Torque Coils Magnetic Field Alignment

Learning Objective

• Validate the system’s functionality and ability to align to a targeted magnetic field, with the satellite suspended in the air by a string on one of its corners

Pre-Requisites

• Obtain IMU’s acceleration, angular velocity, and magnetic field data through COSMOS web

System Components

• Solar Panel Board (Embedded Torque Coils)
• Raspberry Pi
• Battery Board
• PDU Board
• Payload Board
• Fishing Line
• 9 “female” test wires
• Power Supply
• Test leads for Power Supply
• Multimeter with test leads

Procedure

• Check torque coil functionality by varying power and measuring the strength of the magnetic field
  • Procedure to connect to power supply while varying voltage
  • Measure variation of the magnetic field with respect to power with a phone app
• Ensure that the torque coil can be commanded with Raspberry Pi and the battery
  • Connect torque coil to Raspberry Pi and battery
  • Measure variation of the magnetic field with respect to power with a phone app
  • Additionally, measure with a multimeter
• Measure the torque coil capability by pointing it along the magnetic field vector
  • Turn on the torque coil to its maximum magnitude
  • Observe and measure the motion
  • String the system up with fishing line such that when the system hangs, the solar panel can align with the magnetic field vector

Check Torque Coil Functionality

You will need to download an app that can detect magnetic fields. The application that was utilized in this demonstration is seen below. Feel free to download whatever app is compatible with your device. Anything that is free should be sufficient. Please do not pay for an app for this experiment. Take note that phone apps will vary in their efficiency and overall efficiency is not extremely high via a cell phone app, however, you will be able to visualize the reactions of the magnetic field and understand what is going on in your little satellite world.

You will need:

• Power supply

• Set of wires for the power supply

• 1 solar panel

• Connector for solar panel

View of the entire initial setup:

Plug your solar panel connector into your solar panel in the spot marked J1.

Then connect your leads to the solar panel connector wires. The positive wire to one of the wires on the solar panel connector wire. The negative wire to the remaining wire on the solar panel connector wire. It is irrelevant which wire goes where, just be sure that they do not touch each other.

Set your power supply to 5V and .5A.

Take out your phone and open the app that you installed. You will need to place your phone directly on top of the solar panel as shown in the image below.

As your phone sits on top of the solar panel, change your voltage on the power supply. Varying the voltage from about 1 volt to 10 volts. Monitor what happens to the readings on your phone app. You should see a drastic variation in values.

You have officially measured a magnetic field!

Great Job!!

Ensure that the Torque Coil can be Commanded with Teensy and a Power Supply

• Hardware needed
  • OBC with Teensy
  • PDU
  • Antenna Board
  • ANT J15 wire
  • 2x male-to-male jumper Cables
  • Power supply
  • 2x alligator clips
  • Micro-USB to USB cable

Place the OBC on top of the PDU and push the headers together.  The headers should evenly match up and no extra ones should be showing on any side of the PC104 connectors

Take ANT J15 wire and place the end with the black wire in the third pin slot into the OBC J12 connector

Connect the other end of the ANT J15 wire (the one with the black wire at the fourth pin slot) to the antenna board J15 connector

Next, you will need to plug the two male-to-male jumper cables into the PC104.  The first one will be plugged into the top row, 3 holes over from the right end of the board.  This is the ground cable.  The next one will be plugged in on the top row, 9 holes over from the right side of the board.  This will be power.

Connect the power supply to the jumper cables with alligator clips.  The ground (black) should be connected to the able three holes from the right and power (red) should be connected to the cable nine holes from the right.

Set the power supply to 7.5V and .5A.  When turned on, it should read 7.5V and ~.1A.  The amps may vary depending on what the OBC board is currently programmed to do.

Finally, connect the micro-usb cable to the micro-usb connecter (J17) on the antenna board.

Open Arduino IDE and ensure that the Teensy is connected to your computer.  The top left drop-down menu should have “Teensy 4.1” with a cube next to it.

Open the pdu_comm script located in examples>artemis-cubesat>

• If you do not have the artemis-cubesat library or Arduino IDE follow the instructions from the Communications Hardware Lab

Hit the upload button which is the arrow located at the top left side of the screen.

The serial monitor should appear like the image below.  If it does not automatically pop up, you can click the magnifying glass icon in the top right to open it.  If the serial monitor is blank, type “ping” into the message bar.  The response should be “got pong”.

For this part of the lab, we will be focusing on 2 different connectors on the PDU. This will require the PDU to be on its side while still connected to the power supply. Be careful as to not let the two wires touch as you are getting your measurements.

Type the command “set hbidge1 on” to turn on hbridge1.

The response in the serial monitor should look like this.

Measure any of the pins on PDU J7 connector.  They should read ~5V.

Type the command “set hbridge1 off” to turn off hbridge1.

The response in the serial monitor should look like this.

Type the command “set hbidge2 on” to turn on hbridge2.

The response in the serial monitor should look like this.

Measure any of the pins on the PDU J8 connector.  They should read ~5V.

Type the command “set hbridge2 off” to turn off hbridge2.

The response in the serial monitor should look like this.

Measure the Torque Coil Capability by Pointing it Along with a Magnetic Field Vector

Torque coils – Information

Function: React with Earth’s magnetic field to change the orientation of the satellite.

• Number of turns: 60 turns
• Resistance of the wire: 35.8 ohms
•  Supply voltage to the coils: 5V
• Voltage range of coils: 3.3V – 5V
• Power of a single-coil: 0.7 W
• Calculated Magnetic Moment: 1.22 *10^-2 Am^2
• Tentative torque generated: 2.43*10^-6 N*m
• Coils are connected in parallel

Math stuff

Torque on a current loop equation:

Magnetic Moment Equation:

Power consumption equation:

Time of rotation equation:

How it works:

Command will gather data from both the GPS and IMU to track the satellite’s location, which will then send that data to the computer to generate how much current needs to be sent through the coils. Once completed, the current will flow through the coils, thus creating enough torque to point the satellite towards the desired location.

For this part of the lab, you will need to be set up similar to how you were in the first  part of the experiment, minus your cell phone and adding in a magnet and some tape

You will need:

• A piece of tape about 4-6 inches
• Power supply

• Set of wires for the power supply

• 1 solar panel

• Connector for solar panel

• Strong magnet

Plug your solar panel connector into your solar panel in the spot marked J1.

Take your solar panel and gently hang it from some type of hanging apparatus.

Then connect your leads to the solar panel connector wires. The positive wire to one of the wires on the solar panel connector wire. The negative wire to the remaining wire on the solar panel connector wire. It is irrelevant which wire goes where, just be sure that they do not touch each other. Tape your wire so that it does not interfere with the setup.

Now get your solar panel as still as possible.

Once it is nice and still set your power supply to 10V and .5A.

You will see your ever so still solar panel start to sway gently in the wind due to the voltage activation. This is reacting to the earth’s magnetic field! (so cool!!) However, since we are on Earth there is a lot of variables the get in the way of seeing any drastic movements.

This is where our magnet will come in. Place the magnet as close as possible to the solar panel. Feel free to go from either side or alternate front and back. You will see the solar panel start swinging about.

Look at you like a magical magnetic wizard!

Great job today!

^{How the torque coils should respond to the magnet.}