OMEGA Electronics B.tech Training File

OMEGA ELECRONICS

Introduction Omega electronics is established in the year 1962 by Physics and Electronics scholar Mr. Y.P. Agarwal Electronics has more than three decades experience in manufacturing of various electronics instruments and teaching aids. The company is renowned manufacturer of digital instruments, electronic instruments, science experimental training boards, computer logic training boards, dynamic demonstration boards, power electronic training and many more instruments and training aids. Company clients list includes major companies, engineering colleges, institutions and government/private sector organizations. Omega Electronics is manufacturer, exporter and supplier of a range of antenna training equipments, breadboard training equipments, communication training equipments, instrumentation training equipments and decade box and power supply equipments. Omega electronics follows international standards and procedures and is an ISO9001:2000 company.

2 Omega Electronics broad based ranges of educational training equipments are based used in educational institutes worldwide. Omega Electronics is an eminent manufacturer and exporter of more than 1300 educational trainers, scientific equipments and lab practical equipments. Omega Electronics’ scientific lab equipments, educational & training equipments have become much popular in the educational, academics, research and industrial circles. Cost effective, customized and OEM production capacity makes itself the foremost exporter to South-East Asia, North-America and Africa. Apart from this Omega’s training division, “EDUCARE” organizes Training Workshops, Project Assistance and Practical lab for Physics, Electronics and Communication for other colleges. Omega Electronics manufactures a whole range of Antenna-trainers, Instrumentation trainers, Communication trainers, LAN trainer, VLSI trainers, Microprocessor, Micro-controller & Interfaces trainers, Consumer electronics Demonstration trainers, Test and Measuring Instruments, Micro Test Benches, Educational Wall Charts, Robotics Kits, Decade Boxes (R,L,C), Analog Electronics Lab, Digital Electronics Lab, Power Electronics Lab, Breadboards Trainers, Power Project Board, Circuit Lab Trainers, Physics Experimental Set Ups, Fiber Optics Trainers, Power Supplies, etc. Omega Training Systems are presently being exported to various countries in Asia, Africa & America. Omega Electronics is one of the leading manufacturer of Educational Trainers kits and Scientific Equipments. Omega Training Systems are presently being exported to various countries in Asia, Africa & America.

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Different Departments in company

3 The company has the following departments:

(a) Mechanical Department(b)Production Department(c) Testing Department(d)Research & Development Department

The details regarding these departments are as follows-

Mechanical Department

4 Mechanical department further has many subdivisions where various operations are done with the help of different machines. In the mechanical department, cabinet bodies of the products are manufactured and then various components like transformers, voltmeters, ammeters, etc. are assembled on the cabinets. Various tools and machines are required for different purposes like cutting, drilling, welding, sharpening, flattening and fitting. In the Transformer Winding subdivision transformers are made. Different types of transformers are made for different applications, e.g., Step-Up/Down Transformer, Pulse Transformer, Current Transformer, Impedance Transformer, Auto Transformer, Power Transformer and Constant Voltage Transformer.

Manufacturing Department

5 Printed panels and PCBs are sent to this section and here components are assembled on them by soldering process. After that, the final circuit connections are made and the rest of the wiring is done. Once the educational kit is manufactured it is transferred to the Quality Control Department.

Quality Control Department

6 After the fabrication of the instruments, they are sent to the Quality Control Department for multi level checking of the proper functioning of hardware and software of the instrument .The engineers’ team in the quality control section keeps an eye on the quality of the instrument to attain high level accuracy and minimizes the chances of malfunctioning of the instrument and provides the customer years of maintenance-free usage of the instrument.

Testing Team

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7 After working with the manufacturing team, we became the part of testing team. Testing involves both the testing of the finished goods as well as some important purchased components used in making these training boards. We tested a variety of training kits like Computer Trainer, Logic Trainer, Microprocessor Trainer, Microcontroller trainer, AM/FM Trainer, Oscillators etc. Among the purchased goods we were made to test the functioning of IC’s, regulator, Sensors etc.

During the testing of finished goods, every component used in the kit is tested individually. Experiments related to the kit are performed and the kit is calibrated accordingly. After the kit is tested and certified, it is ready to go to the Packaging Section.

The ICs to be used in the kits are tested in two ways depending upon the IC’s:- (a) Direct Testing - It involves testing of commonly used non-programmable IC’s such as: 7495, 7476, 74121 etc. Functionality of these IC’s can be directly checked with the help of a Digital IC Function Tester. (b) Indirect Testing - It involves testing of IC’s by placing them in their characteristic circuits, performing the experiments and judging them on the basis of the results. Apart from this, Programmable IC’s such as 2C512, 2716, AT89C51 (Microcontroller IC) etc. are tested and programmed with the help of computer software.

Research & Development Team

8 Finally we worked with the R&D Team. R&D plays a major role in the growth of the company. This segment includes the design and development of new products in accordance with upcoming technologies. Working as a part of this team, we worked in the design and development of various products like Transformer winding kit, RFID Trainer kit, Antenna Trainer, AM / FM Trainer etc.

Basic Electronic Components

Resistors

9 Resistors are components that have a predetermined resistance. Resistance determines how much current will flow through a component. Resistors are used to control voltages and currents. A very high resistance allows very little current to flow. Air has very high resistance.

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Current almost never flows through air. (Sparks and lightning are brief displays of current flow through air. The light is created as the current burns parts of the air.) A low resistance allows a large amount of current to flow. Metals have very low resistance. That is why wires are made of metal. They allow current to flow from one point to another point without any resistance. Wires are usually covered with rubber or plastic. This keeps the wires from coming in contact with other wires and creating short circuits. High voltage power lines are covered with thick layers of plastic to make them safe, but they become very dangerous when the line breaks and the wire is exposed and is no longer separated from other things by insulation.

10 Resistance is given in units of ohms. (Ohms are named after Mho Ohms who played with electricity as a young boy in Germany.) Common resistor values are from 100 ohms to 100,000 ohms. Each resistor is marked with colored stripes to indicate its resistance. 

TYPES OF RESISTORS

(1) FIXED RESISTORS

A fixed resistor is one in which the value of its resistance cannot change.Fixed resistors are off different types:-

(a) CARBON FILM RESISTORS

11 This 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. Metal film resistors are recommended for use in analog circuits. The physical size of the different resistors are as follows.

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From the top of the photograph1/8W1/4W1/2W

Rough size

Rating power(W)

Thickness(mm)

Length(mm)

1/8 2 3

1/4 2 6

1/2 3 9

of the same value, all in one package. One side of each resistor is connected with one side of all the other resistors inside. One example of its use would be to control the current in a circuit powering many light emitting diodes (LEDs). This resistor is called a Single-In-Line(SIL) resistor network. It is made with many resistors.

(b)METAL FILM RESISTOR

12 Metal 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. I don't use any high tolerance resistors in my circuits. Resistors that are about ±1% are more than sufficient. 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.

(2) Variable Resistors

Variable resistors are also common components. They have a dial or a knob that allows you to change the resistance. This is very useful for many situations. Volume controls are variable resistors. When you

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change the volume you are changing the resistance which changes the current. Making the resistance higher will let less current flow so the volume goes down. Making the resistance lower will let more current flow so the volume goes up. The value of a variable resistor is given as its highest resistance value. For example, a 500 ohm variable resistor can have a resistance of anywhere between 0 ohms and 500 ohms. A variable resistor may also be called a potentiometer (pot for short).

