Math lessons in the fifth grade cover — amongst other things, I hope — the binary system.

My favourite fifth-grader asked me for help. Explaining the number-systems is one thing, but you can do more if you’re a geek with a laser cutter. So I built her a binary counter:

The idea for this came from Twitter, I remembered seeing the video a while ago. I couldn’t find any files for this, so I called FreeCAD to the rescue.

I really like the result. And it looks as if the physical model really did help understanding the numbers.

If anybody is interested in building their own version of this: here are the files (planned for 4mm material):