sandytrisquirrelon
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Re: What should I know about USB hubs beyond: a high quality is good!

Fri Jan 20, 2012 10:35 pm

Does anybody know where to get independent and “undertiteled techi  slang advices” on: What you should know about USB hubs?

As a complete newbee I was just googling for high quality USB hub to get some basic know how on the component to accomplish Raspi with, once it will be out. I reckon within 2 weeks I will me smart enough and have collected enough  background to purchase on my own via Conrad Electronics for e.g. and would not even need to go to a retailer’s shop to ask for advice.

This maybe has been a bit underestimating the situation as I just found out that a guy in a forum had searched the internet 3 weeks just to find the right USB hub (I guess if I do that for any component it will take me a 4x3 weeks to have everything I need not to mention the second step all the installations and the operation sys. install)
Anyway, what I found so far was a forum discussion on July 31st, 2007, 11:55 – unfortunately I did not manage to find something newer nor do I have a clue which journal or web-portal offers quality reviews (independent ones) on USB hubs.
http://terrywhite.com/techblog.....chives/235 USB hubs - Who makes the best one?
was a bit like ranging between heroization and demonizing of Belikin, though the critic had been focusing on 2 certain “quality” Belkin USB hubs:
Belkin Hi-Speed USB 2.0 7-Port Hub Part # F5U237v1
Belkin 7 Port High Speed USB 2.0 Mobile Hub – F5U701-BLK

Here you can read a quite alerting statement: Phantom says: October 6, 2008 at 10:47 pm
•    Belkin Hi-Speed USB 2.0 7-Port Hub Part # F5U237v1.
(…)Reviews on the product warned that the unit would get too hot and shut down when more than two devices were attached. (…)
•    Belkin Hi-Speed USB 2.0 7-Port Hub Part # F5U237v1
(…) is junk and may damage your computer.(…)

Eventually,  as a positive alternative the USB GEAR is appearing.

As I am a complete newbee I thought, well first of all this was in 2007 and Belkin  wouldn’t exist any longer if they were delivering such an e-Waste,  second, maybe the Belkins were faked products which sometimes even find their way into the supply chain of the original brand manufacturer.
So never mind I thought, try to search sth. completely objective which is telling you what a USB hub in generally should be able to manage reliably.
So I stumbled over the EMI Design Guidelines for USB components and unfortunately realized that my technical knowledge is not sufficient to understand this.
The only non-single case issue I managed to siffon out of my matchcode search high quality USB hubs was the hint on a  German-speaking Forum, warning  for getting into deep trouble if hubs are delivered with power adapter of >5 Volt, relying on internal electronic to prevent to let through more – which in case of a defect could lead to a 6 or 9V input with fatal consequences. I assume as the device is powered by 5 Volt micro USB there I do not need to become headaches about this warning. So what I really wanted to know, which USB hub offered with 7 or 13 or whichever number of ports – as long as above 4 to connect mice, keyboards, network adapters and external storage can I surely rely on without embarking on such horror stories as the guys who posted on the Terry White Forum about their 2007 Belkin experience.

toxibunny
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Re: What should I know about USB hubs beyond: a high quality is good!

Sat Jan 21, 2012 11:01 am

My advice: Ignore the forum post nightmare stories and just get a powered usb2.0 hub that suits your budget. You"ll probably find you have no problems whatsoever, but keep your reciept just in case.
note: I may or may not know what I'm talking about...

mightygoose
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Re: What should I know about USB hubs beyond: a high quality is good!

Sat Jan 21, 2012 11:58 am

what about smart hubs underpowering the device...

BlueClogger
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Re: What should I know about USB hubs beyond: a high quality is good!

Sat Jan 21, 2012 12:31 pm

mightygoose said:


what about smart hubs underpowering the device...



The consensus on the forums is that you will be better off with a separate USB wall wart which can supply at least 1A. Smart hubs should limit the current draw on any one device to 500mA, which is not enough for a Model B.  Model As might get away with it if nothing else is drawing from the Pi.  If you have a 2A+ PSU and can split the output you could drive the Pi and a smart hub from one device.

sandytrisquirrelon
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Re: What should I know about USB hubs beyond: a high quality is good!

