Everyone is always busy. This is a fact. So what happens when the doorbell rings at the office? We ignore it. The most annoying is when one of our colleagues forgets to bring the damn RFID card!
So, with a little bit of soldering, programming and creativity we turned the activity of knocking into a password protected door-opening system.
Contact microphones were attached on the glass surface of the door and a servo below the RFID reader. When you enter the five-digit code, by knocking on the correct spots on the window, the servo is activated, which moves the card front of the reader. It’s that simple!
What was used?
servo motor (hacked to 360 but it’s not necessary)
arduino (with standard firmata uploaded)
The system was programmed in MAX.