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SOME EXAMPLES

1st digit - Brown = 1, 2nd digit - Black = 0, 3rd digit - Black = 0, Multiplier - Brown = 1 (one zero must to add), and Brown = ±1% or 1000 ±1%  =  1x103 ±1%  =  1k ±1%

Examples:                1.    Red, Red, Black, Gold,  Brown           

                        2  ,  2  ,    0  , x10-1, 1%  =  22.0         2.    Brown, Red, Red, Red, Brown             

                          1  ,   2 ,   2  ,  2  ,    2%  = 12200  = 12.2x103  = 12.2k   

Capacitors

13Now suppose you want to control how the current in your circuit changes (or not changes) over time. Now why would you? Well radio

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14 signals require very fast current changes. Robot motors cause current fluctuations in your circuit which you need to control. What do you dowhen batteries cannot supply current as fast as you circuit drains them? How do you prevent sudden current spikes that could fry your robot circuitry?

15 Capacitors are like electron storage banks. If your circuit is running low, it will deliver electrons to your circuit. In our water analogy, think of this as a water tank with water always flowing in, but with drainage valves opening and closing. Since capacitors take time to charge, and time to discharge, they can also be used for timing circuits. Timing circuits can be used to generate signals such as PWM or be used to turn on/off motors insolarpoweredBEAMrobots.Quick note, some capacitors are polarized, meaning current can only flow one direction through them. If a capacitor has a lead that is longer than the other, assume the longer lead must always connect to positive.

Power surge /drainage management

16 The problem with using robot components that drain a large amount of power is sometimes your battery cannot handle the high drain rate, Motors and servos being perfect examples. This would cause a system wide voltage drop, often resetting your microcontroller, or at least causing it to not work properly. Just a side note, it is bad to use the same power source for both your circuit and your motors. So don't do it. Or suppose your robot motors are not operating at its full potential because the battery cannot supply enough current, the capacitor will make up for it. The solution is to place a large electrolytic capacitor between the source and ground of your power source. Get a capacitor that is rated at least twice the voltage you expect to go through it. Have it rated at 1mF-10mF for every amp required. For example, if your 20V motors will use 3 amps, use a 3mF-30mF 50V rated capacitor. Exactly how much will depend on how often you expect your motor to change speed and direction, as well as momentum of what you are actuating. Just note that if your capacitor is too large, it may take a long time to charge up when you first turn your robot on. If it is too small, it will drain of electrons and

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your circuit will be left with a deficit. It is also bad to allow a large capacitor to remain fully charged when you turn off your robot. Some things could accidentally short and fry. So use a simple power on LED in your motor circuit to drain the capacitor after your robot is turned off. If your capacitor is not rated properly for voltage, then can explode with smoke. Fortunately they do not overheat if given excessive amounts of current. So just make sure your capacitor is rated higher than your highest expected. Capacitors can also be used to prevent power spikes that could potentially fry circuitry. Next to any on/off switch or anything that that could affect power suddenly should have a capacitor across it?

17 Capacitors can eliminate switch bouncing. When you flip a mechanical switch, the switch actually bounces several times within a microsecond range. Normally this is too small of a time for anyone to care (or even notice), but note that a microcontroller can take hundreds of readings in a single microsecond. So if your robot was counting the number of times a switch is flipped, a single flip can count as dozens. So how do you stop this? Use a small ceramic capacitor! Just experiment until you find the power capacitance value.

Introduction to Robotics

18 In practical usage, a Robot is a mechanical device which performs automated physical tasks, either according to direct human supervision, a pre-defined program, or a set of general guidelines using artificial intelligence techniques. Robots are typically used to do the tasks that are too dirty, dangerous, difficult, repetitive or dull for humans. This usually takes the form of industrial robots used in manufacturing lines. Other applications include toxic waste cleanup, underwater and space exploration, mining, search and rescue, and mine finding. Recently however, robots are finding their way into the consumer market with uses in entertainment, vacuum cleaning, and lawn mowing. A robot may include a feedback-driven connection between sense and action, not under direct human control, although it may have a human override function. The action may take the form of electro-magnetic motors or actuators (also called effectors) that move an arm, open and close grips, or propel the robot. The step by step control and feedback is provided by a computer program run on either an external or embedded computer or a microcontroller. By this definition, a robot may include nearly all automated devices.

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19 Ask a number of people to describe a robot and most of them will answer they look like a human.  Interestingly a robot that looks like a human is probably the most difficult robot to make.  It is usually a waste of time and not the most sensible thing to model a robot after a human being.  A robot needs to be above all functional and designed with qualities that suit its primary tasks.  It depends on the task at hand whether the robot is big, small, is able to move or nailed to the ground.  Each and every task means different qualities, form and function; a robot needs to be designed with the task in mind.

Mobile Robots

Mars Explorer image

    Mobile robots are able to move, usually they perform task such as search areas. A prime example is the Mars Explorer, specifically designed to roam the mars surface. Mobile robots are a great help to such collapsed building for survivors Mobile robots are used for task where people cannot go.  Either because it is too dangerous of because people cannot reach the area that needs to be searched.  

Rolling Robots

Rolling robots have wheels to move around.  These are the type of robots that can quickly and easily search move around.  However they are only useful in flat areas, rocky terrains give them a hard time.  Flat terrains are their territory.   

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   Walking Robots

  Robots on legs are usually brought in when the terrain is rocky and difficult to enter with wheels.  Robots have a hard time shifting balance and keep them from tumbling.  That’s why most robots with have at least 4 of them, usually they have 6 legs or more.  Even when they lift one or more legs they still keep their balance.  Development of legged robots is often modeled after insects or crawfish..  

Stationary Robots

Robots are not only used to explore areas or imitate a human being.  Most robots perform repeating tasks without ever moving an inch.  Most robots are ‘working’ in industry settings.  Especially dull and repeating tasks are suitable for robots.  A robot never grows tired, it will perform its duty day and night without ever complaining.  In case the tasks at hand are done, the robots will be reprogrammed to perform other tasks..  

Autonomous Robots

Autonomous robots are self supporting or in other words self contained.  In a way they rely on their own ‘brains’. Autonomous robots run a program that give them the opportunity to decide on the action to perform depending on their surroundings.  At times these robots even learn new behavior.  They start out with a short routine and adapt this routine to be more successful at the task they perform.  The most successful routine will be repeated as such their behavior is shaped. 

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Remote-control Robots

   An autonomous robot is despite its autonomous not a very clever or intelligent unit.  The memory and brain capacity is usually limited. An autonomous robot can be compared to an insect in that respect. In case a robot needs to perform more complicated yet undetermined tasks an autonomous robot is not the right choice. Complicated tasks are still best performed by human beings with real brainpower.  A person can guide a robot by remote control.  A person can perform difficult and usually dangerous tasks without being at the spot where the tasks are performed.  To detonate a bomb it is safer to send the robot to the danger area.  

Virtual Robots

20 Virtual robots don’t exits in real life.  Virtual robots are just programs, building blocks of software inside a computer.  A virtual robot can simulate a real robot or just perform a repeating task.  A special kind of robot is a robot that searches the world wide web.  The internet has countless robots crawling from site to site. These WebCrawler’s collect information on websites and send this information to the search engines.    Another popular virtual robot is the chatterbot.  These robots simulate conversations with users of the internet.  One of the first chatterbots was ELIZA.  There are many varieties of chatterbots now, including E.L.V.I.S.

BEAM Robots

21 BEAM is short for Biology, Electronics, Aesthetics and Mechanics.  BEAM robots are made by hobbyists. BEAM robots can be simple and very suitable for starters.

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Basic Robots Constituents

Sensors

INFRARED EMITTER DETECTOR

Basic Description

22 The infrared emitter detector pair act as an eye with a flashlight in the infrared spectrum. The detector (a transistor) detects all ambient infrared light. The emitter (a LED) emits infrared light into an otherwise dark (in the infrared spectrum) room.

Availability and Cost

23 It is easily available anywhere, very cheap. Requirments

Power Requirements

24 Low, typical LED power requirements.

Tips and Uses

(a) Don’t bother using this circuit outside, the sun will flood your IR detector and make it useless.

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(b)Certain indoor lighting can also emit IR interference (c) Only if you modulate the IR emitter and set the detector to only

detect modulated IR can you use this outside. This is commonly done with Sharp IR rangefinders.

