Joebacca
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Raspberry Pi Powered from AC USB Hub

Wed Jul 10, 2013 2:53 pm

Hi, I have been using a Raspberry Pi for some time now and have come up with a power question...

My current set up to power the Raspberry Pi is an old phone charger...

What I would like to do, is use the USB Hub that currently is connected to my Raspberry Pi for extra USB ports and also use it to power it. I am afraid that this creates some kind of loop that may damage the Raspberry Pi... Can someone let me know what they think?

Thanks

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Davespice
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Re: Raspberry Pi Powered from AC USB Hub

Wed Jul 10, 2013 3:00 pm

A few people have done this already, it should be fine. You can do one quick test though.
With your current set up, does the Pi stay on if you unplug the charger? If so then the Hub is back-powering the Pi already and you could even get away without adding another cable looping back to the Pi power socket.

ahstwin
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Re: Raspberry Pi Powered from AC USB Hub

Wed Jul 10, 2013 11:34 pm

^ spot on. I'm running mine straight off the usb hub which is powered through an ac connection.j just make sure the ac supply can provide sufficient current ( mine is about 1.5A max so you can also run a Wi-Fi adapter)

Joebacca
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Re: Raspberry Pi Powered from AC USB Hub

Thu Jul 11, 2013 4:03 am

No luck with the "back feeding" method. What exactly would cause this from not working? Was this possibly only working in older revisions?

Thanks for your replies though!

vpatron
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Re: Raspberry Pi Powered from AC USB Hub

Thu Jul 11, 2013 5:26 am

Hi Joe, you can hack your USB hub. I did that on mine and it works fine. Basically, you need to connect the VBUS (5 Volt) pin on the host connector and solder a wire to the 5 Volts from the adapter jack so it feeds voltage from the adapter to the USB host.

I can post a pic but your hub would be different. Hope that helps,

-Vince

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Hove
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Re: Raspberry Pi Powered from AC USB Hub

Thu Jul 11, 2013 6:03 am

Sorry, can't help with using one of the 'normal' type A USB ports to power the RPi from a USB hub, but I use a USB hub with a USB to micro USB cable, plugging that into the usual RPI power socket, and that's worked fine. This is the hub I use:

http://www.amazon.co.uk/gp/product/B006 ... OJNYBMLIQ3

Currently, my WiFi dongle and this are plugged into the RPi USB type A sockets, and the USB to micro-USB goes from the hub to the RPi power socket. Keyboard, mouse and DVD player are also attached to the hub.

This works find with no symptoms of feedback etc.
www.pistuffing.co.uk - Raspberry Pi and other stuffing!

Emexrulsier
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Re: Raspberry Pi Powered from AC USB Hub

Thu Oct 31, 2013 12:42 pm

I am power my pi (B) from the USB port on a screen. I am using hdmi output and a wireless dongle and all seems fine.

donal1506
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Re: Raspberry Pi Powered from AC USB Hub

Wed Nov 13, 2013 11:55 pm

I'm using a Belkin F5U701-BLK usb hub plugged into standard usb port on the Pi
and no micro usb cable and works fine so far.

bersgurs
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Re: Raspberry Pi Powered from AC USB Hub

Sun Nov 17, 2013 1:20 pm

Lets assume that i connected my raspberry and usb hub to a power source with a dual usb charger(outputs are 1A and 2.1A) how can i connect my pi and usb hub to each other? Can i use a simple male to male to usb cable for this?

My usb hub:

Image
Image

MoosePi
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Re: Raspberry Pi Powered from AC USB Hub

Sun Nov 17, 2013 1:30 pm

I use this with a standard USB to Micro Cable, no back feeding:

Belkin Hi-Speed USB 2.0 4-Port Hub F5U234 USB 2.0 4-Port 5 V - 500 mA per Port Verified

http://elinux.org/RPi_Powered_USB_Hubs
Pi Forum Search and Google yields answers to many questions

khisraw
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Re: Raspberry Pi Powered from AC USB Hub

Sun Nov 17, 2013 3:07 pm

HI Guys,
I bought a cheap USB hub to connect peripherals to the PI. It seems it doesnt connect. The hub works fine if I test it on my laptop but if I connect it to PI, at the start it say "Cant not reset port 4" but no mouse or keyboard gets connected.
If there was problem with hub, it wouldnt work with the laptop so why it dosnt work the PI?

Any help or tip please????

Thanks

bersgurs
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Re: Raspberry Pi Powered from AC USB Hub

Sun Nov 17, 2013 11:41 pm

khisraw wrote:HI Guys,
I bought a cheap USB hub to connect peripherals to the PI. It seems it doesnt connect. The hub works fine if I test it on my laptop but if I connect it to PI, at the start it say "Cant not reset port 4" but no mouse or keyboard gets connected.
If there was problem with hub, it wouldnt work with the laptop so why it dosnt work the PI?



