Lecture 7: Displays

April 24, 2023

Introduction to Engineering Electronics

K. A. Connor

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Lecture 7: DisplaysDigital Displays

Cathode Ray TubesFlat 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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V I R Ohm’s Law

Kirchoff’s Voltage LawKirchoff’s Current Law

V 0

I IIN OU T

Series Equivalent

R R R REQ N 1 2 . . .

Parallel Equivalent

1 1 1 1

1 2R R R REQ N

. . .

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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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• Non-Inverting Amplifier

Note that this formula is different in the lab write up

V V RROUT IN

1 1

2

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• Inverting Op-Amp

V VRROUT INf 1

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Binary Numbers6 01107 01118 10009 100110 101011 1011

0 00001 00012 00103 00114 01005 0101

1 1 0 11 110

2 222222 212 034567

+ ++++++ =183

B inarynum ber

B it0

Lower N ibb le

B yte

B it1

B it6

B it5

B it4

B it3

B it2

B it7

U pper N ibb le

128 + 0 + 32 + 16 + 0 + 4 + 2 + 1 = 183

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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

Note the error in the figure

fR R C R R C

10 6 9 3 1 2 2 1

1 4 41 2 2 1. ( )

.( )

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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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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

• 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

5V

5V

VCCVCC

14161

3456

710

921

14131211

15

P1P2P3P4

PETELDCLKCL

Q1Q2Q3Q4

CO

14012-chip

2345

9101112

1

13

1A1B1C1D

2A2B2C2D

1Y

2Y

MC14511-b

12

345

6

7

8

910111213

1415

16

BC

LTBILE

D

A

GND

edcba

gf

Vcc

SEVSEG-b

1

2

3

4

5

6 9

10

11

12

13

14

16

a

f

CAT1

e

CAT2

LDP RDP

d

CAT3

c

g

b

CAT4

12

+-

0-9 circuit

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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 QuizName________________

Sec___• Give three examples of electronic

displays• What is a pixel?• 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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Dividing Images Into Pixels

• Second image is blown up many times to show the individual pixels

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• The second image is blown up a bit less but pixels are still obvious

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• The second image is sampled more coarsely

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• Black and white or single color displays are easier to implement

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• 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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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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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 DumontB.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

http://www.mathworks.com/products/image

http://www.mathworks.com/products/image

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Charged Particle Accelerators

• Fermilab• Medical

Accelerator

Documents

Lecture 7: Displays