MINOR PROJECT REPORT

ON

PC-BASED MOBILE ROBOT FOR NAVIGATIONSUBMITTED AS A PART OF COURSE CURRICULUM FOR

DEGREE OF BACHELOR OF TECHNOLOGY

IN

ELECTRONICS & COMMUNICATION ENGINEERING

Under the guidance of: SUBMITTED BY:

M.K.Soni Ashish Goel (2206020)

(Lectt. ECE) Kanwal Singh (2206049)

Krishan Rangi(2206050)

Department of Electronics & Communication Engineering

Swami Devi Dyal Inst i tute Of Engineer ing & Technology Barwala(PKL. )

SWAMI DEVI DYAL INSTITUTE OF ENGINEERING & TECHNOLOGY

BARWALA, PANCHKULA

ISO:9001:2000 QMS,AFFILIATED TO KURUKSHETRA

UNIVERSITY

APPROVED BY AICTE

Ref: Dated:__________

Certificate

Certified that this project entitled “PC-BASED MOBILE ROBOT

FOR NAVIGATION” submitted by Ashish Goel(2206020), Kanwal

Singh (2206049), Krishan Rangi(2206050) of Swami Devi Dyal

Institute of Engineering & Technology, Barwala as a part of course

curriculum for B.Tech.(Electronics & communication Engineering)

Degree of Kurukshetra University, Kurukshetra, is a record of student’s

own study carried under my supervision & guidance.

This report has not been submitted to any other university or institution

for the award of any degree.

HOD : Under the guidance of :

Er.Rajnish Garg Er. M.K. Soni

HOD ECE(Deptt.) Lect. ECE(Deptt.)

ACKNOWLEDGMENT

We feel honored to have worked under the able guidance of our Lect. Mr. M.K. Soni.

We are particularly grateful to Mr. Rajnish garg (HOD ECE) & Mr. Amit Gupta (Sr. Lect. ECE) for there valuable advice and timely suggestions in helping us overcome all sorts of problems.

We extend our heartiest thanks to the entire staff members who gave suggestions during the development of the project.

Ashish Goel(2206020)

Kanwal Singh(2206049)

Krishan Rangi(2206050)

PREFACE

Excellence is an attitude that the whole of the human race is born with. It is the environment that makes sure that whether the result of this attitude is visible or otherwise. A well planned, properly executed & evaluated industrial training help a lot in inculcating a professional attitude. It provides a linkage between the student and industry to develop an awareness of industrial approach to problem solving, based on board understanding of process & mode of operation of organization. During this period, the student gets the real, firsthand experience for working in the actual environment.

The quest for knowledge can never end. The deeper you dig the greater this unexplored seems to be. No man can honestly say that he has learned this world has to offer. We can’t achieve anything worthwhile in any field only on the basis of theoretical knowledge from books.

ABSTRACT

It is truly said that practice makes a man perfect. But as far as

project making is concerned, it refers to combination of certain

constructive ideas building up consistent project team, analyzing

and rearranging of raw materials and resources, finalizing the

methodology and making things really work out practically. It is

definitely necessary to have strong command over the theoretical

and practical aspects of project under consideration, as all

theoretical knowledge and practical application goes in vain if we

can’t fetch desired results. The minor project is an output of our

exposure to the real and applied world of electronics.

The aim of this report is to briefly cover whatever has

been done during making of the minor project. The project “ Pc-

based mobile robot ” for navigation.

LIST OF FIGURES

S.no. FIGURE NAME PAGE no.

1 Working prototype of the PC-Based mobile robot 2

2 Program output of mobile robot 8

3 Actual-Size, Single Side PCB for PC-Based Mobile Robot For Navigation

12

4 Component Layout for the PCB 12

5 Working prototype of the PC-Based mobile robot 16

6 Power supply 16

7 Working prototype of the PC-Based mobile robot 18

8 An optocoupler 20

9 Schematic diagram of opto-isolator 21

10 A simple circuit with an opto-isolator 22

11 Darlington Array 24

12 Pin Diagram of ULN 2803 25

13 Rectifier Diodes 26

14 LED’s 27

15 Carbon film resistors 28

16 Metal film resistors 29

17 Variable Resistors 30

18 Electrolytic Capacitors 32

19 Ceramic Capacitors 33

20 25-pin,D-type, parallel-port male connector 35

21 Rotation of stepper motor 37

22 A picture of stepper motor 41

23 A typical low-cost webcam used with many personal computers

44

24 A step-down transformer 46

25 Rectification of AC 47

26 26Electrolytic Capacitor 48

27 Voltage Regulator 7805 48

28 soldering iron 50

29 solder 50

LIST OF TABLES

S.no. TABLE NAME PAGE no.

1 Colour codes of the Wires for 55SlM-25DAYG Stepper Motor

6

2 Normal 4 –step Sequence 7

3 Sizes of different resistors 28

4 Sizes of different resistors 29

5 Color Codes of resistor 30

6 Function of pins of 25-pin,D-type, parallel-port male connector

35

7 Base addresses 36

CONTENTS Certificate

Acknowledgement i

Preface ii

Abstract iii

List of Figures iv

List of Tables vi

Block Diagram viii

Circuit Diagram ix

List of components x

1. Introduction 1

2. Circuit Description 3

3. Robot Control Operation 5

4. Construction 10

5. Tips for assembling the robot 13

6. Pictures of Project 16

7. Testing procedure 17

8. Hardware Details 19 9. PCB Etching

4910. Soldering

5011. Software used

5212. Problems faced

6113. Future scope

6214. References 63Appendix

Datasheets

Block Diagram

motor motor

Pc with controllin

g software

CIRCUIT DIAGRAM

LIST OF COMPONENTS

S.no. Component Specification Quantity

Semiconductors:

