Intro: EL Wire T-shirt With Music Beat Detection
In this tutorial I explain how to build an EL-wire decoration to put under a T-shirt and how to drive it with electronics to make it move in beat with ambiant music.
This is the ultimate wearable decoration to wear in electronic music festivals or clubs.
The idea is to hide felt panels under a t-shirt and drive the lights using a microcontroller that analyzes ambiant music with a microphone.
For this project, you will need :
-two simple white T-shirts
Depending on the length of EL-wire we need, we have to choose between two power inverters. If I had used less than 3 meters of wire, I would have chosen a 3V inverter. As I planned to use more, I chose a 12V inverter.
-so a 12V inverter
-12V batteries, I chose 8 NiMH AA type batteries of 1.2V each. It’s not exactly 12V but it’s sufficient.
-some electronics (EL Sequencer with an integrated microcontroller to analyse the microphone and drive the lights
-a microphone (mine is cool, it has automatic gain)
-a small switch
-felt sheets approximately the color of the T-shirt to be able to sew logos on it (the T-shirt would not be resistant enough.
I needed also small supplies, solder iron, tools, wood,…
Step 1: Draw Your Shapes and Solder the EL-wire
First you need to have an idea of the shapes you want to have with your EL-wire. Then you approximately select the length of wire you need and cut it (with some more length just in case)
EL-wire comes without electrical connexions and can be cut where you want. But each time you cut it, you have to connect it to the power source. That’s one of the hardest part of the project, you have to denude very small wire, solder them without breaking them, put shrink tubing around them to secure them,… I won’t get into details, someone explains it better than me. Actually I have red different tutorials here on Instructables to make my own procedure to solder EL-Wire.
Now you should have EL-wire strips with electrical connexions. You can check them by connecting the cables to the inverter and see if it glows.
Step 2: Sew the EL-wire on the Felt
I drew my pattern on the felt and then sewed it to give the shape to the wire. I made holes to pass the wire at the beginning and at the end. As the EL-wire is very hard to solder, I tried to minimize th number of times I cut it. I also simplified the patters I wanted to draw.
Another idea is to hide the wire behind the felt in the places you want to hide it. As an example, on my smiley, I used one segment to make both eyes. If there’s a corner or a sharp edge to draw, make a hole in the felt, and do the turn behind the felt before going out of the hole in another direction.
Step 3: Connect the Electronics
When the wire is connected, you can plug it on an output port of the EL-Sequencer. There are nice male plugs on the board but I haven’t any corresponding female lying around so I made myself connectors on the board. You can also solder the wires directly on the board.
The battery connector goes on DC IN, the inverter goes on DC OUT and AC IN. I put a plug on DC IN to be able to turn everything off easily. If everything is well done we can power it on and with the default program loaded on the microcontroller the wire should blink.
You can connect the microphone OUT to the pin A2 of the microcontroller, also Vdd to 5V and the ground of the microphone on a ground pin.
Step 4: Program It
Get the bass from the microphone
In many engineering domains, analyzing frequencies is very important. It’s often achieved by applying the Fourier Transform Theory. It’s very powerful but the mathematical description of it need integrals, complex calculus and only works for perfect signals. I’m in the real world, and my microcontroller doesn’t know how to evaluate complex integrals. Hopefully, there’s an applied version of this theory called Fast Fourier Transform (FFT) that is a very well known method to do an analysis like that with a computer. Still, it requires some calculating power that my microcontroller doesn’t have. I found another algorythm called the Fast Hartley Transform (FHT) that is simple to use and works well too.
I copied the example code of the library I found and began playing with it to make the lights blink according to the levels of certain frequencies and I was done. I tested it at home, it worked well. Oh, wait, what if in a loud music environment it doens’t work ? Let’s find a plan B.
Surviving in the real world
So as I will use this in an environment with loud music, crowd, drunk people pushing everywhere,… i need to make my T-shirt (and the electronics inside) solid enough.
As I was not entirely sure the microphone would work in very loud music environment I programmed a plan B on the microcontroller using a switch. With that switch I can run the T-shirt in a sequence mode with random patterns. Otherwise it runs in sound mode. It turned out that even if sometimes the microphone was saturated, overall it worked well all the evening. The electronics is put into a small wood box to protect it from impacts. All the wire soldered on the board are hot glued around the solder point to reduce damages on them. Everything is placed in a small bag at the belt in front of me under the T-shirt.
You can use the attached source code on your setup and play with it.
Step 5: Test It and Have Fun
Here is a demonstration of the audio feature :