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Limiting current from a 5v power supply

I'm trying to build a DIY Xbox Kinect adapter to be able to plug the Kinect into my computer, but I'm getting some shaky information. From what I've seen, the official Kinect adapter (for using the Kinect with an non-slim Xbox 360) outputs 1.08A @ 12V. I've got a power supply that outputs 12V @ 3A and I need to know whether using this will damage the Kinect.

My understanding is that a circuit will only draw as much current as is required for it to operate. For example, I can connect an LED that requires 20mA @ 3.3V, in series with an 85 ohm resistor, to a wall-wort power supply that outputs 850mA @ 5V. Computer PSUs generally have a 12V rail with as high as 50A. I could plug a hard drive into one of those rails (as the only load on that rail) and nothing bad happens, and I guarantee that the HDD isn't drawing 50A.

At any rate, am I correct in assuming that using a power supply rated for a higher current won't damage the circuit, as the circuit will only pull as much as it needs?

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Yes, yes, yes. Yes. That is correct. It's also probably going to get closed as a duplicate, but you came to the right place to find the answers =) –  JustJeff Apr 5 '12 at 0:22
    
Thanks a ton, really appreciate the quick answer :) –  HaLo2FrEeEk Apr 5 '12 at 3:41
    
well, since the closers haven't swarmed in .. –  JustJeff Apr 5 '12 at 10:34
    
@JustJeff, or you could vote to close and tell the OP where the answer already exists, which voting to close as duplicate will give a link –  Kortuk Apr 5 '12 at 13:28
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marked as duplicate by Kortuk Apr 5 '12 at 13:27

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2 Answers

You are correct. You can also think of it this way - you know a 50A power supply doesn't force 50A out all the time, b/c with nothing connected, you don't see a 50A arc ripping through the air between the terminals!

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Jeff is right saying that it will give only what the load is asking; but pay attention:

Up to 50A, it will give all the current the load will ask!!

So if you connect a LED and nothing else, you will see it turning into a plasma blob unless there is some protection mechanism; the principle is that you want also some protection in the case that your load is doing something strange.

So, it will work but pay attention to what you connect to it!

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You're right, although I'm 99.9% sure that the kinect has its own current limiting hardware, plus a ton of other people I've read about have used computer power supplies whose maximum current rating far exceeds what the kinect needs and they haven't had any issues. Thanks again for all the help guys, kinect on my computer, here I come! –  HaLo2FrEeEk Apr 5 '12 at 19:25
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