5x7 matrix led display

Design and Implementation Of
Interfacing Of 5x7 Matrix Led Display To 8051
BY
Ami Goswami (IU1241090014)
Vatsal Shah (IU1241090055)
Department of Electronics & Communication Engineering
Indus Institute of Technology
2014-2015

INDEX
Abstract...................................................................................................................................................3
List of Figures ..........................................................................................................................................4
List of Table.............................................................................................................................................4
Ch. – 1 Introduction ................................................................................................................................5
1.1 Introduction ................................................................................................................................5
1.2 Objective.....................................................................................................................................5
1.3 Scope and Limitation...................................................................................................................5
Ch. – 2 Review of Related Studies of LED matrix....................................................................................6
2.1 Theory of LED dot matrix display................................................................................................6
2.2 Description of LED.......................................................................................................................6
2.3 Dot Matrix vs. 7-segment Display...............................................................................................6
2.4 Advantages of LED ......................................................................................................................7
2.5 Dot Matrix Construction .............................................................................................................7
2.6 Why used dot matrix?.................................................................................................................7
2.7 Definition of LED Driver ..............................................................................................................7
Ch. – 3 Design Specifications ..................................................................................................................8
3.1 What do we need?......................................................................................................................8
3.2 Basic component required..........................................................................................................8
3.3 How does it work? ......................................................................................................................8
3.4 Hardware Design.........................................................................................................................8
3.5 ULN2003A Driver IC ....................................................................................................................9
3.6 Software Description ................................................................................................................10
3.7 Assembly code:........................................................................................................................11
Ch.4 – Procedure and Results...............................................................................................................12
4.1 Procedure..................................................................................................................................12
4.2 Simulation and results ..............................................................................................................14
4.3 Conclusion.................................................................................................................................14
5 References ....................................................................................................................................15

3
Abstract
A 5x7 matrix LED Display board with 8051 microcontroller has been designed. The
LED’s are connected like a matrix with 7 rows of 5 LED’s per each row is designed on a board
to display. For a 5x7 LED matrix, it is impractical to assign one I/O pin per LED, as a 5x7
matrix requires 35 I/O pins. These characters are switched continuously with a delay of
05msec. This design can be extended to number of units by using shift registers to display a
message consisting of many numbers of characters. By controlling the data bits connected to
the LED’s, we can display any character. The 5x7 LED matrix display with 35 LED’s are
arranged in 7 rows and 5 columns structure. The purpose of ULN2003A here is to drive the
column lines of the display. ULN2003A is a high voltage (50V), high current (500mA per
channel) Darlington transistor array. Each IC has 7 channels with individual output clamp
diodes. ULN2003A an active high device, which means logic high must be applied to the input
to make the corresponding output high. The software required for displaying character ‘A’, ‘B’,
‘C’, etc. on the LED matrix, with a delay between each character display has been developed
in assembly of 8051. The hex code is downloaded on to the AT89s51 microcontroller and is
verified by interfacing the microcontroller pins for any given character, a corresponding pattern
of LED is generated and is used to display the character at run time. The application and
advantages that can be used at public transport places like bus stop, railway station, and
airport. Displaying various important messages in hospitals, schools, colleges. In future
development we can use GSM technology to receive the data from remote location.

4
List of Figures
Figure No. Figure Title Page No.
2.1.1 5X7 LED matrix 9
3.1.1 Interfacing 5x7 matrix LED display to 8051 15
3.1.2 ULN2003A drive IC pin configuration and internal logic diagram. 16
3.1.3 LED display 19
3.7 Simulated circuit of 5X7 Display
List of Table
Table No. Table Title Page No.
3.1 Code table 20

5
Ch. – 1 Introduction
1.1 Introduction
Visual impact is most effective mode of influencing human’s minds main aim of
advertisements etc. a display device serves this purpose. A display device is a device
for presentation of information for visual reception, acquired, stored, or transmitted in
various form. The display device is use to display the information on machines, clock,
railway departure indicator and many other devices require a simple display of limited
resolution. The display consist of a matrix of lights or mechanical indicator arranged in
rectangular configuration (other shapes are also possible) such that by switching on or
off the text or graphics can be displayed.
Our initial goal was to create a display that would be useful and interactive in order to
attract attention. In the development of our main goal, the modular LED array, we found
that we would be dealing with three major components,
 Integrated circuits consisting of microcontroller, resistor array, and LED
driver.
 Printed circuit board technologies, as well as software involved in their
design.
 Programming in assembly language to drive the microcontroller and scan
through individual row of LED’s with the data needed to produce a message.
For moving a message on display we design a A dot-matrix display contains 5x7 dots
(LED’s), the LED’s are connected like a matrix with 7 rows of 5 LED’s per each row
and a matrix is designed on a board to display characters.
LED dot matrices are very popular means of displaying information as it allows both
static and animated text and images. Perhaps, you have encountered them at gas
stations displaying the gas prices, or in the public places and alongside
highways, displaying advertisements on large dot matrix panels.
1.2 Objective
The objective of this study is to provide a way of displaying information electronically.
That could result to effectual information dissemination.
1.3 Scope and Limitation
This study is only intended to display information via alphanumeric and commonly used
characters like dot (.), comma (,), etc. which means that it is not capable of showing
animated figures or drawings since the inputs allowed are alphabets, numbers and
special characters only.

