[gary_0]

I designed the electronics for a heavy-duty industrial 3D printer and used a 555 in the failsafe circuit (alongside the manual e-stop). If it didn't get reset by a heartbeat from the embedded computer/software, it would unpower the heaters and actuators.

[buescher]

That's the only use for one that isn't (always) a design smell - it makes a really nice missing pulse detector, better than you can easily do with comparators. But if you have the budget, a purpose-made watchdog chip or a tiny microcontroller really can make a better watchdog.

[gary_0]

I would absolutely not want to use a microcontroller or a complicated chip for something like that. Simplicity is the point.

[15155]

Modern 32-bit microcontrollers are cheaper than 555s.