sir G 2

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TITLE PAGE
THE DESIGN AND CONSTRUCTION OF AN AUTOMATIC
ALARM SYSTEM TO MONITOR THE WATER LEVEL
BY
Tgst. GINGER AMEE TERDUE, MNATE; MAMDE; MAEEES.
AUGUST, 2014

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ABSTRACT
The design and construction of an Automatic Alarm System to monitor the water level
is an electronic device which attempt to monitor the flood level/water level and to
alert the user to put it off. Being an electronic device, it is Automatic and highly
sensitive to water. The system is a network comprising of a Sensor Unit which is a
plastic container fitted with Two Probes made of Copper Conductor; Solid State
Switch which is a direct coupling of Amplifier using Complimentary Circuits of two
Transistors, NPN and PNP. It consists of Oscillator Unit is an Electronic Circuit that
use AC outputsignal without requiring anyexternal applied input;and then the Audio
power amplifier which consists of a Darlington Pair in which the Emitter of one is
connected to the base of the other directly. It’s a rugged device and can be used under
diverse conditions. With the low power consumption of the device, it can function for
a very long time before it calls for a battery replacement. This is due to the fact that
the Oscillator is in a standbymode when Flood or spillage due to over-drainage does
not occur. It can withstand Mechanical Vibrations when moving it from one place to
another as well as adverse condition of water (Non-distilled) be it rain, river or pond.
The Switching unitis responsible for switching ON/OFF of the buzzer when actuated;
the Sensor unit normally senses the water level, indicating and sensing the water level
from the designated point and Buzzer unit which is responsible for activating an
Audio sound (Alarm) when the water level fills up the tank.

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With the low power consumption of the device, it can be used underany condition and
it can function for a very long time before the need will arise for battery replacement.
This project comprised of five chapters; Chapter One deals strictly with the
Introduction which includes: Statement of the problem; Significance of the Study;
Background of the Study; Scope of the Study; and Limitations of the Study.
Chapter Two contains the review of related literature; and the theory of components.
Chapter Three has the Design Analysis and Block diagram. Chapter Four accounts
for the construction stages, Materials used and Bill of Engineering Measurement and
Evaluation. Chapter Five contains the Summary, Conclusion and Recommendation.

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TABLE OF CONTENT Page №
ABSTRACT-------------------------------------------------------------------------- vi.
TABLE OF CONTENT------------------------------------------------------------- vii.
CHAPTER ONE
1.0 INTRODUCTION------------------------------------------------------------ 1 - 7
1.1 THE BASIC FEATURES--------------------------------------------------- 7 - 8
1.2 STATEMENT OF THE PROBLEM--------------------------------------- 8
1.3 SIGNIFICANCE OF THE STUDY---------------------------------------- 8 - 9
1.4 BACKGROUND OF THE STUDY---------------------------------------- 9
1.5 SCOPE OF THE STUDY---------------------------------------------------- 9
1.6 LIMITATION OF THE STUDY------------------------------------------- 10
1.7 DEFINITION OF TERMS-------------------------------------------------- 10 - 11
CHAPTER TWO
2.0. REVIEW OF RELATED LITERATURE-------------------------------- 12 - 13
2.1. THEORY OF COMPONENTS-------------------------------------------- 13 - 31
CHAPTER THREE
3.0. DESIGN AND ANALYSIS------------------------------------------------- 32

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3.1. BLOCK DIAGRAM---------------------------------------------------------- 32
3.2. CIRCUIT DIAGRAM-------------------------------------------------------- 33
3.3. PRINCIPLES OF OPERATION-------------------------------------------- 34 - 35
CHAPTER FOUR
4.0. CONSTRUCTION TECHNIQUES/DESCRIPTION-------------------- 36
4.1. SOLDERING TECHNIQUES------------------------------------------------ 36 - 43
4.2. STEPS IN SOLDERING------------------------------------------------------ 43 - 47
4.3. TOOLS USED IN CONSTRUCTION-------------------------------------- 47 - 48
4.4. MATERIALS USED----------------------------------------------------------- 48
4.5. BILL OF ENGINEERING MEASUREMENT AND EVALUATION-- 49
4.6. TESTING------------------------------------------------------------------------- 50 - 51
CHAPTER FIVE:
5.0. SUMMARY AND CONCLUSION----------------------------------------- 52
5.1. RECOMMENDATION-------------------------------------------------------- 52 - 53
REFERENCES------------------------------------------------------------------ 54 - 55

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CHAPTER ONE
1.0. INTRODUCTION
Generally, in most countries, houses and buildings tend to have two water tanks, one
situated on the roof and other on the ground or sometimes underground. The received
water supply is allowed to fill the lower tank first, and a water pump motor is then
switched ON manually so that the water from the lower tank is pumped and shifted
into the upper tank on the roof. Once the water from the lower tank is completely
transferred into the upper tank, the pump is again manually switched OFF. This
process may have to be repeated quite regularly and at times may become a bit of a
headache. Moreover in case, one may forget or fails to do the manual switching in
time, it may result in an overflowing of water and wastage.
As the name depicts, an Automatic Alarm System to monitor water level is an
automatic device used to monitor a particular level of water (for example in an
overhead tank) and restrict it from exceeding a certain limit. The simple circuit design
for such a controller is easily built and installed and may relieve you of the trouble of
manually operating the water pump in time.
The problem of lack of adequate and integrated water management has made it
necessary for researchers in the field to look for a way of cushioning the effect of
water spillage and wastage. Water is commonly used for Agriculture, Industry, and
Domestic consumption. Therefore, efficient use and water monitoring are potential
constraint for home or office water management system.

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Last few decades several monitoring system integrated with water level detection have
become accepted. Measuring water level is an essential task for government and
residence perspective. In this way, it would be possible to track the actual
implementation of such initiatives with integration of various controlling activities.
Therefore, water controlling system implementation makes potential significance in
home applications.
The existing automated method of level detection is described and that can be used to
make a device ON/OFF. Moreover, the common method of level control for home
appliance is simply to start the feed pump at a low level and allow it to run until a
higher water level is reached in the water tank. This is not properly supported for
adequate controlling system. Besides this, liquid level control systems are widely used
for monitoring of liquid levels, reservoirs, silos, and dams etc. Usually, this kind of
systems provides visual multi level as well as continuous level indication. Audio
visual alarms at desired levels and automatic control of pumps based on user’s
requirements can be included in this management system. Proper monitoring is needed
to ensure water sustainability is actually being reached, with disbursement linked to
sensing and automation. Such programmatic approach entails an Automatic Alarm
based automated water level sensing and controlling.
Flood and Water scarcity is considered as one of the biggest problems that is gripping
the major metro cities of the world like the case in Nigeria between 2011 and 2012.
Most of the people who have easy access to resources like water have careless attitude

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towards issues of water scarcity and wastage, but people who face this problems
knows what it takes to have water.
For us to overcome the problem of water scarcity and manage our water resources
very well, we are faced with an important task of preventing wastage of water through
monitoring. This can be achieved by the use of an Automatic Alarm System to
monitor the water level. This is a unique but simple device that is designed to be used
to measure the water level in a Tank, Fish Pond, and swimming pools thereby
preventing wastage and overflow of water.
Basically, the unit of this water level indicator is made up of four sensors acting as a
switch in the tank, fish ponds or pools. These set of sensors as connected to a circuit
works in this way: As the water level starts to rise up, the sensors gets activated when
placed at different levels in the water tank indicating the level of water in the tank.
When the water level finally reaches the top most sensor, the light operating Diode is
activated in the circuit as there will be a visual display as well as a sound (Alarm)
from the buzzer showing that, the water is filled up in the tank and one can be alerted
that the water is filled up and the water source has to be disconnected or switched off
(in case of a pump) thereby saving electrical energy as well as preventing an overflow
of water from the tank.

