Hardware Fundamentals
Week 7 – Lesson 1
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Hardware Fundamentals
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Learning Outcomes
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Define Visual Display Unit (VDU) characteristics: Pixel, Resolution,
Screen size and Refresh Rate
Describe briefly the purpose of video standards.
Discuss different video standards and high-definition television standards
Define Cathode Ray Tube (CRT) characteristics: Dot pitch, Black and
White versus Colour monitors, Two types of pixel shapes, Interlaced,
Non-interlaced and Radiation
Describe CRT operation, LCD operation, and Plasma operation
Define Liquid Crystal Display (LCD) characteristics: Matrix, Passive
matrix and Active matrix
Define Plasma characteristics
Compare CRT, LCD and Plasma displays
Is CRT still the best for high-definition TV?
Surface-conduction Electron-emitter Display (SED) for the future
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Visual Display Unit (VDU)
characteristics
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Pixel

Picture element
 The smallest thing that can
be turned on or off to
produce an image
 A dot
 Anything you see on a
computer screen is a
combination of these dots
or pixels
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Resolution
 Total
number of pixels displayed
 Resolution = # pixels across * # lines
displayed
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If there are 1024 pixels across
and 768 lines displayed, what
is the resolution?
Resolution
1024 * 768 = 786,432
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Screen size
 Measured
diagonally
across the front face
 Measured in inches
 Viewable areas may be
less
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Typical sizes: (12.1”), 14”, (14.1”),
15”, (15.4”), 17”, 19”, 20”, 21”, 22”,
24”, 27”
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Refresh rate
 How
often the screen is refreshed or
redrawn
 Screen needs to be refreshed regularly
as the phosphors stop glowing and the
image to be displayed changes
 Measured in Hertz (i.e.. Hz) per second
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Video standards
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Video standards
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Defines the resolution and colors
for displays
 The standard used, will be determined by the
monitor and the video adapter card
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For high-resolution displays:
 Quad – is a mode with four times as many pixels
(twice the width and twice the height)
– is a mode with 16 times as many pixels
(four times the width and four times the height)
 Hex
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Video standards
Name
Resolution
Total pixels
Colour Graphics Adapter (CGA) 320 x 200
64,000
Enhanced Graphics Adapter
(EGA)
640 x 350
224,000
Video Graphics Array (VGA)
640 x 480
307,200
Super VGA (SVGA)
800 x 600
480,000
eXtended Graphics Array (XGA) 1024 x 768
786,432
Super XGA (SXGA)
1280 x 1024
1,310,720
Ultra XGA (UXGA)
1600 x 1200
1,920,000
Quad XGA (QXGA)
2048 x 1536
3,145,728
Quad SXGA (QSXGA)
2560 x 2048
5,242,880
Quad Ultra XGA (QUXGA)
3200 x 2400
7,680,000
Hex Super XGA (HSXGA)
5120 X 4096
20,971,520
Hex Ultra XGA (HUXGA)
6400 X 4800
30,720,000
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High Definition Television standards
Name
Resolution
Total pixels
Wide Quarter VGA
(WQVGA)
400 x 240
96,000
Wide VGA (WVGA)
852 x 480
408,960
Wide XGA (WXGA)
1366 x 768
1,049,088
Wide Super XGA (WSXGA)
1600 x 1024
1,638,400
Wide Ultra XGA (WUXGA)
1920 x 1200
2,304,000
Wide Quad XGA (WQXGA)
2560 x 1600
4,096,000
Wide Quad Super XGA
(WQSXGA)
3200 X 2048
6,553,600
Wide Quad Ultra XGA
(WQUXGA)
3840 X 2400
9,216,000
Wide Hex Super XGA
(WHSXGA)
6400 X 4096
26,214,400
Wide Hex Ultra XGA
(WHUXGA)
7680 X 4800
36,864,000
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Three types of monitors
 Cathode
Ray Tube (CRT)
 Liquid Crystal Display (LCD)
 Plasma
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Three types of monitors
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CRT characteristics and operation
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Dot pitch
 Spacing
between each pixel
 Typically 0.24mm
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Black and White versus Color monitors
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Black and White monitor
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Use white pixels
Made up of one phosphor
Colour monitor
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Uses three primary colours: Red; Green; and Blue
(RGB)
Made up of three phosphors, so close that the
human eye sees the image as one single pixel
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Two types of pixel shapes
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Triad
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Three electron guns arranged with
overlapping circles in a triangle
Circular holes in shadow mask
Used in smaller screens (e.g. monitors)
Trinitron
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Three electron guns arranged in one line
Three parallel slots
Oval slots in shadow mask
Used in large screens (e.g. televisions)
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Interlaced
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Image on screen is created
in two halves
 First the odd numbered
lines then the even
numbered lines
 Cheaper
 Produce a flickering image
and jerky video motion
 Mostly found on older PC
monitors
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Non-interlaced
 Entire
screen is created in one go
 Less flicker
 Smoother video motion
 More commonly found
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CRT operation (1 of 2)
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Electron gun generates an electron beam
 The yoke is an electromagnet. Varying the
magnetism in the yoke causes the electron beam to
focus in particular areas of the screen
 The shadow mask is a metal screen with holes in it.
