Propeller clock

PROPELLER CLOCK

OBJECTIVE :-
In this project, our aim is to use PIC or 8051 microcontroller to control a row of LEDs to function it as a clock. ABSTRACT :-
The Propeller Clock is an electronic device which has a series of LEDs on board that rotate with the help of a motor to give an illusion of a watching a clock ( Digital or Analogue ). This requires a DC motor which rotates the PCB connected to it with sufficient speed so as to create the illusion. The LEDs are connected to a microcontroller PIC16C84 or 16F84 which is so programmed to switch ON and OFF the LEDs in a sequence and with a time delay to approximately match with the rotating speed of the motor. One of the phases of the DC motor is directly fed back to the microcontroller to identify the position of the motor at any instant. In display , the lights, LEDs, or what ever makes visible dots, are not on all the time. The leds turn on and off, one after another, very rapidly. Due to the slow response of the human eye, we get the impression that the lights are on all together and we can read the display. The basic principle used is the persistence of vision. As the LEDs rotate at a high speed they can be controlled with the help of a micro-controller so as to glow them in such a combination that a floating display is formed.

Working :-
If you move a bright light fast by the eyes, it will leave a line behind because the human brain and eyes are slow to interpret fast changes in light intensity, leaving an afterglow. If a row of LED’s is moved sideways while the LED’s intensity is changed, an image will shortly visualize in the air where the LED’s are moved. If this is done several times, for example if the LED’s are mounted on the end of a bar mounted on a motor as in the figure on the right, the same area in the air could be scanned several times showing the same image each time. Done at high speed it would generate a quite good virtual display hanging in air thanks to the persistence of vision effect of the brain. People has started to refer to this kind of display as POV-displays (Persistence of vision displays) as if it was the only type of displays depending on the persistence of vision effect but that is kind of ignorant as many display types use the same effect, like for example CRTs and multiplexed LED displays, thus “mechanically scanned display” is a more accurate name. How this clock works :

A motor spins the “propeller”, and a small microprocessor keeps track of time and changes the pattern on seven LEDs with exact timing to simulate an array of LEDs. It is an illusion, but it works nicely.

Future Scope :
Once developed at a large scale and used with multicolor LEDs can be used to replace LCD screen. Conclusion :
This project explains about a basic principle of persistence of vision usingsimple low cost circuit. This can be used in large scale to form a nice display screens..