1. 1
CHAPTER ONE
INTRODUTION
1.1 Background of the study
The fuel level detector is an electronic system designed to detect, compute and display the level of
fuel contained in a tank.
Fuel is a very important commodity in our present world. Proper storage makes it even a better
way to manage its usage. Fuel sales executives are mostly unaware of the amount or quantity of
fuel present in their tanks and so top-up or continue usage at an estimated measurement. Several
ways of checking the level of fuel have been in existence.
Level Measurements earliest and simplest method of measurement was to insert a pole into a
solution and retracting it to measure the wetted part of the pole. Another earlier method was to tie
knots in a rope and attach a weight to the rope dropping it into a solution and retracting it to see
how many knots were wet to measure the depth of the solution. The pole method is still used today
by fuel stations when fuel is delivered into an underground tank to see how much fuel was
delivered or needs to be delivered. The rope with knots method has been replaced with a float
device attached to the end of a tape or wire and as the float moves up and down, this movement is
indicated on the outside of the tank with a gauge device showing the level of the vessel. [1]
The proposed project is a fuel level detector using relay switching technology that will provide
volumetric analysis and reading of fuel and present the quantity on a Light Emitting Diode (LED)
display.
1.2 Statement of the Problem
Most fuel filling station operators do not know the exact volume of fuel in their tanks as they
perform their daily sales activity. This is because the current instrument used in calculating the
quantity of the remaining fuel is a long calibrated rod. This has proven incorrect measurement as
in some cases as the tank sometimes bend slightly to one side due to some external factors like
pressure acting on the tank. There are also cases of losing certain quantities of fuel as they

2. 2
continuously open and close the tank. Exposing the fuel to the atmosphere causes small amount of
it to vaporize into the atmosphere. With this method, workers are severely exposed to hazardous
conditions since open the tank before measurement is taken.
At times misunderstanding occurs between operators and customers especially when fuel price is
about to be increased. This is because some filling stations decides to hoard the fuel and sell it later
when the price goes up for them to get more profit. This is cheating. Customers won’t know if
truly there is no fuel at the station as there is no mechanism or device to present to them actual
amount of fuel in the underground tank. This case happened recently at almost all filling stations
Ghana.
This project seeks to present a continuous digital display of fuel quantity in tanks to both operators
and customers, reduce the risk in taking those measurements and also the acquisition of accurate
level of fuel without the need of getting close to the tank.
1.3 ResearchAims
This project aims at;
 Monitoring the stock level of underground fuel storage tank.
 Displaying the volume of fuel measured using a designed Light Emitting Diode (LED)
screen.
 Preventing tank operators from running out of fuel with no prior notification.
 Providing personnel safety to operators.
1.4 ResearchObjectives
The main objectives of this project are;
 To provide users (including customers) of fuel tank a system to identify exact quantities of
fuel in the underground storage tank.
 To build circuitry that will provide an easy and reliable way for managing and running fuel
vending business
 To design an intelligent fuel measuring and displaying system to present the level of the
fuel in a digital format on an LED screen.

3. 3
1.5 Significance of the Study
 This system will not only look at measuring the level of fuel but aid in preventing fuel tank
overflow during refilling.
 This will also ensure that fuel tank supervisors and operators are aware of the quantity of
fuel in the tank at all times.
1.6 Scope of the Study
 The system is used to measure the level of fuel stored in its tank only.
 Suitable for tanks at any position, both above and underground tanks.
 Measurement is given in litres only.
1.7 Limitation of the Study
 The fuel tank measuring system will not be able to determine the pressure and temperature
of the fuel.
 The system will measure but will not store the level recorded in memory for future
reference.
 Fuel level detector system will aid in preventing overflow but will not determine the
presence of fuel leakage.
1.8 Structure of the Report
 Chapter one entails background, statement of the problem, aims, objectives, significance,
scope and limitation of the study.
 Chapter two focuses on the literature review.
 Chapter three consists of methodology.
 Chapter four deals with results and discussions regarding the project.
 Chapter five with the summary, conclusion and future recommendation about the project.

4. 4
CHAPTER TWO
LITERATURE REVIEW
2.1 Introduction
Fuel level detector is the design of a system that will provide volumetric analysis and reading of
fuel in its tank and present a digital output on an LCD screen.
Fuel filling station operators and customers are becoming increasingly concerned about the
quantity of fuel available in the underground storage tank. Hence fuel quantity measurement has
emerged as a major area of fuel sale and acquisition. The predominant reasons for this emergence
is the increase in fuel prices which leads to fuel hoarding, shortage in supply making operators to
sell to their loyal customers only, and also the fact that calculating the amount left always requires
an action to be performed by operators.
Filling stations in Ghana have adopted to a traditional way of measuring the quantity of fuel in
underground tank used for their fuel storage. This measurement is done with the help of a
calibrated dipstick which exposes operators to hazards when taken the measurement.
In the following few sections, the concept of idea of level measurement and a summary of existing
relevant technologies used in detecting level measurement will be explained in details.
When analysing how to tackle the problem, the group decided to use electronic means to detect
the level of fuel in a tank. The device will display the amount of fuel in the tank at all time on an
LED screen and also will reduce the risks and hazards involved in using dipstick to take the
measurements.