1. IC1-IC8 MCT2E optocoupler 8

2. IC9 ULN2803 buffer/driver 1

3. IC10 7812 12V regulator 1

4. D1-D4 1N4001 rectifier diode 4

5. LED1 5mm light- emitting diode 1

Resistors: (all ¼ watt, ± 5% carbon)

6. R1 1-kilo-ohm 1

7. R2-R9 470-ohm 8

Capacitors:

8. C1 1000uF,35V electrolytic 1

9. C2 0.1uF,ceramic 1

Miscellaneous:

10. X1 230V AC primary to 15V,1A secondary transformer

1

11. CON1 25-pin,D-type, parallel-port male connector

1

12. SM1,SM2 12V, 7.5 deg/step stepper motor

8-conductor ribbon cable (3.5 metres in length)

Two wheels for the right and left side of the robot

One caster wheel for front

Two side brackets for stepper motors support

One chassis board One web cam or pc-

camera with USB interface cable

nuts and bolts 2-pin sip connector (male

and female) Two 5-pin sip male

connector DC socket and plug

2

1

2

1

2

1

1

30

1

1

2

INTRODUCTION

Pc - based Mobile Robot for Navigation is basically an electric-powered, three-wheeled vehicle or robot attached with a PC camera or webcam. It can be used for navigation or as a toy. The robot can move up to a radial distance of 3.5 meters from the computer. For longer distance, you need a longer data cable for the parallel port and USB hub to increase the length of the interface cable for the camera. The purpose of this design and implementation is to motivate the beginners. It cannot be used independently in line following, obstacle detection and pothole avoidance applications as it is not intelligent enough to take decision and control by itself. However, line following, obstacle detection and pothole detection can be done by constantly monitoring its movement from the live scene captured by the PC camera. It can be controlled from the PC to move forward, backward, right and left. The project provides an educational test bed for understanding the transition from theory to practice, contest requirements and also other studies in developing advance applications, creative control, etc. The working of the circuit, control system, sensory system, software program, testing and assembly steps for the robot are described in the succeeding sections. The main components include two stepper motors, a motor driver circuit, a PC with parallel port connector and a camera (webcam).

Circuit description

The interface-cum-driver circuit for the PC-based mobile robot is shown in Fig. 2. It works off a 12V DC Power supply. MCT2E is the most popular integrated circuit used for isolating high-voltage circuits from low-voltage circuits. Used to protect the parallel port from damage, it is an opto-coupler having an internal phototransistor and an LED. The LED glows when it receives high output pulse from the parallel port. The transistor conducts when its base receives light from LED. Resistors R2 through R9 limit the in order to protect the parallel port. IC ULN2803 is used as the driver for rotating the stepper motor. It is basically a Darlington pair IC used for driving high-current circuits. The power supply circuit is shown in Fig. 3. It consists of a 230V AC to 15V AC, 1A secondary transformer, filter capacitor, bridge rectifiers and 12VDC regulator 7812 (1C10). The regulated 12V DC is connected to ULN2803 driver IC. In place of the power supply circuit shown in Fig. 3, you can also use a 12V, 4.5Ah battery to power the main circuit.

Robot control operation

Two stepper Motors are used for moving and turning the robot. Stepper motors with various specification are available in the market. Here we have used 55SIM 25DAYG unipolar stepper motors rated at 12V DC, with step angle of 7.5" per pulse. Each of these stepper motors has five wires for connecting to the driver circuit. Out of the five wires, four wires emerge from coils of the stepper motors and the fifth is the centre-tapped common terminal. Correct identification and connection of these wires is important for successful assembly of the stepper motor. The unipolar stepper motor has two centre-tapped coils. Their centre-tapped terminals are joined to make one common terminal. If you have a multimeter, set it in 200-ohm range and check the resistance between these wires The resistance between the common terminal and the rest of the coil terminals will be around 36 ohms, while the resistance between two coil terminals will be around 72 ohms. Connect these coils to the output terminals of the driver circuit in sequence. To help you in proper connection, the colour codes of the wires for the 55SIM-25DAYG stepper motor are listed in Table I. Note that for the same ratings, different manufacturers may have their own coil specifications.

TABLE 1

Colour codes of the Wiresfor 55SlM-25DAYG

Stepper Motor

Colour IdentificationWhite CommonRed L1Blue L2

Brown L3Yellow L4

The software uses wave-drive 4- step sequence technique for rotating the motors. To run the motors, specific sequences of pulses are given to the motor windings. Generally, there are three types of digital signal sequence given to run the stepper motor. But here, we have used a 4-step sequence as shown in Table II. The advantage of this technique is that it consumes the least power. Only one phase is energized at a time, which assures of positional accuracy regardless of any winding imbalance in the motor.

TABLE 2

Normal 4 –step SequenceClockwi

s-eStep

#Windin-g A

L1

Windin-g B

L2

Windin-g C

L3

Windin-g D

L4

Counter Clockwi

s-e1 1 0 0 02 0 1 0 03 0 0 1 04 0 0 0 1

Since the motor rotates at 7.5 deg per step, it takes a total of 48 steps to complete one rotation. The higher the step angle, the fewer the pulses needed for complete rotation of the motor. Hence if the speed of the robot is desired, use a motor with higher step angle, and if more accurate position control is desired, you may use a motor with lower step angle.

Direction control.:

To control the direction of motion, a combination of different rotational directions of the two motors is used. If the left stepper motor (SM1) moves anticlockwise and the right stepper motor (SM2) moves clockwise, the robot moves in forward direction. Similarly, if SM1 moves in clockwise direction and SM2 in anti-clockwise, the robot will move in backward direction. If SM1 and SM2 move in clockwise direction, the robot will turn left. If SM1 and SM2 move in anti-clockwise direction, the robot will turn right.

Speed control .:

To control the speed of the robot, timer delays are used. The value of the delay time for the timer can be increased or decreased by the slider control provided in the software. The selected speed of the robot (1 through 999) is also displayed in the text box as shown in Fig. 4.

