COLLEGE OF ENGINEERING (COETEC)

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

ELECTRONICS AND COMPUTER ENGINERING

FINAL YEAR PROJECT REPORT

PROJECT TITLE

AUTOMATED WEIGHBRIDGE SYSTEM

PRESENTED BY

WACHIRA PATRICK WERU EN272-0357/2007

DATE: 4TH

DECEMBER 2012

ACADEMIC YEAR: 2012/2013

Project supervisor:

Mr. G.K. Irungu

This project report is submitted to the department of Electrical and Electronics

engineering in partial fulfillment for the award of a degree in Bachelor of Science

Electronics and Computer Engineering.

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DECLARATION

I declare that this project is my original work. I also affirm that this project has not been

presented in this or any other university or institution for examination or for any other

purpose.

Signature:………………………………………….Date:………………………………..

Wachira Patrick Weru

EN272-0357/2007

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CERTIFICATION

This is to certify that the above named student carried out the project work detailed in this

report under my supervision.

Signature: ………………………………………Date: …………………………………..

MR. Irungu G.K.

Project Supervisor

Department of Electrical and Electronic Engineering.

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DEDICATION

I would like to dedicate this project to my family who have always stood by my side and

offered counsel to me at all stages of my life. May God guide you and bless you.

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ACKNOWLEDGEMENT

I thank God for giving me the strength, courage and knowledge to complete this project.

I also thank Mr. G.K. Irungu, my supervisor, who has been there to guide and motivate

me in the choice of the project and on the progressive development of the same. The

assistance he has offered has been very instrumental in meeting the set objectives.

I would also like to extend my gratitude to the entire Electrical and Electronic

Department for the facilitation of the development of this project, including but not all,

the laboratory technologists for their continued support, the projects’ coordinators for

their timely communication and all lecturers for the knowledge they have imparted to us,

students.

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PROJECT ABSTRACT

Road authorities have been using weighbridges as a means of checking the conformance

of transporters to the load restrictions rules. Weigh bridges includes a plate where the

vehicles wheels are driven and positioned on and the vehicle load can be measured from

the force exerted on the plate which has an underlying weight measuring equipment such

as coil spring or strain gauges. The output of the measuring unit is then converted to an

electrical signal which is then taken to a display where it is read and the decision made on

whether the vehicle is overloaded or allowably loaded and then the corresponding

measures taken such as allowing the vehicle to proceed on if allowably loaded or pay a

fine if overloaded. A record of the same is maintained and the driver issued with a receipt

to reflect the process.

This project still uses the same weighing principle and the display part but has the signal

to the display or output tapped and fed to a microcontroller which will intelligently

determine the activity to initiate according to the input signal level.

If the vehicle has the allowed weight, the microcontroller is expected to trigger the barrier

opening by enabling the barrier control unit. If the vehicle is overloaded, the

microcontroller is expected to output a signal notifying the driver of the overload amount

and the amount that need be paid. The RFID chip attached to the vehicle contains the

relevant information of the vehicle including a linked account which is debited the owing

sum and once the transaction is successfully completed, the microcontroller triggers the

barrier to open. If the transaction fails, the driver is prompted to park off the road to pave

way for others.

The project also aims at developing a database where every transaction is registered for

future reference and also for accountability. This also helps in identifying the defiant

transporters who form a habit of persistently overloading their vehicles and provide a

chance to charge them.

In summary, the project involves three stages, namely: weighing stage, verification and

transaction stage and finally the barrier control stage.

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LIST OF FIGURES

Figure 2.0 Simple system diagram ……..……….…………………………………….3

Figure 2.1 Strain gauges: (a) wire type; (b) foil type…………………………….…....5

Figure 2.2 RFID tag…………………………………………………………………....6

Figure 2.3 RFID arrangement……………………………………………………….....7

Figure 2.4 Control barrier……………………………………………………………...9

Figure 2.5 Arduino motor shield……………………………………………….……..10

Figure 2.6 Arduino motor shield with possible interconnection………………….......10

Figure 2.7 Brush d.c motor…………………………………………………………....11

Figure 2.8 D.C motor connections with a motor shield……………….……………...12

Figure 2.9 Arduino Uno front side………………………………………………........13

Figure 3.0 Block diagram showing the connection of project modules…………..…..15

Figure 3.1 Detailed system diagram .............................................................................16

Figure 3.2 Weight sensing unit ……………………………..………………………..17

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Contents

DECLARATION ....................................................................................................................................................

CERTIFICATION ................................................................................................................................................ ii

DEDICATION ................................................................................................................................................... iii

ACKNOWLEDGEMENT ......................................................................................................................................iv

PROJECT ABSTRACT ......................................................................................................................................... v

LIST OF FIGURES ..............................................................................................................................................vi

CHAPTER ONE: INTRODUCTION …………………………………………………………………………………………………………………………..1

1.0 BACKGROUND ............................................................................................................................................ 1

1.1 PROBLEM STATEMENT ............................................................................................................................... 1

1.2 PROJECT JUSTIFICATION ............................................................................................................................. 2

1.3 PROJECT AIMS AND OBJECTIVES................................................................................................................. 2

1.3.1 GLOBAL OBJECTIVES ............................................................................................................................ 2

1.3.2 SPECIFIC OBJECTIVES ........................................................................................................................... 2

