1. ACKNOWLEDGEMENT
My profound gratitude goes to my parents Mr. and Mrs. EMEKA OBIMBA for their
invaluable contribution to my educational pursuit and every others sector of life.
My warm regards goes to my elder brother and his wife and son, MR and MRS
ACHIONYE PROMSE for their support and various suggestions during the writing of
this project, and to my siblings, Christiana,Gift,Esther and Rejoice for their love and
understanding.
I also want to appreciate the efforts of my friends and well wishers who in one way or the
other contributed to my happiness and sustenance during my stay in school.
To my supervisor, Engr Chinenye Uchegbu and Engr Michael Ekwuribe for his
instructions, my lecturers; Engr Kelechi inyama, Engr Stanley, Engr Alozie, Engr
Chiwendu for their numerous teachings and impartation in my life, while an
undergraduate.
And not forgetting Engr Jude Ogbunachi of Daystar Electronix Consort for providing
me with some of the materials needed for the write up of this project and for his
coaching.
Thanks to you all.
2. ABSTRACT
This project focuses on the design and construction of a micro controller based moving
message display. However, since the dot matrix technology is inevitably the underlying
principle of the display system, much attention is focused on it and emphasis is centered
on its streaming effect which employs the scanning method of displaying information
under the hard wired system using the dot matrix arrangement of light emitting diodes in
rows and columns. These light emitting diodes which form a hardware part of the system,
provide a suitable way of displaying the information, radiating light in a specific color
(red). The hard ware structure is interfaced with a programmed microcontroller in order
to achieve the desired information.
3. TABLE OF CONTENT
CHAPTER ONE
INTRODUCTION
1.1 Brief Over View
1.2 Aim And Objectives
1.3 Statement Of Problem
1.4 Work Organization.
CHAPTER TWO
LITERATURE REVIEW
2.1 History of Moving Message Display System
2.2 Scope of Work
2.3 Software Controller Base Display System
2.4 Component and features
CHAPTER THREE
DESIGN METHODOLOGY AND ANALYSIS
3.1 Introduction
3.2 Power Supply Unit
3.3 The Control Unit
3.4 Line Decoders
3.5 Formation of Character Font On The Display
3.6 Construction and Operation
3.6.1 Construction
3.6.2 Operation
CHAPTER FOUR
SYSTEM SOFTWARE
4.1 Micro Controller Program
4.2 A51 Macro Assembly
4.3 Assembling With A51
CHAPTER FIVE
CONCLUSION AND RECOMMENDATION
5.1 Conclusion
5.2 Recommendation
5.3 Reference
4. CHAPTER ONE
INTRODUCTION
1.1 BRIEF OVER VIEW
Recently there has been major advancement in technology. Thee advancement have
spurred to virtually every sector of life. The advertisement industry is no exclusion.
Today sign boards and even bill boards have been gradually replaced by electronic
displays which are more attention catching and flexible.
The moving message display is an electronic system which uses a series of LEDs (light
emitting diodes) to display messages in a moving pattern. Generally, such messages were
scrolled so that they move either from the left to right or vice versa.
However, the LEDs cannot do that alone, thus for full functionality of the moving display
system, the LEDs are connected to either computer or micro – controller which is the
major brain behind the formation and movement of message letter or figures. Moreover,
the computer or micro – controller needs the aid of line decoders, crystal oscillators, semi
conductors components such as transistors, resistors and switches and the power supply
unit for proper implementation.
In this work, I shall be focusing in the design and construction of a moving message
which will display 5 characters at a time, each consisting of 5 x 7 LEDs.
The messages display system will then display the message, “WELCOME TO
ELECTRICAL/ ELECTRONICS ENGINEERING DEPARTMENT
5. 1.2 AIMS AND OBJECTIVE
The aims and objectives of these projects are as follows:
To realize an electronic display system which has some level of flexibility in its
operations that is erasing and re – programming the content stored in the memory
to vary the display output is possible.
To implement in system, whose materials and components used in the design of
the hardware are sample and cheap and easily available in the local market, thus
making the whole system to be simple or design and reducing cost.
To implement open module architecture that can be easily upgraded to suit the
specification of producers and manufacturers.
To make a system operations more appreciable by making the system re –
programmable.
To employ dot matrix arrangement on the display unit so as to allow ease in
expansion of both width and length of the display board.
