Author Options:

How can I build a siren when my UPS detects a power cut? Answered

Alright, I have a large server set-up in my closet, and just recently I had a power cut, which, if not for my backups, I would have lost everything (photos, videos, documents, my soul etc.)

The problem was it was in the middle of the night, and the UPS (for some reason) didn't shut down the server when the battery drained. So I want to design a system where if the UPS is tripped, some sort of siren or flashing light goes off, so if I'm asleep, I can get up and safely power down everything.

Any ideas?


I had to replace the batteries in my UPS's. I now use 4 12 volt deep cycle marine batteries. With proper care these batteries can last a long time. Of course now my UPS footprint has doubled.

That's some bad setup if the system loses everything because of a power outage. In all the years I've run servers, none of mine have ever lost hard disk data when we've had power outages.

If it's that important, but a new ups that has the alarm and WILL shut down your system right. Then use the old ups for something else. But if you just gotta build one. But y a 12 volt relay. Power that relay by a 12 volt wall wart plugged into the same outlet as the UPS but not thru the ups. Not, plug another 12 volt wall wart into the outlet of the ups run it thru the relay contacts so that when the relay closes without power it closes the circuit to the alarm. That way when there is power the alarm is off since the relay is pulled open. When you loose power the relay relaxed and closes the switch so the ups can power the alarm and wake you up.