diwit
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Power for an external HDD

Sun Jul 07, 2013 5:54 pm

Hi All,

I have the Raspberry Pi Model B with its original power adapter (1A).

If I connect a USB external drive to it, the drive tries to start spinning but it won't, and the Raspberry Pi does not detect it. If I connect it using a Y USB cable (1 USB for data + power and the second USB only for power), the Raspberry Pi restarts and the drive does not start spinning anyway.

If I use the Y USB cable, but connect the data + power to the Raspberry Pi and the second USB (power only) to an external USB adapter (from a phone, let's say), the disk starts spinning and the Raspberry detects it and everything is OK.

Can this damage the raspberry? When I disconnect the main power from the Raspberry and the second USB is plugged into the external adapter, the raspberry boots up, even with the hard drive unplugged.

Thanks!

stevech
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Re: Power for an external HDD

Sun Jul 07, 2013 8:36 pm

Use an external drive in an enclosure with its own power supply. Avoid such that are USB powered.

diwit
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Re: Power for an external HDD

Sun Jul 07, 2013 9:36 pm

I am thinking of buying the Plugable USB2-HUB-AG7 powered USB hub, but I have seen a video (https://www.youtube.com/watch?v=0Vc6Jtoi8PA) where they show how you can use a WD My Passport 500GB external hard drive without any external supply or powered USB hub, just using a Nokia AC-10E charger.

The hub is about 33€ including shipping, and the external hard drive is about 50€ (you can get the nokia charger for less than 5€).

Plugable USB2-HUB-AG7: http://www.amazon.co.uk/Plugable-Speed- ... B009R921SE
WD My Passport 500GB: http://www.amazon.co.uk/Passport-500GB- ... B007UOW80O

So can anyone confirm that the WD external hard drive will work on my Raspberry Pi without any external power supply?

Thanks!

mushprin21
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Re: Power for an external HDD

Mon Jul 08, 2013 6:50 am

The PI doesn't have very powerful USB ports. You might have to connect to a USB hub on a USB powered one or use a externally powered one. The latter is the best because all the PI has to do is transmit the data and the power is not scourced from the PI's non-powerful ports.
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surfatwork
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Re: Power for an external HDD

Mon Jul 08, 2013 2:39 pm

most external USB HDDs have a provision to be powered from an external power supply (usually 5V). Just use a suitably powered 5V power supply (e.g. 2A) and use it to power both the Pi and the HDD. I do this and its been fine for months.

plugwash
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Re: Power for an external HDD

Mon Jul 08, 2013 4:58 pm

diwit wrote: If I use the Y USB cable, but connect the data + power to the Raspberry Pi and the second USB (power only) to an external USB adapter (from a phone, let's say), the disk starts spinning and the Raspberry detects it and everything is OK.

Can this damage the raspberry? When I disconnect the main power from the Raspberry and the second USB is plugged into the external adapter, the raspberry boots up, even with the hard drive unplugged.
The Pi doesn't care where power is fed in as long as it makes it to the main power rail somehow. Your setup of using a splitter cable with the data A plug plugged into the Pi, the power A plug plugged into a PSU and the B plug plugged into the hard drive should be fine as long as the PSU is suitable (i'd be looking for one of the 2A USB PSUs sold for use with tablets).

I would advise against connecting a second PSU to the "power" port on the pi as in rare cases power supplies can fight each other which may cause problems.

diwit
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Re: Power for an external HDD

Wed Jul 10, 2013 12:21 am

plugwash wrote:
diwit wrote: If I use the Y USB cable, but connect the data + power to the Raspberry Pi and the second USB (power only) to an external USB adapter (from a phone, let's say), the disk starts spinning and the Raspberry detects it and everything is OK.

Can this damage the raspberry? When I disconnect the main power from the Raspberry and the second USB is plugged into the external adapter, the raspberry boots up, even with the hard drive unplugged.
The Pi doesn't care where power is fed in as long as it makes it to the main power rail somehow. Your setup of using a splitter cable with the data A plug plugged into the Pi, the power A plug plugged into a PSU and the B plug plugged into the hard drive should be fine as long as the PSU is suitable (i'd be looking for one of the 2A USB PSUs sold for use with tablets).

