I designed and built this as a 4-bit Binary Mechanical Counter, but it could actually be configured using as many bits as is practical.

This is a great interactive and visual way to introduce the concept of counting in binary to students.

ELEGOO

ELEGOO NEPTUNE 3 Pro

Doesn't Matter

Yes

0.2mm

60%

There are five unique parts in all: left base, right base, and handle, which need to be printed once each, and the bit and bridge parts, which have to be printed once each for the number of bits in your configuration.

I printed the bit piece using tree supports and 60% infill, so that the ball would carry enough weight to accomplish its purpose, but you can experiment with other settings if you wish.

The digits zero and one on either side of the bit are embossed and are both plainly visible (although I used black and white acrylic paint to enhance their appearance for the video).

The design of the bit incorporates a ball (that is actually printed inside of an enclosure, using supports), which rolls to the bottom of the enclosure whenever the bit is flipped over, causing it to return to rest hanging vertically.

The counter is incremented by turning a handle on the right end, adding one bit at a time.

Each bit has a little flag that falls down whenever the bit is a one, causing the bit to its left to flip over whenever it transitions from a one to a zero.

Whenever the counter reaches its maximum (which in my case was fifteen, since I used four bits), incrementing it once more resets the counter to start over from zero.