5. 5
2.2 Basic Concepts of Level Measurements
Level measurement determines the position of the level relative to the top or bottom of the process
fluid storage vessel. [2]
In industries, liquids such as fuel, water, chemicals, and solvents are used in various processes.
The amount of such liquid stored can be found by measuring the level of the liquid in a container
or vessel. The level affects not only the quantity delivered but also pressure and rate of flow in and
out of the container.
2.2.1 Level Sensors
Level sensors detect the level of substances like liquids, slurries, granular materials, and powders.
The substance to be measured can be inside a container or can be in its natural form (e.g. a river
or a lake). The level measurement can be either continuous or point values.
Continuous level sensors measure the level to determine the exact amount of substance in a
continuous manner.
Point-level sensors indicate whether the substance is above or below the sensing point. This is
essential to avoid overflow or emptying of tanks and to protect pumps from dry run. [3]
2.2.2 Classification of Level Measurement
Level measurements are broadly classified in two groups:
 Direct method
 Indirect method
Direct method: The direct level measurement is simple, almost straight forward and economical.
It uses a direct measurement of distance (usually height) from the datum line, and used primarily
for local indication. It is not easily adopted to signal transmission techniques for remote indication
or control. Few examples are:
 Dip Stick (Calibrated Rod)
 Sight Glass
 Floats Gauge

6. 6
Indirect methods: Indirect level measurement depend on the material having a physical property
which can be measured and related to level. Many physical and electrical properties have been
used for this purpose and are well suited to producing proportional output signals for remote
transmission. Few examples are:
 Buoyancy – the force produced by a submerged body which is equal to the weight of the
fluid it displaces.
 Hydrostatic head – the force or weight produced by the height of the liquid.
 Sonar or Ultrasonic – materials to be measured reflect or affect in a detectable manner
high frequency sound signals generated at appropriate locations near the measured
material
 Capacitance – the material to be measured serves as a variable dielectric between two
fixed capacitor plates. In reality, there are two substance which form the dielectric – the
material whose measurement is desired and the vapor space above it. The total dielectric
value changes as the amount of one material increases while the other decreases.
 Conductance – at desired points of level detection, the material to be measured conducts
(or ceases to conduct) electricity between two fixed probe locations or between a probe
and vessel wall. [4]
2.3 A Comprehensive Survey of Exiting Relevant Work
Stated below, are the summary of existing technologies used in the measuring of the quantity of
fuel contained in tank both in industries and fuel vending centers.
2.3.1 Dipstick Level Measurement
A dipstick is one of several measurement devices. Dipsticks is used to measure the quantity of
liquid in inaccessible space, by inserting and removing the stick and then checking the extent of it
covered by the liquid. The most familiar example is the oil level dipstick found on most internal
combustion engines. [5]

7. 7
Other kinds of dipsticks are used to measure fuel levels in underground tank. This dipstick is a
graduated rod or strip dipped into a container to determine the liquid level.
2.3.1.1 How to Calibrate a Dipstick.
In calibrating the dipstick at the filling stations, a gasoline paste which is yellowish in colour is
first applied on the whole length of the dipstick. A container of capacity 100 litres is filled and
poured into the underground tank. The poured fuel is allowed to settle for about 15 minutes. The
stick is now dipped into the fuel in the tank. The paste on the stick that comes into contact with
the fuel changes to red and that level corresponds to the amount/volume of fuel present in the tank.
Figure2.1 dipstick as used in vehiclesFig 2.1 Dip Rod Used In Vehicles
Fig 2.2 Dipstick Used For Underground Tanks

8. 8
This process is repeated until the tank is full and the maximum level is detected or indicated on
the stick.
2.3.1.2 How Dipstick is used to Take Measurement. (Mode of Operation)
Fig 2.3 Dipstick in an Underground Tank
At every sales depot, there is a meter attached to the fuel dispenser. This is responsible for
calculating the amount of fuel that flows through the dispenser, so any sales person on duty knows
the amount or quantity of fuel been sold. For example, if a tank capacity is 4500 liters and dispenser
recorded 500 liters fuel has been sold, the supervisor in charge of station will verify this using the
calibrated dipstick. The depth level indicated on a dip-stick predicts the remaining volume of petrol
left in a cylindrical storage tank .This should read 4000 liters.
Quantity Left = Initial Quantity – Quantity Sold
2.3.1.3 Advantages of Dipstick Level Measurement
Dipstick is very cheap and unrivaled in accuracy, reliability, and dependability. [6]
2.3.1.4 Disadvantages of Dipstick Level Measurement
The dipstick requires an action to be performed, thus causing the operator to interrupt other duties
to carry out this measurement. This system does not provide continuous representation of the
process measurement. Dipstick measuring principle cannot be successfully and conveniently used
to measure level values in pressurised vessels. [6] Also the measuring procedures expose operator

9. 9
to several hazards. Operators inhale the scent of the pressurised fuel anytime they open the tank
and can accidentally fall into the tank.
2.3.2 Float Switch Mechanism
A float is a point level measuring instrument consisting of an object that suspends on top of a liquid
in a tank.
Float sensors involve the opening or closing of a mechanical switch through either direct contact
or magnetic operation of a device which floats on the surface of the measured liquid. [7] With a
mechanically actuated float, switching occurs as a result of the movement of a float against a
switch. The tilting motion of the switch as it floats up and down on the surface of the liquid is
detected by an integrated switch and triggers the switching operation.
Early float systems used mechanical components such cables, tapes, pulleys, and gears to
communicate level. [2]
Fig 2.4 Float Switch Used In a Tank

10. 10
2.3.2.1 Advantages
The float measuring system is moderate and can be used with corrosive liquids, but opening for
tape. They offer a very high switching capacities effects and a high degree of reliability, they are
long-lasting when correctly installed and used – a factor which nowadays is more important than
ever. They are a low cost reliable circuit element.
2.3.2.2 Disadvantages
The major problem with all float devices is that they are subject to mechanical problems due to
the moving parts that become worn and are subject to breakage or defects over time. They cannot
discriminate level values between steps. Due to corrosion and buildup of solutions on the float
causes the device to hang up and give a false indication.
2.3.3 Sight Glass
This is the simplest and oldest level of measuring device. It is straightforward in use; the level in
the glass seeks the same position as the level in the tanks. It provides a continuous visual indication
of liquid level in a process vessel or a small tank and are more convenient than dipstick. [4]
The sight glass is a thick walled glass tube fastened to a gauge cocks with a compression fitting. It
is attached to the tank using upper and lower flanges or fittings. A guard rod is attached above and
below the gauge glass tube to help protect the tube. In some cases, a thicker plastic tube encloses
the glass tube for added protection against breakage. [1]
Fig 2.5 Sight Glass