Any help or tip please????

Thanks
Pi's usb output power is not high as bigger computers.Pi can only output 140 mA to peripherals while bigger devices can provide 500mA per port and even 900mA by usb 3.0

pontypool
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Re: Raspberry Pi Powered from AC USB Hub

Mon Apr 14, 2014 10:42 am

Hove wrote:Sorry, can't help with using one of the 'normal' type A USB ports to power the RPi from a USB hub, but I use a USB hub with a USB to micro USB cable, plugging that into the usual RPI power socket, and that's worked fine. This is the hub I use:

http://www.amazon.co.uk/gp/product/B006 ... OJNYBMLIQ3

Currently, my WiFi dongle and this are plugged into the RPi USB type A sockets, and the USB to micro-USB goes from the hub to the RPi power socket. Keyboard, mouse and DVD player are also attached to the hub.

This works find with no symptoms of feedback etc.

Excuse me chipping in but you mean that hub you posted provides sufficient power to the raspberry pi?
if you plug in say... a wi fi adaptor into the hub will that work properly? what about a usb pen drive and would the speed be ok because it's going through a hub?

How can we tell if any hub is capable of providing power to the raspberry pi, other than of course unplugging the raspberry pi and seeing if it still remains powered ? ( as someone else suggested testing in this thread ) I suspect anything that has usb to micro usb will power it, can anyone confirm?

my brother used a hub and had problems with an external hard drive cutting out... apparently if you have 10 ports on a usb2 hub the full speed of 1 single usb port is shared beteween all 10 ports of that hub. i have always been weary of hubs because of that, i feel that the devices are going to operate sub standard.

fruitoftheloom
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Re: Raspberry Pi Powered from AC USB Hub

Mon Apr 14, 2014 12:10 pm

Excuse me chipping in but you mean that hub you posted provides sufficient power to the raspberry pi?
if you plug in say... a wi fi adaptor into the hub will that work properly? what about a usb pen drive and would the speed be ok because it's going through a hub?

How can we tell if any hub is capable of providing power to the raspberry pi, other than of course unplugging the raspberry pi and seeing if it still remains powered ? ( as someone else suggested testing in this thread ) I suspect anything that has usb to micro usb will power it, can anyone confirm?

my brother used a hub and had problems with an external hard drive cutting out... apparently if you have 10 ports on a usb2 hub the full speed of 1 single usb port is shared beteween all 10 ports of that hub. i have always been weary of hubs because of that, i feel that the devices are going to operate sub standard.
Yes I power my Pi from a USB Hub, but I do not use external drives....

http://www.raspberrypi.org/forums/viewt ... 91&t=74431

The reason for choosing this hub was lack of back powering as well as reliably offering stable voltage in any information found on the www.......bought used for £10.00
Last edited by fruitoftheloom on Mon Apr 14, 2014 3:45 pm, edited 1 time in total.
Retired disgracefully.....
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Tarcas
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Re: Raspberry Pi Powered from AC USB Hub

Mon Apr 14, 2014 3:39 pm

How can we tell if any hub is capable of providing power to the raspberry pi, other than of course unplugging the raspberry pi and seeing if it still remains powered ? ( as someone else suggested testing in this thread ) I suspect anything that has usb to micro usb will power it, can anyone confirm?
It all depends on the wiring. Really, a powered USB hub shouldn't provide power to the host port, but it seems that most of them do. The easiest way to test is to just plug the Pi into the powered hub and see if it turns on. Alternately, you could open up the hub and see if the red +5v wire to the host device is connected to the power bus. If you don't want it to backpower the Pi, just clip or desolder this wire. You can always plug a microUSB cable into any of the other ports and power the Pi through the normal port if you change your mind.

darkform
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Re: Raspberry Pi Powered from AC USB Hub

Fri Apr 25, 2014 12:44 am

Hi all

I've examined these USB hub issues a lot and read many articles/forums about it. Also tried various USB hubs with my Pi. Some were powered, some were not and some of them with/without a no back power function.

here are my suggestions;

First of all, we must have a good quality, at least a real 1A power adaptor for the Pi itself. Most of the hub problems comes in if you do not feed your pi with a good power source. I've experienced different stability and boot up problems when I use different (cheap and expensive ones, all 5v 1A) power adaptors for the pi, with exactly the same pi & hardware setup (same usb hub, same sd card, same os, same usb devices.). Just power adaptor changes and boom, system loses stability like usb devices connected to the hub not working.

