If you always have the intention to build a fantastic 4×4 LED Matrix, then you might want to check out this Crossbar!
Well, this Crossbar is a very easy project, especially for those who involving with LED Matrix frequently. The Crossbar is based on a PIC16F628A. Although this chip cannot directly control the 16 lines necessary for an 8×8 matrix, but it’s more than enough to control the 4×4 matrix! One frame on a 4×4 matrix is only 16 bits or equivalent to 2 bytes, while a frame for an 8×8 matrix might require 8 bytes, which is 4 times of the 4×4 matrix did!
If you want this Crossbar to be viewed by everyone, then you have to figure out the way to solder the LEDs at the intersection of each one. It’s better not to use the steel to hold the LEDs, as it easily rusted and has trouble holding onto the solder.
By the way, you don’t need to use the LM7805 or any capacitor, if you applied a regulated power supply onto this project.
Good luck with your project!