I use this watchdog to keep my chicken barn controller from hanging up. Every 10 seconds my barn controller sends an MQTT message to my Home Assistant Pi. HA has an automation that is triggered by this MQTT message and sends out its own MQTT message back to the barn controller. This signals the barn controller which toggles the watchdog heartbeat pin and the watchdog timer is prevented from timing out. If any part of this sequence fails the watchdog will power down the barn controller for 10 seconds before powering it back up. This really helps if the wi-fi drops out, my code crashes, or my HA is rebooting.

The first version of this device hijacked the incoming power from a 12V adaptor. The second version was designed as a daughter board for my barn controller.

The circuit was designed and built with parts I had on hand. It feels like it has more parts than it needs. If someone knows how to improve it without sacrificing features, please let me know.