12 x 12 NeoPixel Ping Pong Ball Array (Vertical Rainbow Effect)

This is a follow-on to our “Random Color Drips with Fade Effect” experiment ( My current hobby project is to build a 12 x 12 array of ping pong balls, each containing a tricolor WS2818-based (NeoPixel) LED.

{Check out my Cool Beans Blog at

On the one hand, we’re taking things step-by-step. On the other hand, I started to get worried that you would think we were only ever going to light up individual pixels, so I decided to throw this rainbow effect together.

In this case, we are presenting the rainbow using the 12 columns forming the display (in my next video, we will display the rainbow diagonally).

FYI All of this is discussed in more detail in the November 2020 issue of Practical Electronics (PE), which is the UK’s premier electronics, computing, hobbyist, and maker magazine ( Also, the code for each of my sketches (programs) discussed in this issue is available to subscribers from the magazine’s website. But wait, there’s more, because both print and digital versions of back issues are available (