control your display in an interesting way. A modified inverter doesn't need music to work correctly. It responds to the amplitude of the signal, so it will even work with white noise. A custom audio waveform that steps its amplitude up and down can be used to instruct the inverter to turn on a particular level (and all the levels below it). This means you can use an mp3 player instead of a microcontroller to precisely control the EL display! Since the modified inverter only uses the left audio channel, you can still use the mp3 player to play music by making an audio file with the control audio in the left channel and the music in the right channel, and utilizing a splitter that separates the left and right channels.
Here's a video demonstrating precision control with an example display that says "PLEASE VOTE FOR ME! THANKS!". Each word is a different output level. Unfortunately, since lighting a particular level also lights all the levels below it, the sorts of animations you can create with a display driven by a T-qualizer inverter is limited. I put the white noise audio signal in the video for demonstration purposes, but it's not necessary for the audio signal to be converted to sound to make the modified inverter work.
While I was testing out a custom, precision control waveform on the graphical equalizer panel I noticed that driving different lines produced distinct pitches of inverter whine (i.e. the magnetostriction noise). This has me wondering if it would be possible to play simple tunes with inverter noise. I'll try to put up a video of the different pitches of whine so that those that more musically knowledgable than me can let us know if this is possible. My camera's microphone is absolutely miserable though.
We have a be nice policy.
Please be positive and constructive.