DEVELOPMENT AND CHARACTERIZED OF MICROCONTROLLER BASED
XENON FLASHLAMP DRIVER CIRCUIT
ASMAWATI @ FATIN NAJIHAH ALIAS
A thesis submitted in fulfilment of the
requirements for the award of the degree of
Master of Science (Physics)
Faculty of Science
Universiti Teknologi Malaysia
DECEMBER 2005
ii
I declare that this thesis entitled “Development and Characterized of Microcontroller
Based Xenon Flashlamp Driver” is the result of my own research except as cited in the
references. The thesis has not been accepted for any degree and is not concurrently
submitted in candidature of any other degree.
Signature
:……….…………
Author’s name
: ASMAWATI @ FATIN NAJIHAH BINTI
ALIAS
Date
:………3/12/2005…………
iii
Dedication to my beloved father, mother, family, abang and friends…
Thanks for everything
iv
ACKNOWLEDGEMENT
First of all, in humble way I wish to give all the Praise to Allah, the Almighty
God for His mercy has given me the strength, keredhaanNya and time to complete this
work. With His blessing may this work be beneficial for the whole of humanity
I would like to express my sincere gratitude and appreciation to my supervisors,
Associate Professor Dr. Noriah Bidin and Dr Johari Adnan for their supervision, ideas,
guidance and enjoyable discussion throughout this study. I am also grateful to Dr
Yaacob Mat Daud and Associate Professor Dr Ahmad Radzi Mat Isa for their valuable
advices, opinion and suggestions. I hope all this valuable time and experience will keep
in continue.
I would like to acknowledge the help and kind assistance of the following
persons; En. Nyan Abu Bakar for assisting in carrying out the experimental works; En.
Ahmad Hadi Ali and En.Fairuz Jani for their co-operation and assistance.
Thanks also to all my friends and colleagues for their views, concerns and
encouragement. Last, but not least, I am grateful to my beloved family for their prayers
continuing support, patience, valuable advices and ideas throughout the duration of this
study.
I would also like to take this opportunity to thank the Government of Malaysia
through IRPA scholarship and Universiti Teknologi Malaysia for granting this project
through vote, 74531. Without this financial support, this project would not be possible.
v
ABSTRACT
Optical pumping using flashlamp is the preferred technique in solid state laser.
Xenon flashlamp is a device that emits large amount of spectral energy in short duration
pulses. Xenon is generally chosen because it yields a higher radiation output (40% 60%) for a given electrical energy than other noble gases. Triggering a flashlamp
generally requires very high voltage pulse of a short duration. The objective of this
project is to develop a programmable xenon flashlamp driver. Current set-up allows
flashlamp to be triggered in a single mode. A fundamental study was carried out by
varying the input energy from 4.48 J to 26.88 J across the flashlamp. The heart of the
flashlamp driver is a PIC16F84A microcontroller that runs on a +5 V supply and
clocked by a 4 MHz resonator. This microcontroller was connected to a personal
computer, via serial port, acting as remote terminal. Initially, a TTL pulse output from
PIC16F84A was sent out to drive a SCR. The SCR step-upped the TTL pulse to 332 ±5
volts pulse. Finally, a 1:2 transformer mixes the resulting 740 ±10 volt pulse with 2
±0.01 kV DC voltage. The resulting voltage waveform is applied across a xenon
flashlamp. Xenon gas ionizes for a brief period determined by the pulse width. This
results in an electrical short circuit across the flashlamp’s electrodes. A large amount of
current is drawn across the electrodes. This causes a rapid increase in the current flow
through the flashlamp and initiates the desired arc lamp discharges. A Rogowski coil
was used to detect the pulse current waveform. Xenon flashlamp output was detected
using IPL10050 photodiode. An OPHIR BeamStar CCD Laser Beam Profiler was
employed to record a plasma spectral gradient. The peak pulse current was obtained in
the range of 776 A – 982 A. The bandwidth and the amplitude of the xenon flashlamp
pulse were found in good agreement with the input energy. The beam profiles and
dimensions of the plasma were dependent upon input energy.
vi
ABSTRAK
Pengepaman optik menggunakan lampu kilat merupakan teknik yang dipilih
dalam laser pepejal. Lampu kilat xenon merupakan peranti yang menghasilkan
spektrum tenaga yang banyak dalam tempoh denyut yang singkat. Xenon umumnya
dipilih kerana ia memancarkan pancaran yang tinggi (40%-60%) bagi tenaga elektrik
tertentu yang dibekalkan berbanding gas nadir yang lain. Memicu lampu kilat umumnya
memerlukan denyut voltan yang sangat tinggi pada tempoh yang singkat. Objektif
projek ini ialah untuk membangunkan sebuah pemacu lampu kilat xenon yang boleh
diprogramkan. Susunan sekarang adalah membenarkan lampu kilat dipicu dalam satu
mod. Kajian fundamental dijalankan dengan mengubah tenaga masukan daripada 4.42 J
hingga 26.88 J merentasi lampu kilat. Nadi pemacu lampu kilat ini ialah pengawal
mikro PIC16F84A yang dijana bekalan +5 V dan penyalun 4 MHz sebagai jam.
Pengawalmikro disambung kepada computer peribadi, melalui labuhan sesiri, bertindak
sebagai terminal pengawal. Pada mulanya, output denyut TTL daripada PIC16F84A
dihantar keluar untuk memacu SCR. SCR meningkatkan denyut TTL kepada 332 ±5
volt denyut. Akhirnya transformer 1:2 mencampurkan denyut 740 ±10 volt yang terhasil
dengan voltan 2 ±0.01 kV DC. Bentuk gelombang voltan yang terhasil dibekalkan
merentasi lampu kilat xenon. Gas xenon mengion dalam tempoh tertentu yang
ditentukan oleh lebar denyut. Ini menyebabkan litar pintas merentasi elektrod lampu
kilat. Jumlah arus yang besar terhasil merentasi elektrod. Ini menyebabkan
pertambahan yang pantas dalam aliran arus melalui lampu kilat dan memulakan nyahcas
lampu yang diperlukan. Gelung Rogowski digunakan untuk mengesan bentuk denyut
gelombang arus. Output lampu kilat xenon dikesan menggunakan photodiode
IPLIPL10050. OPHIR Beam Star CCD Laser Beam Profiler digunakan untuk merekod
kecerunam spektrum plasma. Denyut arus puncak diperolehi dalam julat 776 A – 982
A. Lebar jalur dan amplitud yang terhasil didapati mempunyai persetujuan yang baik
dengan tenaga masukan. Profil dan dimensi plasma juga didapati bergantung kepada
tenaga input.
vii
TABLE OF CONTENTS
CHAPTER
1
2
TITLE
PAGE
DECLARATION
ii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
LIST OF CONTENTS
vii
LIST OF TABLES
xi
LIST OF FIGURES
xii
LIST OF SYMBOLS
xvi
LIST OF APPENDICIES
xvii
INTRODUCTION
1.1 Overview
1
1.2 Flashlamp Driver Circuit
3
1.3 Comparison of Rare-Gas Flashlamp
5
1.4 Problem Statement
6
1.5 Research Objective
6
1.6 Research Scope
6
1.7 Thesis Outline
7
LITERATURE REVIEW
2.1 Introduction
9
2.2 Optical Pumping
9
2.3 Flashlamp
10
viii
3
2.3.1
Electrodes and Nobles Gases
11
2.3.2
Spectrum of Xenon Flashlamp
12
2.3.3
Flashlamp Impedance
13
2.4 Power Supplies For Flashlamp
14
2.5 Charging Unit
15
2.6 Trigger Circuit
16
2.6.1
External Triggering
16
2.6.2
Series Injection Triggering
17
2.6.3
Simmer Mode Triggering
18
2.6.4
Pseudo Simmer Mode Triggering
20
2.6.5
Overvoltage Triggering
21
2.7 The Mechanism of Breakdown
21
2.8 Summary
23
METHODOLOGY AND MATERIAL
3.1
Introduction
24
3.2
Xenon Flashlamp
24
3.3
Capacitor Bank
25
3.4
High Voltage Power Supply Calibration
27
3.5
PIC Programming
28
3.6
Flashlamp Driver
30
3.7
Current Measurement
31
3.8
Photodetector
33
3.9
Attenuator
33
3.10 Image Processing System
34
3.10.1 Image Processing
35
3.11 Diagnose the Flashlamp Output
37
3.12 Summary
38
ix
4
CALIBRATION OF HIGH VOLTAGE POWER
SUPPLY
5
4.1
Introduction
39
4.2
High Voltage Power Supply
39
4.3
Power Supply Calibration
42
4.4
Summary
45
DEVELOPMENT OF PULSE GENERATOR
5.1
Introduction
46
5.2
Power supply for Microcontroller
46
5.3
Pulse Generator
48
5.3.1
PIC16F84A
49
5.3.2
MAXIM233
50
5.3.3
Pulse Generator Circuit
51
5.4
6
7
Summary
55
DEVELOPMENT OF FLASHLAMP DRIVER
6.1
Introduction
56
6.2
PSpice Simulation
57
6.3
Flashlamp Driver
58
6.4
Electrical Characteristic
64
6.4
Summary
68
DIAGNOSING THE FLASHLAMP OUTPUT
7.1
Introduction
69
7.2
Flashlamp Intensity Profile and Light Distribution
70
7.3
Flashlamp Waveform
76
x
7.4
8
Summary
82
CONCLUSIONS AND SUGGESTION
8.1
Conclusions
84
8.2
Problems And Suggestions
86
REFERENCES
APPENDICES A – B
PUBLICATIONS
88
93 - 95
100
xi
LIST OF TABLE
TABLE NO.
TITLE
PAGE
4.1
Voltage profile for increasing current
43
4.2
Voltage Profile for decreasing current
43
6.1
Peak current during discharged time due to the input
65
energy
6.2
Peak power during discharged time upon the input
67
energy
7.1
Flashlamp output spot perimeter and area at different
75
input energy
7.2
Pulse duration of xenon flashlamp output at various
79
input energies
7.3
Amplitude of xenon flashlamp output signal at various
input energy
81
xii
LIST OF FIGURE
FIGURE NO.
2.1
2.2
TITLE
PAGE
Flashlamp Types.
(a) Linear Flashlamp,
10
(b) Helical Flashlamp, side and end views,
10
(c) U-Shaped Flashlamp
10
Spectral emission from xenon flashlamp at low
13
electrical loading
2.3
Spectral emission from xenon flashlamp at high
13
electrical loading
2.4
Basic diagram of power supplies for flashlamp
15
2.5
External triggering circuit
17
2.6
Series injection triggering
18
2.7
Basic circuit for simmer mode operation
19
2.8
Pseudo-simmer mode circuit
20
2.9
Overvoltage triggering circuit
21
3.1
U-Shape xenon flashlamp
25
3.2
Photograph of a capacitor
25
3.3
Schematic circuit of capacitor bank
26
3.4
Photograph of Textronix P6015 high voltage probe
27
compensating
3.5
Schematic diagram of calibration work
27
3.6
The process of programming a microcontroller
28
3.7
A Schematic diagram of Yappa programmer hardware
30
3.8
Block diagram of programmable flashlamp circuit
31
xiii
3.9
Current measurement
32
3.10
Rogowski coil as a current transformer
32
3.11
IPL10050 Photodetector circuit
33
3.12
Photograph of filters used in this research.
(a) Melles Griot 03 FIV 038 filter
34
(b) Newport FSQD200 filter
34
3.13
CCD profiler option window
35
3.14
Calibration screen option for Video Test 5.0 software
36
3.15
Block diagram of experiment arrangement
37
4.1
Front panel of high voltage power supply
40
4.2
High voltage power supply schematic diagram
41
4.3
Flowchart of calibration work
42
4.4
Graph of voltage (kV) versus current (µA), with capacitor
44
4.5
Straight line signal is obtained as a result of filtering by
45
storage capacitor
5.1
Schematic diagram for +5 V power supply
47
5.2
Oscillogram of +5 V supply and +16 V input voltage for
48
the LM7805
5.3
Pin Diagram of PIC16F84A
49
5.4
Internal block Diagram of PIC16F84A
49
5.5
Typical operating circuit for MAXIM233
50
5.6
Schematic diagram of pulse generator circuit
52
5.7
ttyS1 port setting
53
5.8
Programmable pulse generator menu (Linux Shell
54
scripting)
5.9
1 µs pulsewidth (single pulse)
55
6.1
Schematic diagram of RLC simulation circuit
57
6.2
RLC simulation waveform
58
6.3
Block diagram of flashlamp driver circuit for a real time
59
discharge Schematic circuit of flashlamp driver
6.4
Schematic circuit of flashlamp driver
60
xiv
6.5
A TTL pulse output from PIC16F84A and SCR gate turn –
61
on signal
6.6
Voltage Waveform.
