Chpt11a Electricity,Power Supplies & Electrostatic Discharge

8/9/2019 Chpt11a Electricity,Power Supplies & Electrostatic Discharge

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A+ Certification for PC Technician

Chapter 11Chapter 11

Electricity,Power Supplies & Electrostatic Discharge


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Slide 2Ver 1.0 10 April 2001 Electricity,Power Supplies & Electrostatic Discharge

ElectricityElectricity

What is Electricity?It is the Flow of Electrons from in amedia. Electricity flow from Negativeto Positive potential.

How many types of Electricity?

2 types: Static and Dynamic.

What is Static Electricity?

Electrical charge stored within ainsulating object. The Electrons do notmove through a circuit.

What is Dynamic Electricity?

Charges created by heat, light,chemical reactions or magneticinduction. Electrical circuit is created inthe process.

What are the 2 forms of electricity?1. Alternating current

2. Direct current

What is Alternating current?

Current flow that changes direction at

a certain frequency eg 60Hz

What is Direct Current?

Current that flows in 1 direction.Rectifier is used to converts AC to DC


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Measuring ElectricityMeasuring Electricity

What is Voltage?Measure the difference of electriccharges that causes the electrons toflow from 1 point to another. Unit isVolts or V. Use a Voltmeter to measure.

How is Voltage measured?

Measure in Parallel to the device to bemeasured.

What is Ampere?

Measure the rate of flow of electricalcharge (current). Unit used is Amp or A.

How is current measured?

Measured in series with the device tobe measured.

What is Ohm?Measure the resistance to the flow ofelectricity (;). Device used to limit theflow of electricity is the Resistor.

How is Resistance measured?

Measure in parallel to the device to bemeasured in a broken circuit?

What is Watt?

Measure the electrical power,calculated by multiplying Volts by Amps


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Measuring Voltage, Current & ResistanceMeasuring Voltage, Current & Resistance


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MultimeterMultimeter

What is a multimeter?A measuring instrument use to measurevoltage, current and resistance. It canbe select to function as voltmeter,ammeter and ohmmeter.

How do you set it to use measure areading?To measure, set to the range to coverthe expected reading eg to measure20V range, set meter to 25V and allvoltages fall between 20 and +20 aremeasurable

Multimeter sets to 20V


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Short CircuitShort Circuit

How is current being controlled in anormal circuit?

Each electrical device has someresistance to the current flow. Thiskeeps the current from reaching verylarge values.

How does a Short Circuit Happen?Occurs when the current finds a way tobypass the appliance on a path that haslittle or no resistances to the currentcan flow straight to ground.

How dangerous it is?In a very large current occur, itproduces a lot of heat is a fire hazard.


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Electronic ComponentsElectronic Components

Components Description

Conductors Conducts electricity eg gold, copper

Insulators Resists the flow of electricity eg glass, ceramic

Semiconductors Ability to conduct electricity falls between conductor

and semiconductorTransistor Used as a switch for electrical signal

Amplify the flow of electricity

Capacitor Holds electrical signal for a period of time

Smoothen out the flow of electricity

Measure in FaradsDiode Semiconductor device allowing electricity to flow in one

direction


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Common Electronic Component SymbolsCommon Electronic Component Symbols

Resistor Capacitor Ground

Diode

Transistor


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Power SupplyPower Supply

What type of Power supply is used bythe computer?

Direct current or DC. The main powersupply to the PC is AC and needs to beconverted to DC.

What are the 2 components of thePower Supply Unit?1. Fan to provide an airflow inside the

computer to cool the componentsand also to keep the dust fromsettling on and coat thecomponents.

2. AC/DC converter to change the120V AC current to DC current of5V/12V/3.3V. Converter include theregulator, rectifier, resistors,capacitor and transformer.

Does the Power Supply requires a loadto function?

Yes. Voltage does not flow unlesssomething ask for it.

How does it maintain a steady flow ofcurrent?

It has a load resistor and fuse tomaintain power flow at a pre-determined limit. Exceeding that limitwill cause the fuse to burns out.


