Computer Power - "Modified Sine" Through UPS

 Hi Everybody,

Please feel free to correct me on anything...

My understanding is that low-cost inverters (12v-to-mains-
voltage) usually put out AC with a "Modified Sine" wave (which
could, more honestly be called, a "Modified Square" wave.)

And, apparantly, that AC tends to cause lots of problems trying
to run computers.

I am curious:

I have my laptop computer with its external power transformer
(220v AC going to 14v DC) plugged into an APC-Brand UPS.

If I get a cheap "Modified Sine" wave inverter to run from a 12v
battery source, will the UPS unit smooth out the 220 supply to
properly function with the computer?

Thanks in advance for all of your advice...

--
Guide To DIY Living
http://www.self-reliance.co.nz
(Work in progress)

  I run my laptop and a HP deskjet printer off a 175 watt inverter without any
problems.

Just my personal experience though, no real knowledge to back it up.

Toby

 On Mon, 29 Dec 2003 16:30:09 -0800, Down Under On The Bucket Farm


Modified sine if you're selling, modified square if you're buying. :-)


No, it doesn't. It causes problems on some very specific equipment
such as laser printers and some Macs but it's rare.


Your laptop undoubtedly has a switch-mode power supply (far more
complex than a transformer, though you're probably using the term
generically) and it will likely be just as happy as a clam with
modified whatever wave power.

Is the UPS a true sine wave model? Is it full-time or stand-by? The
average stand-by UPS is little more than a crudely filtered power bar
until the line fails. If it is the typical modified square wave
stand-by device, you can find out exactly how your laptop will run
from mod sq wv power simply by unplugging the input to the UPS.

I live in a house that uses modified square wave power exclusively and
I have run a full-time laptop-based office, with inkjet printer,
scanner and external disk drives without incident for more than three
years.

In fact while doing some system upgrades I ran my little laptop office
off a Statpower 125W mod square wave inverter for three months.

Aside from two Dell laptops, from time to time I've also run a Mac
Powerbook, an IBM laptop, and I recently bought a museum piece to run
some old hardware and software - a desktop 386 PC with a CRT monitor.

All's been just swell. Eventually I will upgrade to sine power, but
computers will not be the inspiration for the move.


Unless it is a full-time sinewave UPS you'd be wasting your time.
However, chances are around 99% that your fears are unwarranted in any
case, so the issue of the UPS becomes academic.

If the laptop is the only thing you want to run from a battery, you
might consider buying a 12V power supply for your laptop, e.g. from
Lind Electronics, but the cheapest, most readily available and
flexible solution will be a low-power inverter.

-=s

 

A switch mode power supply used by virtually all computers (and now most
monitors) these days tend to like square waves just as much as sine waves.
It's one of the many benefits of a switch mode power supply. After all a
switch mode power supply converts and filters the incoming voltage to a high
voltage DC source.

 wrote:


I didn't say it well enough the first time? :-)

-=s