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2.5 size laptop harddrive and external drive

Posted on 2006-07-22
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I wanted to get a 100gig 2.5 laptop harddrive and then an external case for it so i can have it as my portable drive.  My question is will all 2.5 laptop harddrive work as an external drive?  Meaning just using the usb to power it without any power adapter?

Thanks
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Question by:borg48
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17 Comments
 
LVL 31

Expert Comment

by:rid
ID: 17160957
I just lookad at an old(-ish) 6 GB laptop HD. Its power rating is 5 V 500 mA, which is about what a USB port can deliver. Newer drives may take less power, but the enclosure circuitry may need some overhead.... You need to look at power needs for the components involved - 500 mA is max power load on a USB port, for a laptop probably max total power drain from all USB ports.
/RID
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LVL 49

Expert Comment

by:dbrunton
ID: 17160972
No

Older ones may not.  Newer ones should.  You may need to use a double USB connector, that is, two USB connectors to the drive from the computer to supply suficient power for the drive.
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LVL 6

Expert Comment

by:stevepo
ID: 17161014
It depends upon the enclosure.

Here is a link to a list of enclosures of various prices for 2.5 inch hard drives which DON'T require external power: http://www.newegg.com/Product/ProductList.asp?N=2010090092+1053807124+1053907127&Submit=ENE&SubCategory=92

take your pick and enjoy!
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garycase earned 200 total points
ID: 17161016
A typical notebook hard drive (I just checked the specs for an 80GB and a 120GB to confirm this) draws around 400ma when idling, and 500ma during a read/write cycle; so it's right at the USB power spec.   An external enclosure's IDE controller will also draw a small amount -- so you're "pushing" it to power the drive just from the USB port.

Will it work?   ... almost certainly.   But there are a LOT of issues on this forum with failed USB ports; and in almost every case they're been used to power a lot of devices that pushed the spec.   Laptops are even more likely to have this problem, as many laptops can't support more than a total of 500ma, even if they have multiple USB ports.

... so if you use it with a laptop I would not have any other USB device connected at the same time;  and if you're using it in an environment where you could use an external power supply, I would recommend you use it => it's simply more reliable and less likely to cause any problems with your USB controller.   Most of the "self-powered" USB drives (e.g. WD Passport) also provide for external power for that very reason.
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LVL 70

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by:garycase
ID: 17161040
... look carefully at the list of enclosures stevepo posted;  nearly ALL of them (in fact all of the ones I looked at that have a picture of the rear of the enclosure) have a jack for an external power adapter;  and many have notes that indicate you MAY need one;  or someone has mentioned that in the reviews.  Some of them do have provisions for using two USB connections, to get more power from the 2nd port (but as I noted, this is a bad idea with a laptop).

Bottom line:  self-powering a notebook drive from a USB port does work;  but when you do that you're at the margins of the USB spec on power => so don't be surprised if you eventually have problems with your USB ports if you do this routinely, or if you use the drive with other USB devices.
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by:stevepo
ID: 17161077
True, many of them do use 2 USB ports, also you want to be careful of how many RPM the drive your going to be putting into the enclosure is.  Some of the reviews stated that 7200 RPM are too much for some of the enclosures.  Read the product specs carefully and buy a trusted brand, it seems that there are more bad reviews for the less trusted brands.
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LVL 26

Expert Comment

by:PCBONEZ
ID: 17162355
I use several kinds of these.
If you are connecting to a laptop then use an AC adapter for the USB drive. ~ End of story...
That's the only SAFE way to go.
Don't risk using one without an AC adapter unless you're good with possibly replacing a laptop motherboard if it doesn't work as expected.

The two USB ports type box works in theory only. There is no way to 'know' if two adjacent USB ports on a given laptop were implimented (wired) as two completely seperate ports or if they are in affect a hub. If they are wired as a hub the max for BOTH ports in combination is still 500 mA.
I HAVE seen notes in Laptop manuals that specify no more than 500 mA TOTAL on all the USB ports.

These portable drive boxes that come without AC adapters are intended for use with desktops.
(Even the two USB cable versions.)
The intent of two USB cables is not so much to spread the load over USB ports as it is to get more power to a high RPM drive.

Note: The USB ports on 'some' older desktops (usually with the older version 1.1 USB) have no more power handling capacity than laptops. - 500 mA max.

If you are going to use this with the same laptop every time then why don't you simply install a larger drive.

If you want portable then you may be connecting it to someone elses laptop at some point.
Lacking the AC adapter you risk frying THEIR motherboard.
Do you wanna replace THEIR motherboard because you fried it for them?
~ Get the AC adapter!!!!!!!!!
.
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LVL 70

Expert Comment

by:garycase
ID: 17162370
... PCBonez said what I was implying -- but a lot more directly.   Bottom line:  they work without an adapter;  but there's a reason all of the boxes have an input for an A/C adapter!   As I said, they are "on the margins" of the USB spec ==> and it's never a good idea to use equipment on the margins.   You're just begging for failures ... and the point about frying someone ELSE's USB ports is a good one.
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Expert Comment

by:tmj883
ID: 17165034
Just an echo...
I'd rather fry a $15 USB hub than a $$$$laptop mainboard...T
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by:JamesTX10
ID: 17167955
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LVL 26

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by:PCBONEZ
ID: 17169741
Review on the STORE-IT drive:

http://www.technobrains.com/phpbb2/viewtopic.php?p=918

Quote: "The Store-It Drive is USB 2.0 based and any computer with USB 1.1 will require the second USB connection for that added power."

Store-it + USB 1.1 + One USB Port = Dead USB Port

Don't plug that thing into MY laptop!
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LVL 9

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by:JamesTX10
ID: 17169772
But if he has USB 2.0 then it works great.
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LVL 70

Expert Comment

by:garycase
ID: 17169841
"... it works great ..." => but you are, whether you realize it or not, running at the "threshold" of the capabilities of the USB port.   Kind of like driving your car at the red line all the time => it will work fine until the engine blows.
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Author Comment

by:borg48
ID: 17219173
Excuse my ignorance, but who do i give credit to on this since everyone gave such good information about it.
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by:JamesTX10
ID: 17219215
You can select split points and give as many to each person that you would like to.
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by:garycase
ID: 17220081
... you can, as noted split points => but there's a minimum of 20 points, so you can only select two answers unless you increase the points for the question.
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