bluenote
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What kind of power supply to this USB 3 hub?

Wed May 20, 2020 10:03 pm

Hi,

I bought this USB 3 hub, but unpowered, connecting it to 3 USB hard drives that are powered themselves drains too much power from my PI and things don't work quite right. I'd like to buy an AC adapter (or use one that I have kicking around) but I don't want to blow up my stuff.
The voltage is not marked on the casing :( And the supplier ... does not seem to understand the question. :(
Here is the hub that I bought. Thanks for any suggestions!
https://www.aliexpress.com/item/3279050 ... 4c4d32sFXL

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dickon
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Re: What kind of power supply to this USB 3 hub?

Wed May 20, 2020 10:10 pm

Googling for the model number -- a good tip, if you want to find information on otherwise-undocumented devices -- finds an image which suggests it's 5V at 3A. Can't be sure if it's centre-positive (which is normal, but not universal) or not.

Dunno.

W. H. Heydt
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Re: What kind of power supply to this USB 3 hub?

Thu May 21, 2020 1:14 am

dickon wrote:
Wed May 20, 2020 10:10 pm
Googling for the model number -- a good tip, if you want to find information on otherwise-undocumented devices -- finds an image which suggests it's 5V at 3A. Can't be sure if it's centre-positive (which is normal, but not universal) or not.

Dunno.
Typical underpowered spec. To fully power 4 USB 3 ports, it should have a PSU rated at enough more than 3.6A for the hub itself.

trejan
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Re: What kind of power supply to this USB 3 hub?

Thu May 21, 2020 1:53 am

dickon wrote:
Wed May 20, 2020 10:10 pm
Googling for the model number -- a good tip, if you want to find information on otherwise-undocumented devices -- finds an image which suggests it's 5V at 3A. Can't be sure if it's centre-positive (which is normal, but not universal) or not.
That must be the mega ultra deluxe bundle. I've found the same USB hub elsewhere and the photo of that bundle has a 5V 1A PSU which would be woefully underpowered. PSU label does say center positive though.

bluenote
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Re: What kind of power supply to this USB 3 hub?

Thu May 21, 2020 4:22 am

Thanks for weighing in gents. Ali doesn't seem to sell that model # with a PS that I found. I did find this power adapter that I think fits the spec.
I didn't try powering this up just in case :) It does fit, but as you can see in the picture it sticks out a bit. Is this good enough? I'm not sure I remember what this was off, but it would get me by for the moment anyways. Next time I won't buy a hub that doesn't come with a power supply.

So will this blow up?

I don't see a way to insert a picture, here's a link: https://imgur.com/nH7jTH5

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dickon
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Re: What kind of power supply to this USB 3 hub?

Thu May 21, 2020 7:17 am

That's 5V at 2A. No idea if it'll be enough for your devices, and of course there's no telling how the thing is connected up internally: you may end up back-powering the Pi via its USB port if you're not careful. That may be a bad thing; I don't know.

bluenote
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Re: What kind of power supply to this USB 3 hub?

Fri May 22, 2020 5:49 pm

Thanks. I don't suppose anyone can explain how post power adapters are commonly referred to do I can try and buy one with the right end? Is there standardization??

W. H. Heydt
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Re: What kind of power supply to this USB 3 hub?

Fri May 22, 2020 6:39 pm

bluenote wrote:
Fri May 22, 2020 5:49 pm
Thanks. I don't suppose anyone can explain how post power adapters are commonly referred to do I can try and buy one with the right end? Is there standardization??
For barrel connectors, the specs should be outside diameter x inside diameter, center positive or center negative, nominal voltage, claimed maximum current, and whether it is DC or AC output. Often, the polarity will be a glyph with a line to a partial circle and either + or - and a line to a dot within the circle leading to either a - or +. On some devices you will see the input rated with a dotted line over a solid line. That's AC input.

I say "nominal voltage" and "claimed current" because far too many such devices will not deliver the stated voltage anywhere near the asserted current.

Now then... What I would recommend is to find a hub that comes with a PSU. For a 4-port USB 3 hub, look for one with a PSU rated for at least 4A. then test the hub to make sure it doesn't provide power back up the connection from the upstream device. One of the easy (and cheap) way to test this is to connect the hub to a Pi0. If the Pi0 power up, the hub is backfeeding power and you need to get a different one. You don't even need an SD card in the Pi0 to do this test, so the total outlay is $5 (plus shipping, handling and taxes).

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davidcoton
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Re: What kind of power supply to this USB 3 hub?

Fri May 22, 2020 8:48 pm

W. H. Heydt wrote:
Fri May 22, 2020 6:39 pm
On some devices you will see the input rated with a dotted line over a solid line. That's AC input.
Er, I don't think so. I haven't found dotted over solid on any of my PSUs.
However, solid line over dotted line is common and means DC (usually for outputs but conceivably used on inputs too).
The usual symbol for AC is a tilde "~".

Of course, it's quite possible that other conventions are used in some areas.

EDIT: more variants listed here but no standards cited.
Last edited by davidcoton on Fri May 22, 2020 8:55 pm, edited 1 time in total.
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dickon
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Re: What kind of power supply to this USB 3 hub?

Fri May 22, 2020 8:52 pm

I thought that sounded wrong.

bluenote
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Re: What kind of power supply to this USB 3 hub?

Fri May 22, 2020 10:14 pm

Thanks gents. Seems to be hopeless to find the PS I need then, and considering all 4 hubs I own feed power back ...

W. H. Heydt
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Re: What kind of power supply to this USB 3 hub?

Sat May 23, 2020 12:55 am

bluenote wrote:
Fri May 22, 2020 10:14 pm
Thanks gents. Seems to be hopeless to find the PS I need then, and considering all 4 hubs I own feed power back ...
Find a better grade of hub. It may not be a bargain bin unit, but it pays off in the long run.

rpi_vii
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Re: What kind of power supply to this USB 3 hub?

Wed Jun 03, 2020 1:01 am

anyone have a recommendation for small powered usb 3.0 hub with no back feeding issues?

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