Turning Wood Into Pixels

4K display? Bah! 60 frames per second? No thank you! Back in my day, we didn't have any of that fancy technology. Our screens were made of wood, the pixels were updated one at a time, and we liked it that way. We'd gather around the warm glow of a CNC machine that was slowly spinning pixels and be grateful for the entertainment. Kids these days with their millions of pixels…

OK, you caught me. Displays with wooden pixels obviously did not predate modern CRT or LED displays, but they do exist now! Software engineer and hardware hacker Ben Holmen, for reasons not entirely known, had a burning desire to build a large, inefficient display. After experimenting with everything from ping pong balls to styrofoam and golf balls, he settled on creating a 40x25 grid of individually-addressable wooden block pixels called the Kilopixel.

The unusual choice of using wood for the pixels was made for a few reasons. On the one hand, buying 1,000 of anything is pretty expensive. Even the cost of a 50 cent ball really adds up when you need that many. Aside from that, Holmen is very comfortable working with wood. So despite the fact that making 1,000 of anything takes a lot of time and effort, that won out over ponying up for a pile of junk.

The display is made up of rotating blocks of wood sitting on shelves, with each block being painted black on two sides. A two-dimensional CNC machine moves to the X and Y position of a block, then a “poking” mechanism pushes on it to rotate it 90 degrees, flipping it from dark to light, and vice versa. A Raspberry Pi is wired into the CNC machine’s controller to make this happen.

Holmen wrote an API that generates the G-code necessary to move the CNC machine from one pixel to another, and to trigger the poking mechanism. A light sensor tells the software what the current state of a pixel is (light or dark), to avoid having to set the display to a known initial state, or issues where the software’s internal state representation gets out of sync with reality.

Many of us have built some type of elaborate, yet not entirely practical, project before, so we know how it goes — building it is the fun part. So after drawing a few pictures on the new display, it is probably going to start collecting dust. But not if it is shared with friends!

Holmen took care of that by building a web app that allows anyone to submit a picture to be displayed on the device. After it is accepted, you can then watch the image being produced on a livestream. I’m only going to tell you this once, because I know what immediately came to your mind — keep it classy!