Locking and unlocking doors is one of the most popular uses of NFC (near-field communication), and you’ve probably used it yourself at an office. The most common way to lock a door with NFC is with a magnetic bolt that’s powered through a relay. They can either be normally-open or normally-closed, depending on whether safety or security is more important in the event of a power failure. But, those tend to be pricey, and most renters don’t have the option of modifying their doors, which is why YouTuber ChrisViral Vlogs’ NFC lock stands out.
Chris’ design works with the kinds of deadbolt locks that are found on most residential doors, and doesn’t require any permanent modification of the door. That keeps the costs down, and keeps you from getting in trouble with your landlord. The locking mechanism for the deadbolt is turned with a stepper motor that has been geared down to gain the torque necessary to reliably lock and unlock the door.
An Arduino Uno controls the stepper motor through a small motor driver, and also constantly monitors an NFC reader for the proper tags. When that tag is scanned from the outside, the deadbolt is unlocked. A magnetic reed switch tells the Arduino when the door has been closed again, and the door is automatically locked. While NFC does have a number of security vulnerabilities, most of them can be addressed, which makes this a good, low-cost option for unlocking your door.