Power from powered USB hub?


22 posts
by CyCaboose » Thu May 31, 2012 10:32 am
Hi guys,

I've come to realise I'll need a powered USB hub to power my portable HDD, so I am about to get one. Thing is, I'd really rather not take up 2 power sockets just to run the Raspberry Pi (3 inc tv), especially since it uses so little power.

Is it possible to power the Raspberry Pi off one of the ports from a powered USB hub?

Thanks,
User avatar
Posts: 8
Joined: Thu May 31, 2012 10:27 am
Location: Dublin, Ireland
by bredman » Thu May 31, 2012 10:53 am
Yes, this is what I do and a lot of people recommend it.
Posts: 1413
Joined: Tue Jan 17, 2012 2:38 pm
by CyCaboose » Thu May 31, 2012 10:56 am
Will any powered USB hub do it, or is there anything I need to look out for regarding specifics with output power on each port?
User avatar
Posts: 8
Joined: Thu May 31, 2012 10:27 am
Location: Dublin, Ireland
by JetsetWilly » Thu May 31, 2012 3:06 pm
Im running the el cheapo 7 Port powered hub from Ebay and it works fine
Posts: 6
Joined: Mon May 28, 2012 5:26 pm
by SN » Thu May 31, 2012 3:28 pm
Me too - the Pluscomm one BUT IMPORTANTLY with the 3.5A PSU

And today... after 8 days of faffing I finally finally have a combo that is working solidly for me and the key is the use of the Powered Hub!

And here is my setup:
Image

R2 Raspberry Pi
Raspi Upper USB - Belkin F5D7050 USB Wireless Adaptor
Raspi Lower USB - USB A to B Cable to Powered USB Hub

7 Port Pluscomm USB Hub.
Mains Power ONLY to USB Hub
USB Hub Port F1 - USB Optical Mouse (Dell/Logitech)
USB Hub Port F2 - USB Keyboard (Trust super cheapo)
USB Hub Port F4 - USB to MicroUsb Power Cable to Raspi Power Socket
USB Hub Port F5 - USB Maplins Robotic Arm 8-)

No other combo works for me, even swapping over devices on raspi USB ports kills it
The key was that TP1/TP2 was reading about 5.1V with the USB Hub Powering it whereas
anything else I tried direct was only getting to about 4.9v (before adding wireless)

A couple more screenshots showing Midori accessing these forums AND a website over the internet which is actually hosted by my R2 raspi
Image Image
Steve N – binatone mk4->intellivision->zx81->spectrum->cbm64->cpc6128->520stfm->pc->raspi ?
User avatar
Posts: 1008
Joined: Mon Feb 13, 2012 8:06 pm
Location: Romiley, UK
by canyon » Thu May 31, 2012 4:46 pm
[quote="SN"]Me too - the Pluscomm one BUT IMPORTANTLY with the 3.5A PSU

I second that, especially the bit about the 3.5A PSU.

I am also using short cables (30cm), which makes it all neater: But also minimises voltage loss in the USB to Pi power cable:
A 30cm elbow micro-USB to USB-A for power - makes it easier to route the power cable to the rear.
A 30cm USB-A to USB-B for data.
An elbow HDMI adaptor - makes it easier to route the HDMI cable to the rear.
The Raspberry Pi hangs on the wall at the left of my desk, with the Pluscomm USB hub below it, on its stand.
The power and USB from the hub to the Raspberry Pi, and the power from the mains to the hub are on the right, as in the photo. An old 80GB USB powered HDD is underneath, connected to the 2nd USB port on the right end of the hub.
The sockets on the 'front' (left) of the hub are free for peripherals: at present a USB stick and a small wireless dongle for the keyboard/mouse.
As soon as it arrives, I'm going to replace the HDD with a 16GB USB stick and hopefully have the rootfs and swap on that, just leaving /boot on the SD card.
Attachments
P1010577-small.jpg
P1010577-small.jpg (55.71 KiB) Viewed 15427 times
Posts: 31
Joined: Sun Jan 29, 2012 9:47 am
by mahjongg » Thu May 31, 2012 5:08 pm
sometimes the current output of a single HUB port is limited (say by a 500mA fuse) to a value less than what the PI needs, in that case a special "Y cable" could be used that draws current from two hub ports.
User avatar
Forum Moderator
Forum Moderator
Posts: 5700
Joined: Sun Mar 11, 2012 12:19 am
by hackery21 » Fri Jun 01, 2012 2:37 am
So I can use a powered hub as a hub for the pi AND also power the pi with it?
Posts: 56
Joined: Wed Apr 18, 2012 9:11 pm
by antiloquax » Fri Jun 01, 2012 2:37 pm
Yes, this is what I am doing also.
I have a cheapo Kingston 4-usb hub and it's working well to power and be the hub for, my RPi.
Posts: 406
Joined: Sun Nov 20, 2011 11:37 am
by SN » Fri Jun 01, 2012 3:23 pm
hackery21 wrote:So I can use a powered hub as a hub for the pi AND also power the pi with it?

