W A T K I N S - J O H N S O N C O M P A N Y Semiconductor Equipment Group

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Engr/Math/Physics 25
Chp4 MATLABProgramming-4
Bruce Mayer, PE Licensed Electrical Mechanical
EngineerBMayer_at_ChabotCollege.edu
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Learning Goals

• Write MATLAB Programs That can MAKE Logical
  Decisions that Affect Program Output
• Write Programs that Employ LOOPing Processes
• For ? No. Loops know a priori
• while ? Loop Terminates based on Logic Criteria

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Loop Structures

• The conditional statements (if, else, elseif) we
  learned last time allowed us to determine at
  run-time whether or not to execute a block of
  code.

• What these Decision Statements Do NOT do is to
  allow us to execute a block more than once
• The TWO Things that Computers Do Better than
  People
• STORE Massive Amounts of Data
• REPEAT operations

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Repetition ? LOOPs

• A LOOP is a Program Structure that REPEATS
  Until some CONDITION is MET
• The NUMBER of Loops may Be
• Known a priori (ahead of time)
• No. of Loops Determined by simple COUNTING

• Determined Dynamically
• No. of Loops Determined by a DECISION statement
• The Loop consists of
• A Condition Test
• A Repeated Statement-Block

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Test vs Statement Locations

• The key feature ? we test to see whether or not
  to continue before executing the body of the
  loop.
• i.e., The Loop May Not Execute at All
• Good if Potential Zero Executions is Desired
• a.k.a. While DO

• PreTest Loop

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Test vs Statement Locations

• PostTest Loop

• The Key feature ? Do Not Test Until the Block
  Executes at Least Once
• Use if Design Calls for at Least-One Repetition
• a.k.a. DO While

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Test vs Statement Locations

• MidTest Loop

• The generalization of both the pre-test and the
  post-test loops
• Empty Block-1 ? PreTest Loop
• Empty Block-2 ? PostTest Loop

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for Loop Statement
Start

• A PreTested, COUNTED Loop

Set k m

• No. Repetitions Known
• MATLAB Syntax
• for Counter Start Increment Endstatements
• end

k n?
Increment kby s
True
Statements-1
False
end
Statements
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for Loop Rules

• Given for Loop Counting Variable kmsn
• The step value s may be negative
• Example k 10-24 produces k 10, 8, 6, 4
• If s is omitted, the step value defaults to 1
• If s is positive, the loop will not be executed
  if m is greater than n
• If s is negative, the loop will not be executed
  if m is less than n
• If m equals n, the loop will be executed only
  once
• If the step value s is not an integer, round-off
  errors can cause the loop to execute a different
  number of passes than intended

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The continue Statement

• The continue statement passes control to the next
  iteration of the loop in which it appears,
  skipping any remaining statements in the body of
  the loop.
• The Following Code Uses a continue

statement to avoid taking the log of a negative
number.
x 10,1000,-10,100 y NaNx for k
1length(x) if x(k) lt 0 continue end y(k)
log10(x(k)) end

• The Result

y 1, 3, NaN, 2
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Remove continue Statement

• Lets Fine Tune the No-Neg-Log Code by COMMENTING
  OUT the if-continue Commands

x 10,1000,-10,100 y NaNx for k
1length(x) if x(k) lt 0 continue
end y(k) log10(x(k)) end

• The Result

y 1.0000 3.0000 1.0000 1.3644i
2.0000
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Use of a Logical MASK

• The use of loops and branching can often be
  avoided, thus creating simpler and faster
  programs by using a logical array as a mask that
  selects elements of another array.
• Any elements not selected will remain unchanged.
• The following session creates the logical array D
  from the 3x3 numeric array B

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Use of a Logical MASK cont

• Logical Mask Session

gtgt B 0, -1, 4 9, -14, 25 -34, 49, 64 B
0 -1 4 9 -14 25 -34 49
64 gtgt D (B gt 0) D 1 0 1
1 0 1 0 1 1
Mask Array ?a Logical that masks out Negative
numbers
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Logical MASK cont
Original B 0 -1 4 9 -14
25 -34 49 64

