TELECOM Digest OnLine - Sorted: Re: Monitor/Recorder for Residential Power Line Outages?

Re: Monitor/Recorder for Residential Power Line Outages?

Robert Bonomi (
Sat, 18 Jun 2005 04:15:58 -0000

In article <>, AES
<> wrote:

> Any have pointers to a gadget that will monitor and log power outages
> or glitches on 110V or 220V residential electrical service?

> Looking for a home or retail level gadget that will work either
> connected to a dedicated computer, or preferably free-standing with
> periodic read-out to a computer, logging time and duration of both
> longer outages and short glitches (anything long enough to cause
> digital clocks and appliance displays to reset).

> Asking on this group because a lot of tech-savvy people seem to hang
> out on this group; glad to accept pointers to any other group.

> Any way to make the computer itself (e.g., Mac iBook) do the sensing
> and recording?

It should be obvious that any such device will need to be powered by
some sort of UPS. Whereupon you may as well use a UPS. <grin>

Most modern "smart" UPS systems have a capability for signalling a
host computer about the state of the incoming power, and the state of
the UPS batteries. Allowing, among other things, 'controlled'
shutdown of a UPS-protected device when the UPS batteries are about to

However, if you have a 'dumb' UPS, it is trivially easy to create a
sensor that can be monitored by a computer serial port. A simple
120VAC relay does the job. Wire it so that when power goes *off*, the
a "modem control" signal is asserted that indicates the serial port is
"usable". When the power is on, and you try to "open" that port for
use, the operation will wait for the right modem-control signal. The
power goes off, the signal appears, and 'whatever it is' your software
does after the 'open' on the port succeeds will happen. Like logging
the fact that the power went off. When power returns, that signal
will be dropped, and you'll get a status-change on that successfully
opened port. Voila! You can log that power returned.

*IF* the computer loses power, _and_ is set to automatically restart
when power returns, then you simply log the "power returned" when the
machine boots up.

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