AN ELECTRONIC DIGITAL DISPLAY SYSTEM
CHAPTER ONE
1.0 INTRODUCTION
In modern
times, the use of solid state materials has helped man enjoy his existence by
the wonderful innovation in the world of electronics. One major development
that has made possible the enormous advancement in solid state technology is
the digital revolution. Circuits are designed to implement the basic
digital logic functions fundamental to all digital systems. Digital
electronics therefore compasses the design, manufacture, and use of circuits
for processing information in digital form (Obiechine, et al., 2013). An information
display is a way of providing information object for promotion. It can be seen
in a form of cardboard or tarpaulin at stores/shops, streamers and electronic
display devices. The advent of new technologies made the information display in
form of Electronic displays most common nowadays especially for advertisements
and promotions (Wilbert, 2007). The development of information display
electronic
based system has covered numerous technologies since its beginnings
(Gowrishankar, Mritha, & Chandra, 2014). Display technologies have been
developed for many years. In the late twentieth century, cathode Ray Tube
(CRT) dominated the market. However, new trends in display include the
demand of picture quality, size and power consumption. So, Liquid Crystal
Display (LCD) is then emerging to be the current market. Due to their relatively
light weight, low operating power and compact design, LCD has become a popular
part of home entertainment system and it continues to dominate the existing
market (Chan, Cheungkaki, & Mak, 2011). Traditional LCD requires colour
filter to display full
color. Electronic display devices nowadays are mostly controlled by a microcontroller.
And the semiconductor that gives out light like an LED has been a great breakthrough
in electronic display (Baron, 2011). Field
Sequential Color of LCD (FSC-LCD) generates full color without color
filters, with the use of colour addition. Despite
existence of numerous implementation of
embedded system coding, designing a digital sequential display system
(DSDS) is still considered as one of the innovative implementation
(Bhagyashree, 2009). This
technology (DSDS) can be found in a number of places and are being used
for different purposes. In banks, it is used to display interest rates as well
as exchange rates, in hotels and pubs; it is used to display menu and prices
(Obiechine, Don, & Uche.V, 2013). The extent of development in
information dissemination has made it possible that the well-known method of displaying
information using sign posts, placards, notice boards, etc. has to be modified
by using electronic information board. In previous years, the means by
which adverts, information, etc., are made has been through the method
of the digital display board. But the use of static mode of sign display such
as banners, flyers etc. are becoming boring and unattractive. The new technologies
of the digital age have made possible the use of programmable and
reprogrammable electronics display to provide solutions to this kind of problem
(Obiechine, Don, & Uche.V, 2013). National Open University of
Nigeria (NOUN), Ado-Ekiti centre does not have a welcome digital display as at
the time of this
research work; therefore, it is pertinent to design a digital display in
order to fulfill this need.
A brief history of Digital
Billboards and the tech behind them.
JG
Ballard Digital Billboards Atlanta In 1963, author J.G. Ballard predicted the
use of enormous electric signs to entice people to “buy now” in a short story
entitled, The Subliminal Man. Today, digital billboard advertising is very much
a reality utilized by small and large corporations across the country. According
to the Outdoor Advertising Association of America, digital billboards made
their first actual appearance in 2005 as both screen and Internet technology
became available to make the remote loading of files possible onto a
billboard-sized screen. However, prior to the first electronic billboard,
digital place-based screens had been in use since the 1990’s. The science
behind how electronic billboards work is pretty simple: advertising messages
rotate every six to eight seconds on an LED screen. Controlled remotely, this
advertising option is best-suited for companies in need of more flexibility in
their ad messaging. Created in a similar way to ads on traditional billboards,
the key difference is in ad delivery. Digital billboard advertising is sent out
as a simple .JPEG file rather than printed and pasted directly to the
billboard.
