ESP32-C3 Door/Window Sensor with Battery

Behold, a battery-powered window/door sensor built with an ESP32-C3 SuperMini! Nothing revolutionary, but I couldn't find anything like this on MakerWorld, so here's my take for anyone looking to build their own low-power DIY sensor. How It Works This sensor runs ESPHome firmware on an ESP32-C3 SuperMini board using deep sleep mode to maximize battery life. It stays asleep almost all the time, sipping just a few microamps, and only wakes up when the door or window changes state. When the door/window opens or closes (detected by a simple MC-38 reed switch on GPIO2), the ESP instantly wakes up, quickly connects to WiFi, reports the event to Home Assistant, and goes right back to sleep. One small tradeoff: Due to deep sleep, the sensor takes about 1–3 seconds to report state changes to Home Assistant (time needed to wake, connect to WiFi, and transmit). To squeeze every bit of battery life, I physically removed the red power LED from the board saving a couple more milliamps. Parts You'll