We’re finally starting to see robotic lawn mowers gain a little bit of traction as prices come down and consumer trust goes up. They work a bit like Roomba vacuums and pathfinding sophistication varies from one model to the next. But even the most basic models are still a lot more expensive than their secondhand gasoline powered cousins. So, Nikodem Bartnik decided to cut costs by making his DIY lawn mower robot very small.

To keep this prototype simple and affordable, Bartnik decided not to bother with any kind of mapping, pathfinding, object avoidance, or perimeter detection capabilities. It has no autonomous navigation features and instead the user must control the robot themselves. But sitting on a chair in the shade is still a lot better than pushing around a heavy lawn mower. Though the robot is only about the size of a dinner plate, so mowing an entire lawn will take a while.

Bartnik constructed the robot out of a sheet of plywood and 3D-printed parts. It has two driven wheels and each is turned by a small geared DC motor. The third wheel on the front is a caster that spins freely. An Arduino UNO Rev3 board controls both of those, as well as the brushless DC motor that spins the blades. Those blades swivel where they attach to the central hub, so centrifugal force causes them to swing outwards. Finally, the Arduino can communicate with the user’s smartphone through an HC-05 module for remote operation.

This won’t rival your dad’s zero-turn mower when it comes to power, but that wasn’t Bartnik’s intention. Instead, he sees it as a machine for giving the lawn a light trim every day or two before it can get too long. It’s slow, but that won’t be an issue if Bartnik implements autonomous navigation in the future.