To design a system which has human – machine inter – face in the operations,
completing transparent and applicable to end – users
1.3 STATEMENT OF PROBLEM
Despite the previous efforts and methods in building moving message displays,
development problems still exist in the realization of ideal electronic displays that is one
that possesses the qualities such as high intensity, contrast, response, resolution, full
color, large capacity, flat form, light weight, low power consumption, low cost and life
time reliability.
In time past, electronic moving message displays were achieved electromagnetically by
the use of relays and these led to a lot of problems with high cost of materials, flexibility
in the way information were presented.
Due to these, I decided to design a project that overcame the above mentioned
limitations.
6. 2.2 SCOPE OF WORK
The scope of this project is to design moving message display system of the type
commonly used in shop windows, airports, fast food venues and other public buildings
The display will be required to be able to scroll a message of at least 300
characters from right to left, with at least five characters on screen at any instant
A dot matrix style of LED display will be used that is capable of displaying the
ASCII character set
To achieve a moving message display with these features: single color, one
brightness level, 7.5 cm by 4.5 cm character size, 5 by 7 dot-matrix module, 1 LED
per pixel.
Other display features (such as flashing) will not be added, since it would be
extremely difficult to add these using ordinary logic ICs
1.4 WORK ORGANIZATION
This work presents the design and construction of a re-programmable electronic moving
message display system using dot matrix arrangements of LEDs. This is presented
through hard wiring which gives a faster response when arranged in modular
configuration, which introduces some level of convenience to the designer.
Chapter one discusses the background information of micro re-programmable digital
display. Chapter two tells the literature review, chapter three describes the design and
methodology, discusses the system software. Chapter five is the concluding chapter
which also proffers future recommendations.
7. CHAPTER TWO
LITERATURE REVIEW
2.1 HISTORY OF MOVING MESSAGE DISPLAY SYSTEM
The advent of MMDSs began in the entry twentieth century by countries like the United
State of America, Germany, Japan and Soviet Union, but huge successes did not
materialize till the 1920s. Still a major problem encountered was how to produce less
bulky MMDSs, However in the 1950s, with the advent of integrated circuit, switches and
large scale integration lower voltage and power consumption, coupled with reduction in
size and weight was achieved.
This contribution to the full construction and usage of MMDS began in the 1960s. AS a
result, there were higher demands for MMDSs in the commercial industry, domestic,
sporting and aesthetic sectors. At this time, passive display technology for liquid crystal
displays (LCDs) and electrochemical display (ECDs) arose at approximately the same
time and active displays for the vacuum florescent display (VFD) and the light emitting
diode (LED) were first implemented for small capacity MMDS.
Series of researches followed as Wolf wt al in 1954, implemented that observation of
Gallium phosphate (Gal) lighting emitting phenomena and the injection
electroluminescence effect of Gallium Arserdie Phosphide (Ga Ar P) red LED in 1968
subsequently colours of LED were introduced, these include orange, yellow and green
types. In the early 1970s, however, the use of programmable dot matrices LCDs or LEDs
were made possible. These could be implemented with the use of keyboard.
Today, the advanced electronic message display system can present multiple view and
objects that have realistic motions.
8. 2.3 SOFTWARE CONTROLLED MESSAGE DISPLAY SYSTEM
This kind of display system uses a computer to control the nature and movement of
messages. There is no need for a microcontroller since the control basically comes from
the computer’s microprocessor, which has powerful processing powerful capability. The
message system is controlled with the aid of application software that drives it.
The message board is usually connected to the computer with the aid of a serial or
parallel interface. This interface could be a virtual or physical link between the computer
and its peripherals through which compatibility is achieved.
2.4 MICRO-CONTROLLER BASED MESSAGE DISPLAY SYSTEM
In this kind of display system, a micro-controller is used to control the display of
messages on the dot-matrix LEDs which it is interfaced with. They are usually costumed
made or designed to carry about the logic needed to generate required lighting sequences
and output them to the display. The logic is usually available as a firmware in the
Erasable Programmable Read Only Memory (EPROM), which is then interfaced to the
appropriate display.
Advantages of a micro controller based display system include: greater flexibility, ability
to implement very complex logic at no extra hardware cost ability to receive inputs
dynamically and displays them. Cheap, memory can be erased and reprogrammed.
