1. Chapter 4 Electricity and Power Supplies

2. You Will Learn…  How electricity is measured  How to protect your computer system against damaging changes in electrical power  About different form factors and computer cases  How to detect and correct power supply problems  About Energy Star specifications

3. Electricity: Basic Introduction

4. Measures of Electricity continued… Page 121

5. Measures of Electricity

6. Voltage  Measures potential differences  Electrical force created by the potential difference in electron charge flowing between 2 points  Measured in units called volts  Negative to positive flow  Measures when power is on Voltmeter: Page 122

7. Voltage

8. Amps  Ampere = unit of measurement for electrical current  Amps remain constant throughout electrical system  Current: volumn of electrons flowing through an electrical system Ammeter

9. Relationship Between Voltage and Current  Direct relationship As the electrical potential difference (voltage) increases, the electrical current increases As the voltage decreases, the current decreases

10. Ohms  Standard unit of measurement for electrical resistance  Resistors are devices used in electrical circuits to resist the flow of electricity  As resistance decreases, electricity increases Paragraph Page 124

11. Relationship Among Voltage, Current, and Resistance  Voltage and current have a direct relationship When voltage increases, current increases  Resistance has an inverse relationship with voltage and current As resistance increases, either current or voltage decreases As resistance decreases, either current or voltage increases (Ohm’s Law) V=I/R or Volts = Amps/Ohms  One volt drives a current of one amp through a resistance of one ohm

12. Wattage  Total amount of power needed to operate an electrical device  Measured in watts  Calculated by multiplying volts by amps in a system (W = V x A)

13. AC and DC  AC (alternating current) Means of sending power over extended distances Cycles back and forth rather than traveling in only one direction Most economical way to transmit electricity  DC (direct current) Travels in only one direction Type of current required by most electronic devices, including computers Computer power supplies function as both a transformer and a rectifier Device that changes ratio of current to voltage (reduces voltage to a usable level) Device that converts AC to DC

14. Computer Power Supply Hertz (Hz):

15. Power Supply Function Rectifier Chapter questions 2-6

16. Hot, Neutral, and Ground

17.  Hot: inbound current  Neutral: outbound current  Ground: protection for neutral line against short circuits  Short circuit Occurs when electricity is allowed to flow uncontrolled from hot line to neutral line or from hot line to the ground  Fuse Designed to prevent too much current from flowing through the circuit Rated in amps Paragraph 127

18. Hot, Neutral, and Ground 128

19. Hot, Neutral, and Ground Receptacle tester

20. Materials Used to Make Electronic Components  Conductors: easily conducts electricity (gold or copper)  Insulators: resists flow of electricity (glass or ceramic)  Semiconductors: falls between conductors & insulators—ability to conduct electricity when charge is applied (silicon) 129

21. Some Common Electronic Components Device serves as a gate or switch for electrical signal & can amplify the flow Device that can hold electrical charge for period of time & smooth the uneven flow through a circuit 130

22. Protecting Your Computer System  General safety precautions  Protecting against electricity  Protecting against electrostatic discharge (ESD or static electricity) and electromagnetic interference (EMI)  Surge protection and battery backup

23. Protecting Against Electricity  When working inside a computer Turn off the power Unplug the computer Use a ground bracelet 131

24. Static Electricity  Ground yourself and computer parts, using static control devices or methods Ground bracelet or static strap Ground mats Static shielding bags  Caution: Don’t wear a ground bracelet when working inside a monitor or with high-voltage equipment such as a laser printer

25. Using a Ground Bracelet

26. Using a Ground Bracelet and a Ground Mat

27. Using Static Shielding Bags

28. Electromagnetic Interference  Caused by the magnetic field produced as a side effect when electricity flows  Radio frequency interference (RFI) can cause problems with radio and TV reception  Use a line conditioner to filter electrical noise causing the EMI 135

