ELECTRIC CIRCUITSECSE-2010

Spring 2003 Class 3

ASSIGNMENTS DUE

• Today (Thursday):• Will introduce PSpice• Activity 3-1 (In Class) using PSpice• Will do Experiment 1; Report Due Jan 27

• Next Monday:• No Classes – Martin Luther King Day

• Next Tuesday/Wednesday:• HW #1 Due• Activities 4-1, 4-2, 4-3 (In Class)• 4-2 in NOT in your Supplement

REVIEW

• Kirchhoff’s Laws: KCL, KVL Current Into Node = Current Out of Node

Sum of Voltages Around any Closed Path = 0

• Resistors in Series:

• Resistors inParallel:

in out

i's i's KCL

around path

v's 0 KVLeq 1 2 3R R R R ...

eq 1 2 3

1 1 1 1...

R R R R

KIRCHHOFF’S LAWS

1i 2i

3i

1 2 3KCL: i i i

1v

3v

2 v

1 2 3KVL: v v v

RESISTORS IN SERIES

1R2R eqR

eq 1 2R R R

v

v

i i

VOLTAGE DIVIDER RULE

• v1 = i R1 = V/Req x R1

• v1 = [R1/(R1 + R2)] V

• v2 = i R2

• v2 = [R2/(R1 + R2)] V

• Elements in Series• v1 ~ R1

• v2 ~ R2

V R R

R v

21

11

V R R

R v

21

22

RESISTORS IN PARALLEL

1R2R eqR

1 2eq

1 2

R RR

R R

v

v

i i

CURRENT DIVIDER RULE

• i1 = [R2/(R1 + R2)] i

• i2 = [R1/(R1 + R2)] i

• Elements in Parallel• i1 ~ R2

• i2 ~ R1

i R R

R i

21

21

i R R

R i

21

12

PSPICE

• Widely Used Simulation Package Industry Standard for Circuits and Electronics

• Student Version is FREE http://cadencepcb.com/products/downloads/PSpicestudent/

default/asp

We will use PSpice A/D and Schematics Could use Capture in place of Schematics

• Get a Copy and Use it Often

PSPICE

• PSpice has Many “Rules”: Will build up slowly

• Use PSpice for Circuits that are Computationally Challenging:

• Will Often Analyze a Circuit to Learn Principles - Then “test” with PSpice:

METHODS FOR PSPICE

• Circuit File Method: Draw Simulation Diagram Create Circuit File (lines of code you type in) Run Circuit File Using PSpice A/D Observe Output (Probe or Output File)

• Schematics (or Capture) Method: Create Circuit Diagram (Drag and Drop) Set up Analysis Run Simulation (PSpice A/D) Observe Output (Probe or Output File)

ACTIVITY 3-1

6 2

12

3 12

i

v

2v

23 v

eqPlot v vs. i Find R

Resistive Bridge Circuit

eqR

Nothing in Series or Parallel!

eq

vR

i

2 23Will also find v , v

CIRCUIT FILE METHOD

• Create Simulation Diagram: Original Circuit Label Nodes, Name Elements, Identify Sources

• Create Circuit File: Lines of code describing circuit and analysis Must save as <filename>.cir Tells PSpice what to do

• Run Circuit File using PSpice A/D: Observe Output Output File or Plot using Probe

SIMULATION DIAGRAM

• Circuit Diagram but with all Nodes and all Elements Labeled for PSpice

• Each Node must have a unique Number

• Each Element must have both a Name and a Value• Both Active and Passive Elements

SIMULATION DIAGRAM

6 2

12

12 3

1 A

1

0

2 3

R12

R20

R13

R30

Simulation Diagram for PSpice

i

R23

eq

Note:

v(1)R

1 A

CIRCUIT FILES

• Circuit File Describes Circuit to PSpice and Tells PSpice What to Do:

• First Line Not Used by PSpice: => Name

• To Describe a Current Source:i 0 1 DC 1

Name of Source = i; “i” means current (i or I)

