Musical Xylophone Robot

In the first year of the Mechatronics Engineering program, our team was tasked with designing and programming a robotic system using LEGO Mindstorms kits and the RobotC programming language. Inspired by both the holiday season and Disney Imagineering’s animatronic shows, we set out to build a robot that could play Christmas carols on a real instrument. Beyond fulfilling technical course requirements, our goal was to create a project that was fun, interactive, and demonstrated the creative potential of mechatronics. 

To meet course requirements, the robot needed to integrate multiple sensors, use more than one motor, and feature interactive functionality beyond basic automation.

Instrument Selection
We explored several different instruments for feasibility.

• Wind instruments – Ruled out due to mechanical complexity.

• String instruments – Required higher force outputs than LEGO motors could deliver.

• Xylophone – Provided repeatable, precise note striking with minimal complexity, making it the most practical option.

Mechanical Design
The key challenge was enabling a limited number of motors to strike multiple notes efficiently. Options considered included:

• Individual mallets for each key (too many motors required).

• Linear motion to move a mallet across keys (slow and cumbersome).

• Rotational mallet system, chosen for speed and simplicity, using two motorized mallets that could individually pivot on a secondary motor to strike different notes.

Interactive Features
To enhance engagement, we programmed features that went beyond simple playback:

• Ultrasonic + Touch Sensor “Easter Egg” – If motion was detected and the touch sensor was depressed within a set time window, the robot played Silver Bells, simulating a festive “Santa arrival”.

• Song Selection Menu – Users could select carols via the LEGO interface, with melodies stored in a simple coded format for easy customization and additional songs.

The final system successfully played recognizable Christmas carols with over 80% note and timing accuracy, despite the speed limitations of LEGO motors. During presentations, professors and TAs were surprised by our achievements as they had previously noted that musical robots were often discouraged due to the difficulty of achieving consistent sound and recognizable music quality, but our solution demonstrated that automation in music, with the provided resources, was feasible when paired with the right instrument and mechanics.

This project was a pivotal first step in my engineering journey, introducing me to:

• Iterative design under mechanical and software constraints.

• Sensor-driven interactivity for user engagement.

• The importance of balancing creativity and technical feasibility.

Looking back, this project was more than just a fun introduction to robotics, it laid the foundation for many of my later engineering experiences. It was the first time I saw how software, sensors, and mechanical design had to work seamlessly together to achieve a goal, a principle I would apply in much larger projects like my autonomous navigation robot and capstone e-bike charging system.

It also taught me the value of user-centered design, even in a playful project, features like the hidden “Santa arrival” event and intuitive song selection made the system more engaging. That mindset carried forward into my later work, from improving ergonomics in manufacturing internships to designing immersive experiences in my sim racing rig project.

In short, this robot showed me that engineering is not just about solving problems, it is about creating experiences that connect technology, people, and creativity.