Complex 3D-Printed Mechanisms Make This Earth Clock Mirror the Real Thing

Despite what Flat Earthers will tell you, our seasons and day/night cycles make perfect sense when you consider how the Earth moves around the Sun. The Earth rotates on its axis, but that axis is at an angle offset to the plane of the Earth's orbit around the Sun. The result, if you're only looking at the Earth, is that our planet seems as if it is wobbling. That makes it difficult to create an accurate moving model without including the sun. But SimonRob surmounted that challenge when he built this 3D-printed Earth Clock that matches our planet's motion.

SimonRob's goal here was to create a self-contained model that illustrates both the Earth's rotation on its axis and its orbit around the Sun. That means it needs to move in two axes: the first is the daily rotation on the axis tilted at 23.4 degrees from vertical and the second is the yearly rotation around the Sun. There isn't a representation of the Sun in this model, but you can point a lamp at the Earth Clock to get a rough idea of which side of the Earth is getting sunlight. This won't take into account the elliptical orbit of the Earth around the Sun, but it's a fair representation suitable for a quick glance on your desktop.

Both rotational axes are driven by a single motor and a complex series of 3D-printed gears, similar to those in a mechanical wristwatch, determine their speeds. The motor speed is constant, but it is very slow and has to remain as consistent as possible to be accurate. That's why SimonRob used a stepper motor to drive the gears. An Arduino Nano development board controls that stepper motor through a ULN2003 driver board. The only other components are two push buttons, two resistors, a USB cable for power, and screws. You can set the day and time by pushing the two buttons, which will quickly rotate the motor either clockwise or counterclockwise. If you want the Earth to look realistic like SimonRob's model does, you will need to paint it.

This is more of a desktop toy than a useful clock, because it is difficult to determine the actual time by looking at the model. But it is a cool way to visual the Earth's movement, and also a fantastic demonstration of planetary gears and complex mechanisms.