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Backup Power for USB device -- does it exist?

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Edvard:
Would a powered hub do the trick?

    - RPi <--> powered hub <--> device
-mwb1100 (September 25, 2018, 07:24 PM)
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Aw man, I wish I had thought of that...

There you go, problem solved.  Good one, mwb1100!  :Thmbsup:

4wd:
The Y-cable would have also done the trick, plug the power-only lead into another USB charger/outlet or a power bank.

I know the RPi is already plugged into an UPS but if the power bank has two USB outlets and pass-through charging, could have plugged the RPi into the power bank also for a "mini UPS".

USB Host ports are usually protected against input voltage.

eg.

Backup Power for USB device -- does it exist?

But yes, a powered USB hub is cheaper/simpler, nice one mwb1100  :up:

Deozaan:
Some USB devices with the requirement of stable power have an extra powerplug mounted, I assume yours doesn't?
-Ath (September 25, 2018, 03:23 PM)
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This device doesn't require stable/constant power. But for my uses I'd like it to remain constantly powered.

It's a multi-purpose device which can run various applications. If it loses power momentarily then it will reset to the "application select screen" and require physical interaction to select and launch the correct app. Even if there's only one app installed. So even though I can program the RPi to automatically start up and resume operations after a reboot, the fact that the USB device loses power means I need to be physically at the device to get everything running properly again. But ideally I'd like to have this all tucked away in a dark corner somewhere I'll never have to physically access and just manage everything about it remotely.

And this issue seems to be specific to the RPi. If I have the USB device connected to a (Windows) laptop and reboot the laptop, the USB device remains powered.

Or alternatively to my Y-cable idea, maybe someone knows a setting I can tweak in Linux so that it keeps power flowing to the USB ports during a reboot. That would also be an acceptable solution for this issue.

Would a powered hub do the trick?

    - RPi <--> powered hub <--> device
-mwb1100 (September 25, 2018, 07:24 PM)
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I hadn't considered that. It just may work!

Though I'd hate to spend the money buying one only to find out it didn't do what I wanted. . . If I can find one cheap enough then I may give it a go.

The Y-cable would have also done the trick, plug the power-only lead into another USB charger/outlet or a power bank.
-4wd (September 25, 2018, 10:03 PM)
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That's another good idea. Thanks! I do have a Y-cable and a USB charger/power bank I can try out. Actually the Y-cables I have are for mini-USB connections and this device uses a micro-USB connection, so I don't have a usable cable after all. :(

I guess I need to look into getting a new Y-cable or a powered hub.

Thanks to everyone for their suggestions and help!

Deozaan:
I found this Y-cable which looks like it would do the trick for $7.58. But that would require me to give up my power bank (yikes!) or a USB "wall wart" adapter (not too bad).

Or for $2.37 more ($9.95) I can get this powered USB hub which will keep everything self contained and could perhaps be re-purposed in the future if I am ever in need of more (powered) USB ports on a given device. (I already have a USB hub but no AC adapter for it, and buying just an adapter is almost as expensive as buying a new hub with an adapter. >:()

Choices, choices. . .

Ath:
If it loses power momentarily then it will reset to the "application select screen" and require physical interaction to select and launch the correct app.
-Deozaan (September 25, 2018, 10:40 PM)
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Are you sure that power is disconnected during boot of the RPi? Could it be that the device is reset via USB initialization commands? In that case, all your 'keep power applied' actions will be in vane...

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