Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!tmsoft!mason
From: mason@tmsoft.UUCP
Newsgroups: sci.electronics
Subject: UPS's that aren't
Message-ID: <161@tmsoft.UUCP>
Date: Fri, 7-Aug-87 20:49:46 EDT
Article-I.D.: tmsoft.161
Posted: Fri Aug  7 20:49:46 1987
Date-Received: Sun, 9-Aug-87 10:26:09 EDT
Reply-To: mason@tmsoft.UUCP (Dave Mason)
Followup-To: sci.electronics
Organization: TM Software Associates, Toronto
Lines: 33

Sorry if this gets discussed every week here, but I don't usually read the
newsgroup.  I will read it for a while in case this is an interesting topic
for you EEs, and you want to post replies.  If it's a boring topic, please
reply by mail.  I'll summarize if asked.

I was going away on 3 weeks vacation & wanted tmsoft to stay running & receiving
news & mail.  So, I thought, I'll just go out & buy an Uninterruptible Power
System.  So I did: a Sendon UPS-400W (400 watts, 5 millisecond max switchover).

Problem: the wave-form that comes out is positively ugly, and while switching
power supplies don't seem to care, tmsoft has a linear supply.  It will run on
the battery and when the power comes back, it seems to switch OK; but when the
power goes away power drops long enough to be a problem (i.e. system crash 1/2
way through vacation)

I've seen switchers work (although they were probably pulling less current)
fine with it.

The wave form looks like a bad cross between a sin wave & a square wave,
switching between the two about the top of the crest & bottom of the trough.
There are also some ugly transients when it's switching between mains power and
the battery.  I added a Radio Shack "Voltage Spike Protector with Broadband
Noise Filter" to the output with no discernable difference.

What I would like is something I can add on after the UPS that will clean
things up so the power supply works and I get rid of the nasty transients
(which mess up a terminal I use).  (My electrical theory is pretty shaky, but
it seems to me a huge 60 Hz pass filter would do the trick).  (I can also add
some more capacitance to my power supply, but I'm a little concerned about
inrush current).
	Thanks
	../Dave Mason,	TM Software Associates	(Compilers & System Consulting)
	..!{utzoo seismo!mnetor utcsri utgpu lsuc}!tmsoft!mason