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Portable External Drive
- Thread starter Pooky
- Start date
It's more the amount of current they can supply that matters. Will have to measure in series with a variable load to check that.
Here is a comparison of the maximum power consumption for a number of 2.5" hard drives. Most devices comfortably exceed 2.5W (i.e. 5V * 0.5A) so would surely need to be driven from 2 USB 2.0 ports unless the single port is capable of supplying substantially more than 500mA?
http://www.tomshardware.com/charts/2.5-hard-drive-charts-2008/Maximum-Power-Consumption,684.html
http://www.tomshardware.com/charts/2.5-hard-drive-charts-2008/Maximum-Power-Consumption,684.html
Correct, Yotch.
There are just so many urban myths floating around about USB power.... I don't know why.
Edit: That list is a little dated (2008) but bottom line is if maximum power of drive + USB controller > 2.5W, you need a Y.
There are just so many urban myths floating around about USB power.... I don't know why.
Edit: That list is a little dated (2008) but bottom line is if maximum power of drive + USB controller > 2.5W, you need a Y.
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That Tom's Hardware comparison has 2 fields that are applicable, idle power and maximum power consumption. All of the Western Digital drives in that test have maximum power consumption of more than 2.5W which according to what you said means that they will need 2x USB ports for power. However I've owned one of these drives, and seen other people with them running them in USB enclosures and they run 100%. We need to figure out how relative the 'maximum power consumption' term is, ie to what extent the drive operates when it can't draw full power, ie 2.5W and below.
I hear you, and that is where a lot of the cheaper external casing manufacturers seem to be taking "risks". It's cheaper for them to supply a single cable with their product than with a Y, (and more convenient to the end user) thus may perceived to be a better deal than another manufacturer that supplies a Y cable with their enclosure.
It's not what I said, it's what has been agreed and written into the USB specification. You may well get an extra 50mA while charging your BB, but plug another BB in on the other port? Maybe your 50mA disappears. So it will then take a little longer to charge your phone. No biggie. But for something more sensitive like a HDD?
Those figures quotes are nominal, I have no idea of the specified tolerances on them are quoted in the spec, will have to refer to the fine print of said spec to see.
Net result if a drive draws more than the maximum and it gives problems, whatever those may be, you can't blame it in the disk drive manufacturer, it is outside the spec, period.
Also don't overlook the fact that the drive electronics also consumes power from the 500mA total, reducing the available amount to the HDD.
I did say some manufacturers ports can supply more power, by all means if you have one you can toss the Y in favour of a single for your HDD.
Here is a write up by Gigabyte, heavily slanted of course
http://es.gigabyte.com/global/es/pages/239/3x-usb-power.html
It's not what I said, it's what has been agreed and written into the USB specification. You may well get an extra 50mA while charging your BB, but plug another BB in on the other port? Maybe your 50mA disappears. So it will then take a little longer to charge your phone. No biggie. But for something more sensitive like a HDD?
Those figures quotes are nominal, I have no idea of the specified tolerances on them are quoted in the spec, will have to refer to the fine print of said spec to see.
Net result if a drive draws more than the maximum and it gives problems, whatever those may be, you can't blame it in the disk drive manufacturer, it is outside the spec, period.
Also don't overlook the fact that the drive electronics also consumes power from the 500mA total, reducing the available amount to the HDD.
I did say some manufacturers ports can supply more power, by all means if you have one you can toss the Y in favour of a single for your HDD.
Here is a write up by Gigabyte, heavily slanted of course
http://es.gigabyte.com/global/es/pages/239/3x-usb-power.html
It's a good article, especially the USB gadgets they test. A USB foot warmer in the shape of a fluffy lion thing!? Classic
True, underpowing something as sensitive as a HDD is a bad idea. The controller, however, should be clever enough not to let the HDD run if the power it's getting isn't adequate, which I'm sure is the case.
Running with a Y is definitely a good idea, if you have one might as well use it, can't do any harm.
Interesting topic this. Requires some more research when time permits.
Hmm, you wouldn't catch my feet dead in there!
Interesting indeed. I always use my Y on my aging 250GB FreeAgent, no use asking for trouble.
Oh, and remember to plug both connecters into the PC ports first before plugging in the drive, not the other way around, so as to have both connected at the PC at spin-up time.
Soz for the derail, Pooks, but it was just a mini one.
Interesting indeed. I always use my Y on my aging 250GB FreeAgent, no use asking for trouble.
Oh, and remember to plug both connecters into the PC ports first before plugging in the drive, not the other way around, so as to have both connected at the PC at spin-up time.
Soz for the derail, Pooks, but it was just a mini one.
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PostmanPot
Honorary Master
You may also damage the USB port if you consistently draw more than 500mA due to internal heating. My Freecom ToughDrive Leather 320GB drive (Samsung) which was only supplied with a single USB cable developed all kinds of problems, partcularly when copying large numbers of small files until the manufacturer sent me a Y-cable. After having to reformat the drive I will only be using a Y-cable from now on.
@Pooky: www.computersonly.co.za have the Transcend Storejet 25M3 500GB USB 3.0 for R629. Some of the online places like Prophecy also sell it for a similar price.
@Pooky: www.computersonly.co.za have the Transcend Storejet 25M3 500GB USB 3.0 for R629. Some of the online places like Prophecy also sell it for a similar price.
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@South_Bit
Here you go, some light reading on the USB specifications for ya.
http://www.usb.org/developers/docs/
No, Yotch, the USB controller port must limit you drawing more current than the specification states (mode dependant), to prevent damage.
An interesting book on the matter, although written for the developer, but it also covers the hardware.
Here you go, some light reading on the USB specifications for ya.
http://www.usb.org/developers/docs/
No, Yotch, the USB controller port must limit you drawing more current than the specification states (mode dependant), to prevent damage.
An interesting book on the matter, although written for the developer, but it also covers the hardware.
PostmanPot
Honorary Master
Prices?
Samsung.
Samsung.
Thanks for that, nothing like some light reading
The literature makes sense, however the way some things actually function when you're testing them is the interesting part. Lots of free time with a multimeter is required.