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1.1 THE BASIC FEATURES
The technique of an Automatic Alarm System to monitor water level is concentrated
with some basic parts which are softly aggregated together in our proposed method.
Basic descriptions of some parts are described below.
A. Water Level Indicator
For water level indicator unit we used some LED light which work for water level
indication. By touching different water levels through water level sensor, LED should
be indicated as ON/OFF (i.e. ON: yes sensor senses water).
B. Sensor Unit
To make water level sensor we used some convenient materials such as; Iron rod,
nozzles, resistance wire, rubber etc. A connecting rod made of iron and steel which
was connected with ground and need at least four nozzles which are connected with
+5V via a 1kΩ resistance. We need to bind them together and put a rubber at their
joint point which will act as an insulator for every nozzle. When the sensor comes in
contact with water, nozzles and connecting rod get electric connection using water
conductivity.
The sensor unit consists of two parts namely; the rod and the nozzle. Rod is made by
iron and steel, that is connected with ground. Nozzles are connected with +5v. Iron
rod and nozzles are binding together via a rubber. Rubber is used to make the
electrical connection of iron rod and nozzles separate. Due to water conductivity 22kΩ
resistance has been used. The basic operation is, when one nozzle of the sensor is

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drawn into water, nozzle and rod becomes connected due to water conductivity. Then
nozzle gets ground signal (0v) which is connected with input of the inverter. The
output of inverter is connected as the input of microcontroller which makes LEDs
on/off, acts as user display unit.
C. The circuit part
It comprises the electrical system where all point connections are arranged for
effective output which controls the functionability of the whole system.
D. The power supply
It is the part that supplies a regulated 9Volts power to the circuit.
E. The buzzer part
It is responsible for activating an Audio sound (Alarm) when the water level fills
up the tank.
1.2 STATEMENT OF THE PROBLEM
Today, most of the Water tanks and fish pond users have replaced conventional pumps
with Electrical pumps, but they found it inconvenient due to the conditions of water
pumps because there is no effective water level indicator.
As a result of this, if the mechanical sensors fail, there will be plenty of water wastage
as well as wastage in terms of power consumed by the motor pump.
It is therefore pertinent to avoid flood and water wastage by introducing this device
which is an Automatic Alarm System that monitors the water level and gives an
Audio-Visual display Alert System for the users.

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1.3 SIGNIFICANCE OF THE STUDY
A water level indicator employs a simple mechanism to detect and indicate the water
level in an overhead tank or any water trough.
An Automatic Alarm System to monitor water level is a simple device because it is
easy to operate. It is also economical because, it prevents scarcity and overflow of
water. This simple but versatile device indicates the level of water in the tank and
gives an Alarm when the water level is below the lowest set level and also when water
just touches the highest set level.
This device is designed to display four different levels. However, these display levels
can be increased or decreased depending on the level resolution required. This can be
done by increasing or decreasing the number of level detector metal strips and their
associated components.
1.4 BACKGROUND OF THE STUDY
In most houses, water is first stored in an underground tank (UGT) and from there it is
pumped up to the overhead tank (OHT) located on the roof. People generally switch
on the pump when their taps go dry and switch off the pump when the overhead tank
starts overflowing. This results in the unnecessary wastage and sometimes non-
availability of water in the case of emergency.
The simple Automatic Alarm System to monitor water level circuit here makes this
system automatic. i.e. it switches on the Alarm when the water level in the tank goes

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low and switches it off as soon as the water level reaches a pre-determined level. It
also prevents spillage in case the tank fills up.
In this project, the introduced Automatic Alarm System of monitoring water level and
management is within the context of electrical conductivity of the water. More
specifically, we investigated the Transistor based water level sensing and controlling
switch system in a wired environment. Water Level management approach would help
in reducing the home power consumption and as well as water overflow.
1.5. SCOPE OF THE STUDY
An Automatic Alarm System to monitor water level is designed for both large and
small water reservoir. The device must be installed by a trained professional.
This device consists of Resistors, Transistors, Light Emitting Diodes (LED’s), Beaker,
IC CD 4066 and switch.
1.6. LIMITATIONS OF THE STUDY
In the course of designing this project, we encountered problems like inadequate
materials, time management due to other vigorous academic engagements and also
financial restrictions as factors that limit this work in the sense that, all stages of this
work are affected by cost as all the information gathered are dependent on the amount
of money available. With this in mind, we have decided to limit our research work on
an Audio-visual alert System which is an Automatic Alarm System to monitor water
level.

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1.7. DEFINITION OF TERMS:
Resistors: A resistor is an electric component that has the property of opposing the
flow of current.
Transistor: A transistor is a semi-conductor device that can either amplify an
electronic signal or act as an electronic switch.
LED’s: These are semi-conductor devices that emit visible light when an electric
current passes through them.
Beaker: This is a simple container for stirring, mixing and heating liquids. It also
holds liquid quantity of solution as used in many laboratories.
ICCD 4006: This is an IC device that contains four analogue bilateral switches, each
with an active-high enable input (A) and two input/output.
Switch: This is a device that allows current to flow through a circuit when it is closed
and when it is opened, current drops to zero.
Cable: This is a metallic conductor made of two or more wires running side by side
and bonded, twisted and braided to form a single assembly.
Speaker: This is an electromagnetic device that converts electrical energy and
magnetic energy into mechanical energy in form of sound i.e. translate
electronic signals stored in tapes and DVD’s into audible sounds.
Battery: This is a device containing electrolytic cells which stores electrical charges
(energy) in form of chemical energy i.e. it converts chemically stored energy
into electrical energy

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CHAPTER TWO
2.0. LITERATURE REVIEW
A comprehensive review of literature is generally believed to be an essential
ingredient in the development of knowledge through research, (Gamajan, 2002). The
significance of the literature review derived from the fundamental belief among
researchers that the more one knows about the methodology, findings, and conclusion
to one area of study, one can tackle current research analysis for more effectively.
A water level Alarm indicator is a device used to alert the user of either a low water
supply or an overflow of water in an enclosed entity by an electrical system of Alarm
which emits an Audible sound through a buzzer. (Raikut, 2007).
All Alarm Systems to monitor water levels require either an AC voltage supply or a
DC voltage supply in other to start or power them up. But due to the problems
associated with the research of Water level indicators and Alarm Systems under AC
input voltage, the effectiveness of the system and its aim of monitorship are defeated,
especially in the event of unsteady power supply and power upsurges. (Mohammad,
2012).
This study is focused on finding a solution to the problem of using AC supply and at
the same time, design and construct one in which the problem associated with general
water level indicators with Alarm can be overcome. (Radgah D.Z, 1998). It is in this
regard that, the researchers designed and constructed an Automatic Alarm System to
monitor water level which adequately takes care of monitorship and lay to rest the

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worries associated with power outages during operations as this system is powered
from a DC Battery of 9volts which is easily assessable.
The following components were considered appropriate for the circuit to operate
successfully under normal condition.
1. Transistors
2. Metallic sensors
3. Resistors
4. Light Emitting Diodes (LED’S)
5. ICCD 4066
6. Beaker
7. Switch
8. Speaker (Buzzer)
9. Volts battery
10. Cable
DIODE
The diode is a two terminals semi-conductor device made up of PN junction.
The PN junction offers no resistance, it acts as an insulator when reverse biased. In
the forward bias conduction readings occurs as soon as the internally carried voltage
is overcome.

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However, in the reverse bias mode, the majority is blocked, only small amount of
majority carriers are allowed to reach the saturation level, and it’s called current
leakage and this current flows with increase in reverse voltage.
USES OF DIODES
i. Used as power rectifier diode.
ii. Used as signal diode in communication systems for modulation of small
signals.
iii. Used as zener diode in stabilization circuits.
iv. Used as voltage controller in radio and TV receivers.
2.1. THE THEORY OF COMPONENTS
Light emitting diodes
As the name indicates, LED is a forward biased PN junction which emits visible light
when energized. Charge carrier recombination takes place when electrons from the N-
side cross the junction and recombine with the hole on the P-side. Now, electrons are
in the higher conduction band on the N-side whereas holes are in the lower valence
band on the P-side. During recombination, some of the energy is given up in the
form of heat and light (i.e. photons). For Silicon, Si, and Germanium, Ge, junctions,
greater percentage of this energy is given up in the form of heat so that the amount
emitted as light is insignificant. But in the case of other semi-conductor materials like
Galium-Arsenode Phosphate (Ga As P), a greater percentage of energy released
during recombination is given out in the form of light. If the semi-conductor material

