BSc thesis full document

PCB Machine Graduation Project 2006

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Table of contents TABLE OF CONTENTS ............................................................................................................................. 1 ABSTRACT .................................................................................................................................................. 4 PROJECT OBJECTIVES ........................................................................................................................... 6 CHAPTER 1: ................................................................................................................................................ 7 INTRODUCTION TO MECHATRONICS AND PCB............................................................................. 7

1.1 MECHATRONICS: ........................................................................................................................ 8 1.1.1 What is Mechatronics? .......................................................................................................... 8 1.1.2 Key Elements of Mechatronics .............................................................................................. 9 1.1.3 Historical Development and Definition of Mechatronic Systems .......................................10 1.1.4 Mechatronic Design Approach.............................................................................................12 1.1.5 Mechatronic system configuration.......................................................................................13

1.2 INTRODUCTION TO PCB TECHNOLOGY: ..................................................................................14 1.2.1 Introduction: .........................................................................................................................14 1.2.2 Early History of the Industry................................................................................................15 1.2.3 Printed Circuit Applications .................................................................................................16 1.2.4 Types of PCBs .......................................................................................................................16 1.2.5 Where and How PCBs are used ...........................................................................................17 1.2.6 Basic PCB Elements .............................................................................................................18

CHAPTER 2: ...............................................................................................................................................19 THE MECHANICAL HARDWARE OF THE PCB MACHINE ...........................................................19

2.1 SYSTEM OVERVIEW ...................................................................................................................20 2.1.1 First module: Etching Mechanical Hardware.....................................................................21 2.1.2 Second module: PCB Drilling ..............................................................................................21 2.1.3 Lead – screw mechanism ....................................................................................................22

2.2 FIRST MODULE: ETCHING MECHANICAL HARDWARE:.............................................................23 2.2.1 Introduction: .........................................................................................................................23 2.2.2 The arm construction: ..........................................................................................................24 2.2.3 The basin construction: ........................................................................................................25 2.2.4 The frame construction: .......................................................................................................26

2.3 SECOND MODULE:......................................................................................................................35 2.3.1 Design approach ...................................................................................................................35 2.3.2 Modification for x-y table:....................................................................................................36 2.3.3 The X &Y axes: .....................................................................................................................37

CHAPTER 3: ...............................................................................................................................................39 ULTRA VIOLET PRINTING AND CHEMICAL ETCHING ...............................................................39

3.1 METHODS OF PRINTING ART WORK OR PCB............................................................................40 2.3.1 Silk screen .............................................................................................................................40 2.3.2 Direct printing.......................................................................................................................41 3.1.3 UV printing ...........................................................................................................................46

3.2 DEVELOPING:.............................................................................................................................58 3.2.1 Using of SODIUM HYDROXIDE: ......................................................................................58

3.3 ETCHING:...................................................................................................................................59 3.3.1 Using of FeCl3:.....................................................................................................................60 3.3.2 Notes about etching: .............................................................................................................61

3.4 TRAILS .......................................................................................................................................62 3.4.1 Normal PCB with spray ........................................................................................................62 3.4.2 Photo sensitive PCB:........................................................................................................65

3.5 BASIN COATING: ........................................................................................................................67


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3.5.1 Why?......................................................................................................................................67 3.5.2 Alternatives to avoid corrosion:............................................................................................68 3.5.3 The optimal solution: .......................................................................................................70

3.6 DEVELOPMENT: .........................................................................................................................70 3.6.1 Developing: ...........................................................................................................................70 3.6.2 PCB Manufacturing Facilities (future work) ......................................................................71

CHAPTER 4: ...............................................................................................................................................73 PCB M/C ELECTRICAL AND ELECTRONICS H/W ..........................................................................73 ACTUATORS & SENSORS ......................................................................................................................73

4.1 SECTION (1): PCB M/C ELECTRICAL AND ELECTRONICS H/W..............................................74 4.1.1 H-Bridge Circuit:..................................................................................................................74 4.1.2 OP-Amp feed back circuit: ...................................................................................................79 4.1.3 Debouncing circuit: ..............................................................................................................82

4.2 SECTION (2): ACTUATORS & SENSORS .....................................................................................84 4.2.1 Actuators:..............................................................................................................................84 4.2.2 Sensors: .................................................................................................................................89

CHAPTER 5: ...............................................................................................................................................92 PCB M/C PROGRAMMING & S/W ........................................................................................................92

5.1 INTRODUCTION:.........................................................................................................................93 5.1.1 What is a Microcontroller?...................................................................................................93 5.1.2 Where are Microcontrollers used? .......................................................................................94 5.1.3 General-purpose microprocessor: ........................................................................................95 5.1.4 Microcontroller .....................................................................................................................96 5.1.5 Microprocessor v.s. Microcontroller ....................................................................................96 5.1.6 Embedded System .................................................................................................................96 5.1.7 Three criteria in Choosing a Microcontroller .....................................................................97 5.1.8 Inside Architecture of AT90s8515........................................................................................97 5.1.9 Micro-Controller (AT90S8515) specs: .................................................................................98

5.2 FIRST MODULE:.........................................................................................................................99 5.2.1 States: ....................................................................................................................................99 5.2.2 Flowchart:...........................................................................................................................102 5.2.3 Micro-controller Program Code: .......................................................................................108

5.3 SECOND MODULE: ...................................................................................................................120 5.3.1 CAD CAM system: ..............................................................................................................120 5.3.2 flowchart: ............................................................................................................................121 5.3.3 Matlab Program code: ........................................................................................................122 5.3.4 Micro-controller flowchart:................................................................................................124 5.3.5 Micro-controller program: .................................................................................................125

CONCLUSION..........................................................................................................................................130 REFERENCES ..........................................................................................................................................131


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Acknowledgement We would like to express our gratitude and thanks to our supervisors: Prof. Dr. Farid A. Tolba, Prof. Dr. Magdy M. Abd El-Hameed, Eng. Mohamed Ibrahim Awad For their sincere guidance, supervision, support and encouragement. We would also like to thank the technicians of the workshop and Automatic control laboratory, of the Faculty of Engineering, Ain Shams University, for their valuable support and help. Finally, we dedicate our special thanks to our families, our parents and friends, who have always encouraged us along our way.


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Abstract This report presents the work performed for the B.Sc project for the year 2006 in Mechanical Engineering Department, Mechatronics section. The project includes the design and construction of a simple atomized PCB Machine, herewith providing a link between the mechanical hardware of it and the control algorithm that is to satisfy the desired function, as an example of Mechatronics. Mechatronics is a blend of mechanics and electronics, which utilizes precision engineering, control theory, computer science, and sensors and actuators technology to design improved products and processes. During this work, use has been made of Microcontroller and Personal Computer based Controllers (PCs). The project presents our knowledge acquired throughout the past five years of study at the Faculty of Engineering; Ain shams University, in different fields, such as Mechanical Design, Production Engineering, Electrical Engineering, Programming languages and Electronics.


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Introduction

A PCB is a key element in any modern electronic circuit. It is often the only component uniquely designed for the product. As technology has progressed over the last 50 years, the PCB, or PCA, has gone from being a simple, manually laid out, connection platform to being a complex and sophisticated computer-designed product in itself.

The PCB designer must be familiar with not only the concepts of board design, but with all the ancillary elements of other related engineering disciplines as well. These embody mechanical, electrical, chemical, thermal and material engineering principles. Thus the designer should be involved with the process from the concept to its final manufacture. They should work closely with all staff and must ensure that the PCB meets all the specifications that would be expected of the product.

The layout of the board must be done with due consideration being given too many different factors, e.g. component spacing, complexity of routing, track size requirements etc.

Documentation must be produced which meets the necessary standards and can be understood by all of those involved. The final documentation sent to the specialist PCB manufacturer is the designer’s responsibility, both to ensure its correctness and the formats being used.

Complex boards must be designed in an appropriate time span, given that a new design makes most of its profit in its first six months of release (before the competitors can catch up), any reduction in the time-to-market for the product will increase profitability. CAD software is used to ease the tasks of the PCB designer.

However, it must be remembered that the usage of such CAD tools are only an aid to product realization and considerable skill is still required by the PCB designer to maximize the efficiency of the process and produce a reliable, cost-effective and manufacturable board.


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Project Objectives

The main objective of the project is to design and construct two modules of PCB production line and perform control system on it. The design and implementation of the project includes the following steps:

• Acquiring knowledge about the world of PCB technology which is not highly exists in our industry.

• Design and construction of the mechanical system of the vending machine, which is divided into an etching system and a drill system.

• Design and preparation of the electrical and electronic circuits. • Proper selection and purchase of sensing elements and actuators. • The use of the Micro-Controllers to obtain the required function of the

systems through software programming. • The use of computer based programming languages. • Testing the system and comparing the actual product with the desired

product. Hence, the main objective of this project is to design and construct automated modules of PCB production line as an example of Mechatronic systems.


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Chapter 1: Introduction to Mechatronics and PCB


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1.1 Mechatronics: 1.1.1 What is Mechatronics? Mechatronics is a natural stage in the evolutionary process of modern engineering design. The development of the computer, and then the microcomputer, embedded computers, and associated information technologies and software advances, made Mechatronics an imperative in the latter part of the twentieth century. . Mechatronics is nothing new; it is simply the application of the latest techniques in precision mechanical engineering, controls theory, computer science, and electronics to the design process to create more functional and adaptable products. This, of course, is something many forward-thinking designers and engineers have been doing for years. The vaguely awkward word was first coined in Japan some 30 years ago. Since then, Mechatronics has come to denote a synergistic blend of mechanics and electronics. The word's meaning is somewhat broader than the traditional term electro-mechanics, which too many denotes the use of electrostatic or electromagnetic devices. The science of Mechatronics has been defined, by Takashi Yamaguchi (Hitachi Ltd.'s Mechanical Engineering Laboratory in Ibaraki, Japan), as "a methodology for designing products that exhibit fast, precise performance. These characteristics can be achieved by considering not only the mechanical design but also the use of servo controls, sensors, and electronics." He also added "Disk drives are required to provide very fast access, precise positioning, as well as robustness against various disturbances". Others defined Mechatronics as "the confluence of traditional design methods with sensors and instrumentation technology, drive and actuator technology, embedded real-time microprocessor systems, and real-time software."


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1.1.2 Key Elements of Mechatronics The study of Mechatronic systems can be divided into the following areas of specialty: 1. Physical Systems Modeling 2. Sensors and Actuators 3. Signals and Systems 4. Computers and Logic Systems 5. Software and Data Acquisition The key elements of Mechatronics are illustrated in next figure as the field of Mechatronics continues to mature; the list of relevant topics associated with the area will most certainly expand and evolve.

Figure (1-1): key elements of Mechatronics.


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1.1.3 Historical Development and Definition of Mechatronic Systems

Figure (1-2): History of Mechatronics.


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Figure (1-3): Mechatronics Components.


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1.1.4 Mechatronic Design Approach Steps in the Design of Mechatronic Systems

Figure (1-4): Mechatronics design approach.


