In a first step I was planning to try the matrix on an Arduino Mega.
I’ve never tried out multiplexing before. I’m discovering Arduino actually (Xbee, IR,…).
I was thinking of using 2x 74HC595, but I’ve not been really looking in to it, yet. But, sure i will compare the benefit of MAX7219 onto 74HC595.
By the way, congratulations for the nice manufacture for a prototype. Only with cardboard it already has personnality. I really like it.
Your “big project” also partly inspired me (as some others on LMR). Instead of a cylinder, I built a cubic frame. The LED matrix would be one of the robot media for communicating.
The 6502 is an inside joke for futurama fans. Those 7219’s are good but pricy. Did you get yours for a good price? I saw a story about fake ones. But as your head works perfect, yours are obviously the real thing.
This is one of the more novel designs i’ve seen on this site. Very well done. It is definitely one of my favorite robots here. I do have a fun experiment for you. Try this (its easy): Cut a piece of acrylic or plexiglass or other suitable clear plastic to cover the eyes and make a simple lens. Next, cut a piece of tracing paper to fit behind the lens, but in front of the LED eyes. This will diffuse the light for a softer glow and a neater effect. Experiment with different brightnesses and levels of diffusion (by using additional sheets of tracing paper and adjusting the brightness level on your LED matrix) until you find the perfect result.
Also, if you were to paint the surface behind your LED matrix black, and tint the lens with some window tinting film from your local auto parts store, the face of your robot would be completely black when turned off, but have bright visible eyes when in operation. The matrix assembly would ‘disappear’ behind the tinted lens. This would be an effect similar to EVE as posted by OddBot. I used the above technique to great effect when I developed an RFID card reader / door lock with a screen that displayed lock and unlock icons with LEDs. Its design was simple, but the light diffusion / optical layers made it appear more high tech and impressive.