(a) At primary winding of the series injection transformer
62
(pointA)
(b) At secondary winding of the series injection
62
transformer (point B)
6.7
(c) Waveform describes the action of turn-off the SCR
62
Voltage temporal profile across the 0.1 Ω. The charging
64
voltage and energy were 2 kV and 13.44 J
6.8
Relative peak current of the flashlamp versus capacitor
65
charging energy
6.9
A current waveform of flashlamp at input energy of 13.44
66
J
6.10
Relative peak power as a function of input energy
67
7.1
Block digram of Beamstar reducer
70
7.2
Arc intensity profile of the flashlamp
(a) Three-dimensional image shows the distribution of
72
Gaussian beam profile
(b) Two-dimensional image represents in both horizontal
72
vertical axes
7.3
Gaussian profile of xenon flashlamp output
73
7.4
Two-dimensional images of xenon flashlamp taken at
74
different input energies
7.5
The flashlamp output spot area versus input energy taking
76
at working distance of 80 cm
7.6
Pulse xenon flashlamp output curve with input energy of
77
4.48 J
7.7
Pulse xenon flashlamp output curve with input energy of
78
4.48 J after filtering by the FSQ-OD2.00 filter
7.8
Output Curve of the xenon flashlamp after filtering by
78
xv
FSQ OD200 neutral density filter and 03 FIV 038
interference filter
7.9
Pulse duration profile due to input energy across the
80
flashlamp
7.10
Amplitude versus input energy during discharge
81
xvi
LIST OF SYMBOL
v-i
-
Voltage-current relationship
V
-
Voltage
K0
-
Flashlamp impedance
l
-
Arc length
p
-
Pressure
D
-
Flashlamp bore diameter
AC
-
Alternating current
DC
-
Direct current
C
-
Capacitance
SCR
-
Silicon Controlled Rectifier
CT
-
Total capacitance
PIC
-
Programmable Interface Controller
PIV
-
Peak Inverse Current
I
-
Current
R
-
Resistor
OD
-
Optical density
T
-
Transmission
H
Horizontal of the centroid of plasma
V
Vertical of the centroid of plasma
i(h,v)
Intensity at location (h,v)
I
Total intensity taken the total area
Q
Amount of charge stored in capacitor
P
Power
E
Energy
xvii
LIST OF APPENDICIES
APPENDIX
TITLE
PAGE
A
List of home site used to install YAPPA programming
93
B
Technical specification of IPL10050 photodiode
94
C
Assembly language program for programmable
95
flashlamp driver
CHAPTER 1
INTRODUCTION
1.1
Overview
There are many methods used in pumping process. Basically, for gas laser or
semiconductor laser it used electrical injection as pumping method. Most solid state
lasers are pumped with optical sources (Noriah, 2002). The goal in designing optical
pumps for solid state laser is to match the output spectrum of the optical pump with that
of laser pump bands. Optical pump sources can be divided into two broad categories.
One category is black and greybody radiators, of which filament lamps are the best
example. The other category is pump sources with line emission spectra, of which
semiconductor lasers are the best example (Kuhn, 1998). Noble gas discharge lamps
are compromised between blackbody radiators and line sources. They have significant
blackbody component generated by recombination radiation from gas ions capturing
electrons into bound states (free-bound) and from Bremstahlung radiation. Noble gas
discharge lamps are typically designed so that the plasma completely fills the lamp.
Flashlamp excitation is an attractive method to initiate laser of lasing media
(Winstanley, 1997). The first demonstration of laser action by Maiman was achieved in
1960 by using ruby laser, a crystalline solid system where flashlamp was used as
2
pumping source (Hecht, 1991). The flashlamp-pumped solid-state laser is now by far
the most common pulsed laser system in the world with neodymium ions either in
crystal or in glass as the preferred lasing medium (Shaw, 1997).
Pulsed flashlamps, particularly xenon filled flashlamps are used in variety of
application. Besides used as pumping sources in laser application, there are many
others application of flashlamp. These include light source for flash photography
(Elloumi et al, 2004), copying, optical detection and optical ranging applications, in
cosmetology, dermatology and other medical applications (Inochkin et al, 2004).
Ultraviolet light (UV) emitted by medium and high power flashlamp has been
very useful tool for drinking-water treatment. Intense peak power associated with
microsecond pulses of ultraviolet light generated by inert gas (xenon, krypton)
flashlamps appears effective tool, against a broad range of pathogens, including
Crytosporidium and Giardia (Ganesh et al, 2003).
For the past few years, revolutionary new techniques in medical and aesthetic
applications have been developed and they are taking the industry by storm. These
techniques referred to as Intense Pulsed Light (IPLTM*), Variable Pulsed Light (VPL),
Controlled Pulsed Light (CPL), or Intense Flash Light (IFL) are essentially the same.
The systems harness the energy from a pulsed flashlamp and deliver it directly to the
skin. Thousands of systems are currently operating in Japan and Europe, and the
Federal Drug Administration (FDA) has cleared them for use in the USA. This
technique is providing highly effective in several treatment area (Attwood and
Mehlmann, 2004). These include hair removal, skin rejuvenation, medical skin
treatment and acne treatment.
3
1.2
Flashlamp Driver Circuit
Studies of triggering flashlamp as pumping sources have been investigated by
many previous researchers. Thus, various methods and patterns of xenon flashlamp
drivers have been designed.
Several generations of discharge circuit exists for driving flashlamp. The
original discharge circuits used an in-line trigger transformer or a trigger coil on the
lamp to initiate conduction. A series capacitor-inductor discharge would then occur to
deliver the energy into the lamp. This circuits whilst very simple. Furthermore, has
relatively high jitter between trigger and laser pulse and also reduces lamp lifetime.
However, it is still used today for limited low repetition rate applications.
In order to improve the driver, the second generation of discharge circuits use an
active simmer supply, which triggers lamp into conduction and keeps the lamp in
conduction with a few hundred milli-ampere current flows through it. A
semiconductor-switching device, such as a thyristor, can then be used to control the
discharge into the lamp. This enables repetitive pulsed operation of the lamp. Jitter and
lifetime are much improved and the circuit works well for most application.
The latest and third generation for discharge technologies is the use of an
opening and closing switch, such as an IGBT in combination with a large capacitor
bank. The energy storage must be greater than that to be delivered into the lamp. This
gives a highly flexible technology, where both the pulse energy and pulse length can be
controlled independently. Repetition rates of many kilohertz are possible and many
different applications can be tackled by the same circuit implementation (Greenwood
and Miler, 1999 )
4
Study of the designing single mesh circuit for driving xenon flashlamp was
presented by Markiewicz and Emmet (1966). This single mesh circuit has been found
accurate and useful. Pettifer et al (1975) reported a reliable 60 kV flashlamp triggering
system. The triggering system has proved to be an efficient and reliable unit for
simultaneously triggering a pair of heavy walled, water cooled quartz flashlamp.
Recently, in 1998 a zero-current switching resonant converter as a power supply of a
pulsed Nd:YAG laser was adopted to control the laser power density. This power
supply was designed and fabricated suitable for the high frequency range and to reduce
switching loss and noises (Kim et al, 1998). A new method of sequential charge and
discharge circuit (SCADC) was proposed by Hong et al (1999). The power supply is
composed of low frequency capacitors instead of very expensive high frequency
capacitors. This method have been designed and fabricated based on a cheap and
simple power supply.
Kim et al (2001) have proposed a new power supply for pulsed Nd:YAG laser
adopting zero crossing control (ZCC) method which is simple and compact in design.
In this power supply, SCR was turned on at zero point of input AC voltage by the
method of zero crossing control (ZCC). In 2002, a new real time multi-discharge
method (RTMD) was reported. This method uses real-time one-chip microcomputer
that can turn on the flashlamp with a precision of up to 1µs and thus can create diverse
pulse shapes and strength, in addition to longer pulse (Hong et al, 2002).
A flashlamp driver for medical laser system was reported by McCarthy et al
(2003). This driver circuit was employed IGBT device for power switching and use
microprocessor in order to control laser pulse width. In 2004, Inochikin et al reported a
power supply or driver circuit for a pulsed flashlamp. A high-speed semiconductor
switch was employed in order to turn on and off of the flashlamp by a suitable control.
DC simmer current source was connected across flashlamp to maintain discharge in the
flashlamp.
5
1.3
Comparison of Rare-Gas Flashlamp
Rare gas is also known as noble gas. This noble gas is in Group 8A in the
periodic list table. They include neon, argon, krypton, xenon and radon (David, 1982).
It was found that in the past few years there has been increased interest in rare gas
flashlamp, particularly with respect to their application in solid-state laser pumping and
in high intensity illumination for photographic work. Substantially programs by a
number of people have been carried out to investigate the characteristics of flashlamp.
Oliver and Barnes (1969) presented data on the spectral emission characteristics
of xenon, krypton, argon and neon in the region where the emission line spectra make
up a substantial portion of energy. From the spectra data in terms of both output power
and emitted quanta, it was show that xenon is the most efficient of all the rare gases, a
fact which has been reported previously by Barnes (1964).
Study of rare gas pumping efficiencies for Neodymium laser was reported in
1969 by Oliver and Barnes. The investigation was presented on the comparative
pumping efficiencies of xenon, argon and krypton flashlamp. The results obtained
confirm that krypton can be more efficient than xenon for driving Neodymium laser
when run at low current density. Nevertheless, at high drive levels, xenon is superior to
all the rare gases.
Fountain et al (1970) presented a study of comparison of Kripton and Xenon
flashlamp for Nd:YAG laser. As demostrated previously by Oliver and Barnes (1969),
Kripton lamp was found generally superior to xenon for pumping Nd:YAG laser except
at high current densities.
6
1.4
Problem Statement
A flashlamp driver is the most important part in a solid state laser system. It
used as a pump source for laser material. This study is the initial stage to develop a
flashlamp driver circuit for optical pumping. Hence, this driver can or will be used as
references to develop a driver circuit that can be used as pump source in future.
1.5
Objective
The main objective of this study is to develop a xenon flashlamp driver using
PIC16F84A microcontroller and characterize the xenon flashlamp output. The use of
PIC16F84A microcontroller is as a control element.
1.6
Scope
In this study, a programmable flashlamp driver circuit was developed.
Programmability is provided by a PIC16F84 microcontroller. The flashlamp driver
used a series injection trigger mode as triggering circuit. The current setup allows the
flashlamp to operate in single shot. A Rogowski coil was used to detect the pulse
current waveform. Xenon flashlight output is then recorded using CCD laser beam
profile and analyzed by using imaging software. A photodiode was employed to detect
the output of the flash light.
7
1.7
Thesis Outline
This thesis is divided into eight chapters. In the first chapter, it reviews some of
previous research on the development of flashlamp driver, and the application of the
xenon flashlamp in various field of research.
Chapter 2 reviews the characteristics of the xenon flashlamp including the lamp
design, optical and electrical characteristics of the lamp. Besides, the basic of the
flashlamp driver, this chapter also discusses and the mode of tringgering the
mechanisme of breakdown in gaseous.
Chapter 3 explains about the experimental methods and the techniques used in
development flashlamp driver. This includes a series injection triggering technique and
image processing software. A Rogowski coil is used to detect the current curve during
the discharge. The calibration of a high voltage power supply that is employed in the
system is described in Chapter 4.
The development of pulse generator using PIC16f84A microcontroller, which is
interfaced to the personal computer using RS232 lines driver is dicsussed in chapter 5.
This generator acts like a control element for the flashlamp driver. The development of
flashlamp driver circuit is covered in Chapter 6. Series injection triggering mode was
employed to trigger a U-shape xenon flashlamp. The pulse current during the discharge
time was measured. The relation of the pulse current and peak power during the
discharge time due to the capacitance value or input energy is also discussed.
The characteristic of flashlamp output is enlightened in chapter 7. The
bandwidth of the flashlamp pulse at FWHM was measured using the IPL10050
photodiode. Plasma spectral gradient induced by xenon flashlamp was recorded with
the aid of CCD Laser Profiler.
8
Finally, the conclusions of the project are noted in Chapter 8. These provide with the
summarization of the whole project and also problems arisen during the period of study.
Finally, a few proposal are suggested for future study.
CHAPTER 2
THEORY OF FLASHLAMP
2.1
Introduction
In the application of light sources for pumping laser, the primary objective is to
convert electrical energy to optical radiation effectively. The most efficient laser pump
lamp will produce maximum emission at wavelengths which excite fluorescence in the
laser. In this chapter, the flashlamp design and its construction are discussed. Optical
characteristics and electrical characteristics of the flashlamp also discussed.
Furthermore the mechanism that leads to the generation of breakdown and how the
flashlamp can be flashed are also described.
2.2
Optical Pumping
Optical pumping system for a solid-state laser consists of a flashlamp, a power
supply to energize the flashlamp, and an optical pumping cavity to direct the flashlamp
light into the laser cavity. In optically pumped solid state lasers, the light source must
supply the maximum possible light output in the spectral region that can be absorbed by
r material. The optical pumping is done with the help of broadband light sources such
as high pressure Hg lamp, xenon flashlamp and even the high incandescent lamp.
10
like halogen (Sirohi, 1985). Optical pumping is widely used for creating population
inversion in laser material. Generally, most solid-state lasers are pumped with optical
sources.
2.3
Flashlamp
Flashlamp was invented by Dr. Harold Edgerton (fondly referred to a papa
flash) in the late 30's and subsequently develop by Perkin Elmer, Incorporation formerly
Edgerton, Germeshausen and Grier, Incorporation (Capobianco, 1998). Flashlamps are
pulsed sources of light. Figure 2.1 shows some typical lamp configurations.