This is the method employed in this project, the versatility was adequately employed.
9. CHAPTER THREE
DESIGN METHODOLOGY AND ANALYSIS
3.1 INTRODUCTION
This project is designed so as to realize an efficient, maintainable, and most importantly,
affordable electronic re-programmable display system using dot matrix technology. The
moving message display system is designed in modules, which involves the techniques of
modularity. For simplicity, the suitability and compatibility of a stage to conform to the
changing circuit parameters in other stages were considered. Another important step
taken was early identification of hazards and the development of appropriate steps to
isolate and control them in the design phase. The different section/modules that make up
the whole system are shown below.
Block diagram of a Micro programmable moving message display system showing
its principle of operation.
10. 3.2 THE POWER SUPPLY UNIT
The power supply unit is a system that supplies electrical or other types of energy to an
output or group of loads.
The power supply unit is a system that supplies voltage to all parts of a circuitry. There
are basically two main types of power supplies – linear power supply and switched mode
power supply.
In this project, the linear power supply was used principally the linear power supply
consists of four sections. Complete implementation. They include:
1. Transformation
2. Rectification
3. Filtration
4. Regulation
A typical block diagram of the linear power supply unit is as shown
below.
Block diagram of the power supply unit
TRANSFORMER RECTIFIER FILTER REGULATOR
11. THE TRANSFORMER
In this project, a 240/12V, 500MA based transformer is used based on the fact that the
means supply is rated at 240V and the actual voltage required by the circuit components
(micro – controller, line decoder LEDs etc.) is a regulated 5V
However, a 7805 regulator is used which required a minimum of 8V. The back drop
voltage from the regulator is 1.4v given a total of 9.4V. The 12V transformers are
available. A current of 500mA is sufficient to drive all the circuit components.
THE RECTIFIER
A rectifier is an electrical device that converts alternating current (AC) to direct current
(DC), a process known as rectification.
Rectification can either be half wave or full wave.
Half – Wave Rectification
In half – wave rectification, either the positive or negative half of the AC wave is passed,
while the half of the other is blocked.
Full – Wave Rectification
A full wave rectifier converts the whole of the input form if the inputs wave form to
constant polarity at its output.
In this project, full wave bridge rectifier is used because it provides a better efficiency
compared to half wave and bridge rectifier, because the transformer used not center
tapped.
FILTER
12. Filters are electronic circuit which perform signal processing functions, specifically to
remove unwanted frequency component from the signal to enhance wanted ones or both.
They consist of a capacitor connected across the rectified output for the purpose of
smoothening out the unwanted ripple in the output. The capacitors basically store charges
temporarily and the stored charges are measured in farad, micro – farad and pico – farad.
The Regulator
A voltage regulator is an electrical regulator designed to automatically maintain a
constant voltage level. It may use an electromechanical mechanism, or passive or active
electronic component. Depending on the design, it may be used to regulate one or more
AC or DC voltages.
The voltage regulator used in this project is 78HC05 integrated circuit. It has three
terminals and is capable of supplying 5+ 10% at 100Ma
]
1 3
2
Circuit symbol of a voltage regulator with pin out indicator
Terminal 1 serves as the input. 2 serves as ground and 3 as the input terminal.
The 7805 used takes 12V from the transformer and gives output of 5V± 0.2%.
Power Indicator
Diode D5 is a light emitting diode used as power on indicator. This glows once power is
on. Resistor R1 is a circuit-limiting resistor, which helps to limit the amount of current
flowing through the diode D5.
U 1
78105
13. The value of the limiting resistor is gotten by the expression.
Resistor R1 = (Vdc – Vd)
Imax
Where:
Vdc = the calculated dc voltage which is given by
Vdc = Vac √2
= 12* √2
Vdc = 16.97
Vd = Diode voltage drop = 1.7V
I2 = Maximum circuit rating of the LED (D5) = 20Ma
Value of the limiting resistor becomes
R1 = 16.07 - 1.7
20 * 10
R1 = 763.5Ω
Therefore for safety reasons, a value of 1000Ω or 1KΩ which is a little higher than
763.5Ω is used to take care of inconsistencies.
3.3 THE CONTROL UNIT
The control unit is made up of a single micro controller chip that can execute a user
program, normally for the purpose of controlling the device; the transistors serve as
switches and the line decoders.