1.4 SCOPE ........................................................................................................................................................ 2

CHAPTER TW0: LITERATURE REVIEW……………………………………………………………………………………………………………………3

2.0 OVERVIEW ................................................................................................................................................. 3

2.1 LOAD MEASUREMENT UNIT ....................................................................................................................... 3

2.1.1 Weighbridge plate ............................................................................................................................... 4

2.1.2 Weight sensors and transducers .......................................................................................................... 4

2.1.3 Display unit ......................................................................................................................................... 5

2.2 VEHICLE IDENTIFICATION SYSTEM .............................................................................................................. 5

2.2.3 Radio Frequency Identification (RFID) .................................................................................................. 6

2.3 DATABASE .................................................................................................................................................. 8

2.4 VEHICLE MOVEMENT CONTROL SYSTEM .................................................................................................... 9

2.4.1 D.C motor .......................................................................................................................................... 11

2.4.2 ARDUINO .......................................................................................................................................... 12

CHAPTER THREE: METHODOLOGY……………………………………………………………………………………………………………………..15

3.0 OVERVIEW ............................................................................................................................................... 15

3.1 FLOW DIAGRAM ....................................................................................................................................... 16

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3.2 TAPPING AN OUTPUT SIGNAL FROM THE WEIGHING UNIT ....................................................................... 19

3.3 DEVELOPMENT OF AN RFID SYSTEM......................................................................................................... 19

3.4 INTERFACING THE ARDUINO MICRO-CONTROLLER WITH SYSTEM COMPONENTS..................................... 20

3.4.1 Interfacing with measured input signal .............................................................................................. 20

3.4.2 Interface with the host computer ...................................................................................................... 20

3.4.3 Interface with the barrier control motors .......................................................................................... 21

3.5 DATABASE DEVELOPMENT ....................................................................................................................... 21

3.6 DISPLAY UNIT ........................................................................................................................................... 22

3.7 ACTUATOR SYSTEM .................................................................................................................................. 22

CHAPTER FOUR: RESULTS AND ANALYSIS………………………………………………………………………………………….………………..23

4.0 OVERVIEW ............................................................................................................................................... 23

4.1 MODULAR PERFORMANCE ....................................................................................................................... 23

4.1.1 RFID reader ....................................................................................................................................... 23

4.1.2 Weight unit ....................................................................................................................................... 23

4.1.3 Barrier motors ................................................................................................................................... 23

4.2 OVERALL SYSTEM OUTPUT ....................................................................................................................... 23

4.3 DISCUSSION AND ANALYSIS ...................................................................................................................... 24

4.3.1 Advantages ....................................................................................................................................... 24

4.3.2 Disadvantages ................................................................................................................................... 25

4.4 CHALLENGES ............................................................................................................................................ 25

CHAPTER FIVE: RECOMMENDATIONS AND CONCLUSION…………………………………………………………………………………..26

5.0 OVERVIEW ............................................................................................................................................... 26

5.1 RECOMMENDATIONS/ FUTURE INPROVEMENTS ...................................................................................... 26

5.2 CONCLUSION ........................................................................................................................................... 27

REFERENCES……………………………………………………………………………………………………………………………………………………….28

APPENDIX…………………………………………………………………………………………………………………………………………………………..29

BUDGET ......................................................................................................................................................... 29

TIME PLAN ..................................................................................................................................................... 30

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CHAPTER ONE: INTRODUCTION

1.0 BACKGROUND

In the past and still today, weighbridge systems have been used to determine the load

capacity of a vehicle and hence providing the road authorities with a means of

implementing the road restrictions rules. In the country, weighbridge stations have been

erected at different locations to help monitor the transporters’ adherence to the load rules.

These stations are generally constituted of: weighbridge unit, where the vehicle load is

taken, computer system to handle the records and an address system to notify the vehicle

driver of any action to be taken. However, the components mentioned above are not

integrated to form a system that can operate effectively without the input of an officer in-

charge or a station attendant. The wide involvement of officer leave the system to be

highly dependent on them and hence result to the services offered being directly

influenced by the station officer, a situation which may lead to biasness, corruption,

dissimilar services or even inefficiency. This project seeks at developing a fully

automatic weighbridge system that will address most of these issues.

1.1 PROBLEM STATEMENT

The growth of automotive industry has resulted to cheaper, affordable and accessible

means of inland transport means. This includes small cargo carriers and large cargo

carriers ranging from vans to heavy commercial vehicles such as trailers. This on the

other hand has demanded improved infrastructure to increase the efficiency of the

transport means, this includes loading and offloading facilities, cargo handling and

packaging equipment and mostly a reliable, all weather smooth road network.

Maintenance of a smooth road network has proved difficult with businesspeople devising

new means of increasing their profits through increased cargo carriage while paying little

or no attention to road maintenance measures being effected and at the same time

demanding for an ever conditioned road. This has since then prompted the roads

maintenance board to develop means of regulating the load size being carried on the

roads. Such means include erecting weigh bridges at specific points on the roads where

the heavy commercial vehicles are required to pass through and their gross weight be

determined and corresponding measures be taken.

However, the process has been marred by corruption with most businesspeople opting to

part with bribe in event of overloading rather than following the set measures such as

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court fines and more information on road maintenance efforts and importance. This has

encouraged intentional overloading, as there is an open loophole for the whole weigh

bridge system, and hence increased rate of road network degradation.