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AT/ATX Power Supply Unit (PSU)AT/ATX Power Supply Unit (PSU)

What are the 2 major PSU formfactors?

AT, ATX

What are the major characteristics ofAT PSU?1. Uses P8 and P9 connectors. Need to

keep the black cables from bothconnectors together when insertingto the motherboard

2. Supplies 5V and 12V

3. Power supply lead:

Black for ground

Red for +5V White for 5V

Yellow for +12V

Blue for 12V

Orange for Power_Good

What are the major characteristics ofATX PSU?1. Use P1 connector (20 pins) and

supplies 3.3V, 5V and 12V

2. Support software switch which allowsautomatic shutdown when press

3. Power supply lead:

Black for ground Red for +5V, White for 5V

Yellow for +12V, Blue for 12V

Brown for +3.3V

Grey for Power_Good

ATX P1 connectorAT P8 and P9 connector

4 Black cables


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Energy Star ComplianceEnergy Star Compliance

What are the criteria necessary for anequipment to be labeled Energy Star?

Satisfy certain energy-conservingstandards of the US EnvironmentProtection Agency (EPA)

What are the common features?

Device should not consume more than30 Watts. Equipment goes into sleepwhen not in used and can saved up to50% of energy.

Energy Start Logo


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Power Management MethodsPower Management Methods

What are the 2 methods used in PC toManage power

Advanced Power Management (APM)Advanced Configuration and PowerInterface (ACPI)

What is APM?

Introduced with Windows 95. Itshutdown power consuming devicesafter a period of inactivity.

What are the items supporting APM?

Hard disk, monitor (laptops LCD

backlight), throttling back the CPUduring idle periods, query the batteryto obtain its current charge information

What is ACPI?ACPI build upon APM. Introduced withWindows 98/ME. It can turn off CD-ROM, DVD-ROM, modems.. Allowssystem to wake up and perform pre-determined tasks.

Activating ACPI?Install Windows 98 with ACPI onsystem with ACPI. Steps:

1. Start, run

2. Setup /p j


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Power Management FeaturesPower Management Features

What are the necessary components tosupport Power Management?

BIOS, chipset, devices and operatingsystem

What are the Power Schemes inWindows 98?

1. Basic conservation

2. Standby

3. Hibernation

What is Basic Conservation?

Turn off monitor and drive after agiven period is inactivity

What is Standby?Put computer in a standby mode whenidle. Monitor turns off, hard disk andsome other devices are powered down

What is Hibernation?

Go into standby mode . If PC continuesto be idle, everything is saved into thehard disk and PC is turned off.

What happens when the the PCs restartafter hibernation?

The last state is restored to the

memory.

What does hibernation needs in orderto work?

Sufficient hard disk space to work.


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Power SchemePower Scheme

What are 3 pre-defined Power Scheme:1. Always on

2. Home/Office Desk

3. Portable/Laptop

How to Customized the Power Scheme?

Click Start, Setting, Control Paneland then double-click PowerManagement

Click the Power Scheme dropdownlist and select on of the choices

You can customize

How to Invoke Standby Mode? Use the Shutdown Windows dialog

box

Note: Information is RAM is NOTsaved to the HDD and will be lost ifthere is a power interruption

How to Configure PC to go Standbymode when you press Power button

Start, Setting, Control Panel anddouble-click Power Management

Click the Advanced tab, locateWhen I press the power button on

my computer and click Standby Note: For Notebook, find When I

close the lid of my portablecomputer


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Power HazardPower Hazard Surge/SpikeSurge/Spike

What is a Spike?Instantaneous increases in voltage, dueto lightning storms or immediatelyafter the utility restores power.

What damages can it cause?Refer to Surge.

What is the equipment use to protectagainst Surge/SpikeSurge/Spike Suppressor

How does it works?Reduces the massive voltage to a samesafe level of power that your equipmentwas receiving before the lightningstrike. Should let through only thepower needed by your equipment. Maxvoltages allow through is normally 300V.

What are the common power problemsthat may damage the PC?

1. Surge

2. Sag

3. Spike

4. Blackout

What is a Surge?