ATMEI 8951
The ATMEI 8951 is a single chip micro-controller that has random access memory
(RAM) and read only memory (ROM). It has instruction set and is compatible with any
other MC51 controller family.
The RAM (Random Access Memory) – This consists of 128 byte arranged as four
register bank, each containing 8 registers given the label R0 to R7.
The ROM (Read Only Memory) – The 8951 has 4K bytes ROM. This portion of the
8951 is made available for the storage of program written by the system designer. The
operation of the 8951 depends on the program.
14. Serial Communication Ports/Pin Configuration- The 8951 micro-controller is a 40 pin IC
with basically four communication ports with pin 20 and 40 as ground and voltage supply
respectively. The four communication ports are ports are port 0, port 1, port 2 and port 3.
This is illustrated in the fig below.
Diagram of 8951
ALE/PROG: Address latch enable output pulse latching the low byte of the address
during accessory to external memory. ALE is emitted at a constant rate of 1/6 of the
oscillator frequency for external timing or clocking purposes even when there are no
accesses to external memory. This pin is also the program pulse input (PROG) during
EPROM programming.
PSEN: Program store Enable is the read strobe to external program memory. When the
device is executing out of external program memory, PSEN is activated twice each
machine cycle (except that two PSEN activation are skipped during access to external
Data Memory). PSEN is not activated when the device is executing out the internal
program memory.
15. EA/VPP: When EA is held high, the CPU executes out of external program memory.
Holding EA low forces the CPU to execute out of external memory regardless of the
program counter value.
XTAL1: Input to the inventing oscillator amplifier
XTAL2: Output from the inverting oscillator.
PORT 6: Port is an 8 bit drawn bi – directional port. As open drawn output port, it can
sink eight LS TTL loads. Port ) pins that have 1s written to them float and in that state
will function as high impedance inputs. Ports 0 is also the multiplexed lower – order and
data bus during access program and data memory.
PORT 1: Port 1 is also 8 bit bi – directional I/O port with internal pull – ups. The port 1
output buffers can drive TTL inputs. Port 1 pins that have 1s written to them are pulled
high by the internal pull – ups, and in that state can be used as inputs, ports 1 pins that are
externally being pulled low will source current because of the internal pull – ups.
PORT 2: Port 2 is an 8 bit bi – directional I/O port with pull – ups. Port 2 emits the high
order address byte during accesses to external memory that use 16 bit addresses.
PORT 3: Port 3 is an 8 bit bi – directional I/O port with internal pull ups.
VCC: Supply voltage
VSS: Circuit grounded potential
LINE DECODERS
Binary Decoder
It is basically, a combinational type logic circuit that converts the binary code data at its
input into one of a number of different output lines, one at a time producing an equivalent
decimal code at its output. Binary Decoders have inputs of 2-bit, 3-bit or 4-bit codes
depending upon the number of data input lines, and a n-bit decoder has 2n output lines.
Therefore, if it receives n inputs (usually grouped as a binary or Boolean number) it
activates one and only one of its 2n outputs based on that input with all other outputs
16. deactivated. A decoder’s output code normally has more bits than its input code and
practical binary decoder circuits include 2-to-4, 3-to-8 and 4-to-16 line configurations.
A binary decoder converts coded inputs into coded outputs, where the input and output
codes are different and decoders are available to "decode" either a Binary or BCD (8421
code) input pattern to typically a Decimal output code. Commonly available BCD-to-
Decimal decoders include the TTL 7442 or the CMOS 4028. An example of a 2-to-4 line
decoder along with its truth table is given below. It consists of an array of four NAND
gates, one of which is selected for each combination of the input signals A and B.
2-to-4 Binary Decoders
A binary decoder converts coded inputs into coded outputs, where the input and output
codes are different and decoders are available to "decode" either a Binary or BCD (8421
code) input pattern to typically a Decimal output code. Commonly available BCD-to-
Decimal decoders include the TTL 7442 or the CMOS 4028. An example of a 2-to-4 line
decoder along with its truth table is given below. It consists of an array of four NAND
gates, one of which is selected for each combination of the input signals A and B.