1.2 PROJECT JUSTIFICATION

The current weigh bridge system in Kenya leaves the major part of it being played by

officers; this has left a loophole due to corruption as the officers are easily influenced into

it by the easy source of revenue. Also, the axle rule where each axle is not supposed to

exceed 8 tons as opposed to the whole gross weight has left the transporters an excuse of

being inappropriately charged with some citing shifting of goods from the prearranged

axle-balanced position during transit but not the overall overloading. Some of them thus

tend to justify their actions of bribing the concerned authorities.

This project aims at providing an unmanned weigh bridge system with minimal human

intervention and thus sealing the corruption loophole. It also aims at involving the whole

gross weight calculation rather than the axle-based system.

1.3 PROJECT AIMS AND OBJECTIVES

1.3.1 GLOBAL OBJECTIVES

To develop an automated weigh bridge system

1.3.2 SPECIFIC OBJECTIVES

To design a micro controlled barrier linked to the weigh bridge

To develop a database to handle the transactions involved.

To develop a payment enabling system in event of a fine being required.

1.4 SCOPE

The project aimed at developing a weighbridge system model using available low power

components and developing a database to handle the same.

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CHAPTER TW0: LITERATURE REVIEW

2.0 OVERVIEW

This project in its effort to satisfy the fully automation condition seeks to involve

different sub-systems within it. These include:

Load weighing module

Vehicle identification system

Database on the flow of vehicles

Vehicle movement, through the weigh bridge, control system

These modules are then meant to be integrated in a way that will ensure their effective

and efficient operation as a unit. A brief introduction for each of the modules follows

below.

A simple system diagram is as fig 2.0 below.

Figure 2.0 Simple system diagram

2.1 LOAD MEASUREMENT UNIT

This unit involves all the components that are used to accurately determine the weight of

the load carried on the vehicle. The weight of the load; however, can only be determined

from the gross weight of the vehicle on load. Such components include

weighbridge plate

the underlying mechanisms of weight sensors and transducers

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display unit

2.1.1 Weighbridge plate

This is a large metallic (or any hard material) plate that can withstand and bears the gross

load of the vehicle. The vehicle is driven on its top and well positioned as of the indicated

marks. However, for some weighbridges there exist different plates for each wheel axle

depending on the concerned authorities’ requirement.

2.1.2 Weight sensors and transducers

Attached to the weighbridge plate, there are sensors that are sensitive to any changes in

the weight on the plate. Other weight measurement components may be load cells,

weighing sensors and weigh modules. The sensors can either be weight bars, strain

gauges or coils that outputs a signal corresponding to the exerted force and which can be

transduced to the analyzable form. The use of strain gauge is considered below.

2.1.2.1Strain gauge

Strain gauges are devices that experience a change in resistance when they are stretched

or strained. They are able to detect very small displacements, usually in the range 0–50

μm, and are typically used as part of other transducers, for example diaphragm pressure

sensors that convert pressure changes into small displacements of the diaphragm.

Measurement inaccuracies as low as 0.15% of full-scale reading are achievable and also

have increased life time. Strain gauges are manufactured to various nominal values of

resistance, of which 120Ω, 350 Ω and 1000 Ω are very common. The typical maximum

change of resistance in a 120 Ω device would be 5 Ω at maximum deflection.

The typical type of strain gauge consists of a length of metal resistance wire formed into

a zigzag pattern and mounted onto a flexible backing sheet, as shown in fig 2.1(a), but the

current trend of strain gauges involve a metal foil or semi-conductor type as in fig 2.1(b).

The wire is nominally of circular cross-section. As strain is applied to the gauge, the

shape of the cross-section of the resistance wire distorts, changing the cross-sectional

area. As the resistance of the wire per unit length is inversely proportional to the cross-

sectional area, there is a consequential change in resistance. The input–output

relationship of a strain gauge is expressed by the gauge factor, which is defined as the

change in resistance (R) for a given value of strain (S),

Gauge factor=

5

Figure 2.1 Strain gauges: (a) wire type; (b) foil type.

In use, strain gauges are bonded to the object whose displacement is to be measured. The

process of bonding presents a certain amount of difficulty, particularly for semiconductor

types. The resistance of the gauge is usually measured by a d.c. bridge circuit and the

displacement is inferred from the bridge output measured. The maximum current that can

be allowed to flow in a strain gauge is in the region of 5 to 50 mA depending on the type.

Thus, the maximum voltage that can be applied is limited and consequently, as the

resistance change in a strain gauge is typically small, the bridge output voltage is also

small and amplification has to be carried out.

2.1.3 Display unit

The display unit enables the visual collection of the load weight. It can be analogue or

digital where with analog, a pointer that is deflected according to the weight exerted is

used to indicate the weight on a pre-calibrated scale. This type of display does not

necessarily require the transformation of the mechanical measurement output to an

electrical form. With digital display unit, the mechanical form of the measurement output

is first converted to a digital form which is the fed to the display.

2.2 VEHICLE IDENTIFICATION SYSTEM

This includes the onboard vehicle information unit, the station information detector and

the communication channel between the vehicle and the toll station. Different methods

can be used to facilitate transfer of information stored on the onboard data storage and the

station reader which then directly connected to a computer that hosts the system database.

