dalam buah-buahan, suatu alat dihasilkan dengan tujuan digunakan untuk
menguji ... frekuensi dengan kepekatan jus buah-buahan menunjukkan frekuensi
...
i
THE DEVELOPMENT OF PORTABLE SENSOR TO DETERMINE THE FRESHNESS AND QUALITY OF FRUITS USING CAPACITIVE TECHNIQUE
LAI KAI LING
A report submitted in partial fulfillment of the requirements for the award of the degree of Bachelor of Science and Education (Physic)
Faculty of Education Universiti Teknologi Malaysia
March 2006
iii
Dedicated to my beloved parent
iv
ACKNOWLEDGEMENT
I would like to express my deepest gratitude to my supervisor, Dr. Johari Bin Adnan who has provided me with numerous suggestions and advices to complete this project. His encouragement and support will always be remembered and ppreciated.
I would like to thank the Advanced Electronic Lab assistants who helped me a lot in solving technical problems throughout my research period.
Finally, I would like to thank my parent, my friends for their moral support.
v
ABSTRAK
Pengujian kualiti sesuatu bahan adalah amat penting seperti dalam memilih buah-buahan. Dengan pengetahuan asas terhadap pemalar ketelusan yang terdapat dalam buah-buahan, suatu alat dihasilkan dengan tujuan digunakan untuk menguji kualiti buah-buahan. Hal ini demikian akan membawa kebaikan kepada penghasil, pemproses dan pengguna. Objektif tesis ini adalah menghasilkan satu penderia mudah alih untuk mengesan kesegaran dan kualiti buah-buahan berdasarkan teknik kapasitif. Kandungan cecair yang berbeza akan menyebabkan kapasitif antara dua penduga berubah apabila ia dicelup ke dalamnya. Jus buah-buahan diuji dalam berbeza kepekatan iaitu dari jus sepenuhnya ke jus yang telah ditawarkan. Penderia dalam projek ini terdiri dripada 555 timer dan kapasitor digantikan dengan dua penduga. Buah-buahan yang digunakan adalah oren, lemon, tembikai dan tomato. Daripada hasil kajian, penderia boleh berfungsi dengan baik. Bentuk graf hubungan antara frekuensi dengan kepekatan jus buah-buahan menunjukkan frekuensi meningkat apabila kepekatan jus meningkat. Buah-buahan yng segar mempunyai frekuensi yang lebih rendah daripada buah-buahan yang busuk. Ini membawa erti, pemalar ketelusan adalah berbeza antara buah-buahan segar dan buah-buahan busuk.
vi
ABSTRACT
There is a need for determination of product quality in the handling of fresh fruits. With the basic information of the dielectric constant of fresh fruit is presented, it may be able to develop a useful tool of sensing quality factors in fruits that will be benefits to producers, processors and consumers. The objective of this study is to develope a portable sensor to determine the freshness and quality of fruits using capacitive technique. Different liquid will cause the capacitance between the two insulated probes to change, so, the dielectric constant can be measured. Fruits juice was measured in different concentration. This suggests that content in fruits juice can be correlated to dielectric properties. The juices changed from pure juice to tasteless. In this project, the sensor is develope using a timer 555. The capacitor in the original timer 555 astable circuit was replaced by two insulated probe. The fruits used in this project are orange, lemon, watermelon and tomato. The data showed that the portable sensor can function well. Graph of relation between frequency and concentration of fruit juice showed that frequency increase when concentration increase. Fresh fruits have a lower frequency than spoiled fruits. This means dielectric constant is different between fresh fruits and spoiled fruits.
vii
CONTENTS
CHAPTER
TOPIC
PAGE NO.
