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

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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 Research Aims

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 Research Objectives

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.

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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.

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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.

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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

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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]

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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

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Figure2.1 dipstick as used in vehiclesFig 2.1 Dip Rod Used In Vehicles

Fig 2.2 Dipstick Used For Underground Tanks

tank. 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

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operator 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

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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.

2.3.1

2.3.2

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]

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Fig 2.5 Sight Glass

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

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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

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

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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.

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

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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

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.

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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.

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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;

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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.

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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 Design Concept

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

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controller with the signal. The display controller then interprets the signal and sends it to the

exact 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

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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

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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.

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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

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3.3.6 Design Calculations

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 ( R 1+R 2 ) C

Both time resistors in the circuit are 1KΩ and the timing capacitor is 220µF. Therefore

Thigh ¿0.69 (1000+1000 ) ×220 ×10−6

¿0.304 s

The discharge path is through only one resistor R 2 so the time that the output is held low is

shorter:

Tlow ¿0.69 ( R 2 )C

¿0.69 (1000 ) ×220 ×10−6

¿0.152 s

Total Period (T) = Thigh +¿ Tlow

= 0.69 ( R 1+2 R 2 ) C

¿0.69 (1000+2 ×1000 ) ×220 ×10−6

¿0.456 s

The output frequency can be found with

f = 1.45(R 1+2 × R 2)C

= 1.45(1000+2× 1000)×220 × 10−6 =2.2 Hz

The fuel tank is designed specifically to store fuel and retain about 9liters.

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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 = 0.012m 30.001m 3

× 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.

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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.

29

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 Components Cost 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 Taken in the Design and 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.

33

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.

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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.

35

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.

36

37

4.3 Principle Of Operation

Fig.4.2 Final Circuit Diagram Designed with AutoCAD 2004

38

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

39

close 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

40

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.

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 23 of VCC (supply voltage), the output drops low and discharge transistor comes

on. The capacitor now discharge through R2. When the capacitor reaches 13 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]

41

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 ( R 1+R 2 ) C

The discharge path is through only one resistor R2 so the time that the output is held low is

shorter:

Tlow ¿0.69 ( R 2 )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 = 1T

= 1.45(R 1+2× R 2)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= R 1+R 2R 1+2R 2

× 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.

42

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.

43

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.

44

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 company\industry.

45

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.

46

REFERENCES

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March 2014]

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how-they-work-

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47

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APPENDIX A

Images of Final Artefact

Complete Unit

Display Unit Fuel Storage Tank

49