Such methods include Radio Frequency Identification (RFID), Quick Response (QR)

codes, smart cards based on different principles among others. Each of these methods,

however, has both advantages and disadvantages which need to be highly considered

6

when choosing the method to use. The RFID system is analyzed below and will be

applied in the development of this project.

2.2.3 Radio Frequency Identification (RFID)

This is a communication technique that involves a tag containing the identity of a product

and a separate reader that is able to capture the information stored on the tag through

radio signals. In general the main components of an RFID system are: a transceiver with

an antenna (RFID reader) and a transponder (transmitter/responder) with an antenna

which constitutes an RFID tag and which is electronically programmed with unique

information. The RFID tag is read when the reader emits a radio signal that activates the

transponder, which then sends data back to the transceiver. The purpose of an RFID

system is to enable data to be transmitted by a portable device, tag, which is read by an

RFID reader and processed according to the needs of a particular application.

The transponders can be categorized into two; passive and active transponders. Passive

transponders and tags are those that have no energy source of their own and rely on the

energy given off by the reader for the power to respond. They are relatively cheaper and

transmit over shorter distances.

An active transponder or tag has an internal power source which it uses to generate a

signal in response to a reader. Active transponders are more expensive than passive ones

and can communicate over miles like ordinary radio communications.

2.2.3.1 RFID Tag

A typical RFID tag consists of a microchip attached to a radio antenna mounted on a

substrate. The chip can store as much as 2 kilobytes of data. The physical appearance of

the tag is shown in fig 2.2 below.

Figure 2.2 RFID tag

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2.2.3.2 RFID reader

A typical reader is a device that has one or more antennas that emit radio waves and

receive signals back from the tag. The reader then passes the information in digital form

to a computer system.

2.2.3.3 Operation principle

When a transponder enters a ‘read’ zone, its data is captured by the reader and can then

be transferred through standard interfaces to a host computer, printer, or programmable

logic controller for storage or initiate an action. The arrangement can be as shown below,

Figure 2.3 RFID arrangement

The antenna emits radio signals to activate the tag and to read and write data to it.

The reader emits radio waves in ranges of anywhere from one inch to 100 feet or more,

depending on its power output and the radio frequency used. When an RFID tag passes

through the electromagnetic zone, it detects the reader's activation signal.

The reader decodes the data encoded in the tag's integrated circuit (silicon chip) and the

data is passed to the host computer for processing.

2.2.3.4 Advantages of RFID

Tag detection not requiring human intervention reduces employment costs and

eliminates human errors from data collection,

As no line-of-sight is required, tag placement is less constrained,

RFID tags have a longer read range than other methods such as barcodes,

Tags can have read/write memory capability, while barcodes do not,

An RFID tag can store large amounts of data additionally to a unique identifier,

Unique item identification is easier to implement with RFID than with barcodes,

8

It does allow identification of items individually rather than generically even when

in same place.

Tags are less sensitive to adverse conditions (dust, chemicals, physical damage

etc.),

Many tags can be read simultaneously,

Automatic reading at several places reduces time lags and inaccuracies in an

inventory,

Since there is no contact between the card and the reader, there is less tear and

wear hence lesser maintenance.

2.2.3.5 Disadvantages of RFID

Cost. Though relatively cheap, the cost of the tag will depend on its quality.

Collision. Attempting to read several tags at a time may result in signal collision

and ultimately to data loss.

Security and privacy Issues. The RFID communication must be encrypted to

ensure security as the information can be read by any RFID reader in tag range

without the tag-holder’s consent.

Frequency. Through its operation in the allowed frequency range, RFID signals

may be interfered with by other signals operating in the same frequency thus

reducing its efficiency.

2.3 DATABASE

A database is a collection of data which is logically related and about an entity of interest.

A database system on the other hand is a computer system which operates on a database.

A database management system is a software that is used to manage a database by

allowing users to access, update, delete or insert data into a database and also provides an

interface of interaction between the user and the database. Examples of database

management system include MsAccess, MySQL (Structured Querry Language), Oracle,

SyBase and SQL server. The database management system can be either open source or

proprietary depending on whether the user has to pay for its use or not. For this project an

open source database management system will be used to save on the project cost and

freedom of use. An example is the MySQL. The main reasons of using a database are:

enabling central control, reducing manual normalizing thus redundancy, increase

reliability and security enhancement.

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This project will include a centralized database that stores all the information on the

vehicles through the weighbridge, their load and financial records and an access to a

central database. The database is also set to be easily and automatically updated once a

vehicle is introduced into the weighbridge station.

2.4 VEHICLE MOVEMENT CONTROL SYSTEM

This unit is comprised of two control barriers, fig 2.4, which are micro-controlled

depending on the command triggered. The first barrier is used to block other vehicles

from entering the weighing block in case there is another vehicle being checked and will

only open when the current vehicle has been cleared. The second control barrier is used

to block the vehicles from proceeding further without being cleared. The two barriers are

actuated by different signals from the microcontroller.

The actuators are motors attached to each barrier and which are fed from a separate

power source from that of the microcontroller and also require connection through a

motor shield to enable the microcontroller send the low power signal that is to control the

motors which could be having an external source. Fig 2.5 shows a motor shield which is

compatible with the Arduino Uno, being used in the project, and fig 2.6 shows a possible

connection of a d.c motor and the shield.