2-to-4 Binary Decoders
In this simple example of a 2-to-4 line binary decoder, the binary inputs A and B
determine which output line from D0 to D3 is "HIGH" at logic level "1" while the
remaining outputs are held "LOW" at logic "0" so only one output can be active (HIGH)
at any one time. Therefore, whichever output line is "HIGH" identifies the binary code
present at the input, in other words it "de-codes" the binary input and these types of
binary decoders are commonly used as Address Decoders in microprocessor memory
applications.
17. Some binary decoders have an additional input labelled "Enable" that controls the outputs
from the device. This allows the decoders outputs to be turned "ON" or "OFF" and we
can see that the logic diagram of the basic decoder is identical to that of the basic
demultiplexer. Therefore, we say that a demultiplexer is a decoder with an additional data
line that is used to enable the decoder. An alternative way of looking at the decoder
circuit is to regard inputs A, B and C as address signals. Each combination of A, B or C
defines a unique address which can access a location having that address.
In this simple example of a 2-to-4 line binary decoder, the binary inputs A and B
determine which output line from D0 to D3 is "HIGH" at logic level "1" while the
remaining outputs are held "LOW" at logic "0" so only one output can be active (HIGH)
at any one time. Therefore, whichever output line is "HIGH" identifies the binary code
present at the input, in other words it "de-codes" the binary input and these types of
binary decoders are commonly used as Address Decoders in microprocessor memory
applications.
Some binary decoders have an additional input labelled "Enable" that controls the outputs
from the device. This allows the decoders outputs to be turned "ON" or "OFF" and we
can see that the logic diagram of the basic decoder is identical to that of the basic
demultiplexer. Therefore, we say that a demultiplexer is a decoder with an additional data
line that is used to enable the decoder. An alternative way of looking at the decoder
circuit is to regard inputs A, B and C as address signals. Each combination of A, B or C
defines a unique address which can access a location having that address.
Sometimes it is required to have a Binary Decoder with a number of outputs greater than
is available, or if we only have small devices available, we can combine multiple
decoders together to form larger decoder networks as shown. Here a much larger 4-to-16
line binary decoder has been implemented using two smaller 3-to-8 decoders.
18. 4-to-16 Binary Decoder Configuration
Inputs A, B, C are used to select which output on either decoder will be at logic "1"
(HIGH) and input D is used with the enable input to select which encoder either the first
or second will output the "1".
Binary Decoders are most often used in more complex digital systems to access a
particular memory location based on an "address" produced by a computing device. In
modern microprocessor systems the amount of memory required can be quite high and is
generally more than one single memory chip alone. One method of overcoming this
problem is to connect lots of individual memory chips together and to read the data on a
common "Data Bus". In order to prevent the data being "read" from each memory chip at
the same time, each memory chip is selected individually one at time and this process is
known as Address Decoding.
In this application, the address represents the coded data input, and the outputs are the
particular memory element select signals. Each memory chip has an input called Chip
Select or CS which is used by the MCU to select the appropriate memory chip and a logic
"1" on this input selects the device and a logic "0" on the input de-selects it. By selecting
or de-selecting each chip, allows us to select the correct memory device for a particular
address and when we specify a particular memory address, the corresponding memory
location exists ONLY in one of the chips.
In this project the work of 74ls138 is working as a master for chip selection its input is
come from microcontroller and its output is used for chip selection its output is active
low so as a low signal is applied on the 18 or 19 pin of 4*16 decoder it activated and get
19. start working. When a port 1 value is 16 then first 74ls154 is disabled and other is
enabled.
Here A0, A1, A2 and A3 are the inputs of the 74ls154. Its output is active low .E0 and E1
are two inputs for enabling the ic. I ground a pin 19 and pin 18 is controlled by the
74ls138 to enable it at a specific time. It should not be on at every time.
The 74138 line decoder is a high performance memory decoding or data-routing IC that
requires a very short propagation delay times. The 74138 decodes one of the seven lines
depending on the conditions at the three binary SELECT INPUTS and the three
ENABLE INPUTS.
20. 3.5 FORMATION OF CHARACTER FONT ON THE DISPLAY
Use of fonts.exe
This exe files can be used to generate a 7*5 (7 rows*5 column) fonts size pattern in
hardware..
In the above diagram row 6,7 and 8 has code 00h mean no display by using 8*8 just one
00h is used if use three 00h the gap is seems too much between two characters.
