USB Interface - Hard Drives

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#41

07-25-2009, 11:38 AM

reako

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Quote:

Originally Posted by awptickes

You're misunderstanding. He/she is talking about something that uses a LM7805 or similar voltage regulator and steps the voltage down from 12v to 5v. Think about the USB device chargers that go into a cigarette lighter jack.

I have a feeling that's what the Poster was talking about.

Unless they're talking about 12V usb devices, which you don't see too often in the real world:

Thanks. He said "12V power socket plug that terminates in a USB port" what you show there looks to be a USB port terminating into a 12V power socket. I see these all the time. That would make much more sense of course.

#42

07-25-2009, 11:42 AM

awptickes

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Yeah, I was confused at first, then I thought about what he was trying to tell everyone to do.

#43

07-25-2009, 11:03 PM

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Quote:

Originally Posted by reako

Aren't they they same thing? 5v (500mA) power is the same as 5v (500mA) current....

Hmmm I'm no electrician but I remember that current and power are slightly different. Current figures in the basic Ohm's Law equation (I = V/R, where I is current, V is voltage and R is resistance); power is a little more indirect (P = I x V).

And you measure power with watts, not amperes

FYI

Awptickes is correct on the USB charging cigarette lighter plug by the way...guess I should've been more specific

Sorry bout that.