Camera view.:

In this project, a camera is used as the visual sensor to control the movement of the robot. For live viewing of the scene through the camera fitted on the robot, a command button is provided in the software. On clicking the button, the executable file of the camera is run and the pictures can be viewed in another window. We have used a 'Quantum Hi-Tech' camera. It has l0 level zoom for live motion picture, special visual effects, night vision, microphone, snapshot function etc.

Construction

Constructing this project is very simple. Just assemble the ICs and resistors on any general-purpose PCB and mount the stepper motors over any solid base with the help of suitable mechanical parts. Put the camera on the base and fix it with the help of clam or nuts and bolts.

The actual-size, single-side PCB layout of the circuit is shown in Fig. 5 and its component layout in Fig. 6. Cut the PCB along the straight line shown in the integrated PCB layout (Figs 5 and 6) to separate the power supply section. The PCB layout for the power supply section is made separately so that if you want to use a 12v battery you can remove it from the interface-cum-driver section.

Fig. 5. Actual-Size, Single Side PCB for PC-Based Mobile Robot For Navigation

Fig:6. Component Layout for the PCB

Tips for assembling the robot

1. First, secure the stepper motors into the two side-brackets

2. Next, fix the wheels on the shaft of the motors. (Each of the wheel has an 8mm plastic flange with threads and a metal nut for securing it in position).

3. Now, take the chassis or base plate. Identify its front, left, right and rear sides. Secure the PCB and camera on the chassis plate.

4. Secure the side-brackets( left and right) on the chassis plate.

5. Insert the front castor-wheel bolt into the 10mm hole on the chassis and secure it loosely with the help of its nut. Check the chassis level. Use extra spacers over the threaded portion of castor-wheel nut after removing the castor wheel. If the leveling appears alright, tighten the castor wheel to the chassis.

6. Now, insert the connectors of the two motors in the circuit as shown in the PCB layout diagram. Connect the 12V power supply connector to the PCB. This completes the mechanical assembly of your robot and external electrical connections. (Before connecting the 12V supply to the circuit, re-check the assembly for proper and complete connections.)

7. Check directions of rotations of the two stepper motors by clicking 'Move Forward' button in the Mobile robot.exe

program. Both the stepper motors should energies and rotate in such direction as to move the robot forward. In case one or both of the stepper motors rotate in reverse direction, identify the leads by referring the colour codes of the coils for the 55SIM-25DAYG stepper motor as listed in Table I and connect them accordingly.

Testing procedure

1. Mount the stepper motors and camera on the base as shown in Fig. 1.

2. After assembling the PCB, check the circuit connections before switching on the power supply.

3. Connect the parallel-port cable (with male connector) to the parallel port female connector available on the back side of the PC.

4. Run the software to see that the robot is running properly.

HARDWARE DETAILS

OPTO-ISOLATOR OR OPTO-COUPLER

In electronics, an opto-isolator (or optical isolator, optical coupling device, optocoupler, photocoupler, or photoMOS) is a device that uses a short optical transmission path to transfer an electronic signal between elements of a circuit, typically a transmitter and a receiver, while keeping them electrically isolated—since the electrical signal is converted to a light beam, transferred, then converted back to an electrical signal, there is no need for electrical connection between the source and destination circuits. Isolation between input and output is rated at 7500 Volt peak for 1 second for a typical component costing less than 1 US$ in small quantities.

The opto-isolator is simply a package that contains both an infrared light-emitting diode (LED) and a photodetector such as a photosensitive silicon diode, transistor Darlington pair, or silicon controlled rectifier (SCR). The wave-length responses of the two devices are tailored to be as identical as possible to permit the highest measure of coupling possible. Other circuitry—for example an output amplifier—may be integrated into the package. An opto-isolator is usually thought of as a single integrated package, but opto-isolation can also be achieved by using separate devices.

Digital opto-isolators change the state of their output when the input state changes; analog isolators produce an analog signal which reproduces the input.

Schematic diagram of a very simple opto-isolator with an LED and phototransistor. The dashed line represents the isolation barrier, over which there is no electrical contact.

A common implementation is a LED and a phototransistor in a light-tight housing to exclude ambient light and without common electrical connection, positioned so that light from the LED will impinge on the photodetector. When an electrical signal is applied to the input of the opto-isolator, its LED lights and illuminates the photodetector, producing a corresponding electrical signal in the output circuit. Unlike a

transformer the opto-isolator allows DC coupling and can provide any desired degree of electrical isolation and protection from serious overvoltage conditions in one circuit affecting the other. A higher transmission ratio can be obtained by using a Darlington instead of a simple phototransistor, at the cost of reduced noise immunity and higher delay.

With a photodiode as the detector, the output current is proportional to the intensity of incident light supplied by the emitter. The diode can be used in a photovoltaic mode or a photoconductive mode. In photovoltaic mode, the diode acts as a current source in parallel with a forward-biased diode. The output current and voltage are dependent on the load impedance and light intensity. In photoconductive mode, the diode is

connected to a supply voltage, and the magnitude of the current conducted is directly proportional to the intensity of light. This optocoupler type is significantly faster than photo transistor type, but the transmission ratio is very low; it is common to integrate an output amplifier circuit into the same package.

The optical path may be air or a dielectric waveguide. When high noise immunity is required an optical conductive shield can be integrated into the optical path. The transmitting and receiving elements of an optical isolator may be contained within a single compact module, for mounting, for example, on a circuit board; in this case, the module is often called an optoisolator or opto-isolator. The photosensor may be a photocell, phototransistor, or an optically triggered SCR or TRIAC. This device may in turn operate a power relay or contactor.

Analog optoisolators often have two independent, closely matched output phototransistors, one of which is used to linearize the response using negative feedback.