(d)Tweaking is necessary to determine sensitivity of your circuit. Sensitivity will help increase range but also increase ambient interference.

(e) By using certain resistor values, your IR emitter detector can also detect color, such as for line tracking.

Sonar

Basic Description

25 Detects obstacles and can determine object softness/hardness through echolocation. Typical sonar require ground, power, signal transmit, and signal recieve lines. Transmit a short square wave and the sonar emits a mostly inaudible sound. The sonar keeps the signal recieve line low before the emission and after detecting the return of the emission, high. The distance can be determined by measuring in time how long the recieve line is kept high. FYI, the speed of sound at sea level is 340.29 m/s.

Availability and Cost

26 Available online for around $20-$30.

Power Requirements

27 Low, but depends on how active sonar are set to.

Tips and Uses

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(a) Using multiple sonar can be a challenge in that they can trigger each other inadvertently.

(b) If using multiple sonar, you must trigger each independently and wait for a return.

(c) This can take a long time if you have 10+ sonar on your robot, so you will have to fiddle with combinations of sonar running simultaneously

(d) Sonar does not work at very short distances (several inches)

(e) sound bounces off of walls and can interfere with later emission readings.

DIGITAL COMPASS

Basic Description

28 The digital compass gives measurements based on Earth's magnetic field for robot navigation. Inside this commonly available MEMS are tiny nano-structures that bend due to electromagnetic fields. When this MEMS experiences any form of EM field, the tiny structures bend by an amount which can be electrically detected. Cheaper digital compasses usually have a resolution of around +/- 5 degrees, but newer and better ones can detect with a better accuracy.

Availability and Cost

29 It is easily available for $30-$100. It is best to buy them with supporting circuitry included to avoid any interference from bad electrical design.

Power Requirements

30 Minimal, typical logic only.

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Tips and Uses

31 Keep digital compasses far away from anything that emits EM, such as motors, transformers, inductors, etc. Large conductive items significantly altar magnetic fields (cars, fridges, steel plates, etc.)

SENSORS - ACCELEROMETER

Basic Description

32 It detects motion, vibration, and angle with respect to gravity. Inside this commonly available MEMS are tiny nano-structures that bend due to momentum and gravity. When this MEMS experiences any form of acceleration (gravity is a downward acceleration) the tiny structures bend by an amount which can be electrically detected. This means accelerometers can be used to detect and/or control for vibration of a device, acceleration of a robot actuator, or even the angle of the accelerometer. Note that an accelerometer works on only a single axis, so if you wish to detect on X, Y, and Z planes you need 3 of them. Today many accelerometer MEMS's come with multiple axis for simplicity.

Availability and Cost

33 They are easily available and very affordable. Usually require support circuitry. Dimension Engineering has a great plug and play dual axis accelerometer which requires no additional support circuitry.

Power Requirements

34 Minimal, typical logic only.

Tips and Uses

(a) Placing an accelerometer on a mobile robot that experiences bumps can trigger the accelerometer unintentionally.

(b)Use a large capacitor to smooth out output over several hundred milliseconds (testing required) to prevent this.

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Types of Motors

DC Motors

35 From the start, DC motors seem quite simple. Apply a voltage to both terminals, and it spins. But what if you want to control which direction the motor spins? Correct, you reverse the wires. Now what if you want the motor to spin at half that speed? You would use less voltage. But how would you get a robot to do those things autonomously? How would you know what voltage a motor should get? Why not 50V instead of 12V? What about motor overheating? Operating motors can be much more complicated than you think. DC motors are non-polarized - meaning that you can reverse voltage without any bad things happening. Typical DC motors are rated from about 6V-12V. The larger ones are often 24V or more. But for the purposes of a robot, you probably will stay in the 6V-12V range. So why do motors operate at different voltages? As we all know (or should), voltage is directly related to motor torque. More voltage, higher the torque. But don't go running your motor at 100V because that’s just not nice. A DC motor is rated at the voltage it is most efficient at running. If you apply too few volts, it just wont work. If you apply too much, it will overheat and the coils will melt. So the general rule is, try to apply as close to the rated voltage of the motor as you can. Also, although a 24V motor might be stronger, do you really want your robot to carry a 24V battery (which is heavier and bigger) around? So a standard recommendation is do not surpass 12V motors unless you really need the torque.

Stepper Motors

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36 Stepper Motors work under a very similar principle to DC motors, except they have many coils instead of just one. So to operate a stepper motor, one must activate these different coils in particular patterns to generate motor rotation. So stepper motors need to be sent patterned commands to rotate. These commands are sent as high and low logic over several lines, and must be pulsed in a particular order and combination. Steppers are often used because each 'step,' separated by a set step angle, can be counted and used for feedback control. For example, a 10 degree step angle stepper motor would require 36 commands to rotate 360 degrees. However external torque can force movement to a different step, invalidating feedback. Therefore external torque must never exceed the holding torque of a stepper.

37 The Robocore can control up to 2 stepper motors using its standard dc motor connections. To follow this example attaches pin 1 and 2 to the Robocore's first motor output and pins 3 and 4 to the second motor output. The two ground pins can be connected together and attached to the batteries negative terminal.

The following sequence steps the motor through one complete cycle.

The motor can be made to rotate anticlockwise by stepping backwards through the sequence. I.E. Step 4, 3, 2,1,4,3 etc .

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ROBOT BATTERIES

About Batteries

38 The robots are no longer limited to bulky low power non-rechargeable batteries, and today there is a large assortment to suit your robots' demands. How are batteries rated? With any battery you will see a voltage and a power rating. Battery voltages can be somewhat complicated. When fully recharged, a battery will often be 15% above its voltage rating.

39 When fully discharged, about 15% below its rating. A fully charged battery will also immediately drop below its rating when driving heavy loads, such as a DC motor. To increase battery voltage, wire multiple of them in series. Batteries also cannot supply an infinite current. So expect batteries of different types but equal voltages to have different current outputs. To increase battery current output, wire multiple of them in parallel. This is why batteries often come in assembled packs of smaller cells. So when using a battery, make sure your circuit handles changes in battery voltage. For the power rating you will see something like 1200mAh. mAh means milliamps per hour. So if it is 1200mAh, that means the battery can supply 1.2 amps for one hour or 2.4 amps for 30 minutes or 0.6 amps for two hours.

40 Alkaline batteries are the most common, easiest to get, and cheapest too. However they are useless, dont buy them. They have low power capacities, are heavy, have trouble supplying large amounts of current in

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short time periods, and get expensive to constantly replace. The same goes for Zinc-carbon batteries, which suck even more.

Interesting points about Robotics

41 Building robots involves the development of a wide range of skills, including creative thinking, design, mechanics, electronics and programming - all of which are highly valued in industry. Our interest in the subject could lead us into an exciting and fulfilling career at the cutting edge of technology!

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42 Before the 1960s, robot usually meant a manlike mechanical device (mechanical man or humanoid) capable of performing human tasks or behaving in a human manner. Today robots come in all shapes and sizes, including small robots made of LEGO, and larger wheeled robots that play robot football with a full-size ball.

43 What many robots have in common is that they perform tasks that are too dull, dirty, delicate or dangerous for people. Usually, we also expect them to be autonomous, that is, to work using their own sensors and intelligence, without the constant need for a human to control them. Looked at this way, a radio controlled aero plane is not a robot, nor are the radio controlled combat robots that appear on television. However, there is no clear dividing line between fully autonomous robots and human-controlled machines. For example, the robots that perform space missions on planets like Mars may get instructions from humans on Earth, but since it can take about ten minutes for messages to get back and forth, the robot has to be autonomous during that time.

Where did the word robot originate?