Small over-voltage lasting few seconds

How does Surge damage the PC?

Damage critical component eg burns the

motherboard, rendering the hardwareuseless and destroy your data. If asurge travels into your computer viadata or telephone lines, the firstcasualty is usually the modem.


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Power HazardPower Hazard Sag/BlackoutSag/Blackout

What is Blackout?Lost of power supply. Caused by faultson the utility power system. Causesunexpected and damaging shutdown ofall electrical equipment eg fuse blown

Which equipment is used to guardagainst Blackout?Interrupted Power Supply or UPS. Itmaintains a steady flow of power untilthe system can be safely, automaticallyshut down.

What are the purchasingconsiderations?Power rating (VA or Watt), operatingtime, cost

Should UPS be used for Printer?No

What is a Sag?Drop in voltage level lasting from a fewmilliseconds. Sags of longer than about10 to 20 milliseconds may causecomputer equipment to malfunction.

What causes Sag?

Very high power demands of manyelectrical devices (including motors,compressors, elevators, shop tools, etc.)when they powered on.

What does Sag affects a PC?

Starve" a computer of the power itneeds to function, and cause frozenkeyboards and unexpected systemcrashes which both result in lost orcorrupted data.


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Power HazardPower Hazard Sag/BlackoutSag/Blackout

Which equipment is used to guardagainst Sag?

Power line conditioner and a UPS.

What is a Line conditioner?

Apower conditioner is a device that isused to protect electrical devices frompower surge and sag. It automaticallysteps up low voltage and steps downhigh voltage to levels that are suitablefor your equipment

What is a Brownout?

Extended Sag, last more than a second.


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Electrostatic Discharge (ESD)Electrostatic Discharge (ESD)

What causes ESD?

Brief flow of static electricity causedby 2 objects having difference voltages

Is it destructive?

Yes. It can damage components egmicroprocessor, RAM

What causes ESD:

1. Moving people, where clothes rubtogether

2. Low humidity (hot and dry), below50%

3. Improper grounding

4. Unshielded cable

5. Poor connection

6. Moving machines

What can you used to clean the interiorof a PC without producing ESD?

Use Compressed Air to blow dust out ofcomponents

Can eraser (rubber) be used to cleanthe leg of expansion card?

No. Using Easer to clean the connectingpins produce ESD


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Discharging ESDDischarging ESD

What are the ways to discharge ESD?

Wear Grounding strap around thewrist when working withcomponents

Stand on anti-static mats

Ground is connected to the safetyground of the AC power outlet

Discharge by touching the chassis

Humidify the room as dry air actsas insulator storing static charges

In what situation you should NOT weara Static Wrist strap?

When working INSIDE a Monitor orPower supply unit.

What are the devices that requireprofessional service personnel?

CRTs (cathode ray tube)

Power supplies

Laser (high power sources)


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Electromagnetic InterferenceElectromagnetic Interference

What causes EMI?Caused by flow of electricity

Are they Destructive?No. It does not damage equipment. But

can disrupt the operation ofelectronic components, devices, and

systems in its vicinity.

What does it affects?1. Distorted images on the video

display2. Interfere with commercial

communication equipment eg TV,

radio3. Corrupt data4. Signal loss in cable. Called Cross

Talk - where a cable interfere withadjacent cable

What are the steps can be taken tominimize EMI?

Ensuring all electronic equipment isoperated with a good electrical groundsystem. Cords and cables connectingthe peripherals in an electronic orcomputer system should be shielded


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Fire ExtinguisherFire Extinguisher

How are Fire Extinguisher categories?

By the types of material causing thefire

What are the 3 common classes of fire?

A, B and C

What is Class A fire extinguisher?

Ordinary combustible. Fire from wood,paper, clothing, etc.

What is Class B fire extinguisher?

Combustible liquid. Fires from gasoline,oil, or grease fires in the kitchen.

What is Class C fire extinguisher?

Electrical fire. Any fires that involveelectricity fall into this category

Which Class of fire extinguisher shouldbe used if the fire involves a PC?

Class C

Chpt11a Electricity,Power Supplies & Electrostatic Discharge

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