Mechanical Eye
Animatronic Mechacnial Eye
Intro
This project tackled the challenge of building a human-scale animatronic eye with a compact control assembly small enough to fit cleanly behind the eyeball. Using sub-micro servos and a Nintendo Wii Nunchuck for live control, the design allows expressive movement and blinking via a joystick and gyro. Miniaturization made the build tricky, with custom-bent metal rods and fragile servos requiring precision and care. The final result is unsettlingly realistic, with smooth motion and lifelike blinking. While it’s not yet embedded into a larger prop, future iterations aim to simplify the design and improve durability—because bending tiny rods by hand is fun exactly once.
Concept Origin
This was a wild and rewarding project that really pushed my programming skills. It started with a design observation: most animatronic eye mechanisms are _much_ larger than the eyeball itself. That makes them tough to integrate into props without carving out a massive space behind the surface.
While researching (as one does), I stumbled across sub-micro servos—tiny motors roughly half the size of standard 9g servos. That sparked the question: could I build a human-scale animatronic eye with a control assembly small enough to fit behind it cleanly? The goal was a more compact, expressive, and mountable design—plus a simple way to control it live and have it react to the room in real-time.
Design & Development
This became one of my longer-running projects, mostly because it was a huge learning experience on the programming side. It was my first real step outside the Arduino safety bubble I still used the Arduino helper library, but the code was written from scratch. For live control, I used a Nintendo Wii Nunchuck: they’re cheap, widely available, and surprisingly easy to integrate. The joystick controlled eye direction, and the built-in gyro allowed for expressive blinking via the eyelids.
Originally, I tried to house both eye-direction servos inside the eyeball, but it made the whole thing too bulky. After several iterations, I landed on a hybrid setup: one servo inside the eye, and three just behind it (one for the second axis, two for the eyelids). That kept the full mechanism to about 2x the size of the eyeball not bad, all things considered.
On the electronics side, I used off-the-shelf modules to handle servo control, power management, and communication with the Nunchuck. I also made the eye itself removable so the detailed eyeball could snap out easily if the mechanism broke or needed replacement.
Prototype & Build
Miniaturization made this a tough build. When things get small, tolerances matter a lot more. Custom-bent metal rods connected the servo horns to the moving parts: one for vertical movement, one for each eyelid. These bends require a bit of hand skill—standard fare for folks familiar with RC planes, but not quite beginner territory.
Most parts were 3D printed and designed to work straight off the build plate. Wiring was straightforward: power, data, upload the sketch. One hiccup I ran into was with the servos themselves—unlike standard RC servos, these micro versions are far more fragile. Stalling them even briefly can permanently damage the motors.
Final Result
The final result is super satisfying. There’s a bit of a learning curve to get smooth, realistic motion, but once dialed in, the eye is _very_ unsettling—in the best way. The blinking really sells it.
I haven’t yet embedded it into a larger prop, but I have a few ideas for how to simplify the build even further. Ideally, I’ll design a version that removes the need for hand-bent rods and makes the system more robust. Time to add that to the list.