(a)
(b)
(c)
Figure 2.1: Flashlamp Types. (a) Linear flashlamp (b) Helical flashlamp, side and end
views, (c) U-Shaped flashlamp (LEOT, 2001)
11
Linear flashlamps are in the form of straight tubes, and have two electrodes which are
sealed into the envelope. Helical flashlamps offer longer arc lengths and larger wall
areas, and hence can deliver higher pulse energy for a laser rod of a given length. A Ushaped lamp is basically a linear lamp with the ends bent to form a U shape as shown in
the lower portion of the Figure 2.1(c). This configuration allows the electrical contacts
to the end of the lamp to be made conveniently at some distance from the laser rod,
which is adjacent to the long portion of the lamp.
2.3.1
Electrodes and Noble Gases
Important considerations in the structure of flashlamp include the envelope and
the electrodes. A flashlamp consist of a linear, helical or U-shaped quartz tube, two
electrodes which are sealed into the envelope and a gas filled. The material used as the
envelope of the flashlamps for laser pumping applications is silica fused quartz. It is
transparent over a broad spectral range, from the mid infrared well into the ultraviolet.
It also has high thermal conductivity and a relatively low thermal-expansion coefficient.
In the lamp, the transformation of electrical energy into light emitting plasma
takes place at the electrodes. The electrodes in flashlamp must withstand high
temperature and high electrical current density. The simplest of the electrode is the
anode. The anode’s primary purpose is to receive the charge emitted by the cathode and
hence complete the electrical circuit. Most arc lamps employ either pure tungsten for
the anode and 2% thoriated tungsten for the cathode, or thoriated tungsten for the anode
and a compressed pellet of porous tungsten impregnated with barium strontium
aluminate for the cathode (Koecher, 1976). A cathode material with a low work
function makes it easier to trigger the flashlamp. The anode is typically rounded, while
the cathode is pointed for arc stability. Rounded anode also conducts more heat from
the plasma, since it is in contact with more of the plasma surface than the pointed
cathode (Kelinh, 1998). In standard flashlamp, the cathode is more emissive than the
12
anode, hence flashlamps are polarized and will pass current in only one direction
without damage.
Krypton and Xenon are two noble gases most commonly used in laser lamp
design. The gas is filled at a pressure of 300 to 700 torr. Xenon is generally chosen as
the gas fill for flashlamp because it yields a higher radiation output for a given electrical
input energy than other gases. Xenon flashlamp is a device that emit large amount of
spectral energy in short duration pulses. This lamp is a relatively efficient device as it
converts 40 – 60% of the input energy to light in the 200 nm to 1 µm region (Kuhn,
1998). Xenon flashlamps also have greater emission in the blue-green region. Krypton
flashlamps are not widely used because of their cost. They are far more expensive than
xenon’s.
2.3.2
Spectrum of Xenon Flashlamp
The radiation output of a gas discharge lamp is composed of several different
components. The light emitted from the flashlamp contains both discrete line structure
and continuum radiation. The line radiation corresponds to discrete transition between
the bound energy states of the gas atoms and ions (bound-bound transition). The
continuum is made up primarily of recombination radiation from gas ions and
bremsstrahlung radiation from electrons accelerated during collision with the ions. The
spectral distribution of the emitted light depends in complex ways on electron density,
gas type and temperature. Generally, for low values of energy input to the flashlamp,
the line emission dominates. As the energy is increased, the continuum radiation
increases relative to the line emission. Figure 2.2 shows typical spectral emission of the
xenon flashlamp at low energy input. It shows that, the light consist mainly narrow
spectral lines near the long wavelength end of the spectrum. Figure 2.3 shows the
output from the same xenon-filled flashlamp, but at increased input energy. The line
13
emission is still present, but the continuum radiation has increased substantially,
especially at the short-wavelength end of the spectrum.
Figure 2.2: Spectral emission from xenon flashlamp at low electrical loading
(Capabianco, 1998)
Figure 2.3: Spectral emission from xenon flashlamp at high electrical loading
(Capabianco, 1998)
2.3.3
Flashlamp Impedance
The impedance characteristics of a flashlamp determine the efficiency with
which energy is transferred from the capacitor to the lamp. The impedance of
flashlamp is a function of the time and the current density. Most of the triggering
14
systems initiate the arc as a thin streamer which grows in diameter until it fills the tube.
During the growth of the arc, lamp resistance is decreasing as a function of time. The
decreasing resistance arises in part from the increasing ionization of the gas and from
the radial expansion of the plasma. After the arc stabilizes, the voltage-current (v-i)
relationship is described by (Koechner and Bass, 2003) :
V = K 0i
1
2
(2.1)
The flashlamp impedance K0 depends on the arc length, l and bore diameter D of the
flashlamp, and on the kind of gas and fill pressure, p. For xenon the following relation
holds (Koechner and Bass, 2003) :
⎛ p ⎞
K 0 = 1.27⎜
⎟
⎝ 420 ⎠
2.4
0 .2
l
D
(2.2)
Power Supplies For Flashlamp
The major components of a power supply employed in a flashlamp-pumped
laser are a charging unit, high voltage dc charging supply and a trigger circuit for the
flashlamp. Figure 2.4 shows the simplified diagram of power supply for operation of a
flashlamp. The high voltage dc charging power supply is used to charge an energy
storage capacitor. The triggering circuit delivers a high voltage pulse to ionize the gas
and begin the discharge.
15
Figure 2.4: Basic Diagram of power Supplies for Flashlamp (LEOT, 2001)
2.5
Charging Unit
The function of the charging unit is to charge the energy storage capacitor to a
selected voltage within a specified time which depends on the desired repetition rate of
the laser. The capacitor-charging source usually consists of a transformer followed by a
rectifier bridge, a switching element in the primary of the transformer, current-limiting
element and control electronics. The transformer and the rectifier bridge provide the
required DC voltage for the energy storage capacitor from an AC line. The amount of
stored energy in the capacitor bank is determined by the value of capacitance and the
voltage to which the bank is charged. Store energy in a capacitor bank can be
calculated using equation (Capobianco, 2002):
1
E = CV 2
2
(2.3)
Where E is stored electrical energy in Joule, C is capacitance of bank in farad and V is
voltage charge on the capacitor bank in volts.
16
Basically, during the flashing, the capacitor is discharged and appears to be short
circuit. To protect the diodes, transformer and other electronic components, the current
must be limited. This is frequently control by a resistor as the current limiting
components.
2.6
Trigger Circuit
In general, arc lamps require a trigger pulse to cause the initial ionization of the
gas. Triggering is the initiation of an electrical discharge in the gas contained in the
flashlamp. The function of trigger signal is to create an ionized spark streamer between
the two electrodes so that the main discharge can occur. The initial spark streamer is
formed by the creation of a voltage gradient of sufficient magnitude to ionize the gas
column. The discharge of the stored energy into the flashlamp is generally initiated by
a high-voltage trigger pulse. The concept of a voltage gradient is important here, since
it implies the existence of a stable voltage reference surface in close proximity to the
flashlamp. Regardless of the triggering method used, reliable triggering cannot be
achieved without this reference (Koechner, 1976).
There are many ways of triggering flashlamp. The common methods of
triggering flashlamps are external, series injection and parallel triggering. Other
techniques are called simmer and pseudosimmer trigger and also over voltage triggering
method (Alex, 1998).
2.6.1 External Triggering
External triggering uses a high voltage trigger pulse to create a thin ionized
streamer between the anode and the cathode within the lamp. Ionization starts when gas
17
adjacent to the tube wall is excited by the voltage gradient induced by this high voltage
pulse. The high-voltage trigger signal is applied directly to a trigger wire outside the
lamp envelope, as illustrated in Figure 2.5. A thin nickel wire can be wrapped around
the surface of the quartz envelope. The wire must touch the glass over as much as
possible of the length, between the electrode inner tips, for most reliable operation. A
high voltage is generated by discharging a capacitor through the primary of the
transformer. This type of circuit can use small, lightweight, and inexpensive
transformers. The main advantage of external triggering is that the energy-discharge
circuit is independent of the trigger circuit. A major disadvantage of external triggering
circuits is that the trigger voltage is exposed.
Figure 2.5: External triggering circuit (Alex, 1998)
2.6.2 Series Injection Triggering
In series triggering, the secondary winding of the trigger transformer is in series
with the energy-storage capacitor and the flashlamp. The pulse is generated in a
transformer whose secondary winding is in series with the flashlamp. This circuit is
shown in Figure 2.6. The high voltage pulse causes initial ionization of the plasma.
When the lamp is ignited, current flowing in the circuit saturates the transformer core.
This means that the saturated inductance of the transformer serves as the pulse-forming
18
inductor. This reduces the overall component count in the circuit. Series triggering
offers reliable and reproducible triggering. Triggering will be enhanced by any ground
planes brought into close proximity into flashlamp envelope. If desired, a trigger wire
may be wrapped around the envelope and brought to ground. Another advantage of
series triggering is it triggers reliability at low capacitor-charging voltages. Also, this
method yields safe and reliable operation in severe environments because all highvoltage sources can be encapsulated. Disadvantages of series triggering include large
size, heavy weight, and high cost of the trigger transformer and large saturated
secondary inductance.
Figure 2.6: Series injection triggering circuit (Alex, 1998).
2.6.3
Simmer Mode Triggering
The simmer mode of operation requires a switching element between the lamp
and the pulse forming network. Using this technique, flashlamp is required to be
triggered only once in sequence of flashes. After triggering, a low-level dc discharge
(known as simmer) is maintained through the lamp. The lamp is initially ignited by the
open circuit voltage of the high voltage power supply. A separate power supply with
specially designed load characteristic is used to force the current to continue flowing in
the lamp in a low, but stable state of ionization. This circuit maintains a steady-state
19
partial ionization of the lamp during the time the lamp is not flashing. Figure 2.7 shows
typical simmer mode triggering circuit. Depending on the flashlamp type, typical
simmer current may be from 100 milliamps up to several amperes. The main discharge
energy, obtained from a capacitor charged to a separate power supply, may now be
switched into the lamp. A semiconductor switch, such as an SCR or a gas or vacuum
gap may also be used. The gas in the lamp will become more highly ionized, producing
a flash as the energy is dissipated. The gas will then be forced to return to the simmer
state.
Figure 2.7: Basic circuit for simmer mode operation. (Alex, 1998)
Basically, the simmer method of operation is used in application where the pulse
repetition is high. At high rates, the flashlamp does not have time to return completely
to its non-conducting state between pulses. It will not recover its ability to hold off the
applied voltage before the next pulses. The energy-storage capacitor will not be able to
be recharged. Its charge would be dissipated through the flashlamp, which is still in a
conducting state. The advantages of simmer mode operation include increased lifetime
for the flashlamp, reduced jitter in the timing of the pulse and improved pulse-to-pulse
reproducibility of the flashlamp output. Simmer triggering mode also reliable for
operation at higher values of pulse-repetition rate and have better control of lamp status.
The control of the lamp status is achieved by monitoring the so-called keep-alive
current. If there is a short circuit or a broken flashlamp, the triggering can be disabled
and no discharge will occur. This feature is usually used in systems with multiple
20
flashlamps. Beside that by using simmer mode the flashlamp life can be increased. The
major disadvantage of this mode of flashlamp operation is the added electronics.
2.6.4 Pseudo Simmer Mode Triggering
At lower pulse-repetition rates, maintaining a simmer discharge during the
longer interval between pulses wastes power. In this case, one may use a pseudosimmer
mode circuit. A pseudo simmer was devised that combines the advantage of a lightweight external trigger transformer with the improvements achieved in simmer mode
system. Figure 2.8 shows the schematic diagram of pseudo simmer mode setup. The
lamp is ignited with an external trigger transformer. Lamp current initially flows
through a limiting resistor, which is in parallel with the SCR. After an appropriate time
delay, the SCR is switched ON, and the high current pulse is initiated.
Figure 2.8: Pseudo-simmer mode circuit (Alex, 1998).
21
2.6.4 Overvoltage Triggering
Overvoltage triggering is a method of flashing a flashlamp without using a
trigger transformer. Energy storage capacitor is charged to a voltage which exceeds the
self-breakdown voltage of the flashlamp. The energy is switched into the flashlamp
using a high voltage or high current switch. This is typically a triggered sparkgap or
thyratron. When the switch is activated, the flashlamp gas breaks down and a flash is
produced. The circuit of this particular system is shown in Figure 2.9.
Figure 2.9: Overvoltage triggering circuit (Alex, 1998)
2.7
The Mechanism of Breakdown
The term gas discharge originates with the process of discharge of a capacitor
into a circuit incorporating a gap between electrodes (Raizer, 1991). Passing of
electrical currents through the electrode gap leads to an array of phenomena known as
22
gaseous discharges (Merle and Oskam, 1978). If the voltage is sufficiently high,
electric breakdown occurs in the gas and an ionized state is formed. A discharge and
electric current that survive only while an external ionizing agent or the emission of
electrons or ions from electrodes is deliberately maintained are said to be non-selfsustaining. As the voltage is raised, the non-self-sustaining current first increases
because most of the charges produced by ionization are pulled away to electrodes
before recombination occurs. As the voltage is raised further, the current sharply
increased at a certain value of V and light emission is observed. These are the
manifestations of breakdown, one of the most important discharge processes.