11. 11
2.3.3.1 Advantages of Sight Glass
The simplicity and reliability of sight glass type level measurement results in the use of such
devices for local indication. When level transmitters fail or must be out of service for maintenance,
or during times of power failure, this method allows the process fluid to be measured. [4]
2.3.3.2 Disadvantages of Sight Glass
A manual approach to measurement, sight glasses have always had a number of limitations. The
material used for its transparency can get dirty and are susceptible to breakage thus presenting a
safety hazard for personnel especially when hot, corrosive or flammable liquids are being
handled.[4] This system can also not be suitable for underground storage tanks.
2.3.4 Magnetic Level Gauge
The Magnetic Level Gauges (as shown below) are the preferred replacement for sight glasses.
Float devices and magnetic level gauges have common similarities, but magnetic level gauges
communicate the liquid surface location magnetically. The float is carried by a set of strong
permanent magnets, rides in an auxiliary column (called the float chamber) attached to the vessel
by means of two process connections. This column confines the float laterally so that it is always
close to the chamber's side wall. As the float rides up and down with the fluid level, a magnetized
shuttle or bar graph indication moves with it, showing the position of the float and thereby
providing the level indication. [2]
Fig 2.6 Magnetic Level Gauge

12. 12
Magnetic level gauges can also be equipped with magnetostrictive and guided-wave radar
transmitters to allow the gauge's local indication to be converted into 4 – 20 mA outputs that can
be sent to a controller or control system.
2.3.4.1 Advantages
The magnetic level gauge can be used to detect the level of fluids having high temperatures, high
pressures, and fluids that are corrosive. [2]
2.3.4.2 Disadvantages
This method of level measurement cannot be used for underground storage tanks. With the
understanding of magnetism, the system can work only if the auxiliary column and chamber walls
are made of non-magnetic material. The float interacts magnetically with an indicator on the
outside of the chamber to show the fluid level inside. Transferring the fluid level information using
the float’s magnetic field isolates the level indicator from the pressure and corrosive properties of
the process media. [8] The chamber walls and auxiliary column will attract the float’s magnet
when made with magnetic material and this will make it impossible to interact with the indicator.
2.4 Review of Best Contribution Providing Rational For the Work
In reviewing the existing technologies of detecting level of fuel, the group realized the float switch
mechanism and the dipstick provide the rational for the work.
Dipsticks is used to measure the quantity of liquid in inaccessible space, by inserting and removing
the stick and then checking the extent of it covered by the liquid. Fuel filling stations in Ghana are
used to the calibrated dipstick measuring system due to the easiest operation mode. Dipstick does
not involve any running cost and also provide accurate value. The device is not poised to
instrument error and once calibration is done, no other calibration is needed for that same tank.

13. 13
Float mechanism involves the opening or closing of a device which floats on the surface of the
measured liquid. With a mechanically actuated float, switching occurs as a result of the movement
of a float against a switch. The motion of the switch as it floats up and down on the surface of the
liquid triggers the switching operation. The float mechanism is used to give a low or high sensing
and alarms, leak detection, overfill shutoff and also provide a wide variety of industries – not
limited to manufacturing, food and beverage, chemical and pharmaceutical, marine, medical, and
fuel/energy management (filling stations).
2.5 Critical Comparison of Technologies
Float switch mechanism is preferred to sight glass because the transparent glass used for reading
the measurement in sight glass operation can become dirty and opaque as time passes by. This
makes level detection very difficult. Also in cases where sight glass is employed to detect level,
an operator needs to get closer to the transparent glass which is normally attached to the side of
the tank before the measurement can be taken. This means of detecting level using sight glass
cannot be used in situations where the tank is underground especially in fuel filling stations. The
tank is positioned beneath the ground and only has a small opening at the top that is used only for
filling the tank and passing the dipstick through when taken measurement. No space for operators
to go down and take measurement. Float mechanism can be used for underground storage tanks.
The float can be located inside of the tank. Floats are attached to the instrument by a lever to an
On/Off switch activated by the movement of the float. [1] The electric signal from the switching
operation can be transmitted to a remote location to be processed and interpreted.
Although the dipstick level measurement is the cheapest among them, it was not preferred to float
because it cannot give continuous reading of measurement since an operator needs to dip the stick
into the tank anytime he wants to know the level. This in turn exposes him to physical hazards.
The float mechanism keeps the operator far from contact with the tank (or the fuel its self) and is
still able to give the level of fuel since the level can be viewed from a designed LED screen. This
also reduces the physical hazards.
Float mechanism even though having some similarities with the magnetic gauge, operates with
efficiency if installed in tanks or environment with magnetic properties. Magnetic gauges on the

14. 14
other hand, gives false measurement indication ones there are magnetic properties close to the tank
by restricting the flow of the magnetic float and follower. Thus, cannot be used on tanks with
magnetic properties.
2.6 Synthesis Of New Knowledge from Existing Work
With the knowledge acquired from the calibration of dipstick and that of float mechanism, the
proposed projects circuit will receive signal from a locally manufactured float switch positioned
at calibrated points on a rod in the tank.
2.7 Introduction To Proposed Work
The topic proposed is a fuel level detector using float switch as a level sensor. The level detector
consist of a power supply, float switch, relay circuit, astable circuit, LED, and a buzzer. The float
switches are arranged on a metallic rod to detect the level of fuel in a tank and send electric signal
to the relay circuit. The relays then sends signal to the designed LED screen to display the quantity
fuel in the tank.
The buzzer beeps to alert operators when the tank is full. Power supply is used to provide desired
DC power signal to the entire unit for proper functioning of its components.

