Original door lock based on Arduino and capacitive sensor

Massachusetts Institute of Technology Rob Hemsley made an original door lock based on an Arduino and a capacitive sensor.
This is the second version of the lock, the first version of the lock was developed on the basis of RFID, its main disadvantage is the high cost of RFID equipment: you had to spend about $ 80 on one lock.
The new version uses a capacitive sensor connected to a metal door handle. This solution is cheaper and more practical (no need to carry an RFID card, no RFID equipment taking up additional space).

The device detects the touch of a person’s hand on the door handle and monitors the intervals between hand touches of the door handle. If the combination of touches on the handle matches the one stored in the EEPROM, the door will open.

The existing door opening code can be quickly and simply changed: just touch the external door lock and then “knock” a new code on the handle.

The video shows the lock device in action, as well as the process of changing the opening code.

The door is opened with a servo that is attached to the internal lock. The capacitive sensor is attached to the metal handle of the door with an ordinary copper strip.

The capacitive sensor is sensitive to environmental changes, which can lead to interference and false alarms. The device has a mechanism to counter this: an automatic calibration occurs every few minutes. Of course, this is not an ideal solution, but it works well and eliminates the need to carry an RFID card with you everywhere.

For this device you will need:

  • Arduino uno
  • Servo
  • Resistor (25 MΩ resistance)
  • Fiberboard sheet (for mounting the servo drive and lock)
  • Few meters of wire
  • Strip of copper

The full source code of the project is available in the repository on GitHub ,
and the drawings for attaching the servo to the lock are here .