From ESP32 Weather Station to Home Security Monitor with HC-SR501 PIR Sensor

A few months ago I cobbled together a simple ESP32 weather station that dutifully reported temperature and humidity to my Home Assistant dashboard. It worked great until my cat decided the breadboard was a better bed than the couch. While the weather station slowly transitioned into a fur-covered sensor graveyard, I needed something else to do with the spare ESP32 Development Board Module I had lying around. That’s when the idea hit me: why not repurpose the same hardware I used for a weather station into a dead‑simple motion alert system?