[PLUG] Powered USB-A hub

[Michael Barnes]

On Tue, Jan 17, 2023 at 3:22 PM Galen Seitz <galens at seitzassoc.com> wrote:

> On 1/17/23 09:43, Rich Shepard wrote:
> > On Tue, 17 Jan 2023, Galen Seitz wrote:
> >
> >> Sorry, I haven't been following this thread too closely, but if this is
> a
> >> device you already own, you can look this up yourself. First use lsusb
> to
> >> find the vendor and product ID values for the USB device of interest.
> >> Then
> >> use lsusb again to get more information about the device.
> >
> > Galen,
> >
> > What a valuable lesson!
> >
> > # lsusb -v -d 1235:8211 | egrep 'iProduct|MaxPower'
> >    iProduct                3 Scarlett Solo USB
> >      MaxPower              500mA
> >
> > This suggests to me that a less expensive hub with fewer ports that has
> at
> > least 50W published power would work with all three devices.
>
> FYI, the typical 4 port powered USB 2.0 hub is supplied with a 5V
> adapter that is capable of ~2A, or about 500 mA per port.  With a USB
> 3.0 hub where the per port current limit is 900 mA, the max adapter
> current should be higher, but it's unlikely the adapter would be sized
> to allow the max current on every port.
>
> Hubs that have high (>15W) wattage are likely intended to support some
> sort of charging of phones/tablets/etc where communication regarding the
> larger current capability is communicated through a different mechanism.
>
> Once again, the above does not directly apply to USB C hubs that support
> power delivery.
>
> Rich, if you have three devices that draw 500 mA, a hub with a 2A
> adapter should be sufficient.  Look for a hub with a 2.5A or 3A adapter
> if one or two of your devices draw 900 mA.
>
> BTW, I can guarantee you that virtually all of the crazy USB-powered
> things you can buy do *not* have USB descriptors.  Your Ronco USB fan,
> light, and turnip twaddler connect to VUSB (5V) and immediately attempt
> to draw whatever they need, regardless of any intended USB constraints.
> Buyer beware.
>
>
> galen
> --
> Galen Seitz
> galens at seitzassoc.com
>

I didn't go back and re-read all the comments, but just wanted to throw a
few things out.
First for USB powered devices/charging (phones, laptop coolers, keyboard
lights, etc.), I strongly recommend not using a USB hub for these. If you
are not using a data connection, then just get a multi-port USB charger.
Look at the available current *per port* then be sure the overall
capability supports that much. For example, it may show six ports at 2.5
amps per port, however the total capacity is only 10 amps. That means you
cannot expect to get 2.5 amps to each device if you have more than four
high current devices plugged in.

Computer USB ports (doesn't really matter if USB 2/3/?) typically only
source 500 ma. Even most powered USB data hubs are limited to 500ma per
port. Check the specs carefully. This is normally fine for most data
devices. You definitely want a powered hub for data devices, though, so
each one will have its full 500ma available to the device. A non-powered
hub must share the entire 500ma available current from the computer with
all devices, and some will come up short, giving unpredictable results.

Just some thoughts.

Michael