Figure 2.4 control barrier

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Figure 2.5 Arduino motor shield

Figure 2.6 Arduino motor shield with possible interconnection

The motor shield specifications are:

2 connections for 5V 'hobby' servos connected to the Arduino's high-resolution

dedicated timer - no jitter!

Up to 4 bi-directional DC motors with individual 8-bit speed selection (so, about

0.5% resolution)

Up to 2 stepper motors (unipolar or bipolar) with single coil, double coil,

interleaved or micro-stepping.

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4 H-Bridges: L293D chipset provides 0.6A per bridge (1.2A peak) with thermal

shutdown protection, 4.5V to 25V

Pull down resistors keep motors disabled during power-up

Big terminal block connectors to easily hook up wires (10-22AWG) and power

Arduino reset button

2-pin terminal block to connect external power, for separate logic/motor supplies

Tested compatible with Mega, Diecimila, Uno & Duemilanove

Direct current (d.c) motors will be used in this project due to their ease of power rating

integration with other components and also the ease of connection.

2.4.1 D.C motor

A DC motor is an electric motor that runs on direct current (DC) electricity. A d.c motor

can either be of brush or brushless design.

2.4.1.1 Brushed d.c motor

The brushed DC electric motor generates torque directly from DC power supplied to the

motor by using internal commutation, stationary magnets (permanent or electromagnets),

and rotating electrical magnets.

The d.c motor torque is produced by the principle of Lorentz force, which states that any

current-carrying conductor placed within an external magnetic field experiences a torque

or force known as Lorentz force. The fig 2.7 below shows the main components of brush

d.c motor including the permanent magnets and brushes. Advantages of a brushed DC

motor include: low initial cost, high reliability, and simple control of motor speed.

Disadvantages include: high maintenance and low life-span for high intensity uses.

Maintenance involves regularly replacing the brushes and springs which carry the electric

current, as well as cleaning or replacing the commutator. These components are

necessary for transferring electrical power from outside the motor to the spinning wire

windings of the rotor inside the motor.

Figure 2.7 brush d.c motor

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2.4.1.2 Brushless d.c motor

Brushless DC motors use a rotating permanent magnet or soft magnetic core in the rotor,

and stationary electrical magnets on the motor housing. A motor controller converts DC

to AC. This design is simpler than that of brushed motors because it eliminates the

complication of transferring power from outside the motor to the spinning rotor.

Advantages of brushless motors include: long life span, little or no maintenance, and high

efficiency. Disadvantages include: high initial cost and more complicated motor speed

controllers.

Figure 2.8 D.C motor connections with a motor shield

The motor shield can drive up to 4 DC motors bi-directionally, that is, they can be driven

forwards and backwards. The speed can also be varied at 0.5% increments using the high-

quality built in pulse width modulation (PWM) hence the speed is very smooth and won't

vary. Connection of the motors to the shield is done by soldering two wires to the motor

terminals and then connecting them to either the M1, M2, M3, or M4 pins on the motor

shield. A typical simple connection is as in the fig 2.8.

2.4.2 ARDUINO

Arduino is an open source physical computing platform based on a simple input/output

(I/O) board and a development environment that implements the Processing language,

that is, Arduino is composed of two major parts: the arduino board, which is the hardware

and the Arduino Integrated Development Environment (IDE) which is the software part.

2.4.2.1 ARDUINO HARDWARE

The Arduino board is a small microcontroller board, which is a small circuit (the board)

that contains a small ATmega168 chip (the microcontroller) and which is the main

13

component of the board. The board can be individually assembled or acquired when pre-

assembled. Different versions of the board such as Arduino Duemilanove, Arduino

Diecimila, Arduino NG exist but the board is mainly constituted of the following:

14 Digital IO pins (pins 0–13)

These can be inputs or outputs, which is specified by the sketch you create in the IDE.

6 Analogue In pins (pins 0–5)

These dedicated analogue input pins take analogue values (i.e., voltage readings from a

sensor) and convert them into a number between 0 and 1023.

6 Analogue Out pins (pins 3, 5, 6, 9, 10, and 11)

These are actually six of the digital pins that can be reprogrammed for analogue output

using the sketch you create in the IDE.

The board can be powered from the computer’s USB port, most USB chargers, or an AC

adapter (9 volts recommended, 2.1mm barrel tip, and center positive). If there is no

power supply plugged into the power socket, the power will come from the USB board,

but as soon as you plug a power supply, the board will automatically use it. The Arduino

Uno below, fig 2.9, show the basic components that will be present in most of the

Arduinos

Figure 2.9 Arduino Uno front side

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2.4.2.2 THE ARDUINO SOFTWARE (IDE)

The Integrated Development Environment is a special program running on a computer

that allows one to write sketches for the Arduino board in a simple languge developed

after the Processing language. The sketch is then uploaded to the board by first

translating it into C language and then passed to the avr-gcc compiler that translates the C

code to a language understood by the microcontroller. The board can then execute the

sketch.

To run the Arduino from the computer, the right drivers must be installed and

communication established between the two by determining the serial port assigned to the

Arduino board.

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CHAPTER THREE: METHODOLOGY

3.0 OVERVIEW

This project implementation, from some of the above described principles and

components, was approached in modules. The design procedures that were carried out

include:

Tapping a signal from the measurement unit output, the load cell.