44 The word robot was introduced in 1920 in a play by Karel Capek called R.U.R. or Rossum's Universal Robots. Robot comes from the Czech word robota, meaning forced labour or drudgery. In the play, human-like mechanical creatures produced in Rossum's factory are docile slaves. Since they are just machines, the robots are badly treated by humans. One day a misguided scientist gives them emotions, and the robots revolt, kill nearly all humans and take over the world. However, because they are unable to reproduce themselves, the robots are doomed to die.

What are the Laws of Robotics?

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45 The term robotics was coined in the 1940s by science fiction writer Isaac Asimov. In a series of stories and novels, he imagined a world in which mechanical beings were mankind's devoted helpmates. They were constrained to obey what have become known as Asimov's Laws of Robotics:

(a)A robot may not injure a human being, or, through inaction, allow a human being to come to harm.

(b)A robot must obey the orders given it by human beings except where such orders would conflict with the First Law.

(c) A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.

What was the first practical robot?

46 A prototype industrial robot arm named Unimate (designed by George Devol and Joseph Engelberger) was sold to General Motors in 1959. It plucked hot automobile parts out of a die-casting machine and quenched them in water.

47 The 1960s and 1970s saw a revolution in manufacturing as robots replaced humans for many repetitive jobs. However, these robots were not intelligent by today’s standards. Usually they were programmed by humans training their movements, and they had very little decision-making capabilities. There are still many robots like this in factories today, but the trend is towards more intelligent general-purpose robots that can do more than just paint a panel or screw in a bolt.

What can't robots do?

48 It is very difficult to give a robot the ability to perform a wide variety of tasks, move around in cluttered surroundings, recognize objects in the ‘real world’, understand normal speech, and think for itself. These are exciting areas of current research in robotics and artificial intelligence.

Will robots ever be as good as humans?

49 Many futurists believe that robots will eventually and inevitably become more capable than humans, but some experts in artificial intelligence assert that machines will never be able to develop the consciousness and

emotions needed for reasoning and creativity. There are already commercially available robots that can live in our houses and

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do basic chores for us. Robots are very good at processing certain kinds of information, and they are ideally suited to answering the telephone and being controlled over the Internet.

50 The International RoboCup Federation has set itself the challenge of having a team of humanoid robot football players beat the human world champions by 2050. Can you image that? It means that robots will have to become as nimble and skilful as Beckham. It will require the invention of many new materials – for example, a human soccer player could be badly hurt if it clashed with a robot made of metal. It will also require an enormous improvement in machine vision. If you play sports such as football, tennis, or even snooker, next time you play think about the huge amount of information that comes through your eyes.

Will robots take over from humans?

51 This is a popular science fiction theme, and the answer depends on whether robots will ever attain consciousness and emotions. In stories like 2001: A Space Odyssey and Terminator, humans always find a way to outwit intelligent machines that try to take over control. That's fiction, however, and fact is often stranger than fiction!

52 The suggestion that robots will take over because they might become more intelligent than humans overlooks one critical fact: the people who have power in human societies are usually not the most intelligent in the obvious, intellectual way. They have different kinds of ‘human intelligence’, including the ability to understand other people, and to influence their behavior.

53 The sensible answer to the question as to whether robots will take over is that they probably won’t in the near future. There are many reasons for this. The first is that the robots of today have puny brains compared to humans, and they do not have the ability to organise in the same way as humans. Our societies are very complex and allow us to achieve many very advanced things. It is unlikely that robots could overtake us in the near future. Even so, it is something that we should keep an eye on, since all scientists have a responsibility not to do things that damage society. However, for the most part, robots play a very positive role in our

societies, and we can expect them to be used in many ways that make life better for us all.

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Printed circuit board

54 PCBs are boards whereupon electronic circuits have been etched. PCBs are rugged, inexpensive, and can be highly reliable. They require much more layout effort and higher initial cost than either wire-wrapped or point-to-point constructed circuits, but are much cheaper and faster for high-volume production. Much of the electronics industry's PCB design, assembly, and quality control needs are set by standards that are published by the IPC organization.

55 The inventor of the printed circuit was the Austrian engineer Paul Eisler (1907–1995) who, while working in England, made one circa 1936 as part of a radio set. Around 1943 the USA began to use the technology on a large scale to make rugged radios for use in World War II. After the war, in 1948, the USA released the invention for commercial use. Printed circuits did not become commonplace in consumer electronics until the mid-1950s, after the Auto-Sembly process was developed by the United States Army.

56 Before printed circuits (and for a while after their invention), point-to-point construction was used. For prototypes, or small production runs, wire wrap or turret board can be more efficient.

57 Originally, every electronic component had wire leads, and the PCB had holes drilled for each wire of each component. The components' leads were then passed through the holes and soldered to the PCB trace. This method of assembly is called through-hole construction. In 1949, Moe Abramson and Stanislaus F. Danko of the United States Army Signal Corps developed the Auto-Sembly process in which component leads were inserted into a copper foil interconnection pattern and dip soldered. With the development of board lamination and etching techniques, this concept evolved into the standard printed circuit board fabrication process in use today. Soldering could be done automatically by passing the board over a ripple, or wave, of molten solder in a wave-soldering machine. However, the wires and holes are wasteful since drilling holes is expensive and the protruding wires are merely cut off. In recent years, the use of surface mount parts has gained popularity as the

demand for smaller electronics packaging and greater functionality has grown.

How to Make Printed Circuit Boards (PCB's)

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58 There are two main methods for the hobbyist to make PCB's.  The first is how most people start; by laying down special etch resistant transfers onto clean copper board and then etching the board in a bath of ferrous chloride solution. The second is to produce the artwork (foils) for the PCB layout using a PC software application, and then to transfer the track pattern to the copper board using a technique similar to developing and printing a photograph.  Both methods are quite straightforward, but the latter method, which is more expensive but quicker, produces better results and allows more dense population of the PCB.

Method

59 here are six main steps to making a PCB, which are shown in the graphic below. Clicking on each of the steps will provide more information.  At the foot of this page is a downloadable version of these pages.

Preparing the Artwork

60 Using PCB Layout Software:  There are a large number of suppliers of PCB layout applications, which run on a PC, who regularly advertise each month in magazines such as Elektor.   These range in price considerably depending on the functions and complexity (i.e.: number of layers, pads and size of library) available. I have always used Proteus (Ares and Isis) from Lab center Electronics.

61 The method is usually to open the layout application and using the library of packages provided, select all the component packages to be used in the layout (i.e.: DIL_8, TO_92, RES_30, DIL_20, CAP_20, CONN_SIL4 etc).   These packages are then placed in their rough positions on the board area and their pins connected together as required by clicking and dragging using the mouse.

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The screen shot on the right shows the Ares Layout Software Tool in use.

62 This can be time consuming, and you have to be very careful to connect the pins together correctly as there is no checkinmechanism.Alternatively, the circuit can be entered in an accompanying schematic capture application and the pcb layout can be laid out automatically using the supplied auto-router.  I have never been able to justify the expense of this luxury and have always used the manual method!

63 When the artwork is finished, the layers (usually top and bottom) are printed onto either acetate film (if you can afford it) or good quality tracing paper available from art shops (70gsm - A4 sheets usually).  It is better NOT to reverse (mirror) the image for the bottom layer as I will explain under 'Developing'.  When using tracing paper, I leave the ink to dry for an hour or so, then sandwich between several sheets of A4 paper with some heavy books (such as electronic component catalogues) on top, to flatten the artwork, over night.

64 Using transfers:  This is a very slow method, which I used for many years and good quality results can still be obtained, using etch resistant transfers available from many electronic component suppliers.

65 The general method is to create the layout on a piece of paper (using different colored pens for the layers) and then to trace the holes and tracks (including the board edge) onto tracing paper for each layer.  After taping the artwork to the thoroughly cleaned copper board a centre punch is used to mark the position of the holes.   If there are both top and bottom layers, four of the marked holes can be drilled through (one near each corner) at this stage, to line up the layers correctly.With a lot of patience, it should now be possible to 'join the dots' with the etch resist transfers, until the artwork is completed.  Great care should be taken to keep finger marks off of the copper surface and to complete this process as soon as possible, before the copper oxidizes.