Sun Jan 29, 2012 12:13 am

Powering the Pi adequatly USB hub vs. wall wart & extra PSU

Thank you all for your suggestions which followed promptly. It took me by surprise I didn't expect such quickly help:-) I was just re-visiting the Forum today. Sorry as a non-techi I am still a bit confuse with the options you tried to explain. Do you mean that I could finally substitute a USB hub with a wall wart (just learned about what this is meant to be) - if it was for Pi "B" - a w. wart type, able to supply 2A - and a seperated PSU, splitting the output? By the way: How does a "Hardware-for Dummies person" like me manage to split the output? ;- I'd fancy with the idea to have little cable and tiny power devices, not wanting to turn the Pi into an Oil-Rig with lot's of cables like pipelines connected with it;-) and a whole power supply plant as a pheripery, so maybe, thinking into the future I should from the very beginning, make sure that I have a powerful external power supply, even more if I plan to connect other devices with the Pi - no matter if "A" or "B" Pi. Finally I have no clue how a PSU could look like, my google search mostly mounted Switched-mode power supplies (SMPS) which looked rather heavy and a bit bulky. Any idea at which websites I could get an orientation on PSU types? I will extend your advice on USB hubs "try and error strategy - save the receipt" when purchasing a wall wart? Looking fwd. to your response, hoping that I do not bug you too much with my Dummy Questions - hope there will be other people on the forum who are as newbee as me and can also learn from the response you're giving.

jraff1
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Re: What should I know about USB hubs beyond: a high quality is good!

Sun Jan 29, 2012 4:52 am

The "A" type takes 300ma, the "B" type takes 700ma approximately.

A lot depends on just what program is running, and how much video is being created by the GPU. Most peripheral power units "Wall Warts" (because they look like a wart on the wall) can supply that with out breaking a sweat. Depending on what other peripheral circuitry one has to supply power to support the external devices, one adds the expected power usage plus a little bit or a lot again depending on expected surges and temporary power drains.

So one has a "B" unit which requires 0.7A and external circuitry which may take 0.3 to 0.5A. One could assume then that a 1.5A supply could easily cover the power demand.

Google show $2 to $22 for such a device - http://www.google.com/search?q.....038;tab=wf

Be sure to select on with the proper voltage for one's country. Good luck - YRMV

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abishur
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Re: What should I know about USB hubs beyond: a high quality is good!

Sun Jan 29, 2012 5:07 am

It should be noted that power speaking the model A and the model B are identical except for the Ethernet port (which would take a minimal amount of power) and the extra USB port.  The main reason for their estimate of 700 mA for the model B is because they were assuming an extra amount of draw down the extra usb port.  Which is to say, unless you have a big item attached to the port, then you should be able to power the model B from around 300 mA too (the extra amount of RAM shouldn't be a huge power sink either)
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jojopi
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Re: What should I know about USB hubs beyond: a high quality is good!

Sun Jan 29, 2012 10:28 am

Abishur said:


It should be noted that power speaking the model A and the model B are identical except for the Ethernet port (which would take a minimal amount of power) and the extra USB port.  The main reason for their estimate of 700 mA for the model B is because they were assuming an extra amount of draw down the extra usb port.


The LAN9512 draws up to 231mA with Ethernet in use.  That is over a watt, given that it is supplied by LDO.  This actually accounts for most of the difference between the models.

sandytrisquirrelon
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Re: What should I know about USB hubs beyond: a high quality is good!

Sun Jan 29, 2012 2:54 pm

Abishur said:


It should be noted that power speaking the model A and the model B are identical except for the Ethernet port (which would take a minimal amount of power) and the extra USB port.  The main reason for their estimate of 700 mA for the model B is because they were assuming an extra amount of draw down the extra usb port.  Which is to say, unless you have a big item attached to the port, then you should be able to power the model B from around 300 mA too (the extra amount of RAM shouldn't be a huge power sink either)



Thank you all for again giving me an orientation including the 2A wart wall search result. I have the impression all of you yet got a very good technical overview and are not even lost, if confronted with questions that get into detail. Think I will be well adviced to catch up at least a little bit, now properly reading the http://elinux.org/RPi_Hardware.....asic_Setup to get a better understanding and might then get back to you asking more refined questions;-).

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abishur
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Re: What should I know about USB hubs beyond: a high quality is good!

Sun Jan 29, 2012 3:31 pm

jojopi said:


Abishur said:


It should be noted that power speaking the model A and the model B are identical except for the Ethernet port (which would take a minimal amount of power) and the extra USB port.  The main reason for their estimate of 700 mA for the model B is because they were assuming an extra amount of draw down the extra usb port.


The LAN9512 draws up to 231mA with Ethernet in use.  That is over a watt, given that it is supplied by LDO.  This actually accounts for most of the difference between the models.



I stand corrected, I had missed that part of the data sheet.  Still the sheet says "All values measured with maximum simultaneous traffic on the Ethernet port and all USB ports."  and the 300 mA estimate for the model A included a single usb device attached so in theory the model B with no devices attached to the ports (such as if you were using a self powered usb hub) should come in slightly under 500 mA, but I know I'd personally rather give it more wiggle room.  Thanks for catching that!
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