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1.1.5 Mechatronic system configuration

Figure (1-5): Block diagram of Mechatronic system. Figure (1-5) shows the general configuration of a computerized Mechatronic system, where computer with a built in card is connected to the external equipment (sensors and actuators). This card is used as data acquisition and control card.

Table (1-1): elements of a Mechatronic system.


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1.2 Introduction to PCB Technology: 1.2.1 Introduction:

Although many categories of electronic product exist, this unit focuses on products that involve Printed Circuit/Wiring Boards or Assemblies (PCBs/PWBs or PCAs). The terms PCB, PWB and PCA are used extensively throughout the electronic industry and in academia. Strictly speaking, a PCB or PWB refers to the bare unpopulated board (i.e. without components), whilst PCA is used properly to describe an interconnection platform or board that has completed all stages of manufacture (i.e. components installed and all tests and build operations complete). However, although the terms are often used synonymously, they will, as far as possible, be applied as intended within the context of this text.

The aim of the electronic manufacturing industry has long been to achieve a reliable circuit design with repeatable electrical characteristics, good mechanical properties and to be of an acceptable appearance. Up until the 1950s, electrical/electronic circuits and systems were assembled using individual wires to connect each of the components. The components were then mounted on what were known as tag strips and sockets.

In response to the needs of the consumer for repeatable performance, smaller sizes and above all lower costs, it was necessary to develop assembly schemes that would allow for greater manufacturing efficiency. One method that proved very successful was the use of printed circuit boards to provide the contact between components. These were made from a laminate of an insulating material and were typically about 1.6 mm thick. One side had a layer of copper foil fixed onto it.

The foil was then selectively removed to leave a pattern that interconnected the components in the desired manner. Holes were then drilled through the laminate material to enable components to be fixed to the non-copper side. The components had flexible leads as their connection points and these were passed through the laminate. Electrical (and mechanical) connection was achieved by soldering these to the remaining foil. The foil provided the required electrical connection between the components.

The process met the needs of volume manufacture in that it could be relatively easily automated and created a final product which gave repeatable electrical performance and had sound mechanical strength.


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1.2.2 Early History of the Industry

Dr. Paul Eisler, an Austrian scientist, is given credit for developing the first printed wiring board. After World War II, he was working in England on a concept to replace radio tube wiring, as shown in Figure 2, with something less bulky. What he developed is similar to a single-sided printed wiring board.

Figure (1-6): Five-Valve Radio Internals

Figure (1-7): World PCB Market Share


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1.2.3 Printed Circuit Applications

It is important that future designers should have an appreciation for the broad variety of systems and products that employ PCBs. There is also a need to understand how these systems and products will be used and the environments in which they will function.

An effective design will result in a PCB that performs effectively and reliably throughout the product's life cycle, which encompasses fabrication, assembly, test, storage, transportation, and operation. During its life, a PCB may be required to survive exposure to a wide range of environmental conditions, such as temperature extremes, humidity, mechanical shock and vibration, atmospheric variations, harmful chemicals, and electromagnetic radiation.

Other major design influences and constraints related to a PCBs application include:

• Manufacturing cost. • Time to market. • Access for testing, adjustment, replacement and repairs. • Size and weight. • Reliability. • Availability of parts and materials.

1.2.4 Types of PCBs

Printed circuit assemblies are classified in a variety of ways:

• By type of circuitry used (digital, analogue, mixed analogue-digital, radio frequency, microwave)

• By types of electronic components used and how they are mounted (through-hole, surface-mount, mixed-technology, components mounted on one side or both sides)

• By board construction (single-sided, double-sided, multilayer, flex, rigid-flex, strip-line)

• By application and performance required (general electronic products, high-performance, dedicated service products, high-reliability products)

• By design complexity, circuit density, and manufacturability (low, moderate, high)


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Most PCBs incorporate electronic components and interconnections that perform specific circuit functions.

Some, however, simply serve as system-level interconnections, such as connector motherboards, or flex-circuit wiring harnesses. Printed circuit technology is also being used increasingly to produce integrated electronic components such as multi-chip modules (MCMS) and microwave integrated circuit (MIC) modules. Figure 4 shows several examples of some of the more common types of PCBs.

1.2.5 Where and How PCBs are used

Standards developed by the Institute for Interconnecting and Packaging Electronic Circuits (IPC) identify the following three classes of electronic products in which PCBs are used:

• Class 1. General products, including consumer items, computers and peripherals, and some military systems

• Class 2. Dedicated service products, including communication equipment business machinery, industrial controls, instruments, and military systems, where extended life and reliable service is needed

• Class 3. High-reliability products, including equipment and systems where continuous performance or performance on demand is essential

The basic intended functions of a printed circuit board are to support and interconnect electronic components. For most applications, these functions are required to be performed reliably, consistently, and as cost-effectively as possible. As indicated previously, circuit boards have evolved from being simple, passive parts of an electronic assembly to becoming an active circuit element whose design has a major effect on the performance of a product.

PCBs serve as key hardware building blocks for products found in all segments of the electronics market. The two largest areas of application (in terms of hardware cost/sale value) are communications equipment and computer systems. Other significant PGA utilization product areas include industrial controls, instrumentation, automotive, consumer, military/space and business/retail etc.

A substantial increase in the capabilities and application of digital circuitry [e.g. microprocessors, analogue-to-digital (A/D) converters, and digital signal processors] has resulted in an explosion of new electronic products


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using this technology. This has considerably expanded the need for complex, high-performance PCBs for use in games, mobile phones, cameras, video recorders, pagers, CD/DVD players, GPS devices and many other products.

In addition, functions previously performed by mechanical or electro- mechanical methods are rapidly being converted to pure electronic implementations. Two examples are appliance controllers and under-bonnet automotive sensors and controllers.

1.2.6 Basic PCB Elements

PCBs are commonly composed of a similar set of basic elements. These are:

1. A printed circuit board that supports the components and provides interconnections between them

2. Mechanical parts for mounting parts and hardware to the board, attaching the PCB to the system/product, providing thermal paths, and supporting and stiffening the assembly

3. Passive and active electronic components that perform the PCB's intended circuit functions

4. One or more connectors that are the electrical interface between the PCB and the rest of the system/product

The key elements of PCB manufacture, namely printed board creation (fabrication) and component insertion (assembly), may now be explored in some detail.


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Chapter 2: The Mechanical Hardware of the PCB Machine


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2.1 System overview Figure (2-1) shows the design of a simple PCB production line using ultraviolet printing method

Figure (2-1): Our PCB Machine.

Consists of two main modules:

Figure (2-2): system modules.


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2.1.1 First module: Etching Mechanical Hardware The target from that part is to have automatic printing and chemical etching before the drilling of the holes on the Board.

Figure (2-3): First module. 2.1.2 Second module: PCB Drilling

The target from that part is drilling of the holes on the Board.

Figure (2-4): Second module.


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2.1.3 Lead – screw mechanism The main mechanism used in the two stages is motors-lead screw combination to provide all axis movements.

Figure (2-5): Lead-screw. The shaft of the motors is coupled to lead screws. The screws are supported at two ends by Ball bearings. With this mechanism the rotational movement of the motors is converted to linear movements to drive the axis.

Lead – screw mechanism characteristic:

• Lead screws :convert rotary motion from a motor to linear motion

along the screw • Basically a screw and nut • Uses principle of a wedge to drive the nut • Lots of friction = low efficiency (30%) • Used in lots of machines – look at a lathe or milling machine

Figure (2-6): Screw Involved equation for the lead-screw:

⎥⎦⎤

⎢⎣⎡ ×

×=lead

TF πη 2

lead×= ων


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2.2 First module: Etching mechanical hardware: 2.2.1 Introduction:

This is the first part in our machine; the target from that part is to have automatic chemical etching before the drilling of the holes on the board. The idea of that mechanical part is an automated arm using screw- nut mechanism holding the board and move with it in different positions.

1. The position which the board is to be immersed in the Ferric chloride (FeCl3) basin,

2. The position of water basin for cleaning from the ferric chloride and sodium-hydroxide,

3. The position for the developer sodium-hydroxide (NaOH) basin, 4. And the position under ultraviolet box.

Figure (2-7): First module


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The mechanical construction of it; is very simple and it mainly consists of: 2.2.2 The arm construction:

Figure (2-8): Arm.

2.2.2.1 Arm body. 2.2.2.2 Arm housing. 2.2.2.3 Arm screw. 2.2.2.4 Arm nut. 2.2.2.5 The bearing housing plates.


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2.2.3 The basin construction:

Figure (2-9): Basin.

2.2.3.1 The three basins. 2.2.3.2 The basins table. 2.2.3.3 The table holders. 2.2.3.4 The basins lifter. 2.2.3.5 The basin motor support. 2.2.3.6 The basin screw. 2.2.3.7 The basin nut. 2.2.3.8 The basin guides.


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2.2.4 The frame construction:

Figure (2-10): Frame.

2.2.4.1 The main frame body. 2.2.4.2 The frame plates. 2.2.4.3 The basins guides' holder. 2.2.4.4 The basin supports.


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Figure (2-11): First module parts.


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2.2.2.1 The arm body:

The arm body is the holder which holds the board to transmit it from one position to another it has been made from galvanized steel 2mm thickness to resist the chemical action of the Ferric chloride. Its size is (150mm) length and (100mm) width which is appropriate for a standard board size.

Figure (2-12): Arm body. 2.2.2.2 The arm housing:

Figure (2-13): Arm housing.

The arm housing is the shell which holds the screw nut mechanism in order to move the arm. It was made of black steel with thickness (3.5mm) which is coated with red ferric-oxide to resist oxidation that housing is (1160mm ) length, (80mm) width and its height can be controlled between the range of (350mm) as minimum value and (362mm) as maximum value we can control that height using open slots at the end of the arm housing legs.


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2.2.2.3 The arm screw:

Figure (2-14): Arm screw.

The main screw in that part its length is (690mm), its diameter is (14mm) with trapezoidal pitch equal (1mm). That screw is considered as the X direction of that part of the machine also that screw is responsible for conversion of the rotational motion of the arm motor to the arm nut using flexible coupling. The maximum used length of that screw indicates the stroke of that part the pitch of that screw doesn't have to be very small as we didn't need high accuracy at that part as its function is just to handle the board from one position to another.

2.2.2.4 The arm nut:

Figure (2-15): Arm nut.

This nut is used to convert the rotational motion of the motor to linear motion; also the arm body is fixed to it in order to move along the arm housing. That nut had been made from (St.34) as a cube with length (60mm).


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2.2.2.5 The bearing housing plates:

In order to rotate the screw with negligible friction we used bearing with internal diameter (12mm) and outer diameter (24mm) and its capacity is (250 tons) so we made two housing plates attached to the both ends of the arm housing, these plates were made from St. 34 with length (80mm) and width of (60mm) and thickness of (8mm).

Figure (2-16): Housing plates.

2.2.3.1 The three basins:

Figure (2-17): Basins.