Breakdown starts with a small number of spurious electrons or electrons injected
intentionally to stimulate the process. The discharge immediately becomes selfsustaining. The energy of electrons increases while they move in the field. Having
reached the atomic ionization potential, the electron spends this energy on knocking out
another electron. Two slow electrons are thus produced, which go on to repeat the
process. The result is an electron avalanche and electrons proliferate. The ionized gas
in the column is electrically neutral practically everywhere except in the region close to
the electrodes, hence this is plasma (Raizer, 1991).
When the lamp is non-ionized it has very high impedance, all the power supply
unit current flows into the capacitor bank. If the voltage across the capacitor reaches a
value to the self breakdown voltage of the lamp, ionization of the lamp gas start to
occur. The impedance of the lamp begins to fall. A low impedance path quickly forms
between the electrodes of the lamp as more gas atoms are ionized. Current now flows
from the capacitor into the lamp and the impedance of the lamp continues to fall. If
sufficient charge is available, the plasma of ionized gas in the lamp completely fills the
bore. Eventually all the energy stored in the capacitor is expended and the lamp returns
to a de-ionized state. Conduction through the lamp ceases and the power supply unit
begins to recharge the capacitor and thus the process continues (Heraeus Noblelight,
2003).
23
2.8 Summary
In this chapter, the flashlamp was briefly discussed. Optical and electrical
characteristic of the flashlamp also discussed. There are many methods for triggering
the flashlamp, but in this study a series triggering method was used to trigger a Ushaped xenon flashlamp.
CHAPTER 3
METHODLOGY AND MATERIALS
3.1
Introduction
This chapter will discuss about the procedures and the techniques used in this
research. Besides the experiment set-up, the major equipment and materials employed
are also described. In general, the work done is concentrated on the development of
programmable driver circuit for U-Shaped xenon flashlamp and diagnosing flashlamp
output in relation to the energy input delivered to the lamp.
3.2
Xenon Flashlamp
In this study, a U-Shape flashlamp was employed. A photograph of the
flashlamp is shown in Figure 3.1. This flashlamp has diameter of 6.00 mm and the
overall length of 32.00 mm. The gas filled for this flashlamp is xenon. Each end was
connected to cathode and anode. The line in the center is utilized for ground plane.
25
6.00 mm
32.00 mm
Figure 3.1: U-Shape Xenon Flashlamp
3.3
Capacitor Bank
The function of the capacitor is to store the electrical charge when voltage is
applied within specific time. In this experiment, sixteen of axial metallised propylene
capacitors are used in each bank. Each capacitor has capacitance of 0.56 µF and
voltage rated at 2000 V. A photograph of a capacitor used in this research is shown in
Figure 3.2. In this study the capacitor values were varied in order to change the input
energy to the flashlamp. The capacitors were assembled into six capacitor banks which
connected in parallel. The schematic circuit each of capacitor bank is shown in Figure
3.3.
Figure 3.2: Photograph of a capacitor
26
Figure 3.3: Schematic circuit of a capacitor bank
Basically, the capacitors in each bank are arranged in series and parallel. Two capacitor
was connected in series is in order to withstand 4.0 kV. The total capacitance in each
bank can be computed as follows;
For two capacitors in series, the total capacitance can be calculated using (Grob, 1997):
CT =
=
C1 × C2
C1 + C2
(3.1)
0.56 × 0.56
0.56 + 0.56
= 0.28 µF
The total capacitance in parallel arrangement, CT can be calculated as (Grob, 1997):
CT = C1 + C2 ..... + Cn
(3.2)
= 0.28 + 0.28 + 0.28 + 0.28 + 0.28 + 0.28 + 0.28 + 0.28
= 2.24 µF
From the Equation (3.2), the total capacitance for each bank was 2.24 µF. By
using the same equation, totals capacitance for six capacitor banks which connected in
parallel was13.44 µF. Having this amount of capacitances, allowed the circuit to vary
in the range of 2.24 µF up to 13.44 µF.
27
3.4
High Voltage Power Supply Calibration
In this research, a Textronix P6015 High Voltage Probe Compensating
with ratio of 1:1000 was employed for calibration work. A photograph of Textronix
P6015 High Voltage Probe Compensating is shown in Figure 3.4. The calibration work
was done to ensure the voltage reading is correct. The schematic diagram for the
calibration work is shown in Figures 3.5.
Figure3.4: Photograph of Textronix P6015 High Voltage Probe Compensating
High Voltage
Power Supply
(0 - 15 kV)
Capacitor
Bank (2.24
µF-13.44 µF)
Oscilloscope
Digital HP
5422A
Figure 3.5: Schematic diagram of calibration work
28
3.5
PIC Programming
The PIC was originally design as a Programmable Interface Controller (PIC) for
a 16-bit microprocessor (Benson, 1997). Programming a PIC microcontroller has three
steps process. The three items to start programming and building project are PIC
compiler programmer, PIC programmer and PIC itself.
In this study, programs were developed and downloaded from a personal
computer running Linux to PIC16F84 via a simple serial port programmer. First, an
assembly language program was written uses a text editor namely KWrite. In order to
make PIC16F84 understands the program, a translator is required. The translator
interprets each instruction written in assembly language as a series of zeros and ones
which is meaningful to the microcontroller. The process of programming a PIC16F84
microcontroller is shown in Figure 3.6.
Figure 3.6: The process of programming a microcontroller
There are many available programmers for PIC based application under Linux.
However, in this study YAPPA graphical development environment was used in order
to program the PIC16F84 microcontroller. YAPPA was written by Mark Colclough in
29
1999. YAPPA is an integrated editor, assembler and programmer interface for the
PIC16F84, running under Linux. The other requirements needed in order to use this
integrated development environment (IDE) include Linux, phython, Yappa , Picprog
and a serial programmer.
Prior to YAPPA development, a few software needed to be installed. YAPPA
relies on Picprog. Hence, Picprog software needs to be installed (picprog-1.0.i386.rpm)
first. This software is available from YAPPA home site (Apendix A). Picprog was
written and distributed by Jakko Hyvätti (2004) for communication with the
programmer. Picprog was used to program or burn PIC16F84. Then we need to install
Yappa: yappa-0.5.2-1.i386.rpm program. Other software needed is GNU PIC Utilities
gpasm. The GNUPIC utilities project gputils, contains many things among which is
gpasm, an open source replacement for Microchip’s MPASM. Currently, it is
supported by Craig Franklin and Scott Dattalo. This software can be downloaded from
home site as in Apendix A. This gpasm will compile and translate assembly language
into hexfile which PIC16F84 understands.
Another requirement is the programmer hardware. Figure 3.7 shows the circuit
diagram of the YAPPA programmer hardware. The serial connector pin numbers
shown are for a 9-pin female D connector.
30
10 K
7
4
8
3
2.2 K
IN4148
14
1
2
3
4
6
5.6 V
7
2.2 µF
8
9
RA2
VDD
RA3
RA1
RA0
RA4/TOCKI OSC1/CLKI
MCLR
OSC2/CLK2
RB0/INT
RB7
RB1
RB6
RB2
RB5
RB3
VSS
RB4
18
17
16
15
13
4.7 K
12
11
4.7 K
10
5
5
Figure 3.7: A Schematic diagram of YAPPA programmer hardware
3.6
Flashlamp Driver
In this project, a programmable xenon flashlamp driver was developed. The
hardware was divided in two modules. The digital module incorporates the
microcontroller unit, PIC 16F84A and some peripheral device such as a keyboard.
While, the analog module comprises a high voltage charging unit and triggering circuit
in order to sent trigger pulse to the xenon flashlamp. This driver uses a series injection
triggering method. Figure 3.8 represents the block diagram of the flashlamp circuit.
The core of the flashlamp driver is a PIC16F84A microcontroller that runs on a
+5 V supply and is clocked by a 4 MHz resonator. This microcontroller was interfaced
to a personal computer (running Linux) via RS232 serial port. Silicon controlled
rectifier (SCR) or thyristor steps up the +5 V pulse to +332 V pulse. The +332 V pulse
is further step-upped to +740 V pulse and mixed with +2 kV DC voltage using a 1:2
31
transformer. A linear variable high voltage power supply is used in this development.
It consists of a variac (0-240 V), a high voltage transformer (rated at 22.5 kV and 50
mA) and 50 units of diodes chains (IN4007 rates at PIV of 1 kV, 1 A current).
+650VDC
PC
SCR
PIC16F84A
Microcontroller
Variable DC
Power Supply
(0-15kV)
CapacitorBank
1:2 Series Injection
Transformer
Figure 3.8: Block diagram of programmable flashlamp circuit
3.7
Current Measurement
It is important to know the peak current through a flashlamp. In this research,
the current during the discharge time was measured directly, as illustrated in Figure 3.9.
A ceramic resistor of 0.1 Ω, 3 W is connected between the cathode of the flashlamp
electrode and the ground. The voltage across the 0.1 Ω resistor is measured using a
Textronix 3034B digital oscilloscope. From the Ohm’s Law, V=IR, the current during
the discharge can be calculated.
32
A current transformer mode of the Rogowski coil as shown in Figure 3.10 is
used in order to detect the current waveform during the discharge time. The coil is
terminated with a small resistance, R. The R equals 0.1 Ω (Jalil, 1990).
+
Xenon Flashlamp
0.1Ω
Textronix
3034B
Oscilloscope
Figure 3.9: Current Measurement
Discharge
Current
0.1Ω
Textronix
3034B
Oscilloscope
Figure 3.10: Rogowski coil as a current transformer
33
3.8
Photodetector
The xenon flashlamp output can be detected by a high speed IPL10050
photodetector. The rise time of the photodetector is typically 25 ns. This photodetector
has a medium surface area of the pin photodiode about 41.3 mm2 and have response
wavelength range at 350 nm – 1100 nm. Details technical specification of this
phodetector is listed in Appendix A. The IPL10050 photodiode was placed in a series
circuit comprising a 9 V DC source and 5.8 MΩ load impedance, such as shown in
Figure 3.11.
The flash light output was aligned horizontal. The pulsed flashlamp output was
then detected by the photodetector, which was connected to a Textronix 3034B digital
oscilloscope. The time delay of the pulsed flashlamp output after being triggered was
noted from the oscilloscope display panel.
5.8 M
IPL10050
Photodetector
Textronix 3034B
Oscilloscope
9V
Figure 3.11: IPL10050 Photodetector circuit
3.9
Attenuator
In this study, a FSQ-OD200 filter manufactured by Newport Corporation (2004)
and a 03 FIV 038 manufactured by Melles Griot (1997) were employed to filter the
34
flash light. FSQ-OD200 is an absorption natural density filter which has 1.0%
transmission at 546.1 nm and 2.0 optical density (OD) at the same wavelength. Optical
density is defined by the following relationship:
⎛1⎞
OD = log⎜ ⎟
⎝T ⎠
(3.3)
Where, T is the transmission (0≤T≤1).
Melles Griot 03 FIV 038 is an interference filter. This filter has minimum
transmittance of 50% at 500 nm. Photographs of both filters are shown in Figure 3.12.
These filters were used to filter the flashlight coming out from the xenon flashlamp
before detected by the photodiode.
(a)
(b)
Figure 3.12: Photograph of filters used in the research. (a) Melles-Griot 03 FIV 038
filter. (b) Newport FSQD200 filter
3.10
Image Processing System
A Beamstar CCD Laser Beam Profiler, manufactured by OPHIR OPTRONICS
(2003) was employed for diagnosing the profiles of the xenon flashlamp output. It
comprised of a video camera and personal computer card for imaging, capturing and
35
perform two and three dimensional intensity distribution of the laser beams. The option
screen of CCD Beam Profiler is depicted in Figure 3.13. The xenon flashlamp output is
a bright source of visible light and has a large spot area. Hence, in this study the
standard BeamStar camera has to be connected with a BeamStar U Range Beam
Extender or Beam reducer telescope. Thus, the spot area on the image of arc profile
was captured and recorded. The area of intensity distribution was analyzed by VideoTest 5.0 software.
Figure 3.13: CCD profiler option window
3.10.1 Image Processing
The image captured by CCD video camera was analysed by using a Video Test
5.0. software. The function of this software is to determine an area of xenon flashlamp
36
spectral profile output. The output was recorded using OPHIR CCD Laser Beam
Profiler. Prior for performing any measurement, a calibration was carried out. In this
calibration works, a magnification factor was computed. The original size of the object
can be determined by dividing the image size with magnification. From the option, the
calibration factor can be applied to any desirable measurement. Furthermore, an
accurate distance or calculated area measurement can be made via a marker when the
grid option was active. Normally, computer used pixel as a grid of measurement and in
practice the S.I unit such as millimetre, centimetre or metre was used to measure
distance and area. The calibration screen of Video Test 5.0 is depicted in Figure 3.14.
Figure 3.14: Calibration screen option for Video Test 5.0 software
The result of the calibration showed that, the ratio between the measurement
taken in real field and from computer unit was 10 mm is equal to 145 pixel or 0.068 mm
per pixel. This calibration factor was saved into active mode. It can be applied to
measure the real distance and area of the damage or beam spot on the sample.
