ReneU2
Posts: 4
Joined: Fri Apr 13, 2018 1:02 pm

USB power Pi Zero W

Mon Apr 16, 2018 6:27 pm

Hi,
how many ampere can the usb port from a Raspberry Pi Zero W deliver?
I could not found any specs about it.

Thank you for your help.
Regards
René

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fruitoftheloom
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Location: Bognor Regis UK

Re: USB power Pi Zero W

Mon Apr 16, 2018 6:31 pm

ReneU2 wrote:
Mon Apr 16, 2018 6:27 pm
Hi,
how many ampere can the usb port from a Raspberry Pi Zero W deliver?
I could not found any specs about it.

Thank you for your help.
Regards
René

https://www.raspberrypi.org/help/faqs/#topPower
""understanding the theoretical, but not always the end goal""

My other Devices are the ChromeBit CS10, ChromeCast & Huawei Mate 10 Pro SmartPhone

julyjim
Posts: 58
Joined: Tue Jan 31, 2017 5:04 am

Re: USB power Pi Zero W

Tue Apr 17, 2018 5:29 pm

"Limited by PSU, board, and connector ratings only." Per Zero "specification".

How is that for "spec" ?

The " connector ratings only" has little to do with how much power you can get FROM Zero USB port..
Perhaps Zero schematic would answer the question.

The USB connectors power ratings are well specified / described in USB spec.
But that is not the question, right?

The question is - how much POWER can the Zero USB port provide.

gkaiseril
Posts: 317
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Location: Chicago, IL

Re: USB power Pi Zero W

Tue Apr 17, 2018 5:50 pm

I would not exceed the 5 v dc 1.2 amp power supply. The Pi Zero has no voltage or current limiting circuitry so the power supply need s to be limiting controller. You could use a larger power supply but if any accessory starts to draw a much larger current you may burn up the Pi Zero.

julyjim
Posts: 58
Joined: Tue Jan 31, 2017 5:04 am

Re: USB power Pi Zero W

Tue Apr 17, 2018 8:47 pm

The Pi Zero has no voltage or current limiting circuitry so the power supply need s to be limiting controller
Excellent point, but ...
Since it has 3.3V output on GPIO , same as 3B ( as an example ) it has to have 3.3 V regulator and NO 5V regulator ?
Assuming Zero is intended for mobile use (?) where does one get 5.2V battery ?
Again - this is all speculation - the real answer would be in an official schematic.

ReneU2
Posts: 4
Joined: Fri Apr 13, 2018 1:02 pm

Re: USB power Pi Zero W

Wed Apr 18, 2018 6:25 pm

Thank you for your answers. I only need less than 500mA from the Zero.
I thought that there would be maybe a limitation because my device didn't work.
However there was a problem with the UB cable. With a new cable all is working fine. :D

Regards
René

hippy
Posts: 2742
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: USB power Pi Zero W

Wed Apr 18, 2018 7:31 pm

julyjim wrote:
Tue Apr 17, 2018 5:29 pm
"Limited by PSU, board, and connector ratings only." Per Zero "specification".

The "connector ratings only" has little to do with how much power you can get FROM Zero USB port.
I think you may have misinterpreted what it was intending to present in its terse manner. More fully -

"The amount of current you can draw out of the USB socket on a Pi Zero is only limited by PSU, board, and connector ratings".

Basically if you put 1A in you can take out 1A less what the Pi itself uses, if you put 2A in you can take out 2A less what the Pi uses. But you can't go above a current which will burn the tracks off the board or exceed the connector rating.

julyjim
Posts: 58
Joined: Tue Jan 31, 2017 5:04 am

Re: USB power Pi Zero W

Wed Apr 18, 2018 9:16 pm

Fried,
this is becoming more and more pointless.
Your arguments are academically valid , however, the Raspberry foundation apparently prefers few burned out Zeros than spending money on REAL spec.
If somebody wants to make bootleg Zero - the technology is there, but same "argument" can be applied.
Why spending time and money on $10 device - as advertised.
BTW - I paid $15. Go figure.
Back to coding.

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Imperf3kt
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Location: Australia

Re: USB power Pi Zero W

Wed Apr 18, 2018 9:43 pm

You pretty much cannot burn out the Pi0 by drawing too much current over the uUSB port.
If you supply it 50A, you'll still only ever get out what the port can provide, which is less than the point needed to destroy the Pi.

As to the 500mA question, give it 1A or more from a decent supply and cable, and it'll work fine.
Stephen Hawking, rest in peace.
8 January 1942 – 14 March 2018

hippy
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Location: UK

Re: USB power Pi Zero W

Fri Apr 20, 2018 12:42 pm

Imperf3kt wrote:
Wed Apr 18, 2018 9:43 pm
If you supply it 50A, you'll still only ever get out what the port can provide, which is less than the point needed to destroy the Pi.
I do agree with julyjim that defining things in terms of track and connector current carrying capability is rather meaningless when no one will state what those capabilities and limits are, but that's the best one can say unless the RPT/RPF provide those figures.

I have repeatedly asked what the current ratings are for the USB connectors but have never received an official response.

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Gavinmc42
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Re: USB power Pi Zero W

Fri Apr 20, 2018 1:17 pm

It would depend on the copper PCB tracks.
Power in one USB, power out the other USB connector.
At what point do the copper tracks between them becomes fusible links?
It will cost $5 to find out ;)
I am guessing between 1 and 10 amps without finding one and looking at it.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

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mahjongg
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Re: USB power Pi Zero W

Fri Apr 20, 2018 1:28 pm

Power and ground traces run directly from the power input USB port to the USB output port, so your question is meaningless.

Whats more the OP's question was already answered, and as expected no answer was needed to the question, as any problems were not caused by any imagined current limitation.

Therefore locking.

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