The three basins have been made from galvanized steel 1.5mm thickness. We coated it with plastic coating to resist the corrosion action due to the Ferric chloride (FeCl3) and the developer sodium-hydroxide (NaOH). The target of these basins is to hold the Ferric chloride (FeCl3) and the developer sodium-hydroxide (NaOH) and the water in order to immerse the board in it with the required sequence which serves our target. The three basins are identical, each of height (80mm) and length (172mm).


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2.2.3.2 The basin table:

Figure (2-18): Basin table.

The basin table is that table which holds the three basins. We had made it from black steel sheets with thickness (3mm), length (360mm) and width (172mm). 2.2.3.3 The table holder: In order to fix the table in the basin nut we use four right angle sheets each one on the side of the basin nut we made them from black steel sheets (2.5mm). They were attached to the nut using bolts (M6) and have been welded to the table.

Figure (2-19): Table holder. 2.2.3.4 The basin lifter: It seams like U shape part with flanged ends which is welded to the table and has a hole larger than the motor diameter to be able to move easily with the table without friction in the motor body. The usage of this part is to support the table as its heavy weight while holding the basins containing the liquids It was made from black steel sheets with thickness (2mm).

Figure (2-20): Basin lifter.


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2.2.3.5 The basin- motor support:

This support consists of two identical parts and both seems like inverted L section, each have a semi hole in its flat end with diameter less than the motor diameter as it would been assembled with the motor as shrink fit using bolts (M6) and leather washers to prevent the motor from rotation about itself, also we had made it from black steel sheets with thickness (2mm).

Figure (2-21): Basin motor support. 2.2.3.6 The basin screw:

This screw is considered as the Z direction of first module of the machine, also it is responsible about transmitting the rotational motion of arm motor to the arm nut using flexible coupling. The screw is (125mm) length and its diameter is (14mm) with trapezoidal pitch (1mm), the pitch of that screw don’t have to be very small as we didn't need high accuracy at that part as its function is just to rise the basin from one place to another.

Figure (2-22): Basin screw. 2.2.3.7 The basin nut:

This nut is the aid we had used to transform the rotational motion of the motor to linear motion also it has another important function that the table which hold the basin is attached to it in order to move along the screw. The nut had been made from (St.34) as a cube with length (60mm).

Figure (2-23): Basin nut.


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2.2.3.8 The basin guides:

Figure (2-24): Basin guides.

We have two guides as right angle pieces with height (300 mm), its function is to guide the table during stepping up or down in a straight way, and to prevent it from rotation about itself

2.2.4.1 The main frame body:

Figure (2-25): Frame body.

It’s the machine ground which holds all the Etching mechanical hardware to achieve fixation and absorption of some vibration coming from the basin and the moving arm. We used right angle piece and assembled them in rectangle from with dimensions (1200 mm * 610 mm).


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2.2.4.2 The frame plates: these are the plates which connect the main frame body with the two legs of the arm housing; and as we mentioned before we used open slots at the end of the arm housing legs in order of controlling the height of that part so the frame plates have open slots too in order to be attached with the arm housing and in the same time we weld it at the frame corners.

Figure (2-26): Frame plates. The open slot is (6mm) width and (85mm) length, and the plate’s dimensions are (135 *92mm) 2.2.4.3 The basin guides holders:

Figure (2-27): Basin guides holder.

These are the pieces which connect the main frame body with the basin motor support to fix the basin motor in the frame that part is two right angle pieces each of (300 mm) length and also have two open slots to enable us of moving the basin construction in transverse direction over the X direction. 2.2.4.4 The basin supports :- This part is two right angle pieces each of (300 mm) length and their function is to hold the basin guides.

Figure (2-28): Basin support.


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2.3 Second module: The target of this part is to drill holes on board. Mechanical system is the realization of 3-dimensional motion control. Motion Control-in electronics- means to accurately control the movement of an object based on speed, distance, load, inertia or a combination of all these factors. 2.3.1 Design approach

Although a number of people on the internet have built mills around other designs (i.e. using pipes, window frames, etc.) we decided to use a drill press and mill table for a number of reasons:

1) The 13" bench top drill press was chosen as it provided a cheap source for a number of parts, the head casting, from which the spindle would be made, a post for the head to traverse, sheaves (pulley), an electric motor and weight . 2) The milling table provides a heavy casting with a machined flat top surface, T-slots for clamps, dovetail slides with adjustable gabs, and a X & Y axis that are exactly 90 degrees apart. The function of the table during operation is to provide a solid and stiff structure to reduce any problems.

Figure (2-29): Drill design.


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This figure shows our PCB drilling machine which is the second stage in our project.

It consists of:

1- The driller. 2- X-Y table. 3- Vice. 4- Motors (dc geared motor – 2 servo

motors)

The dc geared motor is used to move the Z direction. And the two servo motors are used to move the X & Y directions of the table.

Figure (2-30): Drill.

2.3.2 Modification for x-y table: The main mechanism used is motors lead-screw combination to provide all axes movements. The shaft of the motors is coupled to the lead screws. The screws are supported at the two ends by Ball bearings. Using this mechanism the rotational motion of the motors is converted to linear motion to drive the axis.

Figure (2-31): Lead-screw.


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2.3.3 The X &Y axes: The main concepts commonly used to make a drilling device consist of a threaded travel mechanism, a combination X-axis and Y-axis, a precisely controlled motor, and a controller for the drilling mechanism to correctly position it. For each axis - X, Y, and Z – a motor is connected to the threaded travel mechanism. As the motor turns the screw-like device, a guide on top of the thread moved back and forth in a straight 1-dimensional line. Combining the X-axis and the Y-axis, an XY-plane is created. This allows a platform to be positioned anywhere in a 2-dimensional plane. The Z axis mounted separately above XY-plane which allows for a 3rd dimension.

Figure (2-32): Drill (Inventor).

A motor mount is attached to the table at the far end. On one end a servo motor is attached and the opposite end has a bearing block. The turned end of the lead screw is fitted into the bearings. The Y axis is constructed similar to the X axis. It is a simple idea we got in the movement of the X & the Y axis it is all depend on the movement of a nuts on a screw supported from its ends on ball bearings which are fixed on plates which in turn fixed on the frame.


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The X & Y axes are similar in its constructions its contents are:

1. Lead screw. 2. Nut. 3. Casing. 4. Supports. 5. Ball bearings. 6. Dc motors (for the automatic motion).

It is simply when we want the table to move automatically to the desired position in the X or Y axis we give a signal to the motor which in turn rotate its shaft then transmit the motion to the flexible coupling which make the screw work. Our nut is on the screw when the screw moves it moves in the X direction or in the Y direction according which motor we give the signal (the X or the Y motor)


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Chapter 3: Ultra Violet Printing and Chemical Etching


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3.1 Methods of printing art work or PCB 3.1.1 Silk screen 3.1.2 Direct printing 3.1.3 UV printing 2.3.1 Silk screen What Is Silk Screen Silk screen is also known as screen printing, silk-screening, and serigraphy. It is a process wherein a mesh material, like silk or nylon, is pulled taught over a frame to create a screen. A design is imprinted onto the screen and by blocking out parts of the image a stencil is created on the screen. The screen is set over an object and printing ink is poured near the top edge of the screen. Using a squeegee the ink is spread evenly across the screen, pushing it through the unblocked sections of the mesh and onto the object. The screen is removed revealing the single color image imprinted on the object. The process can be repeated using different screen stencils to add more color and detail to the print.


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2.3.2 Direct printing One way to put a pattern on the board is the direct draw approach. Using either a resist pen to draw your circuit, or by using printer (either inkjet or laser ones). Plotters also can be used for this target, and Specialty tapes (dry transfers). You layout your circuit traces directly onto the copper surface of the board. The pen technique relies on the water-proof nature of the ink and the tapes as an impervious plastic, both of which prevent the etchant from getting at the copper beneath, hence, all copper is etched away except for where the pattern has been drawn. This is the quickest way to get a circuit pattern on the board, plus, since the ink doesn't apply uniformly, there is a risk that the traces will be etched away since the etchant can get to the copper through an extremely thin layer of resist. If you make a mistake you have to start all over again! For these reason, you can use this method only to make very easy low-definition PCBs or to retouch a bit your PCB before etching. We thought to use a printer to print the circuit directly from the computer to

the copper layer of the board.

There were three flashing problems in our mind to use that idea:

1) The printer we will use should be horizontal to draw the paths and

eject it as the board is not rigid enough to be deflected into the printer

core.

2) The thickness of the board nearly equal twentieth time the thickness

of the paper so we should modify the printer to be able to pull the

board.

3) The type of the ink that we use should be suitable to be permanent on

the copper board surface during the chemical etching process.


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3.1.2.1 Plotter

Figure (3-1): Plotter.

To solve the first problem we try to use a horizontal plotter the plotter we use was Copam (pl-445) which we use it especially as the maximum paper size for that printer was A3 so it was small size which will serve us in our project but the problem in that plotter that it was stock one and we can't find the software to run that plotter over any windows almost it was working over DOS and no one from our group was expert in dealing with printers over DOS system so at that moment we have three another types of printers to use

1) Laser printer 2) DeskJet printer 3) dot-matrix

We try with the laser printer and dot-matrix printer and laser but it gives no satisfied results; due to the internal structure of those printer doesn't favor our target


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3.1.2.2 hp DeskJet 3325 printer

We select DeskJet printer (hp 3325) as

• it is available in the Egyptian market

• its software is easy to deal • its cost was suitable for us

But this printer wasn't flat paper drawing

Figure (3-2): hp3325 printer.

3.1.2.3 Horizontal modification:-

Figure (3-3): Horizontal modification. So the only way to overcome this problem is to modify the printer to become horizontal It wasn't easy to do this; but we had opened the backward shell of the printer frame and then break off some limit switch which indicate to the printer that some paper had been jammed At that moment the printer seems to be horizontal paper drawing


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3.1.2.4 The board thickness:-

The second problem was the most complicated problem and it was to modify the thickness that the printer can draw from the paper thickness almost (0.01 mm) to the board thickness which almost equal (1.75 mm) Many trials we had done but failed; the only effective one that we had changed. The spring which control the fans that slides the paper from the drum during the exiting or ejection of the paper with another spring with lower stiffness and for our luck that way has been succeeded now we modified the printer to be able to draw any flat board with thickness up to 1.75 mm and print any shape with any colors you want to print from your computer to the surface of any board, not only the PCB board but we had also print over a pieces of wood , plastic , glass , steel and any material.

Figure (3-4): Board during & after printing.


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3.1.2.5 The ink problem

This problem is tends to be a chemical problem rather than mechanical problem. The printer ink is been removed while etching. We tried to replace the ferric chloride with another chemical material: but it doesn't make the etching. This problem, we think is easy to be solved but with chemical engineering. So our research in this region has been terminated to save time. Important hint: That work we did had taken great effort and time and it gives favorable results which wasn't expected unless the ink problem which is related to chemical engineering. So we advise any one who works in that project to continue that work And he always will find us helping him.


