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: 4 TH 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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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.
i
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
ii
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.
iii
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.
iv
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.
v
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.
vi
LIST OF FIGURES
Figure 2.0 Simple system diagram ……..……….…………………………………….3
CERTIFICATION ................................................................................................................................................ ii
DEDICATION ................................................................................................................................................... iii
PROJECT ABSTRACT ......................................................................................................................................... v
LIST OF FIGURES ..............................................................................................................................................vi
1.1 PROBLEM STATEMENT ............................................................................................................................... 1
1.3 PROJECT AIMS AND OBJECTIVES................................................................................................................. 2
1.3.1 GLOBAL OBJECTIVES ............................................................................................................................ 2
1.3.2 SPECIFIC OBJECTIVES ........................................................................................................................... 2
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
2.4 VEHICLE MOVEMENT CONTROL SYSTEM .................................................................................................... 9
2.4.1 D.C motor .......................................................................................................................................... 11
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
4.1.1 RFID reader ....................................................................................................................................... 23
4.1.2 Weight unit ....................................................................................................................................... 23
TIME PLAN ..................................................................................................................................................... 30
1
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
2
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.
3
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
4
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),