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is translucent, light is emitted and junction becomes a light source i.e. a light
emitting diode (LED).
According to Richard J. Fowler (2003, Pg. 7), Light Emitting Diode (LED) is often
used as an indicator in a place of lamp. It is also used for numeric readouts on
calculators and other digital devices. Light emitting diodes (LED’S) are small low
powered, and reliable. They can operate for years without failure. They are available
in either a wire terminal or socket- type base. Although light emitting diodes (LED’S)
are red, they are available in green, blue and yellow. The colours are determined by
the combination of materials used in the manufacturing of Gallium, Arsenic and
Phosphorous.
Light emitting diodes (LED’S) are real unsung heroes in the electronic world. They do
dozen of different jobs and are found in all kinds of devices. Among other things they
form numbers on digital clocks, transmit information from remote controls, light up
watches and tell you when your appliances are turned on, when collected together,
they can form images on jumbo television screen or illuminate a traffic light.
Basically, LED are just tiny bulbs that fit easily into an electrical circuit. But unlike
ordinary incandescent bulbs, they are illuminated solely by the movement of electrons
in semiconductor-materials and they last just as a standard transistor. The life span of
an LED surpasses the short life of an incandescent bulb by thousands of hours. Tiny
LED are already replacing the tube that light up LCD HDTV’s.
The LED’s are basically used in the following areas:

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1. It is used to dictate the portion and position of water in the water tank.
2. It is used in decorating Christmas trees.
3. It is also used as ultraviolet LED, to find scorpions as they light up under the light.
When you need to add light to a model, an ordinary filament lamp is the first thing
that springs to mind. But if you don't need a high light output, or you need light as an
indicator, an LED has many advantages over a lamp.
LEDs are available in many shapes and sizes, some of which are shown in the
selection below. The 'standard' LED shape is the 5mm diameter domed type, and the
smaller 3mm domed type is also popular.
LEDs have traditionally been red, orange, yellow, or green, but advances in LED
technology mean that blue and white LEDs are now available, though at a much
higher price. These LEDs are considerably brighter than standard LEDs so they could
be used for lighting, but you will find the ones described as 'white' still have a blue
tinge.
Also available are LEDs described as 'bi-color' and 'tri-colour'. Bi-colour LEDs
typically incorporate one red and one green LED in the same package. Since they
have only two leads, only one LED can be on at any time. Tri-colour LEDs also have
two LEDs in one package, but because they have three leads, both LEDs can be
switched on together, their light combining to make a third colour, typically orange.
The central lead of such a package is the common for both LEDs.

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Some manufacturers produce true 'tri-colour' LEDs incorporating red, green, and blue
LEDs, so in theory it is possible to create light of any colour.
The physical colour of an LED package does not necessarily indicate the colour it will
be when switched on. Some LEDs have a clear plastic package, while others may
have a diffused plastic package.
Current consumption
LEDs consume much less current than lamps - usually only 20mA - so they are ideal
for battery powered models.
Long life
LEDs rarely fail (unless you supply them with the wrong voltage!) so are handy in
parts of a model that are hard to reach.
An LED is a diode, so current will flow in one direction through it, but not in the
other direction. When an LED is 'forward biased' it will light and, there will be a
voltage drop of around 0.7V across it. When an LED is 'reverse biased', current will
not flow through it and it will not light. It is this property that enables a bi-colour
LED to have only two leads.
Most LEDs require a forward bias voltage of around 2V and consume a current of
around 20mA, but you should check the data available for the type of LED you are
using to determine its exact voltage and current consumption.
To supply an LED with 2V at 20mA, you simply need to place a current-limiting
resistor in series with it as shown in figure 1. The resistor value can be calculated

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using simple Ohm's law (I = V⁄ R) where R is the resistor value in Ohms (Ω) and Vs is
the voltage of your power supply in Volts (V). If you have different values for the
forward bias voltage and current, then substitute them for the 2V and 0.02A values.
How can you tell which lead on an LED is which? Figure 2 shows a standard domed
LED. If brought new, you will find that the longest lead is the positive lead, or 'anode',
and the shortest lead is the negative lead, or 'cathode'. If the leads have been cut there
are a few other ways to find out the polarity:
1. The plastic package nearest the cathode will be flattened slightly.
2. When holding the LED up to a light, the largest triangular section inside will be
nearest the cathode.
You can also connect up the LED (as in Figure 1) both ways around to see which is
correct - reverse biasing the LED won't do it any harm.
RESISTORS:
According to William L. Faissler (1991, Pg. 6), resistors are components that obey
Ohms law. i.e. their resistance is dependent of the current flowing through them.
Resistors are grouped based on the materials they are made hence the value of the
wire wound resistor can be measured by the use of Ohm meter. Colour coding is also
used to determine the values of the carbon resistor. However, a variable resistor is
used as a volume control in electronic circuits. Such electronics circuits are Radio,
Television and Amplifier.

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According to Theraja (2002), a resistor in Engineering is an electrical device having
the properties of restricting the flow of current through it. Whenever current flows
through a resistor, heat is dissipated in the component. This property is called
resistance and the unit of measurement is in Ohms (Ω). Resistors are the most
commonly used electronic components and made in a variety of ways to suit the
particular type of application.
Resistors are usually manufactured as either carbon composition or carbon film. In
both cases, the general appearances are of a small cylinder with leads protruding from
each end. If subjected to over load, carbon resistors usually decrease in resistance
since carbon has a negative temperature coefficient. This causes more current to flow
through the resistor. The temperature rises and failure occurs usually by fracturing.
These resistors equally have power rating between 0.1 watts to 2.0 watts.
A resistor placed in a circuit will resist the passage of electrical current through it and
will therefore alter the voltages in the circuit according to Ohm's Law which relates
voltage (V in Volts) to current (I in Amps) and resistance (R in Ohms). The unit
'Ohms' has its own symbol, the Greek capital letter Omega (Ω).If you need to find
out the current flowing through a resistor, or the resistance of a resistor, you can easily
re-arrange Ohm's Law to find these quantities; I, V & R.
Resistor values
Resistor values that are available for use in circuits range from 0Ω to around
10,000,000Ω. Because dealing with large numbers like 10,000,000 is awkward, the 'k'

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prefix is used to denote 1,000 and the 'M' prefix is used to denote 1,000,000. 'k' stands
for 'kilo' and 'M' stands for mega. Here are some examples of resistor values;
1kΩ = 1,000Ω (pronounced 'one kilo Ohm' or 'one k' for short)
10MΩ = 10,000,000Ω (pronounced 'ten mega Ohms' or 'ten meg' for short)
Sometimes you will see resistors quoted without the Ω symbol, and sometimes the
symbol will be replaced with 'R'. When a fraction is needed in a value you will often
see 'R', 'k', or 'M' in place of the decimal point as an aid to clarity:
22k is the same as 22kΩ
330R is the same as 330Ω
4K7 is the same as 4.7kΩ
Resistors in series and parallel
If you do need a resistor of exact value, but you don't have one, you could always
combine two or more resistors to get the correct value. This is done by placing the
resistors in 'series' or 'parallel'.
If you place resistors in series, the total value of the combination is the value of each
resistor added together. For example, a 10kΩ resistor in series with another 10kΩ
resistor makes a total of 20kΩ.
Placing resistors in parallel is slightly more complicated, since the total value of the
combination will be the result of the following formula:
1
𝑅₁
+
1
𝑅₂
+ 𝑅ո = Rtotal
where Rtotal is the total combination and R1 to Rn are the values of each resistor in the
combination.

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If both resistors in the combination are of the same value, it is easy - the total value of
the combination is half the value of one of the resistors. For example, a 10kΩ resistor
in parallel with another 10kΩ resistor makes a total of 5kΩ.
Tolerance
Like all components, resistors are never perfect. Their true value will never be exactly
the same as their stated value, but will be somewhere close. The maximum amount of
error in the value is given by the 'tolerance' value, expressed as a percentage. Most
resistors have a 10% - 20% tolerance, and this is normally adequate for most
applications. You can get 1% and 2% tolerance resistors if you need them.
Power rating
Resistors also have a power rating, expressed in Watts (W), which needs to be taken
into account when choosing the type of resistor needed in a circuit. For most low
voltage, low current circuits 0.6W resistors will be adequate. Where a higher rating is
required, it will be stated.
The Resistor Colour Code
Because resistors are so small, it is not easy to print their value and tolerance on them
in a way which is easily readable. Therefore, one of the following colour coding
systems is used instead. Both systems code the value in Ohms - there are no codes for
'k' or 'M'.

