Electricity and Power Supplies

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Electricity and Power Supplies

• CIS 145
• Microcomputer Servicing
• Chapter 3

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Atomic Structure

• Matter has weight and occupies space
• Compound two or more elements
• Element a substance that cannot be decomposed
  any further by chemical action

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ATOM
Smallest part of an element
Nucleus center part of atom
Proton
Neutron
Atomic Number number of protons
Electron
Shell electron orbit
Valence Shell outermost orbit
Valence Electron/s
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Electron

• Stable orbit
• filled shells
• Free Electrons
• random motion
• can move freely from atom to atom

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Categories of Materials

• Conductors materials that readily allow
  current.
• Have a large number of free electrons
• Characterized by one to three valence electrons
• Most metals are good conductors
• Silver
• Copper
• Gold

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Categories of Materials

• Semiconductors classed below the conductors in
  their ability to carry current because they have
  fewer free electrons than do conductors.
• Have four valence electrons
• Silicon and germanium are common semiconductive
  materials.
• Basis for modern electronic devices such as the
  diode, transistor and integrated circuit.

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Categories of Materials

• Insulators materials are poor conductors of
  electric current.
• Used to prevent current where it is not wanted.
• Have very few free electrons
• More than four valence electrons
• Are commonly compounds

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Laws of Charges

• Opposite charges attract
• Like charges repel

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Coulomb

• One coulomb is the total charge possessed by
• 6.28 x 1018 electrons

Ampere One coulomb(C) flowing past a given point
per second 1 Amp Q/s
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Voltage

• One volt is the potential difference between two
  points when one joule of energy is used to move
  one coulomb of charge from one point to the other.

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Resistance

• One ohm of resistance exists when there is one
  ampere of current in a material with one volt
  applied across the material.
• Ohm (?)

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Conductance

• The reciprocal of resistance is conductance.
• A measure of the ease with which current is
  established.
• The unit of conductance is the siemens (S)

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Ohms Law

• I V/R
• I Current (A)
• V Voltage (V)
• R Resistance (?)

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Power

• P IV
• P Watts (W)
• I Current (A)
• V Voltage (V)

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Complete/Closed Circuit
V
1.
R

• Voltage Source
• Load
• Path

2.
loop
I
3.
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Open Circuit
V
1.
R

• Voltage Source
• Load

2.
loop
I
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Short Circuit
V
1.
R

• Voltage Source
• Path

loop
I
3.
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Voltages

• Direct Current (DC)
• electrons flowing in one direction

5V
0V
5V
0V
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Voltages Continued

• Alternating Current (AC)
• electrons flowing back and forth

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Circuits

• Series Circuits
• One current path
• Added voltage drops equal total voltage
• Total resistance increases when loads are added.

• Parallel Circuits
• Current divides
• Total voltage found across each branch
• Total resistance decreases when branches are added

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Circuits
X
Peer - Peer
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Circuits
X
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Circuits
X
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Circuits
X
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Circuits
X
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Circuits
X
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Circuits
X
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Circuits
X
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Noise

• Electrostatic discharge
• Commonly known as static electricity
• Triboelectrification
• Two materials rubbed together take-on opposite
  polarities
• Two kinds of failure
• Catastrophic
• Upset failure

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Watch Out!

• ESD - Electrostatic Discharge
• The dissipation of built-up electrons to an
  object that is a good conductor of electricity.

Prevention

• Do not wear synthetic-fiber or leather-soled shoes

• Remove any static charge by touching the system
  chassis

• Wear a good commercial grounding strap

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Noise

• EMI
• Electromagnetic interference. Interference by
  electromagnetic signals that can cause reduced
  data integrity and increased error rates on
  transmission channels.

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Line Conditions

• Spikes
• A surge of voltage
• Brownouts
• A temporary drop in voltage
• Blackouts
• A lost of voltage

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Surge Protection and Battery Backup

• Surge Suppressor
• Also called surge protector
• Shunt type
• Absorbs the surge
• Series type
• Blocks the surge from flowing
• Combination of both

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Power Conditioners

• Line conditioners
• Provides continuous voltage during brownouts.

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UPS

• Uninterruptible Power Supply
• Condition the line for both brownouts and spikes
• Provide backup power during a blackout
• Protect against very high spikes that could
  damage equipment

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Case and Power Supply

• Case and power supply are usually sold as a unit.
• Considerations to consider when purchasing a
  case
• System board form factor
• Number of drive bays available
• Desktop or floor mounted

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Case and Power Supply

• Form Factor
• Refers to the physical dimensions and size of the
  system board and dictates what type of case the
  board will fit into.
• The most popular case form factors are
• Full-tower
• Mini-tower
• Desktop
• Low-profile

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Case and Power Supply

• Obsolete form factors
• Baby-AT
• Full-size AT
• LPX (semi-proprietary)

• Modern form factors
• ATX
• Micro-ATX
• Flex-ATX
• NLX
• WTX

ATX system boards are recommended for most people
building their own systems today.
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Case and Power Supply

• ATX is an open architecture that improves on the
  older Baby-AT design in many ways that affect
  other components of the computer.
• ATX-style power supply features a redesigned,
  single-keyed connector that cannot be plugged in
  backward or off-center.

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Case and Power Supply

• ATX improves on the Baby-AT and LPX motherboard
  designs in several major areas.
• Built-in double high external I/O connector panel
• Single keyed internal power supply connector
• Relocated CPU and memory
• Relocated internal I/O connectors
• Improved cooling
• Lower cost to manufacture

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Case and Power Supply

• Cases form factors that take ATX boards
• Full-tower
• Mini-tower
• Desktop
• ATX full-tower case and power supply is the
  recommended choice

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Case and Power Supply

• Power Supply
• Converts AC into DC
• Transformer
• Rectifier
• Provide surge protection
• Provide output voltages for various devices
• Rated by capable wattage output
• Wattage is the product of voltage and amps

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Case and Power Supply

• A faulty power supply can cause
• Memory errors
• Data errors
• System hangs
• Reboots
• It can damage a motherboard or other components

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Case and Power Supply
Power Consumption Calculations
Available 5V Power (Amps) 20.0A
Available 12V Power (Amps) 8.0A
Less System Board 5.0A 4 slots filled at 2.0
each 8.0A 3.5 FDD Logic 0.5A 3.5
HDD 0.5A CD-ROM/DVD 1.0A
Less 4 slots filled at 0.175 each 0.7A 3.5 FDD
Drive Motor 0.5A 3.5 HDD Drive
Motor 0.5A Cooling fan motor 0.1A CD-ROM/DVD
drive motor 1.0A
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Energy Star

• U.S. Environmental Protection Agency
• Established Energy Star standards for electronic
  devices
• Sleep Mode
• Use less than 30 watts of power
• CMOS settings
• Affects the available options on the PC.

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Case and Power Supply
TURN IT OFF
In general, one should shut-down the system on an
average of once a day.