1.1 Background of the study
Electronic
digital display system as used in this reports refers to a sign that uses
electronic hardware and software to display its copy, messages or images. Also,
a sign utilizing a fixed light source to provide a message in text, images
pictures, and or symbols that may appear to move or may appear as on/off
messages. This is contrast to traditional non-electronic signs where the copy
displayed is physically applied to the sign surface by printing, painting or
otherwise attaching it onto the sign. The materials or substrate to which the
copy is applied is typically paper, wood, plastic or the wall of a building. In
this modern time, solid materials have helped man to show that he really exists
by doing wonders in the world of electronics. One major development, made
possible by the enormous advances in solid state technology, is the “digital
revolution”. Circuits are designed to implement the basic digital logic
functions fundamental to all digital systems. Digital electronics therefore
comprises the design, manufacture and use of circuits for processing information
in digital form (Simpson, 1978).
An
information display is a way of providing information and it is also used as an
object for promotion. It can be seen in a form of cardboard or tarpaulin at
stores / shops, sign posts, placards, notice boards and electronic display
boards. But the advent of new technologies has made the information in the form
of an electronic display in the world of advertisements and promotions (Gupta,
Shukla and Nagwekar, 2013). The ability to display a short message can be
useful application to be available for any business. Electronic digital display
system is perfect for this application. It can be used for both indoor and
outdoor which makes it universal fit for any business or event. Electronic
digital display system is very efficient and cost effective way to spread
messages to thousands of people, without any personal contact or door to door
sales. Light-Emitting Diode (LED) is a solid state light source with several
attractive properties for display application. LED is a diode that gives off
visible light when forward biased (Mehta and Mehta, 2014). It is chosen as the
main component for displaying messages because, today LED is the most energy
efficiency example and other useful systems.
The
birth of signs and display can be said to be as old as the existence of man on
the planet earth. From the beginning of the world, different types of displays
have been in use, each mode to serve the purpose of invention efficiently.
Signs are any kind of visual graphics created to display information to a
particular audience (David, 2013). In 1389, King Richard II of England
compelled landlords to erect signs outside their premises (Manton, 2008). In ancient
Rome, signboards were usually made from stone or terracotta (Chris, 1995).
With
the advancement in technology, man started carving woods and trees. The use of
special dyes on wood as a means of identifying special locations. With the
discovery of Bronze and iron, man started using the materials to display sign,
thus the advent of metal sign boards were born, which are mostly used in
developing countries. On semiconductors and vacuum tubes technology, light
displays and sign boards were built to add more beauty in the old system and as
a way to increase visibility. LED technology is frequently used in signs now
instead of Neon signs, introduced in 1910 at the Paris Motor show (Bellu,
2006). The use of electronic is now becoming very important. It is extensively
applied in almost our day to day activities.
Electronic
digital display system is also used for outdoor advertisement. Before, outdoor
advertising was mainly characterized by the use of paper. Every bus stop and
billboard had a paper advertisement inside. The reason for this was simple
paper was easy to use and extremely cheap. It had some draw backs as well.
Before an image is actually on the street, it first has to be printed, pasted
and placed. The journey from design to placement is quite long. Another
disadvantages is the considerable amount waste generated by the use of paper.
Finally, many people ignore a paper advertisement and there attention is drawn
to the vibrant environment around them and not to a still image.
The
extent of development in information dissemination has made it possible that
the well known method of displaying information using sign posts, notice
boards, etc has to be modified by using electronic digital display system. In
today’s rapidly advancing technology market, most conventional digital display
system are not being implemented using individual logic gates and integrated
circuits (ICs) such have been used in the past instead, programmable devices
such as microprocessor and microcontroller chips which contain the circuitry
necessary to create logic functions are being used to implement digital
systems. The use of 555 timer as a stable multivibrator and decade counter
(CD4017) can be used to build less expensive electronic display system. The use
of these two major ICs will bring about less board space, less power
consumptions and overall, low cost in manufacturing.