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The four colour band
This system uses three coloured bands to represent a resistor's value, and an additional
coloured band spaced further apart to represent a resistor's tolerance.
-The first two bands give the first two digits of the resistor's value.
-The third band is a multiplier and gives the number of zeroes that must be placed
after the first two digits.
-The forth band gives the resistor's tolerance as a percentage.
The table below shows the meaning of each colour for each of the bands. Notice that
most of the colours are in the order of the colours of a rainbow, with the exception of
indigo which is not used. There is a rhyme you can use to remember these colours:
Richard Of York Gave Battle in Vain.
Colour
Band 1
1stDigit
Band 2
2nd Digit
Band 3
Multiplier
Band 4
Tolerance
Black 0 0 x 1 -
Brown 1 1 x 10 1%
Red 2 2 x 100 2%
Orange 3 3 x 1,000 -
Yellow 4 4 x 10,000 -
Green 5 5 x 100,000 -
Blue 6 6 x 1,000,000 -

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Violet 7 7 - -
Grey 8 8 - -
White 9 9 - -
Gold - - - 5%
Silver - - - 10%
Fig. 1.
The five band Resistors:
The five-band system uses the same colours as the four band system, but uses them
slightly differently. An extra band is included which acts as another digit, and the
colours Gold and Silver are used as additional multipliers of 0.1 and 0.01. The five-
band system can therefore represent values to three significant figures and also values
lower than 1Ω.
-The first three bands give the the first three digits of the resistor's value.
-The forth band is a multiplier and gives the number of zeroes that must be placed
after the first two digits.
-The fifth band gives the resistor's tolerance as a percentage.
The table below shows the meaning of each colour for each of the bands.

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Colour
Band 1
1stDigit
Band 2
2nd Digit
Band 3
3nd Digit
Band 4
Multiplier
Band 5
Tolerance
Silver - - - x 0.01 10%
Gold - - - x 0.1 5%
Black 0 0 0 x 1 -
Brown 1 1 1 x 10 1%
Red 2 2 2 x 100 2%
Orange 3 3 3 x 1,000 -
Yellow 4 4 4 x 10,000 -
Green 5 5 5 x 100,000 -
Blue 6 6 6 x 1,000,000 -
Violet 7 7 7 - -
Grey 8 8 8 - -
White 9 9 9 - -
Fig. 2. shows a few examples of the resistor colour code using both systems.
Using Resistors
Most resistors look like the ones shown below left, although their thickness will
increase as their power rating increases. Surface mounting resistors like those shown
below right are also available, but since they are so small and hard to handle and
solder, they won't be of much use to the hobbyist.

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Resistors normally come on a bandolier - two strips of paper like the ones shown
above left. The resistors are spaced 5mm apart so that they can be easily fed into
machines that bend and cut the leads automatically. Unless you have access to such a
machine, you will need to do this yourself in order to mount your resistors onto a PCB
or piece of strip board. First, bend one of the leads to 90° using pliers, and then use an
off-cut of strip board to get the bend in the other lead in exactly the right place.
Resistors can be placed either way round and they are not damaged by the heat of
soldering.
Variable Resistors
In many circuits the value of a resistor needs to be adjusted by the user when the
circuit is in use. One easy way to achieve this is to replace the resistor with a variable
resistor. Variable resistors have a shaft which, when turned, will increase their
resistance smoothly from around 0Ω up to their marked resistance value.
The shaft is connected to a 'wiper' inside the variable resistor which makes contact
with a circular track made of a resistance material, which will be laid out in either a
'linear' or 'logarithmic' fashion. Most circuits will use variable resistors with a linear
track (usually marked 'LIN'), although you will find logarithmic variable resistors
(usually marked 'LOG') used as volume controls, for example in audio amplifier
circuits. Most variable resistors are designed to be turned easily by hand, and come
with long shafts that can be trimmed to length for panel mounting. The end of the
shaft can be fitted with one of many styles of control knob.

28
Almost all variable resistors that you can buy have three terminals; one connected to
each end of the track and one (usually the centre) connected to the wiper. These
variable resistors are called 'potentiometers' and have a different circuit symbol to
those that have only two terminals, which are called 'rheostats'.
Presets
Sometimes a resistance in a circuit will only need to be adjusted once, perhaps to
calibrate a circuit, and it will rarely be adjusted again. In this situation, small 'preset'
variable resistors can be used. These are normally adjusted using a small screwdriver
so that the shaft position cannot be altered by accident.
FUNCTIONS OF A RESISTOR
The function of a resistor in this project is to adjust the signal and voltage level for
brightness, volume or tone. The most common type used on electronic work has a
circular carbon track contacted by means of an adjusting shaft or by placing screw
driver in the slot. The value of a resistor and tolerance may be marked on the body
either by direct numerical indication or by using a standard colour code.
COLOUR BAND 1 & 2 BAND 3 TOLERANCE BAND 4
Black 0 10°
Brown 1 10¹ + 2%
Red 2 10²
Orange 3 10³

29
Yellow 4 10⁴
Green 5 10⁵
Blue 6 10⁶
Violet 7 10⁷
Grey 8 10⁸
White 9 10⁹
Gold ̶ 10¯¹ +5%
Silver ̶ 10¯² +10%
No colour ̶ ̶ +20%
Table 1: Standard colour coding for Resistors
TRANSISTORS
A transistor is a semi conductor device that can either amplify an electronic signal or
act as electronic switch. It was invented by a team of three scientists at Bell
laboratories, USA in 1947. Although the first transistor was not a bipolar junction
device, yet it was the beginning of technological revolution that is still containing in
the Twenty first century. All of the complex electronic devices and systems
developed or in use today are out of growth of early development in semi conductor
transistor. Basically, there are two basic types of transistors:

30
1. The bipolar junction transistors (BJT)
2. The field effect transistor (FET)
In this project work, the bipolar junction transistor, (BJT), was used. Basically, the
bipolar junction transistor (BJT) consists of two back to back, PN junction
manufactured on a single piece of a semiconductor crystal. These two junctions give
rise to three regions called Emitter, Base and Collector.
David Bodanis (2005, Pg. 3) said that; a transistor is a semi conductor device used to
amplify and switch electronic signals. It is compared of semiconductor materials with
all the three terminals for connections to an external circuit.
The invention of the bipolar transistor in 1948 ushered in a revolution in electronics.
Technical feats previously requiring relatively large, mechanically fragile, power-
hungry vacuum tubes were suddenly achievable with tiny, mechanically rugged,
power-thrifty specks of crystalline silicon. This revolution made possible the design
and manufacture of lightweight, inexpensive electronic devices that we now take for
granted. Understanding how transistors function is of paramount importance to
anyone interested in understanding modern electronics.
The functional difference between a PNP transistor and an NPN transistor is the
proper biasing (polarity) of the junctions when operating. For any given state of
operation, the current directions and voltage polarities for each kind of transistor are
exactly opposite each other.

31
Bipolar transistors work as current-controlled current regulators. In other words,
transistors restrict the amount of current passed according to a smaller, controlling
current. The main current that is controlled goes from collector to emitter, or from
emitter to collector, depending on the type of transistor it is (PNP or NPN,
respectively). The small current that controls the main current goes from base to
emitter, or from emitter to base, once again depending on the kind of transistor it is
(PNP or NPN, respectively). According to the standards of semiconductor symbology,
the arrow always points against the direction of electron flow.
Bipolar transistors are called bipolar because the main flow of electrons through them
takes place in two types of semiconductor material: P and N, as the main current go
from emitter to collector (or vice versa). In other words, two types of charge carriers;
electrons and holes comprise this main current through the transistor.
As you can see, the controlling current and the controlled current always mesh
together through the emitter wire, and their electrons always flow against the direction
of the transistor's arrow. This is the first and foremost rule in the use of transistors: all
currents must be going in the proper directions for the device to work as a current
regulator. The small, controlling current is usually referred to simply as the base
current because it is the only current that goes through the base wire of the transistor.
Conversely, the large, controlled current is referred to as the collector current because
it is the only current that goes through the collector wire. The emitter current is the
sum of the base and collector currents, in compliance with Kirchhoff's Current Law.

32
No current through the base of the transistor, shuts it off like an open switch and
prevents current through the collector. A base current, turns the transistor on like a
closed switch and allows a proportional amount of current through the collector.
Collector current is primarily limited by the base current, regardless of the amount
of voltage available to push it. The next section will explore in more detail the use of
bipolar transistors as switching elements.
Bipolar transistors are so named because the controlled current must go through two
types of semiconductor material: P and N. The current consists of both electron and
hole flow, in different parts of the transistor.
Bipolar transistors consist of either a P-N-P or an N-P-N semiconductor “sandwich”
structure.
The three leads of a bipolar transistor are called the Emitter, Base, and Collector.
Transistors function as current regulators by allowing a small current to control a
larger current. The amount of current allowed between collector and emitter is
primarily determined by the amount of current moving between base and emitter.
In order for a transistor to properly function as a current regulator, the controlling
(base) current and the controlled (collector) currents must be going in the proper
directions: meshing additively at the emitter and going against the emitter arrow
symbol.

