ABSTRACT
The project is based on the design and
construction of a micro-controller based liquid level detector. This is a
system that will measure the level of liquid in a container and display the
level on 3 seven segment display screen. The system will output an audio and
visual alerting indicator when the tank is full and when the tank is empty.
This alarm can be re-set using an override switch.
This feat is achieved using a programmable
integrated circuit that is programmed using assembly language as well as other
integrated circuits such as a seven segment display driver, a multiplexer and
logic gates. Also, I used other discrete components such as resistors,
transistors, capacitors, diodes etc.
After the design, construction and
implementation, the system functioned satisfactorily as a microcontroller based
liquid level detector system with digital display readout.
TABLE OF CONTENTS
Title page - - - - - - - - - i
Certification - - - - - - - - - ii
Dedication - - - - - - - - - iii
Acknowledgement - - - - - - - - iv
Table of contents - - - - - - - - v
Abstract - - - - - - - - - viii
CHAPTER ONE
1.1 Introduction - - - - - - - - 1
1.2 Aim - - - - - - - - - 3
1.3 Objective of the study - - - - - - 3
1.4 Scope of the study - - - - - - - 4
1.5 Uniqueness of the project - - - - - - 4
1.6 Methodology - - - - - - - - 5
CHAPTER TWO
2.1 Introduction - - - - - - - - 8
2.2 The Sub-circuits review - - - - - - 8
2.2.1 Power supply unit - - - - - - 9
2.2.2 Level detector circuit - - - - - 9
2.2.3 Block diagram - - - - - - 11
2.2.4 Signal translating section - - - - - 11
2.2.5 Micro controller unit- - - - - - 12
2.2.6 Display unit - - - - - - - 12
2.2.7 Alarm circuit - - - - - - - 13
2.2.8 Override reset- - - - - - - 13
CHAPTER THREE
3.1 Introduction - - - - - - - - 15
3.2 Block diagram - - - - - - - 15
3.3 Power supply - - - - - - - 16
3.4 Level detector - - - - - - - 24
3.5 Signal processing unit - - - - - - 26
3.6 Display unit - - - - - - - - 28
3.7 Alarm circuit - - - - - - - - 29
3.8 Microcontroller unit - - - - - - - 33
3.9 The complete circuit diagram - - - - - 43
3.10 Mode of operation - - - - - - - 44
CHAPTER FOUR
4.1 Introduction - - - - - - - - 47
4.2 The assemblage of the electronic
components - - - 47
4.3 The construction of the
electronic circuit enclose - - 49
4.4 The construction of the model container - - - - 50
4.5 The installation of the electronic
signals - - - - 52
4.6 Installation of the
complete system - - - - 52
4.7 Bill of engineering measurement and
evaluation - - 53
CHAPTER FIVE
5.0 Conclusion - - - - -- - - - 56
5.1 Recommendation - - - - - - - 57
References - - - - - - - - 59
CHAPTER ONE
INTRODUCTION
1.1 INTRODUCTION
Liquid is one of the basic forms of matter
and it is embedded into our everyday lives. Since the whole earth is made up of
matter and we interact with it daily, it means that the application or
usefulness of fluid is a very essential part of our daily activity. Various materials
comes in fluidal form and in the process of the utilization of it for our daily
activities, we may desire a need to store it in containers or tanks. Secondly,
the need to accurately or approximately determine the volume or quantity of
fluid contained in the storage container or tank, is also important so that we
can monitor its usage and track its movement.
In the
detection of the level of liquid in a tank, various methodologies could be
applied in other to accurately or approximately obtain the quantity of liquid
in a tank, without actually viewing inside the tank. The use of completely
mechanical means such as analogue calibrated meters which is vastly used in
many commercial and industrial products such as the fuel gauge in a car and
other similar products is widely deployed. Or the use of a purely physical
phenomenon such as liquid pressure as seen in the operation of barometric based
meters in liquid detection as applied in most crude oil tanks in flow stations
and other similar conditions. Or the use of a purely manual method as seen in
the use of a dip stick, as applied in majority of petrol filling stations in
the country.
These
methodologies, although very effective and serves the purpose of which they are
applied in the first place, they lack sophistication and sometimes inaccurate
reading of the actual quantity is impossible. To this effect, more accurate
methods will be applied in this project, the use of electronics in the
measurement and calibration of a liquid level in the tank.
A microcontroller
is an integrated circuit that carries out instructions under the guidance of a
program. Microcontroller based application are embedded in every sphere of live
that involves the use of electrical or electronic devices. The range of
application includes industrial, medicine, navigation, space exploration,
measuring and calibration etc.
