Interfacing LED Dot Matrix Display with PIC16F887 Microcontroller

Abstract

This research work is to design and implement six English letters, which stand for the name of our Degree College, Nationalities Youth Resource Development Degree College, NYRDDC. The letters are made up of acrylic sheets, PVC sheets and aluminum foils. Each letter box is 35 inches tall, 24 inches high and 4 inches deep. The ratio of the front surface area of each letter is A4 size ratio and letter font is Arial Black. The front surface is made holes though which LEDs are put into. In each letter, LEDs are arranged into a matrix of 24 rows and 16 columns. LEDs in each row is connected in parallel. All anode terminals from 24 rows are connected together as a common anode. So, the design of each letter is 24 rows and 1 column. Since there are six letters on the display board, the design of the whole system is [24 × 6] LED-dot-matrix. The length of the diameter of each LED is 9 mm and power dissipation for each is 0.12. W (12 V × 10 mA). There are 1361 LEDs in the display system. The maximum number of LEDs lighting on at a time is 100. The power of the constant current source is 12 V- 30 A. The sourcing driver IC for anode side is TD62783APG and the sinking driver is ULN2803APG. The two drivers are from Toshiba’s products. The control device is PIC16F887 microcontroller. LEDs display is controlled with microcontroller and scanned by rows and columns. The programming language is PIC Assembly Language. In each operation, eight rows of the matrix are first set HIGH and then one column is set HIGH. After 1 millisecond (ms), that column is set LOW and successive next column is set HIGH again and again. For a complete cycle of the whole display system, number of processing is 18 and LED-ON-time is also 18 ms. So, the scanning rate is 55 Hz. The result is acceptable with the Persistence of Vision.