[HomeBrew] Smoothing a square wave

[n1khb at aol.com]

Inverters and the equipment that they run don't always get along very 
well. which is why I attempt to buy things like tv's that are 
anticipated to run in such situations already equipped (designed in) to 
run on 12v dc to begin with. Inverters just aren't going to do it all 
even if they are of the modified sine wave type which are really just a 
variant of a square wave according to the one that I looked at on the 
oscilloscope.

Joe N1KHB



-----Original Message-----
From: Jim Miller <JimMiller at STL-OnLine.Net>
To: Homebrew, Reflector <HomeBrew at mailman.qth.net>
Sent: Thu, 4 May 2006 09:43:31 -0500
Subject: [HomeBrew] Smoothing a square wave

** Please do NOT cross-post messages when posting to HOMEBREW **

I have an inverter that I blame for blowing up a 9 inch color TV that I 
use at
my station and wanted it also to run on 12v as battery backup as my 
station
does.  I scoped the output and it is a two-step (two positive and two 
negative)
square wave output.  I had also  intended to connect my computer to it 
but
haven't tried that because the TV blew up.  Does anyone know what the 
output of
these UPS systems look like?

At 60 Hz, it would take a huge inductor to "round" the corners of the 
wave but I
have a very large pole pig sitting here and wondered if one side could 
be used
simply as an inductor or wire the two sides in series, maybe put a load 
on the
unused side or something.  High side or low side?  How much of a load?  
Use a
cap instead of a load?  OK, dumb idea.

For a small TV only maybe a small LONG "extension" cord wound in a 
small coil
would help smooth the square wave?

1. It says the max current is 1 amp.
2. 20 gauge (too much voltage drop?  I don't have the numbers to 
calculate it.
3. 100-200 feet?  Not long enough to create enough inductance?

Opinions please, I am not a design engineer, just trying to get a small 
TV to
safely run on an inverter or was it coincidence that it quit within 
minutes of
plugging it into the inverter?

Thanks es 73 de Jim KG0KP
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