29. Surge Protection and Battery Backup  Devices that filter AC input Surge suppressors (or surge protectors): protect against sudden changes in power level Power conditioners Uninterruptible power supply (UPS) Also provides backup power Tips on 136 Alters power to provide continuous voltage

30. Uninterruptible Power Supply  Benefits Condition line for brownouts and spikes Provide backup power during a blackout Protect against very high spikes that could damage equipment Spikes: temporary voltage surges Brownouts: temporary voltage reductions

31. Uninterruptible Power Supply

32. What to Consider When Buying a UPS  Cost  Rating should exceed your total VA or wattage output by at least 25%  Degree of line conditioning  Warranty, service policies, and guarantee

33. UPS Manufacturers 138

34. Computer Case and Form Factors  Form factor Describes the size, shape, and general makeup of a hardware component Must match for motherboard, power supply, and case

35. Case, Power Supply, and Motherboard Form Factors  AT  ATX (most popular)  LPX  NLX  Backplane systems  Most common form factors used on PCs: AT Baby AT ATX Mini-ATX

36. AT Form Factor

37. ATX Form Factor

38. NLX Form Factor

39. Types of Cases  Desktop cases  Tower cases Minitower Midsize (most popular) Full-size  Laptop cases

40. Desktop Cases

41. Minitower Cases

42. Tower and Desktop Cases

43. Case and Power Supply Vendors

44. Detecting and Correcting Power Supply Problems  Measuring the voltage of a power supply  Upgrading and installing power supplies  Troubleshooting the power system and power supply

45. Measuring the Voltage of a Power Supply  Use a multimeter Before using, tell it three things Whether to measure voltage, current, or resistance Whether the current is AC or DC What range of values it should expect How to measure voltage How to measure current How to measure continuity

46. A Multimeter

47. How to Measure the Voltage of a Power Supply  How to measure the power output for AT and ATX motherboards  Procedure for a secondary storage device

48. Measuring Voltage on an AT Motherboard

49. Measuring Voltage Output to an AT Motherboard

51. Measuring Voltage Output to an ATX Motherboard

53. Upgrading Your Power Supply  Sometimes necessary when you add new devices  Easiest way to fix a power supply you suspect is faulty is to replace it

54. Introduction to Troubleshooting  Categories of problems Problems that prevent the PC from booting Problems that occur after a successful boot  Learn as much as you can by asking questions of the user

55. Problem-Solving Flow Chart

56. Troubleshooting the Power System: Guidelines and Questions  Any burnt parts or odors?  Everything connected and turned on? Loose cable connections? Computer plugged in?  All switches turned on? Computer? Monitor? Surge protector? UPS? Separate circuit breaker? Wall outlet good?  If fan is not running, turn off computer: Connections to power supply secure? Cards securely seated?

57. Troubleshooting the Power System

58.  Troubleshooting the power supply itself  Troubleshooting the power supply fan  Power problems with the motherboard  Overheating

59. Energy Star Systems (The Green Star)  Satisfy energy-conserving standards of the U.S. EPA  Generally have a standby program that switches the device to sleep mode when it is not in use  Apply to computers, monitors, printers, copiers, and fax machines

60. Power Management Methods  Advanced Power Management (APM)  AT Attachment (ATA) for IDE drives  Display Power Management Signaling (DPMS) standards for monitors and video cards  Advanced Configuration and Power Interface (ACPI)

61. Power Management Features  Green timer on motherboard  Doze time  Standby time  Suspend time  Hard drive standby time

62. Power Management Features

63. Energy Star Monitors  Most adhere to DPMS specifications which allow for the video card and monitor to go into sleep mode simultaneously  View and change energy settings in Desktop Properties window (Windows 2000)

64. Changing Power Options in Windows 2000

65. Chapter Summary  How to measure electricity  The power supply and backup power sources  How to measure power supply output  How to change a defective power supply  Introduction to form factors  How Energy Star devices save energy