Developing an RFID system that will enable communication of the vehicle

information with the host computer handling the database.

Interfacing the Arduino microcontroller to the tapped signal and the database host

computer.

Developing a simple database to simulate a large scale database

Displaying the output and to enable efficient communication to the vehicle driver.

Developing an actuator system to control the barriers.

The project system was designed as in the block diagram below. A detailed connection

diagram also follows in Figure 3.1.

Figure 3.0 Block diagram showing the connection of project modules.

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Figure 3.1: Detailed system diagram

Database host

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3.1 FLOW DIAGRAM

The above project design procedures were aimed at developing a system that enabled the

flow of processes as in the flow diagram below:

No

YES

Vehicle positions on

weighbridge and

information on RFID read

Vehicle

overloaded

Database accessed for the

particular vehicle

Vehicle weight taken

Microcontroller actuates

opening of barrier

Vehicle account info

verified and

deductions made for

payment

Prompt the driver to park

off the road and pave way

for other vehicles

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Start

Barrier1

closed

Vehicle in position

Vehicle weight detected and

RFID tag number read

Display vehicle details and

welcome note

Check the weight

read against set

values

Display weight

overload Display

compliance

message

Barrier2

opens

Barrier2

closes

Display overloaded

amount

Access database, the linked

account and deduct fines

Prompt driver to park

off the road

No

Flow chart diagram for the system

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3.2 TAPPING AN OUTPUT SIGNAL FROM THE WEIGHING UNIT

This project employed the SEN-10245 (50Kg) load sensor as the load cell. It required

two load cells to create a full bridge where pressing on the sense cell (load cell 1) gives

an output swing of about 4V. The output from the bridge, very small signal in the range

of 0 to 0.05V, demands to be passed through an instrumentation amplifier to give out a

feasible voltage range of 0 to around 5V. This gives out an output that can be fed to an

arduino as an input.

Figure 3.2 Weight sensing unit

The weight signal is then fed to the analog pin 1 of the Arduino micro-controller for

subsequent operation determination and display purpose. This happens in line with the

program in the micro-controller which dictates the sequences.

3.3 DEVELOPMENT OF AN RFID SYSTEM

This involved the physical design and firmware development of the RFID system. The

physical design will included: interfacing the RFID reader with the host computer that

handles the database, including establishing a permanent safe port to use, determination

of the RFID reading range where the reader will effectively communicate with the RFID

tags, determining the viable powering technique to use and also interfacing the RFID

system to the Arduino micro-controller.

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The software development included: developing the RFID firmware that create a friendly

user interface and also ensure efficient communication with the host computer and

developing the microcontroller software that will enable communication between the two

so as to harmonize the system.

The RFID system was aimed at facilitating the following: once the vehicle is in the

station and thus the reading range of the tag, the RFID reader is expected to communicate

with the tag and read the information stored in it and call the vehicle database file in the

host computer. The microcontroller signal will then trigger the database to update the

vehicle load specifications and if necessary link the bank account for deductions of any

fine payments. The system is then expected to close the transaction and effect any RFID

security measures if any.

3.4 INTERFACING THE ARDUINO MICRO-CONTROLLER WITH SYSTEM COMPONENTS

This included interfacing the micro-controller with the measuring unit signal, interfacing

the micro-controller with the host computer and also its interface with the barrier control

motors. This involved the physical interconnections and also development of code to

enable or drive each of the interfaces made such as the allocated input/output ports and

communication.

3.4.1 Interfacing with measured input signal

The measuring unit, load cell’s, output signal was fed to the microcontroller and served

as the main signal to determine the rest of the processes to be initiated according to

whether the vehicle is relatively overloaded or not. The signal is expected to be in the

analogue form and thus will be inputted through the analogue 1 input pin of the

microcontroller which was programmed to enable the same. The input pin is specified by

the sketch written so to avoid signals from other pins to trigger the subsequent processes.

3.4.2 Interface with the host computer

The Arduino UNO micro-controller, used in this case, has a serial port that facilitates

serial communication with the host computer through a universal serial bus cable. The

port on the host computer that is used for this purpose thus needs to be identified and

assigned to the micro-controller. This process is done by first accessing the available

ports from the host computer and then selecting one of the available ports assigning it to

the Arduino UNO. Any communication from the Arduino is thus sent to that particular

assigned port. The serial buffer linked with the Comm port temporarily store the sent data

awaiting transfer or clearing after being read. This is done through the use of the key

21

word ‘Serial’ in the Arduino program developing either to write or read from the serial

buffer.

The Arduino micro-controller sketch or code was designed to link to and access a

database file stored in the host computer as the micro-controller itself lacks enough

memory to store an operational database. However, for demonstration, a similar database

was created and stored in the micro-controller’s memory.

