I plan on purchasing an uninterruptible power supply for a project that I'm in the middle of, but I realized that I'd love to have some way of notifying me when the UPS kicks on/off! I'm not sure if there exists a way to pull that kind of signal directly from the UPS, but I'd assume it would be possible since many UPS units have small displays with indicators that they're currently active.
I'd be using this signal to throw up a simple indicator on a screen of my own through the Arduino + RPi, as well as sending an email or something of that nature. If anyone has any ideas or solutions, I'd love to hear them! Thanks!
I would investigate the BEEPER that sounds when the UPS takes over. Consider it will also identify a power failure when there is even a 1 cycle missing, so you may get more than you bargained for!
Most will have a dry relay closure or a powerfail signal that comes in as a serial interrupt on the DTR line on the serial or USB port.
Read the manual before buying. Many come with monitoring software that can trigger a SCRAM save. Even if you don't use pc software on the Arduino, the manual will explain the connection method and process.
It all depends which UPS you buy, some have integrated messaging capability via the network.
or you could possibly use the led that comes on when the ups kicks in as a trigger source (making sure it doesn't blow your Arduino of course)