Current flows from Node 0 to Node 1

DC Source

1 Amp

CIRCUIT FILES

• To Describe a Voltage Sourcev4 1 0 DC 2

Name of Source = v4; “v” means voltage

Positive terminal is Node 1

Negative terminal is Node 0

DC Source

2 Volts

CIRCUIT FILES

• Resistors:R45 2 3 12

Name of Resistor = R45; “R” => Resistor

Connected between Nodes 2 and 3

Positive Terminal is Node 2

Negative Terminal is Node 3

Resistance is 12 ohms

COMMANDS

.dc lin i -1, 1, 0.1

Perform a DC Analysis

Do a Linear Sweep

Sweep the variable named i

Sweep i from -1 Amp to +1 Amp in steps of 0.1 Amps

COMMANDS

.probeTells PSpice to run Probe after performing

the specified circuit analysis

.endTells PSpice that the file is at the end

Will Add More Commands Later

PROCEDURE

• Create Circuit File from Simulation Diagram Save as <filename>.cir

• Open PSpice A/D:• Open Circuit File:• Run Simulation• Observe Output

ACTIVITY 3-1

6 2

12

12 3

1

0

2 3

R12

R20

R13

R30

Simulation Diagram for PSpice

i 1 A

eq

Note:

v(1)R

1 A

v

iLabel Nodes

Name Elements

ACTIVITY 3-1

• Open PSpice A/D

• Under File: Select New - Text File

• Type in Circuit File

• Save as <filename>.cir

ACTIVITY 3-1• Circuit File Activity 3-1 * PSpice does not use first line

i 0 1 dc 1

R12 1 2 6

R13 1 3 2

R23 2 3 12

R20 2 0 3

R30 3 0 12

.dc lin i -1, 1, 0.1

.probe

.end

ACTIVITY 3-1• Under Simulation: Select Run <filename>

• If Errors: => Error Message => Correct

• If it Runs, Probe comes up automatically

• Horizontal axis = i (from -1 to + 1)

• Under Trace: Select v(1)• v(1) = Voltage at Node 1

• Note that Req = 5 ohms

SCHEMATICS METHOD

• Create Schematics Diagram: Same Circuit using Schematics Parts Drag and Drop; Similar to LogicWorks Rotate Elements using Control R or Control F

• Set up Analysis: Choose what you wish to do

• Save as <filename>.sch

• Simulate using PSpice A/D: Observe Output Output File or Plot using Probe

ACTIVITY 3-1

Schematics Diagram

SCHEMATICS METHOD

• Open Schematics: Select New Locate “Parts”; Drag and Drop Sources are Passive Elements in PSpice!

Must put in i = -1 A to get +1 A Add Wires using Wire Icon Must always include Earth Ground! Change Names and Values of Elements by

Doubleclicking on them Save as <filename>.sch

SCHEMATICS METHOD

• Under “Set up Analysis” Icon: Select DC Sweep of Current Source, -1 to +1 A Will use other options later

• Click “Simulate” Icon: Error Messages if Errors Observe Output Same as before except for Sign Change Horizontal Axis to –i to get positive slope Much Quicker once you get used to it

MULTIMETER MEASUREMENTS

• Model for Real Voltmeter: Ideal Voltmeter in Parallel with RM

Ideal Voltmeter Draws No Current RM = “large”; Typically a few Mohms

• Model for Real Ammeter: Ideal Ammeter in Series with Rm

Ideal Ammeter has no voltage drop Rm = “small”; Typically a few ohms

VOLTMETER

VMR

i 0

VMR Voltmeter Resistance

Large (few M 's)

AMMETER

AMR Ammeter Resistance

Small (few 's)

AMR

v 0

EXAMPLE

10 V

10

10 v

Using Voltage Divider Rule:

10v (10) 5 Volts

10 10

Let's Measure with a Real Voltmeter

EXAMPLE

10 V

10

10 10 M Ideal

VM

eqR 10 10 M 10

VM reads 5 Volts

EXAMPLE

10 V

10 M

10 M 10 MIdeal

VM

eqR 10 M 10 M 5 M 5

VM reads (10) 3.33 Volts5 10

Meter affects the measurement

EXPERIMENT 1• Use E3631A Voltage Source:

+ 25 V output; +, Com Adjust output to be + 12 Volts

• Think About Model for Ammeter: With Switch Open; Current flows thru Meter• Measures current as if Switch were Closed

With Switch Closed; Current flows thru Switch• Ammeter measures 0; as if Switch were Open

EXPERIMENT 1a

12 V

2 k

5.6 k 3 k2v

1 v 2i

iUse a Wire to Simulate Switch

EXPERIMENT 1b

10 V

R

R VM

VM

R 220 , Record v

Re peat with R 10 M ; Determine R

v