Abstract: The Pendulum Whiteboard Printer is an effector platform for a fully-automatic robotic device for marking or otherwise effecting whiteboards, pinboards, or other vertical surfaces The effector platform is designed to be suspended by two suspension wires whose lengths are adjusted by motorized spindles mounted above and on either side of the board surface. The position of the effector platform is adjusted by winding and unwinding the wires. Electrical power is supplied to the effector platform through the suspension wires or from an on-board battery. Control of a pen and/or other apparatus on the effector platform is achieved through modulation of the power voltage. The effector platform may be fitted with a variety of end effectors such as dry-erase markers, gripping elements, and squeegees.