ESP32-powered 3D-printed solar system model with a working Moon I built a fully 3D-printed mechanical solar system model driven by an ESP32, and tried to avoid the usual fixed gear ratio approach. Instead of continuous gearing, all rings rotate freely. The ESP32 calculates the planetary positions (Meeus-based) and then drives a single stepper motor in a sequence of forward/reverse moves to “pick up” and position each ring individually. The tricky part was getting the engagement sequence reliable so each ring is left behind at exactly the right angle. Another challenge was the Moon: mechanically it uses a simple 1:11 ratio (6-tooth gear inside a 66-tooth ring), which obviously isn’t correct. So I compute where the Moon would end up and apply a correction during the initial homing movement by rotating the whole system slightly further. Timing is handled by a DS3231 RTC, so it runs fully offline. Once per day it performs a short positioning sequence.…