🤖 Lab - DC Motor Control

🤓 Overview and learning outcomes

Direct Current (DC) motors are some of the most versatile actuators we have. This lab will introduce the physical concepts of DC motors and students will gain an understanding of how voltage, current and resistance interact to manipulate simple DC motors. We will start with some simple voltage to RPM calculations and then proceed to controlling the motors with our Raspberry Pis.🚀

Lab Setup

1. Set the power supply to 3V and turn off the power supply.
2. Attach the wheel to the DC motor hub.
3. Attatch the hub to the motor shaft.
4. Mark the wheel with Sharpie to give a reference point for measuring RPMs.
5. Connect your DC motor to the power supply using the aligator clips.

While the power supply is off, take a photo of the motor connected to the power supply. Later, you will upload that photo to this lab.

Procedures

1. You will be recording various RPM levels as voltage values are adjusted for each motor. You will record voltages from 3.0 to 12.0 volts in increments of 0.5V each step (3.0, 3.5, 4.0...12.0). To do this, set the motor at a predefined voltage and then connect the leads and turn on the power. While one person keeps track of time, the other counts the number of revolutions.
2. Record your results for your specified motor on this sheet.
3. Record all observations for your motor.
4. When everyone is done recording observations, copy the entire spreadsheet into your google drive account.
5. Make a a new sheet and name it "All_Motors". The rows should be the voltage values while the columns should be the motor model. Paste all RPM results into this sheet in the appropriate column.
6. Make a line chart of all observations (Insert > Chart to open the chart wizard). The chart should represent each motor with a different colored line and show RPMs changing (y-axis) in relation to voltage (x-axis).

💻 Terms to know

• Voltage
• Revolutions per Minute
• Correlation
• linear relationship
• x-axis
• y-axis

📝 Next steps (Graded)

Answer the following questions in a markdown file titiled, "observations.md":

1. What is the general relationship between voltage and RPMs in a DC motor?
2. Would you describe this relationship as linear? Explain.
3. What statement would you use to accurately describe the relationship between these two variables?

Insert the photo from earlier into the .md file and a screenshot of your chart.

📚 Resources

• How to Make a Line Chart in Google Sheets
• How to Make a Line Graph in Google Sheets (Step-by-Step)
• Khan Academy: Understanding Linear Relationships