Saves on the requirement for mains plugs too! Just make sure you get a PSU for the Hub thatis beefy enough - I'm using the £6 ebay pluscom hub with 3A PSU, works a treat
Steve N – binatone mk4->intellivision->zx81->spectrum->cbm64->cpc6128->520stfm->pc->raspi ?
User avatar
Posts: 1008
Joined: Mon Feb 13, 2012 8:06 pm
Location: Romiley, UK
by nabla » Fri Jun 01, 2012 4:25 pm
Hi,

I'm using a belkin 7-port powered usb hub (2.5A adapter). It first seemed weird to me when I connected the data cable of the hub to my rpi and the PWR light came on!
This interferes with the board so much that the internet becomes so slow that it's unusable.

Did anyone else come to this problem? Any ideas on how should I fix this? Should I put a diode somewhere?
Posts: 12
Joined: Tue May 29, 2012 10:00 pm
by mahjongg » Fri Jun 01, 2012 5:45 pm
if you also power the PI from the same hub there is nothing you have to do further.
User avatar
Forum Moderator
Forum Moderator
Posts: 5700
Joined: Sun Mar 11, 2012 12:19 am
by nabla » Fri Jun 01, 2012 6:12 pm
I do, but it still causes problems.

The simplest way would be to sacrifice one USB cable and cut the power line?
Posts: 12
Joined: Tue May 29, 2012 10:00 pm
by domdoran » Sat Jun 02, 2012 9:54 pm
I noticed that when connecting the USB data cable from the powered hub that the pi powers on without even connecting the micro USB power input to the pi. Is this how you guys are running, or are you also connecting the micro USB from the hub to the power input of the Pi?
Posts: 2
Joined: Thu May 31, 2012 10:55 pm
by mahjongg » Sat Jun 02, 2012 10:22 pm
domdoran wrote:I noticed that when connecting the USB data cable from the powered hub that the pi powers on without even connecting the micro USB power input to the pi. Is this how you guys are running, or are you also connecting the micro USB from the hub to the power input of the Pi?

No, this connection is fused on the PI with a 140mA fuse, so you also need to use the micro USB power cable and plug it into the hub.
User avatar
Forum Moderator
Forum Moderator
Posts: 5700
Joined: Sun Mar 11, 2012 12:19 am
by domdoran » Sat Jun 02, 2012 11:25 pm
Thanks! I'm so paranoid about running too hot. I don't want to fry this thing.
Posts: 2
Joined: Thu May 31, 2012 10:55 pm
by ScoobyDoo » Sun Jun 03, 2012 8:05 am
I've tried this method using a pluscom 7 port hub with bad results.
I've powered the pi from the hub using the micro USB cable.

