[CentOS] 12V computing?

Sat Apr 12 05:11:47 UTC 2008
jim <jim at well.com>

   a 100 Watt system draws a little less than 1 Amp 
at 120 VAC and about 8 Amps at 12VDC. there's about 
10 times power loss per foot of conductor and per 
connection (estimate 1/2 Ohm per connection). Yes, 
heavier guage wire is required for a lower voltage 
supplying the same power. 
   for that reason, systems using 12VDC must require 
very little power. Via's latest motherboards include 
some that draw 20 or 30 Watts and yet have pretty 
good processing capabilities. SATA solid state drives 
and USB pendrives draw very little power. there are 
systems advertised drawing less than 10 Watts (e.g. 
gumstix). the XO laptop (OLPC) is a good example of a 
fairly powerful computer that requires very little 
   efficient software design--good algorithms and 
small memory footprint--improve benchmark performance 
at the feature level. software that must comply with 
legacy requirements is at a disadvantage in such 
systems. and such systems look to be increasingly 
needed, given the increasing green requirements world 
wide, not to mention the spotty power availability of 
many of the world's remote regions. 
   i believe manufacturers will be delivering systems 
that require less and less power in the near future, 
and more and more of them will be battery powered, 
not only at 12VDC but with AA and C cell batteries 
(e.g. cellphones and PIM devices). 
   as 12VDC is ubiquitous, we should see more and more 
systems designed to work off a cigarette lighter. 
they exist today. 

On Fri, 2008-04-11 at 21:28 -0700, John R Pierce wrote:
> jim wrote:
> > 12VDC is appropriate for places that don't have 
> > other electrical supplies. these places include 
> > automobiles and boats as well as remote regions 
> > that use windmills, creekmills, solar panels, 
> > car batteries, and deep discharge gel batteries, 
> > possibly in a mix. typically there's noise and 
> > variant voltage levels above the nominal 12VDC; 
> > any system should be designed to work with spikes, 
> > noise, and higher voltages--most are as a matter 
> > of course. 
> >   
> and, of course, you need 10 times the amperage at 12V... For instance, a 
> 250 watt system that would draw about 2 amps at 120V will be drawing 20 
> amps at 12V.   this means that you need much heavier gauge power wiring, 
> especially for long runs.
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