Kinetic Art with Half Square Triangles
16 steppers create dynamically changing artistic display.
As Andrei Erdei puts it, “Half square triangles or HST blocks are some very interesting geometric shapes.” They’re used in applications such as quilting to create interesting patterns, and a 4x4 square arrangement of them can be used to form 322,650 combinations, each of which has a certain symmetric property. While one pattern is interesting, Erdei made a device that dynamically rotates all 16 HST blocks to display new patterns on the fly.
The setup is shown below in a nice yellow and black triangle pattern, rotating through different geometries. Behind these 16 squares – arranged at alternating heights so as not to hit one another – is a 4x4 matrix of 28BYJ-48 stepper motors mounted to an MDF backing via 3D-printed parts. An “Arduino” Mega 2560 mini is tasked with controlling the kinetic art piece, along with ULN2003 drivers and MCP23017 I/O expander modules to account for the huge number of outputs needed. Microswitches are used to provide homing.
The results maybe be neat, but Erdei admits that this build, although interesting, gave him quite a few headaches. The ULN2003 driver setup with this many 28BYJ048 steppers is a tough approach as it takes a huge number of digital outputs, and there were noticeable differences between motor manufacturers. He notes that he will do things a bit differently if he decides to pick it up again, yet it would seem that you learn something whenever you try an innovative project! Code is available on GitHub, and he’s even designed an interactive simulator if you want to check things out further!