For
the measuring and calibration applications, the microcontroller is designed
together with other discreet electronic components and implemented in such a
way as to accurately collect datum of the measured material and using a
suitable calibration protocol, present the quantity of the measure material
into a suitable reading output in weight, volume, level or height.
Other
features will be added to the basic operational principle of this circuit, such
as a notification of tank empty and tank full, also a fully digital display
readout of the level of fluid in the container.
1.2 AIM
The aim of the project is to design and
construct a microcontroller based an electrical electronic embedded system
circuit or device that will accurately measure the level of liquid in a
container and present the data into a readable digital format that could be
easily read and completely understood by the user.
1.3 OBJECTIVE OF THE STUDY
i.
To
actualize the above aims, the following objective has to be met.
ii.
To
obtain a standard embedded systems schematic diagram to achieve the system that
will enable one to measure accurately, the level of liquid in a container
iii.
To
choose a suitable programming language that will be used in the programming of
an 8052 microcontroller that will be used in the circuit
iv.
To
obtain a power supply unit that will suitably power such a system
v.
To
create a mechanical system that will allow the physical quantity (liquid level)
to be translated into electrical quantity or signals
vi.
To
design a suitable electronic circuit that will enable the microcontroller to
drive the display unit that will show the level of liquid in the container
vii.
To
design a alerting system that will comprise of both an audio and visual
indicators that will be activated when the tank/container is full and when it
is empty
1.4 SCOPE OF THE STUDY
The scope of the study will involve the
presentation of the usual methodologies in determining the liquid level in a
tank or container used worldwide by various spheres of professionals in
existence today and to explain, using technical theories and accurate
engineering principles how, the use of a microcontroller and electronic
implementation is more modern and user friendly.
The scope also covers the careful
presentation of the various stages of the system, ranging from the power
supply, the level detectors, the modulator circuits, the microcontroller unit
and flowcharts, the digital display and the alerting system.
1.5 UNIQUENESS OF THE PROJECT
The liquid level detector circuit is a common
technology and as stated earlier, various methods exists worldwide that
measures the level of liquid in a container, however, the uniqueness of this
circuit is the utilization of an embedded system as the heart of the system. An
embedded system is simply an electronic circuit that has at least one
programmable integrated circuit.
The addition of the microcontroller makes the
system to be intelligent and leaves room for upgrade. The circuit has an over
full and under full liquid detector, while the alerting signals is activated,
the signal can only be deactivated either by the liquid level changing state
from one level to the other. This means that the over full has to become normal
while the under full will also be normal.
Furthermore, another uniqueness feature that
the circuit has is that in most systems when over full is detected or under
full is detected, its only a change of state that can stop the notification,
however, in this circuit, there is a notification over ride push button than
can be pressed by the user to stop he notification alert even if the state of
the fluid level has not changed.
1.6 METHODOLOGY
The methodology employed in the design and
construction of an electronic circuit that will measure the liquid level in a
tank and produce the value in a digital read out format, is one that involves
also in the creation of every master piece engineering technology.
Text books and internet were consulted as
well as the use of standard electronic circuit network theorems and principles
all with the aim of actualizing the most appropriate electronic circuit diagram
to perform the expected function
In the programming of an 8052 microcontroller,
many programing languages can be utilized. Amongst the options are, EMBEDDED C,
BASIC, MACHINE CODE and ASSEMBLY LANGUAGE. of the available options, assembly
language is chosen because of its ability to perfectly blend high level syntax
that enable humans to write a program code that will be easily compactable with
everyday language, with a language that is closely related to machine codes
which is the only language that electronic systems can understand.
The whole system must be operated from a 5
volts dc power supply unit. The choice of battery powered system and electrical
public mains was considered but due to its ability not to need recharging, the
public mains was chosen. An a.c to dc converter circuit was used to obtain 5
volts dc from the 220 volts ac public mains power source.
The mechanical system that was used in the
translation of the liquid level into electrical quantity is metallic screws
that were screwed into the body of the container. Conductors were connected
from these screws to the system and when a liquid rises above the screws, they
will send electrical signals from the terminals to the electronic circuit
The level of liquid will be displayed using
common cathode 7-segment displays. To adequately drive theses display units,
the common cathode 7-segment display driver CD4511, was used. To ensure that
the display units doesn’t use up all he terminals from the microcontroller, the
one-of-eight lines de-multiplexer integrated circuit, DM74138, was used
Finally, for the audio and visual alerting
system, a light emitting diode (LED) was used for the visual output while an
electronic buzzer was used for the audio output. For effect, a pulse width
modulator, 555 timer connected in the astable mode, was used to dive these
indicators
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