The essential operation of the system is to produce a trip signal once a door is opened. Thus, killing any ongoing operations within a room.
The system consists of a door sensor, Raspberry Pi, WiFi Router, and Shelly 1 Relay.
Each door sensor is built using a Heltec wifi kit 2 ESP32, 1000 mAh LiPO, one reed switch, a few small magnets, and a custom, 3D printed, housing. The housing is assembled with threaded brass inserts and appropriately sized cap screws.
The Raspberry Pi, while connected to the WiFi Router via Ethernet cable, handles all communications. Commands passed to, and from, the door sensor or Shelly 1 Relay is done using MQTT via Eclipse Mosquitto. Furthermore, manual control or system reset is performed via a website that is hosted on the Raspberry Pi. The website is built using Node Red and the Node Red dashboard plugin.
The Shelly 1 Relay simply has developer mode enabled for use with MQTT and all commands are passed in accordance with the Shelly REST API.