33
TRANSISTOR AS A SWITCH:
Because a transistor's collector current is proportionally limited by its base current, it
can be used as a sortof current-controlled switch. A relatively small flow of electrons
sent through the base of the transistor has the ability to exert control over a much
larger flow of electrons through the collector.
Suppose we had a lamp that we wanted to turn on and off with a switch. Such a circuit
would be extremely simple.
For the sake of illustration, let's insert a transistor in place of the switch to show how
it can control the flow of electrons through the lamp. Remember that the controlled
current through a transistor must go between collector and emitter. Since it is the
current through the lamp that we want to control, we must position the collector and
emitter of our transistor where the two contacts of the switch were. We must also
make sure that the lamp's current will move against the direction of the emitter arrow
symbol to ensure that the transistor's junction bias will be correct.
The choice between NPN and PNP is really arbitrary. All that matters is that the
proper current directions are maintained for the sake of correct junction biasing
(electron flow going against the transistor symbol's arrow).
Going back to the NPN transistor in our example circuit, we are faced with the need to
add something more so that we can have base current. Without a connection to the
base wire of the transistor, base current will be zero, and the transistor cannot turn on,
resulting in a lamp that is always off. Remember that for an NPN transistor, base

34
current must consist of electrons flowing from emitter to base (against the emitter
arrow symbol, just like the lamp current). Perhaps the simplest thing to do would
be to connect a switch between the base and collector wires of the transistor.
If the switch is open, the base wire of the transistor will be left “floating” (not
connected to anything) and there will be no current through it. In this state, the
transistor is said to be cutoff. If the switch is closed, electrons will be able to flow
from the emitter through to the base of the transistor, through the switch, up to the left
side of the lamp, back to the positive side of the battery. This base current will enable
a much larger flow of electrons from the emitter through to the collector, thus lighting
up the lamp. In this state of maximum circuit current, the transistor is said to be
saturated.
Of course, it may seem pointless to use a transistor in this capacity to control the
lamp. After all, we're still using a switch in the circuit, aren't we? If we're still using a
switch to control the lamp, if only indirectly, then what's the point of having a
transistor to control the current? Why not just go back to our original circuit and use
the switch directly to control the lamp current?
Two points can be made here, actually. First is the fact that when used in this manner,
the switch contacts need only handle what little base current is necessary to turn
the transistor on; the transistor itself handles most of the lamp's current. This may be
an important advantage if the switch has a low current rating; a small switch may be
used to control a relatively high-current load. More importantly, the current-

35
controlling behavior of the transistor enables us to use something completely different
to turn the lamp ON or OFF. Consider where a pair of solar cells provides 1 V to
overcome the 0.7 VBE of the transistor to cause base current flow, which in turn
controls the lamp.
SWITCHES
According to Gladstone, Bernard (1978, Pg. 4), switches are an electrical component
that can break an electrical circuit, interrupting the current or diverting it from one
conductor to another.
In computing a system, there are also used to make selections. Switches are manually
operated but can also work by mechanical, electromechanical, hydraulic or
gravitational means. The varieties in design of switches are all in the market today;
such as open or skeleton, enclosed switch, dimmer switch, push button, toggle and
knife switches etc.
In this project, toggle switch is used. Toggle switch is a class of electrical switches
that are manually activated by hand.
A switch.
Fig. 3.

36
INTEGRATED CIRCUITS (IC)
With the invention of the transistor in 1947 by W.H Brattain and I. Bardeen, the
electronic circuits become considerably reduced in size. It was due to the fact that a
transistor was not only cheaper, more reliable and less power consuming but was also
much smaller in size than an electron tube. To take advantage of small transistor size,
the passive components too were greatly reduced in size thereby making the entire
circuit very small.
In the early 1960’s, a new field of micro electronics was born primarily to meet the
requirements of the military which wanted to reduce the size of its electronic
equipment to approximately one-tenth of its then existing volume. This drive for
extreme reduction in the size of electronic circuits has led to the development of
microelectronic circuits called integrated circuits (IC’s), which are small than their
actual construction is done by Technicians using high powered microscopes.
According to Charles A. Schuler, (1999, Pg. 1), to put it very briefly, an integrated
circuit (IC) is just a packaged electronic circuit. An IC is a complete electronic circuit
in which both the active and passive components are fabricated and tiny single chip of
silicon. Active components are those which have the ability to produce gain e.g
Transistors and FET’s while passive components are those which do not have this
ability e.g Resistors and Inductors.
In this research work, IC CD4066 was used. The table overleaf shows its Logic and
Analogue types.

37
Logic type Analogue
Function family Bilateral switch
Description Quad bilateral switch
Pins 14
Table 2.
The 4066 contain 4 analogue bilateral switches each with an active-high enable input
(A) and two input/output (X and Y), when the enable input is asserted (high), the X
and Y terminals are connected by low impedance; this is the ON condition. When the
enable is low, there is a high impedance path between X and Y and the switch are
OFF.
The 4006 is pin-compatible with the 4016, but has a significantly lower ON
impedance more constant than resistance over the full range of the input voltage;
therefore, the 4006 is preferable to the 4016 in most cases.
SPEAKER OR BUZZER:
Speaker as concerned in this project work is used as an output of the generated signal.
Speaker has a vibration core with a large surface area. When in operation, a large
mass of air in contact with it is set into vibration to produce a loud sound. The figure
below shows the diagram of a loud speaker.
According to Collins English Dictionary (1985), a buzzer is a device that produces a
buzzing sound, especially one similar to an electric bell without a hammer or gong.

38
BEAKER
According to Oxford English Dictionary, (1985), a beaker is a simple container for
stirring, mixing and commonly used in many laboratories. Beakers are generally
cylindrical in shape, with a flat bottom and a lip for pouring. Many also have a small
spout (or beaks) to aid pouring. Beakers are available in a wide range of sizes from
one milliliter up to several liters. Beakers serve many purposes.
1. It is used to hold liquid
2. They are usually used in scientific settings
3. They are commonly used in scientific research as containing containers.
4. They are usually used as containers in which to mix various liquids or as
measuring devices. They are usually made with Boro-silicate glass which can
handle rapid temperature.
5. Being glass, they can reach higher temperatures than plastics so they are
preferable in many science experiments.
BATTERY
According to Richards J. Fowler (2003, Pg. 7), a battery consists of two or more cell
electrically connected together and packaged as a single unit. Although technically, a
battery has two or more cells, the term battery is often used to indicate either a single
cell or a group of cells.
Cells and batteries are classified either as primary or secondary:

39
1. Primary cells are cells that are not rechargeable i.e. the chemical reaction that
occurs during discharge is not easily reversed. When the chemicals used in the
reaction are all converted, the cell is fully discharged.
2. Secondary cells may be discharged many times. Secondary cells include the
following types: Rechargeable Alkaline; Lead Acid; Nickel Cadmium; Nickel
Iron and Lithium Iron cells. Secondary cells are also called Wet cell.
CABLE
A cable is one or more conductors provided with insulation. The insulated conductor
may be provided with an overall covering to give mechanical protection. The
necessary requirements of a cable are that, it should conduct electricity efficiently,
cheaply and safely.
Cables are of different types but for the purpose of this project, six (6) mm² single
core flexible cable size is used for low voltage rating and flexibility. The cable used in
this project work belonged to vulcanized rubber type. Other vulcanized types
included: Poly-Vinyl Chloride (PVC); Mineral Insulated cable; Vulcanized Iron Cable
e.t.c.

40
CHAPTER THREE
3.0. DESIGN AND PRINCIPLES OF OPERATION
This circuit not only indicates the amount of water present in the overhead tank or any
other container, but also gives an alarm when the water is full. The circuit uses the
widely available CD4066 bilateral switch CMOS IC to indicate the water level
through LED’s. When the water is empty, the wires in the tank are open circuited and
the 180k resistors pull the switch low hence, opening the switch and LED’s are off.
The sensing is simply done by using a set of four probes which are placed at four
different levels on the tank walls in the increasing (ascending) order of heights.
Common probe, i.e. Supply carrying probe, Sı, is placed at the base of the tank.
The level four represents the water full. As the water starts filling up, first, the wire in
the tank connected to switch and the supply are shorted by water. This closes the
switch, Sı, and turns the LED 1 ON. As the water continues to fill up the tank, the
LED’s 2, 3, and 4 lights up accordingly. The number of levels of indication can also
be increased to 8 if two CD4066 IC’s are used in the circuit.
When the water is full, the base of the transistor BC148 is pulled high by water and
this saturates the transistors, turning the buzzer ON. The switch then has to be opened
to turn the buzzer OFF. The switch must be ON while pumping up water; otherwise,
the buzzer will not sound.