The metal blocks the electron beam but the holes will
let the electron beam through when it will strike a
pixel, and only one pixel. Makes sure the image is
sharp
 The phosphor screen is made up of the phosphors
that glow when hit by the electron beam. An image is
formed by turning on some phosphors but not others.
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CRT operation (2 of 2)
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The electron beam sweeps over the phosphor
screen, making some phosphors glow, so fast that
the user sees a stable image on the screen.
Other components such as the panel glass, funnel
glass and the inner magnetic shield provide the
structure of the CRT
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Radiation
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Whenever an electric current passes through
a conductor (such as a wire or a copper track
on a circuit board) it gives off an electro
magnetic field
 The electron gun, electromagnet and coil
inside a CRT monitor produce magnetic fields
that radiate from the monitor
 Most of this radiation is exposed from the rear
of the monitor
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LCD characteristics
and operation
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Matrix
A
two dimensional array; that is, an
array of rows and columns
 The background area of colour display
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Two methods are used to apply
charges to liquid crystal cells
 Passive
Matrix
 Active Matrix
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Passive Matrix
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Thin Film Transistor (TFT) for each row and
column
 Cheaper
 Use relatively few electrodes arranged along
the edges of the liquid crystal layer and rely
on timing to be sure the correct cells are
charged
 The charges in the cells fade quickly, causing
a faded look
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Active Matrix
Individual TFT’s for each cell/sub pixel (i.e.
RGB)
 Brighter
 Wider viewing angle
 Expensive
 70% failure rate at manufacturing stage
 Provide a more precise and stronger charge,
creating more vivid colours
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LCD operation (1 of 2)
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Light emanating from a fluorescent panel behind a
computers display panel spreads out in waves that
vibrate in all directions
A polarising filter in front of the light panel lets
through only the light waves that are vibrating more
or less horizontally
In a layer of liquid crystal cells – there is one for each
colour (RGB)
The light emerging from each liquid crystal cell
passes through one of the three colour filters – RGB
– that are arranged close to each other
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LCD operation (2 of 2)
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The coloured beams of light pass through a second
polarising filter that is aligned to let pass only those
light waves that are vibrating more or less vertically
The light that passed through a liquid crystal to which
a full electrical charge was applied is now oriented
perfectly to pass through the second filter.
Any light that was not twisted at all when passed
through the liquid crystals is now blocked completely
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Plasma characteristics
and operation
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Plasma characteristics
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Thin display, less than 2 inches thick
 Flat display
 Can be hang on the wall like a painting
 Plasma display is brighter than LCD
 Wider viewing angle than LCD (160 degrees)
 Larger sizes than LCD
 More expensive than LCD
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Plasma operation (1 of 3)
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Two sets of electrodes
 Address Electrodes are positioned vertically in the
rear of the display
 Display Electrodes are positioned horizontally in
the front of the pixels
 These electrodes run through layers of glass and
magnesium oxide, which protect and insulate the
electrodes from each other
 Pixels are called cells, these are depressed in ridges
called ribs
 The ribs separate the cells
 Trapped inside each cell is a mixture of xenon and
neon gases
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Plasma operation (2 of 3)
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Illuminate tiny coloured fluorescent lights to form an
image
Each pixel is made up of three fluorescent lights: a
red light; a green light; and a blue light
Display varies the intensities of the different lights to
produce a full range of colours
The central element in a fluorescent light is a plasma,
a gas make up of free-flowing ions (electrically
charge atoms) and electrons (negatively charged
particles)
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Plasma operation (3 of 3)
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When an electrical current runs through a plasma,
negatively charged particles are rushing toward the
positively charged areas of the plasma, and the
positively charged particles are rushing toward the
negatively charged areas
 In this mad rush, particles are constantly bumping
into each other
 These collisions excite the gas atoms in the plasma,
causing the plasma screens to release light photons
of energy
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CRT versus LCD versus
Plasma
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CRT
LCD
Cheaper
Uses less power
More robust
Flat more compact screen
Brighter colours
Lighter
More contrast
No radiation
Wider viewing angle Not affected by magnetic fields
Higher refresh rate
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Calculated longer life
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LCD
Plasma
Cheaper
More expensive
Positioned on desk
Hang on the wall
Best image front-on
Wider viewing angle
Smaller sizes
Larger sizes
Brighter display
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Is CRT still the best for highdefinition TV?
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CRT monitor
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Despite the popularity of LCD and Plasma
screens, the best display of high-definition TV
is still the CRT monitor
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SED for the future
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Surface-conduction Electronemitter Display (SED)
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Developers are Canon and Toshiba
Combines the best of CRT’s, LCD’s and plasma
displays
Will have the visual quality of a CRT monitor and the
slimness of LCD and plasma flat panels
Requires less materials than LCD and less expensive
circuitry than plasma
Screen is made up of phosphors (CRT) painted on
the inside of a plate of glass, each phosphor dot has
its own emitter which shoots electrons at only its
matching phosphor (no electron beam)
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References
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Required textbook
http://www.howstuffworks.com
http://www.webopedia.com
http://www.fourmilab.ch/documents/howmanydots/
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