Stepping Up Security

You might think that you have the world’s worst neighbors, but you’ve got nothing on Roni Bandini. Not long ago, Bandini created a device called the Reggaeton Be Gone that listened for a specific type of music, then jammed the nearby Bluetooth speaker of a neighbor that insisted on blasting reggaeton music way too early in the morning. So, did that solve all of his issues with neighbors? Hardly. Bandini says that where he lives in Buenos Aires, drunks and thieves are known to frequently come right up to people’s doorsteps and make themselves at home.

With another problem to solve in the neighborhood, Bandini once again built a device that is a bit over-engineered and slightly passive-aggressive, yet also very humorous (at least if you are not on the receiving end), to address it. Named Step Guard, this system monitors one’s doorstep and watches for the presence of people. If some unwelcome visitors are hanging around, Step Guard will blare an annoying horn sound or a recorded message warning them to leave the entryway.

After starting out with some sophisticated solutions for person detection involving mmWave radar sensors and cameras, Bandini ultimately settled on a lower-tech solution due to issues with false positives and limited wireless connectivity that kept coming up. The final solution made use of a DFRobot Beetle ESP32C3 development board with an ultrasonic distance sensor that was placed above the doorstep. This simpler setup sent Bandini a message, and also communicated with another computing unit that was located indoors, via Telegram whenever a person was detected.

The indoor unit was built around a UNIHIKER single-board computer with a built-in touchscreen display. Powered by a custom Python application, this device waits for a signal from Telegram, then plays audio through a small USB sound board connected to a three watt amplifier. All of the actions taken by Step Guard are also logged by this unit.

To finish off the build, the outdoor unit was put in a waterproof case, while the indoor unit was fitted into a custom 3D-printed case designed with Autodesk Fusion. Buttons on the indoor device also allow the owner to change the type of sound that the system plays, or mute it entirely if they are feeling like having some company.

Since building Step Guard, Bandini has found a steady stream of willing (but unaware), err…, beta testers. The device is having the desired effect. As you might expect, people do not really like hanging out with a loud alarm blasting in their ears. After seeing this project in action, I can't help but wonder if Step Guard would work on door-to-door salespeople.

In the project write-up, Bandini discusses the setup of the hardware and has circuit diagrams to help others get their own Step Guard off the ground. Source code is also available to help speed up the build process.