dumb question volts/amps - how much is too much?

I've a wall wart which is rated 12 V DC at 1 amp output
The router is (I think) expecting 12 VCD at .5 amp.
And I correct in assuming that the wall wart will not "over supply"
the device - that its rating is essentially the max amperage it will output, while the router is the amount it will draw to function?
That seems to make sense, to me. At this hour of the morning.
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pyotr filipivich.
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Typically, a device "pulls" what it needs for a lack of a better way of describing it. For instance, a battery capable of powering the space shuttle at 12V could also start my motorcycle, but not the other way around.
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-0400 typed in rec.crafts.metalworking the following:

    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.
    Thanks.
    Now to see if I let the magic smoke out. (I've been told by Electrical Engineers, that electrical items run on smoke, and letting the smoke out is what causes them to fail.)
tschus pyotr
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pyotr filipivich
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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
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message

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.
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That's because they are almost always with Underwriters Labs as being a "current limiting device" and as such they are actually designed to fry in an overcurrent situation--and the main reason they are so prevalent these days is exactly because this...IE, in many situations it allows manufacturers to circumvent agency certification so long as the device is sold along with a "listed power supply"....essentially making it faster, easier and less costly for manufacturers to bring new electronic items to the marketplace..
That said, beware of "counterfiet UL stickers", items imported from Communist China being notorious for this particular consumer fraud.
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Boy, Ed, you sure are easily entertained.
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?
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.
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I used to tear the wings off of flies, until I discovered RCM.

It would be fun to watch. d8-)

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On Tue, 26 Apr 2011 15:17:33 -0400, "Ed Huntress"

No motor in a router - not in the computer type anyway - and a 12 volt 1/2 amp Motor type router is only 6 watts, or roughly 1/100 hp.
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Ed Huntress wrote:

Letting the magic smpke out causes the house to smell bad!
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Richard Lamb
http://www.home.earthlink.net/~cavelamb
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Not as bad as the piece of Tupperware my wife "cooked" in the electric oven last night... :(
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Joe Agro, Jr.
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Gunner Asch wrote:

One of the things I worked on when in the USAF was a jamming transmitter with a separate power supply. The power supply was pressurized, to maintain breakdown voltage so that it didn't arc over internally. One day, we got one of the pressurized power supplies in the shop that had blown its selenium rectifiers. Hoo Boy! It cleared the whole building for the rest of the day!
Cheers! Rich
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That is a sharp smelling when those blow. I did it at home building a home made tube radio. Vacated the living room - Selenium is poison.
Martin
On 4/27/2011 3:36 PM, Rich Grise wrote:

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    [ ... ]

    [ ... ]

    [ ... ]
    And here I thought that I was the only one left who knew what a fried selenium rectifier smelled like. :-)
    Enjoy,         DoN.
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Yea when this young one bolted the stack to the metal chassis - grounding the supply through the stack to ground I did. That taught me about insulators and standoffs made in porcelain. Martin
On 4/27/2011 11:43 PM, DoN. Nichols wrote:

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sounds like - OOPS!
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"DoN. Nichols" wrote:

You never watched the original 'Mission Impossible' TV series?
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    [ ... ]

    No -- that was during a period when I lived alone in an apartment with no need for a TV. :-) (I *did* read a lot of science fiction, though. :-)
    Enjoy,         DoN.
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In one episode their 'equipment' has a Selenium rectifier start to fail, which would have shut down their operation, so their nerd solders a new one across the failing unit with the power on. Then he leaves the supposedly bad rectifier in the circuit.
I am in the middle of sorting my Sci-Fi collection right now. The $40 I paid for a new barcode scanner was money well spent. So far, I have inventoried over 600 books and put each in a zip lock bag.
The inventory will be posted here when I finish it: http://home.earthlink.net/~michaelaterrell /
I have found that I have a lot of duplicate books, that I want to trade for books I don't have.
I am going to have to find another way to post & read, if Earthlink doesn't fix their problems with Giganews log in. I had downloaded a bunch of headers and was reading the messages when it crapped out, this time. :(
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Gunner Asch wrote:

Got F&SF? I can't buy them this week (or maybe for about a month - are you in a hurry?)
I'd kill to get my hands on a collection of The Good Doctor's essays.
I might even be able to arrange for a pickup, depending on how far from Whittier they are.
And I don't remember which one it was, either Analog or Galaxy or that other SF pulp, where there was a very notable article, "Cap the Volcanoes!", from the 1960's or so. It soundly debunked the global warming hoax.
And another article I'd virtually kill for was something like "Build an Atomic Bomb and Wake Up the Neighborhood."
Thanks, Rich
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