37
3.11
Diagnose the Flashlamp Output
The xenon flashlamp output was diagnosed using arrangement shown in Figure
3.15. Input energy level was altered by varying the storage capacitor. The flashlamp
output was recorded by using BeamStar U. The recorded images were then transferred
into personal computer. Image processing software was used to analyse the data. The
images recorded from BeamStar CCD were analysed by OPHIR CCD Laser Beam
Profier software and Video Test 5.0 to determine the spot area as function of variable
capacitance value. The used of IPL10050 medium area photodiode is to detect the
output curve of the flashlight.
PC
Controlled
Flashlamp Driver
Xenon
Flashlamp
RS232
PC
PC
Controlled
BeamStar CCD
Beam
Splitter
BeamStar
CCD
Flashlamp Driver
Circuit
03 FIV 038 Filter
OD 2.00 Filter
3.ummary
Optical Line
Electronic Line
Oscilloscope
IOL10050
Photo detector
Figure 3.15: Block diagram of experiment arrangement
38
3.12
Summary
The purpose of this study is to develop a programmable flashlamp driver. In
order to develop the driver, the characteristics of the materials used must be identified.
In this experimental, two modules were done. First module is the development of the
flashlamp driver. Second part is the metallurgy used to study the characteristics or
performance of the develop system. The material used in this development was
discussed briefly in this chapter. Besides, the methodology and the arrangement setup
employed in this study also discussed.
CHAPTER 4
CALIBRATION OF HIGH VOLTAGE POWER SUPPLY
4.1
Introduction
The major components of a power supply employed in a flashlamp-pumped
laser are charging unit and flashlamp trigger circuit. The function of the charging unit
is to charge the energy storage capacitor into a selected voltage within a specific time.
In this chapter, the charging unit will be discussed. An existing high voltage power
supply was employed. This high voltage power supply is employed to provide the
required DC voltage for the energy storage capacitor. The energy storage capacitor was
divided into six-capacitor bank. The capacitance of each bank is 2.24 µF. Thus, in this
investigation, capacitance can be varied from 2.24 µF up to 13.44 µF. This section will
describe the calibration of high voltage power supply employed in this experiment. The
calibration work is important in order to get the required voltage for developed system.
4.2
High Voltage Power Supply
An existing high voltage charger with output rating of 15 kV has been employed
in this research. This power supply is used to charge up the capacitor banks.
40
The high voltage power supply comprises of a high voltage transformer rated at 22.5
kV, 50 mA with 50 units of IN4007 diodes rates at PIV of 1 kV, 1 A current. These
diodes are used as rectifier elements. Besides, it also comprised of a gravity operated
solenoid plunger safety dumping system. The diodes are connected in series and
inserted into plastic tubing filled with transformer oil. This oil was used to absorb the
heat when current pass through the diode. Special brass are used to ensure that ends of
the diode chain protrude out, one at each end, whilst keeping the oil in. A variac (0 –
240 V) was employed in order to get the variable voltage output.
One of the transformer output is connected to the capacitor via the diode chain
in series. The other end of the transformer is connected to the earth side of the
capacitor. In the event of a power failure the high voltage on the capacitor is dumped to
ground through a ballast resistor of 200 kΩ.
When the high voltage switch is ON, current from the transformer will flow
through the diodes, into the ballast resistor and then into the output. The output voltage
value is based on the ammeter which is connected with 33.3 MΩ in series. From the
Ohm’s Law V=IR, we can calculate the output voltage. A photograph of high voltage
power supply is shown in Figure 4.1. The schematic diagram of the high voltage power
supply is shown in Figure 4.2.
Figure 4.1 : Front panel of high voltage power supply
41
Main
Fuse
Mains
ON
Switch
o
L o
Main ON
Indicator
To capacitor bank
33.3
MΩ
High Voltage ON
Switch
o
µA
A
50 Diode
Chains
High
Voltage
ON
Indicator
100 kΩ/ 200 W
To
Fuse
o
o
Solenoid
Microswitch at
Dumping
Switch
Solenoid
100 kΩ/
200 W
Charging
Resistor
o
N o
B
o
Dumping
Switch
Variac
A
B
High Voltage
Transformer
Figure 4.2: High voltage power supply schematic diagram
42
4.3
Power Supply Calibration
In this calibration work, a Textronix P6015 High Voltage Probe Compensating
was employed to attenuate the voltage. High voltage from the power supply can be
varied by adjusting the variac. Calibration was done by varying the variac and reading
the current. The corresponding voltage was displayed and measured on the oscilloscope.
Two procedures were carried out, first the voltage was measured by increasing the
current. Then the same experiment was repeated by decreasing the current. Current
was increased with the increment of 10 µA. The block diagram for calibration work is
shown in Figure 4.3.
High Voltage Power Supply
Capacitor Bank
Textronix P6015 High Voltage
Probe Compensating
1000X 3pF 100 MΩ
Oscilloscope Digital
HP 5422A
Figure 4.3: Flowchart of calibration work
For this calibration, the voltage was measured three times for each increasing
and decreasing current. An average of the three voltages was calculated in both
experiments. The data obtained from both experiments are listed in Table 4.1 and Table
4.2.
43
Table 4.1: Voltage reading for increasing current
Current,I
(±1 µA)
0
10
20
30
40
50
60
70
80
90
I
0.00
0.48
0.94
1.28
1.64
2.10
2.42
2.78
3.06
3.38
Voltage, V (±0.01 kV)
II
0.00
0.56
1.00
1.26
1.74
2.16
2.50
2.84
3.06
3.38
III
0.00
0.44
0.84
1.22
1.54
1.94
2.32
2.74
3.02
3.30
Average,V
(kV)
0.00
0.49
0.93
1.25
1.64
2.07
2.41
2.79
3.05
3.35
Table 4.2: Voltage reading for decreasing current
Current, I
( ±1µA )
0
1
10
20
30
40
50
60
70
80
90
I
0.00
0.02
0.42
0.80
1.22
1.60
1.96
2.32
2.76
3.08
3.38
Voltage,V (±0.01 kV)
II
0.00
0.03
0.44
0.76
1.18
1.58
1.92
2.32
2.66
2.96
3.38
III
0.00
0.02
0.42
0.84
0.96
1.54
1.92
2.30
2.62
2.92
3.30
Average,V
( kV )
0.00
0.02
0.43
0.80
1.12
1.57
1.93
2.31
2.68
2.99
3.34
The collected data in Table 4.1 and 4.2 are used to plot a graph voltage versus
current. The plotted graph is shown in Figure 4.4.
Voltage (kV)
44
y = 0.0371x + 0.1267
3.4
3.2
3
2.8
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
y = 0.0374x + 0.0291
increasing
decreasing
0
10
20
30
40
50
60
70
80
90
100
Current (mA)
Figure 4.4: Graph of voltage (kV) versus current (µA)
The graph in Figure 4.4 shows the linear relationship between voltage and
current reading. Both graphs are linear. This indicate that the calibration has full filled
the Ohm’s Law, V=IR. From the gradient of the graph, the resistance of 37.1± 1.57
MΩ was obtained for increasing value. While for decreasing current, the gradient of the
graph was found to be at 37.4± 0.75 MΩ. Both of the calibrations are in good
agreement with the applied resistor which is 33.3 MΩ.
The sample output of the power supply displayed on the oscilloscope HP 5422A
is shown in Figure 4.5. The straight line signal is obtained as a result of filtering by the
storage capacitor.
45
1.20 kV
igure 4.5: Oscillogram of straight line signal is obtained as a result of filtering by
storage capacitor
4.4
Summary
The high voltage power supply was calibrated. The result obtained from the
calibration shows that, the voltage was found to be linear to the current. This indicates
the power supply is full-filled the Ohm’s Law. This power supply will utilize as the
charging unit for the development of flashlamp driver.
CHAPTER 5
DEVELOPMENT OF PULSE GENERATOR
5.1
Introduction
A control part is required in order to trigger a flashlamp (Whi-Young Kim et-al,
2001). The pulse control device is the heart of the flashlamp driver. The pulse control
device will trigger the driver circuit for the flashlamp. Normally, the flashlamp is
recommended to be triggered by a pulse with microsecond pulse width (Heraeus
Noblelight, 2003). Hence, a control device needs to be designed to meet this
requirement. This device may generate pulse consecutively and thus can create diverse
pulse shapes. In this project, a pulse generator was designed using PIC16F84A
microcontroller. This microcontroller can be programmed via a personal computer.
The PIC16F84A devices are programmed using a serial programmer.
5.2
Power Supply for Microcontroller
In generally, the correct voltage supply is of utmost importance for the proper
functioning of the microcontroller system. According to technical specification by the
manufacturer, PIC16F84A device requires supply voltage of VDD between 4.5 V to
47
5.5 V) (Microchip, 2002). In this experiment, a voltage regulator namely LM7805
which gives stable +5 V on its output was used.
In order to have a stable 5 V at the output (pin 3), input voltage on pin 1 of
LM7805 should be between 7 V through 24 V (Nebojsa, 2000). The schematic circuit
of the +5 V power supply to power up the PIC microcontroller is shown in Figure 5.1.
Basically, the transformer will step down the main voltage (∼ 230 V) to ∼14 V. The
bridge rectifier will convert the ac voltage to dc voltage. The function of LM7805 is
converting +16 V input voltage at pin no. 1 into 5 V at pin no. 3. This +5 V will be
used to power up PIC microcontroller. Figure 5.2 shows the oscillogram of the +5 V as
an output of the LM7805 at channel 3 and +16 V input voltage at pin no 1 as recorded
at cannel 4.
∼ 230 V
1
∼14 V
LM7805
2
4700
µF
Figure 5.1: Schematic diagram for +5 V power supply
3
+5 V
48
16 V
Time Based: 100 µs
OSC Sampling Rate: 5GS’s
Channel 3: Signal of input
voltage.
Channel 4: Signal of output
voltage.
5V
Figure 5.2: Oscillogram of +5 V supply and +16 V input voltage for the LM7805
5.3
Pulse Generator
A pulse generator is required in order to control the flashlamp driver. In this
experiment, the control circuit consists of PIC16F84A microcontroller, which is the
most important part of the control circuit, a MAXIM 233 RS232 driver and a personal
computer.
5.3.1 PIC16F84A Microcontroller
PIC16F84A microcontroller belongs to Microchip family. This device is
fabricated using CMOS technology and has only 35 single word instructions and
contains 1K words, which translates to 1024 instructions (Microchip, 2001). The 1024
bytes flash memory on board PIC16F84A allows program to be loaded and erased with
ease. It can be programmed, tested in circuit and reprogrammed if necessary in a matter
of a few minutes and without the need for UV EPROM eraser (Benson, 1997). This
49
microcontroller has 13 input/output pins each with individual direction control. The Pin
diagram and the internal block diagram of the PIC16F84A are shown in Figure 5.3 and
5.4, respectively.
Figure 5.3: Pin diagram of PIC16F84A (Microchip 2001)
Figure 5.4: Internal block diagram of PIC16F84A (Microchip, 2001)
50
5.3.2 MAXIM233 RS232 Driver
In order to connect a microcontroller to a serial port on a PC computer, we need
to agree in the level of the signals so communicating can take place. The RS232 signal
level on a PC is -10 V for logic zero, and +10 V for logic one. Since the signal level on
the microcontroller is +5 V for logic one and 0 V for logic zero, we need an
intermediary stage that will convert the levels to RS232. The chip specially designed for
this task is MAX233. This chip receives signals from -10 V to +10 V and converts them
into 0 and 5 V and vice versa. The MAX233 contain four sections, namely the dual
charge-pump DC-DC voltage converter, RS-232 driver, RS232 receiver, and receiver
and transmitter enable control inputs. Figure 5.5 shows the typical operating circuit for
the MAXIM 233.
Figure 5.5: Typical operating circuit for MAXIM233 (MAXIM, 2003)
51
5.3.3 Pulse Generator Circuit
The pulse generator circuit was divided in two modules, namely the hardware
and software. Schematic of the pulse generator based on PIC16F84A is shown in
Figure 5.6. The RC circuit, consist of 4.7 µF capacitor in series with a 10 KΩ resistor,
connected between the +5 V supply voltage and ground. The MCLR is connected to the
RC circuit. A 4 MHz ceramic resonator was connected to pins no. 15 and 16. This
resonator was used as external clock oscillator. Ceramic resonator was chosen because
it has built-in capacitors, small and inexpensive while providing good accuracy within ±
1.3 percent or better (Benson, 1997). This external clock frequency is divided by 4
internally. A pair of PORTA input/output (pin no.17 and 18) lines connects
PIC16F84A to a personal computer via MAXIM 233’s RS232 driver. MAXIM 233’s is
used as voltage converter. Pin no. 18 (PIC16F84A) is connected to pin no.3 (MAXIM
233) while pin no.17 (PIC16F84A) is connected to pin 1 (MAXIM 233). Pin no. 4
(MAXIM 233) is connected to pin no. 3 of 9-pin male D connector and pin no. 18
(MAXIM 233) is connected to pin no. 2 of 9-pin male D connector.
Second module is the software. The language used in PIC16F84A
microcontroller is called Assembly Language. Programs were written using K-Write
application and saved as .asm file. The developed program is shown in Appendix B.
Programs were developed and downloaded from a PC (running Linux) to PIC16F84 via
a simple serial port programmer.
