The Beating Heart Inside of a Different Kind of Chest

Halloween is coming at us, slowly but surely, like the antagonist in a slasher film. As the official Holiday of Makers (we took a vote), everyone in our community is scrambling to finish turning their most ghoulish ideas into real decorations. And though the Pirates of the Caribbean movie franchise is exactly known for its horror, it does have spooky elements. Inspired by the eponymous storage trunk in Dead Man’s Chest, Grendel Studios' Erik Finley built this elaborately locked chest containing an ominous beating heart.

In Pirates of the Caribbean: Dead Man’s Chest, the title refers to a literal chest (the kind used to hold gold and jewels) containing the still-beating heart of Davy Jones. Yes, the lore of the franchise got pretty convoluted somewhere along the way. Finley recreated all of that with a chest, complete with a key and locking mechanism, that holds an anatomically correct heart that beats loud enough to be heard from anywhere nearby.

The chest is a 3D-printed affair, with heavy-looking “bolts” around the rim of the lid. When the user inserts a key, which Finley made from welded steel for strength, and turns it in the lock, those bolts disengage and pop out. They’re just decorative and actuated by servos, but the effect is really cool. And the lock itself is functional — anyone who wants to open the chest will need either the key or a willingness to break things.

An Arduino Nano R4 board controls those servos, as well as another set inside the star of the show: the heart. That has a soft, squishy outer shell made from silicone poured into a mold. That shell fits around an inner core featuring a very clever mechanism to mimic the movement of a throbbing heart. Two high-torque servo motors push out rhythmically and the effect with the silicone shell in place is quite convincing.

The final piece of the puzzle was incorporating sound effects, which Finley achieved using a DFRobot DFPlayer Mini Player connected to a speaker underneath the chest. That plays the unmistakable beating sounds that are so delightfully foreboding.

Finley actually showcased this build at Open Sauce 2025 and so you may have seen it there. But if you missed it, the chest will also make an appearance at Maker Faire Rome in a few weeks.