15. 15
CHAPTER THREE
METHODOLOGY / IMPLEMENTATION
3.1 Introduction
This chapter gives the detailed and sequential arrangement of the method used to design and
construct the fuel level detector. It also elaborates on the functions and why some of the
components were chosen for this project. The construction of the circuit and the testing of
components are also explained.
The project detect the level of fuel in an underground tank and interprets it on a displaying unit. It
convert the mains supply of 220VAC to a rectified 12VDC which provides electric signal to four
float switches calibrated at a 3litres interval to the tanks capacity. The output gives a digital display
of EMPTY, 3 LITRES, 6 LITRES, and 9 LITRES / FULL in respect to the switches activation.
The minimum reading is empty whiles the maximum is 9 litres.
The full display and the buzzer were connected to an astable circuit to provide a pulsating display
and beeping sound respectively.
3.2 Study of The Problem
Primary means of studying a problem was first used to collect data from filling station personnels.
The group realize that the use of dipstick is a difficulty that fuel filling station operators are facing
because of the disadvantages it comes with. Visitation was made to four different fuel filling station
in Takoradi, the capital city of the western region of Ghana, talked to the operators and recorded
their feedbacks on the operation, merits and demerits of using the calibrated dipstick to measure
the level of fuel in an underground tank using a mobile phone.
General overview of the input from the operators and managers at the filling stations are stated
below;

16. 16
 Operators: Picking the level of fuel in the tank using a dipstick is not a safe and healthy
activity. It exposes operators to unfavorable condition each time the tank is opened for
measurement to be taken. Those allergic to fuel scent always complain of headache and
flu. They sometimes lose valuable items such as money, mobile phones and pens as these
items accidentally fall into tank when opening or closing it.
 Station Managers: The artefact will help the general public to understand fuel vendors
when there is no fuel at the station for them not to think that fuel operators are hoarding
the fuel and later sell it when the price goes up. “This is a very nice innovative project.
Wish the government invest enough money into it for you people to make it on a larger
scale”, said by one manager.
Also, investigations were made into other technologies not primarily used by filling stations but in
process industries on how to measure the amount of fluids present in vessels through secondary
means using the internet.
3.3 How Research Methods and Procedures Was Performed
Firstly, the manager at Total Ghana, Takoradi and that of other fuel stations were consulted and
they gave the go ahead to do the investigations on their operations and also acquire information
from their operators. The recordings were taken back to the classroom and analyzed to get the best
information that will help in solving the problem. The internet and other electronics books also
came in handy and from which was consulted to know some other relevant technologies that exist
and to get information about components that can be put together to design a circuit to solve the
problem.

17. 17
3.3.1 Solution Approach
During the design approach, considerable steps were taken to build an entire measuring system
that eliminates the risks and difficulties involved in taking the measurements of fuel. Comparisons
were made between the technologies and finally a decision was made to synthesize dipstick and
floating processes to come out with a system, which can detect the fuel level in the tank
automatically and present an output on an LED display unit with a continuous display.
Knowledge acquired from both dipstick and float mechanism were combined to construct a sensor
made of floating objects attached to a calibrated rod. Also a circuit was put up to understand
electric signals from the sensor and interpret them on a display unit. The display unit is made up
of properly arranged LED’s that illuminates precisely to show the interpreted output signal.
3.3.2 DesignConcept
Fig 3.1 Fuel Level Detector Block Diagram
The figure above is the block diagram of a fuel tank level detector. The power supply provides a
DC voltage at desired value to all the components for proper functioning. The sensor (float
switches) measures the level of fuel stored in a tank and sends electric signal into the automatic
switching circuit consisting of normally open (NO) relays which closes to feed the display
controller with the signal. The display controller then interprets the signal and sends it to the exact

18. 18
LEDs to be illuminated. The buzzer beeps when the received signal is for the FULL display. The
beeping and FULL illumination are controlled by the pulse from the astable circuit.
3.3.2.1 Working Diagram
Fig. 3.2 Flow Chart for the Level Detector Designed with AutoCAD 2004

19. 19
3.3.3 Components Specifications
Table 3.1 Components Specifications
S/No. Item Specification Quantity
1 Rectifier Diode IN4007 32
2 Electrolytic Capacitor 35V 3300 µF 1
35V 4700 µF 1
25V 220 µF 1
3 PNP Transistor TIP42C 1
4 Resistor 1 KΩ 2
1.8 KΩ 1
5 Light Emitting Diode (LED) Red 95
Green 117
6 Relays 12VDC / 10 A 7
7 IC NE 555 Timer 1
8 Float Switch (Sensor) 4
9 Buzzer 1
10 Centre Tap Transformer AC 220V / 240V 50Hz
DC 12V×2 300 mA
2
11 PC Board Big Size 1
12 Fuse 250V / 500 mA 1
13 ON – OFF Switch 125V 12A AC250V 1
14 Connecting Wires
Source: Researchers (2014)