This
project however; emphasizes mainly on the display of information using two
major integrated circuits (ICs) namely NE555 timer (ICI) and CD4017 (IC2) to control
the lighting of LEDs. This message display circuit is built around readily
available, low cost components. It is easy to fabricate. A total of 250 LEDs
will be used to display the message “GREAT NIGERIAN STUDENTS”
1.2 Statement of the Problem
Due
to limitation of the sign board or local sign board which could not display
clearly at night expect light shines on it, it is then necessary that
electronic display system is employed to counter the limits of the local sign
board. The information displayed on the local sign board is less attractive
compared to the information displayed using electronic digital display system.
Thus,
researchers are prompted to tirelessly hold up to these challenges by
initiating some means of improving the above among which is the design and
construction of an electronic digital display system.
1.3 Aims and Objectives of the Study
The
main objective of this study is to design and construct an electronic digital
display system. Specifically this study will achieve the following:
i.
To display “WELCOME TO AJAYI POLYTECHNIC”
ii.
To use the electronic digital display system constructed as a sign post for Ajayi
polytechnic
iii.
To have more knowledge on what electronic digital display system is all about.
v.
To know the benefits of electronic digital display system.
v.
To design and realize the moving message display panel.
1.4 Significance of the Study
In
all field of human endeavor, electronic digital display system plays very vital
role, such as means of advertisement, means of communication, presentations,
exhibitions, identification and direction. It is also used in giving warning or
safety instructions, such as warning signs, traffic signs, exit signs or signs
conveying rules and regulations. This project write-up will be a guide to
future designing in a related work.
1.5 Scope of the Study
This
project covers the use of peripheral solid state electronic components
alongside with two major integrated circuits (ICs) namely NESSS timer and
CD4017 decade counter to solve above stated problems. It is limited to display WELCOME
TO AJAYI POLYTECHNIC
CHAPTER TWO
LITERATURE
REVIEW
There are many works that have been carried out on digital electronic
message display board for application in different spheres of life.
Nivetha, et al. (2013) designed and implemented an SMS based wireless
notice board with monitoring system. This project was designed using integrated
circuit (IC4017) which will sends signal to IC 7432.
An
electronic oscillator is an electronic circuit that produces a periodic,
oscillating electronic signal, often a sine wave or a square wave, Oscillators
convert direct current (DC) from a power supply to an alternating current (AC)
signal. They are widely used in many electronic devices ranging from simplest
clock generators to digital instruments (like calculators) and complex computers
and peripherals etc. Common examples of signals generated by oscillators
include signals broadcast by radio and television transmitters, clock signals
that regulate computers and quartz clocks, and the sounds produced by electronic
beepers and video games. Oscillators are often characterized by the frequency
of their output signal: A low-frequency oscillator (LFO) is an electronic
oscillator that generates a frequency below approximately 20 Hz. This term is
typically used in the field of audio synthesizers, to distinguish it from an
audio frequency oscillator. An audio oscillator produces frequencies in the
audio range, about 16 Hz to 20 kHz.
An
RF oscillator produces signals in the radio frequency (RF) range of about 100
kHz to 100 GHz. Oscillators designed to produce a high-power AC output from a
DC supply are usually called inverters. There are two main types of electronic
oscillator – the linear or harmonic oscillator and the nonlinear or relaxation oscillator.
A sequential digital display
A
sequential digital display is an electronic system that is used to display
information to the public. It is a device that contains light emitting diodes
that conveys messages by a programmable controller or mechanical processes,
regardless of size. Sequential digital display is fast gaining acceptance and
application in different spheres of life. In this work, a sequential digital
display system was designed and implemented. The components used include
transformer, diodes, voltage regulator, resistors (fixed and variable types),
capacitors, NE555 timer, IC4017, light emitting diodes and transistors (
Wikipedia, 2016)
Counter unit
In
digital logic and computing, a counter is a device which stores (and sometimes
displays) the number of times a particular event or process has occurred, often
in relationship to a clock signal. The most common type is a sequential digital
logic circuit with an input line called the clock and multiple output lines.