Below is the screen shot of fonts.exe that how I use it, it has many formats and option to
do as I check three boxes and then generate a font’s pattern code.
21. Dot matrix internal structure:
In the above diagram rows are supplied by 5 volt and ground provided at column then led
glow.
I am using the same pieces it is called common cathode configuration.
22. 3.6 CONSTRUCTION AND OPERATION
3.3.1 CONSTRUCTION
The construction of the moving message display system was done in such a way that
connections followed the circuit diagram. The LEDs were connected anode to anode and
cathode to cathode in a 7 by 25 format so that the system can display 5 characters at a
time, each comprising of 7 by 5 LEDs. Thus each letter is typified with 7 LEDs on the
vertical axis and 5 LEDs on the horizontal axis.
The connection of LEDs is interfaced with the micro controller and four line decoders
which control the display and movement of messages.
The system’s internal circuit is connected in such a way that every unit except the
transformer is mounted on the same circuit board. This was done to minimize the weight
of the message display system.
The casing is 2.5 ft by 6 ft. and a total number of 210 LEDs were used in order to display
five letters at a time. A reddish translucent glass was used in order to make the display
visible and attractive.
23. 3.3.2 OPERATION
When the system is powered on, the powered supply unit provides the voltage (5V)
necessary to power the micro controller, the LEDs and other circuit element. The micro –
controller receives 5V from pin 1 with pin 20 grounded, begins to execute programmes
from its internal memory. As a result of this, data signals are sent from the micro –
controller port 1 to the input pins of the eight line decoders and clock signals are sent to
their clock input pin from port of the micro – controller. At the same time, base biased
signals are sent to the bases of the transistors from the micro controller’s port 2.
Immediately the line decoder receives the clock signals from micro – controller, the
decoders transfers their data to other output pins, which are connected to the cathode of
the LEDs. Also when the transistors receive their base bias currents from the micro
controller they switch power to the LEDs, since they are wired to the anode of the LED
array. At this time, LED will only grow if its anode is positive with respect to the
cathode. Thus, by controlling the system sent to the decoders and transistors, the micro –
controller controls LED which needs to be on/off for the device to achieve the display.
24. CHAPTER FOUR
4.1 COMPONENTS AND FEATURES
List of components part Quantity
Resistors
R1 1
R2 1
R3.1 – 8 8
CAPACITORS
C1 1
C2 1
C3 1
C4 1
TRANSISTORS
T1 – 8 8
LEDs 210
DECODER 1
ICs’ 3
MICRO – CONTROLLER 1
AT89C51 Micro – controller 1
RESISTORS
A resistor is a two terminal electronic component that produces a voltage across its
terminals that is proportional to the electric current passing through it in accordance to
ohms law.
TRANSISTOR
This is a semi – conductor device commonly used to accomplish or switch electronic
signals. A voltage or current applied to one pair of the transistor’s terminals changes the
25. current following through another pair of terminals changes the current following through
another pair of terminal. The transistor provides an amplification of signal.
LIGHT EMITTING DIODES (LEDs)
LEDs from the numbers on digital clock transmission from remote controls, light up
watches, etc. They are tiny bulbs, but unlike ordinary incandescent bulb, they don’t
filament that will burn off and they don’t get hot. They are illuminated solely by the
movement of electron in a semi – conductor material and they last just as long as a
standard transistor.
LINE DECODERS
Decoders are collection of logical gates, which are arranged in a specific way so as to
break down any combination of inputs to a set of terms that are all set to 0 apart from 1
term.
MICR-CONTROLLER
This is a single programmable chip that is designed to control circuits that are interfaced
with it. They usually consist of ports and other activation pins having specific functions.
There are of various families including the 8086, 8088, 8951 series.
INTEGRATED CIRCUIT
also called microelectronic circuit or chip, an assembly of electronic components,
fabricated as a single unit, in which miniaturized active devices (e.g., transistors and
diodes) and passive devices (e.g., capacitors and resistors) and their interconnections are
built up on a thin substrate of semiconductor material (typically silicon). The resulting
circuit is thus a small monolithic “chip,” which may be as small as a few square
centimeters or only a few square millimeters. The individual circuit components are
generally microscopic in size.
