If you need a place to put coins, you can use a jar, or perhaps a simple piggy bank that you bought just for that purpose. If you want something that’s a bit more fun, check out the transforming box in the video below by Japanese “deformable gadgets artist” VALiMA.
This unit, which resembles a Companion Cube from Half Life, features a black inside section, as well as four white corner pieces that form a partial shell. When a button on top is pushed, these corner sections pop out, revealing a coin slot on the top, as well as a hole on the side that allows coins to escape when it’s time to actually spend money.
The device is controlled by an Arduino Pro Micro, which activates a servo to push the corner sections out. This is accomplished using a cam system inside, and a series of pusher rods. The movable corners then snap back into place via springs. Channels on the sides keep these pieces in place, and raised “lines” on the bottom keep them off of whatever it’s resting on.
While the video below is in Japanese, it does a pretty good job of explaining things visually for those that don’t speak the language, including the fact that it’s powered by AA Hello Kitty Batteries. More build information, like 3D data, circuit diagrams, and the program used are available via VALiMA’s Patreon page.