We've all seen those smart home devices such as the Ring doorbell, or those countless Bluetooth-enabled smart locks. We've also heard the horror stories about these devices: from the Ring doorbell's camera footage being view-able by Ring employees, to Bluetooth door locks being a bit unreliable. These devices are also usually expensive, with starting prices at $150 USD. We wanted to create an affordable smart lock that would also be free from any sort of remote interference. Therefore, LockMate was born.
What it does
LockMate uses a near-field communication breakout board, a standard servo motor, and a 16x2 LCD screen. It comes with one NFC key card that acts as a programmer key, allowing users to add up to 10 keys to the system. When a valid key card is brought close to the sensor, the servo rotates, unlocking the door. The lock will wait for a few seconds, and then rotate the servo again, locking the door. If any other NFC tag is brought close to the sensor, the LCD screen will display an error message and the lock mechanism will not be moved.
How we built it
We first started by verifying the NFC breakout board and servo motor we received were both operational. We used separate programs, each individually testing the NFC board and servo motor. After this, we began writing the code to integrate the two systems. We added the LCD screen after the lock mechanism was confirmed working, and continued testing to ensure the motor works as expected.
Challenges we ran into
One big challenge that we ran into was that the servo motor would continue rotating after the lock mechanism was moved to the unlock position. We contemplated switching the motor to a stepper motor, but then found a quick fix - by using the Stepper Arduino library with the servo motor, we were able to move the lock mechanism properly.
Accomplishments that we're proud of
Personally, I'm proud that we were able to get everything working. It was a little difficult, but with perseverance and hard work we accomplished our goal.
What we learned
This was our first time with embedded systems development, so we learned a ton about how Arduinos communicate with motors and other peripherals, and about electronics in general. We also learned a bit more on how the NFC standard works.
What's next for LockMate
We hope in the near future to integrate all the parts of this prototype into a fully fleshed product, with a target price of about $70-$80 USD. We'd like to either update the current servo motor, or completely swap it out for a solenoid.