CAPACITOR
(originally known as a condenser) is a passive two-terminal electrical component used
to store electrical energy temporarily in an electric field. The forms of practical capacitors
vary widely, but all contain at least two electrical conductors (plates) separated by a
dielectric (i.e. an insulator that can store energy by becoming polarized). The conductors
can be thin films, foils or sintered beads of metal or conductive electrolyte, etc. The
nonconducting dielectric acts to increase the capacitor's charge capacity. A dielectric can
be glass, ceramic, plastic film, air, vacuum, paper, mica, oxide layer etc. Capacitors are
26. widely used as parts of electrical circuits in many common electrical devices. Unlike a
resistor, an ideal capacitor does not dissipate energy. Instead, a capacitor stores energy in
the form of an electrostatic field between its plates.
CRYSTAL OSCILATOR
is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal
of piezoelectric material to create an electrical signal with a very precise frequency.[1][2][3]
This frequency is commonly used to keep track of time (as in quartz wristwatches), to
provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for
radio transmitters and receivers. The most common type of piezoelectric resonator used is
the quartz crystal, so oscillator circuits incorporating them became known as crystal
oscillators,[1] but other piezoelectric materials including polycrystalline ceramics are used
in similar circuits.
4.2 SYSTEM SOFTWARE
Micro- controllers Program
In this project, the program used is assembly language. Assembly language is a low key
programming language that makes use of mnemonics or symbols to program the
computer. This makes the assembly language user-friendly, since it is easier for a user to
remember programming symbols which are far easier than complex machine codes.
However, it employs a utility program that translates its symbols into a form that is
readable by the computer’s machine. The assembly language is usually employed in the
programming of computers, microprocessors, microcontrollers and even integrated
circuits. They implement a symbolic representation of the numeric machine codes and
other constants needed to program a particular CPU architecture.
The utility program called the assembler is used translate assembly language into the
target computer machine code. In this project however, the assembler used is the A51
Macro Assembler.
4.3 A51 MACRO ASSEMBLER
The A51 assembler is an Intel ASM51-compatible macro assembler for the 8051 family
of microcontrollers. The A51 assembler translates symbolic assembly language
mnemonics into relocatable object code where utmost speed, small code size, and
hardware control are critical. The macro facility speeds development and conserves
maintenance time, because common sequences need be developed only once. The
assembler supports symbolic access to all features of the 8051 and is configurable for
each 8051 derivative.
The A51 assembler translates an assembler source file into a relocatable object module. If
the DEBUG control is used, or if the “Include debugging information” option is checked,
27. this object file will contain full symbolic information for debugging with the WinSim-51
debugger/simulator or an in-circuit emulator. The A51 assembler generates a list file,
optionally with symbol table and cross references. The A51 assembler is fully compatible
with Intel ASM51 assembly programs.
4.4 Assembling with A51
This chapter explains how to use the A51 assembler to assemble 8051 assembly source
files and discusses the assembler controls that you may specify on the command line and
within the source file.
Using the controls described in this chapter, you can specify which operations are
performed by A51. For example, you may direct the A51 assembler to: generate a listing
file, produce cross reference information, and control the amount of information included
in the object file. You may also conditionally assemble sections of code using the
conditional assembly controls.
Running the Assembler
First the ASSEMBLER is invoked by selecting TRANSLATE, MAKE, or BUILD ALL
from the Project menu in preview. The TRANSLATE command will assemble only the
source file that is selected in the project window. The MAKE command will compile and
link all changed files in the project. The BUILD ALL command will compile, assemble
and link all of the files in the project.
To invoke the Assembler, you enter A51 at the DOS prompt. The command line must
contain the name of the 8051 assembly source file to be assembled as well as any
required command-line controls. The format for the A51 assembler command line is:
A51 sourcefile controls…
where sourcefile is the name of the source program you want to assemble. The A51
assembler controls are used to direct the operation of the assembler. Refer to the
“Assembler Controls” section later in this chapter for more information.
SYSTEM PROGRAM
org 00h
call gap
call shift
call shift
call shift
call shift
call shift
call shift
start: call capw
40. mov 49,#49h
mov 50,#49h
mov 51,#49h
mov 52,#49h
ret
capu:MOV 48,#3fh
MOV 49,#40h
MOV 50,#40h
MOV 51,#40h
MOV 52,#3fh
ret
GAP:MOV 48,#00H
MOV 49,#00H
MOV 50,#00H
MOV 51,#00H
MOV 52,#00H
ret
end
SYSTEM INTEGRATION
Usually before a system is developed, other subsystems are brought together in such a
way as to achieve a singular purpose. In this piece of work, the case is not different.