A simple circuit with an opto-isolator. When switch S1 is closed, LED D1 lights, which triggers phototransistor Q1, which pulls the output pin low. This circuit, thus, acts as a NOT gate.

APPLICATIONS

Among other applications, opto-isolators can help cut down on ground loops, block voltage spikes, and provide electrical isolation.

switched-mode power supplies use optocouplers for mains isolation. As they work in an environment with much electrical noise and with signals which are not small, optocouplers with low transmission ratio are preferred.

Where electrical safety is paramount, optocouplers can totally isolate circuitry which may be touched by humans from mains electricity.

o Medical equipment often uses optocouplers. o One of the requirements of the MIDI (Musical Instrument

Digital Interface) standard is that input connections be opto-isolated.

Optocouplers are used to isolate low-current control or signal circuitry from transients generated or transmitted by power supply and high-current control circuits. The latter are used within motor and machine control function blocks.

DARLINGTON ARRAY (ULN 2803)

INTRODUCTION

A ULN2803 is an Integrated Circuit (IC) chip with a High Voltage/High Current Darlington Transistor Array. It allows you to interface TTL signals with higher voltage/current loads. In English, the chip takes low level signals (TLL, CMOS, PMOS, NMOS - which operate at low voltages and low currents) and acts as a relay of sorts itself, switching on or off a higher level signal on the opposite side.

Its features are:

A TTL signal operates from 0-5V, with everything between 0.0 and 0.8V considered "low" or off, and 2.2 to 5.0V being considered "high" or on. The maximum power available on a TTL signal depends on the type, but generally does not exceed 25mW (~5mA @ 5V), so it is not useful for providing power to something like a relay coil. On the output side the ULN2803 is generally rated at 50V/500mA, so it can operate small loads directly.

Alternatively, it is frequently used to power the coil of one or more relays, which in turn allow even higher voltages/currents to be controlled by the low level signal. In electrical terms, the ULN2803 uses the low level (TTL) signal to switch on/turn off the higher voltage/current signal on the output side.

Its features are summarized below: Output current (single output) 500mA MAX. High sustaining voltage output 50V MIN. Output clamp diodes. Inputs compatible with various types of logic

PIN DIAGRAM

The ULN2803 comes in an 18-pin IC configuration and includes eight (8) transistors.

Pins 1-8 receive the low level signals, pin 9 is grounded (for the low level signal reference). Pin 10 is the common on the high side and would generally be

connected to the positive of the voltage you are applying to the relay coil.

Pins 11-18 are the outputs (Pin 1 drives Pin 18, Pin 2 drives 17, etc.).

DIODES

A diode is a semiconductor device which allows current to flow through it in only one direction. A diode is specifically made to allow current to flow through it in

only one direction.

Some ways in which the diode can be used are listed here.A diode can be used as a rectifier that converts AC to DC for a power

supply device.Diodes can be used to separate the signal from radio frequencies.Diodes can be used as an on/off switch that controls current.

This symbol is used to indicate a diode in a circuit diagram

Rectification / Switching / Regulation Diode

The stripe stamped on one end of the diode shows indicates the polarity of the diode.The stripe shows the cathode side.The devices shown in the picture are diodes used for rectification. They are made to handle relatively high currents. The device on top can handle as high as 6A, and the one below it can

safely handle up to 1A.However, it is best used at about 70% of its rating because this current value is a maximum rating. This diode is typically used to protect the circuit from momentary voltage spikes.

Light Emitting Diode ( LED )

Light emitting diodes must be chosen according to how they will be used, because there are various kinds.

The diodes are available in several colors. The most common colors are red and green, but there are even blue ones.The device on the far right in the photograph combines a red LED and green LED in one package. The component lead in the middle is

common to both LEDs. As for the remaing two leads, one side is for the green, the other for the red LED. When both are turned on simultaneously, it becomes orange.

RESISTORS

The resistor's function is to reduce the flow of electric current. This symbol is used to indicate a resistor in a circuit diagram, known as a schematic. Resistance value is designated in units called the "Ohm." There are two classes of resistors; fixed resistors and the variable resistors. They are also classified according to the material from which they are made.

Fixed ResistorsA fixed resistor is one in which the value of its resistance cannot change.

Carbon film resistorsThis is the most general purpose, cheap resistor. Usually the tolerance of the resistance value is ±5%. Power ratings of 1/8W, 1/4W and 1/2W are frequently used. Carbon film resistors have a disadvantage; they tend to be electrically noisy. The physical size of different resistors are as follows.

Rough size

Rating power(W)

Thickness(mm)

Length(mm)

1/8 2 3

1/4 2 6

1/2 3 9

From the top of the photograph1/8W1/4W

1/2W

Metal film resistorsMetal film resistors are used when a higher tolerance (more accurate value) is needed. They are much more accurate in value than carbon film resistors. They have about ±0.05% tolerance. They have about ±0.05% tolerance. Ni-Cr (Nichrome) seems to be used for the material of resistor. The metal film resistor is used for bridge circuits, filter circuits, and low-noise analog signal circuits.

From the top of the photograph

1/8W (tolerance ±1%)

1/4W (tolerance ±1%) 1W (tolerance ±5%) 2W (tolerance ±5%)

Variable resistorsThere are two general ways in which variable resistors are used.

1. One is the variable resistor which value is easily changed, like the volume adjustment of Radio.

2. The other is semi-fixed resistor that is not meant to be adjusted by anyone but a technician. Semi-fixed resistors are used to

Rough size

Rating power(W)

Thickness(mm)

Length(mm)

1/8 2 3

1/4 2 6

1 3.5 12

2 5 15

compensate for the inaccuracies of the resistors, and to fine-tune a circuit

The rotation angle of the variable resistor is usually about 300 degrees. Some variable resistors must be turned many times to use the whole range of resistance they offer.These are called "Potentiometers" or "Trimmer Potentiometers."

