Electricity and Power Supplies

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Chapter 4

• Electricity and Power Supplies

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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

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Measures of Electricity
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AC and DC

• Alternating current (AC)
• Cycles back and forth
• Economical
• Direct current (DC)
• Travels in only one direction, from hot to ground
• Required by most electronic devices
• Computer power supply functions as both a
  transformer and rectifier

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Computer Power Supply
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Hot, Neutral, and Ground
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Hot, Neutral, and Ground (continued)
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Hot, Neutral, and Ground (continued)
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Common Electrical Components
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Protecting Your Computer System General
Precautions

• Make notes so you can backtrack
• Remove packing materials from work area
• Keep components away from hair and clothing
• Keep screws and spacers in an orderly place
• Dont stack boards on top of each other

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Protecting Your Computer System General
Precautions (continued)

• Dont touch chips on motherboard or expansion
  cards
• Dont touch chip with magnetized screwdriver
• Dont change DIP switch settings with a graphite
  pencil

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Protecting Your Computer System General
Precautions (continued)

• Have classroom instructor check your work before
  putting cover on and powering up
• Turn off a computer before moving it
• Keep disks away from magnetic fields, heat, and
  extreme cold

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Protecting Yourself Against Electricity

• Turn off power and unplug computer
• Always use a ground bracelet
• Never touch inside of a computer while it is
  turned on
• Never remove cover or put your hands inside
  monitor or power supply

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Static Electricity (or ESD)

• Can cause catastrophic failure or upset failure
• Protection against ESD
• Ground bracelet or static strap
• Ground mats
• Static shielding bags

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Ground Bracelet
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Ground Bracelet with a Ground Mat
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Static Shielding Bags
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EMI (Electromagnetic Interference)

• Caused by magnetic field produced as side effect
  when electricity flows
• Protection against EMI
• Cover expansion slots
• Do not place system close to or on same circuit
  as high-powered electrical equipment
• Use line conditioners

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Surge Protection and Battery Backup

• Surge suppressors
• Power conditioners
• Uninterruptible power supplies (UPSs)

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Uninterruptible Power Supplies

• Benefits
• Condition line for brownouts and spikes
• Provide backup power during a blackout
• Protect against very high potentially damaging
  spikes
• Considerations
• Cost
• UPS rating
• Degree of line conditioning
• Warranty and service policies

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UPS
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The Computer Case and Form Factors

• Form factor describes size, shape, and general
  makeup of a hardware component
• Use same form factor for motherboard, case, and
  power supply
• Decision driven by motherboard

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Case, Power Supply, and Motherboard Form Factors

• AT
• ATX (most popular)
• LPX
• NLX
• Backplane systems

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AT and Baby AT Form Factors
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AT Motherboard
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Power Connectors on AT and ATX Boards
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ATX Form Factor

• Open, nonproprietary spec (Intel 1995)
• Easier to add and remove components
• Greater support for I/O devices and processor
  technology
• Lower costs
• Improved positioning of components

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ATX Form Factor (continued)

• Smaller
• Uses one power connector P1
• Soft switch feature
• Better air circulation
• Other types Mini-ATX, MicroATX, FlexATX

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ATX Motherboard
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NLX Form Factor
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Other Form Factors
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Types of Cases

• Desktop cases
• Tower cases
• Minitower
• Midsize tower
• Full-size tower
• Notebook cases

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Desktop Case
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Tower Case
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Tower and Desktop Cases
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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

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Introduction to Troubleshooting

• Isolate the problem
• Problems that prevent PC from booting
• Problems that occur after a successful boot
• Learn as much as you can by asking questions of
  user(s)

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PC Problem Solving
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Troubleshooting the Power System General
Guidelines

• Any burnt parts or odors?
• Everything connected and turned on? Loose cable
  connections? Computer plugged in?
• All switches turned on? Wall outlet good?
• If fan is not running, turn off computer
  Connections to power supply secure? Cards
  securely seated?

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Troubleshooting the Power System General
Guidelines (continued)

• Check for correct wire connections to motherboard
• Remove nonessential expansion cards one at a time
• Vacuum entire unit

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Troubleshooting an ATX Power Supply
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Troubleshooting the Power System

• Power supply itself
• Power supply fan
• Power problems with the motherboard
• Overheating

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Preventing Overheating
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Preventing Overheating (continued)
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Energy Star Systems(The Green Star)

• Satisfy energy-conserving standards of the US EPA
• Generally have a standby program that switches
  device to sleep mode when not in use
• Apply to computers, monitors, printers, copiers,
  and fax machines

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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)

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Power Management Features

• Green timer on the motherboard
• Doze time
• Standby time
• Suspend time
• Hard drive standby time

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Power Management Setup Screen
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Energy Star Monitors

• Most adhere to DPMS specifications
• Allow video card and monitor to go into sleep
  mode simultaneously

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Changing Power Options
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Summary

• Measurements of electricity
• Form in which electricity comes to you as house
  current
• The power supply, backup power sources, and how
  to change a defective power supply
• Form factors
• How Energy Star saves energy