External HDD & usb power?

Hi

I'm looking to get the Western Digital 250GB My Passport Essential hard disk to use with my laptop.

However I've read that the usb ports don't have enough power. The HDD apparently needs 1000mA but laptop usb ports are only up to 500mA so it won't work properly.


http://www.amazon.co.uk/Western-Digital-Passport-Essential-250GB/dp/B0012IOHVM/ref=cm_cr_pr_product_top

So I was wondering has anyone used a hard disk like this with their laptops.

Should I look for a different product?

Can anyone recommend a portable external hard disk to use with my laptop.

Thanks

 

That should work fine, I've used the 250GB with a single head cable and it was ok. I can't recall if it came with a dual head cable though.

 

It might work, but I think its not good for the drive, to supply it with less current than the rated value.

The drive may come with a USB Y-Cable if those are the specs (1000mA), otherwise you can buy one yourself.



EDIT: I looked up WDC, and if they are using the WD Scorpio Blue, the max current reqd is 500mA. There are only a couple of drives that actually require more current than 500mA, and hence need a Y-Cable to work properly when connected externally via USB as the power source.

 

yeah, I have the same WD 250GB external hdd and it works perfect with my old and new laptops without a Y-cable. Single head cable is just fine and it is less messy...

 

All the recent external HDDs I have used have been able to run off a single USB port. Maybe USB can provide temporary extra power or maybe the HDDs adjust their power demands to meet the supply.

John

 

I think HDDs adjust their power demands, and run on slightly lower current. I think 500mA is the max current reqd during R/W. USB ports cannot provide more than 500mA, as that may lead to a USB Power Surge, and the USB controller does not run the device, and gives an error.

AFAIK, there is no mobile drive that requires more than 500mA....

 

I recall the WD2500BEVS had a jump option which would reduce the startup power. I don't know, however, if this jumper was put on the HDDs put into enclosures.

Also, I've just looked at the board in one of my enclosures and there is a capacitor which could be there to slightly smooth the power demands. One way or another, units such as the WD Passport are designed to run off the power from one USB port.

John

 

So I should be safe, I was concerned because I've been reading quite a few user reviews with mixed feedback. Most of the cons were related with its usb power usage.

Looking for Y-cable if needed I came across this reviewer.

http://www.amazon.co.uk/LINDY-USB-Cable-Dual-Power/dp/B000FKP7XK/ref=sr_1_9?ie=UTF8&s=electronics&qid=1223847713&sr=8-9

Went to WD site and at the last sentence of the testimonial tab it says
http://www.wdc.com/en/products/products.asp?driveid=525

"* An optional cable is available for the few computers that limit power from the USB port."

ramgen and goofball have their ones working fine so I hope it'll be ok for me too.

EDIT - By the way I also run a Zalman NC-1000 notebookcooler and mice by usb.

 

The problem I've had with the USB powered external HDs is they knock the onboard USB off on the laptop.

 

Found some info on its power usage which is interesting.

http://wdc.custhelp.com/cgi-bin/wdc.cfg/php/enduser/std_adp.php?p_faqid=1481&p_created=1164135184

It says at the bottom of the specifications page:

" Drive Maximum Power Draw (milliamps) 650 Ma"

So a bit over 500Ma USB specs but I guess it should still work fine since it has for a lot of people.

 

I have disassembled my WD external harddrive and it had WD2500BEVT hard disk in it. The max. power requirement for that is 500mA (written on the hdd). I would assume another 50mA for the little circuitry that does SATA<->USB conversion. It will sum up to 550mA.

My guess is that although the power capacity of the USB ports is technically limited to 500mA, laptop companies put some leeway for that. (may be 600-650mA max power support)