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3.3.4 Components Analysis
The components were tested one by one using analogue multimeter. The reasons for selecting the
specific components and observations after testing are stated below;
3.3.4.1 Resistor
Before testing the resistor, the analogue multimeter’s Range Selector Knob (RSK) was set to
continuity. The multimeter leads were then connected to the resistor’s terminals. The meter’s
indicator pointer moves meaning the resistor is good.
The colours of the resistors were used to determine their sizes.
1 KΩ is Brown – Black – Red
Two 1 KΩ resistors were connected in series in the astable circuit to determine the high and low
period of the 555 timer output.
1.8 KΩ is Brown – Gray – Red
This was connected at the timer’s output to reduce the voltage entering the transistors base. The
base voltage shouldn’t be more than 3V.
3.3.4.2 Capacitor
The RSK was set to continuity. The common lead of the multimeter was connected to the negative
terminal of the capacitor (normally painted with ash colour) and the positive lead to the positive
terminal. The capacitor charges and discharge indicating it is good.
The capacitance of a capacitor determines how smooth the DC signal will be. The 3300µF
capacitor was used in the first rectification circuit to smooth the DC signal used for the relays.
4700µF was used in the second rectification circuit to make the signal controlling the 555 timer
smoother than that controlling the relays.
3.3.4.3 Diode
The RSK was set to continuity. The positive lead of the multimeter was connected to the anode
and the negative lead to the cathode of the diode. This gave a low resistance meaning the diode is

21. 21
good. Changing the polarities gave high resistance. When both sides (after changing the polarities)
gives same resistance, it means the diode is not functioning. IN4007 rectifier diodes were used in
the circuit. Eight were used for rectification purpose and the remaining twenty for preventing
reverse current.
3.3.4.4 Light Emitting Diode (LED)
The RSK was set to continuity. The positive lead of the multimeter was connected to one terminal
of the LED and the negative to the other. The LED illuminated and the meter reads meaning the
LED is good and its terminal is same as that of the meter leads. Ninety – five red LED’s were used
for the FULL and EMPTY display. One hundred and seventeen green LED’s were also used for
the 7 segment and LITRES display.
3.3.4.5 PNP Transistor
For a PNP Transistor, positive is common to the collector and emitter.
The RSK was set to continuity. The positive lead of the multimeter was connected to one terminal
of the transistor. The expectation was that, after connecting the negative lead to the remaining two
terminals separately, the multimeter’s pointer should move which means the terminal with the
positive lead is the base of the transistor. The transistor has three terminals. The other two were
indicated in the following format;
Base Collector Emitter
Collector Base Emitter
Emitter Collector Base
The FULL LED’s and Buzzer need high voltage to operate. TIP42 PNP transistor was selected to
provide 12V output for the buzzer and FULL LED’s connection.

22. 22
3.3.4.6 Relay
The relay is made up of coils. A good relay should read high resistance. The leads of the multimeter
were connected to the coils outlet of the relay. This read high resistance meaning the relay is good.
To know the normally closed (NC) and normally open (NO) terminals, one lead was connected to
the common and the other to the relay switch terminal. This gave out a reading on the multimeter
meaning the switch is a NC switch and the other is a NO switch.
To get the polarities of the relay, a rectifier diode was connected across the coils outlet. This
makes the relay get the same polarities as the diode.
Seven 12V / 10A relays were used to control the circuit’s current flow.
3.3.4.7 Transformer
The primary side of the transformer reads higher resistance than the secondary side. The
multimeter was used to determine it. Two 220V/12V transformer were used to give two separate
voltages for the circuit operation.
3.3.4.8 Fuse
The RSK was set to continuity. The leads of the multimeter was connected to the fuse terminals.
The multimeter read indicating the fuse is good. 250V / 500 mA was used to protect the circuit
against excessive current.
3.3.4.9 Buzzer
The RSK was again set to continuity. The positive lead of the multimeter was connected to the
negative terminal (black lead) of the buzzer and the negative lead connected to the positive (red
lead) of the buzzer. The buzzer beeps indicating it is good. The buzzer was used to beep when the
tank is full.

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3.3.5 Circuit Design
The diagram below is the actual circuit design of the project.
Fig 3.3 Circuit Diagram Designed with AutoCAD 2004

24. 24
3.3.6 DesignCalculations
The popular 555 IC timer was used in an astable arrangement. The IC, two external resistors, and
a capacitor were connected together in the circuit to control the high (ON) and low (OFF) periods
of both the FULL LED’s and the buzzer.
The charged path for the astable circuit is through two resistors and the time that the output will
be held high is given by
Thigh = 0.69( 𝑅1 + 𝑅2) 𝐶
Both time resistors in the circuit are 1KΩ and the timing capacitor is 220µF. Therefore
Thigh = 0.69(1000+ 1000)× 220 × 10−6
= 0.304𝑠
The discharge path is through only one resistor 𝑅2 so the time that the output is held low is shorter:
Tlow = 0.69( 𝑅2) 𝐶
= 0.69(1000)× 220 × 10−6
= 0.152𝑠
Total Period (T) = Thigh + Tlow
= 0.69( 𝑅1 + 2𝑅2) 𝐶
= 0.69(1000 + 2 × 1000)× 220 × 10−6
= 0.456𝑠
The output frequency can be found with
𝑓 =
1.45
(𝑅1 + 2 × 𝑅2)𝐶
=
1.45
(1000 + 2 × 1000)× 220 × 10−6
= 2.2Hz
The fuel tank is designed specifically to store fuel and retain about 9liters.

25. 25
3.3.6.1 Body Casing Design
Fig. 3.4 Size of Aluminum Metal Sheet
The formula for finding volume of a cuboid was used to calculate the capacity of the tank.
Volume of Cuboid = Length (L) × Breath (B) × Height (H)
L= 0.32m, B= 0.21m, and H= 0.18m
Using the equation formula
Volume = 0.32m × 0.21m × 0.18m
= 0.012m3
3.3.6.2 Conversion from meter cube (m3) to liters (l)
0.001m3 = 1l
0.012m3 =
0.012m3
0.001m3
× 1𝑙 = 12l
The total capacity of the tank is 12l. But the group decided to calibrate the sensors (float switches)
to see the tank as full when the fuel level is at 9l. A tolerance of 4l was given to prevent leakages
due to the construction done at the top of the tank.

