On 2/9/10 7:00 AM, John Carmonne wrote:
On Feb 9, 2010, at 6:16 AM, Bruce Johnson wrote:
On Feb 8, 2010, at 8:53 PM, JOHN CARMONNE wrote:
Hi All I want to buy a 5v power adapter that I can use on most of
my stuff ilke external FW USB drives and Pc cards cards and such.
I want to get some that work across the board, Is there something
like this I can get? John Carmonne Yorba Linda USA
It depends on the specific power needs and the tip style. RatShack
and WallyWorld sell multi-tip, multi-voltage adapters, just be
aware that you can use higher amperage than the original, but it's
dicey using lower amperage, and the multi adapters I've seen have
been like 900 milliamps, and I've seen drive adapters as high as
two amps.
OK so do you trust the multi votage, multi tip ones? And I assume you
would buy the highest amp out put? Do the devices adjust to the
increased amperage?
A device connected to a power supply only draws as much current as it
needs. Amperage is a capacity rating, as in it will supply UP TO that
amount.
In general you can go with a higher current rating but don't go too much
higher, probably no more than 50% higher. Most wall warts are
unregulated. An unregulated supply puts out a higher than specified
voltage under a light load. I've seen power supplies that were rated at
12V put out 18V under no load. The rated voltage is (more or less)
achieved at the specified current load. If you use a supply with a much
higher current rating the voltage will likely never drop to near the
rated amount.
Now in some cases this doesn't matter but you never know ahead of time
if it does or doesn't.
That said, 5V supplies are a different beast. These usually are
regulated, the output stays at 5V (or close enough) from 0A to the
maximum rated current. A lot of digital electronics is unforgiving of
changes in supply voltage so they use a regulated supply. In most cases
the regulation is in the equipment not the wall wart. But 5V regulated
wall warts are becoming more common. So if your device needs a 5V
regulated supply make sure that is what you use. Multi-voltage wall
warts may be regulated but I wouldn't count on it. And if they are
regulated I don't have much faith in how well regulated they are. This
is due to a specific technical feature of them, they are C.H.E.A.P.
There is also equipment out there that requires a 3.3V regulated supply.
--
Clark Martin
Redwood City, CA, USA
Macintosh / Internet Consulting
"I'm a designated driver on the Information Super Highway"
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