12 May
2006
12 May
'06
1:08 p.m.
On Friday 12 May 2006 03:07 pm, Roger Merchberger wrote:
I need some help from those who are a lot better than
I in hardware
design...
The problem is I need to use a PC power supply (AT-class with it's own
power switch) as a 12V power source, and the only one I have access to
needs a minimum load of 3Amp on the +5Volt line.
By my rough calculations and allowing for wiggle room, I'd need a 20-watt
power resistor of 1.5 ohms to keep the critter happy. "Bare minimum" is
15W, and I could squeak by with that if I wire the fan to the 5V line
instead of the 12V... but even when I'm expected to perform a "miracle" I
like to have a little wiggle-room. ;-)
Problems I have are: 1) I need this by Monday, and 2) I don't keep 20-watt
power resistors in my back pocket. Had I a week, I'd just order the right
tool for the job - I don't have that luxury. ;-)
I remember reading somewhere that taking one or several 12V light bulbs of the
automotive persuation and running them off the +5 supply would often work in
this situation. Got a junkyard nearby? :-)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
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Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin