The Propeller Clock — Lucas Marques

The Problem

The objective was to create a digital clock that appeared to float in mid-air using a mechanical optical illusion. The technical hurdles involved synchronizing a spinning display to the human eye's persistence of vision and transferring power to a board rotating at 600 RPM without tangling wires.

Propeller Clock displaying six digits in mid-air — The completed Propeller Clock displaying a stable 6-digit time interface in mid-air.

The Engineering

I built the display around a line of seven LEDs and an Intel 8051 microcontroller. Carbon brushes deliver power to the rotating board. An infrared photodiode detects a fixed beam once per revolution, triggering an interrupt every 100 ms at 600 RPM. That reference synchronizes the LED flashes with the board’s rotation to draw a stable six-digit display.

Intel 8051 microcontroller control board — Control board housing power management systems.

Propeller clock logic and power regulation schematic — Circuit diagram with the logic and power regulation design.

Linear array of seven light emitting diodes — Linear 7-LED array.

High-speed direct current motor base assembly — DC motor (bottom view).

Carbon brush power transmission mechanism — Carbon Brush Contact.

Infrared optical synchronization photodiode sensor — Infrared optical sensor.

The Results

The working prototype produced the floating six-digit clock shown in the demonstration below. Built as my electronics capstone, it combined circuit design, embedded firmware, optical sensing, and a rotating mechanical assembly.

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Watch the six digits appear stable while the seven-LED board rotates. Optical synchronization times each flash to draw the clock in mid-air.