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3.1.3 UV printing 3.1.3.1 Exposure

The photo-resist board needs to be exposed to ultra-violet light through the artwork, using a UV exposure unit.

UV exposure units can easily be made using standard fluorescent lamp and UV tubes. For small PCBs, two or four 8 watt 12" tubes will be adequate, for larger (A3) units, four 15" 15 watt tubes are ideal. To determine the tube to glass spacing, place a sheet of tracing paper on the glass and adjust the distance to get the most even light level over the surface of the paper. Even illumination is a lot easier to obtain with 4-tube units. The UV tubes you need are those sold either as replacements for UV exposure units, insect killers or 'black light' tubes for disco lighting etc

LAMP DETAILS

Figure (3-5): UV lamp.

They look white or occasionally black/blue when off, and light up with a light purple, which makes fluorescent paper etc. glow brightly. Do not use short-wave UV lamps like EPROM eraser tubes or germicidal lamps, which have clear glass - these emit short-wave UV which can cause eye and skin damage, and are not suitable for PCB exposure.

A timer which switches off the UV lamps automatically is essential, and should allow exposure times from 2 to 10 minutes in 30 second increments. It is very useful if the timer has an audible indication when the timing period has completed. A mechanical or electronic timer from a scrap microwave oven would be ideal.

Short-term eye exposure to the correct type of UV lamp is not harmful, but can cause discomfort, especially with bigger units. Use glass sheet rather


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than plastic for the top of the UV unit, as it will flex less and be less prone to scratches.

Figure (3-7): UV unit.

If you made up a combined unit, with switchable UV and white tubes, so it doubles as an exposure unit and a light-box for lining up double-sided artworks. If you do a lot of double-sided PCBs, it may be worth making a double-sided exposure unit, where the PCB can be sandwiched between two light sources to expose both sides simultaneously.

You will need to experiment to find the required exposure time for a particular UV unit and laminate type - expose a test piece in 30 second increments from 2 to 8 minutes, develop and use the time which gave the best image.

For a single-sided PCB, place the artwork, toner side up, on the UV box glass, peel off the protective film from the laminate, and place it sensitive side down on top of the artwork. The laminate must be pressed firmly down to ensure good contact all over the artwork, and this can be done either by placing weights on the back of the laminate, or by fitting the UV box with a hinged lid lined with foam rubber, which can be used to clamp the PCB and artwork.

To expose double-sided PCBs, print the solder side artwork as normal, and the component side mirrored. Place the two sheets together with the toner sides facing each other, and carefully line them up, checking all over the board area for correct alignment, using the holes in the pads as a guide. A light box is very handy here, but it can be done with daylight by holding the sheets on the surface of a window. If printing errors have caused slight miss-registration, align the sheets to 'average' the error across the whole PCB, to avoid breaking pad edges or tracks when drilling. When they are correctly aligned, staple the sheets together on two opposite sides (3 sides for big PCBs), about 10mm from the edge of the board, forming a sleeve or


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envelope. The gap between the board edge and staples is important to stop the paper distorting at the edge. Use the smallest stapler you can find, so the thickness of the staple is not much more than that of the PCB. Expose each side in turn, covering up the top side with a reasonably light-proof soft cover when exposing the underside - rubber mouse mats are ideal for this. Be very careful when turning the board over, to avoid the laminate slipping inside the artwork envelope and ruining the alignment.

After exposure, you can usually see a clear image of the pattern in the photosensitive.

3.1.3.2 DIY PCB Manufacturing

The basic PCB material used is photo-sensitive with a UV

You can also use non photo-sensitive PCB and treat it with Positiv20 spray from. De-oxidate and de-grease the raw PCB material with steel wool and aceton. Atomise a Fine layer of Positiv20 onto the copper and let the PCB dry for 24 hours in ambient room temperature, or about an hour at a maximum of 70°C (do not exceed!). Do this in hot air electric oven. The drying must be done in complete darkness! After that the PCB can be used as normal photo-sensitive PCB.

All you need is:

• Software to develop your PCB layouts. • (Preferably) A laser printer to print the darkest possible printouts of

your PCB layout on transparent slides.


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3.1.3.3 Exposure steps

First cut out the layout leaving a few millimeters of space on the edges. If you are going to perform the exposing and etching in the same session, go ahead and turn the etching machine on now, since it takes 10 minutes to warm up.

Figure (3-7): Cut the translucent paper, leaving at least a few mm

boarders The best PCBs are those that have a plastic sticky sheet protecting them (some are just sold in a plastic bag) so that they can be handled, drilled and sheared without excess UV exposure. The plastic is easy to peel off:

Figure (3-8): The underlying substrate should be a greenish color


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Figure (3-9): Circuit lay-out.

Figure (3-10): Some more pictures for UV-exposure units:


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Figure (3-11): The PIC16F84 based Timer & the 4 UV-lamps:

Figure (3-12): The used glass plate is "milky" to diffuse the UV-light from the lamps


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Figure (3-13): Placement of the PCB material and slides

Figure (3-14): Slides in place onto the glass plate (with toner upwards)


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Figure (3-15): PCB material in place onto the slides, ready to be exposed Once you think you're done exposing, lift off the design and put it away in case you want to make another set of boards. You are ready to perform the chemical processing. If you need to do these parts later, or you have other boards to expose, place this board in an opaque container.


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To determine the "best" exposure time for the UV exposure do the following:

1. Take a slide with a PCB layout. 2. Put a piece of cardboard on 9/10 of the surface. 3. Expose for 1 minute. 4. Move the cardboard to 8/10 of the surface. 5. Expose for 1 more minute. 6. Move the cardboard to 7/10 of the surface. 7. Expose for 1 more minute. And so on... 8. Develop the exposed PCB. 9. Examine the results and decide for the best exposure time.

Figure (3-16): UV exposure

The best exposure time is between 5 and 6 minutes


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3.1.3.4 Our UV exposure unit:

Figure (3-17): The UV unit with the hand in it.

Figure (3-18): The UV unit as a part of the system.


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3.1.3.5 HEALTH, SAFETY AND THE ENVIRONMENT

Today, more than at any other time in our history, man has become conscious of the environment, and is increasingly aware of the damage already done to it. Global warming, greenhouse effect, ozone depletion, photochemical smog, pollution and deforestation are now household terms.

Environmental protection agencies and governmental health and safety authorities operate in just about every industrialized country in the world. Governments and numerous non-government bodies are working locally, nationally and internationally to protect our health, our environment and the future of planet earth.

Health Effects

The biological effects of the 3 regions vary greatly as implied by the "hazard potential" column in the table. The health effects of exposure to UV light are familiar to anyone who has had sunburn. However, the UV light level around some UV equipment greatly exceeds the levels found in nature.

Acute (short-term) effects include redness or ulceration of the skin. At high levels of exposure, these burns can be serious. For chronic exposures, there is also a cumulative risk of harm. This risk depends upon the amount of exposure during your lifetime. The long-term risk for large cumulative exposure includes premature aging of the skin and even skin cancer.

The eyes are also susceptible to UV damage. Like the skin, the covering of the eye or the cornea, is epithelial tissue. The danger to the eye is enhanced by the fact that light can enter from all angles around the eye and not only in the direction you are looking. The lens can also be damaged, but since the cornea acts as a filter, the chances are reduced. This should not lessen the concern over lens damage however, because cataracts are the direct result of lens damage.

Burns to the eyes are usually more painful and serious than a burn to the skin. Make sure eye protection is appropriate for this work. There are specially-made safety glasses for the different UV ranges.


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Normal eyeglasses or contacts offer you very limited protection!!

The rest of the face must also be protected. Severe skin burns can happen in a very short time, especially under the chin (where most people forget to cover). Full-face shields are really the only appropriate protection when working with UV light boxes for more than a few seconds.

Be sure to protect arms and hands by wearing a long-sleeve lab coat and gloves.


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3.2 Developing: 3.2.1 Using of SODIUM HYDROXIDE: Keep clear of the fumes that are produced, they're heavily etching and really bad for your lungs! This is also why you should only use this method if it is possible to do outdoor. This solution will etch a PCB in 30 to 300 seconds, much faster than other processes. And the chemicals are - though very dangerous in concentrated form - not toxic to the environment if you flush it afterwards (in limited doses, that is - the removed copper is a little toxic).

When the board is fully developed all the unwanted copper will become bare and the wanted copper tracks will still remain covered with resist. Gentle finger pressure rubbed over the board will assist the removal of the unwanted resist as well as clearing out holes, text and other detail. Wash your hands immediately after this. The soda should be so weak that it will do no harm, but if allowed to evaporate then it could become a problem.


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3.3 Etching:

Ferric chloride always used as an etchant - it's a messy stuff, but easier to get and cheaper than most alternatives.

It attacks ANY metal including stainless steel, so when setting up a PCB etching area, use a plastic or ceramic sink, with plastic fittings & screws wherever possible, and seal any metal screw heads etc. with silicone-rubber sealant. If copper water pipes may get splashed or dripped-on, sleeve or cover them in plastic

You should always use the hexahydrate type of ferric chloride, which is light yellow, and comes as powder or granules, which should be dissolved in warm water until no more will dissolve. Adding a teaspoon of table salt helps to make the etchant clearer for easier inspection. Anhydrous ferric chloride is sometimes encountered, which is a dark green-brown crystalline powder. Avoid this stuff if at all possible Use extreme caution, as it creates a lot of heat when dissolved - always add the powder very slowly to water, do not add water to the powder, and use gloves and safety glasses.

If you're making PCBs in a professional environment, where time is money, you really should get a heated bubble-etch tank. With fresh hot ferric chloride, a PCB will etch in well under 5 minutes, compared to up to an hour without heat or agitation. Fast etching also produces better edge quality and consistent line widths.

If you aren't using a bubble tank, you need to agitate frequently to ensure even etching. Warm the etchant by putting the etching tray inside a larger tray filled with boiling water - you want the etchant to be at least 30-50؛C for sensible etch time.


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3.3.1 Using of FeCl3:

Etch rate can be very high but is dependant on solution movement over the

surface of the board and temperature, normal etching temperature is more

likely to be 45C. When etching circuits if up to 5% of HCL is added it,

increases etch rate, helps to stop staining, and reduces the risk of the solution

sludging. Ferric especially with extra HCL makes a very good stainless steel

etchant.

When Ferric crystals are mixed with water some free HCL produced through

hydrolysis.

FeCl3 + 3H2O > Fe(OH)3 + 3HCL

The basic etching reaction takes place in 3 stages.

First the ferric ion oxidizes copper to cuprous chloride, which is then further

oxidized to cupric chloride.

FeCl3 + Cu > FeCl2 + CuCl

FeCl3 + CuCl > FeCl2 + CuCl2

As the cupric chloride builds up at further reaction takes place,

CuCl2 + Cu > 2CuCl


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The etch rate quickly falls off after about 17oz/gallon (100g/l of copper has been etched. For a typical solution containing 5.3lb/gallon (530g/l) of ferric chloride. 3.3.2 Notes about etching:

• The concentration of the etchant acid (FeCl3) is very effective on

etching process, when we used 400 gm/liter the process was done in 15min. while when used 250gm/liter it took like 7hr without heating or stirring.