I would advise against connecting a second PSU to the "power" port on the pi as in rare cases power supplies can fight each other which may cause problems.
That would be great/simple/cheap!! But I recall reading somewhere that having the Pi getting power from USBs instead of the microUSB power connection avoids the short protection fuse and other interesting things to protect the power supply and/or schematics (http://raspberrypi.stackexchange.com/qu ... is-it-safe).

Can someone please confirm this would not damage the Pi, bearing in mind that I will have it powered on 24/7??

Thanks!

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Re: Power for an external HDD

Wed Jul 10, 2013 1:29 am

My 2 Rev.2.0 boards (512MB) with a 2.1A Apple iPad adapter; both will not power a USB HDD from one or both ports (Y adapter) Enough current just does not get through F3 (750ma polyfuse (Polymeric Resettable fuse)). They will work if I put an alligator clip connecting both sides of F3 (shorting the fuse). I even had trouble after I replaced F3 with a 1.1A polyfuse. One way I was able to make it work reliably was to plug the data/power leg of the Y cable on my USB HDD into the RasPi and the other, power only, into an Adafruit 1A USB PSU. It worked just fine. The only danger here is it was also back-powering the RasPi.

They are correct, that the RasPi does not care where the operating voltage comes from. For that matter the RasPi itself does not really care where its operating voltage comes from, as long as it is between 4.75 and 5.25 volts. Though I have had stable operation as low as 4.3V.

My back-powered RasPii are completely stable. They both use a mini USB hub with a 2A PSU. they have a 2A polyfuse inside the hubs. Some people have also had good results back-powering from and external HDD (3.5") in an enclosure. These enclosures have 12V and 5V for powering the HDD.

The biggest problem I have seen with back-powered RasPii is that the upstream cables are too long. There also can be quite a bit of loss at the connectors. Use a short cable of reasonable quality and the voltage at TP1/TP2 will rise. The one RasPi is now on a pin header with about 4" wires and the other uses a shortened Male A to Male Mini USB cable of about 5". Both show about 4.9V at TP1/TP2. So if you do choose to back-power make sure you protect the circuit and that you use short cables!
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abramq
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Re: Power for an external HDD

Sun Oct 05, 2014 6:46 pm

So it looks like there is no really working external HDDs, powered by Pi usb port? I havn't find any post with succesful instalation... That's a pity - especially, that Pi B+ version has better power possibility...
Time to look for any Pi alternative ...

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default_user8
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Re: Power for an external HDD

Mon Oct 06, 2014 1:14 am

If you want a board that can handle a usb drive check into a cubietruck. But at $95USD a Pi and a powered usb hub are a lot cheaper.
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abramq
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Re: Power for an external HDD

Mon Oct 06, 2014 6:21 am

Ok, no problem, will you buy my Pi? ;-)

fruit-uk
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Re: Power for an external HDD

Mon Oct 06, 2014 7:09 am

default_user8 wrote:If you want a board that can handle a usb drive check into a cubietruck.
Not a wise choice unless you really know what you are doing IMHO!
...and I believe USB power is current limited but can't remember the details.

To find a drive that you can use with a Pi without using a hub you probably need to look through drive manufacturer's tables until you find one that will fit within the Pi's USB spec in terms of power - then find an available device that includes that drive or fit it in an enclosure yourself.

My feeling is that most current drives are a lot more power hungry than some of the early, slower and smaller ones. Many of the early ones were IDE just to complicate things further

abramq
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Re: Power for an external HDD

Mon Oct 06, 2014 7:53 am

Looking for producers specifications of portable disc, telling about power consumption is a way to nowhere. No one publish such data. I spend a lot of time looking for it, reading mass of pdf's.
Similar - I spent a lot of time looking for ANY post telling that someone succesfully connected disk in this way as I wrote. I really think about to sell my Pi...

fruit-uk
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Re: Power for an external HDD

Mon Oct 06, 2014 8:00 am

abramq wrote:Looking for producers specifications of portable disc, telling about power consumption is a way to nowhere. No one publish such data. I spend a lot of time looking for it, reading mass of pdf's.
You must be looking in the wrong places, a few keystrokes found one at http://www.seagate.com/www-content/supp ... -m8-ds.pdf, there will be many more out there.

