Description

Interfacing LED Dot Matrix with Microcontroller

An LED dot matrix display consists of a matrix of  LED’s arranged in a rectangular configuration. The desired character or graphics can be displayed by switching ON /OFF  a desired configuration of LED’s. Common display configurations available are 7×5, 8×8, 7×15, etc. LED dot matrix can be used in simple display applications where the resolution is not a big concern.  The figure below shows the arrangement of LEDs in a typical 7×5 dot matrix display.Any individual LED or a group of LEDs in the matrix can be activated by switching the required number of rows and columns.

Working

Light-emitting diodes (LEDs) provide a cheap and convenient way to display information electronically. LEDs are tiny light sources that are illuminated solely by the movement of electrons in semiconducting materials. They emit light when forward-biased, fit easily into an electrical circuit, and are durable. LEDs are often arranged in patterns to display information. The seven-segment configuration of an LED arranged in the form of the digit 8 can be restrictive in that it does not adequately allow the display of some alphanumeric characters. By contrast, the versatility of a dot-matrix arrangement allows an LED unit to display complicated shapes.

Stable Character

This diagram is for practice and programming, wants you have it working you can put transistors and resistors on. Here we put the letter A on the display as you can see in video, using a breadboard.       Let’s understand how it works. First connect row and column to the microcontroller PORT P3 and PORT P2 respectively. Then by using programing sends data to first column and at same time sends data to row and then after some milli-seconds change the column and send data to row again. And do this till last column and then repeat it again and again around speed of greater then 20 frame per second.

Moving Character

How to scroll a character across the display? The trick is to build one character on the display by scanning the columns very fast, and let say each 20 times (20 frames) scroll it one position to the left, this will give the effect of a walking text across the dot-matrix display. So first build one frame, repeat this 20 times, and after that, read the data one address later, if you do this 5 times (5 columns) the character scroll from right to left from the display. (The refresh goes so fast that your brain can’t keep up, and what you see is the A scrolling over the display