• The 250gm/liter concentration was enough when we used hand sprayed boards while it proved to be less than required when we were etching photo sensitive boards

• Constant heating the water is effective too; the water is getting cool with time passing, why? it was noticed that the etching process is relatively fast in the beginning and gets slower as the water loses heat to the environment (it's recommended to add a thermostat to keep the water at a certain level of heat )


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3.4 Trails 3.4.1 Normal PCB with spray First trial:

• Non-homogeneous. • Spent 4-hours under

florescent light. • Heavy spray. • At a non-particular

distances. • One min in NaOH. • 30 min in FeCl3. • Didn't give a result.

Figure (3-19): First trial.

Second trial:

• Homogeneous. • 5 hours under florescent

light. • Heavy spray. • At no particular distance. • Slightly appearing

printed tracks. • 40 sec in NaOH. • One hour in FeCl3.

Figure (3-20): Second trial.


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Third trial: Homogeneous. 4 hours under

florescent light. Sprayed at 20 cm

distance. One min in NaOH. 90 min. in Fecl3.

Figure (3-21): Third trial.

Fourth trial:

Medium spray 6 min under UV. Medium

homogeneity. Sprayed at no

particular distance. 20 sec. in NaOH. 45 min. in FeCl3.

Figure (3-22): Fourth trial.

Fifth trial:

Light spray. 12 min under UV. Slightly homogeneous. Sprayed at 20 cm distance. 60 sec in NaOH. No results to be put in

FeCl3. Figure (3-23): Fifth trial.


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Sixth trial:

Light spray. 7 min under UV. Good homogeneity. 10 sec. is NaOH. 10 min. in FeCl3 1 hour in FeCl3.

Figure (3-24): Sixth trial.


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3.4.2 Photo sensitive PCB: Trails of photo sensitive boards: First trail

• 18 min under UV.

• 40 sec in NaOH.

• 15 min in FeCl3.

Figure (3-25): First trial.

Second trails


• 10 sec in NaOH.

• 18 min in FeCl3

Figure (3-26): second trial.


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Third trail


• 30 sec in NaOH.

• 15 min in FeCl3.

Figure (3-27): Third trial.

Fourth trail


• 10 sec in NaOH.

Figure (3-28): Forth trial.


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3.5 Basin coating: 3.5.1 Why? Ferric chloride attacks basin material (steel), therefore, it is necessary to coat the basin with special coating to avoid corrosion occurrence.

Figure (3-29): Basin (steel) before interaction with FeCl3 Figure (3-30): Forth trial. Basin after attack of FeCl3, fully corroded after approx.9 hours without heating.


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3.5.2 Alternatives to avoid corrosion: 3.5.2.1 coating using red Ferro oxide(Fe2O3) Coating the steel with this type of coating gives inefficient results as shown in the following figure. Figure (3-31): The sample is coated with Fe2O3 is diluted with an organic solution (Tenar). The coating is dissolved due to the action of the heated ferric chloride (FeCl3) after 10 minutes approximately. . Figure (3-32): The sample is coated with concentrated Fe2O3 , it takes longer to be dissolved due to the action of the ferric chloride(FeCl3). The two samples give inefficient results. Therefore, this type of coating is inefficient.


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3.5.2.2 coating using plastic paint: Another alternative is to coat the basin with plastic paint to avoid corrosion. Plastic paint gives better results than Fe2O3, as shown in the following figure.

Figure (3-33): The sample after exposure to FeCl3 Disadvantages: After coating the basin(that made of steel) ,FeCl3 should be put in the basin just before proceeding the experiment by a specific time up to (maximum)one day to avoid corrosion occurrence.

Figure (3-34): Another photo for the sample.


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3.5.3 The optimal solution: When setting up a PCB etching area, use a plastic or ceramic sink, with plastic fittings & screws wherever possible, and seal any metal screw heads etc. with silicone-rubber sealant.

3.6 Development: 3.6.1 Developing:

The main thing to say here don’t use SODIUM HYDROXIDE for developing photo resist laminates. It is completely and utterly dreadful stuff for developing PCBs - apart from its causticity, it's very sensitive to both temperature and concentration, and made-up solution doesn't last long. Too weak and it doesn't develop at all, too strong and it strips all the resist off. It's almost impossible to get reliable and consistent results, especially so if making PCBs in an environment with large temperature variations (garage, shed etc), as is often the case for such messy activities as PCB making. A much better developer is a silicate based product, which comes as a liquid concentrate. They say it is sodium met silicate pent hydrate Na2SiO3*5H2O.

This stuff has huge advantages over sodium hydroxide, most importantly is very hard to over-develop. You can leave the board in for several times the normal developing time without noticeable degradation. This also means it's not temperature critical - no risk of stripping at warmer temperatures. Made-up solution also has a very long shelf-life, and lasts until it's used up - the concentrate lasts for at least a couple of years.

The lack of over-developing problems allows you to make the solution up really strong for very fast developing the recommended mix is 1 part developer to 9 parts water.


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3.6.2 PCB Manufacturing Facilities (future work)

Etching

This is the process which is more likely to be familiar to you. For each side of a PCB, a positive mask is produced on acetate film (i.e. black lines on the mask correspond to tracks on the finished PCB). Many PCB design systems allow you to produce these masks. They can also be produced manually in certain circumstances. The masks are placed on either side of a piece of blank PCB material that has been coated with a thin film of light-sensitive resist. After the board is exposed to a controlled level of ultraviolet light, areas of the resist can be washed away leaving other areas attached to the board. When the board is then immersed in an etch solution, copper can be removed from the board where it is not required and left where contacts are required. The process requires precise exposure times and good quality artwork (more on this later) and can produce reasonably good quality boards.

Advantages of etching include:

• It is easy to produce many boards at once • It can be very quick for a large design (both sides done at the same

time) • Can take artwork from all sorts of packages

Disadvantages include:

• Potentially harmful chemicals are used in the process • Quality is sometimes variable • Poor quality artwork produces poor quality boards • Not usually suitable for high-density designs • Drilling not part of the process

Figure (3-35): PCB Etch Process Tank


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Miller / Router

The miller/router is a PCB prototyping system. It allows very high quality prototype boards to be produced as "one-offs". Due to its nature it is not intended to be used to produce multiple copies of a board. In the manufacturing process a high-speed machine is used to mill the PCB. Board areas that are not required are removed during the milling process. Areas that are left form the pads and tracks of the design. The design file used by the machine follows an industry standard format called Gerber. Most good PCB packages allow this format to be generated

Advantages of the miller / router include:

• Excellent quality boards can be produced • Component and track density can be very high • Uses industry-standard design files • Component holes and mounting holes can be drilled on the same set-

up

Disadvantages include:

• It's technology-intensive and relatively expensive • It can be slow for complex boards • Multiple boards take correspondingly longer • Cost of tooling and hence PCB is high • Input files must be in Gerber format

Figure (3-36): The Miller / Router System


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CHAPTER 4: PCB M/C Electrical and Electronics H/W Actuators & Sensors


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4.1 Section (1): PCB M/C Electrical and Electronics H/W 4.1.1 H-Bridge Circuit: 4.1.1.1 H-Bridge Theory: Figure (4-1) shows the basic schematic for a typical H-Bridge along with its truth table. In order to make a motor turn, we need to apply a voltage to it. We do this by turning certain NPN transistors on. By looking at the truth table, we can see that in order to make a motor go forward (NOTE: ‘Forward and ‘Reverse’ are arbitrary directions for purposes of illustration. In your application, forward and reverse will be determined by how the motors are mounted with respect to each other and the polarity of the voltage) .we must turn on Q1 and Q4. This puts the Motor Battery Positive on the left side of the motor (through Q1) and grounds the other side of the motor (through Q4). To go in the opposite direction, we must turn off these transistors and turn on Q2 and Q3. Now, the Motor Battery Positive will be on the right side of the motor (through Q3) and ground is on the left (through Q2). You have now reversed the polarity of the motor’s supply voltage and the motor will spin in the opposite direction.

Figure (4-1): H-Bridge basic circuit.

You will notice that each time a motor is turned on; current passes through 2 NPN transistors. Each transistor has (approximately) 0.7 Volt drop across it, so the motor will see about 1.4 Volts LESS than the Motor Battery Voltage across its terminals. This means that if you have a 12 Volt motor, and you want it to receive maximum power, you should use a 13.4 Volt battery.


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Also notice that if transistors Q1 and Q2 (or Q3 and Q4) were turned on, that you would make a short circuit across the battery. For this reason, the L298N has internal logic that prevents this from happening. 4.1.1.2 L298 – Dual Full-Bridge Driver IC: The L298 is a high voltage, high current dual full-bridge driver designed to accept standard TTL logic levels and drive inductive loads such as relays, solenoids, DC and stepper motors. Two enable inputs are provided to enable or disable the device independently of the input signals. The emitters of the lower transistors of each bridge are connected together and the corresponding external terminal can be used for the connection of an external current sensing resistor. An additional supply input is provided so that the logic works at a lower voltage. The L298 has an operating supply voltage up to 46V. (I.e. High operating voltage means higher rotation speeds in a stepper motor.) It can handle 2A/Phase motor currents with a total DC current up to 4A (two phases). Figure (4-2) shows the block diagram of the L298 integrated circuit. See Appendix B for detailed information about L298 IC.

Figure (4-2): L298 IC Block diagram.


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The outputs (Out1-Out4) must be connected to DC motor coils by using external recirculation diodes to enable current paths for the motor windings. These diodes must be “Fast Recovery Diodes” with reverse recovery times smaller than 200ns to reduce switching noises during step changes. A typical DC motor driver designed with L298 IC can be seen in Figure(4-3)

Figure (4-3): Motor connection.


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For two phases we could use the following connection

Figure (4-4): Two phase connection.

4.1.1.3 H-Bridge specifications:

• Controls 2 DC Motors up to 2 Amps each Forward, Reverse, Stop. • Runs on 6 to 35 Volts DC. • Fully Isolates Motor Electricals from Microcontroller. • Easy to Assemble.


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4.1.1.4 Motor connection considerations: Motors are inductive devices; they draw much more current at startup than when they are running at a steady speed. Before connecting any motor to the L298 you should know a few things about the motor:

- What voltage it is designed to work at - How much current it draws when running (unloaded) - How much current it draws at stall.

