After leaving the freezer door open all evening twice in hot weather in previous years I started working on a fridge/freezer door alarm to warn me if this happens again. My model of fridge/freezer happens to have convenient anchor points for this:
Using an ESP32-C6 I've made the "Eightfold Seal" device that supports two doors and a buzzer alarm with increasing frequency when the door is left open. It communicates using Zigbee allowing remote configuration and status information, as well as the possibility to cancel the current alarm if the door is intentionally left open.
![[Home Assistant list of controls for the Eightfold Seal device: cancel/enable switches for the alarm and configuration of timing for the two alarm stages]](/assets/2025/05/11/hass_eightfold_seal_controls.png)
![[Home Assistant list of sensors for the Eightfold Seal device: current alarm and door open/closed state as well as uptime and Zigbee uplink information]](/assets/2025/05/11/hass_eightfold_seal_sensors.png)
When either door is open even slightly, this is detected and the buzzer will sound after a delay. Here are some videos with the buzzer configured for no delay to demonstrate the sensitivity:
I had to print a custom lower profile insert for the freezer door because there's a mat nearby and very little clearance below the door because of that:
