[time-nuts] Power glitch

Hal Murray hmurray at megapathdsl.net
Wed Jun 27 22:48:55 EDT 2012

david-taylor at blueyonder.co.uk said:
> Thanks for that, Hal.  I would set up some monitoring myself except that I
> don't have a UPS so even a 16-second outage would not be recorded.  Could
> use a portable PC, I suppose...  We have perhaps one outage every two years
> on average, and they last for at least 30 minutes, so I might need a
> generator as well as a UPS!  Not worth it - I don't mind being dragged away
> from the desk for a while - might catch up with read a magazine or two.

An old laptop is clearly an interesting solution that is easy to understand.  
The older ones still had real serial ports.  At least some of them did.  
Maybe it's on the expander thingie with CD drive and various connectors.


Several years ago, I got a recycled APC-750.  It has a serial port that will 
tell you the line voltage and the min line voltage since the last time you 

There are 2 main parameters for a UPS.  One is how much power they can put 
out.  The other is battery size.

The only thing I have plugged into it is a small "embedded" type PC.  It 
draws about 20 watts.  The APC-750 is way overkill for running a tiny PC.  I 
got it because it had a big battery and bigger ones were more than I was 
willing to pay at the time.  I think it was roughly $100 plus another $50 for 

I'm not sure how long that combination will last.  I guess I should try an 
experiment some time.

Fine print:

I've seen a comment about the power rating on small UPSes taking advantage of 
the size of the small battery.  There is enough thermal mass to be 
significant.  The temperature is still ramping up when the battery runs out.

For light loads, the idle power might be significant.  I guess this calls for 
another experiment.

These are my opinions.  I hate spam.

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