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Re: Can a power supply have too much current?
Michael J. Mahon wrote:
> 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.
Did I really get that backwards? That's worrying.
>
>>>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...
I like linear regulators. They have their uses anyway. As long as input and
output aren't reversed on the variable voltage regulator. Strange and
frightening things happen then.
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