For our project, we decided to use a powerful electromagnet controlled by a microcontroller. We have a keypad on which user is able to input a code. If the inputted code is correct, then the magnet turns off and allows the user to turn off the magnet. The inspiration for this project came from a similar project, which created a Thor’s Hammer using an electromagnet that turned on and off based on a fingerprint sensor reader. We wanted to do something similar, but put our own spin on it.
Instead of creating an electromagnet from scratch, we decided to take apart an old microwave to convert the transformer into an electromagnet. A transformer has both a primary and secondary coil winding, and so the secondary coil needed to be cut out of the iron core’s housing. Then an angle grinder was used to cut the the weld to cut the top off. Then the primary coil was removed, and placed at the bottom of the iron housing. Masking tape was placed on the inside of the iron housing so that the primary coil was not making contact with the housing.
In order to turn the electromagnet on and off we needed to use an electronic relay with a simple circuit. We used a Grove Relay, which was purchased from FirstBuild. The circuit was simply a battery pack configuration connected to the electromagnet, and the relay was used to open and close the circuit. We also decided to play a simple tone with a speaker when the electromagnet was successfully turned off (i.e. the relay opened). Pictured here is the A3BU, a battery pack with four AA’s, a small speaker, and our electromagnet.
Here is a short video demonstrating the operation of the electromagnet. It shows the user initially entering an incorrect password, and the magnet staying on. Then the user entering the correct password and the magnet turns off. Then after pushing a button on the keypad, the magnet turns back on.