6
Ch. – 2 Review of Related Studies of
LED matrix
2.1 Theory of LED dot matrix display
In a dot matrix display, multiple LEDs are wired together in rows and columns. This is
done to minimize the number of pins required to drive them. For example, a 5×7 matrix
of LEDs (shown below) would need 35 I/O pins. By wiring all the anodes together in
rows (R1 through R7), and cathodes in columns (C1 through C5), the required number
of I/O pins is reduced to 16. Each LED is addressed by its row and column number. In
the figure below, if R4 is pulled high and C3 is pulled low, the LED in fourth row and
third column will be tuned on. Characters can be displayed by fast scanning of either
rows or columns.
FIG.2.1 5X7 LED matrix
2.2 Description of LED
Light-emitting diodes (LEDs) are semiconductor devices that illuminate solely by
motion of electrons. When forward-biased, these things emit light. LEDs provide a
cheap and convenient way to display information electronically, fit easily into an
electrical circuit, and are durable.
2.3 Dot Matrix vs. 7-segment Display
LEDs are often arranged in patterns to display information. The 7-segment
configuration of an LED arranged in the form of 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. A 5x7 LED dot matrix is the appropriate device for displaying characters.

7
2.4 Advantages of LED
LED advantages are energy efficient, environmental, produce the intended light
and runs cool. It lights up quickly, fully dimmable, operates silently, and has good
color rendering. One of LED savings is on the carbon dioxide (CO2) emission of
power plant in producing electricity, which helps protect Earth. LEDs are even
better that traditional lighting. Factors like energy savings, energy efficiency and
environmental advocacy.
2.5 Dot Matrix Construction
The two dot matrix configurations are the LED matrix with a common anode for LEDs
in a row - all of the anodes in each row is common, and LED with a common cathode
for LEDs in a row – all the cathodes in each row is common.
2.6 Why used dot matrix?
The dot matrix is the most versatile display in our line of LED displays. It is suitable for
any application that requires numeric, alphabetical and symbolic/graphic information
to be displayed. Choose a smaller pixel size for a crisper message and combine
multiple modules for larger displays. Practically, a LED dot matrix is better than
creating a panel composed of single LEDs because a matrix provides proper alignment
and saves a huge amount of soldering.
2.7 Definition of LED Driver
IC drivers are devices that provide the required current and voltage needed to turn
power switching elements on or off such as LED displays filament lamps including5x7
Dot Matrix Display based on the logic output signals of a digital signal processor (DSP)
and microcontroller or other logic device.
The ULN2003 LED driver is a high voltage, high-current Darlington arrays containing
Darlington pairs with common emitter configuration. Each channel rated at500 mA and
can withstand peak currents of 600mA which can drive wide range of loads including
solenoids, relays, DC motors; LED displays filament lamps, thermal print heads and
high power buffers. Suppression diodes are included for inductive load driving.

8
Ch. – 3 Design Specifications
3.1 What do we need?
 Micro controller based interface using ICAT89S51
 Display size: 8x34 pixels, (26.5.cm) x (5.5.cm)
 Input Power: 8 -12V DC, 500mA
 LED driver interface
 Crystal
 Power-On LED indicator
 Data receiving LED
 Resistors
3.2 Basic component required
 ICAT89S51
 Control Circuit
 Display Board
 Computer
3.3 How does it work?
We need to dump the code which we have written in C compiler into the ICAT89S51,
and later we assemble the control circuit and fix connectors and also the serial port to
pc. Now we setup the software into computer and when we type the messages in the
computer we get the display. This is how it works.
3.4 Hardware Design
:
The Block diagram of 5x7 LED matrix is show in the figure. The 5x7LED matrix display
with35 LED’s are arranged in 7 rows and 5 columns Structure named as display
character as shown in the figure 1. The data is provided to rows and columns through
program loaded in IC1 AT89S51. Now the rows are connected to 89S51 through port
p0.