• Logical Mask Session cont

gtgt B(D) sqrt(B(D)) B 0 -1 2
3 -14 5 -34 7 8 gtgt B(D)
B(D) 50 B 0 49 2 3 36
5 16 7 8
Negative Values Unchanged ? Masked OUT by D(m,n)
0
Positive Values Unchanged ? Masked OUT by D(m,n)
1
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while Loops

• The while loop is used when the looping process
  terminates because a specified condition is
  satisfied, and thus the number of passes is not
  known in advance.
• A simple example of a while loop is

x 5 while x lt 25 disp(x) x 2x - 1 end

• Results from the disp statement are 5, 9, and 17.

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while Loop Statement
Start
Set Loop VarInitial value

• A PreTested DYNAMIC Loop

LogicalDecision

• No. Repetitions UNknown
• MATLAB Syntax
• while Logical Expression
• statements
• end

True
Statements(MUST IncrementLoop Variable)
False
end
Statements
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while Loop Statement
Start
Set Loop VarInitial value

• For the while loop to function properly two
  conditions must occur

LogicalDecision

1. The loop variable must have a value before the
   while statement is executed
2. The loop variable must be changed somehow by the
   statements Inside the Loop

True
Statements(MUST IncrementLoop Variable)
False
end
Statements
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while Loop Example
k 1 x 9 k 2 x 17 k
3 x 33

• The Results

• A simple while loop

x 5k 0 while x lt 25 k k 1 y(k)
3x x 2x-1 end
gtgt y y 15 27 51

• The loop variable x is initially assigned the
  value 5, and it keeps this value until the
  statement x 2x - 1 is encountered the first
  time. Its value then changes to 9. Before each
  pass through the loop, x is checked to see if its
  value is less than 25. If so, the pass is made.
  If not, the loop terminates

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Another while Loop Example
tot 0k 0 while tot lt 10e3 k k 1
tot 5k2 - 2k tot end disp(No.
terms ') disp(k) disp('The Sum ') disp(tot)

• Write a .m- file to determine
• The min. number of terms required for the sum of
  the series 5k2 2k k 1, 2, 3, to exceed
  10,000.
• the sum for this number of terms
• The .m-file and the Results

No. Terms 18 Sum 10203
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The switch Structure

• The switch structure provides an alternative to
  using the if, elseif, and else commands.
  Anything programmed using switch can also be
  programmed using if structures.
• However, for some applications the switch
  structure producesmore readable code than when
  using the if structure.

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MATLAB switch Syntax

• switch input expression (which can be a
  scalar or string).
• case value1
• statement group 1
• case value2
• statement group 2
• .
• .
• .
• otherwise
• statement group n
• end

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switch Example
grade_level input('Hi-School Grade Level.
') switch grade_level case 9 disp('
Freshman') case 10 disp('
Sophomore') case 11 disp(' Junior')
case 12 disp(' Senior')
otherwise disp(' NOT a Hi-Schl Grade
Lvl') end

• This switch Block displays the High School
  Class-Name that Corresponds to a Given Grade Level

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switch Example Results
Hi-School Grade Level. 9 Freshman Hi-School
Grade Level. 11 Junior Hi-School Grade
Level. 13 NOT a Hi-Schl Grade Lvl Hi-School
Grade Level. 10 Sophomore
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Example Prob 4.24

• Consider an Electrical Diode ?

• We can MODEL the V-I Behavior of this Device in
  Several ways

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Problem-24 cont

• The Diode exhibits a form of RECTIFICATION
• i.e., It allows current to Flow in the FORWARD
  direction, But NOT in the REVERSE direction
• Think of a diode as a Check-Valve for
  Electrical Current

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Problem-24 cont

• Now Lets Connect the Diode to
• A Power Source, Vs
• A Useful Load, RL

VL ?