The values on the output lines represent a number in the binary or BCD number
system. Each pulse applied to the clock input increments or decrements the
number in the counter. A counter circuit is usually constructed of a number of
flip-flops connected in cascade. Counters are a very widely used component in
digital circuits, and are manufactured as separate integrated circuits and also
incorporated as parts of larger integrated circuits. ( Wikipedia, 2016)
Driver unit
In
electronics, a driver is a circuit or component used to control another circuit
or component, such as a high-power transistor, liquid crystal display (LCD),
and numerous others. They are usually used to regulate current flowing through
a circuit or to control other factors such as other components, some devices in
the circuit. The term is often used, for example, for a specialized integrated
circuit that controls high-power switches in switched-mode power converters. An
amplifier can also be considered a driver for loudspeakers, or a voltage
regulator that keeps an attached component operating within a broad range of
input voltages. Typically the driver stage(s) of a circuit requires different
characteristics to other circuit stages. For example in a transistor power
amplifier circuit, typically the driver circuit requires current gain, often
the ability to discharge the following transistor bases rapidly, and low output
impedance to avoid or minimize distortion. ( Wikipedia, 2016)
Electronic bill board
Electronic
billboards are high-tech versions of the traditional billboards that are often
found along highways and major thoroughfares within some cities. The main
function of this type of billboard is to advertise goods and services, or
provide announcements or promotions to the general public. A single electronic
billboard may offer a rotating selection of ads for a single entity, or be used
to display advertising for multiple companies on a rotating basis. Some of the
earliest efforts to develop this form of mobile advertising produced results
that were somewhat like a theater marquee. Text and simple illustrations that
were created using projection equipment were considered novel, but not
particularly cost effective. As technology continued to advance, the
development of rear-projection equipment and the ability to control the
multiple displays from a central control unit enhanced the quality and range of
the displays, while also making them much easier to load and unload. One of the
advantages of an electronic billboard is that the advertising no longer has to
be static. Depending on the source of the imaging on the display, the
experience may be somewhat similar to that of watching a commercial on
television. However, the visual display may offer something simple, like
animated graphics that allow the billboard to present a simple ten second
message that repeats continually, making it possible for anyone passing by to
view the entire message with relatively little effort. In addition to the
enhanced options for visual display, companies that operate the billboards can
also maximize their return on a single electronic billboard. Since it is
possible to display an ever-changing rotation of ads for different clients, one
billboard may advertise goods and services for several clients throughout the
day. Advertisers sometimes like this approach, since it allows them to purchase
a certain amount of advertising time each day, without having to pay for the
full use of the board around the clock. While it is likely that the use of
electronic billboard advertising will increase over time, there are some
obstacles that may limit the use of this medium in some settings. Because many
operators of the boards use remote control equipment to load and change
displays, some of the regulations that apply to wireless communications are
likely to apply to the operation of the billboards themselves. In addition,
there is some concern that the movement on an electronic billboard is more
distracting for people driving by the displays, a fact that could lead to an
increase in vehicle accidents. For this reason, some jurisdictions are likely
to impose limits on what intersections and stretches of highways that the
boards can be placed. https://m.wisegeek.com/what-is-an-electronic-billboard.htm
Microcontroller unit
A
microcontroller (MCU for microcontroller unit) is a small computer on a single
integrated circuit. In modern terminology, it is similar to, but less
sophisticated than, a system on a chip (SoC); an SoC may include a
microcontroller as one of its components. A microcontroller contains one or
more CPUs (processor cores) along with memory and programmable input/output
peripherals. Program memory in the form of ferroelectric RAM, NOR flash or OTP
ROM is also often included on chip, as well as a small amount of RAM.
Microcontrollers are designed for embedded applications, in contrast to the
microprocessors used in personal computers or other general purpose
applications consisting of various discrete chips. Microcontrollers are used in
automatically controlled products and devices, such as automobile engine
control systems, implantable medical devices, remote controls, office machines,
appliances, power tools, toys and other embedded systems. By reducing the size
and cost compared to a design that uses a separate microprocessor, memory, and
input/output devices, microcontrollers make it economical to digitally control
even more devices and processes. Mixed signal microcontrollers are common,
integrating analog components needed to control non-digital electronic systems.
