11-08-2012, 01:19 PM
Propeller LED display
[attachment=31111]
Introduction
What is Propeller LED Display?
Propeller is a term generally associated with rotating fan , revolving at high RPM. Just like a propeller, this is a special kind of a rotating display.
How it works?
PERSISTANCE OF VISION
This is a phenomenon of the eye by which an afterimage is thought to persist for approximately 1/25th of a second. So if someone is observing images at rate of 25 images/second, they appear to be continuous.
The Sensor
Sensor used in this project is MOC 7811 from
Motorola. This is a slotted coupler/interrupter device.
In each revolution as the beam is interrupted,
the sensor generates a positive pulse. Microcontroller
will execute interrupt routine, When a pulse occurs.
Interrupt routine measures the total time taken for one revolution, divides it by 120, and stores the result into another timer,
Configured in auto-reload mode.
Now, the timer overflows after tiny intervals of time. Each time it overflows, next stored value is called from the lookup table, and displayed.
[attachment=31111]
Introduction
What is Propeller LED Display?
Propeller is a term generally associated with rotating fan , revolving at high RPM. Just like a propeller, this is a special kind of a rotating display.
How it works?
PERSISTANCE OF VISION
This is a phenomenon of the eye by which an afterimage is thought to persist for approximately 1/25th of a second. So if someone is observing images at rate of 25 images/second, they appear to be continuous.
The Sensor
Sensor used in this project is MOC 7811 from
Motorola. This is a slotted coupler/interrupter device.
In each revolution as the beam is interrupted,
the sensor generates a positive pulse. Microcontroller
will execute interrupt routine, When a pulse occurs.
Interrupt routine measures the total time taken for one revolution, divides it by 120, and stores the result into another timer,
Configured in auto-reload mode.
Now, the timer overflows after tiny intervals of time. Each time it overflows, next stored value is called from the lookup table, and displayed.