The “stall current” is the current the motor draws when you stop (stall) the output shaft. 4.1.1.5 Heat Sinks: The L298 has internal thermal protection circuitry that shuts down the chip if it becomes too hot (when you try to draw too much current). If you find this happening, you should add some kind of heat sink to the L298. A simple heat sink can be made from a piece of scrap aluminum by cutting as big a piece as you have room for and drilling a 1/8” hole into it (for a bolt to hold it to the L298). Of course, you should always make sure that air can circulate freely around the L298 and its heat sink. NOTE: If a motor behaves erratically, turning on and off rapidly, it is likely the L298 senses that it is being overloaded. This usually means that you are drawing too much current. Either add a heat sink to the L298 and/or reduce the current being drawn. Caution: The L298’s heat sink (the metal tab) is at ground potential. Do not allow any ground-referenced voltage source to touch it or any heat sink connected to it, or you will cause a short.


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4.1.2 OP-Amp feed back circuit:

Figure (4-5): OP-Amp feed back circuit


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4.1.2.1 Absolute Maximum Parameters of the (uA741): Maximum means that the op-amp can safely tolerate the maximum ratings as given in the data section of such op-amp without the possibility of destroying it. The uA741 is a high performance operational amplifier with high open loop gain, internal compensation, high common mode range and exceptional temperature stability. The uA741 is short-circuit protected and allows for nulling of the offset voltage.

Table (4-1): Maximum ratings.

4.1.2.2 Summed-up Features: • Internal frequency compensation. • Short circuit protection. • Offset voltage null capability. • Excellent temperature stability. • High input voltage range. • NO latch-up.


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4.1.2.3 Electrical Ratings: Electrical characteristics for op-amps are usually specified for a certain (given) supply voltage and ambient temperature. Also, other factors may play an important role such as certain load and/or source resistance. In general, all parameters have a typical minimum/maximum value in most cases.

Figure (4-6): The two most common types are shown in the diagram on the right. Depending on the application, the 8-pin version is used the most, worldwide. Actually, there is a third type in the form of a metal-can but is obsolete and, by my knowledge, no longer used. I have two of these metal-can types and keep them as a 'gone-by' memory.

Figure (4-7): Internal 741 schematic of Fig. 3)

Figure (4-6)


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4.1.3 Debouncing circuit: Shown below is a push-button switch. It is spring loaded so that if you are not pushing it, the middle pin is connected to the side pin marked NC (Normally Connected). When the button is pushed, the middle sliding contact is pressed against the other side pin contact. If we connect one of the side pins to +5V and the other to GND and use the middle pin as a variable as we do in the toggle switches, we get the following output on the middle pin when the button is pushed:

Figure (4-8): Push-button. This timing diagram is blown up so the time scale is in milli-seconds. The switch does not produce a clean transition from one logic level to the other. Instead, it "bounces". Switch bounce has not been a problem in the combinational circuits that we have examined so far because the human eye cannot detect this bounce and it settles out in a matter of milli-seconds. When switches are used as clock inputs to flip-flops, however, it becomes a problem because when we intend to input a single pulse, we are instead inputting several pulses. In the case of a toggle flip-flop, for example, this can result in an indeterminate final state. This is a characteristic of ALL mechanical switches and cannot be eliminated in the design of the switch itself. We CAN, however, obtain a clean, "debounced" signal from the switch by adding a "debouncing circuit". This circuit consists simply of an S'R' latch. Examine the debouncing circuit shown below connected to the switch. Since the S'R' latch has 2 inputs, the side pins of the switch are now inputs rather than being connected directly to +5V or GND. The middle pin is connected to GND so that when the button is UP, the rightmost pin is connected to GND and the leftmost pin is connected to +5V. When the button is pressed down, the leftmost pin is connected to GND and the rightmost pin is connected to +5V. The resistors


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must be inserted so that +5V is never connected directly to GND. This direct connection tends to ruin power supplies.

Figure (4-9): Push-button.

The timing diagram for the bouncing switch outputs is given. Keeping in mind the characteristic table of the SR latch, fill in the outputs, Q and Q'. Make sure you understand why the outputs are not bouncy like the inputs.


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4.2 Section (2): Actuators & Sensors 4.2.1 Actuators:

i. DC –Motor.

ii. Servo Motor.

4.2.1.1 DC-Motor 4.2.1.1.1 Why choose a D.C. motor? Many applications call for a high start-up torque. The D.C. motor, by its very nature, has a high torque vs. falling speed characteristic and this enables it to deal with high starting torques and to absorb sudden rises in load easily. The speed of the motor adjusts to the load. Furthermore, the D.C. Motor is an ideal way of achieving the efficiency designers are constantly seeking for, because the efficiency it gives is high compared with other designs. 4.2.1.1.2 Composition of a D.C. motor

Figure (4-10): Inside the DC motor.

The stator is formed by a metal shell and one or more magnets that create a permanent magnetic field inside the stator. At the rear of the stator are the brush mountings and the brush gear which provide electrical contact with the rotor.


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The rotor is itself formed by a metal shell carrying coils which are interconnected at the commutator at the rear of the rotor. The commutator and brush assembly then select the coil through which the electric current passes in the opposite direction. 4.2.1.1.3 Principle of operation: Whatever the complexity of the rotor coil windings, once they are energized, they may be represented in the form of a ferromagnetic cylinder with a solenoid wrapped around it. The wire of the solenoid is in practice the wire bundle located in each groove of the rotor. The rotor, when energized, then acts as an electromagnet, the magnetic field following the axis separating the wires of the solenoid in the direction of the current which flows through them.

Figure (4-11): Rotor of the motor.

The motor, therefore, consists of fixed permanent magnets (the stator) a moving magnet (the rotor) and a metal shell to concentrate the flux (the motor body).

Figure (4-12): The magnets.


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By the attraction of opposite poles and repulsion of like poles, a torque then acts on the rotor and makes it turn. This torque is at a maximum when the axis between the poles of the rotor is perpendicular to the axis of the poles of the stator. As soon the rotor begins to turn, the fixed brushes make and break contact with the rotating commutator segments in turn. The rotor coils are then energized and de-energized in such a way that as the rotor turns, the axis of a new pole of the rotor is always perpendicular to that of the stator. Because of the way the commutator is arranged, the rotor is in constant motion, no matter what its position. Fluctuation of the resultant torque is reduced by increasing the number of commutator segments, thereby giving smoother rotation. By reversing the power supply to the motor, the current in the rotor coils, and therefore the north and south poles, is reversed. The torque which acts on the rotor is thus reversed and the motor changes its direction of rotation. By its very nature, the D.C. motor is a motor with a reversible direction of rotation. 4.2.1.1.4 Torque and speed of rotation The torque generated by the motor, and its speed of rotation, are dependent on each other. This is a basic characteristic of the motor; it is a linear relationship and is used to calculate the no-load speed and the start-up torque of the motor.

Figure (4-13): Torque vs. Speed curve.


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The curve for the output power of the motor is deduced from the graph of torque versus speed. P (W) =

602π x C (N.m) x N (rpm)

Figure (4-14): O/P Power vs. Rotation Speed curve.

The torques vs. speed and output power curves depends on the supply Voltage to the motor. The supply voltage to the motor assumes continuous running of the motor at an ambient temperature of 20°C in nominal operational conditions. It is possible to supply the motor with a different voltage (normally between -50% and + 100% of the recommended supply voltage). If a lower voltage is used compared to the recommended supply the motor will be less powerful. If a higher voltage is used, the motor will have a higher output power but will run hotter (intermittent operation is recommended).


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4.2.1.2 Servo Motor: 4.2.1.2.1 What Is a Servo?

A Servo is a small device that has an output shaft. This shaft can be positioned to specific angular positions by sending the servo a coded signal. As long as the coded signal exists on the input line, the servo will maintain the angular position of the shaft. As the coded signal changes, the angular position of the shaft changes. In practice, servos are used in radio controlled airplanes to position control surfaces like the elevators and rudders. They are also used in radio controlled cars, puppets, and of course, robots.

Servos are extremely useful in robotics. The motors are small, have built in control circuitry, and are extremely powerful for their size. A standard servo, which is pretty strong for its size. It also draws power proportional to the mechanical load. A lightly loaded servo, therefore, doesn't consume much energy. You can see the control circuitry, the motor, a set of gears, and the case. You can also see the 3 wires that connect to the outside world. One is for power (+5volts), ground, and the white wire is the control wire.

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4.2.2 Sensors:

4.2.2.1 Limit switches 4.2.2.2 Potentiometers

4.2.2.1 Limit Switches:

A push button switch such as those used for limit switches have an operational hysteresis that must be accommodated to avoid a false reading of its activation trigger point that acts as the positional reference. As the mechanical striker plate approaches and contacts the switch, there is a point where the switch triggers and opens the circuit (we are really only concerned with switches that are normally closed unless activated or triggered). Once activated, as the striker plate moves away from the switch, there is a small distance it must traverse before the switch will deactivate, closing the circuit again. This small distance is the hysteresis.

Figure (4-15): Limit switch positions. Position 1 is where the switch rests when untouched. Position 2 is where the switch triggers, interrupting current. Position 3 is where the switch closes again as pressure is released. The space between 2 & 3 is the hysteresis


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Figure (4-16): Limit switch.

4.2.2.1.1 Features

• Long operating life. • Elongated mounting hole for easier, more accurate mounting • Choice of actuation (plunger, as well as a variety of integral and

auxiliary actuators). • Choice of electrical termination (solder, quick connect, PCB). • Choice of operating characteristics (sensitive differential travel as low

as 0,0254 mm [0.001 in] maximum, low operating force to 0,56 N [2.0 oz] maximum).

• Optional series constructions available (gold contacts for low energy switching, bifurcated gold contacts for maximum reliability, power load switching capability to 11 A).

4.2.2.1.2 Typical Applications

• Aerospace • Instrumentation • Appliances • Vending machines • Timing devices • Office equipment • Computer/business equipment • Test instruments • Medical/dental equipment • Communications equipment • HVAC equipment • Manually operated devices • Valves.


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4.2.2.2 Potentiometers 4.2.2.2.1 Types of Potentiometer • Wire wound

– Wiper slides along coil of Ni-chrome wire – Wire tends to fail, temperature variations

• Cermets – Wiper slides on conductive ceramic track – Better than wire inmost respects

• Plastic film – High resolution – Long life and good temperature stability

4.2.2.2.2 When to use a Potentiometer:

– Require analog signal for control – Require absolute positional information – Low cost – Temperature and wear variations – Not in dusty or wet environments.

Figure (4-17): potentiometer.