STATUS DECLARATION FORM SUPERVISOR’S DECLARATION
CHAPTER I
CHAPTER II
TITLE
i
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRAK
v
ABSTRACT
vi
CONTENTS
vii
LIST OF FIGURES
ix
LIST OF SYMBOLS
x
APPENDIX LIST
xi
INTRODUCTION 1.1 Background
1
1.2 Objective
3
1.3 Scope
3
THEORY 2.1 Capacitance
4
2.2 Dielectric Constant
5
2.3 Timer 555
7
viii
CHAPTER III METHODOLOGY 3.1 The Electronic Circuit
12
3.2 Circuit Operation
15
3.3 Sample Preparation
16
3.4 Measurement Procedure
17
CHAPTER IV CALIBRATION AND RESULT
CHAPTER V
4.1 Calibration
19
4.2 Result
20
DISCUSSIONS AND CONCLUSIONS 5.1 Discussions
26
5.2 Conclusions
30
REFERENCES
31
APPENDIX A
33
APPENDIX B
35
APPENDIX C
37
ix
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
2.1
LM 555 Timer Pin Connection
7
2.2
Timer 555 stable circuit
8
2.3
Astable circuit output waveform
8
2.4
LM 555 astable output, a square wave
9
3.1
Oscillator circuit
12
3.2
Seven segment display LCD
13
3.3
Oscillator circuit of portable circuit
14
3.4
Diagram of function of each component in
15
circuit operation 3.5
Picture of apparatus set up
18
4.1
Example of function display equation on chart
21
4.2
Graph showing frequency versus water depth
22
(water) 4.3
Graph showing frequency versus water depth
22
(Orange Juice) 4.4
Graph of frequency versus concentration of fruit
24
juice (Orange) 4.5
Graph of frequency versus concentration of fruit
24
juice (Lemon) 4.6
Graph of frequency versus days
25
x
LIST OF SYMBOLS
Q
-
Charge in coulombs
C
-
Voltage in volts
V
-
Capacitance in Farads
εr
-
Relative dielectric constant
εs
-
Permittivity of material
εo
-
Permittivity of free space
k
-
Constant
A
-
Area
d
-
Distance between two plates
Vcc
-
Voltage
T
-
Period
Tm
-
Mark time (output high)
Ts
-
Space time (output low)
R1 and R2
-
Resistors
f
-
Frequency in Hertz
xi
APPENDIX LIST
APPENDIX
TITLE
PAGE
A
Definition of Pin Functions for Timer 555
33
B
Figure of blender and filter used to prepared
35
fruit juice Figure of Fresh fruit and spoiled fruit (orange
35
and lemon) Figure of fresh fruits cover with food wrap
36
(orange, lemon, watermelon and tomato) Figure of microprocessor and display unit
36
circuit C
Table of data from experiment Frequency
37
versus Water Depth (water) Table of data from experiment Frequency versus Water Depth (orange juice)
37
CHAPTER I
INTRODUCTION
1.1
Background
Material investigations and moisture measurements using electromagnetic waves in wide spectrum serve for quality control and improvement in many branches. For example, industry, civil engineering, agricultural, commerce but also for foodstuffs, for instance for quality detection of meal, fruits, coffee and so on. The research in moist materials and development of measuring devices are absolutely necessary (Klaus Kupter. ed., 2001).
There are many methods used for permittivity determination at microwave frequencies. The methods include reflection measurements with short-circuited wave guides or coaxial lines containing the test samples, resonant cavity parameter measurement when loaded with a sample of the material.
Besides, transmission coefficient
measurement for a large sample of material placed between two radiating elements in free space also can use to measure permittivity (Z. HLAVÁČOVÁ, 2003).
2
However, capacitive sensor systems are very suited to be applied to measure physical quantities, such as position, speed end acceleration of moving objects, liquid levels, dielectric properties and flow of materials.
Dielectrics are usually insulators. Some liquids and gases can serve as good dielectric materials. The dielectric constant is a measure of the extent to which substance concentrates the electrical lines of flux. The dielectric constant tells how a material, living or not, stores energy. The dielectric loss factors indicate the ability of a material to absorb energy from an electric field and convert it to heat. As it turns out, there is a correlation between these dielectric properties and the maturity of fresh produce (Lee, Jill, 1998).
Dielectric constants of materials vary with both the frequency and the temperature of materials. There is a need for determination of product quality in the handling of fresh fruits. With the basic information of the dielectric constant of fresh fruits is presented, it may be able to develop a useful tool of sensing quality factors in fruits that will be bring benefits to producers, processors and consumers.
3
1.2
Objective
The objective of this study is to develope a portable sensor to determine the freshness and quality of fruits using capacitive technique. This sensor is used to determine the fruits in good condition or otherwise based on dielectric property of the fruits.
1.3
Scope
In this project, the sensor is developed using a timer 555. The capacitor in the timer 555 astable circuit was replaced by two insulated probe. Different liquid will cause the capacitance between the two insulated probes to change, so, the dielectric constant can be measured.
A fruit’s characteristic can be determined from the
frequency value when two probes were immersed into it. The fruits used in this project are oranges, lemons, watermelons and tomatoes.