In the photograph , the four resistors at the center of the photograph are the semi-fixed type. The two resistors on the left are the trimmer potentiometers.This

symbol is used to represent variable resistor in circuit diagram

Resistor colour code

Example 1(Brown=1),(Black=0),(Orange=3)

10 x 103 = 10k ohmTolerance(Gold) = ±5%

Colour Value Multiplier Tolerance

Black 0 0 -

Brown 1 1 ±1

Red 2 2 ±2

Orange 3 3 ±0.05

Yellow 4 4 -

Green 5 5 ±0.5

Blue 6 6 ±0.25

Violet 7 7 ±0.1

Gray 8 8 -

White 9 9 -

Gold - -1 ±5

Silver - -2 ±10

None - - ±20

Example 2(Yellow=4),(Violet=7),(Black=0),(Red=2)

470 x 102 = 47k ohm

Tolerance(Brown) = ±1%

CAPACITORS

The capacitor's function is to store electricity, or electrical energy. The capacitor also functions as a filter, passing alternating current (AC), and blocking direct current (DC).This symbol is used to indicate a capacitor in a circuit diagram.

The capacitor is constructed with two electrode plates facing eachother, but separated by an insulator. When DC voltage is applied to the capacitor, an electric charge is stored on each electrode. While the capacitor is charging up, current flows. The current will stop flowing when the capacitor has fully charged.

The value of a capacitor (the capacitance), is designated in units called the Farad ( F ). The capacitance of a capacitor is generally very small, so units such as the microfarad ( 10-6F ), nanofarad ( 10-9F ), and picofarad (10-12F ) are used.Sometimes, a three-digit code is used to indicate the value of a capacitor. For example, when the code is [103], it indicates 10 x 103, or 10,000pF = 10 nanofarad( nF ) = 0.01 microfarad( µF ).

BREAKDOWN VOLTAGE

When using a capacitor, you must pay attention to the maximum voltage which can be used. This is the "breakdown voltage." The breakdown voltage is the voltage that when exceeded will cause the dielectric (insulator) inside the capacitor to break down and conduct. When this happens, the failure can be catastrophic.

The types of capacitors used in our project are:

Electrolytic Capacitors (Electrochemical type capacitors)

Aluminum is used for the electrodes by using a thin oxidization membrane.

Large values of capacitance can be obtained in comparison with the size of the capacitor, because the dielectric used is very thin.

The most important characteristic of electrolytic capacitors is that they have polarity. They have a positive and a negative electrode.[Polarised]

If the capacitor is subjected to voltage exceeding its working voltage, or if it is connected with incorrect polarity, it may burst.

Generally, in the circuit diagram, the positive side is indicated by a "+" (plus) symbol.

Electrolytic capacitors range in value from about 1µF to thousands of µF. Mainly this type

of capacitor is used as a ripple filter in a power supply circuit, or as a filter to bypass low frequency signals, etc.

From the left to right:1µF (50V) [diameter 5 mm, high 12 mm] 47µF (16V) [diameter 6 mm, high 5 mm] 100µF (25V) [diameter 5 mm, high 11 mm] 220µF (25V) [diameter 8 mm, high 12 mm] 1000µF (50V) [diameter 18 mm, high 40 mm]

Ceramic Capacitors

Ceramic capacitors are constructed with materials such as titanium acid barium used as the dielectric. Internally, these capacitors are not constructed as a coil, so they can be used in high frequency

applications. Typically, they are used in circuits which bypass high frequency signals to ground.These capacitors have the shape of a disk. Their capacitance is

comparatively small.

The capacitor on the left is a 100pF capacitor with a diameter of about 3 mm.The capacitor on the right side is printed with 103, so

10 x 103pF becomes 0.01 µF. The diameter of the disk is about 6 mm.

Ceramic capacitors have no polarity. Ceramic capacitors should not be used for analog circuits, because they can distort the signal.

25-pin,D-type, parallel-port male connector

The parallel port is a 25 pin connector on your computer that is commonly known as the printer port, LPT1 or LPT2. This port is nice because it is relatively easy to manipulate it with software and the data is transmitted using standard TTL 0 – 5V signals. Another pro to using this port is there is no need for additional hardware to put the signal back together so that it can be loaded into the microcontroller.

To utilize the parallel interface we would need 8 pins for the data transmission, 1 pin is an IRQ which signals that the data is ready and clocks it through, 1 pin to signal whether the data transmission was an address or actual data because we are employing multiple

microcontrollers, and 1 pin to send a signal back to the PC telling it that the current task has been accomplished and it is ready for the next instruction.

Now just to transmit data we need 11 pins and 2 pins are power and ground, so that only leaves 3 pins on port A to control our motor, which is enough for now, but cuts down on capability for future expansion.

This is a pin out diagram of the 25-pin,D-type, parallel-port male connector.

The following table lists the function of each pin in the 25-pin,D-type, parallel-port male connector as they pertain to a printer connection. The most useful part is the direction of signal flow for our application, as well as knowing whether the bit is inverted or not.

This next table lists the base addresses for the status, control and data registers of LPT1 and LPT2.

Stepper motor

A stepper motor (or step motor) is a brushless, synchronous electric motor that can divide a full rotation into a large number of steps. The motor's position can be controlled precisely, without any feedback mechanism. Stepper motors are similar to switched reluctance motors (which are very large stepping motors with a reduced pole count, and generally are closed-loop commutated.)

Fundamentals of Operation

Stepper motors operate differently from DC brush motors, which rotate when voltage is appliedto their terminals. Stepper motors, on the otherhand, effectively have multiple "toothed" electromagnets arranged around a central gear-shaped piece of iron. The electromagnets are energized by an external control circuit, such as a microcontroller.