9
FIG3.1.1Interfacing 5x7 matrix LED display to 8051
3.5 ULN2003A Driver IC
The purpose of ULN2003A here is to drive the column lines of the display. ULN2003A
is a high voltage (50V), high current (500mA per channel) Darlington transistor array.
Each IC has 7 channels with individual output clamp diodes. ULN2003A an active high
device, which means a logic high must be applied to the input to make the
corresponding output high. The input pins are designated as 1B, 2B, 3B, 4B, 5B, 6B,
7B while corresponding output pins are designated as 1C, 2C, 3C, 4C, 5C, 6C, and
7C. The pin configuration and simplified internal logic of ULN2003A is shown in the
figure below.
FIG.3.1.2 ULN2003A drive IC pin configuration and internal logic diagram.

10
3.6 Software Description
The software required for displaying characters ‘A’ on the LED matrix. The hex code
is downloaded on to the 89S51 microcontroller and is verified by interfacing the
microcontroller pins to the pins of the board. For any given character, a
corresponding pattern of LED is generated and is used to display the character at
run time. The equivalent data bytes required for the Display of ‘A’ character were
computed and stored at internal ram address and were transmitted sequentially by
monitoring the TI flag of the SCON register.

11
3.7 Assembly code:
#include <reg51.h>
VoidMSDelay (unsigned int);
sbit R1=P0^0; //Rows connected with Port P0
sbit R2=P0^1;
sbit R3=P0^2;
sbit R4=P0^3;
sbit R5=P0^4;
sbit R6=P0^5;
sbit R7=P0^6;
sbit C1=P1^0; //Columns connected with Port P1
sbit C2=P1^1;
sbit C3=P1^2;
sbit C4=P1^3;
sbit C5=P1^4;
void main(void)
{ while(1)
{
P1 = 0x01; //To print word “EC”
P0 = 0x80;
MSDelay(5);
P1 = 0x02;
P0 = 0xB6;
MSDelay(5);
P1 = 0x00;
P0 = 0x00;
MSDelay(5);
P1 = 0x08;
P0 = 0x80;
MSDelay(5);
P1 = 0x10;
P0 = 0xBe;
MSDelay(5);
}
}
voidMSDelay(unsigned int time)
{
unsignedinti,j;
for (i=0;i<50;i++)
for (j=0;j<time;j++);
}

12
Ch.4 – Procedure and Results
4.1 Procedure
Suppose, we want to display the word ‘EC’. We will first select the column C1 (which
means C1 is pulled low in this case), and deselect other columns by blocking their
ground paths (one way of doing that is by pulling C2 through C5 pins to logic high).
Now, the first column is active, and you need to turn on the LEDs in the rows R1
through R7 of this column, which can be done by applying forward bias voltages to
these rows. Next, select the column C2 (and deselect all other columns), and apply
forward bias to R1,R5 and R7 and so on. Therefore, by scanning across the column
quickly (> 100 times per second), and turning on the respective LEDs in each row of
that column, the persistence of vision comes in to play, and we perceive the display
image as still.
Fig3.1 Display Device
Fast scanning across the
columns results in a steady
display.

13
Table No. 3.1 code
You should have noted that across each row, one pin is sourcing the current for only
one LED at a time, but a column pin may have to sink the currents from more than one
LED. For example, the column C1 should be able to sink the currents from 6 LEDs
while displaying the WORD ‘EC’. A microcontroller’s I/O pin cannot sink this much of
current, so external transistor arrays are required.
ROWCOL C1 C2 C3 C4 C5
R1 1 1 0 1 1
R2 1 0 0 1 0
R3 1 0 0 1 0
R4 1 1 0 1 0
R5 1 0 0 1 0
R6 1 0 0 1 0
R7 1 1 0 1 1

14
4.2 Simulation and results
Simulated circuit to print any word on 5X7 matrix using 8051uC as shown below:
Fig 3.7 Simulated Circuit of 5X7 Display
4.3 Conclusion
The display consists of a dot matrix of lights arranged in a rectangular configuration
such that by switching on or off selected text or graphics can be display. A dot matrix
controller converts instructions from a processor into signals which turns on or off lights
in the matrix so that the required display produced.

15
5 References
 Muhammad Ali Mazidi (2012), The 8051 Microcontroller and Embedded
System, Second Edition, Pearson.
 http://www.circuitstoday.com/interfacing-dot-matrix-led-display-to-8051
 http://www.goodreads.com/author/show/113686.Muhammad_Ali_Mazidi
 http://www.appelsiini.net/2011/how-does-led-matrix-work
 http://www.engineersgarage.com/electronic-components/uln2003-
datasheet
 http://electronics.stackexchange.com/questions/106568/use-of-uln2003-
for-led-current-drive
 http://www.cadsoftusa.com/download-eagle/
 http://www.popularmechanics.com/home/improvement/energy-
efficient/everything-you-need-to-know-about-led-light-bulbs-16542040
 http://accd.vermont.gov/sites/accd/files/Documents/strongcommunities/cd/
mpg/SampleFinalProjectReport.pdf

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