The hassle of walking to your mailbox to check mail has prompted many hackers to install automated systems that can let them know when mail has been delivered. Mailbox monitors are built based on a variety of methods: some measure the weight of items inside, some use a camera and machine view, others simply trigger whenever a mailbox door or flap is moved. When [Gary Watts] Wanting to install a notification system for his 1940s brick letterbox, his options were limited: to monitor any flaps or doors, and without limited space to install mechanical contraption, he decided to use a LIDAR sensor instead.
Probably best known for their emerging application in self-driving vehicles, the LIDAR system sends a laser pulse and it takes time to be reflected from a surface. About this [Gary]Its mailbox, that surface is either a brick wall or a letter leaning towards it. Since the letters are inserted through a vertical slot, they will usually be tilted straight along the wall, providing a clear target for the laser.
The LIDAR module, a VL53L0X made by ST, is paired with a Wemos D1 Mini Pro. Communicates with D1 [Gary]Its home WiFi is charged via an external antenna, and a solar panel powered by an 18650 lithium battery. The entire system is housed inside a waterproof plastic case, with the LIDAR sensor attached to the inside of the mailbox via a 3D-printed mounting bracket. On the software side, Mailbox Notifier is powered by Home Assistant and MQTT. The D1 spends most of its time in deep-sleep mode, only waking up every 25 seconds to read the sensor and send a notification if needed.
We’ve seen a number of fancy mailbox monitors over the years: some are extremely powerful, some use multiple sensors to allow for different uses, and some are simply beautifully designed.