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Chapter 5: PCB M/C PROGRAMMING & S/W


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5.1 Introduction: 5.1.1 What is a Microcontroller? Microcontrollers are task-specific chips that are typically very cheap to build and quite reliable in the field. Most microcontrollers are single-chip-integrated systems. Typically such a microcontroller would have many on-chip peripheral features. Most microcontrollers have the ability to control program and data memory and input-output ports. Reliability in microcontrollers is well documented, such reliability is achieved by limiting end-user data-input. By “end-user” we refer to the final purchaser of a device with such a microcontroller. Yet we already allow computers to control objects in our lives, with hardly any bad effects. The reason so many of these devices are running smoothly is that they use microcontrollers. By limiting end-user data-input, the microcontroller’s operating software is less likely to develop bugs. A virus is virtually impossible to put into a microcontroller, as end-users don’t usually have the means to enter complex data structures or programs into the manufactured product. Many older microcontrollers are not capable of multiprocessing, which means that once a particular program is activated the chip will not relinquish control to any other program. Thus even if a new program could be created and loaded, somehow, into the microprocessor’s memory there would be no way to get it to execute. Microcontrollers take many different forms. The great majority of microcontrollers through the early eighties were 4-bit microcontrollers. Microcontrollers are typically talked of in terms of number of bits. This is a measure of the size of the data that can be computed by a particular microcontroller. Common sizes of microcontrollers today are 4-bit, 8-bit, 16-bit, and 32-bit. The most common size from 1991 through 1996 is 8-bit. Eight-bit microcontrollers continue through today as the most common


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5.1.2 Where are Microcontrollers used? The reason we find microcontrollers fascinating is that they have been and continue to be such an important part of the electronics industry. Over the past decade and more microcontrollers have been creeping into our daily lives. Figure 1 shows how microcontrollers increased in popularity from 1991 through 1996. The reason microcontrollers have become so common is that they are more than merely reliable. By adding a small computer to many devices it is possible to increase efficiency or safety, or any number of other features. Timing devices are now composed almost entirely of microcontrollers. This has made them unbelievably accurate. They are also cheap, and much more reliable. Telephones and other personal communication devices also use microcontrollers. With such devices it is possible to have wireless telephones and cellular phones, each capable of maintaining a connection between the phone unit and some sort of base station. These phones can also encrypt data as it leaves and decrypt it as it comes in. Televisions and stereos use microcontrollers. As a result, both produce better quality picture and sound, have more features, and weight less per unit volume. All kinds of transportation systems use microcontrollers. Cars use them in fuel injection systems, brakes, airbags, and just about any other piece of equipment. Airplanes are going to a “fly-by-wire” control system. This is a complex computer interface between the controls that the pilot uses and the control surfaces of the plane. Such interfaces are controlled by microcontrollers.


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Figure (5-1): Sales of microcontrollers vs. microprocessors, showing microcontrollers to be almost ten times more common in daily use than microprocessors. A dedicated and continuous task could be achieved easily with the help of microcontrollers. 5.1.3 General-purpose microprocessor:

• CPU for Computers • No RAM, ROM, I/O on CPU chip itself • Example Intel’s x86, Motorola’s 680x0

Figure (5-2): Micro-processor.


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5.1.4 Microcontroller

• A smaller computer • On-chip RAM, ROM, I/O ports... • Example Motorola’s 6811, Intel’s 8051, Zilog’s Z8 and PIC 16X

Figure (5-3): Micro-controller.

5.1.5 Microprocessor v.s. Microcontroller Microprocessor

• CPU is stand-alone, RAM, ROM, I/O, timer are separate • Designer can decide on the amount of ROM, RAM and I/O ports. • General-purpose • Expansive

Microcontroller • CPU, RAM, ROM, I/O and timer are all on a single chip • Fix amount of on-chip ROM, RAM, I/O ports • Single-purpose • Cheap • For applications in which cost, power and space are critical

5.1.6 Embedded System

• Embedded system means the processor is embedded into that application.

• An embedded product uses a microprocessor or microcontroller to do one task only.

• In an embedded system, there is only one application software that is typically burned into ROM.

• Some embedded products using microcontrollers. Example printer, keyboard, video game player, door opener, copier, ABS, fax machine, camera, cellular phone, keyless entry, microwave...


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5.1.7 Three criteria in Choosing a Microcontroller

1. Meeting the computing needs of the task efficiently and cost effectively:

• Speed, the amount of ROM and RAM, the number of I/O ports and timers, size, packaging, power consumption.

• Easy to upgrade. • Cost per unit.

2. Availability of software development tools • Assemblers, debuggers, C-compilers, emulator, simulator,

technical support

3. Wide availability and reliable sources of the microcontrollers. 5.1.8 Inside Architecture of AT90s8515

Figure (5-4): Inside Architecture of AT90s8515

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5.1.9 Micro-Controller (AT90S8515) specs:

• 32 general purpose registers • 32 Programmable I/O Lines • 8K Bytes of In-System Programmable Flash (program memory) • 8-bit Timer/Counter • 16-bit Timer/Counter • On-chip Analog Comparator • On-chip Analog Comparator • Programmable Serial UART


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5.2 First Module: The function of the program is to monitor the etching module through the whole process using 7 limit switches and a start push button starting from user pressing the start PB ending with the PCB board totally etched through exposing the board to the developer, etchant and water The control process is applied to two motors:

Arm motor: controlling the motion of the handle carrying the board monitored through LS1,2,3,,4,5

Basin motor : controlling the altitude of basins monitored through LS6,7

5.2.1 States:

• State 1: check on start button on pina,8 when pressed move arm motor in Forward direction

• State 2: Check on LS5 when pressed break arm motor start printing wait (14min.)

• State 3: when printing wait is finished Move arm motor in reverse direction.

• State 4: check on LS3 when pressed break arm motor, move basin motor in forward direction.

• State 5: Check on LS7 when pressed break basin motor start developing wait (1/4 min.)

• State 6: when developing wait is finished Move basin motor in reverse direction.

• State 7: Check on LS6 when pressed break basin motor, move arm motor in forward direction.


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• State 8: Check on LS4 when pressed break arm motor, move basin motor in forward direction.

• State 9: Check on LS7 when pressed break basin motor start watering wait (1/2 min.)

• State 10: when watering wait is finished Move basin motor in reverse direction.

• State 11: Check on LS6 when pressed break basin motor, move arm motor in reverse direction.


• State 13: Check on LS7 when pressed break basin motor start etching wait (15 min.)

• State 14: when etching wait is finished Move basin motor in reverse direction.

• State 15: Check on LS6 when pressed break basin motor, move arm motor in forward direction.


• State 17: Check on LS7 when pressed break basin motor start watering wait (1/2 min.).


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• State 18: when watering wait is finished Move basin motor in reverse direction.

• State 19: Check on LS6 when pressed break basin motor, move arm motor in reverse direction.

State 20: Check on LS1 when pressed break arm motor Start the process over.


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5.2.2 Flowchart:


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Legend of the flow chart: Wreg: waiting register Gw: get wait register State reg: state register Startpb: start push button MFx: move 'x' motor in forward direction MBx: break 'x' motor movement MRx: Move 'x' motor in reversed direction C1: counter no. 1 C2: counter no. 2 Tout: time out LSx: limit switch 'x'


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5.2.3 Micro-controller Program Code: ;assume 11.059MHZ .include"8515def.inc" .def temp=r16 .def state=r17 .def tout1=r18 .def tout2=r19 .def tout3=r20 .def tout4=r21 .def wreg=r22 .def c1=r23 .def c2=r24 .def Gw=r25 .org $000 rjmp start .org $004 rjmp program start: ;Initialization part cli ;stack initialization ldi temp,$02 out sph,temp ldi temp,$5f out spl,temp ;ports A&B are inputs C&D are outputs ldi temp,$00 out ddra,temp out ddrb,temp ldi temp,$ff out ddrc,temp out ddrd,temp ;Timer control registers ;starting value ldi temp,$00


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out tcnt1h,temp out tcnt1l,temp ;ending value (int. every 50msec( ldi temp,$02 out ocr1ah,temp ldi temp,$1c out ocr1al,temp ;define clk division & timer rest enable when compareA matches ldi temp,$0d out tccr1b,temp ldi temp,$05 out tccr0,temp ;define output pin action ldi temp,$00 out tccr1a,temp ;clearing timer flages ldi temp,$ff out tifr,temp ;compare matchA bit is set ldi temp,$40 out timsk,temp ;registers initialization ldi state,1 ldi tout1,$00 ldi tout2,$00 ldi tout3,$00 ldi tout4,$00 ldi c1,$00 ldi c2,$00 ldi wreg,$00 ldi Gw,$00 ldi temp,$00 sei ;initialization done mainloop: rjmp mainloop program: cpi wreg,1


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breq timeri ;Determining State ldi temp,1 cp state,temp Breq s1i ldi temp,2 cp state,temp Breq s2i ldi temp,3 cp state,temp Breq s3i ldi temp,4 cp state,temp Breq s4i ldi temp,5 cp state,temp Breq s5i ldi temp,6 cp state,temp Breq s6i ldi temp,7 cp state,temp Breq s7i ldi temp,8 cp state,temp Breq s8i ldi temp,9 cp state,temp Breq s9i ldi temp,10 cp state,temp Breq s10i ldi temp,11 cp state,temp Breq s11i ldi temp,12 cp state,temp Breq s12i ldi temp,13


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cp state,temp Breq s13i ldi temp,14 cp state,temp Breq s14i ldi temp,15 cp state,temp Breq s15i ldi temp,16 cp state,temp Breq s16i ldi temp,17 cp state,temp Breq s17i ldi temp,18 cp state,temp Breq s18i ldi temp,19 cp state,temp Breq s19i ldi temp,20 cp state,temp Breq s20i ;out of reach labels timeri: rjmp timer s1i: rjmp s1 s2i: rjmp s2 s3i: rjmp s3 s4i: rjmp s4 s5i: rjmp s5 s6i: rjmp s6 s7i:


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rjmp s7 s8i: rjmp s8 s9i: rjmp s9 s10i: rjmp s10 s11i: rjmp s11 s12i: rjmp s12 s13i: rjmp s13 s14i: rjmp s14 s15i: rjmp s15 s16i: rjmp s16 s17i: rjmp s17 s18i: rjmp s18 s19i: rjmp s19 s20i: rjmp s20 ;state conditions s1: in temp,pina sbrs temp,0 rcall MFa rjmp exit s2: in temp,pina Andi temp,0b00001000 cpi temp,0


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brne exit2 rcall MBa ldi wreg,1 ldi Gw,1 rjmp exit2 s3: cpi tout1,1 breq MRa1 rjmp exit s4: in temp,pina Andi temp,0b00100000 cpi temp,0 brne exit2 rcall MBa rjmp MFb s5: in temp,pina Andi temp,0b00000010 cpi temp,0 brne exit2 rcall MBb ldi wreg,1 ldi Gw,2 rjmp exit2 s6: cpi tout2,1 breq MRb1 rjmp exit s7: in temp,pina Andi temp,0b00000100 cpi temp,0 brne exit2 rcall MBb


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rjmp MFa s8: in temp,pina Andi temp,0b00010000 cpi temp,0 brne exit2 rcall MBa rjmp MFb s9: in temp,pina Andi temp,0b00000010 cpi temp,0 brne exit2 rcall MBb ldi wreg,1 ldi Gw,3 rjmp exit2 s10: cpi tout3,1 breq MRb1 rjmp exit1 ;out of reach labels exit2: rjmp exit1 ;state con. s11: in temp,pina Andi temp,0b00000100 cpi temp,0 brne exit1 rcall MBb rjmp MRa s12: in temp,pina


