chapter 4 electricity and power supplies. you will learn… how electricity is measured how to...
TRANSCRIPT
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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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Electricity: Basic Introduction
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Measures of Electricity
continued…
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Measures of Electricity
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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
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Voltage
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Amps
Ampere = unit of measurement for electrical current
Amps remain constant throughout electrical system
Current: volumn of electrons flowing through an electrical system Ammeter
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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
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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
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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
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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)
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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 rectifierDevice that changes ratio of current to voltage (reduces voltage to a usable level)
Device that converts AC to DC
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Computer Power Supply
Hertz (Hz):
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Power Supply Function
Rect
ifier
Chapter questions 2-6
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Hot, Neutral, and Ground
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Hot, Neutral, and Ground
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
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Hot, Neutral, and Ground
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Hot, Neutral, and Ground
Receptacle tester
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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)
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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
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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
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Protecting Against Electricity
When working inside a computer• Turn off the power
• Unplug the computer
• Use a ground bracelet
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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
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Using a Ground Bracelet
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Using a Ground Bracelet and a Ground Mat
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Using Static Shielding Bags
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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
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Surge Protection andBattery 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
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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 surgesBrownouts: temporary voltage reductions
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Uninterruptible Power Supply
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What to Consider WhenBuying 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
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UPS Manufacturers
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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
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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
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AT Form Factor
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ATX Form Factor
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NLX Form Factor
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Types of Cases
Desktop cases Tower cases
• Minitower
• Midsize (most popular)
• Full-size
Laptop cases
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Desktop Cases
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Minitower Cases
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Tower and Desktop Cases
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Case and Power Supply Vendors
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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
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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
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A Multimeter
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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
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Measuring Voltage on an AT Motherboard
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Measuring Voltage Output to an AT Motherboard
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Measuring Voltage Output to an AT Motherboard
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Measuring Voltage Output to an ATX Motherboard
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Measuring Voltage Output to an ATX Motherboard
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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
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
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Problem-Solving Flow Chart
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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?
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Troubleshooting the Power System
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Troubleshooting the Power System
Troubleshooting the power supply itself Troubleshooting the power supply fan Power problems with the motherboard Overheating
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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
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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 motherboard Doze time Standby time Suspend time Hard drive standby time
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Power Management Features
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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)
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Changing Power Options in Windows 2000
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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