Tricolor light emitting diode dot matrix display system with audio output

In this paper, a novel tricolor dot matrix display system in which all the LEDs are modulated and encoded with audio information is presented. The novelty is on the concurrent use of the tricolor LEDs for simultaneous visual message display and audio signal transmission in a free space optical link. The system is comprised of a tricolor LED dot matrix display panel with an interface circuit to a computer, an audio signal transmitter and a receiver. The system further comprises an executive program that runs on the computer for the display control of characters, decorative pattern or messages on the display panel. The receiver, combined with a speaker, is located at some distance from the display system. The receiver is designed to demodulate the optically transmitted audio information and reproduce the messages with the speaker. For modulating emission of tricolor LEDs, an oscillator is used to vary the frequency of on/off periods of the LEDs. The frequency of flicker is high enough to be indistinguishable by human eye and hence display appears to be constantly illuminated. This is a new generation of tricolor LED dot matrix display where in addition to the usual function of LED display, they concurrently provide audio broadcasting through the visible light rays transmitted by the display panel or assembly.