ShadowClock : The electronic sundial. An ME203 project.
The electric sundial functions on the same principle as a traditional axial sundial. High power LEDs replace the sun, casting a continuously rotating shadow over a polished aluminum gnomon onto roman numerals, indicating the hour and minute. A small red light illuminates a port on the side of the base, blinking each second, indicating the "seconds hand".
The clock uses a planetary gear train (36:1 reduction) driven by a bipolar stepper motor. The continuous rotation of the lamp necessitates using brushes for electrical contacts and a lazy susan turntable bearing. The brushes make contact with copper slip rings that are fixed in the base.
The 13 inch diameter base and top are polished aluminum manually machined on the rotary table attachment to the mill.
The shadow is cast on a sand-blasted acrylic cover with Roman numerals.