"rangerssuck" wrote in message
...
On Apr 26, 3:17 pm, "Ed Huntress" wrote:
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in
messagenews:Xns9ED399F9754E7lloydspmindspringcom@2 16.168.3.70...





pyotr filipivich fired this volley in
:

Ah, so "one way of thinking about it"is that - yes, the wall wart
can supply up to 1 amp at 12 VDC, but the router is only going to use
half an Amp.

But the other way of thinking about it is that some Wal Warts are not
regulated. If not, and you do not draw something near to their ratings,
they may damage the powered equipment by supplying too high a voltage.

The little lightweight switching supplies are almost always regulated,
but the heavier transformer-based units are often just a transformer,
bridge rectifier, and filter capacitor; Their outputs can vary 50% from
the rating at full load.

LLoyd

It's instructive to see what happens to a wall-wart when you abuse it. If
you short the output of one, most of them will fry themselves in an
instant
from the current overload.

I've done that for entertainment when I no longer have use for them. I
have
too many in my junk box as it is. g I have two of them that did not. The
transformers in them must be so pathetically underbuilt that they just
buzzed. Most of them are somewhat self-limiting by virtue of extreme
transformer inefficiency, but most in my limited experience will not
tolerate a direct short.

Regarding the motor, if you supply too much voltage, you probably will get
a
surprise regarding that 1/2 Amp.

--
Ed Huntress-

Boy, Ed, you sure are easily entertained.

I used to tear the wings off of flies, until I discovered RCM.


Many of these things have fusible links under the first layer of tape
in the transformer, others have "polyfuse" type circuit interruptors.
Would you prefer, perhaps, that they supply unlimited current and just
catch fire when you short them?

It would be fun to watch. d8-)


BTW, regarding the original question: Yes, a properly working device
will draw only what current it needs from your 12V supply (assuming
it's putting out something near 12V), but the designers sometimes rely
on the overcurrent protection built into the supply rather than
spending the extra $0.25 to put a fuse in the router. So, if you had a
fault situation in the device and it was connected to a larger than
expected supply, you *could* have a fire. In reality, it's unlikely;
at the currents your talking about (0.5A vs 1.0A) it's virtually
impossible, but I've seen installations which have large numbers of
consumer-grade devices connected to a single large supply, and that
sort of thing could be a problem.