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Andi temp,0b01000000 cpi temp,0 brne exit1 rcall MBa rjmp MFb s13: in temp,pina Andi temp,0b00000010 cpi temp,0 brne exit1 rcall MBb ldi wreg,1 ldi Gw,4 rjmp exit1 ;out of reach labels MRa1: rjmp MRa MRb1: rjmp MRb ;state con. s14: cpi tout4,1 breq MRb rjmp exit s15: in temp,pina Andi temp,0b00000100 cpi temp,0 brne exit1 rcall MBb rjmp MFa s16: in temp,pina Andi temp,0b00010000 cpi temp,0


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brne exit1 rcall MBa rjmp MFb s17: in temp,pina Andi temp,0b00000010 cpi temp,0 brne exit1 rcall MBb ldi wreg,1 ldi Gw,3 rjmp exit1 s18: cpi tout3,1 breq MRb rjmp exit s19: in temp,pina Andi temp,0b00000100 cpi temp,0 brne exit1 rcall MBb rjmp MRa s20: in temp,pina Andi temp,0b10000000 cpi temp,0 brne exit1 rcall MBa ldi state,1 clr tout1 clr tout2 clr tout3 clr tout4 rjmp exit1


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exit1: rjmp exit ;C is taken as pin1, D is taken as pin0 ;subroutine no.1 for MA Forward action MFa: ldi temp,$02 out portc, temp inc state rjmp exit ;subroutine no.2 for MA Reversed action MRa: ldi temp,$01 out portc, temp inc state rjmp exit ;subroutine no.3 for MA break action MBa: ldi temp,$03 out portc, temp ret ;subroutine no.4 for MB Forward action MFb: ldi temp,$02 out portd, temp inc state rjmp exit ;subroutine no.5 for MB Reversed action MRb: ldi temp,$01 out portd, temp inc state rjmp exit ;subroutine no.6 for MB break action MBb:


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ldi temp,$03 out portd, temp ret ;every unit of c1=50msec , c2=255*50=12.75sec timer: inc c1 cpi c1,$01 brne exit clr c1 inc c2 ;which wait we want? getwait: cpi Gw,1 breq waiting1 cpi Gw,2 breq waiting2 cpi Gw,3 breq waiting3 cpi Gw,4 breq waiting4 rjmp exit ;subroutine no.7 for waiting ;printing wait=14 min waiting1: cpi c2,66 brne exit clr wreg ldi tout1,1 inc state clr c1 clr c2 rjmp exit ;Developing wait=1/2 min. waiting2: cpi c2,2


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brne exit clr wreg ldi tout2,1 inc state clr c1 clr c2 rjmp exit ;Water wait=1 min waiting3: cpi c2,5 brne exit clr wreg ldi tout3,1 inc state clr c1 clr c2 rjmp exit ;echting wait=15 min waiting4: cpi c2,71 brne exit clr wreg ldi tout4,1 clr tout3 inc state clr c1 clr c2 rjmp exit exit: reti


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5.3 Second Module: 5.3.1 CAD CAM system: To produce a PCB (printed circuit board) on CNC driller; you should have CAD CAM system which interface the PCB layout software with our machine hardware The flow of CAD CAM system in our project may be summarized in the following points:

1. The lay out of the PCB we want to manufacture is to be initially as jpg or bmp image.

2. We convert the image to dxf file using image2CAD software.

3. Then convert that dxf file to Gcode file using cad2Gcode software.

4. By using the MATLAB we extract the X points and the Y points in

the Gcode and transfer them by order to the parallel port.

5. The parallel port transfers the points to the microcontroller and waiting for the ready signal from it to transfer the next point.

6. The microcontroller give a signal to the X motor and Y motor and

from the feedback sensors it checks if the motors reached to its given point; that process be executed by a built in PD controller programmed over the microcontroller.

7. When the microcontroller ensure that the motors reaching that given

points from the parallel port it give ready signal to the parallel port to send the next point.


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5.3.2 flowchart:


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5.3.3 Matlab Program code: gh= ' enter the G code here ' for a=1:length(gh) if (gh(a)=='x') p1=a+1 p2=a+2 p4=a+4 p5=a+5 n1=str2num(gh(p1))*10 n2=str2num(gh(p2)) n4=str2num(gh(p4))*.1 n5=str2num(gh(p5))*.01 c=n1+n2+n4+n5 if (c>0) b=b+1 x(b)=c end end end d=1 for a1=1:length(gh) if (gh(a1)=='y') q1=a1+1 q2=a1+2 q4=a1+4 q5=a1+5 m1=str2num(gh(q1))*10 m2=str2num(gh(q2)) m4=str2num(gh(q4))*.1 m5=str2num(gh(q5))*.01 k=m1+m2+m4+m5 if (k>0) y(d)=k d=d+1 end end end


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dio = digitalio('parallel','LPT1'); addline(dio,[ 1 2 3 4 5 6 7 8 9 14 ],{'out','out','out','out' }); addline(dio,10,'in'); r1=0 r2=0 for co=1:length(x) TrigLine=getvalue(dio) if TrigLine==1 o1= dec2binvec(x(r1),10); putvalue(dio,o1) r1=r1+1 end TrigLine=getvalue(dio) if TrigLine==0 o2= dec2binvec(y(r2),10); r2=r2+1 putvalue(dio,o2) end end


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5.3.4 Micro-controller flowchart:


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5.3.5 Micro-controller program:

;assume 8MHZ .include"m8535def.inc" .def temp=r16 .def Mn=r17 .def setpl=r18 .def setph=r19 .def Apl=r20 .def Aph=r21 .def errorh=r22 .def errorl=r23 .org $000 rjmp start .org $007 rjmp program start: ;Initialization part cli ;stack initialization ldi temp,$02 out sph,temp ldi temp,$5f out spl,temp ;ports A&B are inputs C&D are outputs ldi temp,$00 out ddra,temp out ddrb,temp out ddrc,temp ldi temp,$ff out ddrd,temp ;Timer control registers ;starting value ldi temp,$00 out tcnt1h,temp out tcnt1l,temp


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;ending value (int. every 50msec) ldi temp,$02 out ocr1ah,temp ldi temp,$1c out ocr1al,temp ;define clk division & timer rest enable when compareA matches ldi temp,$0d out tccr1b,temp ldi temp,$05 out tccr0,temp ;define output pin action ldi temp,$00 out tccr1a,temp ;clearing timer flages ldi temp,$ff out tifr,temp ;compare matchA bit is set ldi temp,$10 out timsk,temp ;ADC intialization ldi temp,0b11000000 out admux,temp ldi temp,0b01010110 out adcsra,temp ldi temp,0b00001111 out Sifor,temp ;registers initialization ldi Mn,1 ldi acpl,$00 ldi acph,$00 ldi setpl,$00 ldi setph,$00 ldi errorl,$00 ldi errorh,$00 ldi temp,$00 sei ;initialization done program: ;get to M/C Zero in X-directio


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Zerox: in temp,pinc andi temp,0b00001000 cpi temp,$00 brne Normal_exe ldi Mn,$00 in temp,pinc andi temp,0b00010000 cpi temp,$00 breq Zeroy rcall MR rjmp exit ;get to M/C Zero in Y-directio Zeroy: ldi Mn,$04 in temp,pinc andi temp,0b00100000 cpi temp,$00 breq exit rcall MR rjmp exit ;M/C zero reached and getting set points Normal_exe: ;only get new set point if error is zero cpi errorl,$00 brne error_handling ;switching pin has 1 on it in temp,pind andi temp,0b10000000 cpi temp,$00 breq SwitchOne in temp,pind andi temp,0b01111111 out portd,temp nop rjmp get_setp


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;switching pin has 0 on it SwitchOne: in temp,pind ori temp,0b10000000 out portd,temp nop rjmp get_setp ;getting set point get_setp: in temp,pinb mov setpl,temp in temp,pinc andi temp,0b00000011 mov temp,setph ;determine error state error_handling: mov errorh,setph mov apl,ADCL mov aph,ADCH sub errorh,aph cpi errorh,$00 breq check_low sub errorh,$00 brmi MR rjmp MF ;checking low error_byte check_low: mov errorl,setpl sub errorl,apl cpi errorl,$00 breq drill sub errorl,$00 brmi MR rjmp MF ;drilling operation


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Drill: cpi Mn,$04 brne exit in temp,pinc andi temp,0b01000000 cpi temp,$00 brne exit ldi Mn,$08 rcall MF in temp,pinc andi temp,0b10000000 cpi temp,$00 brne exit ldi Mn,$00 rcall MR ;Motor controlling actions: ;Forward action MF: ori Mn,0b10000000 ldi temp,$02 or temp,Mn out portd,temp ret ;Reverse action MR: ori Mn,0b10000000 ldi temp,$01 or temp,Mn out portd,temp ret ;Break action ori mn,0b10000000 ldi temp,$03 or temp,Mn out portd,temp exit: reti


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Conclusion • Mechatronic systems can be designed and constructed through various

interfacing methods, of which we have chosen the use of Micro-Controllers.

• Micro-Controllers are task-specific chips that are typically very cheap to build and quite reliable in the field.

• This project shows the importance of Mechatronics in our present time, as it widens the scope of creation and invention to provide more reliable and precise systems.

The main drawbacks of our project are:

• The mechanical system is considerably not suitable for the production of the PCB.

• The use of UV unit has some hazards for the health and it needs dark, thus it should be isolated.

• The etching by immersion is considered an old way of etching which could be replaced by another method.

This project has added valuable knowledge & practical experience to us in various fields, Such as:

• The design and construction of a mechanical system. • The design and construction of electronic circuits. • The design and construction of electric circuits. • The usage of Micro-Controllers. • The usage of software packages for designing the mechanical design,

such as “Inventor” software package. • The usage of soft ware packages for designing the electric circuit,

such as “ORCAD” software package. • The usage of software packages for programming, such as

“MATLAB” software package. • The presentation of our work in an acceptable and attractive way. • The creation of a link between mechanical, electrical, electronic,

Micro-Controllers systems which is a representation for the Mechatronic system.


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References

1. THE MECHATRONICS HAND BOOK, Robert H. Bishop.

2. Mechatronics systems, George Pelz.

3. Sensor Technology Handbook, Jon S. Wilson.

4. A Handbook for the Mechanical Designer, Second Edition, Springfield, MO.

5. Mechanisms And Mechanical Devices Sourcebook, Sclater & Chironi.

6. Design Handbook, [McGraw-Hill 2004], Rothbart H.A. 7. Mechanical Engineering Handbook Ed. Frank Kreith Boca Raton: CRC

Press LLC, 1999.

8. http://www.pennmotion.com/quick_index.html (Motor data sheet)

9. http://www.geocities.com/dsaproject/electronics/cnc/cnc_ctrl.html

10. http://pcbdrill.fws1.com/

11. http://www.maxim-ic.com/appnotes.cfm/appnote_number/764

12. http://www.etisystems.com/mw22.asp

13. http://www.uoguelph.ca/~antoon/gadgets/741/741.html

Education

BSc thesis full document