This project was inspired by some larger light effects I've seen on buildings.
I decided to try aranging 40 RGB LEDs to a 1m bar and see how it looks.
The LEDs are mounted to a 1m aluminium profile (u-shaped). It was some work to solder the 120 wires...
This version did not look bad, but multi chip LEDs do not mix the colors properly, so I bought a 1m frosted acryl glass pipe. Again, not bad, but I figured out it looks best if you mount the whole pipe in front of the LEDs.
I used a ATMega16 for this one, controlling 15 74HC573 (bad idea btw). In order to get full brightness, I used
18 ULN2003 to sink each chip with full 20mA. In retrospect, it would have been easier to use just 5 8-bit shift registers and connect each colours cathodes.