Comment by gary_0
10 days ago
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.
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.
I would absolutely not want to use a microcontroller or a complicated chip for something like that. Simplicity is the point.
Supervisor chips are not complicated. In some ways simpler than a homebrew analog watchdog, and the good ones will handle failure modes a simple watchdog won't, like those that result in an oscillating output.
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Modern 32-bit microcontrollers are cheaper than 555s.
Yes, but uses software, so you have another level of added complexity that may be or may be not desirable.
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There's the guy who's never shipped and supported a product.
Not if you go to the cheap "Asian brands" like you're thinking with micros, plus with your cheap micro you'll need a reset controller. And budget isn't all BOM cost.
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