52
+5 V
4
2
3
18
17
15
RS232
12
11
10
9
T1IN
VC2C2+
V-
T2IN
R1OUT
T1OUT
C1C1+
C2+
R2IN
C2-
R2OUT
GND
GND
6
V+
1
18
2
17
3
5
4 MHz
Ceramic
Resonator
16
15
14
13
13
12
19
11
20
1O
8
Figure 5.6: Schematic diagram of pulse generator circuit
RA1
14
VDD
RA0
OSC1
OSC2
RB7
RB6
TOCK/RA4
MCLR
INT/RB0
RB5
RB4
RA2
RA3
PIC16F84A
16
T2OUT
MAXIM233
5
R1IN
7
VCC
+5 V
RB1
RB2
GND
5
RB3
1
2
3
4
4.7 µF
6
7
8
9
to TIP 31A
53
Generally, serial communication comes in two flavors, synchronous and asynchronous
(John, 2000). Synchronous communication uses a clock line to determine when the
information on the serial line is being used. While, asynchronous communication
doesn’t use a clock line. In lieu of clocking line, asynchronous communication requires
start bit and stop bits in addition to the strict data time frame. The start bit informs the
receiver that of information is about to be transmitted. In this experiment the port or
device used ttyS1. This device is similar to COM2 in windows. The ttyS1 setting port
is shown in Figure 5.7. In this study, the baud rate was set at 4800 bps, the data are sets
as 8 data bits, no parity and 1 stop bit.
Figure 5.7: ttyS1 port setting
54
The programmable menu for the pulse generator is shown in Figure 5.8. Basically, the
PIC16F84A listens for the data on pin no.18 connected to the RS232 serial port on the
PC through MAXIM233. This pin functions as receiver for serial communication.
When a character is typed, the data gets parsed by the PIC and sent off to the PC
through pin no.17. Beside, it also transmits (echoes) the character received back to the
PC via RS232.
Figure 5.8: Programmable pulse generator menu (Linux Shell scripting)
A typical TTL pulse output from the PIC16F84A microcontroller is shown in
Figure 5.9. This TTL pulse output from the PIC16F84A is observed and captured by a
Tektronix 3034B oscilloscope. Minimum pulse width that can be generated from this
microcontroller was found to be 1 µs using the 4 MHz external clock. This is because,
based on the internal device characteristics of the PIC16F84A microcontroller, the clock
frequency is divided internally by 4. This TTL output pulse will be used to trigger the
55
SCR gate for triggering circuit. Details about the triggering circuit will be discussed in
Chapter 6.
5V
1 µs
Time Base: 1µs
OSC Sampling Rate: 5GS/s
Figure 5.9.: 1 µs pulse width (Single pulse)
5.4
Summary
A programmable pulse generator using PIC16F84A was successfully designed.
This pulse generator can be controlled remotely to the triggering circuit. Minimum
pulse width for TTL pulse output was found to be 1µs using 4MHz clock that will be
used to trigger the SCR for the flashlamp circuit.
CHAPTER 6
DEVELOPMENT OF FLASHLAMP DRIVER
6.1
Introduction
Flashlamp is a pulsed source of light. It is filled with gas and have two
electrodes sealed into the envelope. The power supply for operation of a flashlamp
consists of high voltage dc power supply, energy storage capacitor and trigger circuit.
In this chapter, the developed flashlamp driver will be discussed. The flashlamp
driver was developed based on series injection triggering method. The heart of this
flashlamp driver is a PIC16F84A, which acts as the control element. The current set-up
allows the flashlamp to be triggered in a single pulse mode.
The flashlamp output is diagnosed based on the common electrical parameters
such as peak current and peak power during the discharge time. Besides, the current
waveform of the flashlamp was also investigated.
57
6.2
PSpice Simulation
Modelling and computer simulations play an important role in analysis and
design of power electronic system. Computer simulations are commonly used in
research to analyse the behavior of the circuit. In this study, PSpice 8.0 computer
simulation was employed. The schematic of the simulated circuit is shown in Figure
6.1. SCR used in the triggering circuit acts like a switching. In this simple simulation,
the SCR was substituted with pulse source. The pulsewidth was set to 1 µs and
amplitude of 650 V as supplied to anode terminal of SCR in the designed circuit.
V1=+650V
PW=1us
Figure 6.1: Schematic diagram of RLC simulation circuit
Typical result obtained from the simulation is shown in Figure 6.2. This
waveform is simulated using the transient analysis. As depicted in the Figure (6.2), the
waveform corresponds to the action of turn-off the SCR. Tank circuit connecting in
series with the SCR produces reverse voltage. A negative or reversed voltage produced
from the tank circuit will turn off the SCR. This is because the tank circuit produced
reversed current below the holding current that is 40 mA (Motorola, 1999) which is will
turn OFF the SCR.
58
Described the action of
turn-off SCR
Figure 6.2: Tank circuit simulation waveform
6.3
Flashlamp Driver
In this project, a programmable xenon flashlamp driver was developed. The
hardware was divided in two modules. The first part is the digital module which
comprises of microcontroller unit, PIC 16F84A. Details about digital part have been
described previously in Chapter 5. The second step is the analog module itself. The
analog module comprises of a high voltage charging unit and the triggering circuit in
order to send trigger pulse to the xenon flashlamp.
The core of the flashlamp driver is a PIC16F84A which acts as a control circuit.
In this control circuit, single pulse duration is entered by the keyboard. This input is
conveyed to PIC which in turn output aTTL signal in accordance with the
predetermined program. But this signal is too weak to turn on the SCR gate. For this
reason, a TIP31 transistor was inserted which plays a role in amplifying the current and
voltage of the transformed signal. Figure 6.3 represents the block diagram of the driver
circuit.
59
PC
PIC16f84A
Microcontroller
Amplification
Circuit
U-Shaped
Xenon
Flashlamp
Charging
Unit
SCR
Circuit
Figure 6.3: Block diagram of flashlamp driver circuit
In this research, a series injection triggering method was used. In series
injection method, the secondary winding of the trigger transformer is in series with the
energy-storage capacitor and the U-shaped xenon flashlamp. Because of the driver
circuit involved in the discharge process produces a large amount of current; a great
care must be taken to ensure that the whole circuit is protected. Hence, a 1:1 isolation
pulse transformer was employed in order to isolate the digital part and analogue
module. Figure 6.4 shows a schematic diagram of the developed system.
High voltage power supply consists of a variac (0-240 V), transformer and
rectifier. This high voltage supply can charge the capacitor up to 15 kV. This output
far exceeds the flashlamp breakdown voltage. Hence, in this experiment, the charging
voltage was fixed and set at 2.0 kV DC. In this experiment, the capacitance value was
also varied in the range of 2.24 µF up to 13.44 µF. By changing the capacitor value, it
will effect the electrical energy or input energy into the flashlamp. The electrical
energy in Joule is given by:
1
E = CV 2
2
Where, C is the energy storage capacitance in µF and V is the discharge voltage in
volts.
(6.1)
60
V = +650 V
IN4007
main
1:2
120 Ω
+5 V
PIC
150 Ω
2Ν6398
TIP31
250 Ω
IN4007
IN4007
1:1 Isolation
Transformer
IN4007
A
High Voltage
= 2.0 kV
B
0.1µF
IN5408
1:2 Series
Injection
Transformer
Xe Flashlamp
FigureFigure
6.4: Schematic
diagram
of flashlamp
driverdriver
6.3: Schematic
diagram
of flashlamp
Capacitor Bank
(2.24µF
µF-13.44
(2.24
– 13.44mF)
µF)
61
Initially, the TTL pulse output from PORTB0 I/O line from PIC16F84A will drive a
power transistor namely TIP31. This amplified signal will turn on SCR gate. Typical
result obtained is showed in Figure 6.5.
5V
Time Based: 1.00 µs
OSC Sampling Rate: 5GS’s
Channel 1: 5 V TTL pulse
output
Channel 2: Gate turn on signal
of 2N6398
5V
Figure 6.5: A TTL pulse output from PIC16F84A and SCR gate turn-on signal
Figure 6.5 shows the TTL pulse output from the PIC16F84A at channel 1.
While, channel 2 shows the gate turn-on signal of the 2N6398 SCR. The pulsewidth of
the signal was found to be 1 µs with an amplitude of +5 V.
The SCR was used as a power control device. A small gate current can control a
much larger voltage or current in the anode circuit (Elbell, 1978). As depicted in Figure
6.3, a +650 V is supplied to the anode terminal of SCR. Current cannot pass through
until trigger pulse from controller circuit is applied at the gate terminal of SCR. Typical
results obtained are shown in Figure 6.6
62
Action of
SCR turn off
gyijy
(a)
(b)
(c)
Figure 6.6: Voltage waveform. (a) at primary winding of the series injection transformer (point A) (b) At secondary winding of
the series injection transformer (point B) (c) Waveform describes the action of turn-off the SCR
63
When the gate terminal is triggered, SCR allows current to pass through from anode to
cathode of the SCR, producing an output of +332 V at the primary of series injection
transformer as depicted in Figure 6.6(a). The +332 V pulse then is step-up by 1:2 series
injection transformer producing + 740 V. Voltage profile at secondary winding is
shown in Figure 6.6(b). Figure 6.6(c) shows the waveform describes the action of turnoff the SCR. This curve waveform is in good agreement with the simulation result
shown in Figure 6.2. As described previously, the reversal voltage produced from the
tank circuit will turn off the SCR. Turn-off SCR means that all forward conduction has
ceased. The repetition of the positive signal to the anode will not cause the current to
flow without there being a gate signal (Raymond, 1973).
Because of the driver resulted in a large amount of current during the discharge
process, it is desirable to connect freewheeling diode in parallel with the secondary of
series injection transformer. This free wheeling diode was designed to withstand a 2.0
kV. The function of free wheeling diode is to protect the SCR circuit.
Voltage difference across metal electrodes of 2.0 kV does not initiate gas
breakdown in a xenon fashlamp tube which acts as an electrical open circuit. However a
narrow 82.14 µs pulsewidth of 740 V mixed with a 2.0 kV causes gas breakdown. This
electrical short circuit draws large amount of current through the ionized gas. This is
the value at which a large number of gas molecules become ionized. The conductivity
of the gas is increased and the electrons are accelerated to a velocity at which the
electron can ionize more molecules through collisions. De-excitation of these ionized
gas resulted in emitting of high intensity light energy.
64
6.4
Electrical Characteristic
Once triggering has taken place, the plasma will grow within the flashlamp.
Current flows from the capacitor bank through lamp. As current through the lamp
increased rapidly, voltage drop across the lamp falls rapidly. In this study, the behavior
of the peak current during the discharged time as a function of the input energy was
investigated. The input energy was calculated using the equation, E=1/2 CV2.
The flashlamp peak current was measured indirectly by detecting the voltage
drop across a 0.1 Ω resistor in series with the flashlamp as illustrate in Figure 3.9.
Voltage differential across the 0.1 Ω resistor was recorded using a Textronix 3034B
digital oscilloscope. A typical result obtained is shown in Figure 6.7. The peak current
can be obtained using basic equation of Ohm’s Law, V=IR. Substituting R = 0.1 Ω and
the value of V measured from the oscilloscope, the peak current can then be calculated.
84 V
Time Based: 20.00 µs
OSC Sampling Rate: 5GS’s
Figure 6.7: Voltage profile across the 0.1 Ω. The charging voltage and
energy were 2 kV and 13.44 J
65
The input energy injected across the xenon flashlamp were varied in the range of
4.48 J to 26.88 J. The measurements of the peak current upon input energy are listed in
Table 6.1.
Table 6.1: Peak current during the discharging time due to the input energy
Input Energy, E (J)
Voltage, V (0.01V)
Peak Current, I (A)
4.48
77.60
776.0
8.96
84.24
842.4
13.44
89.01
890.1
17.92
92.48
924.8
22.4
95.68
956.8
26.88
98.24
982.4
The collected data in Table 6.1 were used to plot graph such as shown in Figure
6.8. The peak current value was plotted against the input energy given into the
flashlamp during the discharge time.
1000
950
Peak Current (A)
900
850
800
750
700
650
600
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Input Energy (J)
Figure 6.8: Relative peak current of the flashlamp versus capacitor charging
energy
66
Figure 6.8 shows the peak current profile versus input energy delivered to the
flashlamp. From the result obtained, it shows that the peak current was linear with
respect to the input energy. The minimum peak current was found as 776 A and the
maximum peak current was found as 982.4 A.
For the investigation of the current waveform, a Rogowski coil was employed.
Typical current waveform of the xenon flashlamp is shown in Figure 6.9 corresponding
to the input energy of 13.44 J. The current waveform of Figure 6.9 shows that the
discharge circuit is seen to be critically damped. The damping or ringing signal is
caused by the inductance and capacitance in the circuit.
180 mV
Time Based: 10.00 µs
OSC Sampling Rate: 5GS’s
Figure 6.9: A current waveform of flashlamp at input energy of 13.44 J
Other parameter that can be determined is the peak power produced during the
discharged time. Generally, high peak power output from the flashlamp is achieved by
storing electrical energy in high-voltage capacitors and discharging them very rapidly
into the flashlamp. In this investigation, the peak power was calculated using the
equation of P=IV. The current value, I is obtained as listed in Table 6.1. The voltage
value, V was obtained as 2.75 kV for all measurement. The measurements data are
listed in Table 6.2.