26. 26
3.3.7 Procedures Used for the Construction of the Project Artefact
Before the whole circuit design was started, one had to be certain that all the component were in
good condition.
A transformer was used to step down 220VAC to 12VAC. Four rectifier diodes were connected
together. To obtain a pulsating direct current (DC), a rectification circuit was built by connecting
the anode and cathode of two diodes to one terminal of the secondary side of the transformer.
Again, another anode and cathode of two diodes were connected to the other terminal of the
transformer’s secondary side. The positive and positive sides of the diodes were connected
together and the negative and negative sides of the diode were also connected together. These are
to obtain a pulsating direct current (DC).
Diodes were connected across the coils outlet of the relay. The positive side of the diode was
connected to the main voltage that is VCC. The negative side was connected to ground through the
float switch. The float switches were fixed on a calibrated dip – rod nicely constructed inside the
fuel tank.
The output of the relay connected to the first float switch was then connected in series to a
rectifying diode to an LED indicator. The same principle was applied to the second and third
switches. The output of the fourth switch was connected to a 555 timer that generates an astable
pulses. The output of the integrated circuit (IC) carrying the pulses was connected to a transistor
that amplifies the current to illuminate the “FULL” LED’s and sound a buzzer. Diodes were
connected in the circuit to prevent reverse current.
The tank was constructed with galvanized steel material to have a capacity of 12 liters equivalent
to 2 gallons of fuel.

27. 27
3.3.8 Casing / Packaging
The circuit board and the display unit were connected together. Black Teaser (leather) was used as
the background of the displaying unit. Paper pad was placed behind the teaser to prevent heat. The
whole unit was then placed in an aluminum frame and screwed together. A wooden structure was
constructed inside the frame to support the circuit board. A glass was placed in front of the frame
to provide protection to the LED’s and for beautification.
The dimension of the final artefact is 44cm × 36cm × 10cm.
Also, the whole unit was cased to due to the following reasons;
 To prolong the life cycle of the electronic component which requires a reliable packaging
to prevent it from the effect of climatic changes or bad weather conditions.
 To enclose the circuit to prevent it from external mechanical hazard.
 To prevent the user from the risk of electric shock.
The tank was galvanized with black paint to prevent it from rusting.
Fig. 3.5 Underground Tank

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3.3.9 Testing / Validation / Verification
The final piece was tested in the lab. The LED’s determine the output and state of the system. The
device was connected to the power supply and switched ON. The LED for “empty” indication
came on.
The system was constructed such that the tank is seen as empty when the fuel quantity is 1 litre or
when there is no fuel in the tank. This was done to prevent the tank from drying up which can lead
to rusting.
Gradually the tank was being filled with petrol. When the petrol level reached the second switch,
the switch activated and 3 litres displayed on the output. This means that the amount of fuel in the
tank is 3 litres. The filling process was continued and the level of the petrol reached the next switch,
activated it and 6 litres showed, meaning the quantity is 6 litres. Finally the level got to the last
float switch, activated to close it and the output was 9 litres, FULL and a beeping sound from the
buzzer.
The tank’s valve was opened to reduce the petrol level and observations recorded. The output
changed from the FULL indications back to 6 litres. This means that the FULL switch is
deactivated and the 6 litres switch is activated in the circuit. The level was further reduced and the
output changed to 3 litres, indicating 6 litres switch is deactivated and the 3 litres was in circuit.
Finally the output displayed EMPTY which means the fuel level is very low and only the empty
switch is active.
When there is power outage during operation, the output display will be the same as that of the
activated switch when the power is restored.

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3.3.10 Costing and Cost Analysis
Table 3.2 ComponentsCost Analysis
S/No. Item Specification Quantity Unit Cost
(Gh₵)
Sub Total
(Gh₵)
1 Rectifier Diode IN4007 32 0.50 16.00
2 Electrolytic Capacitor 35V 3300 µF 1 4.00 4.00
35V 4700 µF 1 4.00 4.00
25V 220 µF 1 2.00 2.00
3 PNP Transistor TIP42C 1 4.00 4.00
4 Resistor 1 KΩ 2 0.50 1.00
1.8 KΩ 1 0.50 0.50
5 Light Emitting Diode
(LED)
Red 95 0.50 47.50
Green 117 0.50 58.50
6 Relays 12VDC / 10 A 7 4.00 28.00
7 IC NE 555 Timer 1 4.00 4.00
8 Float Switch (Sensor) 4 50.00 50.00
9 Buzzer 1 3.00 3.00
10 Centre Tap Transformer AC 220V/240V 50Hz
DC 12V×2 300 mA
2 10.0 20.00
11 PC Board Big Size 1 5.00 5.00
12 Fuse 250V / 500 mA 1 0.20 0.20
13 ON – OFF Switch 125V 12A AC250V 1 3.00 3.00
14 Tank Construction 200.00 200.00
15 Fuel 4gl 10.00 40.00
16 Casing / Packaging 50.00 50.00
17 TOTAL 540.70
Source: Researchers (2014)

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3.3.11 Implementation
The tank will be placed underground and connected with the help of wires running through
conduit pipe to the device. The device consist of the main circuit and display unit packed
together in one case. The unit should be mounted on the office wall or placed on a table. The
place of mounting should be visible to everyone in and around the office.
3.3.12 Precaution Measures Takenin the Designand Construction
During the design and construction of this work the group
 Ensured that the working area was clean and also avoided water at all times when working
with electricity.
 Made sure that soldering iron being used for construction was place on a heat sink when
hot
 Ensured that the circuit had earthing system.
 Provided a fuse to break flow of high current from entering the circuit
 Ensured complete isolation to ground when working
 Ensured the switches in the tank would not produce ignitions.

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CHAPTER FOUR
RESULTS AND DISCUSSIONS
4.1 Introduction
The circuit operates in sequential process from one component to the other. This chapter explains
the detailed operation of the device. In addition, a comparison was made between the final device
and existing techniques.
4.2 Detailed Explanation of the Block Diagram
Fig. 4.1 Fuel Level Detector Block Diagram
The figure above is the block diagram of a fuel tank level detector. Below is the detailed
explanation of the block diagram.