In the context of the internet of things, microcontrollers are an economical
and popular means of data collection, sensing and actuating the physical world
as edge devices. Some microcontrollers may use four-bit words and operate at
frequencies as low as 4 kHz, for low power consumption (single-digit milliwatts
or microwatts). They generally have the ability to retain functionality while
waiting for an event such as a button press or other interrupt; power
consumption while sleeping (CPU clock and most peripherals off) may be just
nanowatts, making many of them well suited for long lasting battery
applications. Other microcontrollers may serve performance-critical roles,
where they may need to act more like a digital signal processor (DSP), with higher
clock speeds and power consumption. https://en.m.wikipedia.org/wiki/Microcontroller
Obiechine, et al. (2013) designed and constructed a dot matrix
information display for the office of the vice chancellor, Anambra State
University, Uli. It was done in three stages namely the design, construction
and
working of a dot matrix information display. The project
covered a fairly comprehensive study of a dot matrix
information display. Digital instruments, signals, and
related numbers and codes were discussed. The project
was designed such that the dot matrix information
display operates with electrical power from either direct
or alternating current source.
Emilo (2010) also designed 15 LEDs by 7 LEDs scroll message advertising
billboards, this project uses 105 LEDs to produce a screen 15 LEDs long, by 7
LEDs High for running messages. Larger displays showed more letters but this is
the largest display that can be produced with a single PIC16F628 micro.
Ketkar, et al. (2013) designed
and implemented a LED scrolling message display system. The system hardware
consists of an AT89C51 controller which serves as the heart of the system. The
inclusion of the buzzer and alarm units into
the design limits its area of application and makes thesystem unduly
complex.
Ukpa, et al. (2013) developed a SMS Controlled Digital Display System using
multiple microcontrollers namely PIC16F877 and PIC16F628 and a SAGEM MYX5-2
phone.
Dresden (2008) designed and implemented alternative transparent
electrodes for organic light emitting diodes (OLED). In his work, he studied
the use of two types of alternative transparent electrodes, ZnO: AL and PEDOT. These
were developed for organic OLEDs. The evolution of light bulbs in the 1880s
brought about the use of electric lighting as a standard technology. The use of
flourescent and incandescent lamps has dominated the world today because of
their low cost and long-term stability. Solid state lighting (SSL) is a new
environmental friendly light source with potentially high efficiency. So far,
LEDs and OLEDs have been presented as candidates for solid state lighting
(Alstair, 2013). Several view-sequential displays have been demonstrated
by developers which implement a time multiplexing principle and utilize a fast
optical
modulator, active shutters, and projection optics. Time sequential
information is angularly multiplexed by restricting the pulp of a projection
system in conjunctions with images being displayed on the modulator
(Philip,
John, Phil, & Christopher, 2007). Sequential systems have the advantage of
using a single modulator, which is more economically feasible than other
multi-view systems. They also provide natural reviewing zone, which is a
subject of difficulty for other multi-view displays. However, they require
large projection optics, which limits the field of view. They also throw away a
lot of light because of the active shutter, which are included in the system.
CHAPTER THREE
SYSTEM DESIGN &
ANALYSIS/METHODOLOGY
3.0 MATERIALS AND METHODS
Descriptions of components used in the design are explained in following
sub sections.
3.1 TRANSFORMER
A transformer works through the principle of magnetic induction. It is a
device that converts an alternating (A/C) current of a certain voltage to an
alternating
current or direct current of different voltage, without change of
frequency, by
electromagnetic induction. The functions of the transformer in the
circuit are:
1. To step down the input voltage from 220v to the required 15v of the
designed circuit.
2. Transformer allows high Voltage to be stepped down to lower Voltage.
3. It also allows the circuit diagram to be isolated from mains
Figure 3.1 the symbol of transformer
3.2
DIODES
Diodes used in this work were used to perform rectification after the
transformer had stepped down the voltage to 15volts. The diodes convert AC to
DC
enabling components operating on DC to be powered. The specifications of
diodes used are the IN4007 and IN4148.