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Re: Power for an external HDD

Mon Oct 06, 2014 8:01 am

fruit-uk wrote:My feeling is that most current drives are a lot more power hungry than some of the early, slower and smaller ones. Many of the early ones were IDE just to complicate things further
Why would IDE complicate things?

Now, if they were ST506 or ESDI... :lol:
(or like my first laptop which had a direct interface to the head and stepper motor - no electronics on the drive at all. The control circuitry was all on the mainboard)

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Re: Power for an external HDD

Mon Oct 06, 2014 8:20 am

rpdom wrote: ...
Why would IDE complicate things?
...
Now, if they were ST506 or ESDI... :lol:
(or like my first laptop which had a direct interface to the head and stepper motor - no electronics on the drive at all. The control circuitry was all on the mainboard)
+1, since it (originally) stood for Integrated Drive Electronics (which both PATA and SATA drives have). I came to the conclusion some time ago, after losing several, relatively low-power, USB-to-PATA(IDE) 2.5" drives in caddies using Y-cables that, unless they were to be used with a netbook or laptop****, which can provide the surge currents during spin-up, the only reliable way to use such is either by external power** or a good, expensive (at the time 2/3 the cost of a Pi) externally powered hub.
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** where possible, only one of the caddies had that option.
**** I even had one fail (degrade) when used with an NSLU2 USB NAS, designed, and provided with a good PSU for use with such.
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Re: Power for an external HDD

Mon Oct 06, 2014 8:33 am

rpdom wrote:
fruit-uk wrote:My feeling is that most current drives are a lot more power hungry than some of the early, slower and smaller ones. Many of the early ones were IDE just to complicate things further
Why would IDE complicate things?
I imagine that enclosures for IDE/PATA may be harder to come by these days - but I haven't looked lately

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PeterO
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Re: Power for an external HDD

Mon Oct 06, 2014 8:37 am

abramq wrote:So it looks like there is no really working external HDDs, powered by Pi usb port? I havn't find any post with succesful instalation... That's a pity - especially, that Pi B+ version has better power possibility...
Time to look for any Pi alternative ...
I've been running USB powered 2.5" 500Gb external drives on my Pi Bs since they first came out. Not had any toruble.

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abramq
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Re: Power for an external HDD

Mon Oct 06, 2014 8:38 am

fruit-uk wrote:
abramq wrote:Looking for producers specifications of portable disc, telling about power consumption is a way to nowhere. No one publish such data. I spend a lot of time looking for it, reading mass of pdf's.
You must be looking in the wrong places, a few keystrokes found one at http://www.seagate.com/www-content/supp ... -m8-ds.pdf, there will be many more out there.
Sorry, but this is not about external (portable) disc. The pdf you show is about a classic HDD, to be mounted inside laptop for example.
When you buy an external hard drive you don't know what model of disc is used inside. No one producer tells it. Or you have to destroy the case. Is there any takers to destroy his external HDD? ;-)

Of course I can buy one to check if it will work. And then buy anuother if not... and anyother... But it is expensive method, that's why I am writing here :-)

abramq
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Re: Power for an external HDD

Mon Oct 06, 2014 8:51 am

PeterO wrote:
abramq wrote:So it looks like there is no really working external HDDs, powered by Pi usb port? I havn't find any post with succesful instalation... That's a pity - especially, that Pi B+ version has better power possibility...
Time to look for any Pi alternative ...
I've been running USB powered 2.5" 500Gb external drives on my Pi Bs since they first came out. Not had any toruble.
PeterO
I have been looking for you so long! :-)
Please tell me exact model of disks you used, please!

