A countdown timer is usually a number on a screen and a button somewhere nearby. Maker mircemk’s “Universal Timer” collapses that gap: the input device and the display are the same circular surface, and turning one turns the other.
The build is based on Elecrow’s CrowPanel 2.1-inch “Rotary Display,” a 480×480 round touchscreen module built around an ESP32-S3 with a physical rotary-encoder ring set into its housing. Twisting the ring to set a countdown rotates the on-screen graphics to match, so the dial you’re turning and the dial you’re watching are the same object rather than a knob next to a readout. As the countdown nears zero the display shifts color, and a buzzer — driven off a PCF8574 I2C I/O expander — sounds when time runs out.
It’s a small build, but it’s a clean argument for a specific idea: a physical rotary input and a circular display aren’t just compatible shapes, they’re the same interface if you let the software treat them that way.