Lecture 8: Displays
Digital Displays
Cathode Ray Tubes
Flat Panel Displays
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Summary of What We Have Learned
•
•
•
•
•
Ohm’s Law
Resistor Combinations
What a Diode Does
Transistors as Switches
Op-Amp Configurations
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Ohm’s Law
V  IR
Kirchoff’s Voltage Law
V  0
Kirchoff’s Current Law
I IN   I OUT
Series Equivalent
REQ  R1  R2 ... RN
1
1
1
1


...
Parallel Equivalent
REQ R1 R2
RN
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Diode V-I Characteristic
• For ideal diode, current flows only one way
• Real diode is close to ideal
Ideal Diode
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Op-Amp
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Ideal Op-Amp Continued
• Bandwidth is also infinite. Thus, an ideal
op-amp works the same at all
frequencies.
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Golden Rules for Op-Amps
• The output attempts to do whatever is
necessary to make the voltage
difference between the two inputs zero.
(Negative Feedback is Required)
• The inputs draw no current.
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Op-Amp Configurations
• Buffer or Voltage Follower
 No voltage difference between the output
and the input
 Draws no current, so it puts no load on the
source
 Used to isolate sources from loads
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Op-Amp Configurations
• Non-Inverting Amplifier
VOUT

R1 
 VIN 1  
R2 

Note that this formula is different in the lab write up
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Op-Amp Configurations
• Inverting Op-Amp
VOUT  VIN
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Rf
R1
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Binary Numbers
0
1
2
3
4
5
0000
0001
0010
0011
0100
0101
6
7
8
9
10
11
0110
0111
1000
1001
1010
1011
Byte
Lower Nibble
Upper Nibble
Bit
7
Bit
6
Bit
5
Bit
4
Bit
3
Bit
2
Bit
1
Bit
0
1
0
1
1
0
1
1
1
2
128
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7
+
2
+ 0
6
+
+
2
5
+
32 +
2
4
3
+
2
+
16 +
0
+
2
1
2
4
+
+
2
0
=183
2
+
2
Binary
number
+
1
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=
183
12
Astable and Monostable Multivibrators
• What are they good for?
 Astable: clock, timing signal
 Monostable: a clean pulse of the correct
height and duration for digital system
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555 Timer
• The correct frequency is given by
1
144
.
f 

