[solved for me] 2 USB not deliver enough power to a HDD?

postcd

Member
Hello,

i have several 3,5" HDDs 5-7k rpm

and i bought this cable to externally connect HDD via USB ports:
http://www.buyincoins.com/item/44426.html

BUT it appears it do not make spinning any of my HDD no mater which USB ports i use/combine. I tried on 2 PCs.

So i want to ask how is that possible, per USB 2.0 specification i thought i can get up to 2x500mA from 2 USB ports.

and on example one of my HDD is:
5V, 0.65A
12V, 0,6A

so i have 1,0A right, so why it do not works?

Please can i use USB splitter cable to make lets say 3-4 USB ports out of 2 USB ports of the cable i bought above mentioned?

So i would deliver lets say 4x500mA would that be enough to make HDD spinning? Thank you
 

Shlouski

VIP Member
This cable you have bought claims to work only with 2.5 inch drives and this is because 3.5 inch drives have higher power consumption and run at 12 volts, this is why 3.5 inch enclosures come with an extra power plug with an adapter that outputs at 12 volts, so 5 volt usb's aren't going to work.
 

postcd

Member
thanks so its probably impossible to power it thru standard PC USB ports..
and if powered by AC adapter, it MUST have 12V ?

then lets say 1-2 USB ports of the connected AC powerred hub will have enough power to spin up 3.5" HDD?
 
Last edited:

beers

Moderator
Staff member
You'd need something with a transformer to convert 5v to 12v for the motor.

Instead of just trying to rig it, itd be less effort and cost to do it correctly with a powered external enclosure.
 

postcd

Member
12v at 0.6 amp is already 6 watts, which is more than those interfaces can provide.
and if usb hub is powered by AC adapter, adapter MUST have 12V ?

then lets say single USB port of the connected AC powered hub will have enough power to spin up 3.5" HDD?
 

strollin

Well-Known Member
No, no, no. USB does not supply 12V at all so if the drive requires 12V, it will NOT work with USB. End of story.
 

Shlouski

VIP Member
and if usb hub is powered by AC adapter, adapter MUST have 12V ?

then lets say single USB port of the connected AC powered hub will have enough power to spin up 3.5" HDD?

Just because a hub is powered by a 12v DC adapter does not mean it is outputting at 12v. The adapter is using alternating current (AC) from the wall socket and outputting at 12v direct current (DC) not AC, with the necessary amps to feed all the usb ports in the hub at 5v. Voltage is like pressure and if the hub was outputting at 12v then it would damage or destroy any usb device you put in it. Even if you were able to get the same wattage normally required to run a hard drive, but using 5v instead of 12v, it still would not work.

Edit: If you really want to run a 12v device from something outputting 5v, then you will need a transformer, it would be easier to use something like this that can do it all: http://www.amazon.co.uk/SATA-Drive-Adapter-Cable-Buyincoins/dp/B001OORMVQ
 
Last edited:

strollin

Well-Known Member
A USB port only supplies 5V and will never supply 12V so since your 3.5" drive requires 12V it CANNOT be powered via USB.

I've answered this on several forums now, is there some reason you don't understand this? It won't matter how many USB ports you gang together, you will never be able to run that drive from USB ports.
 

Agent Smith

Well-Known Member
I've always been able to use a powdered USB adapter connected to a SATA or PATA HDD. What's this 12 volt shit?
 

Shlouski

VIP Member
I've always been able to use a powdered USB adapter connected to a SATA or PATA HDD. What's this 12 volt shit?

Is profanity really necessary?

If you are powering a 5v device that does not exceed the maximum amperage that the port can supply, then it will work off a usb port. If you are trying to power a 12v device like a 3.5 inch HDD off a 5v usb then its not going to work. If you know better then please inform power supply manufactures that they don't need 12v rails, because the 12v devices inside will run fine off 5v o_O.
 

strollin

Well-Known Member
I've always been able to use a powdered USB adapter connected to a SATA or PATA HDD. What's this 12 volt shit?
You can run 2.5" drives from a USB port but the OP is wanting to run a 3.5" drive that requires 12V. I can't say for sure that ALL 3.5" drives require 12V but most, as well as the one the OP is using, do.

BTW, what's a "powdered" USB adapter? :confused:
 

postcd

Member
thanks alot, its now crystal clear for me.

if anyone curious what his HDD needs, just look on the sticker on the HDD. there you will find that voltage needed to run HDD
in my case it was like this:

5V, 0.65A
12V, 0,6A

which appears to mean that 12V is required and as mentioned above, USB ports (no matter how they are powered) do not support it.
 

Agent Smith

Well-Known Member
I have a USB to 3.5 adapter with a power adapter and have connected it to USB many times. Maybe this is some weird HDD?
 

Geoff

VIP Member
I have a USB to 3.5 adapter with a power adapter and have connected it to USB many times. Maybe this is some weird HDD?
As stated many times, the 3.5" drives require too much power to be pulled from two USB 2.0 ports. 3.5" drives use 12v while 2.5" drives use 5v.
 
Top