Persistence of Vision
From MARS Wiki
Contents |
Project: A Simple Persistence of Vision Device
Here is a spreadsheet to calculate table lookup values so you don't have to do it by hand.
Project Description
Sometimes it is nice to have an LED matrix output device, but LED matricies and the drive circuitry to control them can become somewhat expensive at times. Therefore, it is desirable to have a cheap alternative. For this purpose, a persistence of vision (or POV) device can be quite handy. A persistence of vision device uses a single row (or column) of LEDs and simply turns the LEDs on or off depending on the position of the LEDs.
Examples of LED POV Devices
Persistence of Vision: Software Overview
For this simple starting project, we will consider a rotary POV device (one that simply spins in a circle), that implements a virtual sign (a large table showing the different LED values that need to be on for a given column of the virtual sign). One complete spin of the circle will display the "virtual sign" in it's entirety. For this project, we will utilize an external interrupt pin and 2 Timer Modules. One timer will serve as a free-running timer, determining how much time has elapsed between interrupts. Based on this time, it will determine how long each of the individual columns of the sign must be on, and the other timer module will engage the LEDs for that amount of time before moving to the next table entry.
