I want to have some equipment connected to a UPS to shut down gracefully when mains is cut. This equipment does not have capability to read serial or USB, so software solutions are out. What I'm looking for is a hardware solution: a digital output which shows high or low depending on whether the UPS is on battery or mains.
I looked at some APC and other brand models, and all seem to use USB and/or RS-232 to communicate this information. I'm looking for something simple, just a single pin on the back that changes voltage when on battery, or perhaps two pins that get shorted together.
Does anyone know whether such features exist on available UPS models, or is it all software these days?
With APC UPS models this is achieved using dry contact I/O cards. This is an expansion card which provides digital inputs and outputs to control the UPS's state, and read back whether it is using its battery or the mains.