Developing the Artwork

66 Pre-Sensitized boards:  These are relatively expensive, but you get what you pay for and results can be excellent and quick.  The boards are supplied with black plastic covering the surfaces to protect the Ultra-violet (UV) sensitive surfaces and this covering is removed immediately prior to using.

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If the board is to be doubling sided, then before removing the plastic, four pilot holes can be drilled, as mentioned before, to assist lining up the layers.  Tip! :- If the bottom foil was NOT reversed when printing (as recommended), the printed side of the artwork will now be as close as possible to the copper surface.  This will result in sharper and better resolution for thin tracks, because the UV light has less opportunity to 'spread' within the thickness of the plastic film or tracing paper used for the foil.

67 The foils are affixed to the board with small pieces of adhesive tape. Tip! :- At this stage the artwork and pcb should be cut larger than the finished board by (say) 5mm all round.  The board is then placed in the UV exposure box for an appropriate amount of time to allow the pcb pattern to be transferred to the board.  Each side of the board is usually exposed separately when using non - professional equipment.  The photo' shows my light box with the Parallel Port Development Board Foil ready to be used.After exposure, the foils are carefully removed and the board placed in a solution of developer for a couple of minutes and the tracks and pads will magically appear, similar to developing a photograph. Caustic Soda can be used with the pre-sensitized boards and this is available from most hardware stores for cleaning drains etc.  It should be used in a well ventilated area.

68 As soon as the developing is complete, the board must be washed under cold running water but with care taken to avoid damaging the etch resist on the board surfaces, which will be very soft at this stage.  Etching should now be undertaken as soon as possible, but keeping the developer solution to one side for use again shortly.

69 Coated Boards:  A cheaper method is to use plain copper board and to apply a UV sensitive coating to it (after cleaning).  Electro lube sells such a coating which is applied from an aerosol spray under low light conditions.I have found this to be a very hit and miss process, where good

results are hard to obtain.  If this method is used, it is important for the same manufacturer’s developer to be used if the process is to work successfully.

Etching the Board

70 Great care should be taken with the Ferric Chloride while preparing, using and disposing of it.  This chemical (and to a lesser extent) the

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caustic soda developer solution, should be used in a well ventilated area.

71 Before etching begins, the artwork on the PCB should be inspected for damaged tracks and hairline cracks, which should be corrected using a 'Dalo' etch resist pen or similar.  If this is necessary, the board should first be dried off, as soon as possible after developing, with a hair ryer, for example.

72 I have found etching is best completed with the chemical heated to a little above room temperature, using a hot water- bath.  Etching should then take little more than 15 to 20 minutes with constant agitation of the board.  Leaving the etching bath floating in the hot water-bath makes agitation easy, but be careful not to splash the chemical about. When the PCB looks ready, it should be carefully removed from the chemical, using plastic gloves and thoroughly rinsed in a cold water bath.  After inspection, if it is finished then it should be returned to the caustic soda solution, to soften the resist, which can then be removed with a soft abrasive (e.g.: fine wet and dry paper).

73 However, I prefer to remove the resist at the end, after all other stages have been completed. The photo on the left shows some of the materials required for making your own PCB's. Caustic Soda for developing the artwork, FCC - Ferrous Oxide (etchant) and a tin of drills.

Cleaning the PCB

74 Cleaning the PCB, is perhaps easiest to do at this stage, as the etch resist is soft, but I prefer to complete the drilling and cutting of the board to size, first. Otherwise, a further, final session of cleaning will be needed later.

75 Transfers and etch resist is fairly easily removed with a medium density, waterproof, abrasive paper, that can be used under running water.  Only light pressure is needed, to avoid damaging the thinner copper tracks. This can be followed by use of a very fine paper to give a better finish. If an etch resist pen (such as a 'Dalo' marker pen) has been used, this is easily removed by using a solvent, such as nail polish remover! However, this can stain the pcb, if you are not careful to clean up the residue quickly.

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The picture, right, shows from top clockwise, the original art work, (printed on good quality tracing paper).   Then the exposed design before etching and finally, the etched layout ready for drilling and finishing.

Drilling the PCB

76 Most PCBs these days, contain a few IC's as a minimum, and this can quickly multiply the number of holes that need to be drilled.It is important, especially with dual sided boards, that the holes are drilled with the drill 'upright' so that the holes are lined up in the middle of the pads on both sides.  This is easy if you have a small bench drill which will fit into a pillar stand, but if you don't, what can you do?

77 I use a 12 volt modeler’s drill, which I hold in two hands above the board, and rest both wrists on the table surface.  I can then use the weight of both hands to hold the copper board down tight at the same time.  In this way I manage to hold everything rigid and am able to use light pressure to ease the drill through the board. A soft material should be placed under the board for the drill to pass into, such as a spare piece of cork or an old 'jiffy' bag!  Whatever method is used, it is important NOT to allow any sideways movement of the PCB (or the drill) if breakage of the drill bit is to be avoided.

78 The drills used, should be the Tungsten Carbide type (which usually have a larger shank) as these will not blunt as quickly as the ordinary metal HSS drills.  These are about three times as expensive, but if breakages are avoided, will work out at better value in the long run. I have found that it is best to use a range of drill sizes - 0.8mm for IC pads and most other components, 1.0mm for thicker component leads (diodes and regulators) and 1.2mm for some larger components.  The normal practice of drilling a pilot hole and then the final size later should not be

tried, as this will result in the snapping of the brittle Pcb drills, which tend to 'snatch' as they enter a pilot hole.  Therefore, drill each hole only once, with the correct sized drill.

Finishing the PCB

79 At last, the etching has been done, the holes have been drilled and the last task before soldering the components is to finish the PCB so that it looks as professional as possible. First, the oversize board can be cut to size, using a hacksaw or similar.  Make the saw cut just outside the

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copper board edge, to allow for filing/smoothing of the rough cut PCB edge.  Take care not to rub fingers and hands against the rough PCB edges, as the glass fibers are so fine, they can enter the body!  Similarly, do not breathe in dust generated when drilling, cutting or filing the board. The board should now be cleaned as described in the earlier page, but if this has already been completed, then a light rub over with a fine, waterproof, abrasive paper should be carried out. The board, with shiny copper tracks, is now ready for assembly and soldering.  After this has been completed, and basic functional testing carried out (to spot the stupid mistakes), the bottom surface should be coated with a protective lacquer, to prevent oxidization of the tracks, over time.  This should be done as soon as possible after component assembly.

80 A better approach (which does not always look so good!), is to 'tin' the copper tracks before component assembly.   This takes some practice, if a messy result is to be avoided, but the key to success is heat and flux! Smear a THIN layer of plumbers flux across the surface to be tinned, then using the soldering iron and the minimum possible solder, work the solder across the pads and along tracks as quickly as possible.  Avoid using too much heat on thinner tracks to avoid damaging them.  Finally, inspect the board for solder bridges between tracks and pads - a small magnifier may be useful for this task

81 The flux is messy and this is best removed using cellulose thinners, in a well ventilated area. Followed by a wash with soapy water.  A protective lacquer is not needed with tinned boards, but will enhance appearance, if applied to the finished board after components have been assembled and soldered.

Printed circuit board guidelines

82 Printed circuit board (PCB) is a component made of one or more layers of insulating material with electrical conductors. The insulator is typically made on the base of fiber reinforced resins, ceramics, plastic, or some other dielectric materials. During manufacturing the portions of conductors that are not needed are etched off, leaving printed circuits that connectelectroniccomponent.Currently the main generic standard for printed circuit board design, regardless of materials is IPC-2221A. Whether PCB board is single-sided, double-sided or multilayer, this standard provides rules for manufacturability and quality such as requirements for material

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properties, criteria for surface plating, conductor thickness, component placement, dimensioning and tolerance rules, and more. For a specific technology the designer can then choose the appropriate sectional standard from the IPC-2220 series.

