A drawing arm out of LEGO
Python running on a LEGO Mindstorms EV3 brick, driving a two-axis drawing arm with a mouse-controlled cursor and a pen-lift servo. Coarse hardware, surprisingly precise output.
Demo. Drawing in Norwegian.
How it worked
- Two motors drove an X/Y carriage over a paper bed.
- A third small motor lifted and dropped the pen, isolating start/stop strokes.
- Python on the EV3 read a stream of (x, y, pen-down?) tuples from a host PC over Bluetooth.
- The host could either play back a saved stroke list or feed it live from the mouse, so drawing on the screen mirrored to ink on paper.
What I learned
That mechanical play is a force you cannot ignore. Backlash, flex, and an uneven paper surface ate more accuracy than my code ever did. A surprising chunk of the project was characterising those errors and compensating for them. My first taste of "real" robotics, where the math meets the physics.