To make the motor shaft turn, first one electromagnet is given power, which makes the gear's teeth magnetically attracted to the electromagnet's teeth. When the gear's teeth are thus aligned to the first electromagnet, they are slightly offset from the next electromagnet. So when the next electromagnet is turned on and the first is turned off, the gear rotates slightly to align with the next one, and from there the process is repeated. Each of those slight rotations is called a "step," with an integer number of steps making a full rotation. In that way, the motor can be turned by precise angle.

Stepper motor characteristics

1. Stepper motors are constant power devices.

2. As motor speed increases, torque decreases.

3. The torque curve may be extended by using current limiting drivers and increasing the driving voltage.

4. Steppers exhibit more vibration than other motor types, as the discrete step tends to snap the rotor from one position to another.

5. This vibration can become very bad at some speeds and can cause the motor to lose torque.

6. The effect can be mitigated by accelerating quickly through the problem speeds range, physically damping the system, or using a micro-stepping driver.

7. Motors with a greater number of phases also exhibit smoother operation than those with fewer phases.

Types

There are three main types of stepper motor.

1. Permanent Magnet Stepper2. Hybrid Synchronous Stepper3. Variable Reluctance Stepper

Permanent magnet motors use a permanent magnet (PM) in the rotor and operate on the attraction or repulsion between the rotor PM and the stator electromagnets. Variable reluctance (VR) motors have a plain iron rotor and operate based on the principle of that minimum reluctance occurs with minimum gap, hence the rotor points are attracted toward the stator magnet poles. Hybrid stepper motors are named because they use use a combination of PM and VR techniques to achieve maximum power in a small package size.

Two-phase stepper motors

There are two basic winding arrangements for the electromagnetic coils in a two phase stepper motor: bipolar and unipolar.

Unipolar motors

A unipolar stepper motor has two windings per phase, one for each direction of magnetic field. Since in this arrangement a magnetic pole can be reversed without switching the direction of current, the commutation circuit can be made very simple (eg. a single transistor) for each winding. Typically, given a phase, one end of each winding is made common: giving three leads per phase and six leads for a typical two phase motor. Often, these two phase commons are internally joined, so the motor has only five leads.

A microcontroller or stepper motor controller can be used to activate the drive transistors in the right order, and this ease of operation makes unipolar motors popular with hobbyists; they are probably the cheapest way to get precise angular movements.

Unipolar stepper motor coils

A quick way to determine if the stepper motor is working is to short circuit every two pairs and try turning the shaft, whenever a higher than normal resistance is felt, it indicates that the circuit to the particular winding is closed and that the phase is working.

Bipolar motor

Bipolar motors have a single winding per phase. The current in a winding needs to be reversed in order to reverse a magnetic pole, so the driving circuit must be more complicated, typically with an H-bridge arrangement. There are two leads per phase, none are common.

Static friction effects using an H-bridge have been observed with certain drive topologies.

Because windings are better utilised, they are more powerful than a unipolar motor of the same weight

Stepper motor

A step motor can be viewed as a synchronous AC motor with the number of poles (on both rotor and stator) increased, taking care that they have no common denominator. Additionally, soft magnetic material with many teeth on the rotor and stator cheaply multiplies the number of poles (reluctance motor). Modern steppers are of hybrid design, having both permanent magnets and soft iron cores

.

To achieve full rated torque, the coils in a stepper motor must reach their full rated current during each step. Winding inductance and reverse EMF generated by a moving rotor tend to resist changes in drive current, so that as the motor speeds up, less and less time is spent at full current -- thus reducing motor torque. As speeds further increase, the current will not reach the rated value, and eventually the motor will cease to produce torque.

Pull-in torque

This is the measure of the torque produced by a stepper motor when it is operated without an acceleration state. At low speeds the stepper motor can synchronise itself with an applied step frequency, and this Pull-In torque must overcome friction and inertia.

Pull-out torque

The stepper motor pull-out torque is measured by accelerating the motor to the desired speed and then increasing the torque loading until the motor stalls or "pulls out of synchronism" with the step frequency. This measurement is taken across a wide range of speeds and the results are used to generate the stepper motor's dynamic performance curve. As noted below this curve is affected by drive voltage, drive current and current switching techniques. It is normally recommended to use a safety factor of between 50% and 100% when comparing your desired torque output to the published "pull-Out" torque performance curve of a step motor.

Detent torque

Synchronous electric motors using permanent magnets have a remnant position holding torque (called detent torque, and sometimes included in the specifications) when not driven electrically. Soft iron reluctance cores do not exhibit this behavior.

Stepper motor ratings and specifications

Stepper motors nameplates typically give only the winding current and occasionally the voltage and winding resistance. The rated voltage will produce the rated winding current at DC: but this is mostly a meaningless rating, as all modern drivers are current limiting and the drive voltages greatly exceed the motor rated voltage.

A stepper's low speed torque will vary directly with current. How quickly the torque falls off at faster speeds depends on the winding inductance and the drive circuitry it is attached to, especially the driving voltage.

Steppers should be sized according to published torque curve, which is specified by the manufacturer at particular drive voltages and/or using their own drive circuitry. It is not guaranteed that you will achieve the same performance given different drive circuitry, so the pair should be chosen with great care.

Applications

Computer-controlled stepper motors are one of the most versatile forms of positioning systems. They are typically digitally controlled as part of an open loop system, and are simpler and more rugged than closed loop servo systems.

Industrial applications are in high speed pick and place equipment and multi-axis machine CNC machines often directly driving lead screws or ballscrews. In the field of lasers and optics they are frequently used in precision positioning equipment such as linear actuators, linear stages, rotation stages, goniometers, and mirror mounts. Other uses are in packaging machinery, and positioning of valve pilot stages for fluid control systems.

Commercially, stepper motors are used in floppy disk drives, flatbed scanners, computer printers, plotters, slot machines, and many more devices.