83 The width of the circuit conductors should be chosen based on maximum temperature rise at rated current and acceptable impedance. The spacing between the PC traces is determined by peak working voltage, the coating and the product application. The minimum possible width of the traces and spacing between them are limited by the manufacturing capabilities of your fabricator and should not be less then 2 mils. IPC and other standards do not tell you how to properly route the board. Good PCB layout techniques require understanding of the effects of non-zero trace impedance and coupling of signals from one circuit to another through parasitic capacitances and radio transmission, as well as basic understanding of circuit operation. Auto-routing may be done for most parts of control circuits, but power, ground and high di/dt circuits should be routed by hand.

POWER SUPPLY84 Power supply can be define as an electronic equipment which is the

stable source of d.c. power for electronic circuits.

TYPES OF POWER SUPPLIES Power supplies can be classified into two major categries.

UNREGULATED POWER SUPPLIES85 These power supplies ,supply power to the load but do not take into

consideration the variation of power supply output voltage or current with

respect to the changes in a.c. mains voltage ,load current or temperature variations. The output voltage or current of an un regulated power supply changes with the change in a.c. mains voltage , load current and temperature.

REGULATED POWER SUPPLIES86 These power supplies are regulated over the change in source voltage or

load current i.e. its output parameters remain stable Regulated power supplies are of two types:-

CURRENT REGULATED POWER SUPPLIES 33

87 These are constants current supplies i.e. they supply constant current (irrespective of the voltage ) inspite of changes in load or input voltage .

VOLTAGE REGULATED POWER SUPPLIES88 These supplies supply constant output voltage (irrespective of current)

with respect to the variation in load or source input voltage.

UNREGULATED POWER SUPPLIES 89 Unregulated power supplies can be represented by a block diagram :-

a.c. input is applied to the primary of the transformer and the desired a.c. voltage is obtained from the secondary . This voltage is applied to the rectifier which converts a.c. into d.c. This d.c. output from the rectifier is of pulsating nature and is of no use. To smooth out this pulsating d.c. (ripples) filters are employed after rectifier .

RECTIFIERS90 Rectifiers use mainly diodes to converts a.c. into d.c. A few types of

rectifiers (single phase) along with wavefoms are as given :

HALF WAVE RECTIFIER

A half wave rectifier is as shown:

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91 The operation of the half wave rectifier can be explained as, the desired input to the rectifier is obtained from the transformer and when A is +ve with respect to B , diode is forward biased and conduction takes place giving output across load . On the other hand ,when A is –ve with respect to B , the diode is reverse biased and no conduction of current takes place in the circuit and hence we get d.c. at the output.

FULL WAVE RECTIFIER A full wave rectifier is as shown below :-

92 A full wave bridge rectifier on the basis that when A is +ve with respect to B diodes D1 and D3 are forward the direction shown. Now when A is –ve with respect to B , diodes D2 and D4 conducts and current flows through the diodes and load in the same direction as previous one giving rise to waveform .

REGULATED POWER SUPPLIES The block diagram of a regulated power supply is given below:-

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93 The regulated power supply comprises of an unregulated power supply,regulated through a regulator to provide d.c. power to the load Regulators regulate the unregulated power supply to provide constant voltage or constant current to the load irrespective of the changes in load or source voltage

VOLTAGE REGULATED POWER SUPPLIER They maintain constant voltage over the working range (irrespective of current) .A few types of voltage regulators are as given below:-

ZENER DIODE REGULATOR 94 A zener diode regulator are as shown below:-

As we know from the characterstics of zener diode that if the reverse voltage across it increases beyond that of zener breakdown voltage , breakdown takes place and current increases rapidly and voltage across the diode remains constant at zener breakdown voltage (Vz) .This property of zener diode is exploited to make zener diode voltage regulator .Zener breakdown voltage (Vz) of the diode is so relected as a little less than the unregulated power supply so that it is operated in breakdown region . The output voltage from such a regulator is the zener breakdown voltage (Vz) . When the input voltage increases or decreases , the relative increase or decrease in voltage is taken up by Rs and change in current can be afforded by diode without change in voltage across it. Similarly 36

change in load , changes current ,which is afforded by zener diode and the voltage across it remains constant.

EMITTER FOLLOWER REGULATOR OR SERIES PASS TRANSISTOR REGULATOR Emitter follower regulator is as shown below:

95 This circuitis an extension of the zener diode voltage regulator and has a bipolar transistor emitter follower at the output terminals . Zener diode in the circuit is operated in breakdown region and provide a constant voltage at the base of the emitter follower transistor . The emitter follows the base to supply the output current at the load terminals . The gain of transistor provides isolation of the zener diode from the load terminals .Any change in voltage from unregulated power supply comes across Rs and Rb since

voltage across zener diode is constant now as in an emitter follower , emitter follows base , output voltage also remains constant. Its advantages over zener diode regulator are better regulation , lower output resistance and capability of larger power output.

SHUNT TRANSISTOR VOLTAGE REGULATOR

In this circuit the transistor is in shunt with the load resistance.

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96 In the operation zener diode acts as a voltage reference source (diode operated in the breakdown region ) to bias the transistor .The output voltage of this circuit is maintained constant because as the unregulated DC input voltage or the load current changes it changes the biasing of the transistor nd the current drawn by the shunt transistor is varied in the way so as to maintain the output (load) voltage constant .The shunt regulator is not as efficient as the series regulator but it has advantage of greater economy and simplicity . In a shunt regulator ,the transistor passes all the current in the absence of load, which is a disadvantage over series type ,in which the transistor passes current only as long as the load is connected across its output and the current through it is the load current only.

THREE TERNMINAL VOLTAGE REGULATORS97 These are IC’s (integrated circuit) having three terminals ,namely input ,

output and ground leads ,to provide fixed output voltage over a range of input voltages and capable of delivering a certain maximum output current . Three terminals voltage regulators can be represented as

38 Diodes

98 Diodes are components that allow current to flow in only one direction. They have a positive side (leg) and a negative side. When the voltage on the positive leg is higher than on the negative leg then current flows through the diode (the resistance is very low). When the voltage is lower on the positive leg than on the negative leg then the current does not flow (the resistance is very high). The negative leg of a diode is the one with the line closest to it. It is called the cathode. The positive end is called the anode. Usually when current is flowing through a diode, the voltage on the positive leg is 0.65 volts higher than on the negative leg.

Switches

99 Switches are devices that create a short circuit or an open circuit depending on the position of the switch. For a light switch, ON means short circuit (current flows through the switch, and lights light up.) When the switch is OFF, that means there is an open circuit (no current flows, lights go out.

When the switch is ON it looks and acts like a wire. When the switch is OFF there is no connection.

LED

100 An LED is the device shown above. Besides red, they can also be yellow, green and blue. The letters LED stand for Light Emitting Diode. The important thing to remember about diodes (including LEDs) is that current can only flow in one direction.

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Transistor

101 Transistors are basic components in all of today's electronics. They are just simple switches that we can use to turn things on and off. Even though they are simple, they are the most important electrical component. For example, transistors are almost the only components used to build a Pentium processor. A single Pentium chip has about 3.5 million transistors. The ones in the Pentium are smaller than the ones we will use but they work the same way.

Transistors that we will use in projects look like this:

102 The transistor has three legs, the Collector (C), Base (B), and Emitter (E). Sometimes they are labeled on the flat side of the transistor. Transistors always have one round side and one flat side. If the round side is facing you, the Collector leg is on the left, the Base leg is in the middle, and the Emitter leg is on the right.