With 1 X logitech wireless keyboard & mouse, 1 XTP link wifi adaptor, 1 X external HDDs, 1 X usb light and 1 X 32 gb Usb stick;
I've tried using pi with an original 5v/1A iphone adaptor and it works good.
I've also tried original samsung galaxy note 2 5c/2A and it also works great. So main problem here is not he HUB itself I guess, but the power adaptor/s.

Secondly, we have to use a powered hub for sure, especially if we are going to use many usb connections like wireless keyboard, mouse, wifi adaptor, HDDs etc.. That is also a must.

As it comes to back power issues; I've found out that the most important element in these backpower issues is not the hub itself, but the power source of the pi as well as the power source of the Hub. I mean power adaptors. If you have a good quality power source (adaptor) for your pi with at least 1A (I mean real output, stable and good quality 1A) or more, your pi will work very very stable rather it's connected to a powered hub with a back power functionality or no backpower. Backpower won't effect your pi's power stability in most cases. I've used 4 different, cheap powered hubs, all made in china and had no problems with any of them on long terms. All still working smoothly.

After some research, I've found out that the best chip around manifactured and used in powered USB Hubs is so cheap that, most of the manufacturers use the same one for their powered USB hub products, even if it's a cheap china made model or a quality one like a Logitech or Microsoft. Both use the same chip in general. What makes the difference is the power adaptor. If you buy a cheap powered USB hub, it's power adaptor coming out of the box may not sustain the power that the hub needs. So, I also recommend to replace the power adaptor of the cheap powered hubs with quality ones.

To summerize what I can suggest is;
1. Use/buy quality adaptors, both for the Pi and the HUB.
2. If you have a digital meter, check their real rates/outputs. It's easy.
3. Try to keep it at least 1A when you are buying a (good) adaptor for the Pi.
4. You may go even over 2A as you add more usb devices to your Pi/Hub. Remember this if system gets unstable, USB devices gets suddenly disconnected or they become unresponsive randomly.
5. When buying a quality adaptor for the powered USB Hub, check the rates of the original one. Buy with the exact same voltage. But you will definitly want to buy one with a higher amper value, like 2A. Sooner or later, you'll need higher Ampers as you start to connect more and more usb devices.
6. If your powered USB hub has backpower function, try to power on both the Pi and Hub at the same exact time. This will highly reduce USB device errors. (like bad disk, mount/umount and safely remove errors) You may want to use a simple plug with a switch for that. Just turn the swith on and Pi & The Hub will power on at the same time. This will also keep fragile micro usb power port and usb ports of the pi safe.
7. If you are using 3.5' HDDs, do not try to power it from The Pi, nor from powered USB hub. Power it directy from another source. They consume very high power which will probably effect the stability and power balance of the system.
8. Rarely, backpower may create problems. But in most cases, the problem is the power adaptors. Buy a good one/s!

Tarcas
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Re: Raspberry Pi Powered from AC USB Hub

Fri Apr 25, 2014 2:30 am

Thanks for that, Darkform. I've long said that power supplies are the most overlooked component when building a computer, and that issue seems to be amplified with the Pi, since you're not buying a "power supply" but using a USB charger, and those seem to be built to rather questionable specs, as you have noticed. Even though the Model B is supposed to only take about 500mA of power, in order to power it reliably, we need to use a supply rated at double that, minimum.

In your point #6, you talked about the powered hubs that provide backpower and that you found it best to power it and the pi simultaneously. What testing did you do with powering the pi only through backpower? I was under the impression that if your hub backpowers your Pi, you should not also power it through the microUSB.

In point #5, you mention matching the voltage. Voltage should always be 5v for standard USB. Did you come across any powered USB hubs with different supply voltages, and if so do you know why? (I could imagine a supplier stepping down 6v or more inside the hub to 5v for various reasons, or possibly accounting for internal resistance with something like a 5.25v supply, but I have not seen either of these firsthand.)

fruitoftheloom
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Re: Raspberry Pi Powered from AC USB Hub

Fri Apr 25, 2014 8:03 am

*Back Powering by-passes the polyfuse, that is why I junked a couple of Cheap Chinese Hubs.

