[ale] [way OT]: Workbench power supply?

[James P. Kinney III]

I'm missing bits and pieces of this thread, but here goes:

If your dashpc only needs 70 Watts, then all you need is an 80W power
supply to give yourself some head room. 75 Amps at 12 Volts is a 900
Watt power supply. A clean computer system stable 500W power supply is
around $400. 

Yes, it is possible to put multiple power supplies in parallel to up the
amperage output while keeping the voltage the same. That said, you will
need some big, honking diodes ($$$$$) to prevent "backflow" upstream of
the common point for every power supply. It is essentially not
practical.

The car battery is a good idea. Get a car battery charger and put it on
the battery during your testing. It will keep it charged up.

A car battery is rated to deliver around 600 Amps at 12V. But it can
only do that for about 1-2 minutes then it's dead. With your 70W need,
the battery will last about 100 minutes (depends on temperature and
"rest times"). You probably don't want to have the charger running on
the battery during testing as they do not have much AC filtering and
will tend to scramble delicate DC circuits like those found in CPU's. 

As was stated by Jeff, the relevant math is:
V=IR
W=IV

The missing math is:
$=W^(I+V)   :)

On Thu, 2003-05-01 at 22:38, Christopher Bergeron wrote:
> Any guesses on how long "a while" is?  I really don't want to be 
> swapping car batteries out daily, weekly, or even monthly (for that 
> matter).  I'd like to find a way to do this by using either an 
> affordable power supply, or a "combination" of computer power supplies.
> 
> Jeff H actually gave me some good advice tonight.  Am I right in 
> thinking that if I try to draw more current from a supply than it can 
> handle, the power supply will be the only casualty?  I'm asking this 
> because I have MANY PC power supplies that can give out 10A at 12V.  I 
> can burn through power supplies without tears; however, if I lose my 
> mainboard or my DC-DC supply, I may shed a few.
> 
> Any further tips Jeff, et al?
> -CB
> 
> 
> 
> 
> Alexander Barton wrote:
> 
> > Christopher Bergeron wrote:
> >
> >>  From what I can gather with my limited knowledge, I think I'd like 
> >> to have a 12-14V power supply, that can handle however many AMPS are 
> >> equivalent to my 70 watt DC power supply.
> >
> >
> > 70 Watts divided by 12 Volts is 5.83 Amps.
> >
> >> Does anyone have a recommendation of a power supply that I could use 
> >> to affordably duplicate a vehicle power subsystem?
> >
> >
> > Instead of a power supply, you might want to get another car battery. 
> > At a draw of 6 Amps, the battery should last a while.  Then, swap it 
> > with the one in your car to recharge.
> >
> > You also have a hot spare in case you leave you car lights on one 
> > day.  :-)
> >
> > -Alexander
> >
> > _______________________________________________
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> > Ale at ale.org
> > http://www.ale.org/mailman/listinfo/ale
> >
> >
> 
> 
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-- 
James P. Kinney III          \Changing the mobile computing world/
CEO & Director of Engineering \          one Linux user         /
Local Net Solutions,LLC        \           at a time.          /
770-493-8244                    \.___________________________./
http://www.localnetsolutions.com

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics) <jkinney at localnetsolutions.com>
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