This one has been around but it’s too cool.
Cool LED Shirt you can make yourself!
1. Pick a garment to sew on, a pattern that will let you sew your own garment, or design your own pattern.
2. Design your display. decide on the number of LEDs you want and their general placement. This will depend on the garment you chose and the microcontroller you intend to use as well as how you’d like the display to look. I decided to sew a simple tank top and I chose to place the LEDs evenly across my tank top every 2″. Since my tank top is approximately 28″ around and 12″ tall I needed 84 LEDs. (Note! The pictures here show a different shirt with 140 LEDs spaced 1″ apart.)
3. Decide on the microcontroller you want to use. Choose one with an internal oscillator, and make sure you have enough i/o pins to control your matrix. It’s a good idea to pick a microcontroller you are familiar with and read the data sheet carefully! It can take some reading to discover that what you thought was a general purpose I/O pin is input only or an open drain output.
4. Decide on the power-source you want to use.