Tuesday, June 26, 2012

The Rotating LED Clock

Time is an illusion...!!!!  

Mechanically scanning LED displays have a great place in the future. They may eventually replace the matrix of light bulbs found on standard displays. Spinning displays require much less power to drive the lights, as there is a fraction of the number of lights required in the matrix design. Our group hopes to take advantage of this and create an aesthetically pleasing clock. This clock also should keep the time accurately, slowly rotate the time so it is visible from all sides, is inexpensive to construct and maintain, and look more appealing than the average clock. The basic principle of working is the persistence of vision POV.


Persistence of vision is 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 visual form of memory known as iconic memory has been described as the cause of this phenomenon. Although psychologists and physiologists have rejected the relevance of this theory to film viewership, film academics and theorists generally have not. Some scientists nowadays consider the entire theory a myth.

In contrasting persistence of vision theory with phi phenomena, a critical part of understanding that emerges with these visual perception phenomena is that the eye is not a camera. In other words vision is not as simple as light registering on a medium, since the brain has to make sense of the visual data the eye provides and construct a coherent picture of reality. Joseph Anderson and Barbara Fisher argue that the phi phenomena privileges a more constructionist approach to the cinema (David Bordwell, Noël Carroll, Kirsten Thompson), whereas the persistence of vision privileges a realist approach (André Bazin, Christian Metz, Jean-Louis Baudry). 

This phenomenon of eye to persist the image for 16 seconds after the removal of the original image from eye sight is being used for this project


The clock has its torque during rotation due the reason that the battery is also rotating along with the PCB board. So to handle such high torque a geared motor fixed in a strong heavy wooden base is used. 


The Program is written in MikroC Pro for PIC. The TIMER0 built in module of the PIC16F877A is used for the purpose of second determination in accuracy and from this the minute and hour is derived by fundamental mathematical calculations. The display sequence is send to PORTB set in output mode from an array of the sequence to be displayed. The initial time is set in the program itself.

TIMER0 uses an interrupt flag T0IF which set when the counter overflows. When this flag is set the interrupt occurs and we can execute the required service routine. After that the flag must be reset in order to determine the next interrupt occurrence. The time taken for the counter to overflow is designed so that the time taken for that is one second. That’s how the second is determined and from that the minute and hour is determined.




The program for the task is written in mikroC pro for pic which is attached in the supporting files. The logic is to blink the LED's in the instance to display the string of time stored in the controller which is made to increment as per the regular time reference clock. The same circuit can be made used to display any strings. But i have chosen the clock to be displayed.


  1. Proteus Files
  2. HEX file
  3. Program File

Good Luck.

Sooraj Shenoy

1 comment:

  1. Internet esta plagado de este proyecto pero hasta ahora este es el mas resumido y sencillo lo probare. sigue así =)