Principles of Engineering in Communications

1. Principles of Engineering in Communications Engineering Concepts

2. Communications History of Communications • 1450 Johannes Gutenberg builds the movable printing press. • 1826 Joseph Niepce of produces the wrold’s first permanent photographic image. • 1876-Alexander Graham Bell introduced telephone. • 1877 Thomas Edison patents the phonograph. • 1891 Thomas Edison and William Dickson invent the kinetoscope. • 1895 Guglielmo Marconi develops the wireless telegraph • 1925 John Logie Baird transmits the first television signal. • 1954 The transister radio or tubeless radios become available in the USA • 1990 The world wide web is created in Europe. It’s chief architect is Tim Berners-Lee.

3. Communications • Assignment 1: • Have students pick one form of communication technology and develop a PowerPoint presentation to be presented to the class (See Communication Systems PowerPoint Project) • Assignment 2: • Fill in the Principles of Engineering in Communicationsvocabulary sheet as we go through this unit. Use the PowerPoint, textbook, and any other resources to complete the worksheet.

4. Communications • Communication is the ability to send and receive messages. • People to people • People to machine • Machine to people • Machine to machine

5. Communications • Messages are intended to: • Inform – news papers, TV news casts • Educate – texts, video, DVD’s, internet. • Persuade - advertising • Control – machines and tools such as Computer Numeric Control: A type of programmable control system, directed by mathematical data, which uses microcomputers to carry out various machining operations; such as a mill or lathe.

6. Communications • All Communications include a message, a sender, a communication channel, and a receiver. • A communication channel is the path over which a message must travel to get from the sender to the receiver.

7. Communications

8. Communications • The telegraph by Samuel Morse. • Sent electronic signals using wires. • Morse devised a language with a series of long and short signals that represented letters and numbers. • Video: Telegraph Machine

9. Communications • Morse code Assignment 3: Using an old set of walkie talkies, send a classmate a message using Morse Code.

10. Communications Video: Digital vs. Analog

11. Communications • Electronics Components in Communication • Transmission systems… • Copper Wire: Many older phones consist of two thin insulated copper wires twisted around each other. • Coaxial Cable: Carry many more messages all at once than twisted-pair wire. Consists of an outer tube made of a material that conducts electricity (usually copper). Inside the tube is an insulated central conductor (also copper). Several of these cables are combined into one bundle.

12. Communications • Optical Fibers: thin fibers of pure glass that carry signals in the form of pulses of light. Each optical fiber is surrounded by a reflective cladding and an outside protective coating. The light pulses are converted to electronic signals.

13. Communications • Microwaves can be used to carry phone conversations over long distances. Microwaves are very short electromagnetic waves that travel through the atmosphere and make communication without connecting wires possible. • In cell phones, sound waves are changed into microwaves. They are transmitted using an antenna (sent and received) and converted back to sound waves.

14. Communications CIRCUITS VOLTAGE & CURRENT

15. Circuits, Voltage & Current • PARTS OF A CIRCUIT • An electric circuit is a combination of parts connected from a complete path through which electrons can move. • The purpose of a circuit is to make use of energy of moving electrons. • Therefore a circuit is a system of parts, or components by which electric energy can be changed into other forms of energy.

16. Circuits, Voltage & Current • HEAT, LIGHT & MAGNETISM • A basic complete circuit has four parts: • The energy source • the conductors • the load • and the control device.

17. Circuits, Voltage & Current Conductor Wires Light Energy Source Battery Switch

18. Circuits, Voltage & Current • ENERGY SOURCES • Produces the force that causes electrons to move. • Similar to a pump that forces water through a pipe. • In electricity, this force is called voltage or electromotive force. • Chemical Cells and electromagnetic generators.

19. Circuits, Voltage & Current • Because electrons are negatively charged, they are attracted by positive charges and repelled by negative charges. • If two charged objects are connected by a conducting material such as wire, electrons will flow from the negative object to the positive object. • The flow of electrons is called current.

20. Circuits, Voltage & Current • To produce a continuous electric current in the wire, energy must be supplied continuously. • Electrons are not used up as they move through a circuit. • Therefore the number of electrons that return to the positive terminal of the power source equals the number of electrons that leave the negative terminal of that energy source.

21. Circuits, Voltage & Current - - - - + + + + + + + + - - - - + - POS. CHARGED OBJECT NEG. CHARGED OBJECT

22. Circuits, Voltage & Current - - + + + + - - - + + - + + - - - + FLOW OF ELECTRONS NEG. CHARGED OBJECT POS. CHARGED OBJECT

23. Circuits, Voltage & Current • CONDUCTORS • in a circuit, conductors provide an easy path through which electrons can move through the circuit. • Copper is the most commonly used conductor metal. • Fashioned into wire or channels, copper wire may be bare or covered with some kind of insulating material.

24. Circuits, Voltage & Current • The insulation wire provides a method to prevent the conductors (wires) from touching each other or some other conducting surface. • It prevents a short. • In some circuits, metal objects other than copper conductors form the conducting paths.

25. Circuits, Voltage & Current • Laminated circuit boards or bread boards are conductors. • Lets look at the bread board.

26. Circuits, Voltage & Current • Breadboards are used for testing and experimenting with electronic circuits. • They are very convenient since all you have to do is plug in the components. • On the surface of a breadboard, there are many holes for plugging in components:

27. Circuits, Voltage & Current • The bread board has many strips of metal which run underneath the board that connects the component. The metal strips are laid out as shown below:

28. Circuits, Voltage & Current • Each strip is a connection. So whichever components connected to a certain strip are connected to each other. • The blue strips shown in the illustration are usually used for connecting the batteries and the green strips are for the components.

