Holo Clock is a novel 3D-printed clock that tells time using a pair of rotating rings
Simply looking at a traditional analog clock sitting on a wall somewhere got pretty boring for one Instructables user who goes by saulemmetquinn, which is partially why they wanted to create a novel design instead. Their device uses almost entirely 3D-printed components that come together to form the “Holo Clock,” since it seems holographic with its floating minute and hour hands.
The Holo Clock project started with a surprisingly complex design in CAD software. There are two rotating rings that are lined with teeth that sit stacked horizontally. The back ring is the minute hand, and because it is moved almost directly by the stepper motor, it spins more quickly. The hour hand is driven by a set of gears that reduce the output of the minute hand’s cogs by a factor of 60, thus making it turn at the correct rate.
The electronics for the clock are extremely simple. It uses an Arduino Uno with a set of four output wires, along with power and ground, to control a ULN2003 stepper motor driver. This in turn outputs current to a generic 5V stepper motor that spins the first drive gear at a known, precise rate for consistent timing. Likewise, the code is also straightforward, as all it must do is step the motor a certain amount depending on how many steps are left within the loop.