Chapter 7 Electronic Terms

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Chapter 7Electronic TermsPower Supplies
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Working electronic Device CONCEPT

• Electronic devices function as a result of the
  movement of electrons in a conductor.
• Electrons are forced to move in the conductor as
  a result of the pressure applied by voltage.
• As a result of the movement of electrons work,
  expressed in Watt, is accomplished.

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Electronic Terms with units of measure

• TERM UNIT
• Voltage (EMF) Volt
• Current Flow Ampere
• Power Watts
• Resistance Ohm
• Continuity and Conductivity Mho (Seimens)

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Other Electronic Terms

• Conductor - Easily conducts current
• Insulator - Does not conduct current well
• Semiconductor Does neither well

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Voltage

• The electrical potential difference is what
  causes current to flow.
• The basic unit of voltage is the volts .

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Current flow Amperes (Amps)

• Ampere unit of measurement for electrical
  current.
• One volt across aresistance of one ohm will
  produce a flow of one amp.

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Power Watts

• Total amount of power needed to operate an
  electrical device.
• Measured in watts.
• Calculated by multiplying volts by amps in a
  system.

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RESISTANCE to current flow - Ohms

• The standard unit of measurement for electrical
  resistance is the Ohm.
• Named after Mr. George Ohm, mathematician and
  physicist b. 1789 d. 1854 - Bavaria,
• He defined the relationship between power,
  voltage, current and resistance.
• Resistors are rated in ohms.

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Conductivity

• Conductivity is the opposite of resistance. It
  is a measure of a materials ability to conduct
  current.
• Continuity If a wire or circuit has continuity
  that means that there is a complete circuit from
  one end to the other end of the circuit.
  

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Two Types of Electricity

• AC Alternating Current
• DC Direct Current
• Both types of electricity are used by the
  computer.
• AC to the power supply
• DC from the power supply to other computer
  devices.

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AC

• AC Alternating Current - The type of electricity
  that is delivered from the wall socket. Its
  polarity and value are constantly changing.
• In the United States household electricity
  normally has a voltage value between 110 and 120
  AC volts.
• This electricity is supplied from a standard wall
  outlet.

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DC

• DC Direct Current The type of electricity that
  is provided from a battery or a computer power
  supply. It has a constant polarity and value.
• DC (direct current) Computer power supplies
  transform the 120 VAC to lower values of AC
  voltages and convert to the voltage to DC.
  

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The Hot, Neutral, and Ground wires for AC
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AC Wiring Color Codes

• Black Hot
• White Neutral
• Green Safety Ground

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Testing AC Voltage

• Test all of the wall outlets that the PC uses
• Include any peripheral devices plugged into a
  wall outlet
• Include the PC and the monitor plugs
• Circuit testers are available
• The hot should output approximately 115 V, the
  neutral should output approximately 0 V, and
  the ground should connect to ground (also
  approximately 0 V)

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Multimeter Basics

• A multimeter (or Volt-Ohm meter VOM) is used to
  measure
• Voltage
• Resistance
• Continuity (level of resistance)
• When using a multimeter, you must properly set it
  to either AC or DC, depending on the voltage
  youre trying to measure

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Multi-Meters
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A Digital Multimeter
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Using a Multimeter

• A multi-meter can be used as either a voltmeter,
  ammeter or an ohm meter. It will measure
  continuity, depending on a switch setting.
• Measure voltage and current with electricity ON
• Measure resistance and continuity with
  electricity OFF
• Autorange meter - Senses quantity of input and
  sets the range accordingly

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How to Measure the Voltage of a Power Supply

• Be sure that the volt meter or multi-meter is set
  on the proper range and function.
• Voltage measurements are taken with respect to
  chassis ground.
• Place the negative (black) lead on the power
  supply common or the chassis.
• Place the positive (red) lead on the voltage to
  be measured.

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Uninterruptible Power Supply

• An uninterruptible power supply (UPS) provides
  protection against a power dip or power outage
• Contains a battery that provides AC power to the
  computer
• Online is true protection and power conditioning
  battery is constantly being charged and system
  is running off the battery at all times
• Stand-by uses AC until the voltage drops enough
  to switch over to the battery no power
  conditioning and a fail-over time required
• All uninterrupted power supplies are measured in
  watts

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Power Terms

• Under voltage the voltage is known as a brownout.
• Black out is a total loss of power
• Over voltage the voltage is 130v
  

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Power Protection

• Surge Protectors
• Line conditioners
• Uninterruptible Power Supplies
• Standby Power Supplies
• Phone Line Isolators

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Surge Protectors

• Typically a 4 or 6 outlet strip with built-in
  protection against over voltage.
• Does not protect against under voltage.
• Typically use Metal Oxide Varistor (MOV) as
  protection.
• Look for the underwriters laboratories UL1449
  standard number.

