I’ve often seen these being made by other hobbyists and wanted to make one myself.
However my first attempt ended in disaster when I misread the resister value and ended up breaking a bunch of LEDs and didn’t want to go through the hassle of soldering them again.
A year later, I decided to make one for my girlfriend, that she could program with some software I would write.
This time I bought plenty of extra LEDs, and use my multimeter on my resisters first just to be extra sure.
With four rows completed, now the complicated task for soldering them together.
Each time I soldered a new row I tested the LEDs to be sure they were still functional, and that no short circuits had occurred.
With all the rows completed and working, I began working on the firmware for the microcontroller that would control that LEDs. It was simple enough to write and after tweaking the wait times, I managed to create pulse width modulation (the PIC chip I was using doesn’t support it in the way I’m using it).
I managed to get the PIC chip communicating with my laptop over USB, and here is a video of it working.
All I need to do now is write the software.