32. 32
Power Supply: The project’s circuit comprises of two power supply with one source. The negative
output of the first rectification circuit serve as common current source to the float switches on the
dipstick which further goes to ground. The positive output is connected to the positive terminals
of the relay coils outlets. For the second rectification circuit, its negative output signal is sent to
the negative terminals of the buzzer, electrolytic capacitor in the astable circuit and Pin 1(earth) of
the IC. This signal is later sent to ground. The positive output is connected to the relays common
terminals. Two full bridge rectification circuits were used to provide a desired 12VDC to all the
components for proper functioning. This helps in avoiding voltage drops in the operation.
Sensor: The sensor is a locally manufactured float switch using a floating material and aluminum
sheet. A piece of the aluminum sheet is placed on the floating material and four others fixed within
uniform intervals on a dipstick. Four floating materials were used. The dipstick was calibrated
within 3 litres intervals to the capacity of the tank used in the project. The first sensor is found at
the bottom of the dipstick and it is used to measure the fuel level when the tank is empty or fuel
level is less than 3 litres. The other three sensors are positioned on the calibrated points on the
dipstick. The second sensor measures 3 litres, third measures 6 litres and the fourth which the last
one at the top of the dipstick measures 9 litres. The sensors activate during filling and emptying of
the tank. When the level gets to the floating material, it pushes the material upwards to hit the fixed
aluminum sheet to close the switch. Electric signal is sent to display the fuel level depending on
the sensor activated. During the emptying process the fuel level decreases and this causes the
floating material to move downwards from the fixed aluminum sheet. The switch opens and signal
flow ceases. The next sensor below activates automatically with the help of the switching circuit
Fuel: This is the content of the tank. Petrol was used.
Automatic Switching: The automatic switching contains seven relays switching devices. Four of
which are connected directly in series to the sensors. These ones are activated by the sensors to
send electronic signal to the control display through the remaining three relays. The three relays
are positioned to receive signal from a previously activated relay to the display controller and also
activated by the switching of the next switch to isolate the previous relay signal from the display
controller.

33. 33
Display Controller: The display controller receives signal from the relays output. This is a group
of diodes used to control the display unit basically the seven segment display. It splits the output
of an activated relay to give the desired figure needed on the segment.
Example when S2 is closed, the expected display is 3. The display controller picks the output from
R4 and split it into five signals namely a,f,g,e,d and the number 3 is produced from the seven
segment. When S3 is closed, R6 output is divided into six signals. These signals illuminate
a,b,g,c,d,e and 6 is produced from the segment. S4 closes and output from R7 is also divided into
six signals to illuminate a,b,g,f,e,d to produce the figure 9. The diodes are used to control and
prevent reverse current.
Astable Circuit: This is a configuration of 555 timer integrated circuit which produces a uniform
pulsating output signal to illuminate the FULL LED’s and beeps the buzzer simultaneously.
Display Unit: This comprises of the FULL, SEVEN SEGMENT, and EMPTY LED’s. They
illuminate to indicate the amount of fuel in the underground tank as received from the display
controller.
Buzzer: The buzzer receives its signal from the astable circuit. It beeps only when the tank is full.

34. 34
4.3 Principle Of Operation
Fig.4.2 Final Circuit Diagram Designed with AutoCAD 2004

35. 35
Below is the detailed explanation of the above circuit;
The artifact is designed to monitor the level of fuel present in an underground tank and display the
measured level on a screen. In achieving this result, the system went through a number separate
circuit operations.
In the power supply circuit
The power supply transformed a 220VAC of supply voltage to 12V. The system used two
transformers for its operation. The transformed voltage passed through a rectification circuit made
up of four diodes and a capacitor. The negative electric current of the rectified voltage goes to the
floating switches and the positive goes the relays. The second transformer also rectified the 12VAC
to 12VDC and its positive electric current flows through to the common (C) contact of the relays
and the negative of the rectified voltage flows through to the negative terminal of all the
components and also served to earth.
The following is how the switches operate to get the output of the final display.
From the above circuit, when switch S1 is closed by the float, electric signal is sent to its related
relay R1. The signal sent energizes the coils of R1 to cut supply to the normally closed (NC)
terminals and close the normally open (NO) terminal circuit to allow current flow. The NO of R1
is connected to the NC of R2 and allows current flow through to illuminate the designed EMPTY
LEDs.
Fig. 4.3 Empty Display
As the level of the fuel rose, it pushed up the float to switch S2. When S2 is switched on, current
flows from the switch to the relay R3 and R2. The current flowing to R2 from S2 energizes the
coils of R2 to change its NC to an open terminal and isolate the current flowing from R1. Current
from S2 to R3 energizes the coils of R3 to also change its NC and NO terminals to open and close

36. 36
respectively. Current then flows from the NO terminal to the NO terminal of R4 and then through
diodes “a,f,g,e,d” to illuminate the designed LITRES LEDs arrangement and to the seven segment
display to illuminate the LED connections “a”, “f”, “g”, “e” and “d” to represent 3.
Fig. 4.4 3 LITRES Display
Continuous filling of the tank increased the fuel level to reach the switch S3 and activated it. As
S3 is closed, the electric current flows through to energize R5 and allow the current to flow through
its NO terminal to the NC contact of relay R6. The closing of S3 energized the relay R4 to open
its NC contact to isolate the incoming current from the previous switching. The current from R5
flows through R6 to maintain the illumination of the LITRES and to the seven segment display to
also illuminate the LED connections “a”, “b”, “g”, “c”, “d” and “e” representing 6.
Fig. 4.5 6 LITRES Display
The final switching stage was when the fuel level reached the switch S4. S4 closed to supply
electric current to relays R6 and R7. In R6, the current energizes the coils to isolate the previous
switching that showed the display of 6. The current from S4 also enters R7 to energize its coils to
allow current to pass through its NO contact and flow through to maintain the illumination LITRES
and to the seven segment display to illuminate the LED connection “a”, “b”, “g”, “f”, “e”, and “d”
to display 9. The current also flows to the 555 Timer which creates a pulsating current to illuminate
the FULL LEDs. This LEDs blinks at a uniform interval of 0.3seconds high and 0.15seconds low.
The rate of the on and off of the FULL is same as the sound the buzzer produce. The operation of
the 555 Timer is well explained in the next page.