Transistor Symbol

103 The following symbol is used in circuit drawings (schematics) to represent a transistor.

 Basic Circuit

The Base (B) is the On/Off switch for the transistor. If a current is flowing to the Base, there will be a path from the Collector (C) to the

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Emitter (E) where current can flow (The Switch is On.) If there is no current flowing to the Base, then no current can flow from the Collector to the Emitter. (The Switch is off.) Below is the basic circuit we will use for all of our transistors.

Relays

104 A relay is usually an electromechanical device that is actuated by an electrical current. The current flowing in one circuit causes the opening or closing of another circuit. Relays are like remote control switches and are used in many applications because of their relative simplicity, long life, and proven high reliability. They are used in a wide variety of applications throughout industry, such as in telephone exchanges, digital computers and automation systems.

How do relays work?

105 All relays contain a sensing unit, the electric coil, which is powered by AC or DC current. When the applied current or voltage exceeds a threshold value, the coil activates the armature, which operates either to

close the open contacts or to open the closed contacts. When a power is supplied to the coil, it generates a magnetic force that actuates the switch mechanism. The magnetic force is, in effect, relaying the action from one circuit to another. The first circuit is called the control circuit; the second is called the load circuit. A relay is usually an electromechanical device that is actuated by an electrical current. The current flowing in one circuit causes the opening or closing of another circuit.

Types of Relays There are two basic classifications of relays:

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(1)Electromechanical Relay (2)Solid State Relay.

Electromechanical relays have moving parts, whereas solid state relays have no moving parts. Advantages of Electromechanical relays include lower cost, no heat sink is required, multiple poles are available, and they can switch AC or DC with equal ease.

(1)Electromechanical Relays

(a) General Purpose Relay106 The general-purpose relay is rated by the amount of current its switch

contacts can handle. Most versions of the general-purpose relay have one to eight poles and can be single or double throw. These are found in

computers, copy machines, and other consumer electronic equipment and appliances.

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(b) Power Relay107 The power relay is capable of handling larger power loads – 10-50

amperes or more. They are usually single-pole or double-pole units.

(c) Contactor108 A special type of high power relay, it’s used mainly to control high

voltages and currents in industrial electrical applications. Because of these high power requirements, contactors always have double-make contacts.

(d) Time-Delay Relay109 The contacts might not open or close until some time interval after the

coil has been energized. This is called delay-on-operate. Delay-on-release means that the contacts will remain in their actuated position until some interval after the power has been removed from the coil. A third delay is called interval timing. Contacts revert to their alternate position at a specific interval of time after the coil has been energized. The timing of these actions may be a fixed parameter of the relay, or adjusted by a knob on the relay itself, or remotely adjusted through an external circuit.

(2)Solid State Relays

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110 These active semiconductor devices use light instead of magnetism to actuate a switch. The light comes from an LED, or light emitting diode. When control power is applied to the device’s output, the light is turned on and shines across an open space.On the load side of this space, a part of the device senses the presence of the light, and triggers a solid state switch that either opens or closes the circuit under control. Often, solid state relays are used where the circuit under control must be protected from the introduction of electrical noises.

Advantages of relays

(a) Relays can switch AC and DC, transistors can only switch DC. (b) Relays can switch high voltages, transistors cannot. (c) Relays are a better choice for switching large currents (> 5A). (d) Relays can switch many contacts at once.

Disadvantages of relays: (a) Relays are bulkier than transistors for switching small currents. (b) Relays cannot switch rapidly (except reed relays), transistors can

switch many times per second. (c) Relays use more power due to the current flowing through their

coil. (d) Relays require more current than many chips can provide, so a

low power transistor may be needed to switch the current for the relay's coil.

Microcontrollers The 8051 Microcontroller

Overview

111 The 8051 family of micro controllers is based on an architecture which is highly optimized for embedded control systems. It is used in a wide variety of applications from military equipment to automobiles to the

keyboard on your PC. Second only to the Motorola 68HC11 in eight bit processors sales, the 8051 family of microcontrollers is available in a wide array of variations from manufacturers such as Intel, Philips, and Siemens. These manufacturers have added numerous features and peripherals to the 8051 such as I2C interfaces, analog to digital converters, watchdog timers, and pulse width modulated outputs. 44

Variations of the 8051 with clock speeds up to 40MHz and voltage requirements down to 1.5 volts are available. This wide range of parts based on one core makes the 8051 family an excellent choice as the base architecture for a company's entire line of products since it can perform many functions and developers will only have to learn this one platform.

The basic architecture consists of the following features:

112 One 8051 processor cycle consists of twelve oscillator periods. Each of the twelve oscillator periods is used for a special function by the 8051 core such as op code fetches and samples of the interrupt daisy chain for pending interrupts. The time required for any 8051 instruction can be computed by dividing the clock frequency by 12, inverting that result and multiplying it by the number of processor cycles required by the instruction in question. Therefore, if you have a system which is using an 11.059MHz clock, you can compute the number of instructions per second by dividing this value by 12. This gives an instruction frequency of 921583 instructions per second. Inverting this will provide the amount of time taken by each instruction cycle (1.085 microseconds).

(a) an eight bit ALU(b) 32 discrete I/O pins (4 groups of 8) which can be individually

accessed(c) two 16 bit timer/counters(d) full duplex UART(e) 6 interrupt sources with 2 priority levels(f) 128 bytes of on board RAM(g) separate 64K byte address spaces for DATA and CODE memory

Memory Organization

113 The 8051 architecture provides the user with three physically distinct memory spaces which can be seen in Figure A - 1. Each memory space consists of contiguous addresses from 0 to the maximum size, in bytes, of the memory space. Address overlaps are resolved by utilizing instructions

which refer specifically to a given address space. The three memory spaces function as described below.

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Figure A - 1 - 8051 Memory Architecture

The CODE Space

114 The first memory space is the CODE segment in which the executable program resides. This segment can be up to 64K (since it is addressed by 16 address lines). The processor treats this segment as read only and will generate signals appropriate to access a memory device such as an EPROM. However, this does not mean that the CODE segment must be implemented using an EPROM. Many embedded systems these days are using EEPROM which allows the memory to be overwritten either by the 8051 itself or by an external device. This makes upgrades to the product easy to do since new software can be downloaded into the EEPROM rather than having to disassemble it and install a new EPROM.

115 Additionally, battery backed SRAMs can be used in place of an EPROM. This method offers the same capability to upload new software to the unit as does an EEPROM, and does not have any sort of read/write cycle limitations such as an EEPROM has. However, when the battery supplying the RAM eventually dies, so does the software in it. Using an SRAM in place of an EPROM in development systems allows for rapid downloading of new code into the target system. When this can be done, it helps avoid the cycle of programming/testing/erasing with EPROM’s, and can also help avoid hassles over an in circuit emulator which is

usually a rare commodity. In addition to executable code, it is common practice with the 8051 to store fixed lookup tables in the CODE segment. To facilitate this, the 8051 provides instructions which allow rapid access to tables via the data pointer (DPTR) or the program counter with an offset into the table optionally provided by the accumulator. This means that oftentimes, a table's base address can be loaded in DPTR and the 46

element of the table to access can be held in the accumulator. The addition is performed by the 8051 during the execution of the instruction which can save many cycles depending on the situation.

The DATA Space

116 The second memory space is the 128 bytes of internal RAM on the 8051, or the first 128 bytes of internal RAM on the 8052. This segment is typically referred to as the DATA segment. The RAM locations in this segment are accessed in one or two cycles depending on the instruction. This access time is much quicker than access to the XDATA segment because memory is addressed directly rather than via a memory pointer such as DPTR which must first be initialized. Therefore, frequently used variables and temporary scratch variables are usually assigned to the DATA segment. Such allocation must be done with care, however, due to the limited amount of memory in this segment. Variables stored in the DATA segment can also be accessed indirectly via R0 or R1. The register being used as the memory pointer must contain the address of the byte to be retrieved or altered. These instructions can take one or two processor cycles depending on the source/destination data byte.

