Analog Magnetic Clock

The project features an analog clock that has 3 magnetic balls to show seconds, minutes, and hours. The entire mechanism was driven by a single SG90 micro servo and a ratchet-pawl mechanism, which then powers a compound gear train to drive the 3 magnets in continuous, rotational motion. The servo can be easily programmed with an Arduino or a Raspberry Pi.

The entire inner mechanism is 3D-printed, and the case was made of laser-cut plywood with an intricate living hinge design around the sides.

Time-lapse demonstration

Presentation Video

Image Gallery

The Design: Inner Mechanisms

As part of the group project, I designed and fabricated the entire inner mechanism. I first calculated the gear train using help from an online gear generator. Using help from the software, I came up with a gear system that results in the correct gear ratio on 3 concentric internal gears; I then modeled the gears and supporting structures in SolidWorks.

During the process, I payed extra attention to design the parts for manufacturability, specifically for FDM 3D-printing. I divided the support structures into different components that can be later assembled to produce a more complex geometry,

Initial concept sketches and final CAD rendering.

The ratchet and pawl mechanism is shown below. The 2-segment arm is attached to the servo, which swings back-and-forth to push the gears forward in a pre-defined increment. Another idler pawl is placed at the other side of the ratchet to prevent back driving of the gear as the servo arm moves back to the original position.

Assembly

Assembly Process