Sunday, November 12, 2017

Paradise ponders: powered by UPS edition...

Paradise ponders: powered by UPS edition...  My “install the UPS” project yesterday went about as well as it could.  There were no major challenges, and no extra trips to Home Depot were required.  The new L5-30R receptacle (at right) is about the only visible part of the project, other than the UPS itself.  As I'd hoped, at the current draw my actual equipment has, the UPS is fairly quiet.  I located it in the storage area of my barn, outside the insulated walls of my office, so from inside the office I can't hear it at all.  I put my 'scope on the power produced by the UPS, and it's a beautiful, noise-free sine wave.  Put my freq counter on it, and it's running at 60.0002 Hz: more than close enough for anything I need!  That's actually probably better than the power company, especially when you take the noise on the main lines into account.

I did run into one disappointing thing.  The “Multilink” software that comes with the UPS is a restricted license with very limited capabilities.  It has an embarrassingly bad user interface, and there's no obvious way for me to write software that can interact with it, or monitor it. This is not what I had been expecting out of a datacenter-class piece of kit.

Multilink communicates with the UPS over a serial port.  That got me to wondering whether the serial protocol was documented.  A little googling and I discovered that (a) no, it's not documented and in fact is explicitly proprietary, and (b) of course some other datacenter operations folks have reverse-engineered it (the same protocol is used on many UPSs, including the monsters used in datacenters).  This fellow made a start on documenting it, and includes some interesting information about how he did it.  Here's another guy who actually wrote a Linux device driver for it!  It looks like it won't be too hard for me to integrate some monitoring for this...

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