Automation, sensing and robotics • Re: Automatic shutdown and restart after power outage using NUT

If the UPS can restore power when the mains supply is stable then the Pi can power itself back on.

There are a few notes on this post https://forums.raspberrypi.com/viewtopic.php?t=361443 about starting a Pi from cold.

Normally a SIMPLE UPS sequence would something along this sequence:

• Everything running normally
• Power fails
• UPS goes onto battery and notifies client devices it's on battery
• Devices wait for 'x-minutes' for mains power to be restored
• If mains power not restored clients shut down
• UPS reaches a low battery point (NOT flat as that kills batteries quickly) and shuts itself down into a standby mode
• Mains power restored (or a standby generator kicks in)
• UPS powers back on and checks if the mains supply is stable (and starts charging its batteries)
• Once the mains supply is stable the UPS powers its output supply
• Some send a power restored message - could be handy if low power devices remain on*
• Client devices power themselves back on

Commercially it can get way more complex than this (esp phasing of devices coming back) but this should give you a basic idea.

* Pi boards are handy - I think I could get a good couple of moths supply to a Pi from a rack mount unit I used to have and maybe a year or two from the old mini computer supply from years ago.

Note - not all UPS systems will shut down after a delay or re-power on but any reasonably decent one should

Statistics: Posted by MiscBits — Thu Jun 13, 2024 10:14 pm

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