Switching Electromagnets:
Making Magnetic Tracks

What if we could draw the tracks we want a train to follow?

These days, we can make our own roller coaster designs and experience them using VR. I wanted to emulate this concept and make a magnetic object move on a platform remotely using a track drawn on a screen.

I don’t think I loved an elective more than HCI (Human computer interaction) in my final year of undergrad. Studying about technology by understanding human behavior, generating ideas and molding designs based on context instilled a sense of inventiveness that was also grounded. The inception of this project came about as we were exploring tangible user interfaces – where humans can interact with digital platforms through the physical environment. Working with tangible media demands not only creativity but also an intuitive representation of nature through technology. For someone who wants to funnel a bit of curiosity and imagination into their work, this was one project I was very excited about.

This video demonstrates a simulation of the project. The tracks are made of electromagnets (arranged as shown) that can be switched on and off remotely using a Bluetooth app. The magnets are modeled as round buttons on the digital interface.

This project aspires to emulate a simulation space for observing the interaction of objects under magnetic field manipulation. This vision links the concept of tangible user interface to enable users to draw patterns on a remote digital platform that manipulates the electromagnet units, referred here as “pixels”, to move the objects in a similar pattern on the 2D platform.

 

Components needed:

  1. A simple electromagnet made from a solenoid of copper wire with a soft iron core.
  2. Switching transistor (here we used a TIP132 npn transistor with a 220 ohm resistor)
  3. Arduino Uno
  4. Bluetooth module (HC-05)
  5. Any kind of foam board to make the platform
  6. Wires, breadboards, and necessary power sources
  7. A smartphone
  8. Lastly, we used bearing balls to demonstrate how ferromagnetic objects can be remotely moved around the platform.

 

Construction:

There were two challenges that we needed to address. One was the switching control in the same circuit as an electromagnet that required a high current to operate. This is where a first year undergrad course on transistors helped us figure out the circuit design. The second challenge was to ensure our electromagnets had instantaneous on-and-off effect. However, this factor varied based on the iron core we used. Some retained the magnetic effect strongly after turning them off, impeding the forward progression of the bearing balls. So, it took an initial phase of experimentation with various types of iron rods available, by analyzing the magnetic effect based on dimension such as volume and diameter, strength of current and diameter of copper wire.

 

The circuit diagram representing one electromagnet
The problem with prolonged demagnetization from using wrong iron cores

After weeks of experimenting and endless troubleshooting (and few minor shocks), the final set-up came together. For the app we used MIT App Inventor to create a simple interface of buttons to connect to the Bluetooth module on the Arduino Board.

After setting up 3x3 electromagnets according to the circuit diagram
The 2D platform still at prototype stage
https://youtu.be/srv5TKfk6Ok

Follow this link to find the video on my channel

Moving forward:

While this iteration of the project fulfilled our initial goal, we realize the that a tangible user interface should also display a fluidity that humans can feel natural interacting with. The vision for this project is to make a digital interface that should feel like drawing with a pen on paper and observing the action at a distance. We wanted to create the joy of making our drawings come to life in a way. Therefore, our next focus is to make the interface  similar to patterns we use as smartphone locks, making the platform larger and creating complex shapes.