UPS recommendations?

[Mark J Elkins]

In article <3260 at anomaly.sbs.com> mpd at anomaly.sbs.com (Michael P. Deignan) writes:
>mark at intek01.uucp (Mark McWiggins) writes:
>
>>I need a UPS that can do auto-shutdown of my 386 Unix system in the
>>event of a power failure.

The simplist I ever saw was...

Plug a neon into the normal mains (with appropiate ballast resistor).
Have an 'LDR' next to it (Light dependant resistor).  connect the ends
of the LDR to pins 2 and 3 of an available RS232 port.  Put neon and
LDR together (close) in a light-proof box (match-box size?).

On computer - send char every 1 minute to rs232 port.  If you can read
a reply (what you just sent), mains power still on.

If you send a char - and nothing comes back - assume power is off and
that you are running on the UPS.  Schedual a shutdown!

You can use status files and guesswork as to how much juice is in the
batteries - and schedual the shutdown accordingly.

Costs - Most expensive part is the DB25 (assuming you have a 'spare'
rs232 port :-).  OK - so this ties up a port - and there are some
detail missing like crossing pins 4+5+8 and 6+20, writing a prog to
read/write the port...  but once you have the 'idea'....

If you are careful - the LDR/Neon can fit into a DB-9 connector.  It
looks quite amusing plugging the RS232 port into the mains!
-- 
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