Potentiometer (Variable Resistance Circuits)

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What to Add Next time you update?

  • 9/16/2019
  • 8/23/19
    • WOW… add Step by Step for first table… and probably walk through each step as a class… then have them do table 2,3,4 on their own
    • Ohms law review… with quick math to show going from one formula to another
    • slide 8? add more slides with “what the power supply ‘Sees’”
    • also slide 8 add values to the resistors and show adding them together
    • Slide 11, maybe update slide to be better so you don’t have to explain the “X”
    • update slide 14-what ever with TinkerCAD images
    • Slit this into 2-3 presentations with the Potentiometer as a separate presentation and the light sensitive resistor as a separate presentation
  • 2018
    • Worksheet with 3 and 4 resistors
    • Create worksheet of tables
    • Add Hypothesis and Questions
    • Add Lab and Lecture Objectives
    • Add equipment needed
    • Add science standards
    • Review links for additional content

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See Appendix A,B,C, for Licensing & Attribution Information

CC BY-NC-SA 4.0

https://creativecommons.org/licenses/by-nc-sa/4.0/

https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode

GNU Public License

Any included Programming Code Is licensed under GNU General Public License v3.0

EUPL (European Union Public Licence) Code and Content is also licensed under EUPL 1.2 or later

3

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Quick Review

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Trick to Remember Ohm’s Law

V

I

R

I

V

R

=

V=I*R

R

V

I

=

V

I

R

V

I

R

V

R

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Series Circuits - Total Voltage?

+ |

+ |

?

Yes

B

A

C

A

C

Is the same voltage measured between A and C?

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What is a potentiometer?

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Potentiometer Videos

B

A

C

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Pins On A Potentiometer

B

A

C

B

A

C

A

B

C

B

A

C

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Series Circuits - Total Resistance?

B

A

C

The Rt is the “Total” Resistance from the pin A & pin C

Rt

B

A

C

Rt

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Series Circuits - Voltage Across Rx?

B

A

C

The Rx is the Resistance between or “across” points A and B

Rx

B

A

C

Rx

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Series Circuits - Voltage Across Rx?

B

A

C

Rx

B

A

C

Rx

The Rx is the Resistance between or “across” points B and C

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TinkerCAD Circuit - Resistance

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TinkerCAD Circuit - Voltage

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TinkerCAD Circuit - Voltage

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Series Circuits - Total Voltage?

+ |

B

A

C

Vt

B

A

C

The Vt is the “Total” voltage from the + side of the battery to the - side of the battery

Vt

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Series Circuits - Voltage Across Rx?

+ |

B

A

C

The Vx is the voltage between or “across” points A and B

Vx

Rx

B

A

C

Vx

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Series Circuits - Voltage Across Rx?

+ |

B

A

C

The Vx is the voltage between or “across” points B and C

Vx

Rx

B

A

C

Vx

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TinkerCAD Circuit - Voltage

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LAB:

Voltage Divider - Calculating the R1 and R2 given a V2 & V1

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LAB #2

Log Some Data

  • Build and Measure 3-4 positions
    for the Potentiometer
  • Measure Voltage across A<-->B and B<--> C

Circuit

Measured V1

Measured V2

Measured Vt

Calculated R1

Calculated R2

Measured Current

1

2

3

4

B

A

C

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Series Circuits - Total Voltage?

+ |

B

A

C

Vt

B

A

C

The Vt is the “Total” voltage from the + side of the battery to the - side of the battery

Vt

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LAB #2

Log Some Data

  • Build and Measure 3-4 positions
    for the Potentiometer
  • Measure Voltage across A<-->B and B<--> C

Circuit

Measured V1

Measured V2

Measured Vt

Calculated R1

Calculated R2

Measured Current

1

2

3

4

B

A

C

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Series Circuits - Voltage Across Rx?

+ |

B

A

C

The Vx is the voltage between or “across” points A and B

Vx

Rx

B

A

C

Vx

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LAB #2

Log Some Data

  • Build and Measure 3-4 positions
    for the Potentiometer
  • Measure Voltage across A<-->B and B<--> C

Circuit

Measured V1

Measured V2

Measured Vt

Calculated R1

Calculated R2

Measured Current

1

2

3

4

B

A

C

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Series Circuits - Voltage Across Rx?

+ |

B

A

C

The Vx is the voltage between or “across” points B and C

Vx

Rx

B

A

C

Vx

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LAB #2

Log Some Data

  • Build and Measure 3-4 positions
    for the Potentiometer
  • Measure Voltage across A<-->B and B<--> C

Circuit

Measured V1

Measured V2

Measured Vt

Calculated R1

Calculated R2

Measured Current

1

2

3

4

B

A

C

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Picking V2 and Solving for R1 and R2

  • We are going to Pick a V2
    • 1.67v
  • Turn the Potentiometer until voltage of V2 is 1.67v between or “across” points B and C

+ |

R1

R2

5 v

V2

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Picking V2 and Solving for R1 and R2

  • We are going to Pick a V2
    • 1.67v
  • Turn the Potentiometer until voltage of V2 is 1.67v between or “across” points B and C
  • We know that Rt Is 10KΩ (that’s the value to the Potentiometer)

+ |

R1

R2

5 v

R2

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Picking V2 and Solving for R1 and R2

  • We are going to Pick a V2
    • 1.67v
  • Turn the Potentiometer until voltage of V2 is 1.67v between or “across” points B and C
  • We know that Rt Is 10KΩ (that’s the value to the Potentiometer)
  • Which then let us calculate the R2 and thus R1

+ |

R1

R2

5 v

R2

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equation to solve for Rx

+ |

R1

R2

5 v

We are going to need to use this Formula to solve for R2, and then R1

 