117 The DATA segment contains two smaller segments of interest. The first sub segment consists of the four sets of register banks which compose the first 32 bytes of RAM. The 8051 can use any of these four groups of eight bytes as its default register bank. The selection of register banks is changeable at any time via the RS1 and the RS0 bits in the Processor Status Word (PSW). These two bits combine into a number from 0 to 3 (with RS1 being the most significant bit) which indicates the register bank to be used. Register bank switching allows not only for quick parameter passing, but also opens the door for simplifying task switching on the 8051.

118 The second sub-segment in the DATA space is a bit addressable segment in which each bit can be individually accessed. This segment is referred to as the BDATA segment. The bit addressable segment consists of 16

bytes (128 bits) above the four register banks in memory. The 8051 contains several single bit instructions which are often very useful in control applications and aid in replacing external combinatorial logic with software in the 8051 thus reducing parts count on the target system. It should be noted that these 16 bytes can also be accessed on a "byte-wide" basis just like any other byte in the DATA space.

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Interfacing of Seven Segment with Parallel port

Apparatus

119 Seven segment C-5611, Parallel Port Connector cord, Jumper Wires Bread Board.

Procedure

1. Open windows 98 as OS 2. Connect the male connector of the parallel port cord to the PC 3. Now connect the Female Connector of cord with seven

segment C-5611 as shown in table.

Table: Connection between Seven Segment and Female Connector

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Table: Relationship of decimal No. , Segment Display

Seven Segment Pin No.

Female Connector Pin No.

1 6

2 5

3 19

4 4

5 9

6 3

7 2

8 20

9 7

10 8

and Hexadecimal Equivalent

Pin out of seven segment

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Embedded Systems

Introduction

120 An embedded system is a special-purpose system in which the computer is completely encapsulated by the device it controls. Unlike a general-purpose computer, such as a personal computer, an embedded system performs pre-defined tasks, usually with very specific requirements. Since the system is dedicated to a specific task, design engineers can optimize it, reducing the size and cost of the product. Embedded systems are often mass-produced, so the cost savings may be multiplied by millions of items.

121 Handheld computers or PDAs are generally considered embedded devices because of the nature of their hardware design, even though they

are more expandable in software terms. This line of definition continues to blur as devices expand.

Examples of embedded systems(a) automatic teller machines (ATMs)(b) avionics, such as inertial guidance systems, flight control

hardware/software and other integrated systems in aircraft and missiles

(c) cellular telephones and telephone switches(d) computer equipment such as routers and printers(e) engine controllers and antilock brake controllers for automobiles(f) home automation products, like thermostats, air conditioners,

sprinklers, and security monitoring systems(g) handheld calculators(h) household appliances, including microwave ovens, washing

machines, television sets, DVD players/recorders(i) medical equipment(j) handheld computers(k) videogame consoles

122 The first recognizably modern embedded system was the Apollo Guidance Computer, developed by Charles Stark Draper at the MIT Instrumentation Laboratory. Each flight to the moon had two. They ran the inertial guidance systems of both the command module and LEM.

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At the project's inception, the Apollo guidance computer was considered the riskiest item in the Apollo project. The use of the then new monolithic integrated circuits, to reduce the size and weight, increased this risk.The first mass-produced embedded system was the Autonetics D-17 guidance computer for the Minuteman missile, released in 1961. It was built from discrete transistor logic and had a hard disk for main memory. When the Minuteman II went into production in 1966, the D-17 was replaced with a new computer that was the first high-volume use of integrated circuits.

Characteristics

123 Embedded systems are designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Some also have real-time performance constraints that must be met, for reason such as safety and usability; others may have low or no performance requirements, allowing the system hardware to be simplified to reduce costs. For high volume

systems such as portable music players or mobile phones, minimizing cost is usually the primary design consideration. Engineers typically select hardware that is just “good enough” to implement the necessary functions. For example, a digital set-top box for satellite television has to process large amounts of data every second, but most of the processing is done by custom integrated circuits. The embedded CPU "sets up" this process, and displays menu graphics, etc. for the set-top's look and feel.

124 The software written for embedded systems is often called firmware, and is stored in ROM or Flash memory chips rather than a disk drive. It often runs with limited hardware resources: small or no keyboard, screen, and little RAM memory. Embedded systems reside in machines that are expected to run continuously for years without errors and in some cases recover by them if an error occurs. Therefore the Software is usually developed and tested more carefully than that for Personal computers, and unreliable mechanical moving parts such as Disk drives, switches or buttons are avoided. Recovery from errors may be achieved with techniques such as a watchdog timer that resets the computer unless the software periodically notifies the watchdog.

User interfaces

125 Embedded systems range from no user interface at all - dedicated only to one task - to full user Interfaces similar to desktop operating systems in devices such as PDAs. In between are devices with small character- or

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digit-only displays and a few buttons. Therefore usability considerations vary widely. On larger screens, a touch-screen or screen-edge soft buttons also provides good flexibility while minimizing space used. The advantage of this system is that the meaning of the buttons can change with the screen, and selection can be very close to the natural behavior of pointing at what's desired.

Conclusion

126 An engineer must have a good practical as well as theoretical knowledge. He must be technically sound as book knowledge is incomplete. The technical training was an educative as well as interactive. We learned how to make the people learn. Technical lectures presented by the professional technicians related to topics like Robotics, Assembly language were really interesting and healthy to learn the industrial trends.

The additional activities such as a session on Aptitude questions and presentations related to the topics provided the chance for overall development of an engineer. It made us learn about the importance of teamwork.

127 Omega electronics provides a good base for student who need to gain knowledge in technical field with it’s training program known as educare. The students are made familiar to complex instrument and kits. So that it can assist them in future .Omega is a world leader in exports. The finished products with its business spreaded in more then 25 countries. The major strength of OMEGA, regarding its production & training is its more capable team of technicians & workers which always been the major part of its image in international market. Training at OMEGA is like a milestone in our way of learning the production or manufacturiug of the products which we are usiny in almost each of our experiments. OMEGA is well equipment with heavy & light machinery for its production which are in best supervision of its technicians & employes and is more in favour of students like us. Omega has its own production plant which is well equipped with almost each and every required machinery and assemblies for manufacturing purposes. This factor is likely to be the most essential for increasing the efficiency and interest of the people associative with Omega. These all machineries and assemblies are tested and checked at regular instances to maintain the efficiency and also for the security and surety. Laboratory instruments and equipments are also provided to technicians for the innovative and more efficient workings in their respective field.

128 OMEGA is a well known name in the field of export & sales of electronic equipments & trainer kits. A determined & hardworking bulk of over 40 people in production of various electronic products. with over 1400 products. Being exported to more than 30 countries, OMEGA is a well known & everywhere trusted institution. OMEGA has achieved this landmark with its quality control measures. It was an 150 9001: 2000 company & follows all of the international standards for quality control regarding its products. The EDUCARE training program of OMEGA for students in technical field & higher education provides a good platform for practical training & to understand the basic & complex concepts of electronic equipments & kits. A fair and educational environment at Omega helps the students like us to learn the basics of electronic equipments and components to be used at appropriate places and also to mount and their calibration. The industrial training arranged for us has been proved to be beneficial in context of our knowledge and experience. It provides a good platform for students of technical field and higher

education with its innovated technicians who are always committed to give the best products for welfare of the company and their importers.

129 Omega electronics is a true platform to initiate the step towards professionalism in an engineer’s life. Omega has its own production plant which is well equipped with almost each and every required machinery and assemblies for manufacturing purposes. This factor is likely to be the most essential for increasing the efficiency and interest of the people associative with Omega. These all machineries and assemblies are tested and checked at regular instances to maintain the efficiency and also for the security and surety. Laboratory instruments and equipments are also provided to technicians for the innovative and more efficient workings in their respective fields