The Electromagnetic Tether Robot was built as part of the course EECE 281 by me and 5 other teammates. The transmitter contains an 8051 microcontroller which drives an H-bridge, which in turn produces oscillations in the LC circuit on the same board, emitting a magnetic field. The receiver circuit is connected to the robot, and it is supposed to maintain a constant preset distance from the receiver by measuring the magnetic field and constantly adjusting itself. This preset distance can be changed by the user on the transmitter end.
The innovative part about our project was how the signal was sent from the user to the transmitter. We made an Android app for this purpose, instead of using push buttons on the transmitter. The app sends signals through the phone’s audio output. A digital signal gets converted to an audio signal on the phone, and gets converted back to a digital signal on the transmitter. This signal is sent to the receiver by the same LC circuit which produces the magnetic field for the robot to maintain constant distance.
Other than changing the preset distance, the user can also send various other commands to the robot such as “Rotate 360°”, “Start/Stop Following” and “Parallel Park” using the app.