67
Table 6.2: Peak power during discharged time upon the input energy
Input Energy, E (J)
Peak Current, I (A)
Peak Power, P (106W)
4.48
776.0
2.13
8.96
842.4
2.31
13.44
890.1
2.44
17.92
924.8
2.53
22.4
956.8
2.62
26.88
982.4
2.69
The data in Table 6.2 are used to plot graph. The plotted graph is shown in
Figure 6.10.
Peak Power (E+06 W)
3
2.5
2
1.5
1
0.5
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Input Energy (J)
Figure 6.10: Relative peak power as a function of input energy
The curve in Figure 6.10 shows that, the peak power is linear with respect to the
input energy. This means, altering the capacitance value changes the production of
peak power.
68
6.5.1 Summary
A programmable driver circuit for U-shaped xenon flashlamp driver have been
developed and characterized. In order to find out the operational characteristics of this
flashlamp driver, parameters such as peak current and peak power were investigated.
Experiment had been performed by adjusting the capacitor value.
The core of the flashlamp driver is a PIC16F84A microcontroller. This
microcontroller was interfaced to a personal computer running under Linux. The
developed driver circuit comprised of a digital module and an analog module. This
flashlamp driver uses a series injection method triggering. Secondary winding of series
injection transformer is connected in series with the flashlamp. A SCR was used as the
switching element. In a DC circuit, the only way to turn-off the SCR is by opening the
main switch. But this is not acceptable for this driver. Hence, a tank circuit was
introduced in order to generate a reverse voltage to switch off the SCR. The method
employed is called forced-turned off method (Berde, 1986). The design circuit was
verified by PSpice computer simulation and also by experimental work.
When the SCR is triggered, gas breakdown will occur in the flashlamp region.
Ionization of the xenon gas will take place and plasma will grows. During the discharge
time a large amount of current will produce rapidly. These current flows can emit high
intensity light energy and this condition called flashing. For this experiment, the
current setup for the developed system allows flashlamp to be flashed in a single shot.
In this study, the peak current during the discharge time was calculated using
equation of V=IR. While for estimating the peak power dissipated from the system, the
basic equation of P=IV was employed. Beside that, the current pulse waveform also
was detected. This measurement was performed using Rogowki coil. Generally, the
peak current and the peak power increase as input energy increases.
CHAPTER 7
CHARACTERISTIC OF THE FLASHLAMP OUTPUT
7.1
Introduction
In this chapter, the characteristics of the flashlamp output upon input energy will
be investigated. In this study, a Beam Star CCD Laser Beam Profiler was used as
diagnostics measurement equipment. The Beam Star CCD Profiler uses a video camera
and PC card to image, capture, store, and perform two- and three- dimensional intensity
distribution analysis on laser beams.
In order to measure an area of intensity distribution of the flashlamp output, a
metallurgical method was employed. Two dimensional images of the intensity
distribution of the flashlamp output were analysed via the Video Test 5.0 software.
Others parameter, which may be important to be investigated is the flashlamp output
curve. This curve was detected by using an IPL10050 medium area photodiode.
70
7.2
Flashlamp Intensity Profile and Light Distribution
In this study, intensity profile of xenon flashlamp output was investigated using
Ophir BeamStar CCD camera profiler. This CCD camera laser beam profile is based on
a mosaic of two-dimensional detector called pixel. The two-dimensional mosaic like
detector instantly records the amount of energy impending on its surface. The intensity
distribution of the laser beam is recorded pixel by pixel and displayed as a twodimensional topographic map or a three-dimensional isometric view.
Flashlamp light coming out from the system is a strong source of visible light
and scattered. Based on the Ophir Beamstar requirement a beam reducer is needed in
order to reduce the size of the light. In this experiment, a BeamStar U Reducer was
attached to the BeamStar CCD and placed at 80 ± 0.5 cm constant working distance.
The optical system of this beam reducer then images the beam on CCD of the BeamStar
and at the same time reduces the size by factor of 4. Figure 7.1 shows the block
diagram of the Beam reducer.
Imaging system
BeamStar
camera
Adjustable
iris
Fluorescent
plate
Figure 7.1: Block diagram of BeamStar reducer
71
Typical two- and three-dimensional images of arc intensity profile of the
flashlamp are shown in Figure 7.2. Three dimensional profile of the flashlamp output is
illustrated in Figure 7.2(a). This three dimensional profile beam is distributed in the
form of Gaussian. Gaussian profile generated by the BeamStar CCD camera analyzer
illustrates the intensity level distribution under pulsed conditions. The red colour
indicated the highest stage of intensity, followed by yellow, green, light blue and finally
the dark blue represents the lowest stage of the intensity. Two-dimensional image of
the flashlamp output is shown in Figure 7.2(b). The dimensional vertical and horizontal
profiles are referenced to the centroid of the plasma.
The BeamStar CCD Profiler determines the location of the beam centroid by
summing the intensities of all image pixels in both horizontal and vertical axes, and
computing the center of gravity of the beam intensity. The pixel coordinates at this
location define the Centroid. The horizontal (H) and vertical (V) coordinates of the
Centroid are computed using the following formula:
H = ∑ {h * i (h, v )}/ I
(7.1)
V = ∑ v * i (h, v ) / I
(7.2)
Where;
i(h, v)
= The intensity at location (h, v)
I
= The total intensity taken over the total area
72
(a)
(b)
Figure 7.2: Arc intensity profile of the flashlamp; (a). Three-dimensional image
shows the distribution of Gaussian beam profile (b). Two-dimensional image
representation in both horizontal vertical axes
Vertical profile and horizontal profile display the profiles from two orthogonal
axes, namely horizontal and vertical. Each image is a digital representation of the
spatial power distribution across the beam. Typical vertical profile and horizontal
profile results obtained from this experiment are shown in Figure 7.3.
73
Figure 7.3: Gaussian profile of xenon flashlamp output
The other parameter, which may be important, is the flashlamp output spot size.
In this study, two-dimensional images captured by video CCD BeamStar camera were
analysed by using Video Test 5.0 software. The function of this software is to
determine the spot area of xenon flashlamp spectral profile output. Typical results of
the two-dimensional are shown in Figure 7.4. The areas of high intensity distribution
(red colour) were measured upon input energy from 4.48 J up to 26.88 J into the
flashlamp. The intensity level for all measurement was set at 10 db and the shutter
speed was set at 1/50.
74
a. 4.48 J
b. 8.96 J
c. 13.44 J
d. 17.92 J
e. 22.40 J
f. 26.88 J
Figure 7.4: Two-dimensional images of xenon flashlamp taken at different input energies
75
Two-dimensional images are arranged in the increasing order of input energy
delivered to the flashlamp. Qualitatively, the spot areas of the flashlamp output in
Figure 7.4 become larger with the increase of the input energy. As the light became
more intense, the larger numbers of pixel corresponding to high energy were detected
by the CCD camera. Colours arrangement of the beam spot almost similar for every
image. The most contrast colour of course can be obviously observed in the image of
Figure 7.4f.
Each of flashlamp output spot area in Figure 7.4 was measured in millimeter
square. The collected data are listed in Table 7.1.
Table 7.1: Flashlamp output spot perimeter and area at different input energy
Input Energy,
Flashlamp Spot
E (J)
Perimeter (mm)
Area (mm2)
4.48
12.55
11.96
8.96
18.01
21.69
13.44
20.79
28.82
17.92
24.46
42.48
22.4
27.50
51.12
26.88
31.53
67.03
The collected data in Table 7.1 are used to plot graph of flashlamp output spot
area against input energy. The plotted graph is shown in Figure 7.5.
Spot Area (mmxmm)
76
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
0
2
4
6
8
10 12 14 16 18 20 22 24 26 28 30
Input Energy J
Figure 7.5: The flashlamp output spot area versus input energy taken at working
distance of 80 cm
Figure 7.5, shows that the area of the flashlamp output increased linearly with
the input energy into the flashlamp. By changing the input energy across the flashlamp,
the current delivered during the discharge time also changes. This result in different
intensity distribution. Result shows that the larger the input energy of the flashlamp;
the larger of spot area is.
7.3
Flashlamp Waveform
In this investigation, an IPL10050 medium area photodiode was employed in
order to detect the flashlight output curve. The detection of optical radiation is usually
accomplished by converting the optical energy into an electrical signal. When light
strikes special type of material, a voltage was generated, a change in electrical
resistance occur, or possibly electrons will be ejected from the material surface. As long
as the light is present, the condition continues. It ceases when the light is turned off.
77
Initially, flashlight output from the xenon flashlamp was detected directly by the
IPL10050 photodetector. This photodetector was placed at constant working distance
of 80 ± 0.5 cm from flashlamp source. The output signal was measured across the 5.8
MΩ load resistor which connected in series with the photodiode as illustrated in Figure
3.11 in Chapter 3. Typical result obtained from this experiment is shown in Figure 7.6.
8.8 V
Time Based: 400 µs
OSC Sampling Rate:
5GS’s
Figure 7.6: Pulse xenon flashlamp output curve with input energy of 4.48 J
Oscillogram from Figure 7.5 shows that the output curve was saturated. The full
waveform cannot be captured because it was limited by the supply voltage of the
detector circuit which is 9 V. Hence, the maximum voltage that can be measured is 9 V
only. In order to measure the full wave half maximum (FWHM) of flash output, a FSQOD2.00 filter was employed. FSQ-OD200 is an absorption neutral density filter which
has 2.0 optical density at 546.1 nm. This filter has broadband attenuation from visible
to near IR. Figure 7.7 shows the oscillogram of the flashlamp output after it was
filtered by the FSQ-OD2.00.
78
8.8 V
Time Based: 400 µs
OSC Sampling Rate:
5GS’s
Figure 7.7: Pulse xenon flashlamp output curve with input energy of 4.48 J after
filtering by the FSQ-OD2.00 filter
The result obtained shows that the full output signal of the flashlamp still cannot
be captured after it was filtered by the FSQ-OD2.00 filter. The full waveform still
cannot be captured because of the flash light coming from the xenon flashlamp is too
intense. Another filter was employed in this study in order to detect the fullwaveform is
03 FIV 038 interference filter. Typical result obtained is shown in Figure 7.8.
3.3 V
Time Based: 400 µs
OSC Sampling Rate:
5GS’s
Figure 7.8: Output Curve of the xenon flashlamp after filtering by FSQ OD200
neutral density filter and 03 FIV 038 interference filter
79
As depicted in Figure 7.6, 7.7 and 7.8, each signal shows that the pulsewidth
was decreased when flashlamp output was filtered. From the figure, it also shows that
the flashlamp output has long tail extending after the emission peak.
In this study, the bandwidth of the flashlamp light output during the discharge
time was investigated. Basically, the short pulse sources are utilized in many
applications. The input energy delivered to the xenon flashlamp was varied in the range
of 4.48 J to 26.88 J. These values are obtained by varying the capacitance values of the
high voltage charging unit. The pulse durations of the flashlamp output are listed in
Table 7.2. The pulse duration is measured at full wave half maximum (FWHM) of the
curve.
Table 7.2: Pulse duration of xenon flashlamp output at various input energies
Pulse Duration, t (± 40 µs )
Input
Energy, E (J)
4.48
8.96
13.44
17.92
22.4
26.88
I
260
320
320
320
340
360
II
280
300
320
320
350
360
III
260
300
320
340
360
380
IV
280
300
300
340
350
380
V
290
320
320
340
340
380
Average
274
308
316
332
348
372
Data collected in Table 7.2 are used to plot graph such as depicted in Figure 7.9.
The pulse duration during the discharged time is plotted against the input energy.
80
400
Pulse Duration (ms)
350
300
250
200
150
100
50
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Input Energy (J)
Figure7.9: Pulse duration profile due to input energy across the flashlamp
The curve obtained indicated that, the bandwidth of the flashlamp signal at
FWHM is linearly with respect to the input energy.
Another parameter that can be determined is the amplitude of light detected by
the photodetector depending upon discharge capacitor value. The amplitudes during the
discharge are listed in Table 7.3. The collected data are used to plot graph of amplitude
against input energy during the discharge. The graph is shown in Figure 7.10.
81
Table 7.3: Amplitude of xenon flashlamp output signal at various input energy
Input
Energy (J)
4.48
8.96
13.44
17.92
22.4
26.88
1
3.7
5.4
6.4
7.6
8.4
8.6
2
3.8
5.2
6.8
7.2
8.2
8.8
Amplitude, V (± 0.1 V)
3
4
5
3.9
3.7
3.8
5.6
6.0
6.0
6.4
6.7
6.8
7.6
7.6
7.4
7.8
8.2
7.8
9.0
8.8
9.0
Average
3.78
5.64
6.62
7.48
8.08
8.84
10
9
8
Voltage (V)
7
6
5
4
3
2
1
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Input Energy (J)
Figure 7.10: Amplitude versus input energy during discharge
Figure 7.9 shows the amplitude profile versus input energy. The graph shows
that, initially the amplitude increase rapidly with respect to the input energy. After the
input energy of 8.96 J, the amplitude is found to be proportional with the given input
energy.