Subsystems were designed and integrated to each other. The hardware and the software
are interwoven to realize a desired result. They must be compatible for there to be a
smooth protocol or receiving and processing of the information.
TEST PLAN
To verify the functionality of various subsystems, a test plan is adopted. Here, we are
using a module by module testing plan. This is necessary to ensure the smooth operation
of the project work. The plan helps to detect any abnormality should there be any
malfunctioning.
MODULE BY MODULE TESTING
1. POWER UNIT TESTING: this unit comprises the transformer, bridge rectifier,
filtering capacitor and a voltage regulator. All electronic gadgets use a DC voltage
source. In this work, TTL (Transistor Transistor Logic) was used, hence the need
to use 5Volt source. The regulator 7805 stabilizes the DC voltage to +5V. At the
end of the construction, the test was ok. This unit is very vital in any electronic
circuit in that it supplies the required energy to each module.
41. 2. DEMULTIPLEXERS AND LINE DECODERS
It operates on a principle of causing the output that corresponds to the binary
input to go LOW. At each binary input, the output pins respond only if the enable
pins are activated. The line decoder has a tristate capability. Therefore its
operation is dependent on the activation pins and the supply of the binary codes at
the input pins.
3. PROCESSING UNIT TEST
This is tested based on its connection to other subsystems. It is the unit that
establishes control over all other subsystems. The test has to include the software
programs written to drive the hardware. More still, simulation software could be
used to debug the program to verify its workability and compatibility to other
modules.
CONTROL SYSTEM TESTING
The control is provided by a microcontroller based on the software program
burned into it. It is expected to switch each lamp at appropriate time and also
switch them OFF when it is desired. After the design, the software drives the
hardware as expected and is working quite well.
USER MANUAL AND PRECAUTION
It is expected that the user must have read this manual before operating this
system.
Operation procedure:
1. Connect the mains plug to the mains.
2. Switch ON the system
3. Change the direction of the traffic by pressing the appropriate button. Do
not press any if you wish not to change the direction of traffic.
4. Do not open the casing to avoid electric shock. For services, take to a
registered service personnel.
42. 5. Switch OFF the system when it is not in use.
PROBLEMS ENCOUNTERED
In the course of carrying out this project, several problems were encountered
First, sourcing for materials was pretty difficult as most of the circuit elements could not
be found in neighboring markets. Traveling out town to get them was the only solution.
Second, during the course of building, some components got damaged. Such damage
could be allotted to over-heating during soldering, careless handling, environmental
distortions and even incompetence of manufacturing.
Third, due to wrong connection on one occasion, a fault arose, leading to the demand for
trouble shooting which was time consuming and stressful.
Fourth, due to my non conversance with this project, a lot of errors where registered in
programming which had to be debugged for the program to run accurately.
43. CHAPTER FIVE
CONCLUSION AND RECOMMENDATION
5.1 CONCLUSION
The digital electronic message display system has been modernized with sophisticated
electronic devices, which center on the urgent needs in our advertising industry. They
provide various applications in different aspects of our economy such as banks, airports,
restaurants, superstores, institutions, entertainment, stock exchange market and
directional venue guides.
The light emitting diodes which constitute of the hardware system is mainly used to
display alphanumeric characters and symbols in various systems such as digital clocks,
microwave ovens, stereo tuners and calculators.
The design of moving massage display systems have a single micro- controller chip
which provides 8 kilobytes of flash, 256 of ram, 31 input/output lines, three 16 bit timer
counters, six vector two-level interrupt architecture, full duplex serial port, on chip
oscillator and clock that provides the necessary control and flexibility of display.
5.2 RECOMMENDATIONS
The design of a micro controller based moving message display system has characters
showing five pages at a time. There is a great need for future design and implementations
to cater for animations and symbols.
Again, plasma display panels may be used in place of light emitting diodes to
accommodate certain areas of our economy that may require large display board for
advertisement.
There is significant need for future design to include a universal serial bus of a serial
interface that was used for the same purpose.
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