3.4.3 Interface with the barrier control motors

The main aim of the project is to ensure adherence to load specifications by the road

authorities by filtering the vehicles that tend to defy them. This is done through initiation

of corresponding processes once the vehicle weight have been taken and the micro-

controller having intelligently identified the load specification and the actuation process

to execute. The actuation process might be either to open the road barriers to allow the

vehicle to proceed or to retain the barrier closed, in case of overloading, until the required

transactions are made and then proceed in opening the barrier. The barriers in this case

are controlled using direct current motors which are directed by the Arduino micro-

controller but will require a different source of power as the power from the micro-

controller is not adequate to run the motor. A motor shield is then required to enable the

micro-controller small output current to control the motor which is powered from a

different power source with higher current. This more like a transistor (such as a Bipolar

Junction Transistor) would be used to trigger or switch-on current flow in the motor

circuit by only feeding a small current in its input (such as the base current for a BJT) but

in this case a pre-assembled board, the Arduino motor shield, is used as it allows easier,

faster and efficient connection of more than one motors and other servo components. The

motor shield design was described in the literature review section above. In this project,

the two barrier control motors are used where one is to drive the barrier controlling the

station access and the other to drive the barrier regulating the proceeding of vehicles from

the station, which are connected to motor ports on the shield board and their driving

power connected through the external motor power connection pins. The code or sketch

to enable the motor control was developed and uploaded into the micro-controller. The

code is also meant to identify the output pins to use; analogue or digital.

3.5 DATABASE DEVELOPMENT

The system database designed is meant to perform the following operations:

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Store the registration numbers of the vehicle, the vehicle owner or the transport

company, type or model of the vehicle, its expected load specifications and a liable

linked prepaid account.

Automatically access each vehicle database account at ease or create a new

database account for a new vehicle.

Update the vehicle’s database account as per the activities carried out or

transactions involved.

The database developed is based on MySQL database management system and the

entities include: vehicle registration number, vehicle owner or transport company, model

or type of vehicle, specified vehicle load (gross and total), actual vehicle load as of the

moment, type of load, destination of load, bank account and any transaction involved.

Each of these entities have its associated attributes.

3.6 DISPLAY UNIT

This display is mainly aimed at ensuring the smooth involvement of the vehicle driver in

the weighbridge system processes by displaying the outcome and requirement of each

stage where necessary. This is also very crucial in prompting the driver for any co-

operation required. It also aid in communication especially in a noisy environment such

as heavy commercial vehicles’ engine roar, a situation where the normally used audio

signal is unreliable.

Some of the variables to be displayed include:

Vehicle load weight from the weight measurement unit once converted into digital

form

Request to proceed for vehicle with allowable load

Amount overloaded and the fine to be paid in event of an overloaded vehicle

Request to proceed once the transactions are over

3.6 ACTUATOR SYSTEM

The control barriers used in this case are driven by direct current motor which are

actuated by the signal from the micro-controller. The right power source for the motors

will be any d.c supply or rectified a.c source. The current to drive the motor flows in a

different circuit from the one involving the micro-controller direct connection but its

switch will be triggered by the signal from the microcontroller through a transistor.

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CHAPTER FOUR: RESULTS AND ANALYSIS

4.0 OVERVIEW

This chapter gives the general functioning of the system as a whole and the output or

performance at every module. It gives the functioning of the automated weighbridge

system as observed during its operation. A brief analysis of the results is also included in

the chapter.

4.1 MODULAR PERFORMANCE

4.1.1 RFID reader

The RFID reader used in this case was the ID-20 Innovations that operates at 125 KHz

for EM4001 64-bit RFID tags and an ideal read range of 200mm. The RFID tags used are

passive thus contributing to the small reading range. Practically, the reader could only

detect the tags at a separation of around 3 inches.

4.1.2 Weight unit

The electrical signal from the load cells was very small and thus required amplification

through an instrumentation amplifier which unlike the normal operational amplifiers

could produce a more stable amplified signal. Output raw signal ranges were from 0 to

0.05V while the amplified signal range was 0 to 5V. In this range, the overload threshold

was taken as 3V for the project where values above that were taken as overloads.

4.1.3 Barrier motors

The barriers in this case were controlled by motors and their opening and closing was

represented by the rotation of the motors in clockwise (forward) and anticlockwise

(reverse) directions respectively. Barrier 1 is meant to remain closed as long as the there

is a vehicle in the weigh station but normally open if there is no vehicle. Barrier 2 on the

other hand is supposed to remain closed until a vehicle is allowed to proceed.

4.2 OVERALL SYSTEM OUTPUT

The system as developed is intended to be a standalone and thus once initialized should

continue in operation or in idle state awaiting a signal from the sensors. The weight

sensors and the RFID reader are the main inputs to the microcontroller and whose inputs

pose as the determinant of the subsequent operation of the system. The main output is the

barrier control where the barriers can remain closed or be opened as triggered by the

micro-controller.

The system microcontroller continuously checks for an RFID tag read from the RFID

reader and the weight signal from the bridge, in this case the load cells. The weight signal

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is detected only when a force is applied to the load cells. This also enables the reading of

the RFID tags by the reader positioned close enough. This is followed by the

corresponding micro-controlled action.

The following scenarios are possible and their outputs were observed as follows.

1. Weight detected being less than or equal to the threshold weight allowed: This

scenario was faced by the barrier control motors rotating in the forward direction

thus opening the barrier allowing the vehicle to proceed.

2. Weight detected being more than the allowed weight with a deductible

balance in the account: This scenario is marked by a deduction in the account

value in the vehicle database and also the opening of barrier 2.

3. Weight detected being more than the allowed amount with a deficit account

balance: This scenario is marked by failure to open the barriers and the prompting

of the driver to park off the road, a message displayed on the LCD.

.