41
3.1 BLOCK DIAGRAM
Fig. 4.
3.3 CIRCUIT DIAGRAM 9V
13 5 6 10 14
Fig. 5
3.2 PRINCIPLES OF OPERATION
When the water level gets to the probes, a signal is sent to the input BJT and the
circuit become as shown below:
S1 S2 S3 S4
BC
148
330 Ω 330 Ω 330 Ω 330 Ω
Buzzer
Switch
2.2k
180kΩ
3
2
180kΩ
180kΩ
180kΩ
4 9 11
Green
Red
Red
Red
S1 – S4 = IC
Full
3
4⁄
1
2⁄
1
4⁄
Full
3
4⁄
1
2⁄
1
4⁄
2
1

42
9V
R
V०
IC
Q
R₁
R₂
R₃ R₄
9V
Fig. 6.
The Transistor is connected as a switch to the circuit and amplified the input signal. A
general purpose BJT (CD 148) is used in this design. From the fig.6 above, the
transistor must be biased to ICQ and also the D.C current gain of the transistor at
room temperature is β=200.
To bias the circuit in the operating point stated above, a standard value of 180kΩ is
selected for all resistors.
Therefore from the circuit above, we have:
V= the voltage input = 9V
∾

43
∴ The current gain at room temperature;
β = 200 V.
The input resistance of the circuit is:
R=V ⁄ I.
From the data above,
Current gain A₁=V ⁄ I = 200 ⁄ 9 = 22.2kΩ
∴ R₁ = V ⁄ I = 9 ⁄ 22.2 = 0.405KΩ
∴ the current output of the circuit is approximately;
0.41kΩ

44
CHAPTER FOUR:
4.0. CONSTRUCTION TECHNIQUES/DESCRIPTIONS:
The construction of this project is simple but complicated and a very technical one.
The following procedure was followed in the construction of the main circuit board.
1. The strip board was marked with strips running from left to right.
2. All the components were correctly fixed particularly LED’s, transistor and
resistor in the circuit.
3. The integrated circuits (IC’s) were mounted and positioned in such a way that
the correct pins stay in the correct holes.
4. Correct soldering of components was done to ensure good electrical contact.
5. All the wire links were inserted in the right places and their use was minimized.
6. Soldering short circuit was checked.
7. Breaks (both intentional and those that are not intentional) in the copper tracks
were checked.
8. Finally, the strip board was fixed inside a case. Care was taken to ensure that
the board was properly fixed onto the base of the case and that no metallic
object was bridging any of the strip board line.
The container was designed to ensure that the strip board and other components sit
inside comfortably, and that no part of the case in anyway constitutes a hindrance
in the function of the components encased therein. The wooden casing highly

45
insulated is finally covered and screwed firmly to give the whole project a fine
finish.
4.1. SOLDERING TECHNIQUES:
Soldering is a process of joining metals using a low melting point called solder. In
electronics, the metals usually joined are copper wire and lead wire which when
moderate heat capable of melting the lead wire strip is used to solder metallic
components which are glued on the strip board.
4.2.1. SOLDERING CONCEPTS:
A. Solder is used to hold two (or more) conductors in electrical contact with each
other.
B. Solder is not used to make the electrical contact.
C. Solder is not used to provide the main mechanical support for a joint.
D. Solder is used to encapsulate a joint, prevent oxidation of the joint, and provide
minor mechanical support for a connection.
4.2.2. SOLDERING IRONS AND ACCESSORIES:
A. Soldering Iron Types:
1. Temperature-controlled iron:
A soldering iron with electronic temperature control is highly recommended. Irons
without temperature control can reach temperatures that are high enough to
irreversibly damage the tips. Since temperature is not proportional to wattage with

46
this type of iron, the wattage rating is relatively unimportant. A higher wattage iron
results in a faster temperature recovery time between soldering operations (40 W to 60
W units seem to work well).
A .Non-temperature-controlled iron:
Low wattage (10 W to 25 W) pencil-type (not gun-type) can be used but is not
recommended. This type of iron must be unplugged when not in use to save the tips.
The temperature is proportional to wattage and most of these types of soldering irons
will reach temperatures that can destroy tips quickly.
3. Modified, non-temperature-controlled iron:
A 10 W to 40 W pencil-type iron can be operated from a variac to limit the wattage
(and therefore the temperature) and is a reasonable substitute for a temperature-
controlled iron. However, a variac can cost more than a temperature controlled
station and will yield less satisfactory results!
B. Sponge:
A sponge is required for keeping tips clean for best heat transfer. A clean soldering
iron tip is one of the most important steps towards producing good solder joints. Most
soldering stations come with sponges and sponge holders.
C. Tips:
Currently, most tips sold for electronics work are iron-clad copper and have long life
spans. Iron-clad tips cannot be filed or sanded when they become oxidized; they must
be replaced. Many tip shapes are available, but miniature needle or chisel point tips

47
are best for most work. The tip shape should be chosen to provide the highest contact
surface area for best heat conduction. Minimizing the shank length can increase the
heat transfer from the iron (heater) to the tip. Copper tips can still be purchased but are
not recommended because of their short life span and poor wetting properties.
4.2.3. SOLDER AND FLUX:
Flux is used to prepare the surfaces of the conductors prior to soldering. Flux
removes oxidation from the conductors and maintains oxide-free surfaces at elevated
temperature during the soldering process. This allows all surfaces to “wet” properly.
1. The most common flux used in hand soldering of electronic components is rosin, a
combination of mild organic acids extracted from pine trees (some manufacturers use
synthetic compounds).
2. Although fluxes can be obtained in liquid or paste form, they are typically contained
in solders (rosin core) used for hand assembly of electronics. Fluxes labeled as
“Acid” are strong acids (as opposed to the mild rosins) and should never be used for
electronics assembly. B. Solder 1. Rosin core. 60/40 Sn/Pb (M.P. 361-376°F) and
63/37 Sn/Pb (M.P. 361°F) solders are the most common types used for electronics
assembly. These solders are available in various diameters and small diameters are
most appropriate for small electronics work (0.02” - 0.05” dia. is recommended).
LEAD-FREE:
Lead-free solders are used as more environmental-friendly substitutes for leaded
solder.

48
They are typically not as easy to use mainly because of their higher melting point and
poorer wetting properties.
4.2. 5. SILVER:
Silver solders are typically used for low resistance connections but they have a higher
melting point and are more expensive than Sn/Pb solders.
1.2.4. ACID-CORE:
NEVER USE ACID CORE SOLDERS FOR ELECTRONICS! They are intended for
plumbing or non-electronics assembly work. The acid-core flux will cause corrosion
of circuitry and can damage components.
4.2.7. OTHER SPECIALTY SOLDERS:
(a).Various melting point eutectics. These specialty solders are typically used for non-
electronics assembly of difficult to construct mechanical items that must be assembled
in a particular sequence.
(b).Paste solders. These solders are used in field applications or in specialized
manufacturing applications.
TOOLS NECESSARY FOR PROPER SOLDERING:
This is the recommended minimum complement of tools for soldering:
A. Miniature needle-nose pliers
B. Miniature side cutters
C. Wire strippers
D. Solder removal tool (“Solder Sucker”)

49
E. Water bottle F. Safety glasses
F. Lamp with magnifying glass
G. Vise or circuit board holder
H. “Third hand” device
I. Heat sink clips
J. De-soldering station
K. Fume absorber
PREPARATION FOR SOLDERING:
- A. Warm-up:
Allow the soldering iron to reach adequate temperature. The recommended
temperature setting is between 600 and 750° F. Some tips may have recommended
operating temperatures that should be observed.
- B. Clean Tip:
A clean tip promotes heat transfer, and helps to prevents unwanted “solder bridges”
from forming. A heavily oxidized tip will make it impossible to solder properly.
The steps to maintain clean tips are as follows:
1. Moisten sponge.
2. Wipe tip on sponge.
3. “Wet” tip with solder – just enough for a very thin coating.
4. Repeat if necessary to obtain a clean, shiny tip surface. Also, repeat between
each solder operation to maintain a clean tip

