[ale] APC UPS

Mike Panetta ahuitzot at mindspring.com
Thu May 8 14:33:55 EDT 2003


Heck, you can even run a PC powersupply off DC if the voltage is high enough.  It just rectifies the AC and filters it with some caps in the PSU anyway.  I even took a small 5V 5A switcher brick (the autosensing kind, 47->63HZ 100-240V) thats used to power WAP's (we have tones of em here at the office) and with a slight modification I could get it to run off 48V DC in.  With a little bit more mod I got it to run off 12->16V DC in (had to start it at 16V then bring it down to 12V because of the undervoltage lockout on the switching controller).  Switching powersupplies specificly the flyback kind used in PC power supplies are very forgiving of input voltage variations (or can be made to be).

Of course, when I was powering it at 12V in, I could get nowhere near the rated 5A out of the powersupply (watts in must be greater then or equal to watts out, and the input side of the PSU could never handle 2A continuous I am sure, there were other reasons it would not work, but I do not think anyone wants me to go into switching PSU theory...) but it was an intresting and informative experiment none the less :).

Very cool stuff.  If you like to play with electronics and you know how to read schematics well, and know where to get the data sheets on the chips used in the powersupplies, you can do all sorts of things with them :)

Mike

-------Original Message-------
From: Josh Freeman <josh at catea.org>
To: ale at ale.org
Sent: 05/08/03 01:17 PM
To: ale at ale.org
Subject: Re: [ale] APC UPS

> 
> On Thu, 2003-05-08 at 12:59, hbbs at attbi.com wrote:
> Did anyone find out if that generator was DC?  Reason I ask is that once
> undriven, a flywheel naturally can't stay at the same speed and
therefore can't
> run an AC generator so as to make it continue to put out 60Hz.

Depending on the mass of the flywheel, I'd be willing to bet it could
run in the 50-60 Hz range for quite a long time. Many power supplies can
operate down as low as 50 Hz without too much damage. In any case, I
would imagine that the 15% drop in voltage would be as much of an issue
as the lower frequency.

Josh


-- 
Josh Freeman
Technical Manager
Center for Assistive Technology and Environmental Access

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