4.3 DISCUSSION AND ANALYSIS

The micro-controller which works with electrical signals demanded the conversion of

each input to electrical signal. From the different scenarios considered and different

settings, the output seemed to end in relatively the same results as projected in the design

step. This was however subject to errors and thus the efficiency and the sensitivity

targeted could not be fully achieved. This is especially marked by some delays in

response, weight to electrical signal conversion, varying distance of detecting the RFID

tags and the inadequacy of controlling the motor position.

However, it is notable that with the use of more sensitive modules, though relatively

expensive, more efficiency can be achieved.

It was also noted that the project was mostly comprised of components that exist in the

current weigh bridge systems except for the microcontroller. This shows that efficiency

and effectiveness can be achieved at very minimal extra cost.

4.3.1 Advantages

The automation makes the system advantageous through:

Saving on human capital thus the overall maintenance cost

Improved efficiency as the human error is reduced

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Increased reliability as the system can operate at all times for long hours

Uses only the existing components of a weighbridge with only the addition of a

microcontroller thus the installation costs remain relatively the same for a more

effective system.

Long-term road maintenance cost saving as overloading will be highly controlled

Increased speed of operation thus more vehicles served per unit time.

Cases of harassment by traffic officers to drivers will be highly reduced.

4.3.2 Disadvantages

It is difficult to ascertain the vehicle details as it will only read the tag and which

can easily be switched for a different tag.

It is difficult to ascertain the cargo being transported.

4.4 CHALLENGES

During the project’s implementation, some of the challenges faced included:

Strained availability of some components thus exceeding the scheduled time limit

allocated for their purchase.

Lack of quality components that would fit the allocated budget thus settling for

lesser quality components that at times proved difficult to integrate in the project.

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CHAPTER FIVE: RECOMMENDATIONS AND CONCLUSION

5.0 INTRODUCTION

This chapter outlines some of the recommendations or future improvements that can be

incorporated in the project to add on its effectiveness and efficiency. The project’s

conclusion is also included.

5.1 RECOMMENDATIONS/ FUTURE INPROVEMENTS

The system though developed with the weighing plate capturing the gross vehicle

weight as the input allows also for per-axle weighing units whose different weight

values will be the inputs to the micro-controller and be integrated to determine the

subsequent operations of the weighbridge system. This can also be enhanced by

inclusion of other means of ascertaining the identity of a particular vehicle.

An electronic vehicle registry system for all vehicles can be developed have the

weighbridge system integrated so as to minimize any possible RFID tag switching

by the rogue transporters.

Develop a system that will be able to detect the type of load being transported to

enhance security.

Integrate a receipt printing device for future references by the transporters.

Develop an online database system, centrally located, to ensure updates in the

database. This also will help create accounts for the new vehicles such as those that

rarely visit a given weighbridge station.

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5.2 CONCLUSION

The obtaining of results in this project shows that it is possible to implement an

automated weighbridge system that integrates all the services offered by human

attendants and at the same time increase efficiency, effectiveness and reliability of the

weigh bridges.

From the objectives, it was possible to design a micro-controlled barrier that is linked to a

weigh bridge, develop a database that handles all the transactions and also it was possible

to develop a mode of payment of fines if needed.

The project development thus met all the objectives set and was thus considered

successful.

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REFERENCES

[1]. Internet materials and files on the concerned areas.

Wikipedia

www.practicalarduino.com/projects

www.arduino.cc

www.processing.org

Avon Barrier Company Ltd files

International Journal of Computer and Electrical Engineering, Vol.3, No.1,

February, 2011 1793-8163 (RFID Technology Principles, Advantages,

Limitations & Its Applications)

[2]. Books

GETTING STARTED WITH ARDUINO by Massimo Banzi First Edition

PRACTICAL ARDUINO cool projects for open source hardware BY

Jonathan Oxer Hugh Blemings.

[3]. Class notes and lecture materials

EEE2407 Instrumentation

EEE2411 Microprocessor

ICS 2206 Database

[4] Components’ user guides and manuals

Adafruit motor-shield arduino user guide.

ID series datasheet Mar 01, 2005

Arduino Microcontroller Guide W. Durfee, University of Minnesota

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APPENDIX

BUDGET

Item Component Description Quantity Price(KShs)

Per piece Total

1 RFID reader ID-20 Innovations (125Khz) 1 4 614.00 4 614.00

2 Motor shield Adafruit, Shield for Arduino kit-v1.0 1 2 490.00 2 490.00

3 RFID tags Sparkfun EM4001 (125KHZ) 3 300.00 900.00

4 DC motors 6V dc 2

5 Strip board 14.5 X 6.5 cm (small) 1 50.00 50.00

6 Load cells Sparkfun 50Kg(SEN 10245) 2

8 Arduino UNO UNO R3 1 2 500.00 2 500.00

9 LCD 16 X 2 1

10 USB cable 10” Standard A-B 1

11 Amplifier Instrumentation 1

12 Internet 1 500.00

13 Printing 1 000.00

TOTAL 13 054.00

The excess budget finances, above the institution provision, were mostly from personal

sources. Also some of the components were borrowed.

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TIME PLAN

SEMESTER 1 SEMESTER 2

Activity May June July August September October November December

Research and

literature

review

Project

proposal

Mini-report

compilation

and

presentation

Circuit

development

Purchase of

components

Software

development

System

testing

Y

S

Final report

compilation

&

presentation