This is a project from a long time ago. I thought it would be cool and make me the hit of the parties to have an LED hat that lights up and did cool animation things for a dance. Turns out the hat won’t help meeting people as much as I thought. None the less, it was a big hit during halloween.
I made two versions of the hat. The first has 8 vertical rows of LEDs and 5 LEDs tall. It was basic and could only display simple patterns. The electronics are a atTiny and two shift registers. One is a constant current driver for the columns. The other shift register does not have a latch. For this number of LEDs it was fine, as there was only very minor ghosting. The two buttons control the different functions. It can scroll left to right and then left to right. It also has an up and down function.
After I made this hat, my friend wanted to make a bigger and better one with me. The goal of this one was to display text and more complicated functions. The hat is 24 columns around and 8 rows tall. It is powered by a 4 AAA battery pack, an Arduino Pro Mini, and two 74HC595 shift registers. These shift registers have storage register which allows for the data to be sent to all the registers and then latched to the display all at once. There is almost no ghosting with this method of output.
We were really interesting in displaying text on it; while text can kinda be read it is hard to read at any but the perfect angles. This is due to the small size of the LEDs, the large spacing between them, and the non-diffused LEDs. If the LEDs were 5mm it would be a lot easier to see the dots. Sense the LEDs are not diffused they can not be seen very well from all angles. Add to these problems the large amount of blank space the hats more detailed functions are not as cool looking.
Doing this hat again I would double the number of rows of LEDs and use 5mm diffused LEDs. closer spacing would make soldering easier because the legs of the LEDs were not quite long enough to reach the next LED. I’ve seen hats that take strips of led and wrap those around to make good displays. Another idea I had was to put LED panels, such as these or the like of, around the hat. With all those colors I would want something faster than the Arduino Pro Mini.