If you are into electronics, I bet you've seen a lot of badges with LCDs, OLED display, LEDs and so on. AmalMathew
posted on Instructrables his work on an LED dor matrix badge. As he says on the tutorial post:
"Are you running an event ,competition or even hosting a birthday party ? Badges are versatile item that can make introductions and celebrations that much easier .You would never begin a conversation with "hello , my name is ............." so why should your badge?"
In this project, he will show us how he built a badge-sized ATtiny85-based LED matrix display (5x4 matrix). He used Charliplexing technique for driving 20 LEDs using ATtiny85.