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Powering external HDD with computer PSU

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January 26, 2013 4:13:17 AM

I currently have two Seagate 2TB desktop expansion drives, and as all desktop drives do, they have a big bulky power brick for powering them. I have a spare PSU sitting around that I planned on using to power other 12V accessories, and was wondering if I could use this to power my external drives, instead of having to use the bricks?

What I plan on doing is cutting the chord that goes from the HDD to the power brick, and just connecting the wires to the 12V rails from the PSU, that way I can just easily use the same connector that fits right into the back of the HDD.

Now I'm certain that my PSU will be able to provide enough power to the drives, however my question is about how safe this would be? Would it possibly damage the drives in any way?

I'm assuming that it wouldn't, seeing as though a computer PSU is what's used to power internal computer drives anyway, but I just want to make sure before I go ahead and connect it up, and possibly risk losing all my data.

Thanks
a b G Storage
January 26, 2013 4:45:11 AM

How do you plan to tap into the 12 rails? If you don't know what you're you can burn out the psu or worse cause a fire. A safer way is to put the hhd into a external usb housing and get power from the usb port. You could take the hhd out of the housing and mount them inside the and get power withe sata cables.























i
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January 26, 2013 4:45:18 AM

Thanks for the reply mate.. However I don't plan on hooking up two PSU's for a single machine.. I only plan on using a seperate PSU to power the external drives that I have (which would otherwise be power by a big power brick/wall wart/transformer - depending on what you refer to it as). The drives will still plug into my laptop over USB, but will be powered from the computer PSU that I have external to any other computer.. If that makes sense?
January 26, 2013 4:48:45 AM

Sorry I didn't see your message before I replied Goodeggray.

I guess I wasn't clear enough, the drives are already external drives in an external case, exactly like this one http://www.villman.com/product_photos/seagate-1tb.gif.

And I plan on using spades connectores to safely connect them together
a b G Storage
January 26, 2013 4:59:59 AM

Didn't realize you had a laptop. You only dealing with 12V dc. Cant do too much damage. Just make sure all the wires are well insulated.













































y
January 26, 2013 5:10:11 AM

Goodeggray said:
Didn't realize you had a laptop. You only dealing with 12V dc. Cant do too much damage. Just make sure all the wires are well insulated.

y


Fantastic. I thought this would have been the case, but just wanted to ask other peoples opinions before I went ahead with it, in case I as missing something silly.

Thanks for your advice!
a c 303 G Storage
January 26, 2013 6:53:10 AM

Computer PSUs should ideally have a minimum load in order to regulate properly. The scenario you have described would leave the +5V rail unloaded. You might like to consider adding a suitable load resistor to this rail.

BTW, Seagate's power adapters have DC plugs whose centre pin is positive. Make sure you get the polarity right.

Just FYI, in order to turn on the PSU, you would need to short the PS_ON pin to Ground.

http://pinoutsguide.com/Power/atx_v2_pinout.shtml
January 26, 2013 11:47:12 AM

Thanks for the reply mate.

I'm aware of the need for a load for the PSU to turn on, as well as connecting the green wire to ground. The PSU will also be running some fans anyway, which will be cooling the external drives in a rack that I am going to build for them, so there should be enough load to keep it happy.

Polarity however could prove to be a little more difficult.. Although I'm sure I can just plug the brick in and test the wires after they've been cut and match them up with the other side :) .

Thanks again,
Denno
a c 303 G Storage
January 26, 2013 10:42:19 PM

IME most fans are 12V devices. They don't usually draw power from the +5V rail.

It seems like you have the polarity issue sorted out, but just FYI a good rule of thumb is to test the resistance between each of the wires and a known ground point, such as the ground pin at the USB connector. That will be your negative terminal.
January 26, 2013 10:48:51 PM

fzabkar said:
IME most fans are 12V devices. They don't usually draw power from the +5V rail.

It seems like you have the polarity issue sorted out, but just FYI a good rule of thumb is to test the resistance between each of the wires and a known ground point, such as the ground pin at the USB connector. That will be your negative terminal.


Oh so you're saying that both the 12V rail AND the 5V rail need a decent load for the PSU to be stable? I thought it was just the 12V rail :/ ..

I guess I'll have to find something that's 5V then! I do have a couple of USB power fans, which I could cut up and connect to the 5V PSU rails.. Although, seeing as though they're USB powered, they don't draw a lot of current..

What would you suggest being a good resistor value to put on the 5V rail? Or the best way to effectively load the rail, without wasting energy, as a resistor would do.

Thanks
Denno
a c 303 G Storage
January 26, 2013 11:59:55 PM

Another consideration would be how the load on the 12V rail varies when the external drives spin down during power saving mode.

Furthermore, some (most ?) external drives will not spin up unless they detect the presence of a USB host.
January 27, 2013 12:10:51 AM

I've got 4 fans that I'm going to have connected to the 12V rails, so whenever the PSU is on, these fans will be on. So I think I'm safe in that regard.
!