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Re: Can a power supply have too much current?
Tristan Mumford wrote:
"Henry" <apl2research(.a.t.)comcast.net> wrote:
Hey Guys.
I have a couple of IIGSs from different places. My problem is also
the voltage with regards to those that came from the US. I have
previously managed to cut a board in half from an AT power supply and
fit it into a //e (still looking stock). I think it won't be too much
trouble to do the same for a IIGS, if I could find another AT power
supply (they're becoming rare nowadays... everything's now ATX).
[SHAMELESS PLUG ALERT!]
One of our IIe or IIgs 200w Power Supplys would also do the trick and it
does work with any international power source. Link:
http://www.gse-reactive.com/product_info.php?products_id=55
As far as 'too much' current, it really can't hurt anything but too much
or
not enough voltage can. Just think of a car battery. Yours might be 500
Amps but the car never uses more then it needs when you start it. Really
it more determines the amount of time it can turn the engine over before
it's
drained and needs to be recharged. A 500 Amp battery will last longer
trying to start a car then a 200 Amp battery.
And a shorted 500A battery will make a fire *much* faster than a
200A battery. ;-)
What happens in case of a short is the issue. A power supply designed
to supply 2x-3x the maximum normal requirement will current limit at a
point that may be useful for protection, while a 20x-30x supply will
turn into an arc welder. Vaporized chips and board traces and burned
boards are much more likely with an oversized supply.
A 5A fuse could help a great deal, but its resistance adds to the
impedance of the supply, which can hurt regulation. The best way to
deal with this is to have a supply with remote sensing, and sense the
voltage for regulation at the point of load, after the fuse.
Well that's true. It's just there's something relating to hydraulics that
worries me. I know it'd different, but I just keep thinking too much
pressure = burst pipes.
In the hydraulic analog to electricity, pressure corresponds to voltage
and flow rate corresponds to current. Burst pipes correspond to
insulation breakdown.
Now for something really 'fun' you could use any power supply, say 15
volts,
and some Voltage Regulators to achieve the voltage you require. They now
make some REALLY small 80w Power Supplys that would do just fine and are
smaller then a box of matches. Fun little project!
Linear voltage regulators dissipate power equal to deltaV * current, so
that could be the hot way to get a lower voltage...
-michael
NadaNet networking for Apple II computers!
Home page: http://members.aol.com/MJMahon/
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