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Author Topic: Wall Wart amperage question.  (Read 660 times)
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Florida
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Hello,

I was wondering what would happen if I pulled more amps from a wall wart then it was rated for.

Thanks!
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Dubuque, Iowa, USA
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Depends. If you pull more amps from a wall wart than it's rated for then you should wear Depends.

Could be anything from switching off until replugged-in, blowing a fuse, or creating a fire.
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The latter outcome should not happen if its a genuine UL-certified part (and not a cheap knock-off).  A general
purpose PSU is more likely to be built to take abuse than one designed for a single piece of equipment I suspect.
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Florida
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The fire is what i'm afraid of. It is ul listed. It came from a Router and is rated for 1 amp. Do you think 2amps would cause a fire?

Thanks,
Drew
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Quote
Do you think 2amps would cause a fire?
What anyone thinks is irrelevant. The supply is rated for 1 amp. Don't exceed that. Period.

Pete
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Florida
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I'm not trying to exceed the 1amp rating, but it is being used to power a motor and if the motor stalls it might hit 2 amps before my fuse breaks! Would a few seconds at 2amps cause a fire?

Thanks,
Drew
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If its a "switching" regulator, it will likely just shut down. (small & compact design)
If its a linear regulator, the output will start dropping as the current goes past 1A and it starts getting hot to the point of failure/fire.
(larger, blockier design)
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Florida
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Are the "switching" regulators light compared to the linear regulators? Also It is newer. Does that matter with which one it is?

Thanks!
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Yes, switching are light compared to linear - no big bulky transformer inside.

"Does it matter which one?"

Yes:
If its a "switching" regulator, it will likely just shut down.
If its a linear regulator, the output will start dropping as the current goes past 1A and it starts getting hot to the point of failure/fire.
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
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I think I have a linear regulator. I will just buy a wall wart online that will meat the Specs I need.

Just out of curiosity do they have a capacitor in them because it seems that it holds it's charge a good while after its been unplugged.

Thanks for all the help!
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I would doubt any certified wall wart would catch on fire if the output is dead shorted. I would think that any device with "user accessable" electrical contacts would be designed with the expectation that the user will sooner or later short the contacts.
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Florida
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If I end up going with the wall wart I have, should the fuse be placed on the positive wire or the negative one?

Thanks!
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If I end up going with the wall wart I have, should the fuse be placed on the positive wire or the negative one?

Thanks!

Makes no difference, the same current flows through both wires. The convention is to put it on the positive, if the circuit it powers uses a negative common.

Lefty
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Yes, they have caps.
Fuse on positive.
2A?
http://www.dipmicro.com/store/DCA-0520
4A?
http://www.mpja.com/5-Volt-DC-Plug-Power-Supply-4A-Regulated/productinfo/18520%20PS/

I use both of these.
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Thanks for the help everybody!
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