Figure 3.2 the symbol of diode
3.3 VOLTAGE REGULATOR
The purpose of the voltage regulator is to get a fixed output voltage
irrespective of the input voltage to the system. Various voltage regulators
exist but the one used
in this work is specified as LM7812 which gives a constant 12V DC supply
to power the circuit. LM7812 have three-terminal devices that provide a
constant DC output voltage that is independent of the input voltage, output
load current, and temperature. The IC does not require additional components to
provide a constant, regulated source of power, making them easy to use, as well
as economical and provides efficient use of space. Other voltage regulators may
require additional components to set the output voltage level, or to assist in
the regulation process. They have protection against overheating and short circuits,
making them quite robust in most applications. In some cases, the
current-limiting
features of the LM7812 devices can provide protection not only for the
LM7812 itself, but also for other parts of the circuit.
3.4 RESISTORS
The resistor acts as a passive component that resists the flow of
current. The resistors available include such ratings as 10KΩ, 330Ω, 1MΩ, 220Ω,
100KΩ,
1KΩ, and 1MΩ variable resistor. However, a 1KΩ resistor was used for the
project.
Figure 3.4 the symbol of resistor
3.5 CAPACITOR
The capacitor is used to allow AC signal to pass to the input of the
timer integrated circuit (IC) while the DC signal is blocked. The capacitor
used in the power circuit
of this project is to filter the ripples that may be found in the power
supply section and in the switching stage. The specifications used in this work
are 100μf, 10nf, 1nf. Various types such as electrolytic capacitor, ceramic capacitor
and mica capacitor were deployed.
Figure 3.5 the symbol of capacitor
3.6 TRANSISTOR
A transistor can be used to amplify weak signal and also act as a
switch. In this work, however, the transistor used IC D888 (NPN) is used to
amplifier weak signal
Emanating from the IC 4017.
Figure 3.6 the symbol of Transistor
3.7 NE555 TIMER
The 555 timer IC is an integrated circuit (chip) used in a variety of
timer, pulse generation, and oscillator applications. The 555 timer can be used
to provide time delays, as an oscillator, and as a flip-flop element.
Derivatives provide up to four timing circuits in one package. This
multipurpose IC NE555 is
wired as a stable-multi vibrator which detects the signal coming to its
input.
Figure 3.7 the symbol of NE555 timer
3.8 INTEGRATED CIRCUIT 4017
The IC 4017 can be considered as one of the most useful and versatile
chip having numerous electronic circuit applications. Technically it is called the
Johnsons 10 stage decades counter divider. The name suggest two things, it has
something to do with number 10 and counting/dividing. The 555 IC will operate
in astable mode with a frequency of 14Hz. The 555 IC in the
circuit is used as a clock pulse generator to provide input clock pulses
to the counter IC 4017. The IC 555 in the circuit operates at a frequency of
14Hz, which means that it produces about 14 clock pulses every second to
the IC 4017. The clock pulses generated at the output of IC 555 timer
(PIN-3) is given as an input to IC 4017 through PIN-14. This is shown in figure
1.
