Bloodsbane
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Quick question

Fri Oct 03, 2014 1:10 pm

Hey, sorry if this is wrong forum and should not be posted under off topic but i am going to buy a raspberry pi b+ and i got 3 questions.

Can i power it from a usb hub from my computer?


how well do ps1 run?

and how well does xbmc run?

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liz
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Re: Quick question

Fri Oct 03, 2014 4:14 pm

I've moved this to Beginners - for obvious reasons!
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W. H. Heydt
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Re: Quick question

Fri Oct 03, 2014 6:27 pm

Bloodsbane wrote:Hey, sorry if this is wrong forum and should not be posted under off topic but i am going to buy a raspberry pi b+ and i got 3 questions.

Can i power it from a usb hub from my computer?
Yes, but....

The B+ should run okay powered from your computer's USB port, but it may not be able to provide power to much in the way of USB devices connected to its own USB ports. It's better to get the Pi its own power supply. To take full advantage of a B+, get a good quality power supply rated for at least 2A...and use good quality USB to microUSB cables to connect the power to the Pi.

lazarus78
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Re: Quick question

Fri Oct 03, 2014 6:33 pm

I use a powered USB3 hub to power 2 Pis, since USB3 standard called for 1000mA output. The Pis are hooked to TVs, complete with the fixings of network cables and a USB keyboard/mouse. They have worked flawlessly for over 2 months so far.

W. H. Heydt
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Re: Quick question

Fri Oct 03, 2014 6:53 pm

lazarus78 wrote:I use a powered USB3 hub to power 2 Pis, since USB3 standard called for 1000mA output. The Pis are hooked to TVs, complete with the fixings of network cables and a USB keyboard/mouse. They have worked flawlessly for over 2 months so far.
This assumes USB 3.0 ports (and, by the way, so far as I know, the spec is 900mA, not 1A). The far more common USB 2.0 port specify 500mA, but allow for special connections that provide more. Even then, don't be too sure that you'll get full voltage at the rated current. On a desktop computer, I watched a USB 2 port provide a bit over 900mA, but the voltage dropped below 4.5v.

Bloodsbane
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Re: Quick question

Fri Oct 03, 2014 7:09 pm

W. H. Heydt wrote:
Bloodsbane wrote:Hey, sorry if this is wrong forum and should not be posted under off topic but i am going to buy a raspberry pi b+ and i got 3 questions.

Can i power it from a usb hub from my computer?
Yes, but....

The B+ should run okay powered from your computer's USB port, but it may not be able to provide power to much in the way of USB devices connected to its own USB ports. It's better to get the Pi its own power supply. To take full advantage of a B+, get a good quality power supply rated for at least 2A...and use good quality USB to microUSB cables to connect the power to the Pi.
Ah okie, is it only important to be a supply with 2A?

W. H. Heydt
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Re: Quick question

Fri Oct 03, 2014 10:10 pm

Bloodsbane wrote:
W. H. Heydt wrote:
Bloodsbane wrote:Hey, sorry if this is wrong forum and should not be posted under off topic but i am going to buy a raspberry pi b+ and i got 3 questions.

Can i power it from a usb hub from my computer?
Yes, but....

The B+ should run okay powered from your computer's USB port, but it may not be able to provide power to much in the way of USB devices connected to its own USB ports. It's better to get the Pi its own power supply. To take full advantage of a B+, get a good quality power supply rated for at least 2A...and use good quality USB to microUSB cables to connect the power to the Pi.
Ah okie, is it only important to be a supply with 2A?
If you use a 2A supply, you won't have to worry about what you connect to it (so long as you stay within the limits of the Pis power system). The Pi itself is going to need around 300mA (give or take). The default settings provide 600mA for the USB devices. You can set an option to increase the available USB current to 1.2A. The Pi has a protective polyfuse that trips at around 2A, so a power supply rated much more than that is wasted effort...the Pi will never use more current.

The thing to watch for is that not all things labeled as "power supplies" really are and on all to many of them, if you try to draw the rated current, the voltage will drop to unacceptable levels.

As you can see, the Raspberry Pi is a *very* educational device. Ask question about it, and you'll get an education in topics you didn't anticipate.