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Surge Suppressors
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Line Conditioners

• Also known as Power Conditioner
• More expensive than Surge Protectors
• Protects from
• Over voltage
• Under voltage
• Noise on the power line
• Condition the power providing continuous voltage
  during brownouts

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Line Conditioners
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Uninterruptible Power Supply

• Provides a backup power supply in the event the
  AC current fails completely.
• Current capabilities differ depending on battery
  size.
• Dont plug a laser printer into a UPS.
• May produce square wave rather than sine wave
  voltage.
  

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Uninterruptible Power Supply
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When Buying a UPS

• UPS rating should exceed your total VA or wattage
  output by at least 25
• Be aware of the degree of line conditioning the
  UPS provides
• Consider the warranty and service policies as
  well as manufacturers guarantee
  

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Standby UPS and Inline UPS

• Inline UPS (Text calls these Online)
• Continually provides power through a
  battery-powered circuit
• Requires no switching
• Ensures continuous power to the user
• May provide power conditioning
• Standby UPS (Also called a SPS)
• Quickly switches from an AC power source to a
  battery-powered source during a brownout or power
  outage.
  

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Line-interactive and Intelligent UPSs

• Line-interactive UPS
• Variation of a standby UPS
• Shortens switching time by always keeping the
  inverter that converts AC to DC working, so that
  there is not charge-up time for the inverter
• Intelligent UPS
• Connected to a computer by way of a serial cable
  so that software on the computer can monitor and
  control the UPS
  

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Phone Line Isolation

• May also be called a modem isolator
• Provides protection from high voltage spikes that
  occur on the phone line.
• May be built into a surge protector.

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Purpose of a power supply

• The computer power supply uses the 115V AC from
  the wall socket and
• transform the voltage down to a level usable by
  the computer.
• Converts the lower level AC voltages to DC
• Filters the DC voltage
• Provides voltage regulation

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The Power Supply

• The power supply acts as a step-down transformer
  converting high voltage AC into 5, 12, and 3.3 V
  DC
• PCs use a 12V current to power motors on devices
  such as the hard drives, and CD-ROM drives
• PCs use a 5-volt/3.3-volt current to support
  onboard electronics

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The Power Supply

• AT and ATX are the two types of power supplies
  that can be installed in any PC
• The ATX form factor motherboard, with its unique
  ATX power supply, dominates todays systems
• All power supplies share a number of common
  features such as the power connection,
  motherboard power, power switch, peripheral
  connections, and the fan

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Power Supply
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Modular Power Supply Tiger Direct
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Modular Cables

• Connectors
• 1 - 20-Pin Main Power
• 1 - 6-Pin AUX (Xeon) Power
• 1 - 4-Pin 12V (P4)
• 6 - 4-Pin Peripheral
• 1 - Floppy

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Power Connections

• The power supply connects to the power cord
  through a standard IEC-320 connector
• Each power supply must have standard AC power
  from the company

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DC Power

• DC power comes out of the computers power
  supply, and provides electricity to all the
  components in the PC
• Flows in one direction, from negative to positive
• All PC power supplies provide both positive and
  negative voltages

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AT Power Connectors

• P8 and P9 are a pair of connectors that link the
  AT power supply to the AT motherboard
• As they are faced, they cannot be installed
  backwards

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ATX Power Connector

• Uses a single P1 power connector
• The P1 has a notched connector to ensure proper
  installation

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ATX Power Connector
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P4 Connector

• Many motherboards require a second, four-wire
  connector to push more 12-volt power into the
  board

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P1 and P4 Voltages
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Power to Peripherals

• Motherboards require power from the power supply
  as weve already seen
• Peripherals like hard drives, floppy drives,
  CD-ROM drives, and fans also require power from
  the power supply
• Different types of connectors are used
• Molex (company name)
• Mini connectors also called Berg connectors
• Splitters

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Molex Connectors

• Primarily used for devices that require 12V and
  5V of power
• A Molex connector uses chamfers (notches) for
  easy installation
• Installing a Molex backwards can destroy the
  device into which the Molex is connected

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Mini Connectors

• Primarily for 3.5-inch floppy drives
• Care should be taken when installing mini
  connectors

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Splitters and Adapters

• Occasionally, there are not enough connectors to
  power all the devices inside a PC
• Splitters are used to create more connections
• Adapters are used to adapt a Molex to a mini plug
  if necessary