Webcam

A typical low-cost webcam used with many personal computers

A webcam is a video capture device connected to a computer or computer network, often using a USB port or, if connected to a network, ethernet or Wi-Fi.

Their most popular use is for video telephony, permitting a computer to act as a videophone or video conferencing station. This can be used in messenger programs such as Windows Live Messenger, Skype and Yahoo messenger services. Other popular uses, which include the recording of video files or even still-images, are accessible via numerous software programs, applications and devices.

They are well known for their low manufacturing costs and flexibility. Some, for example those used as online traffic cameras, are expensive, rugged professional-grade hardware.

With video interpreting, sign language interpreters work remotely with live video and audio feeds, typically at a relay call centre, so that the interpreter can see the deaf or mute party, and converse with the hearing party at the same time, and vice versa. Much like telephone interpreting, video interpreting can be used for situations in which no on-site interpreters are available. However, video interpreting cannot be used for situations in which all parties are speaking via telephone alone.

Webcams are also employed for security purposes. Software is available to allow PC-connected cameras to watch for movement and sound, recording both when they are detected; these recordings can then be saved to the computer, e-mailed or uploaded to the Internet. In one well-publicized case. a computer e-mailed out images as the burglar stole it, allowing the owner to give police a clear picture of the burglar's face even after the computer had been stolen.

Webcams typically include a lens , an image sensor, and supporting circuitry.

Webcams typically include a lens, an image sensor, and some support electronics. Various lenses are available, the most common being a plastic lens that can be screwed in and out to set the camera's focus. Fixed focus lenses, which have no provision for adjustment, are also available. As a camera system's depth of field is greater for small imager

formats and is greater for lenses with a large f/number (small aperture), the systems used in webcams have sufficiently large depth of field that the use of a fixed focus lens does not impact image sharpness much. Image sensors can be CMOS or CCD, the former being dominant for low-cost cameras, but CCD cameras do not necessarily outperform CMOS-based cameras in the low cost price range. Most consumer webcams are capable of providing VGA-resolution video at a frame rate of 30 frames per second. Many newer devices can produce video in multi-megapixel resolutions, and a few can run at high frame rates such as the PlayStation Eye, which can produce 320×240 video at 120 frames per second.

POWER SUPPLY

The term power supply is more commonly abbreviated to PSU

To provide a useable low voltage the PSU needs to do a number of things:-

Reduce the Mains AC (Alternating current) voltage to a lower level.

Convert this lower voltage from AC to DC (Direct current) Regulate the DC output to compensate for varying load (current

demand) Provide protection against excessive input/output voltages

Reduction of AC Mains

This is achieved by using a device known as a Transformer, an electromagnetic device consisting of an ferrous iron core which has a large number of turns of wire wound around it, known as the Primary Winding. The ends of these turns of wire being connected to the input voltage (in this case Mains AC).

A second number of turns of wire are wound around the Primary Winding, this set being known as the Secondary Winding.

The difference between the number of turns provides us with a way of reducing (in our case) a high AC voltage to a lower one.

Conversion of AC to DC

To convert our now low AC voltage to DC we use a Rectifier Diode connected to the Secondary Winding.

This is a silicon diode, only allows current to flow in one direction)

As our low AC voltage will be working at a frequency of 50Hz (Mains AC frequency) it is desirable to reduce the inherent hum on this to a lower level.

This is achieved by a technique known as Smoothing (“Ironing” out the bumps in the AC).

A simple way to reduce the hum is to use Full Wave Rectification.

Regulation of Output Voltage

In a simple PSU the easiest way to provide regulation to compensate for varying load conditions is to use a pair of relatively high value Electrolytic Capacitors.

Their values in this case being in the region of 470uF to 2000uF .

One of these capacitors is connected across the DC output of the rectifier diode(s) or bridge, this capacitor also providing an extra degree of smoothing the output waveform.

The second capacitor is connected via a low value, medium to high wattage resistor, which assists in limiting the current demand.

Voltage Regulator

Regulator, usually having three legs, converts varying input voltage and produces a constant regulated output voltage. They are available in a variety of outputs.   The most common part numbers start with the numbers 78 or 79 and finish with two digits indicating the output voltage. The number 78 represents positive voltage. The 78XX series of voltage regulators are designed for positive input. The LM78XX series typically has the ability to drive current up to 1A. The component has three legs: Input leg which can hold up to 36VDC Common leg (GND) and an output leg with the regulator's voltage. For maximum voltage regulation, adding a capacitor in parallel between the common leg and the output is usually recommended.

PCB ETCHING

Etching is the process where the excess copper is removed to leave the individual tracks or traces as they are sometimes called.

Many different chemical solutions can be used to etch circuit boards. Ranging from slow controlled speed etches used for surface preparation to the faster etches used for etching the tracks. Copper etching is normally exothermic. Almost all etching solutions liberate toxic corrosive fumes, extraction is highly recommended. All etchants are corrosive and toxic, mainly due to the high metal content.

Ferric Chloride

It is an old favorite chemical very good at staining fingers, clothing, etc brown. Etch rate can be very high but is dependant on solution movement over the surface of the board and temperature. At 70C using Spray etching, 1oz copper is removed in a little under a minute, normal etching temperature is more likely to be 45C.

When 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.

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.

1. FeCl3 + Cu > FeCl2 + CuCl2. FeCl3 + CuCl > FeCl2 + CuCl2

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

3. CuCl2 + Cu > 2CuCl

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.

SOLDERING

Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a relatively low melting point. Soft soldering is characterized by the melting point of the filler metal, which is below 400 °C (800 °F). The filler metal used in the process is called solder.

In a soldering process, heat is applied to the parts to be joined, causing the solder to melt and be drawn into the joint by capillary action and to bond to the materials to be joined by wetting action. After the metal cools, the resulting joints are not as strong as the base metal, but have adequate strength, electrical conductivity, and water-tightness for many uses. Soldering is an ancient technique mentioned in the Bible and there is evidence that it was employed up to 5000 years ago in Mesopotamia.

