AI Smart Door Lock based on nRF9160

Client

A property security company requiring a retrofit cellular door lock that works in buildings without Wi-Fi and provides real-time access logging for landlords.

Challenge

Integrating a camera, motor, and LTE modem into a standard 50mm door lock form factor while achieving 1-year battery life on 4xAA batteries.

Product Concept & Architecture

The Nordic nRF9160 SiP provides both LTE-M connectivity and application processing. A GC032A IR camera captures visitor images. A miniature brushless DC gear motor drives the deadbolt via a custom planetary gearbox (100:1 reduction).

Engineering Solution

The firmware on Zephyr RTOS implements a duty-cycled wake schedule: the camera and face recognition subsystem activate only when the capacitive touch keypad or doorbell button is pressed. Face recognition uses a quantized MobileNet model running on the nRF9160's Cortex-M33. LTE-M data transmission is batched — all access logs upload once daily unless a tamper event is detected, triggering immediate alert.

Result

Sub-1.2 second face authentication. Zero false accepts in 5,000 trials. 14-month battery life with 20 access events per day.