• Next Assume that Vs is a Decaying Sinusoidal,
  Alternating Current (AC) Voltage-Source modeled
  mathematically as

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Problem-24 ? Plot Vs
VL ?
Bruce Mayer, PE 08Jul05 ENGR25 Problem
4-24 file Prob4_24_Vs_plot.m INPUT
SECTION tmax input('Max time in sec ') Vmax
input('Max Supply Potential in V
') CALCULATION SECTION use linspace command
to generate 500 time pts t linspace(0,tmax,500)
Use for-Loop to generate plotting vector,
vs for k 1500 Calc SUPPLY V-Level
vsup Vmaxexp(-t(k)/3)sin(pit(k)) vs(k)
vsup end PLOT SECTION plot(t,vs),ylabel('Loa
d Voltage (V)'),xlabel('Time (sec)'),...
title('Ideal-Diode Rectifier'), grid disp('Plot
Complete')
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Problem-24 ? Plot Vs
VL ?
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Prob 24 cont

• Recall the Ideal-Diode Model ?

• With This Diode Behavior weExpect Load a Voltage
  in this form

VL ?

• Write a MATLAB Program to Plot VL vs t for 0 ?t
  ? 10s

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Problem-24 ? Plot VL Ideal
Bruce Mayer, PE 08Jul05 ENGR25 Problem
4-24a file Prob4_24a_ideal_diode.m INPUT
SECTION tmax input('Max time in sec ') Vmax
input('Max Supply Potential in V ')
CALCULATION SECTION use linspace command to
generate 500 time pts t linspace(0,tmax,500)
Use for-Loop to generate plotting vector, vL for
k 1500 Calc SUPPLY V-Level at the
current t(k) vs Vmaxexp(-t(k)/3)sin(pit(k
)) chk Fwd or Rev condition by if-else
if vs gt 0 vL(k) vs else
vL(k) 0 end end plot(t,vL),ylabel('Load
Voltage (V)'),xlabel('Time (sec)'),...
title('Ideal-Diode Rectifier'), grid
VL ?
VS
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Problem-24 ? Plot VL Ideal
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Prob 24 cont

• Recall the OffSet-Diode Model ?

• With This Diode Behavior weExpect Load Voltage
  in this form

VL ?

• Write a MATLAB Program to Plot VL vs t for 0 ?t
  ? 10s

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Problem-24 ? Plot VL Offset
Bruce Mayer, PE 08Jul05 ENGR25 Problem
4-24b file Prob4_24b_offset_diode.m INPUT
SECTION tmax input('Max time in sec ') Vmax
input('Max Supply Potential in V ')
CALCULATION SECTION use linspace command to
generate 500 time pts t linspace(0,tmax,500)
Use for-Loop to generate plotting vector, vL for
k 1500 Calc SUPPLY V-Level at current
t(k) vs Vmaxexp(-t(k)/3)sin(pit(k))
chk Fwd or Rev condition by if-else if vs gt
0.6 vL(k) vs-0.6 else
vL(k) 0 end end plot(t,vL),ylabel('Load
Voltage (V)'),xlabel('Time (sec)'),...
title('Offset-Diode Rectifier'), grid
VL ?
VS
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Problem-24 ? Plot VL Offset
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Prob 24 Analysis
VL ?

• Compare Plots Side-by-Side

• 0.6V Offset has a large affect when the Vs
  amplitude is only 3V
• OffSet is 20 of amplitude

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Prob 24 Analysis
VL ?

• Plots for 24V amplitude

• Makes less difference
• Note different vertical scales

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All Done for Today
SinusoidalHalfWaveRectifier
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Engr/Math/Physics 25
Appendix
Time For Live Demo
Bruce Mayer, PE Licensed Electrical Mechanical
EngineerBMayer_at_ChabotCollege.edu