Make external hard drives usb powered

[sram]

Hello folks. You know that external hard drives are good/easy way to gain additional capacity with no much hassle. All of course require power, but some require more power than others. It is even more convenient when they are USB powered, especially if one intends to use them with laptops.

Maybe you've already guessed where am I going!! Is it possible to make drives that use a power adapter work with only USB!?? Perhaps by using more than one USB port to get more current?

Does the voltage differ?

Are there USB powered hubs that will enable to get the matching power I need (This will only work for desktops though, it is meaningless for laptops)

It will be neat if it is achievable!


Discuss away, thanks.

 

[ParkingLotLust]

Only problem is that hard drives need +12v and +5v while (pretty sure laptop drives only need +5v) the USB port only supplies +5v at a MAXIMUM 400-500mA. And to get that current, drivers have to request it. So maybe if you used a couple of usb ports through a charge-pump converter or something to boost the voltage, then maybe it's possible.

 

[sram]

Your reply raises this question in my mind. Does all external hard drives that come with power adaptor uses 12 volts? There are slim ones which I think only uses +5 volts.

 

[justDIY]

you should be able to sneak one or two amps out of a motherboard usb port, but that won't likely be enough to run through a boost converter and get enough power at 12v to spin a desktop hard drive

stick with notebook drives, or mod your case to provide a DC power jack for your hard drive.

 

[suicidalmonkey]

USB powered Hard Drives are already manufactured.
They are commonly known as pocket drives.
Here is a link to a shop that sells them in Australia.
http://www.dse.com.au/cgi-bin/dse.storefront/44857dcc0268d5c2273fc0a87f9c0774/Product/View/XH8253

If your looking for information on how you can build one yourself, sorry, but I can't help.

 

[justDIY]

oh i should add ... the 500ma thing is part of the usb 2.0 spec, aka usb high speed (not usb 2.0 aka usb ultraspeed or whatever they're calling it now).

so, knowing that not every system out there will be usb 2.0 compliant, most external drives, even the slim ones with notebook hdds inside them, ship designed for external power. if your systems are all usb 2.0, then you should be able to make a second usb cable with an ordinary power jack on the other end ... so one cable for power, one cable for data... or you could hack open your drive enclosure and jumper the power wires inside

 

[Someone Electro]

USB is curent limited so no way of pulling more out of it.

If your pc has a game port you can use that.Its not curent limited so will suply a lot,but also be careful becuse shorting this can result in damage since you short the PSU over a thin track on the PCB.

 

[evandude]

https://www.newegg.com/Product/Show...KU25+2.5"+USB+2.0+External+Enclosure+-+Retail

There's an example of an external enclosure for laptop drives that uses two USB ports to get enough power. As others suggested, nothing really special except for paralleling the power wires of the two ports, and clearly it's something common and commercially available.

It's not done for 3.5" (desktop) hard drives because they use so much power... for example, a 40GB IDE desktop hard drive from western digital is specified as using 7.5 watts during read/write operations. Since it needs +12v in addition to +5v, that means you also need a DC-DC converter, which introduces some amount of inefficiency, and you probably have to have some more power head room just in case, so in the end you're probably looking at over 10 watts at least. 500mA at 5v from a USB port is 2.5 watts, so at the minimum you would need probably 4 USB ports just to power it... And worse, many of the larger and better drives are rated at around 10 watts for read/write, so you might need 5 or 6 USB ports for those. at that point, running cords to that many USB ports (as well as giving up that many ports that could be used for other devices) would surely be less desirable than a power adapter.

 

[The Mad Professor]

With the prices of solid state memory dropping as they are, coupled with improvements to the lithography process , going digital is looking more attractive. Thumb-drives with a four Gig capacity are now available.

