Charlie, my Mindstorms chess robot, rebuilt ten years after the first version. A phone now does all the vision.

LEGO builder and Reddit user /u/Alex_darrous has unveiled an impressive, fully rebuilt chess robot named Charlie, marking a decade of evolution since the first iteration debuted in 2015. While the original 2015 build required a separate laptop running MATLAB to process the board state, this updated version modernizes the vision system by utilizing a smartphone camera mounted on a custom stand, allowing the robot and its board to operate entirely on their own.

Constructed from approximately 3,100 pieces, the build primarily relies on classic NXT-era Technic elements, supplemented by several custom 3D-printed components that include the guards, phone stand, and parts of the gripper mechanism. The most difficult engineering challenge involved the capture sequence, which requires the robot to cleanly lift an opponent's piece off the board and park it safely without disturbing any neighboring pieces. This complex maneuver forced the designer to refine the gripper through roughly a dozen distinct iterations.

The builder designed the entire model digitally using BrickLink Studio, which significantly streamlined the process of recreating the building instructions compared to the older LEGO Digital Designer (LDD) file format used a decade ago.

Projects of this scale require immense patience and organization, so builders taking on complex Technic creations might want to grab a LEGO storage organizer to keep all those pins and gears sorted, or use a brick separator when adjustments are needed during the prototyping phase.