37. 37
The diodes a,b,c,d,e,f, and g prevent reverse current to the relay circuit and switches.
.
Fig.4.6 FULL and 9 LITRES Display
4.3.1 Operation of 555 Timer IC
Fig. 4.7a Astable Mode Timer Configuration Fig. 4.7b Output Waveform
Fig. 4.1a shows the timer configuration for astable mode. The trigger (pin 2) is tied to the threshold
(pin 6). When the circuit is turned on (switch S4 activated), timing capacitor C is discharged. It
begins charging through the series combination of R1 and R2. When the capacitor voltage reaches
2
3⁄ of VCC (supply voltage), the output drops low and discharge transistor comes on. The capacitor
now discharge through R2. When the capacitor reaches 1
3⁄ VCC, the output switches high and the
discharge transistor is turned off. The capacitor now begins charging through R1 and R2 again.
The cycle will repeat continuously with the capacitor charging and discharging and the output
switching high and low. [9]
The charge path for the astable circuit is through the two resistors and the time that the output will
be held high is given by
Thigh = 0.69( 𝑅1 + 𝑅2) 𝐶

38. 38
The discharge path is through only one resistor R2 so the time that the output is held low is shorter:
Tlow = 0.69( 𝑅2) 𝐶
The output waveform is nonsymmetrical. The total period (T) can be found by adding Thigh to Tlow.
The output frequency will be equal to the reciprocal of the total period. The output frequency can
also be found with
𝑓 =
1
𝑇
=
1.45
(𝑅1 + 2 × 𝑅2)𝐶
The duty cycle D of a rectangular waveform is the percentage of time that the output is high. It can
be found by dividing the total period of the waveform into the time that the output is high. For the
astable circuit used in the project circuit, the duty cycle can be found from
𝐷 =
𝑅1+𝑅2
𝑅1+2𝑅2
× 100%
𝐷 =
1 × 103
+ 1 × 103
1 × 103 + 2(1× 103)
× 100% = 66.7%
4.4 Comparison with Existing Technique
Fuel filling stations are currently using dipstick as the only means of measuring the amount of fuel
in their underground tanks. The major aim for this project was to come out with an electronic
device which can monitor the fuel level in an underground tank and present it digitally on a
displaying unit. Comparing the final device to the dipstick currently used by the filling stations,
the following strengths and weaknesses were identified.
4.4.1 Strengths of the Artefact
 Fuel level is presented continuously in a digital format.
 Measurement can be taken without nearness to the tank.
 Operate in a safer mode that life and properties are protected.
 Time spent in taken measurement is very minimal.
 The buzzer warning helps to reduce over filling of tank.

39. 39
4.4.2 Weakness of the Artefact
 The device works on its tank only.
 There is no subsequent grading between the calibrated points. That is level between them
can’t be recorded.

40. 40
CHAPTER FIVE
SUMMARY, CONCLUSION AND RECOMMENDATIONS
5.1 Introduction
This final chapter typically consists of a summary, conclusion, and recommendation of the
dissertation. The summary repeats in few detail the major findings. Conclusion explores
implications of the findings. It is the opinion formed after considering relevant facts form the
findings. And finally, recommendation based on the strength of the findings and provide
suggestions for further research into the entire topic or an aspect of it.
5.2 Summary of Findings
Having undergone through intensive research, it can be stated that the set aims and objectives of
this project have been successfully achieved. The various tests carried out and the results obtained
demonstrate that the fuel level detector has achieved its design and construction aims. The system
worked accordingly to specification. The fuel level detector is relatively affordable and reliable. It
is easy to install. Finally, it reduces stress associated with manual detection of fuel level.
5.3 Conclusion
In the research to the design and construction of fuel level detector, it was realized that there isn’t
any electronic device available for fuel filling stations to use in detecting the level of fuel in tanks
because of the implications relating to fuel and electricity. Fuel is very flammable and can ignite
with the presence of electrical charges or sparks. Critical study was made in the construction to
remove the charges/sparks that can be produced by the switches.
Irrespective of the challenges encountered, the design and construction of this project, fuel level
detector was a successful venture. The design and fabrication of this fuel measuring system has
been tested and found workable. The machine can be used in filling stations, refinery and any fuel
consuming companyindustry.

41. 41
5.4 Recommendation
The Fuel Level Detector was constructed with purely electronic components and for it to function
effectively and maintain its durability, the following recommendations were made for it effective
usage and further research into the entire topic or aspect of it.
 For effective operation of the device, the main unit should not be placed where there is
much humidity like in the tank farm.
 The sensors (float switches) should be cleaned at constant intervals to remove dirt particles
which restrict free movement of the switches reducing it conductivity.
 Students who partake this project in future should employ a fuel leakage detection sensor
into the system. This will help save the extra cost involved in using the pressurized method
to detect leakage in the tank.
 Ultrasonic range finder can be used to give accurate volumetric reading at all levels.
 Improvement on this design is necessary to enable accommodates larger storage tanks.

42. 42
REFERENCES
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44. 44
APPENDIX A
Images of Final Artefact
Complete Unit
Display Unit Fuel Storage Tank