 

[justDIY]

don't underestimate the electrical load of a flash drive either, however ... I have a flash drive that will only work on self-powered hubs or direct to the motherboard ... try to run it off a passive hub (like the one in my keyboard) and I get a device exceeds bus power error or some such

 

[The Mad Professor]

hmm , what about using the USB supply to charge a small battery pack or large value capacitor located local to hardware and use the stored energy to supplement the devices power requirements under load conditions.

 

[justDIY]

well sure, but you still have a 2.5 watt/hour maximum charge rate ... if you're running a drive that takes an average of 5 watt/hour worth of power, you'll need a decent battery to get good runtime, and it will take forever to recharge

look at firewire enclosures ... the firewire bus supplies a lot more power, but it's not common on peecees

 

[Dr.EM]

We always get that "low power" notice for USB at college in thier macs. There are only 3 sockets on the back, and all are used all the time. It seems that the USB MIDI keyboard uses less power than the little memory sticks, so we usually connect that to the keyboard USB socket so theres a free motherboard USB for the memory sticks.

Firewire is usually found on the soundcard for PC, I have one because I have a decent soundcard. I think some more recent motherboards have them built on too.

 

[Nigel Goodwin]

Firewire is usually found on the soundcard for PC, I have one because I have a decent soundcard. I think some more recent motherboards have them built on too.

Seems a strange place to have Firewire?, on a sound card?.

As you say, some modern motherboards have Firewire, or you can easily buy Firewire cards. I've recently added Firewire to my computer (as I needed to download video from a Mini-DV camcorder - the video of my daughters gig).

As I had no free slots I had to remove an extra USB card I had, so I bought a Belkin combined Firewire/USB 2.0 card - with three of each, and it came with a Firewire cable as well. Very pleased with it, dropped straight in, and worked immediately, no drivers required under XP.

 

[Blueteeth]

Hi,

Not sure if this is what you're after..
**broken link removed**

They're avaiable from a few companies, you simply provide the HD and a USB cable. It says 'self powered' but even if it had a 5v-12V converter, I can't see USB 2.0 providing enough current for it. Plus...buying a 'kit' takes all the fun out of designing your own

Blueteeth

 

[evandude]

Yeah, I think by "self-powered" they mean it is powered separately of the PC, so you don't need to connect to any of the normal 4-pin molex power connectors in the PC. Plus it says the case "includes a power supply" which probably means a wallwart. Not that I expect any of these manufacturers to agree on a set of terminology, but I when something is powered off the USB port, it is often referred to as "bus-powered", whereas I have seen some USB hubs that have wallwart power adapters referred to as "self-powered".

not to mention, it is USB1.1 compatible, and USB1.1 supplied even less power per port than USB2.0.

 

[Dr.EM]

Heres and example of one built onto the card:

**broken link removed**

But ones without the socket on the card often have connectivity for one, mine is joined from the card to the front panel of my PC. Soundcards used to have the joystick socket too, which can be made into a MIDI socket with an adapter plug (in fact, it seems probable the jostick communicates through MIDI somehow?).

 

[evandude]

Seems a strange place to have Firewire?, on a sound card?

Not that I use anything like it, but a quick google search turned up some high-end audio devices for recording/etc via firewire. That would explain why the firewire ports appear mostly on more expensive sound cards, for people who are more likely to be buying other expensive audio equipment.

 

[justDIY]

Hi,

Not sure if this is what you're after..
**broken link removed**

They're avaiable from a few companies, you simply provide the HD and a USB cable. It says 'self powered' but even if it had a 5v-12V converter, I can't see USB 2.0 providing enough current for it. Plus...buying a 'kit' takes all the fun out of designing your own

Blueteeth

that's deffinately an out of spec device ... no way could it power a 3.5" hdd relying on the "standard" 100ma or even the extended 500ma from a usb port ... they're relying on the fact there is no real current limiting hardware in usb (just like all this usb powered non-computer junk you can get now)

Maxim has an interesting app-note about charging batteries from the USB, and some analysis of the out-of-spec current supply capabilities of a typical usb port... I'll try to dig this up.