External hard drive power requirement

Question

I have a second hard drive identical to the primary hard drive for the Latitude D600. I have a external enclosure and a USB cable (third party- ME 930 series - USB2.0 2.5' Enclosure). It has a location for an external power connection. The problem is that if I try to run it without the external power connection and just plug it in to the USB then it gives me a error message of Power Surge in the port replicator and it does not come up. If I attach it to a desktop it works fine but I guess the laptop does not have enough power to spare. My question is what power requirements does it have and is there a standard power adapter for this?

JersWork · Answer

All external enclosures for 2.5 inch notebook drives that I have seen have the same external power connector.  They use a 5V power supply and vary in current ranging from 750 mA up to 3.0 A.  The drives themselves usually require less than 500 mA (otherwise they can't power from teh USB bus),  and often the external enclosure will provide a cable to draw power from the keyboard port (if you have one) and supply it to the drive.   Each enclosure will have its own power adapter requirements,  but  generally speaking,  most use the same as a 'Radio Shack 'H' plug' and have a 'tip positive' polarity.  I also have three USB hubs that use the same power adapter plug/voltage/polarity,  as well as one PCMCIA USB2 card.  It looks like vendors may be 'standardizing' on this connector/voltage/polarity because the parts then become a commodity and can be gotten cheaply...   If you get a chance,  you might want to try to use a FireLite external drive enclosure.  Of the ones I've seen,  they seem to have the lowest power requirements.  When connected to an XP system,  the Device Manager reports that they are only using about 2 mA of crrent from the bus,  even when powered from the bus.  Compare that to the 96 mA needed by my 'SmartDrive' combo (Firewire-USB 2) enclosure.  I don't have access to a newer Dell to test it,  but I suspect that it might actually work powered from teh USB bus. Message Edited by JersWork on 03-24-2005 04:39 PM

TDunn · Answer

All of the new Dells are underpowered for USB hard drives. You have to use external power
or get an enclosure that uses 2 USB ports or USB/1394 for both power and data.
My old I8000 runs stuff fine but all of the new units....starting with the I8500...that I have
tried...don't have enough juice to run even a Creative MP3+...................TD

JersWork · Answer

I just tried a few drives on a co-worker's Inspiron 5150 today. They both worked great, and had no problems.

I have tried 3 different external USB2 enclosures. According to XP, they each use different amounts of power as reported by the Device Manager showing the Power tab of the USB Root Hub to which the drive is associated. On my Thinkpad, one enclosure reports 96 mA usage (for a USB2/Firewire combo enclosure), one reports 2 mA usage (for a USB2/USB1.1 only) and the last reports 0 mA (also USB2/USB1.1 only). I can run all 3 drives using my 3' USB cable, but only 2 of them using my "high quality gold" 6' cable. Using the longer cable, the 96mA drive won't spin-up properly.

Connected to my Friend's 5150, the 96mA drive would not even spin-up at all with any cable, not even a 4" cable which has always worked for me on my Thinkpad. The other two drives work great using the 6' cable, the 3' cable, and the 4" cable. All 3 drives are good, and all 3 cables are good, yet the one drive will not work on the 5150 at all, and that same drive won't work on the ThinkPad with teh 6' cable. I have not tried it, but a friend also has a USB2.0 only enclosure which looks almost identical to my combo enclosure, and his HP notebook also reports his drive as using 96mA on the USB Root Hub in Device Manager.

The enclosures that work are a FireLite drive from SmartDisk, and a generic no-name enclosure which looks like this one http://www.meritline.com/usb-hard-disk-enclosure-25.html (anthough it came from a different source).

I know that the FireLite drive enclosure is using an NEC chipset in it, and I'm uncertain about the generic one as there was only 1 chip and it had a sticker over the chipset so I couldn't get the details on it. According to some research, a Meritline Tech reports that their enclosure uses the same NEC chipset as the FireLite, so it might also have the same low-power requirements. One last hing to note is that the FireLite drive will also power itself though the bus when attached to a battery-powered USB2 hub (CyerPower CP-H420MP) which powers using 4 'AAA' batteries (650 mAh NiMH), which won't power the 96mA enclosure.

I haven't found a source to buy the FireLite encolsures without a drive, so they are a little pricey. I got mine on clearance with a 5400RPM 80GB drive for $159 (plus tax). The generic enclosure I tested was bought at a local CompUSA store for under $20. Considering that these have both been tested on an Inspiron 5150 and work, it might be worth the little extra money to get something that you can use. I know I am considering replacing my two 96mA enclosures with the generic ones so that I can eliminate the need for special cables in order to run my drives...

TDunn · Answer

Excellent work.  Thanks for checking it out.  I've seen posts about it since the curent models came out.  I think you are the first to offer up solid info................TD

JersWork · Answer

Here is a little more info for you as well.  The 'generic enclosure' is from CompUSA and is sold as their own brand.  It looks a little clunky (more blocky than my older enclosures which draw almost 50x the power from the USB port).  I still prefer the styling/appearance of the FireLite,  but since I can get the CompUSA enclosure for $20,  and buy an 80 GB/5400 RPM drive from CompUSA for another $159,  and it costs about $210 for the equivilent in the FireLite,  I will go with the more blocky look.  Besides,  they stack a little better that way.  ;)

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External hard drive power requirement

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