This project was designed with backwards compatibility in mind. With technology evolving rapidly, there are people in parts of our lives that are not necessarily chasing after everything new. Janus is designed to operate with any phone that has SMS capabilities, so even our grandparents who still prefer feature phones and want a smart door will not be left out.
In line with the smart home theme of the H.A.R.D Hack hackathon at University of California, San Diego, the participants built a door that is engineered to require no keys, no PIN codes, no magnetic strips, nothing physical for the guest to interact with! The host/user just needs a phone number with at least SMS capabilities (preferably MMS). The unassuming welcome mat at the door is the next door bell. It is armed with a force resistor that has been tuned in Arduino so that a person of at least 25 kg/55 pounds (which is equivalent to that of a child) will trigger the face-detecting camera. The guest will not be aware of it, as the camera searches for faces. When it detects one, it sends the host/user a photo of the scene with the face highlighted and asks if the host/user wants to unlock the door for the guest. If the user texts unlock, the door will unlock and let the guest in. It will lock back whenever the door is closed again due to the flex sensor installed at the hinge. Multiple phone numbers can be notified, and potentially any phone with SMS capability can send the ‘unlock’ code to unlock the door. So even grandpa who still prefers feature phones is still in control.