  This letter introduces HOPPY, an open-source, low-cost, robust, and modular
kit for robotics education. The robot dynamically hops around a rotating gantry
with a fixed base. The kit lowers the entry barrier for studying dynamic robots
and legged locomotion in real systems. The kit bridges the theoretical content
of fundamental robotic courses and real dynamic robots by facilitating and
guiding the software and hardware integration. This letter describes the topics
which can be studied using the kit, lists its components, discusses best
practices for implementation, presents results from experiments with the
simulator and the real system, and suggests further improvements. A simple
controller is described to achieve velocities up to 2m/s, navigate small
objects, and mitigate external disturbances (kicks). HOPPY was utilized as the
topic of a semester-long project for the Robot Dynamics and Control course at
the University of Illinois at Urbana-Champaign. Students provided an
overwhelmingly positive feedback from the hands-on activities during the course
and the instructors will continue to improve the kit for upcoming semesters.