Generally, increasing the input voltage normally increases the amount of
charges in the capacitor. According to the equation of capacitor where, Q=CV, the
amount of charge, Q stored in the capacitance is directly related to the amount of
capacitance, C and voltage, V across the capacitor. Thus, changing the capacitance
82
influenced the production of current flowing across the flashlamp as well as the
intensity of the light emitted. As intensity increases, the amplitude detected by the
photodetector also increases. This is because when the current is increased, more
ionization occurs consequently more spontaneous photons will be liberated.
7.4
Summary
In this diagnostic, the characteristics of the xenon flashlamp output during the
discharged time were investigated. This consists of the profile of the flashlamp output,
the spot area, flashlamp waveform including the pulsewidth and amplitude depending
on variation of the input energy across the flashlamp.
The plasma spectral gradient of the flashlamp was recorded by a OPHIR CCD
Beamstar U. It provides three and two dimensional images of flashlamp output during
the discharge time. The three-dimensional profile illustrates the intensity level
distribution under pulsed condition.
Initially, the two-dimensional of flashlight output profiles were analysed
qualitatively. From the analysis, the dimension of the flashlamp output was increased
as the input energy increases. The highest density of contrast colour of the flashlamp
output was found at the input energy of 26.88 J. This indicates that at greater input
energy, it provides brightest intensity. In general, the spot areas of the flashlamp output
are dependent on given input energy. By increasing the input energy the spot area
becomes wider.
Flashlamp output waveform observation during the discharged time was
performed by using IPL10050 photodiode. The pulse duration of the flashlamp curve at
FWHM were found linearly increased with the input energy. Similarly, the amplitude
83
of flash output detected by the photodiode was also found to be linear with the
input energy.
CHAPTER 8
CONCLUSIONS AND SUGGESTIONS
8.1
Conclusions
The objectives of this research were successfully achieved. A programmable Ushape xenon flashlamp driver circuit was successfully developed and tested.
Programmability is provided by a PIC16F84A microcontroller. The developed system
was divided into two stages, namely the implementation of software and the
implementation of hardware.
Generally, a basic flashlamp driver circuit, consist of a charging unit and a
triggering unit. In this study, an existing high voltage power supply was employed.
The function of this power supply is to charge up the capacitor banks. This high
voltage power supply was calibrated. Calibration is important in order to meet the
requirement DC voltage. In order to investigate and characterize the output of the
flashlamp, the capacitor values have been varied in the range of 2.24 µF to 13.44 µF.
This result changes in the input energy supply to the flashlamp.
85
Flashlamp itself has many applications. There are various methods are used to trigger
the flashlamp. These include external triggering, simmer and pseudo-simmer triggering
and overvoltage triggering. However, in this experiment a series injection triggering
method was chosen. The reason is because it is simple, safety, offers reliable and
reproducible performance especially for preliminary study. The triggering circuit was
divided into two parts. One is low voltage part which comprises of control circuit or
PIC16F84A circuit. While for high voltage part, it comprises of SCR and mixer circuit.
Isolation between low voltage and high voltage part is provided by a 1:1 isolation pulse
transformer.
The breakdown of the xenon gas in the flashlamp is induced by summing a
narrow 82.14 µs pulsewidth of 740 V from triggering circuit with 2.0 kV DC voltage
from charging unit. When this energy is released it yields highly excited xenon plasma
within the flashlamp. During this time, current through the flashlamp increases rapidly
and the voltage across the flashlamp falls drastically. As a result intense optical
radiation is emitted.
The peak current and the peak power during the discharge time of the flashlamp
were calculated using the fundamental equation of I=V/R and P=IV. Both peak current
and peak power were dependent on the input energy. The current waveform of the
flashlamp was detected by Rogowski coil as a pulse current transformer. The damping
or ringing signal is caused by several factors, such as the inductance and capacitance in
the circuit.
Two- and three- dimensional image of xenon flashlamp output from the
developed system were observed using Beam Star CCD Laser Beam Profiler. The
three-dimensional profiles are distributed in the form of Gaussian distribution. These
Gaussian profiles illustrate the intensity level distribution of the plasma spectral
gradient. Generally, the dimensions and plasma profiles are varying with the input
energy. The spot area of xenon flashlamp output was measured regarding it two-
86
dimensional, which then analyzed by Video Test 5.0 software. In general, the
flashlamp outputs are dependent on input energy.
The flashlamp output curve was detected using IPL10050 photodiode. The
bandwidth of the flashlamp pulse at FWHM and the amplitud of light were observed.
The diagnosed results indicated that, the pulsewidth of the flashlamp output at FWHM
is linear with the input energy. Similarly, the amplitude of flashlight detected from
photodiode also found linearly increses with input energy.
8.2
Problem and Suggestion
During this study, several problems are observed. The main problem is with the
tuning circuit for the SCR. According to the characteristic of the SCR in DC circuit, the
anode voltage remains positive with respect to the cathode. The only way anode current
can be reduced is by opening the line switch. So, we need a resonant or tune circuit in
order to force the SCR to switch off. The combination of RLC circuit must be preset,
otherwise the SCR will never switch off.
At the initial experiment, the SCR was damaged after triggering because of large
current surge. To overcome this problem, limiting resistors and free-wheeling diodes
are connected in parallel with secondary winding of series injection transformer. In
addition, free-wheeling diodes are also connected across anode and cathode of the SCR.
The other problem is to detect the waveform of the flashlight. As mention
earlier, the flashlamp output is too bright and scattered. The full waveform cannot be
captured because the detected output is limited by the input voltage i.e. 9 V. In order to
detect the full waveform two types of filter were employed, namely FSQOD200 and
03FIV038. Another related problem is the flashlight profile recorded by CCD
87
BeamStar was also saturated. To get the ideal profiles, the CCD BeamStar assembly
was placed at ~5 degrees from the flashlamp sources. A optical spectrum analyzer can
also be introduced to test the spectral emission of the xenon flashlamp.
As mentioned earlier, this research is a preliminary study for developing a
flashlamp driver for optical pumping. In this study, PIC16F84A was used as pulse
generator. For future works, it is suggested that other PIC microcontroller such as
PIC16F870 or PIC16F873 to be used. This is because these microcontrollers have more
flash program memory and PWM module that can be used for developing switching
power supply. Switching mode power supply has advantage of offering low cost, high
efficiency and compact in design (Sari, 1993).
Generally, there are many methods to trigger the flashlamp. In the present
study, the designed flashlamp driver circuit employs a series injection triggering
method. For future works, it is suggested that simmer triggering method can be used.
The main advantage of this method is that the flashlamp is only required to be triggered
once when switched on. Besides, the lifetime of the flashlamp can be increased. This
technique also requires lower voltage instead of high voltage involved in this research.
A linear flashlamp can be also employed to use as pumping sources for laser materials.
The results from this study will be beneficial for future researchers. The
problems described and the idea suggested will lead to a better understanding and inject
interests to carry on further study. Hopefully, this thesis will be a good reference and be
fully utilized for future works.
88
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Z.Sari, K.Amgoud and M. Ait-Bouabdallah (1993). Design And Implementation Of A
Microprocessor Based High Frequency Switching Mode Power Supply. Proceeding
of Fifth European Conference on Power Electronics & Application. Sept. 13 – 16,
1993. Inelec, Algeria: IEEE, 334-337.
93
APPENDIX A
List of home site used to install YAPPA programming.
1.
http://www.cm.ph.bham.ac.uk/software/yappa
2.
https://sourceforge.net/project/showfiles.php?group.
94
APPENDIX B
95
APPENDIX C
Assembly language program for programmable flashlamp driver
list
p=16f84
-CP_ALL
_CP_OFF
_DEBUG_ON
_DEBUG_OFF
_WRT_ENABLE_ON
_WRT_ENABLE_OFF
_CPD_ON
_CPD_OFF
_LVP_ON
_LVP_OFF
_BODEN_ON
_BODEN_OFF
_PWRTE_OFF
_PWRTE_ON
_WDT_ON
_WDT_OFF
_LP_OSC
_XT_OSC
_HS_OSC
_RC_OSC
pcl
status
porta
portb
cntmsec
msgptr
txreg
rxreg
bits
menu1
menu2
equ
equ
equ
equ
equ
equ
equ
equ
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
EQU
0x02
equ
0x05
0x06
equ
equ
0x0e
0x0f
0x10
0x31
0x32
H'0FCF'
H'3FFF'
H'37FF'
H'3FFF'
H'3FFF'
H'3DFF'
H'3EFF'
H'3FFF'
H'3FFF'
H'3F7F'
H'3FFF'
H'3FBF'
H'3FFF'
H'3FF7'
H'3FFF'
H'3FFB'
H'3FFC'
H'3FFD'
H'3FFE'
H'3FFF'
0x03
0x0c
0x0d
__CONFIG _CPD_OFF & _CP_OFF & _BODEN_OFF &
_XT_OSC
bsf
movlw
movwf
movlw
movwf
status,
0xfe
porta
0x00
portb
0x05
_PWRTE_OFF & _WDT_OFF &
96
bcf
bsf
movlw
call
movlw
movwf
call
movlw
call
call
clrf
status,
porta,
0x32
nmsec
0x00
rxreg
inmsg
0x00
outmsg
prompt
rxreg
menu
call
call
call
movf
bsf
andwf
btfss
goto
call
goto
inmsg
keyecho
prompt
menu1,
0
status, 0x02
rxreg
status,
0x02
menu
spulse
menu
nmsec
msecloop
movwf
movlw
call
nop
nop
decfsz
goto
return
cntmsec
0xf8
micro4
movlw
movwf
btfsc
goto
movlw
call
btfsc
goto
movlw
call
bsf
btfss
bcf
rrf
decfsz
goto
return
movf
call
movlw
call
movlw
call
return
0x08
bits
porta,
pc
0x13
micro4
porta, 0x01
pc
0x31
micro4
status,
porta,
status,
rxreg,
bits,
rxloop
inmsg
pc
rxloop
keyecho
0x05
0x00
;Get any message prom PC
;Print main menu
;Print pic> prompt
cntmsec, 1
msecloop
rxreg,
outch
0x0d
outch
0x0a
outch
0x01
0
0x01
0
1
1
0
97
prompt
movlw
call
movlw
call
movlw
call
movlw
call
return
0x70
outch
0x69
outch
0x63
outch
0x3e
outch
outmsg
msgloop
movwf
movf
call
addlw
btfsc
return
call
incf
goto
msgptr
msgptr,
msgtext
0x00
status,
movwf
movlw
movwf
bcf
movlw
call
rrf
btfsc
goto
bcf
goto
bsf
nop
decfsz
goto
movlw
call
bsf
movlw
call
return
txreg
0x08
bits
porta,
0x31
micro4
txreg,
status,
clrbit
porta,
testdone
porta,
outch
txloop
clrbit
testdone
msgtext
addwf
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
outch
msgptr,
msgloop
bits, 1
txloop
0x34
micro4
porta,
0x68
micro4
pcl,
0x0d
0x0a
'P'
'r'
'o'
'g'
'r'
'a'
'm'
'm'
'a'
'b'
'l'
'e'
1
0
0x02
1
0x00
1
0x00
0x00
0x00
0x00
98
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
0x20
'P'
'u'
'l'
's'
'e'
0x20
'M'
'e'
'n'
'u'
0x0d
0x0a
0x0d
0x0a
'P'
'r'
'e'
's'
's'
0x20
'('
'1'
0x20
'o'
'r'
0x20
'2'
0x20
')'
0x0d
0x0a
'1'
'.'
0x20
'S'
'i'
'n'
'g'
'l'
'e'
0x0d
0x0a
'2'
'.'
0x20
'R'
'e'
'p'
'e'
't'
'i'
't'
'i'
'v'
'e'
0x0d
99
micro4
spulse
retlw
retlw
retlw
retlw
0x0a
0x0d
0x0a
0x00
addlw
btfss
goto
return
0xff
status,
micro4
bsf
portb,
bcf
portb,
return
end
0x00
0x00
0x02
100
PUBLICATIONS
1. Asmawati @ Fatin Najihah Alias, Johari Adnan and Noriah Bidin,
Microcontroller Based Pulse Generator For Flashlamp Driver, Proceeding of
Annual Fundamental Sciences Seminar 2004 (AFSS2004), 14-15 June 2004,
Inst. Ibn Sina, Skudai Johor
2. Johari Adnan, Asmawati @ Fatin Najihah Alias, Ahmad Hadi Ali, Mohd Fairuz
Jani and Noriah Bidin, Programmable Xenon Flashlamp Driver Circuit,
Industrial Art & Technology Exibition 2004 (INATEX 2004), 6-8 July 2004,
Universiti Teknologi Malaysia (UTM), Skudai, Johor.
3. Asmawati @ Fatin Najihah Alias, Johari Adnan, Ahmad Hadi Ali, Mohd Fairuz
Jani and Noriah Bidin, Programmable High Voltage Pulse Circuit For Xenon
Flashlamp, Proceeding of Persidangan Fizik Kebangsaan (PERFIK 2004), 5-7
October 2004, Seri Kembangan, Selangor.
4. Asmawati @ Fatin Najihah Alias, Johari Adnan, Ahmad Hadi Ali, Mohd Fairuz
Jani and Noriah Bidin, Development of A Programmable Flashlamp Circuit For
Optical Pumping, Proceeding of The XXI Regional Conference and Workshop
on Solid State Science & Technology (RCWSST 2004), 10-13 October 2004,
Kota Kinabalu, Sabah.