AC-to-USB can't be so hard!?
April 25, 2006 9:53 PM   Subscribe

Can I use a generic AC-to-USB adapter to charge my MP3 player?

I have a Creative Zen MicroPhoto. It's a very nice MP3 player, but the only way to charge it (out of the box) is by connecting it to a USB port on a computer. This presents obvious problems if you're traveling and don't always have a PC handy. Creative, of course, would love to help me out, but their AC adapter is outrageously priced. What are the chances that I'll damage the player if I use a generic AC-to-USB adapter, say, like this? (Could there be something about that adapter that makes it only compatible with iPods?) All USB adapters should have the same specifications, right?
posted by epimorph to Technology (10 answers total)
Best answer: The chances of damage are very low. The USB standard includes a standard voltage (5V, I think), and that's the voltage that this adapter will supply to your device.
posted by mr_roboto at 9:56 PM on April 25, 2006

Yes, USB follows a standard and all USB chargers should be rated for 5V and up to 500 mA, and that's really all there is to know about them.
posted by musicinmybrain at 10:23 PM on April 25, 2006

Yeah, the whole point of a USB AC adapter is that it duplicates the power you'd get from a USB port.
posted by kindall at 10:23 PM on April 25, 2006

At the risk of sounding redundant... it's fine. To add something: I've been using a similar item by the same manufacturer, also purchased from Amazon, and it seems to be made well, albeit cheaply.
posted by fvox13 at 11:10 PM on April 25, 2006

Response by poster: Thank you, everyone! It's as I suspected. I guess I was being overly protective of my shiny toy.
posted by epimorph at 12:12 AM on April 26, 2006

I worried about this, too, with my ipod, and got a sony USB charger. I worried about it again when I got a cigarette lighter USB adapter. They're all the same. I think most USB devices will take anywhere from 3-30V, anyway.
posted by oxonium at 12:47 AM on April 26, 2006

I think most USB devices will take anywhere from 3-30V, anyway.

Doubtful. According to the USB spec, "The voltage supplied by high-powered hub ports is 4.75 V to 5.25 V. The voltage supplied by low-powered hub ports is 4.4 V to 5.25 V." Given that, it would be a needless challenge to design devices to operate over a full order of magnitude of supply voltages.
posted by musicinmybrain at 5:28 AM on April 26, 2006

Best answer: Theoretically, a really cheap crappy one would put out bad power, but that's true of cheap USB hubs as well.

USB power is supposed to be regulated -- it shouldn't matter what load is on the port, so long as the current draw doesn't exceed 500ma. If the adapter is compliant, it'll put out at least 4.4V, and not more than 5.25V, for any current draw from .1uA to 500mA.

Now, USB devices that require less voltage than that may well have voltage regulators onboard, and can take a wide variety of power. With the cost of voltage regulator/DC-DC converter ICs plummeting, more and more devices are including one -- despite the extra cost, you save money in the long run with better reliability and less support (since Joe User's weak or strong USB port still powers your device, despite the port being completely out-of-spec.)

If you're paranoid about the converter, you can test it -- get a dummy load (a couple of resistors), hook it up and see what the voltage and current draw are. Ideally, you'd want to see 5V from 0 to 500mA draw. You won't, but as long as it stays within the numbers above, you're adapter will work fine.

But that's paranoia. I'd quickly meter it to make sure it isn't completely bogus if I'd never heard of the manufactuer, but if it came up at 5V no load, I'd plug something into it.
posted by eriko at 5:51 AM on April 26, 2006

FWIW, my ipod nano (quite needlessly, you're right) claims to be fine with anything from 5-30VDC.
posted by oxonium at 6:15 AM on April 26, 2006

in the case of the iPods, it's because you can charge over FireWire, which can supply up to 30VDC. the new ones support charging but not data transfer. (kinda a derail but yano)
posted by mrg at 8:27 AM on April 26, 2006

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