This Robot Is the Chalk of the Town

Suburbia can be a brutal place to live. Sure, neighbors smile and greet one another with friendly conversation, but all too often, lying just beneath that facade is a desire to find any possible weakness and exploit it. After spending an afternoon mowing one’s lawn in the summer heat, a neighbor might comment that things would be much easier with a fancy (and very expensive!) riding lawn mower like they have. And of course they are very sorry to hear about your car trouble, but it would really be no trouble at all to give you a ride in their brand new convertible.

These sorts of situations have given rise to the idiom “keeping up with the Joneses” that many people — suburbanites in particular — feel they must do at almost any cost. Why do so many of us care about petty things like how green the neighbor’s lawn is, or where they went on vacation? That is a question for another news outlet as we stick to technology around here, but whatever the reason may be, YouTuber MrDadVs is working very hard to keep up.

In the case of MrDadVs, it is not about lawns or cars, however. It is about…sidewalk chalk art, of all things. He and his family are some pretty amazing sidewalk chalk artists, but he feels it is only a matter of time before the neighbors improve their skills and show them up. What if his own skills have peaked? Oh, the horror!

Driven by a single-minded purpose, MrDadVs planned and plotted, ultimately deciding to build a chalk art robot appropriately named A.P. (the initials of a character in a 1913 comic that spawned the phrase “keeping up with the Joneses”). The goal was to be able to draw precision designs on 9 x 12 foot squares of a driveway, so some of the most obvious options, like an XY gantry robot, were dismissed as too large to be practical. Even a rolling robot with a single axis of movement would be excessively large.

So MrDadVs went in a somewhat more unconventional direction in designing and building a rotating robot. A.P. has a roughly four-foot arm that rotates around a central base, giving a drawing area of about eight feet in diameter. A linear actuator moves the drawing tool in and out to make it possible to color any area within that circle. A liquid chalk mixture of some sort is sprayed on the driveway, although MrDadVs did not give details on the composition of the mixture or the spraying mechanism.

In order to program the robot, artwork is supplied in SVG format. This file is then converted into G-code (much like a 3D printer uses), before being wirelessly transmitted to the robot, which processes the G-code into actuator movements with the help of software called FluidNC.

This software, as virtually any software that deals in G-code does, works with a Cartesian coordinate system. But since the rotating robot operates using polar coordinates, a conversion script was necessary to make things work smoothly. It is a bit hacky, especially when it comes to long, straight lines, which are actually a lot of very small half circles in sequence, but it gets the job done and is far easier than modifying FluidNC to support polar coordinates.

To avoid the slowness of having to test A.P. with actual chalk drawing, MrDadVs instead installed an LED on the drawing arm and used a GoPro camera to do some light painting. After working out the kinks with this setup, the robot was ready to shame the Joneses by drawing some of the best chalk Super Mario Bros. characters you have ever seen. This is not the end of the line, however. MrDadVs is already planning to build an updated chalk art robot in the form of a free-moving rover to draw bigger and better things. Stay tuned for updates!