A Very Sketchy Robot
Mural is a $60 open source robot, powered by an ESP32 and stepper motors, that turns your walls into canvases for beautiful artwork.
Mammas don't let your babies grow up to be robotics engineers. If you do, all those years of teaching them to be decent, responsible people that do not — under any circumstances — draw on the walls will go out the window the moment that they are introduced to microcontrollers and stepper motors. These parts may seem innocent enough, but oh no, not in the hands of a roboticist. Their warped minds will take an ESP32 and turn it into an instrument of domestic destruction.
Nik Ivanov has built one such machine, which is called Mural. This robot is a low-cost, open source wall plotter that can easily be built from readily available parts. Once in place, Mural is capable of autonomously drawing wall-sized art of any sort using a marker (including washable markers, which can later be removed without a trace). It only needs to be supplied with a vector graphics file, and it will reproduce the image as it clings to the wall and zips around.
Mural was built around a NodeMCU ESP32 development board that handles all of the system’s data processing and interfacing with external components. A pair of NEMA 17 stepper motors and an MG90s metal gear servo round out the main components, with driver boards, timing belts, wires and other such bits and pieces completing the hardware build. A large number of 3D-printed parts tie everything together and turn Mural into an actual robot instead of a mess of motors and wires.
The robot hangs from timing belts that are attached on the wall, at a point above where the artwork is to be drawn. The stepper motors are attached to belts on opposing sides of Mural. As such, by carefully controlling the distance each stepper moves up or down the belt, any X/Y position on the wall (within range) can be precisely traveled to. The servo is used to move the marker up and down as it is needed for drawing.
All of the parts for the build, not counting the 3D prints, only cost about $60. This is surprisingly inexpensive for an autonomous wall plotter robot. The low price tag was made possible in large part by the clever belt-driven locomotion mechanism.
A full list of the materials needed, 3D model files, and firmware is available in a GitHub repository, so go grab everything if you would like to build your own copy of Mural. There is even a detailed, step-by-step build video below to get you on your way if you are planning to throw caution to the wind and ignore your parents’ warnings about drawing on the walls.
