USB bus seems to be shutting down after 30seconds


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by Helpme1986 » Thu Apr 19, 2012 9:09 am
Do you think this should be good enough for the Pi?

http://www.amazon.co.uk/CHARGE.....038;sr=1-1

Would love for others to share their working power supply's and where they got them.
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by colin B » Thu Apr 19, 2012 9:16 am
Looks perfect to me, it doesn't say how long the cable is nor the output voltage, but I assume it'd be 5v.

The quality of the USB cable is the only real unknown.
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by Helpme1986 » Thu Apr 19, 2012 9:19 am
Ive ordered that along with a battery:

http://www.amazon.co.uk/exec/o.....os_product

Which has a 1amp and a 2.1amp output, in theory should power my pi for days.

I have an official HTC and Samsung (U2) USB to Micro cable so I dont think its the quality of cable, lets hope the quality of the charger is good enough!
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by Helpme1986 » Thu Apr 19, 2012 9:19 am
DOUBLE POST, PLEASE DELETE

*Dam work internet connection!
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by davehigton » Thu Apr 19, 2012 12:28 pm
Please, people, use the correct units.

Currents are measured (often) in milliamps: mA.

Battery capacities are measured (often) im milliamp-hours: mAh.  That's current multiplied by time.  For example, a 500 mAh battery should be able to supply 500 mA for one hour, or 250 mA for 2 hours, etc. (Caveats apply, I know, but I'm trying to keep it simple here.)
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by Helpme1986 » Thu Apr 19, 2012 12:35 pm
Sorry, the battery capacity is 7000mAh, 1 port provides 1000mA and the other 2100mA (is that right? im new to electricity terminology but im getting there!)

Am i right in saying that if the capacity is 7000mAh and the Pi requires a 700mA supply, if it used all that 700mA constantly it would last for 10 hours?
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by colin B » Thu Apr 19, 2012 12:41 pm
Helpme1986 said:


Am i right in saying that if the capacity is 7000mAh and the Pi requires a 700mA supply, if it used all that 700mA constantly it would last for 10 hours?


Yes you would be correct in theory, in practice you would get slightly less than that, but as a rule of thumb it is a good guide.

**edit** The above applies to an actual battery, I've just looked at your Amazon link, and in your case you will probably get very close to the theoretical 10 hours as there are electronic gubbins (technical term there) inside that case.
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by Helpme1986 » Thu Apr 19, 2012 12:50 pm
yeah of course, plus on the packaging it says 6600mAh (bit miss leading but never mind)

Will update the Wiki if should it work as I can image a few people wanting a totally portable Pi
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by Helpme1986 » Thu Apr 19, 2012 7:27 pm
After a night round my friends house (fellow geek) im 99% sure my Pi is faulty :(

At his we tried:

HTC 1A

Samsung 1A

Samsung 2A (Worked the best but still dropped, all of these with 3 different USB Cables, all official and not cheap)

A different router and ethernet cable

Different TV's and HDMI cables

4 different SD Cards (All booted the OS fine)

Different Keyboards and mice (with and without powered hub)

The best we could do was get it stable with the Samsung 2A supply and no ethernet, as soon as the ethernet plugged in it would drop regulary (but this time come back after a while which never happened before, but of course drop again)

I can only assume there is a bad solder on the board which the 2A supply is helping with (compared to the 700mAh) but ultimatly is still suffering.

What would the Foundation prefer? Given its a dev board do they want it back to do their own tests (happy to pay for postage each way) or just return to RS?
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by jbeale » Thu Apr 19, 2012 7:50 pm
I don't know what the official policy is on returns, but if you can reach Pete Lomas [Liz - Pete's contact details redacted - he's just sent me a bewildered email about this, and it's really not something we want to be spending his time on because he is a *very* busy man!]]
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by Helpme1986 » Thu Apr 19, 2012 7:54 pm
Liz has mailed me back (Big thank you, i know how busy you are!) and said to return it to RS who will in turn send it back to them for testing :D (though ill drop Pete a mail)

Just hope I dont have to wait to long for a replacement
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by Boreatton Scouts » Thu Apr 19, 2012 11:39 pm
I had similar problems - started with a iphone plug and usb cable with unpowered hub and moved to powered hub and ipad plug... drops usb when i have a wifi adapter, keybd, and mouse and hdmi runnig. All usb devices on the powered hub. I also noticed that I only have 192 Mb ram - anyone else short on ram?
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by johnbeetem » Fri Apr 20, 2012 12:55 am
Helpme1986 said:

I can only assume there is a bad solder on the board which the 2A supply is helping with (compared to the 700mAh) but ultimatly is still suffering.

It would be interesting to know the voltage at RasPi for each power supply.  For example, a higher voltage could cause RG2 to run hotter which could cause a marginal F3 to misbehave.  Only a hypothesis.  I wonder how the software decides to shut down USB?  It is monitoring the USB voltages on the USB ports?

Just wondering and hoping my comments might help the debug process.
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by colin B » Fri Apr 20, 2012 1:02 am

John Beetem said:

It would be interesting to know the voltage at RasPi for each power supply.  For example, a higher voltage could cause RG2 to run hotter which could cause a marginal F3 to misbehave.


RG2?  What component are you referring to?
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by jbeale » Fri Apr 20, 2012 1:05 am
Boreatton Scouts said:


I also noticed that I only have 192 Mb ram – anyone else short on ram?


The GPU and CPU have different memory allocations:

We will supply 3 versions of the GPU firmware built for different split sizes (ARM with 128M, 192M and 224M). We hope to eventualy use CMA to handle dynamically moving the memory split, but that's a significant job that will take a while.

-from http://www.raspberrypi.org/for.....txt/page-3
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by jbeale » Fri Apr 20, 2012 1:10 am
bodgyuk said:



John Beetem said:

It would be interesting to know the voltage at RasPi for each power supply.  For example, a higher voltage could cause RG2 to run hotter which could cause a marginal F3 to misbehave.


RG2?  What component are you referring to?


RG2 is the 3.3V regulator, which is physically located on the top side near the microUSB power connector. F3 is near that location but on the bottom side.. See also:

http://www.raspberrypi.org/wp-.....s-R1.0.pdf

http://itlounge.eu/wp-content/.....rry_Pi.jpg
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by colin B » Fri Apr 20, 2012 1:15 am
So it is :)   Couldn't see RG designators anywhere on the schematic, and I was wearing my glasses.

I wonder if some small reverse diodes across out to in would be prudent.
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by johnbeetem » Fri Apr 20, 2012 6:19 pm
bodgyuk said:

I wonder if some small reverse diodes across out to in would be prudent.

I was curious so I checked the ONsemi NCP1117 data sheet for RG2.  In turns out it has a built-in protection diode which can withstand a 15A surge, so you usually do not need a separate external diode.
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by melondrop » Sun Apr 22, 2012 7:49 am
Wouldnt it be better to get a real switching power supply instead of trying phone chargers? Seems like alot of people are having problems using chargers.

You can get a good regulated ac to dc 5v 1.5 or 2a supply rather cheaply tho you might have to add your own mini usb connector.
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