Use the same Equation to solve for R2 with the algebraic equation

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LAB #2

Log Some More Data

  • Build and Measure 3-4 positions
    for the Potentiometer
  • Measure Voltage across A<-->B and B<--> C

Calculate R1 = ??Ω, R2 = ??Ω

Circuit

Measured V1

Measured V2

Measured Vt

Calculated R1

Calculated R2

Measured Current

1

2

3

4

B

A

C

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Lab #3 Connect it to your Arduino

int potPin = A2; // select the input pin for the potentiometer

int ledPin = 13; // select the pin for the LED

int val = 0; // variable to store the value coming from the sensor

void setup() {

pinMode(ledPin, OUTPUT); // declare the ledPin as an OUTPUT

}

void loop() {

val = analogRead(potPin); // read the value from the sensor

digitalWrite(ledPin, HIGH); // turn the ledPin on

delay(val); // stop the program for some time

digitalWrite(ledPin, LOW); // turn the ledPin off

delay(val); // stop the program for some time

}

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Math behind the measurements

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How Do you find the Resistance given a known voltage Divider?

  • We know that you can find Vx When you know Rx

  • How do we manipulate to solve for Rx?

t

 

t

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manipulate to solve for Rx

t

 

t

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manipulate to solve for Rx

t

 

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manipulate to solve for Rx

t

 

t

 

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manipulate to solve for Rx

t

 

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manipulate to solve for Rx

t

t

t

 

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manipulate to solve for Rx

t

t

t

 

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manipulate to solve for Rx

t

 

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manipulate to solve for Rx

t

 

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Picking V2 and Solving for R1 and R2

  • V2 = 1.67v and Rt = 10KΩ
  • Which then let us calculate the R2

+ |

R1

R2

5 v

V2

t

 

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Picking V2 and Solving for R1 and R2

  • V2 = 1.67v and Rt = 10KΩ
  • Which then let us calculate the R2

+ |

R1

R2

5 v

V2

 

10KΩ * 1.67v

5v

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Picking V2 and Solving for R1 and R2

  • V2 = 1.67v and Rt = 10KΩ
  • Which then let us calculate the R2

+ |

R1

R2

5 v

V2

 

33.4K

R2

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Picking V2 and Solving for R1 and R2

  • V2 = 1.67v and Rt = 10KΩ
  • Which then let us calculate the R2

+ |

R1

R2

5 v

V2

R2 = 33.4K

What is R1? V1? Can you calculate It?

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Picking V2 and Solving for R1 and R2

  • Vt = 5v, V2 = 1.67v, R2 = 33.4KΩ,
    and Rt = 10KΩ

+ |

R1

R2

5 v

V1

What is R1? V1? Can you calculate It? Write it in your Lab book

 

t

 

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Lab: Build the circuit you just calculated

  • Vt = 5v, V2 = 1.67v, R2 = 33.4KΩ,
    and Rt = 10KΩ

+ |

R1

R2

5 v

What is a standard Resistor value close to R2 = 33.4KΩ?

What can you pick for R1?

Build, then Measure your circuit. Does it match your calculated values?

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Reference

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Worksheet – Lab / Quiz

  • Objectives
    • Demonstrate knowledge of Ohm's Law
    • Demonstrate proper use of a Digital Multimeter
    • Demonstrate knowledge of Series Circuits fundamentals
    • Apply the Voltage divider principles
  • Equipment needed
    • 5 volt DC power supply and breadboard adaptor
    • DMM
    • Bread board
    • Assorted resistors and wires

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Electronic symbols

+

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Reference Slides

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Learning Domain, CTE Standards and Stuff like that…

  • Learning Domain

[ ] cognitive [ ] affective[ ] psychomotor

      • What are some cognitive skills required for success in your pathway?
      • What are some affective skills required for success in your pathway?
      • What are some psychomotor skills required for success in your pathway?
  • Time:
    • Lecture
    • Lab

  • Standards
    • CTE
    • CCSS
    • NCSS

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Lab Setup for Measuring Continuity

Probe the Breadboard to prove you understand

the connections

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Appendix

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Can I Get A Copy Of These Slides? Yes, Probably...

Most presentation lecture slides can be found indexed on www.steamclown.org and maybe blogged about here on Jim The STEAM Clown’s Blog, and on STEAM Clown’s Mechatronics Engineering Google site, where you can search for the presentation title. While you are there, sign up for email updates

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Appendix A: License & Attribution

  • This interpretation is primarily the Intellectual Property of Jim Burnham, Top STEAM Clown, at STEAMClown.org
  • This presentation and content is distributed under the Creative Commons License CC-BY-NC-SA 4.0
  • My best attempt to properly attribute, or reference any other sources or work I have used are listed in Appendix C

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Please maintain this slide with any modifications you make

Appendix B: License & Attribution

  • This interpretation is primarily the Intellectual Property of Jim Burnham, Top STEAM Clown, at STEAMClown.org
  • The programming code found in this presentation or linked to on my Github site is distributed under the:
  • My best attempt to properly attribute, or reference any other sources or work I have used are listed in Appendix C

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© Copyright 2019 STEAM Clown

Please maintain this slide with any modifications you make

Appendix C: Primary Sources & Attribution for Material Used

  • <Add Your Logo and Attribution here>
  • Much of this interpretation is primarily the Intellectual Property of Jim Burnham, Top STEAM Clown, at STEAMClown.org, My best attempt to properly attribute, or reference any other sources or work I have used are listed below. The programming code found in this presentation or linked to on my Github site is distributed under the:
  • <Add additional attribution here>>

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Sources

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Lesson 7.1 - Potentiometer (Variable Resistance) - STEAMClown - Google Slides