0.693( R1  2  R2)C1 ( R1  2  R2)C1
Note the error in the figure
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From What We Have Seen So Far, How
Would We Make a Display?
•
•
•
•
•
LEDs in some kind of an array
How to arrange them?
How to control them?
What is the purpose of the display?
How much should it cost?
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Binary Numbers
0
1
2
3
4
5
0000
0001
0010
0011
0100
0101
6
7
8
9
10
11
0110
0111
1000
1001
1010
1011
Byte
Lower Nibble
Upper Nibble
Bit
7
Bit
6
Bit
5
Bit
4
Bit
3
Bit
2
Bit
1
Bit
0
1
0
1
1
0
1
1
1
2
128
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7
+
2
+ 0
6
+
+
2
5
+
32 +
2
4
3
+
2
+
16 +
0
+
2
1
2
4
+
+
2
0
=183
2
+
2
Binary
number
+
1
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=
183
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7 Segment Displays
• Binary inputs are converted to a decimal
number display by turning on a set of 7
LEDs
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7 Segment Displays
• Common cathode at the right and
common anode at the left
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7 Segment Displays
1
2
9
10
7
+
1
5V
-
6
5
4
3
CL
CLK
LD
TE
PE
0-9 circuit
15
CO
VCC
VCC
1
P4
P3
P2
P1
14
13
12
11
Q1
Q2
Q3
Q4
7
1
2
6
2
14161
1
13
1Y
2Y
1A
1B
1C
1D
2A
2B
2C
2D
2
3
4
5
9
10
11
12
5V
3
4
5
8
A Vcc
B
C
a
D
b
c
LT
d
BI
e
LE
f
g
GND
16
14
13
12
11
10
9
15
14
MC14511- b
12
10
4
2
13
6
a
b
c
d
e
CAT4
CAT3
CAT2
CAT1
f
g
LDP
RDP
16
11
5
3
9
SEVSEG-b
14012- chip
• This is the 0-9 counting circuit you will
be building in the lab.
• Note that it has to count and then
convert the binary to show decimal
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Displays Applications
• 7 Segments are excellent for displaying
simple alphanumeric information –
multimeters, clocks, etc.
• More complex displays are needed to show
images – computer displays, televisions, etc.
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2 Minute Quiz
Name_______Sec______Date______
• Give three examples of electronic
displays
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Dividing Images Into Pixels
• Second image is blown up many times
to show the individual pixels
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Dividing Images Into Pixels
• The second image is blown up a bit less
but pixels are still obvious
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Dividing Images Into Pixels
• The second image is sampled more
coarsely
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Dividing Images Into Pixels
• Black and white or single color displays
are easier to implement
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Dividing Images Into Pixels
• Images can be constructed by scanning
across them, line-by-line
• The original image is encoded in this
manner (e.g. this is the way a scanner
or copier works) by, say, starting at the
upper left and going line by line to the
lower right
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Plasma Displays
•
•
•
•
Large, bright, flat panel display
View from a wide angular range
Designed for HDTV
Available from many companies
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Plasma Displays
• High voltage discharge creates high
energy photons (UV) that excite
phosphors
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Plasma Displays
• Note the patterns of the address and
display electrodes
• To excite an address, both voltages
must be applied
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Plasma Displays
• Fujitsu ALIS display
• More complex electrodes but better use
of surface area for display
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Plasma Displays
• Discharge
region geometry
and voltages
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2 Minute Quiz
Name_______Sec_____Date_______
• What is a pixel?
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Displays: CRT
• In a CRT, an electron beam excites the
phosphor rather than a UV photon
• The beam is directed to a spot on the surface
using sweep plates
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Displays: CRT
• Three separate electron guns are
required to produce a color picture
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Displays: CRT
• At the left is the layout of the mask and
phosphors
• At the right is the scanning sequence
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Displays: CRT
• A large variety of configurations are
used by manufacturers
• Look carefully at the screen of your TV
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2 Minute Quiz
Name_______Sec______Date______
• True or False
 Blue light is higher energy than red light
 Most colored light is not produced directly
 Solid state light is generally produced
directly
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Image From My TV
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Same Image Enlarged to Show Screen
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Same Image Enlarged Further
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Same Image Enlarged Further
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Unsmoothed Image Enlarged Further
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Displays: Early TV
Allen Dumont
B.S.E.E. RPI 1924
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Displays: Dumont
• Developed the first practical CRT (previous versions
lasted only 10s of hours)
• First company to market home TV receiver in 1938
(previous slide)
• Dumont network until 1956 – It could not compete with
radio networks (poorly funded)
• Broadcast Jackie Gleason, first sporting events, but
shows were bought by big 3 networks
• Dumont was one of broadcastings first millionaires
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Where Will You See This Material Again?
• 7 Segment Displays: Many courses
• CRT: ECSE-2100 Fields and Waves I
• Digital Imaging: ECSE-4540 Voice and Image
Processing
• RF Circuitry: ECSE-4060 Communications
Circuits
• Plasmas: ECSE-4320 Plasma Engineering
• Optics: ECSE-4630 Lasers and Optical
Engineering and ECSE-4640 Optical
Communications and Integrated Optics
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Imaging Tools
• Mathworks Image Processing Toolboxes
http://www.mathworks.com/products/image
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2 Minute Quiz ANSWERS
• Electronic displays-7 segment, plasma, CRT
• A pixel is a PIcture Element, smallest unit of a
display grid
• True or False
 Blue light is higher energy than red light
TRUE
 Most colored light is not produced directly
TRUE, reflected
 Solid state light is generally produced
directly
TRUE
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Charged Particle Accelerators
• Fermilab
• Medical Accelerator
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