Dwardo
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Re: Quick question

Sat Oct 04, 2014 2:40 am

W. H. Heydt wrote: The thing to watch for is that not all things labeled as "power supplies" really are and on all to many of them, if you try to draw the rated current, the voltage will drop to unacceptable levels.
I'm interested in what you mean by this, is there anyway to tell beforehand?

Was about to buy one myself, was looking at this one.

Joe Schmoe
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Re: Quick question

Sat Oct 04, 2014 4:39 am

W. H. Heydt wrote: The B+ should run okay powered from your computer's USB port, but it may not be able to provide power to much in the way of USB devices connected to its own USB ports. It's better to get the Pi its own power supply. To take full advantage of a B+, get a good quality power supply rated for at least 2A...and use good quality USB to microUSB cables to connect the power to the Pi.
Note that OP wrote:
Bloodsbane wrote: Can i power it from a usb hub emphasis mine from my computer?
Which is unclear. I.e., it is not clear what "a usb hub from my computer" means, but I'm assuming it means a USB hub (and that the "from my computer" part can more or less be ignored. Maybe he means "from his computer spare parts bin"…)

The point of this is that if you use a powered hub, then (IME), you are not limited by the 500 mA limit in the USB 2.0 spec. Yes, technically/in-theory, a hub is only required to supply up to 500 mA per port, but in practice most good hubs ignore this and allow any port to draw what it wants (up to the limit of the power supply of course). This is all IME, of course, and if you have a hub that doesn't work like this, well, that's not my concern. The point is that if you have a powered hub with a, say, 3A power supply, you should be fine powering the Pi from it (as long as your cable is good).
And some folks need to stop being fanboys and see the forest behind the trees.

(One of the best lines I've seen on this board lately)

Bloodsbane
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Re: Quick question

Sat Oct 04, 2014 8:40 pm

Joe Schmoe wrote:
W. H. Heydt wrote: The B+ should run okay powered from your computer's USB port, but it may not be able to provide power to much in the way of USB devices connected to its own USB ports. It's better to get the Pi its own power supply. To take full advantage of a B+, get a good quality power supply rated for at least 2A...and use good quality USB to microUSB cables to connect the power to the Pi.
Note that OP wrote:
Bloodsbane wrote: Can i power it from a usb hub emphasis mine from my computer?
Which is unclear. I.e., it is not clear what "a usb hub from my computer" means, but I'm assuming it means a USB hub (and that the "from my computer" part can more or less be ignored. Maybe he means "from his computer spare parts bin"…)

The point of this is that if you use a powered hub, then (IME), you are not limited by the 500 mA limit in the USB 2.0 spec. Yes, technically/in-theory, a hub is only required to supply up to 500 mA per port, but in practice most good hubs ignore this and allow any port to draw what it wants (up to the limit of the power supply of course). This is all IME, of course, and if you have a hub that doesn't work like this, well, that's not my concern. The point is that if you have a powered hub with a, say, 3A power supply, you should be fine powering the Pi from it (as long as your cable is good).
sorry for being unclear but i got both USB 2 and 3

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DougieLawson
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Re: Quick question

Sat Oct 04, 2014 8:55 pm

Put the USB 3.0 stuff away in a cupboard. Your RPi has NO support for USB 3.0 devices unless they can run in USB 2.0 mode.
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W. H. Heydt
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Re: Quick question

Sat Oct 04, 2014 9:19 pm

DougieLawson wrote:Put the USB 3.0 stuff away in a cupboard. Your RPi has NO support for USB 3.0 devices unless they can run in USB 2.0 mode.
As a power supply for a Pi, a USB 3 hub would be just fine (assuming the hub actually meets the USB 3 specifications) since the spec calls for up to 900mA per port. Of course, that implies that the power supply for the hub should exceed 3.6A for a 4-port hub. I have seen far too many "powered USB hubs" that come with power supplies that are rated way below spec, including one that MCM at one point recommended early on for the Pi. I called them on that and they corrected their listings.

Caveat emptor is still very much a thing to remember in this field.

Likalnik
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Re: Quick question

Sun Oct 05, 2014 9:38 pm

Hi guys...one quick question...what is the maximum speed download for raspberry...I used it for movies..deluge client...and I get only 2,5Mib/s...but on utorrent I get more than 6Mib/s...any idea why??

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