The pi boots ok but I get lots of USB reset errors, 500ma from the hub to the pi just isn't enough power.
Removed the hub totally , used a Belkin 1amp USB adapter to power the pi and it runs rock solid with no errors.
It's very hit and miss with hubs but after trying 3 different ones and getting different results with each I'm staying well clear of them.
User avatar
Posts: 65
Joined: Wed Apr 04, 2012 2:52 pm
Location: Staffordshire, UK
by itimpi » Sun Jun 03, 2012 8:10 am
Do you have a USB Y cable? These are often used with 2.5" disk drives to enable them to take power from 2 USB ports in parallel. It might help here at the cost of using an additional USB port.
Posts: 1035
Joined: Sun Sep 25, 2011 11:44 am
Location: Potters Bar, United Kingdom
by CourtDweller » Sun Jun 03, 2012 11:24 am
So just to check, if I did get a powered USB hub that conforms to spec (each port doing 500mA) when my Pi arrives (my place in the queue arrived last week), would using a Y cable fairly much guarantee enough power? I'd be using the hub for all devices, so if the Pi is drawing in 2x500mA it be enough right?
Posts: 1
Joined: Sun Jun 03, 2012 5:45 am
by Pi_Man » Sun Jun 03, 2012 8:29 pm
Can you tell me where you bought your micro usb to twin usb cable.

Thanks


canyon wrote:
SN wrote:Me too - the Pluscomm one BUT IMPORTANTLY with the 3.5A PSU

I second that, especially the bit about the 3.5A PSU.

I am also using short cables (30cm), which makes it all neater: But also minimises voltage loss in the USB to Pi power cable:
A 30cm elbow micro-USB to USB-A for power - makes it easier to route the power cable to the rear.
A 30cm USB-A to USB-B for data.
An elbow HDMI adaptor - makes it easier to route the HDMI cable to the rear.
The Raspberry Pi hangs on the wall at the left of my desk, with the Pluscomm USB hub below it, on its stand.
The power and USB from the hub to the Raspberry Pi, and the power from the mains to the hub are on the right, as in the photo. An old 80GB USB powered HDD is underneath, connected to the 2nd USB port on the right end of the hub.
The sockets on the 'front' (left) of the hub are free for peripherals: at present a USB stick and a small wireless dongle for the keyboard/mouse.
As soon as it arrives, I'm going to replace the HDD with a 16GB USB stick and hopefully have the rootfs and swap on that, just leaving /boot on the SD card.
Posts: 2
Joined: Sun Jun 03, 2012 8:24 pm
by canyon » Mon Jun 04, 2012 9:14 am
Pi_Man:
I got it from Amazon: http://www.amazon.co.uk/StarTech-feet-C ... f_ee_p_t_1.
I also purchased one of these, as it is neater: http://www.amazon.co.uk/gp/product/B004 ... 02_s00_i00.

I've come to the conclusion that the cable is more important than it is given credit for.
Voltages are measured on TP1.

The RPi has a Sandisk 16GB usb stick in one USB port, composite output and the USB hub in the other.

Using the RPi powered from my Pluscom 7 port hub. Note that the hub has a 3.5A PSU - I've opened up the hub and found that the 5V is directly connected to all of the ports, so any port can supply up to the full 3.5A:

Startech double USB cable, both ports connected: 4.98V
Startech double USB cable, one ports connected: 4.97V
Startech single elbow USB cable: 4.91V
1.8m USB cable from my Sony Reader: 4.74V
1.2m USB cable from my ZTE blade mobile phone charger: 4.85V

I've started, so I'll finish:
ZTE Blade mobile charger with its 1.2M cable: 4.94V
ZTE Blade mobile charger with Sony 1.8M cable: 4.87V
ZTE Blade mobile charger with Startech single elbow USB cable: 5.08V

'Sainsburys' Masterplug surge-protected double USB mains adaptor with Startech single elbow USB cable: 4.79V.

I could do more combinations, but my desk is now getting a bit chaotic- I think this gives you a flavour!
Posts: 31
Joined: Sun Jan 29, 2012 9:47 am
by Pi_Man » Mon Jun 04, 2012 6:21 pm
Many thanks for your detailed reply.

I would appreciate any further postings you feel relevant.

Regards.
Posts: 2
Joined: Sun Jun 03, 2012 8:24 pm