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PeterO
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Re: Power for an external HDD

Mon Oct 06, 2014 8:53 am

abramq wrote: I have been looking for you so long! :-)
Please tell me exact model of disks you used, please!
Can't do that until I'm at home, but I can tell you they are both Seagate drives.
PeterO
Last edited by PeterO on Mon Oct 06, 2014 9:40 am, edited 1 time in total.
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Re: Power for an external HDD

Mon Oct 06, 2014 8:56 am

abramq wrote:
Sorry, but this is not about external (portable) disc. The pdf you show is about a classic HDD, to be mounted inside laptop for example.
When you buy an external hard drive you don't know what model of disc is used inside. No one producer tells it. Or you have to destroy the case. Is there any takers to destroy his external HDD? ;-)

Of course I can buy one to check if it will work. And then buy anuother if not... and anyother... But it is expensive method, that's why I am writing here :-)
You know that you can buy a enclosure to turn any classic HDD into a portable hard drive? Prices range from about £4 up to whatever you are willing to pay. Given a HDD enclosure and a known HDD you can make your own and know exactly what you are getting.
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Re: Power for an external HDD

Mon Oct 06, 2014 9:37 am

Same poster, same question:

According to USB-2.0 specification an USB device may draw up to 500 mA (USB-3.0 a bit more). If an 2.5 HD enclosure with USB 2.0 and no external power supply is sold, it should not use more.

The old B (this is a bit mixed up in this thread) was never made to supply 500 mA on its USB ports, The B+ delivers either 0.6 A or 1.2 A, dependent on a configuration setting, on all four USB ports together. This requires a good power supply with stable 5V at 2A (and a good power cable!).

With the high power setting enabled, the B+ should be able to feed two low power (100 mA) and two high power (500 mA) USB devices.

Connecting one USB 2.5 drive should always be possible, if all conditions are met. But don't use any of these crap "USB loaders"; use a good 2A switched power supply and a good cable. And use an USB-2.0 drive, not USB-3.0. If a drive is sold with an Y-cable, you can be sure, that it doesn't meet the standards, so don't use it.
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abramq
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Re: Power for an external HDD

Mon Oct 06, 2014 9:58 am

BMS Doug wrote:
abramq wrote:
Sorry, but this is not about external (portable) disc. The pdf you show is about a classic HDD, to be mounted inside laptop for example.
When you buy an external hard drive you don't know what model of disc is used inside. No one producer tells it. Or you have to destroy the case. Is there any takers to destroy his external HDD? ;-)

Of course I can buy one to check if it will work. And then buy anuother if not... and anyother... But it is expensive method, that's why I am writing here :-)
You know that you can buy a enclosure to turn any classic HDD into a portable hard drive? Prices range from about £4 up to whatever you are willing to pay. Given a HDD enclosure and a known HDD you can make your own and know exactly what you are getting.
Yes, of course I know... But in this situation I prefer factory made case, not home-made. More of it - there is an adapter inside - getting unknow amout of power ;-)

abramq
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Re: Power for an external HDD

Mon Oct 06, 2014 10:33 am

gkreidl wrote:Same poster, same question:

According to USB-2.0 specification an USB device may draw up to 500 mA (USB-3.0 a bit more). If an 2.5 HD enclosure with USB 2.0 and no external power supply is sold, it should not use more.

The old B (this is a bit mixed up in this thread) was never made to supply 500 mA on its USB ports, The B+ delivers either 0.6 A or 1.2 A, dependent on a configuration setting, on all four USB ports together. This requires a good power supply with stable 5V at 2A (and a good power cable!).

With the high power setting enabled, the B+ should be able to feed two low power (100 mA) and two high power (500 mA) USB devices.

Connecting one USB 2.5 drive should always be possible, if all conditions are met. But don't use any of these crap "USB loaders"; use a good 2A switched power supply and a good cable. And use an USB-2.0 drive, not USB-3.0. If a drive is sold with an Y-cable, you can be sure, that it doesn't meet the standards, so don't use it.
That sounds as an answer everybody want to get :-)
My model is B+, so with standard configuration I should get 0.6A as you described. I was making a little inwenstigetion before in standard 2.5 disks (used in laptops) and the best are using 0.7-0.9A. I gues, that external portable disks should use the same, as probably inside of them are similar models of disks. Then - usb standard giving 0.5A is not enought for them? Sounds strange - becasue as you wrote everbody work with portable disks...
On the other side I have found many posts from people with non-working portable disks together with Pi and no one post from some one who get success...

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