50
5. A properly cleaned and “wetted” soldering iron tip.
- C. Prepare surfaces to be soldered:
1. If soldering to a bare copper (non-pretinned) printed circuit board (PCB), the
copper should be cleaned using fine steel wool or other fine abrasive. All oils and
remaining abrasives should be removed with light soap and water followed by an
alcohol rinse. The copper should have a bright, shiny appearance prior to soldering.
2. If soldering to magnet wire or other wire with varnish insulation or with oxidized
surfaces, fine grit sandpaper can be used to prepare the surfaces to be soldered.
WIRE TYPES:
A. Stranded Wire:
1. Stranded wire should be used for connections from PCB to panel-mounted
components, or where wires will be flexed.
2. Strip, twist, and lightly “tin” the wire prior to soldering it in place this prevents
fraying of the conductors. Apply solder sparingly since too much solder may increase
the wire diameter so that it becomes too large or too stiff. A wire prepared in this way
may now be hooked around a terminal or soldered into place on a PCB without
fraying.
3. Stranded wire preparation. 3. 22 – 26 ga. stranded copper wire is recommended and
22 or 24 ga. is most common. 4. For power connections, refer to wire tables (e.g.,CRC
Handbook) to determine the proper gauge to carry the required current: Stripped,
Twisted or Tinned.

51
B. Solid Wire:
1. Solid wire should be used for jumpers on pc boards or for any point-to- point
wiring.
2. Use pre-tinned wire for best results.
3. 22 – 28 ga. solid copper wire is recommended and 22 or 24 ga. is most common
4. For power connections, refer to wire tables (e.g., CRC Handbook) to determine the
proper gauge to carry the required current.
C. Preparation Methods:
(a). Strip the outer insulating sleeve using a sharp knife (e.g., X-Acto knife).
(b). Bend the wire over, split the shield braid and pull the center conductor through the
opening.
(c). Strip the center conductor using a knife or wire strippers.
(d) Twist and tin the center conductor (if stranded type).
(e). Twist and tin the braid.
Construction and Soldering Techniques:
Printed Circuit Board (PCB) Soldering and Construction.
1 .Component mounting:
Components are pushed through from the top side of the board and the leads are bent
slightly to hold the component while soldering.

52
2. Component mounting on PCBs:
(a). The soldering iron tip should be placed in contact with both the trace (foil) and the
lead. The two should be heated only enough to melt solder in order to avoid
damaging sensitive components and to avoid de-lamination of the PCB traces.
(b). Solder is then touched to the area and allowed to flow freely around the lead and
to cover the solder pad. A minimal amount of solder should be applied. Only enough
solder to cover the joint and to form a smooth fillet should be used.
(c). The iron should be removed after the solder has flowed properly and wetted
all surfaces. The component and the board should not be moved until the solder has
hardened (up to several seconds, depending on the lead and trace size).
3. Soldering a component to a PCB:
Solder joints should be inspected when completed to determine if they have been
properly made:
(a). Qualities of good solder joints:
1. Shiny surface.
2. Good, smooth fillet.
(b). Qualities of poor solder joints:
Trace
Pad

53
1.3. STEPS IN SOLDERING
IMPORTANT SOLDERING TIPS
The following tips provide a quick guideline on how to make proper joints in
soldering.
CLEANLINESS:
All parts, including the soldering iron tip, must be clean and free from grease,
oxidation and contamination. Solder does not ﬂow over contaminated areas;
moreover, solder is repelled by dirt. Severe contamination is evident when solder
begins to “bead”. A common source of contamination is oxidation. Old components
and copper boards will often have an oxide layer that prevents a good solder joint.
Ensure all components have shiny leads and the PCB has clean traces. An abrasive
such as a blue or pink eraser, emery paper, or steel wool can be used to remove the
oxidized layer from the PCB board and components.
TINNING:
In addition to being clean, the soldering iron tip must also be tinned (coated with
solder). Tinning the tip allows solder to ﬂow on the components more quickly rather
than the soldering iron tip itself. Tinning involves adding a few millimetres of solder
to the tip and then wiping and rotating the tip on the damp sponge to reveal a shiny
surface on the tip of the soldering iron: a thin layer of solder will coat or “tin” the tip
of the soldering iron. When done soldering, tinning the iron is required to protect the
tip from oxidation thereby dramatically increasing its life.

54
TEMPERATURE:
Ensure that both the component leads and the PCB’s copper layer are heated at the
same time. The soldering iron tip should contact both the component and the PCB
pad. This will ensure that each surface is relatively close in temperature resulting in a
good joint. If there is a temperature diﬀerence between the two surfaces, the solder
will form a “dry” joint. Soldering irons are typically set around 650 Fahrenheit,
depending on the lead-tin ratio of the solder being used. Too much heat causes
excessive “sputtering” of ﬂux, and too little doesn’t melt the solder in a timely
manner.
DURATION:
The duration that the iron is in contact with the component and PCB is dependent on
the size of the joint and your soldering iron temperature. For the typical PCB through-
hole joint, it should take a few seconds to heat the joint and apply the solder. This will
require practice, so don’t expect to be fast if you are a beginner. Excessive heat
(several seconds in duration) will damage sensitive semiconductors. If this is a
concern, use a heat sink attached to the component leads: sometimes as simple as an
alligator clip. These concerns can sometimes be avoided by soldering sockets instead
of the semiconductor itself.
Adequate solder coverage: If too little solder is applied, the joint will not make a
secure connection and will cause erratic behaviour. How- ever, if too much solder is

55
applied, the joint may bridge with adjacent joints resulting inelectrical shorts. How
much solder to apply comes with experience?
HANDLING:
Most modern electronics systems contain static-sensitive devices. Use proper
handling procedures to minimize the likelihood of damage: grounding wrist-straps,
grounded soldering irons, grounding mats, etc.
PRECAUTIONS:
- Soldering Irons get very hot (600-8000ºF, 315-4250ºC), please ensure you
follow precautions during use. Basic safety precautions are listed below.
- Never leave your iron turned on while unattended.
- Turn the soldering iron off when it is not being used. If the iron is left on for
long periods of idle time, the soldering iron tip will be destroyed through
oxidation.
- Eye protection must always be worn when soldering. Hot flux can spit up and
into an unprotected eye. In the Capstone Design Lab, use of eye protection is
mandatory.
- If the cord of the soldering iron is damaged, inform the lab staff who will ensure
it is replaced.
- Never set the soldering iron down on anything other than an iron stand.

56
- To prevent burning your fingers, use needle nose pliers, heat resistant gloves, or
a third hand tool to hold small pieces.
HOW TO SOLDER THROUGH-HOLE COMPONENTS:
Most of the soldering done in the Capstone Design Lab is through-hole. A through-
hole joint is a type of soldering joint in which the component joins with the PCB pad
through a physical hole in the board. The following steps will illustrate how to make a
proper through hole solder joint on a PCB.
1. Ensure that the printed circuit board and all components are clean. Cleaning can be
achieved with a mild abrasive and/or the application of flux.
2. Plug in the soldering iron, turn it on, and let it warm up for 2–3 minutes.
3. Wet the soldering station sponge with the water provided in the lab. Do not wet the
sponge in the bathroom or the water fountain.
4. Clean the tip of the soldering iron and tin it with solder.
5. Insert the component into the holes. Ensure that the component is secure by taping
the component or by using a third hand. Optionally, the component leads can be
clinched. This technique, however, is not recommended for two-sided boards as the
flow of solder to the component side is restricted.
6. Apply the soldering iron tip to one side of joint making contact with the component
lead and the board copperfoil, ensuring that both are heated up to the same
temperature.

57
7. Slowly add a few millimetres of solder to the other side of the joint. DO NOT apply
solder to the soldering iron tip. If enough heat was applied to the PCB pad and
component wire, the solder will flow freely onto the joint.
8. Remove the solder when the joint is suitably covered.
9. If the PCB is double-sided, the solder should flow through the hole around the
component lead and make a bond on the component side of the board (opposite
to the side that the solder was applied). If this “wicking” does not occur, the hole may
be undersized, clinching could be blocking the solder’s path, or the component lead is
not clean.
10. Remove the soldering iron and allow the joint to cool naturally.
11. Cut the lead of the component, if necessary.
HOW TO SOLDER SURFACE-MOUNT COMPONENTS
Surface mount soldering requires more experience and skill than through hole. It is
recommended that one practices with through-hole prior to at- tempting any surface
mount soldering. As the name suggests, surface mount involves soldering a
component to either the top or bottom surface of a PCB. Depending on the footprint,
the pads are usually a spaced closer together (finer pitch), making the soldering more
susceptible to solder bridges, etc.
The actual soldering of the joints is similiar to the through-hole method. One
difficulty, however, is maintaining the part’s alignment on the PCB pads.

