Lotto ball machine

Mechanical Rock runs a tech conference called Latency, and earlier in the year they asked me to make something that could help them to select door prizes at the conference.

The idea I came up with was a lotto ball machine that uses air to mix up the balls. The design was based around a cylindrical acrylic tube, with a bottom section made of steel (to match their sign) to house the fan and electronics. The fan would mix up the balls by blowing them around in a helical pattern, then a winning ball would somehow be selected, be blown up a tube in the middle of the cylinder, and pop out the top 🎉!

After a few design iterations with some basic cardboard mockups, I settled on the following size and shape. I drew a 3D model in Fusion 360, and then exported the steel and acrylic profiles to be laser cut.

CAD model of lotto machine
Annotated cross section of CAD model

This was one of the most challenging projects I've ever worked on. I learned a tonne along the way - bending and MIG welding thin sheet steel, selecting and speccing axial fans, cutting and flame polishing acrylic tube, installing brass threaded inserts into acrylic, generating a 5V 50kHz PWM signal from the Rasberry Pi's GPIO, controlling the RGBW LED strips, and more.

I took a few photos while building it - click any image below to open the gallery.

This is the finished machine in action (thanks to Hamish for the demo!). It's controllable via the web app and the API.

I'd love to hear what you think - please let me know on twitter! I'm really keen to take on more projects like this in the future - if you've got an idea for something that combines electronics, software and mechanical design and fabrication then please get in touch 😀