Whenever a clock pulse is received at the clock input of IC 4017
counter, the counter increments the count and activates the corresponding
output PIN. When count is zero, PIN-3 is HIGH, which means LED-1 will be ON
and all the other LEDS are OFF. After the next clock pulse, PIN-2 of IC
4017 is HIGH, which means that LED-2 will glow and all the other LEDs can be
turned OFF. This repeats and the LEDs turn ON and OFF successively on each
clock pulse thereby producing circling effect
Figure 3.8: the diagram of integrated circuit
4017
3.9 INTEGRATED CIRCUIT 7432
The schematic diagram of the IC 7432 used in this work, pin 1 and 2 are
the inputs of first gate where the output is from pin
number 3. Pin number 4 and 5 are the inputs of second gate whose output
is in pin 6. Pin 10 and 9 are the inputs of fourth gate whose output is at pin
8. The input of the last gate or fourth gate is pin 13 and 12 and pin 11 is its
output. Pin 7 is ground and pin 14 is +Vcc supply
3.10 LIGHT EMITTING DIODES (LEDS)
Light emitting diodes are semiconductor devices that illuminate solely
by motion of electrons. When forward biased, these components emit light. LEDs
provide a
cheap and convenient way to display information electronically, fit
easily into an electrical circuit, and are durable. LEDs were designed with
different colours:
RED, BLUE. WHITE, GREEN and PINK etc for the purpose of this project
YELLOW were used. The circuit diagram showing all the components used is
Figure 3.10 the symbol of light emitting diode
3.11 THE CIRCIUT DIAGRAM
Figure 3.11 the Circuit Diagram of The System
CHAPTER FOUR
4.0 IMPLEMENTATION
The implementation of the project is divided into four stages which are:
i. Power stage
ii. Input stage
iii. Amplifying stage
iv. Output (Result) stage
4.1 POWER STAGE
The power stage supplies the current needed to power the circuit. This
stage comprises of transformer, Diodes, Capacitors, wires and the voltage
regulator (7812). The transformer steps down voltage input 220 v to output 15v
which is passed to the block diode for rectification, the output produced is DC
(Direct current) which still contains some ripples (i.e. unwanted AC signal),
the ripples in the circuit if allowed to power a device, may damage the device
or may not allow the device to function properly. To avoid this situation,
filter capacitor
100μf and 10nf are connected to the output of the block diode to filter
the ripples and after the ripples is filtered; the voltage regulator 7812 is
then connected to ensure constant output voltage which is 12V as shown Fig 4. A
Light Emitting Diode is connected to the output in order to monitor the output
power Supply, if voltage is supplied to the output, then the LED glows, and if
not, the LED remains in the off position.
Figure 4.1 the power stage diagram
4.2 THE INPUT
STAGE
The input stage shown in Figure 5 involves the soldering of the NE555
TIMER, IC 4017, resistors, and capacitor on the Vero board which allows the
signal to transmit
to the IC 4017 to control the display of the light emitting diode. The
first output of the IC 4017 must be active at the time when the thyristor chip
is outputting
the first row of data and this means the 4017 must be "clocked"
so that it is turning on the first output at the beginning of the scanning
cycle.
Figure 4.2 the input stage circuit diagram
4.3 THE AMPLIFYING STAGE
In this work, thyristors D882 were used to boost the weak signal from
the CD4017 so as to be able to control display on the output of the circuit.
The first output of
the 4017 must be active at the time when the D882 is outputting the
first group of the character e.g. (WELCOME) and this means the 4017 must be
“clocked”
so as to turn on the first output at the beginning of the scanning
cycle. Figure 6 shows the amplifying stage pictorial view.
Figure 4.3 the amplifying stage diagram
4.4
OUTPUT STAGE/ RESULT
The
designed sequential digital display was tested in the polytechnic environment. It was connected to a 220 volts supply
which is stepped down to 12 volts for the circuit. The result showed that the
light emitting diodes displayed the title: WELCOME TO AJAYI POLYTECHNIC IKERE EKITI
correctly. This is shown in Figure 4.4. In comparison with the work of Emilo (2010)
and Ketkar, et al. (2013), this work uses less complex components andcheaper
materials to achieve the same results.
CHAPTER FIVE
5.0 CONCLUSIONS
AND RECOMMENDATIONS
A moving message display or a scrolling message is an excellent method
of communicating information. The smooth sailing effect of the alphabet or the
characters is not only pleasing to the eyes, but also, information becomes accessible
through a short time passage The design and development of a sequential digital
display board was accomplished. Justification for the selection of materials
used was given by design calculations. The board is used to display a welcome message
for visitors and students in AJAYI POLYTECHNIC IKERE EKITI study centre in
Nigeria. Readily available and cheap components were used to execute the
project. Further improvement works can be done by introducing matrix board and
PIC microcontroller to the project.
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