Add a Watchdog Timer to Your Microcontroller
Although most modern microcontrollers have an internal watchdog timer, that may not be safe enough for the system to rely on it. The built-in watchdog timer can reset the MCU but it cannot perform a power cycle. An external watchdog controlling the MCU’s power supply may be a better solution in some cases. There are dedicated ICs for that, but you can also make one yourself based on a 555 timer IC.