Regards Hard Drives 3.5" also use a mains powered caddy

2.5" in a USB Cadddy with two USB leads (dsta & power), experimented and found it better if powered the caddy from a phone charger.....
Retired disgracefully.....
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pontypool
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Re: Raspberry Pi Powered from AC USB Hub

Fri Apr 25, 2014 3:31 pm

darkform wrote:Hi all

I've examined these USB hub issues a lot and read many articles/forums about it. Also tried various USB hubs with my Pi. Some were powered, some were not and some of them with/without a no back power function.

here are my suggestions;

First of all, we must have a good quality, at least a real 1A power adaptor for the Pi itself. Most of the hub problems comes in if you do not feed your pi with a good power source. I've experienced different stability and boot up problems when I use different (cheap and expensive ones, all 5v 1A) power adaptors for the pi, with exactly the same pi & hardware setup (same usb hub, same sd card, same os, same usb devices.). Just power adaptor changes and boom, system loses stability like usb devices connected to the hub not working.

With 1 X logitech wireless keyboard & mouse, 1 XTP link wifi adaptor, 1 X external HDDs, 1 X usb light and 1 X 32 gb Usb stick;
I've tried using pi with an original 5v/1A iphone adaptor and it works good.
I've also tried original samsung galaxy note 2 5c/2A and it also works great. So main problem here is not he HUB itself I guess, but the power adaptor/s.

Secondly, we have to use a powered hub for sure, especially if we are going to use many usb connections like wireless keyboard, mouse, wifi adaptor, HDDs etc.. That is also a must.

As it comes to back power issues; I've found out that the most important element in these backpower issues is not the hub itself, but the power source of the pi as well as the power source of the Hub. I mean power adaptors. If you have a good quality power source (adaptor) for your pi with at least 1A (I mean real output, stable and good quality 1A) or more, your pi will work very very stable rather it's connected to a powered hub with a back power functionality or no backpower. Backpower won't effect your pi's power stability in most cases. I've used 4 different, cheap powered hubs, all made in china and had no problems with any of them on long terms. All still working smoothly.

After some research, I've found out that the best chip around manifactured and used in powered USB Hubs is so cheap that, most of the manufacturers use the same one for their powered USB hub products, even if it's a cheap china made model or a quality one like a Logitech or Microsoft. Both use the same chip in general. What makes the difference is the power adaptor. If you buy a cheap powered USB hub, it's power adaptor coming out of the box may not sustain the power that the hub needs. So, I also recommend to replace the power adaptor of the cheap powered hubs with quality ones.

To summerize what I can suggest is;
1. Use/buy quality adaptors, both for the Pi and the HUB.
2. If you have a digital meter, check their real rates/outputs. It's easy.
3. Try to keep it at least 1A when you are buying a (good) adaptor for the Pi.
4. You may go even over 2A as you add more usb devices to your Pi/Hub. Remember this if system gets unstable, USB devices gets suddenly disconnected or they become unresponsive randomly.
5. When buying a quality adaptor for the powered USB Hub, check the rates of the original one. Buy with the exact same voltage. But you will definitly want to buy one with a higher amper value, like 2A. Sooner or later, you'll need higher Ampers as you start to connect more and more usb devices.
6. If your powered USB hub has backpower function, try to power on both the Pi and Hub at the same exact time. This will highly reduce USB device errors. (like bad disk, mount/umount and safely remove errors) You may want to use a simple plug with a switch for that. Just turn the swith on and Pi & The Hub will power on at the same time. This will also keep fragile micro usb power port and usb ports of the pi safe.
7. If you are using 3.5' HDDs, do not try to power it from The Pi, nor from powered USB hub. Power it directy from another source. They consume very high power which will probably effect the stability and power balance of the system.
8. Rarely, backpower may create problems. But in most cases, the problem is the power adaptors. Buy a good one/s!
why do you need an adaptor for the pi AND the hub? this hub USB2-HUB-AG7-UK is recommended, I purchased one myself and it runs the pi-b 2 pen drives, a mini wireless keyboard with touchpad, wifi internet with no problems what so ever, i've left it on as a server to share torrent files non stop.

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JamesChan
Posts: 4
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Re: Raspberry Pi Powered from AC USB Hub

Sun Jun 15, 2014 7:08 am

How about the uugear USB HUB with AC input http://www.uugear.com 8-) 8-)
DSC_0115-6.jpg
uugear usb hub with ac input
DSC_0115-6.jpg (61.55 KiB) Viewed 20042 times

Mudit
Posts: 12
Joined: Sat Jan 16, 2016 10:14 am

Re: Raspberry Pi Powered from AC USB Hub

Thu Jun 09, 2016 12:59 pm

I am facing the exact same problem,have u figured the solution?

drgeoff
Posts: 9924
Joined: Wed Jan 25, 2012 6:39 pm

Re: Raspberry Pi Powered from AC USB Hub

Thu Jun 09, 2016 2:05 pm

Mudit wrote:I am facing the exact same problem,have u figured the solution?
It isn't clear, at least to me, what problem you are facing.

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