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MOVING MESSAGE USING DOT MATRIX DISPLAY

MOVING MESSAGE DISPLAY USING uController AND 5x7 DOT MATRIX DISPLAY

INTRODUCTION:
In day-to-day life, in many public places, like hotels, government offices; we come across a number of situations wherein there are scrolling messages being displayed; which give information about the products or services being rendered at that particular business spot or office. Such a method of displaying information so as to be visible to all the people at once is easier than asking the queries at the reception. Thus, the most commonly used displays for such purposes are the DOT MATRIX DISPLAYS.

These displays facilitate easy understand of the matter and it can be made more efficient by making the message to scroll from right to left thereby creating a sense of a continuous message being displayed to the consumer.
This project uses the Philips P89C51RD+ Micro-Controller with 5x7 Dot Matrix alphanumeric programmable display to create a marquee style moving message display. The custom message scrolls from right to left facing the display..

Multiple modules of 5x7 Dot matrix display are interfaced with the Micro controller and using efficient coding, the required message can be displayed.

EXPLANATION OF THE BLOCK DIAGRAM:
The Micro controller IC P89C51RD+ is interfaced with array of 5x7 Dot Matrix display module. The output ports of the micro controller are connected to all the display units. As it is a 5x7 display; there are 35 LED’s on each module of the display. Thus, we require 35 lines from the output ports of the micro controller which are obtained from the Ports 0,1,2 and 3 of the Micro controller. If required some other circuits like decoder can also be used to obtain the required output at the port. Corresponding to each output from the port, a particular LED in the 5x7 matrix will glow. Thus by software, we program a particular set of LED’s to glow whenever a particular character is to be displayed. Thus, the viewer gets the sense of a particular character being displayed, which combined with other characters displays a meaningful message. The µC is programmed using C code to scroll the given string of message.
There are also select lines being used for each module of display to select the unit that is to be glowed at a particular time. The logic used is known as MULTIPLEXING.

In this method, only a particular unit is active at a time. For example, if we want to display “HELLO” in the units. Then first, the code for H will be sent at the ports and the first unit of display will be selected so as to display “H” in the first unit, and all other units are blank as they are not selected. After some time, the code for 2nd character “E” is sent to the data lines, and the 2nd unit is selected so as to display “E”, all other units being blank as they are not selected. This process is repeated continuously at a very fast rate, and hence due to the persistence of vision, the viewer doesn’t see the flickering of characters, instead reads the message as a whole “HELLO”.

APPLICATIONS:
(1) Generally used for advertisement purposes in public areas.
(2) Railway Reservation and announcement systems for arrival and departure time display of trains.
(3) Timer in traffic signals, token number display in hospitals, and in various other places.It can be used for creating Games like the brick-game,etc.

This project has been undertaken as a part of the VIth semester project. My partner for this project is Mr. Kapish M. Joshi.