58
A good technique is outlined here:
1. Align the component on the PCB pads. This can be aided with the use of tweezers
and dental picks.
2. Secure the component to the PCB by applying a small amount of pressure onto the
top of the component using a small slot screwdriver.
3. Solder one of the corner component leads to the PCB pad.
4. Align the remaining pads and solder the opposite corner PCB pad.
5. Solder the remaining pads in a pattern that does not build-up too much heat in the
device.
4.3. TOOLS USED IN CONSTRUCTION:
The following are tools used in the construction of this project:
- Flat and round file.
- Flat screw driver.
- Star screw driver.
- Pair of pliers.
- Iron brush.
- Soft brush.
- Soldering iron.
- Multi-meter.
- Cutting knife.
- Wire stripper.

59
- 1.2 SWG lead wire.
- Variable temperature soldering iron: used for applying heat to joints during
the soldering process.
- Damp sponge: for cleaning soldering iron tip.
- Rosin-core solder: to electrically and mechanically bond a component to the
PCB.
- Wire cutters or side cutter: for trimming component leads and stripping
insulation from wires.
- Needle nose pliers: for holding, placing and shaping components.
- De-soldering pump and/or de-soldering braid: for removing solder.
- Scotch tape and/or a “Third Hand”: for securing components.
- Safety glasses: for eye protection. These are mandatory in the lab.
- Magniﬁer: to provide more detail during intricate work. A magnifying glass is
convenient, but an illuminated magniﬁer is better.
- Light source: to prevent eye-strain.
- Ventilation: to extract and dispel fumes generated during the soldering process.
- Flux: to clean components and PCB pads.
1.4. MATERIALS USED:
S/№: MATERIAL DESCRIPTION: QUANTITY:
1. Resistor 33Ω 4
2. Resistor 180kΩ 4

60
3. Resistor 2.2kΩ 1
4. Transistor BC 148 1
5. Piezo Electric buzzer 1
6. Sı - S₄=IC 4066 4
7. LED (Red) 3
8. LED (Green) 1
9. Beaker 1
4.5. BILL OF ENGINEERING MEASUREMENT AND EVALUATION
(BEME)
Itemizes the estimated quantities and different types of Works and may include a day
work schedule for unforeseen work outside the Bill of Engineering Measurement and
Evaluation. The BEME has a direct bearing on the cost of the tender, purchase and the
implementation performance.
S/N ITEMS QTY UNIT (₦) AMOUNT(₦)
1 9volts lead acid battery 1 1,500.00 1,500.00
2
Transistor BC 148 1 200.00 200.00
LED 4 100.00 400.00
Resistor 330Ω 4 50.00 200.00
Resistor 180kΩ
4
50.00 200.00

61
Resistor 2.2kΩ 1 50.00 50.00
Switch (SPST ON/OFF) 1 100.00 100.00
IC CD 4066 (Sı –S₄ ) 4 200.00 800.00
3 Vero Board 1 100.00 100.00
4 Cable for wiring ⅛ roll 300.00 300.00
5 Casing 1 2000.00 2000.00
6 Adhesive gum 1 tin 150.00 150.00
7 Soldering lead 1 roll 250.00 250.00
8 Miscellaneous ---- 8,500.00 8,500.00
SUB TOTAL:₦14,750.00
4.6. TESTING:
4.6.1. Testing Connections:
After completely soldering a component to a PCB, it is good practice to ensure
connectivity between the component wire leads and the PCB pads they are soldered
to. A DMM (Digital Multi-Meter) is suﬃcient to determine connectivity; many
DMMs include an audible connectivity setting, but failing this, measure the joint
resistance.
Milled Board Soldering:
In-lab manufacture of PCBs uses a technique known as “milling”.

62
The milling technique involves cutting out the PCB tracks and pads from the copper-
clad board. Due to its construction, a milled PCB is susceptible to solder-bridging
across the milled grooves, particularly when an excess of solder is used. Finding a
short caused by a bridge is a difficult task, particularly when many solder joints exist.
To this end, make a limited number of solder connections and then test for bridges
using a multimeter.
Post-Soldering Cleanup of PCB:
The flux left behind by rosin-core solders, or perhaps as part of the cleaning process,
needs to be removed from the PCB. Due to the flux’s sticky nature, dirt gathers and
contributes to short-circuiting problems. The most frustrating part of this situation is
that a short does not necessarily occur immediately. Weeks, or even years later, a
short can develop. To remove flux, alcohol is used. Apply the alcohol liberally and
then brush away with an acid brush, starting at the center of the PCB and working out
toward the edges. This is a time-consuming task, but a clean board is well-worth the
effort.
Work Area Cleanup:
The importance of keeping your work area clean cannot be emphasized enough. When
cleared of obstructions and garbage, handling a hot soldering iron is safer. The
soldering process itself involves chemicals and sub- stances which are known to have
ill effects in humans. Wiping-down the work-area surfaces with a moist paper towel
will help reduce some contamination. When you are done soldering, wash your hands

63
with soap and water to get rid of contamination. The primary concern here is
accidental ingestion of the chemicals. For more information, please refer to the Safe
Operating Procedures, posted in the lab’s soldering area.
4.6.2 TESTING OF THE PROJECT:
Testing of the project was carried out installmentally. Static test was performed i.e.
without powering the circuit using a multimeter turned to the resistance mode.
Resistance test was performed to ensure there was an open circuit or short circuit in
the circuit board.
Dynamic testing was next carried out. The circuit was finally powered and a voltmeter
was used to check voltage level at different points in the circuit.

64
CHAPTER FIVE
5.0 SUMMARY AND CONCLUSSION
The aim of a project work like this is to enable the student adopt the theories into
the practical realization for the benefit and betterment of mankind.
An Automatic Alarm System to monitor water level was constructed with the
combination of various components with each serving a desired purpose which it
was intended to perform.
Before conclusion, the researchers must confess that, a lot of challenges were
encountered during the construction of the given project and before it was
completed.
The various tests carried out and the results obtained demonstrate that the
Automatic Alarm System to monitor water level achieved its design and
construction aims. The system worked accordingly to specification and quite
satisfactory. The Automatic Alarm System is relatively affordable and reliable. It is
easy to operate, and it provides a high level of accuracy when used rightly in the
manner it is designed to be used. Finally, it reduces stress associated with manual
visual water level indicators.
5.1 RECOMMENDATIONS:
This project work has its limitations among which are time factor, finance and
Technical specifications. This area should be taken into consideration in
subsequent work on the same or similar topic.

65
REFERENCES
1. Charles A. Schuler (1999):Electricity: Principle and application; fifth
Edition, MCGrawhill companies, USA.
2. Richard J. Fowler (2003): NIST. Archive of surface evolver code. Technical
report. http://www.ctcms.nist.gov/solder/archive.html.
3. David Bodanis (2005): Electronics Universe; United States of America.
4. Glastone Bernard (1978): Industrial Electronics; USA.
5. William L. Faisher (1991): Introduction to modern electronics; USA.
6. Collins English Dictionary (1985): Collins English Dictionary; UK.
7. Clyde F. Coombs, ed. Printed Circuits Handbook, Second Edition, 1979,
McGraw-Hill, New York, NY.
8. R. Glass; Electrical wire soldering for beginners: Technical report.
http://www.airheads.org/contrib/solder.html.
9. D. Lauder; How to solder: Technical report, Oct 2001. http://dragon.herts.ac.uk/
eleqdml/teaching/general/soldering/.
10. W. M. Leach.The leach amp. Technical report, (2000): See section on
Assembly of Circuit Boards, http://users.ece.gatech.edu/
mleach/lowtim/part2.html.
11. Serial Tester. Serial tester: Technical report.
http://army-gps.robins.af.mil/tech/Serial-tester/proc06.jpg.

66
12. Faissler, W.L. (1991): An introduction to modern Electronics, Willey, New
York, NY, USA.
13. A. Winstanley: The basic electronics soldering and de-soldering guide.
Technical report,Feb 1999.
14. http://www.epemag.wimborne.co.uk/solderfaq.htm.

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