How does propeller led clock work?

Answer 1

Led Propeller Clock based on "POV" .Persistence of visionis the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina.

The myth of persistence of vision is the belief that human perception of motion (brain centered) is the result of persistence of vision (eye centered). The myth was debunked in 1912 by Wertheimer, but persists in many citations in many classic and modern film-theory texts. A more plausible theory to explain motion perception (at least on a descriptive level) are two distinct perceptual illusions: phi phenomenon and beta movement. A class of display device described as "POV" is one that composes an image by displaying one spatial portion at a time in rapid succession (for example, one column of pixels every few milliseconds). A 2 dimensional POV display is often accomplished by means of rapidly moving a single row of LEDs along a linear or circular path. The effect is that the image is perceived as a whole by the viewer as long as the entire path is completed during the visual persistence time of the human eye. A further effect is often to give the illusion of the image floating in mid-air. A 3 dimensional POV display is often constructed using a 2D grid of LEDs which is swept or rotated through a volume. POV display devices can be used in combination with long camera exposures to produce light writing. Ali Zafar Notkani

Answer 2

A propeller LED clock works by flashing LEDs mounted on the tips of rotating blades. As the blades spin, the LEDs turn on and off in a controlled sequence to create the illusion of a clock face. By adjusting the speed of rotation and timing of the LEDs, the clock can display the current time.