The only tools that are essential to solder are a soldering iron and some solder.

There are, however,

lots of soldering accessories available

soldering iron solder

The software

The software program for the user interface to control the robot (Mobile robot.exe) is designed in Visual Basic 5.0. The core file used by software is 'inpout32.dll,' which can be downloaded from 'www.logix4u.net' for free. The .dll file uses a kernel-mode driver. Therefore this software works as good with NT-based Windows OS as with Win XP and Win 2000. A separate program module for the inpout32.dll is used along with the main program of the mobile robot For details about the .dll file, visit 'www.logix4u net'.

The software uses timer controls to produce delay in between the counting sequence that controls the speed of the stepper motors. The value of timer delay can be increased or decreased with the help of timers defined in the source code. Data port (D0 through D7) of parallel port LPT1 with base address of 0x0378 is used to connect the PC to the motors. The base address is defined in the source Program. Install the webcam/camera driver software in your system and ensure that the camera executable file is located under 'C' drive. Here, for Quantum Hi-Tech camera, the executable file is 'amcap.exe.' Run the Mobile robot.exe program. On clicking the 'View Picture' button the program will get connected to *re executable file of the webcam and run automatically. If you have any other webcam, change the path and filename in the source code and make the executable file of the same for running the application. Current date and time and present status of the buttons pressed (move forward and backward and turn right and left) are also displayed on the screen at software runtime.

The relevant program for the Pc-BASED MOBILE ROBOT FOR NAVIGATION is shown below:

Private Sub Commandl _Click ( )

Unload Me

End sub

Private Sub Command2 _C1ick ( )

Label4.caption = “Turn Left”

Timerl . Interval = sliderl . Value

Timerl.Enabled = True

Timer2.Enabled = False

Timer3.Enabled = False

Timer4.Enabled = False

End sub

Private Sub Command3 _Click ( )

Label4.caption = “Move Forward”

Timer2.Interval = slider1. Value

Timerl.Enabled = False

Timer2.Enabled = True Timer3.Enab1ed = False

Timer4.Enabled = False

End sub

Private Sub Command4_ Click ( )

Label4.caption = “Move Backward”

Timer3 . Interval = slider1. Value

Timer1.Enabled= False

Timer2.Enabled = False

Timer3.Enabled = True

Timer4.Enabled = FaIse

End sub

Private Sub Command5_ Click ( )

Label4.caption = “Turn Right”

Timer4 . Interval = slider1. Value

Timer1.Enabled= False

Timer2.Enabled = Fa1se

Timer3.Enabled = Fa1se

Timer4.Enabled = True End sub

Private Sub Command6 _Click ( )

Label4.caption = “Robot is Stopped”

Timer1.Enabled= False

Timer2.Enabled = Fa1se

Timer3.Enabled = Fa1se

Timer4.Enabled = Fa1se

End sub

Private Sub Command7 _Click ( )

Dim aks as Integer

aks = S h e l l ( "C:\WINDOW \Amcap.exe”, vbMaximizedFocus )

End sub

Private Sub Command8_ Click ( )

frmAbout . Show

End Sub

Private Sub Sliderl_ Click ( )

Timerl. Interval = Sliderl . Value

Timer2. Interval = Sliderl . Value Timer3. Interval = Sliderl . Value

Timer4. Interval = Sliderl . Value

Text1.Text = 1000 - Sliderl . value

End Sub

Private Sub Sliderl _scroll ( )

Timerl. Interval = Sliderl . Value

Timer2. Interval = Sliderl . Value

Timer3. Interval = Sliderl . Value

Timer4. Interval = Sliderl . Value

End Sub

Private sub Timerl _Timer ( )

Static a As integer

b = 2 ^ a

Out &H378, 17 * b

a = a + 1

If a > 3 Then

a = 0

End if End Sub Private sub Timer2 _Timer ( )

Static a As integer

b = 2 ^ a

If b = 1 Then

Out &H378 , 24

ElseIf b = 2 Then

Out &H378 , 36

ElseIf b = 4 Then

Out &H378 , 66

ElseIf b = 8 Then

Out &H378 , 129

End If

a = a + 1

If a > 3 Then

a = 0

End if

End Sub Private sub Timer3 _Timer ( )

Static a As integer

b = 2 ^ a

If b = 8 Then

Out &H378 , 24

ElseIf b = 4 Then

Out &H378 , 36

ElseIf b = 2 Then

Out &H378 , 66

ElseIf b = 1 Then

Out &H378 , 129

End If

a = a + 1

If a > 3 Then

a = 0

End if

End Sub

Private sub Timer4 _Timer ( ) Static a As integer

b = 2 ^ ( 3-a )

Out &H378, 17 * b

a = a + 1

If a > 3 Then

a = 0

End if

End Sub

Private sub Timer5 _Timer ( )

Label9.caption = Times

Label13.caption = Dates

End sub

PROBLEMS FACED

. Non availability of IC data sheets

. Burning of components

. Burning of PCB tracks

. Voltage fluctuations

. Fault in PCB layouts

. Non availability of capacitors & Resistors of exact values

. Improper functioning of web camera.

REFRENCES

1. M.Morris Manno, “Digital Design”, Pearson Publication,

Singapore.

2. R.P. Jain, “Digital Electronics”, Tata McGraw Hill, New-Delhi.

3. J.B.Gupta, “Theory and Performance of Electrical Machines”,

S.K. Kataria and Sons , New Delhi

4. Muhammad Ali Mazidi and Janice Gillispie Mazidi, “The 8051

Microcontroller and Embedded Systems”, Pearson Education,

New Delhi

5. “Electronics For You”, Magazine, October 2008.

6. www.alldatasheets.com

7. www.en.wikipedia.org