Fish are great pets for people who don't want love, cuddles, or interaction of any kind. But while you can't take your fish to the park or snuggle with them when you've had a rough day, they are beautiful to watch. A good aquarium can enhance that beauty and also give the fish a more pleasant environment. I don't know if fish actually find tiny treasure chests interesting, but it feels like they should. But Zach Frew's shrimp have more sophisticated tastes and weren't happy with a tacky treasure chest, which is why he built an automated sand art table into his aquarium.
This project, called Sisyphish, was inspired by the Sisyphus and Sisyphus Mini kinetic sand art tables that we covered in the past. Those tables have large basins full of sand in which a ball bearing rests. Underneath the each table's basin is a magnet that moves in two axes. As the magnet moves, it pulls the ball bearing through the sand to produce patterns. Frew's Sisyphish aquarium works in much the same way, except the sand is underwater. Because the ball is magnetically-coupled to the gantry, it can remain submerged while the electronic components are safe and dry in a separate compartment.
Unlike the Sisyphus tables, which have two linear movement axes for the gantry, the Sisyphish gantry is polar. It has a rotating arm for the rho positioning and a spur gear for the theta positioning. This is more compact and eliminates the need for expensive linear rails and bearings. An Einsy Rambo board, which is normally used for 3D printing, controls the two stepper motors through TMC drivers. Frew chose that board because the stepper drivers can detect a stall, which means that they can find home without limit switches. A Raspberry Pi running Octoprint sends G-code commands to the Einsy Rambo. Frew creates the paths used to generate the G-code with Sandify software.
Frew filled the Sisyphish aquarium with Taiwan Bee Shrimp, which are colorful little critters. Unfortunately, they also poop a lot. Drew says that their waste has caused the sand to lose its luster. But this is still an awesome project and a very novel use of a kinetic sand art machine.