29. Circuits, Voltage & Current • LOAD • The part of the circuit that changes the energy of moving electrons into some other useful form of energy. • A light bulb is a very common circuit load. • As electrons move through the filament of the lamp, the energy of the electrons in motion is changed into heat energy and light energy.

30. Circuits, Voltage & Current • Loads can be connected into a circuit in series and parallel or in series-parallel combinations. • A series circuit provides only one path or one loop through which electrons can move from one terminal of the energy source to the other.

31. Circuits, Voltage & Current • In a parallel circuit there may be two or more different paths, or loops. • A series-parallel circuit has a combination of both parallel and series circuits in a single circuit.

32. Circuits, Voltage & Current • CONTROL DEVICE: • The mechanical wall switch is an example of a simple circuit control. • When the switch is in the on position, it acts as a conductor to keep electrons flowing continuously through the circuit. • The circuit is said to be CLOSED or a closed loop.

33. Circuits, Voltage & Current • When the switch is in the off position, the circuit path is interrupted. • Electrons can no longer move through the circuit. • The circuit is said to be OPEN or an open loop. • Different types of control devices.

34. Circuits, Voltage & Current • VOLTAGE: • As stated earlier, the energy that forces electrons through a circuit is called the electromotive force. • The EMF is measured in units called volts. • It is referred to voltage. • Most homes operate on 120. • A common flashlight battery produces 1.5 volts

35. Circuits, Voltage & Current • CURRENT: • The movement of electrons is called current. • It is measured in amperes or amps. • One ampere of current is equal to one coulomb (6,240 quadrillion) of electrons passing past any point in a circuit during one second of time.

36. Circuits, Voltage & Current • A 100 watt light bulb requires about .8 amps of current to operate. • Most starters in cars use 200 amps when it is switched on. • VOLTAGE AND CURRENT REQUIREMENTS: • Sources od energy must be able to do two things. • Supply the voltage • Deliver the current as required by the device.

37. Circuits, Voltage & Current • You can connect 8 flashlight dry cells together in such a way as to form a battery that produces 12 volts. • However you would never get the car to start with this energy source. • In order to do that a larger battery also producing 12 volts but having a much larger current-delivering capacity must be used.

38. Circuits, Voltage & Current • It is important to know both the voltage and current requirements are often given on the name plates attached to these products. • DIRECT CURRENT (dc) • Is produced in a circuit by a steady voltage source.

39. Circuits, Voltage & Current • That is, the positive and negative terminals, or poles, of the voltage source do not change their charges over time. • These terminals are said to have fixed polarity. • Therefore the direction of the current does not change over time. • Such a voltage is provided by electric cells, batteries and dc generators.

40. Circuits, Voltage & Current • DC may be constant, or steady, in value. • The current also may be varying or pulsating. • The applied voltage and the nature of the load determine the kind of direct current supplied.

41. Circuits, Voltage & Current • ALTERNATING CURRENT (ac) • produced by a voltage source that changes polarity, or alternates, with time. • The current moves in one direction and then another direction over time. • The most common source is a an alternating current generator or alternator.

42. Circuits, Voltage & Current • For purposes of our project we will be using DC power.

43. Circuits, Voltage & Current • RESISTANCE • To better understand what resistance is, you must first get an idea of how electrons flow. • When an electron is knocked out of an atom, it will fly off and hit another atom. If the electron strikes the atom with enough force, it will knock off another electron. The atom that was just knocked off will hit another atom and so forth.

44. Circuits, Voltage & Current • Note that every time an electron strikes another, it is transferring its energy. Some of the energy is converted into heat every time it is transferred. • The voltage will drop as the energy is transferred over long distances. • Thus a long wire has a higher resistance than a short wire.

45. Circuits, Voltage & Current • Some materials - such as copper and silver - does not hold on to its electrons very tightly. • Therefore it doesn't require much energy to knock off an electron. • These materials are called conductors and has a very low resistance to electron flow.

46. Circuits, Voltage & Current • Materials such as clay and plastics hold on to their electrons more tightly than conductors. It takes more energy to knock off an electron from these materials. These materials are called insulators and has a high resistance to electron flow. • Now, you must understand that this is NOT how electrons really flow; It serves only as something for you to work with. To really know how electrons flow, which we will not get into, you will need to study quantum physics

47. Circuits, Voltage & Current • Resistance is represented by the letter R. • The basic unit of measure is ohm or the symbol (Greek omega).

48. Circuits, Voltage & Current • OHM’S LAW • Ohm's law is one of the most important concepts in electronics. Fortunately it's only a very simple mathematical relationship between current, voltage, and resistance. • According to the Ohm's law, voltage equals current times resistance which is expressed in the following equation: • E=IR • where E = voltage, I = current, and R = resistance

49. Circuits, Voltage & Current • For example, ifI = 0.1AR = 10kthen E = 0.1 * 10kE = 1000 voltsSee excel spreadsheet: Ohms Law • Note: "k" stands for "thousands". So 10k = 10,000 ohm

50. Circuits, Voltage & Current • COMPONENTS • Resistors are one of the most commonly used components in electronics. • As its name implies, resistors resist the flow of electrons. • They are used to add resistance to a circuit.