Hi, I just acquired a 'broken' UPS. All it needed was a new 12V 12Ah SLA battery- $40 from Sydenham. Oh, and a cable...
I have found from trawling the web that this UPS shorts pins 8&9 for "AC fail" and 1&7 for "Low battery" on its DB9 connector. I haven't found any more information, and it looks like that is the extent of its capabilities. Some UPS units have a pin that will shut down the UPS, and some have actual serial communications back and forth so that the UPS can indicate its status and accept commands via a serial protocol. Anyway, this email is partly an enquiry and partly documentation on what I have done. I made a cable: PC DB9F DB9M UPS DCD 1 <------- 1 \ Short on DTR 4 -------> 7 / Low Batt. CTS 8 <------- 8 \ Short on RTS 7 -------> 9 / AC Fail There are other web references which include resistors to pull the lines high or low, but I didn't see the need. In this particular case the UPS has relay switches, so they have no polarity. Any inputs not connected on the serial port have built-in pull-ups (or pull-downs) to assert the idle condition, so there's no need to include them in the cable. As you can see, if DTR and RTS are both asserted (by the UPS daemon), then when the relay switches close then DCD and CTS will be asserted, so the daemon can detect it. I tried installing 'upsd', and got it going on the laptop, but I think I will install 'nut' on the server (which is the intended destination). Anyone else got anything to add to this? Better techniques? More information on this specific UPS? Top tips for configuring a Debian server with nut? Thanks, and Season's Greetings, Andy
