What happens when you power a USB port?

[Marco2G]

Hi everyone

 

I am currently wrestling with a USB problem on my PC that has brought up a few questions.

 

See, I am using a USB 3.0 switch right now to be able to flip my peripherals between my home PC and my work laptop. Basic home office thing, right?

 

Today I just have a simple USB hub behind the thing but previously had had a USB-C docking station attached. The USB hub has the option to receive 5V power from a wallwart.

 

I remember with the USB-c dock that my PC would still have LEDs light up, on the GPU too, even though I flipped the power switch on the power supply because the USB-C dock had charging power on the USB-C uplink. The hub will probably do the same, I think.

I had a similar thing with my active USB extension cable that I used back when the PC whas in the attic and I used to jsut lay down 15m of USB and DP cabling to connect the peripherals. There too the 5V the cables introduced would light up the PC even when disconnected from main power.

 

My question is whether this is a problem.

 

I imagine it should be as I cannot imagine this being good for the motherboard.

 

Which brings me to the next question: Since my el-cheapo sabrent USB switch seems to downgrade the connection to USB 2.0 and thus does not allow for a USB 3 thumbdrive to be connected, I need to rethink my current setup. I don't particularly want to attach the dock anyhow as the additional ethernet port and HDMI and USB audio that then connects clutters up my HW list and frankly Linux does strange things when audio devices come and go like that. That being said, I need suggestions for a USB switcher and a HUB that follow USB standards, that WILL support all kinds of USB 3 (preferably 3.2) devices and that will not feed 5 volts into my PC or laptop.

 

So question: Is there any such solution out there that doesn't cost hundreds of $? The cheap chinesium crap obviously isn't worth even what little it costs.

[aDoomGuy]

Well first off USB 2.0 allow to connect USB 3.x devices allthough at a slower transfer speed (USB 2.0 speed will be used). So your 3.0 thumbdrive should work fine.

 

Next, what I understand from what you're saying is that with the PSU on a desktop PC turned off it get power from a USB hub? Well if I understood that correctly, I don't think that will be a problem. I highly doubt the USB hub runs 5v current right into your USB port in your PC. So no I don't think this will be a problem, I had a similar USB hub before and while I never tried to turn off my PSU to see if the hub would power parts of the PC I never had any problems with my USB controller.

 

22 minutes ago, Marco2G said:

that WILL support all kinds of USB 3 (preferably 3.2) devices and that will not feed 5 volts into my PC

Well USB devices are backwards compatible as I mentioned, I guess just don't get the cheapest alternative on Wish.com or something.

 

How about something like this?

https://www.distrelec.ch/en/usb-hub-7x-usb-gen-usb-socket-exsys-ex-1189hmvs-3w/p/30174058?q=usb+hub&pos=6&origPos=6&origPageSize=50&track=true

May be a bit pricy though but from my experience USB 3.2 hubs are a bit stiff on the cost.

 

By the way, I got a cheapo USB 3.0 hub with a power supply right now. The make is ZAP (lol) never caused me any issue. Also your profile says you're in Switzerland so I tried to find something there for you.

[Marco2G]

I just can't imagine that it's going to end well to put a voltage onto something that is not made to receive a voltage.

 

I changed my mind about the USB switcher. I will just have two USB extensions on my desk and attach the hub to the one I need.

 

So I thought why not upgrade to USB-C... turns out, most USB hubs with a USB-C connection upstream seem to suffer from weird effects, too, like disconnecting randomly and stuff..

 

I'm coming to the conclusion that USB has become such a commodity that nobody gives a fuck these days whether the stuff they sell even remotely works.


Edit: I just tested my USB 3.0 hub with external powersupply and this thing does not power my computer's LEDs when the PSU is off. The USB3 extension cord does.

 

[aDoomGuy]

23 hours ago, Marco2G said:

I just can't imagine that it's going to end well to put a voltage onto something that is not made to receive a voltage.

 

I changed my mind about the USB switcher. I will just have two USB extensions on my desk and attach the hub to the one I need.

 

So I thought why not upgrade to USB-C... turns out, most USB hubs with a USB-C connection upstream seem to suffer from weird effects, too, like disconnecting randomly and stuff..

 

I'm coming to the conclusion that USB has

Edit: I just tested my USB 3.0 hub with external powersupply and this thing does not power my computer's LEDs when the PSU is off. The USB3 extension cord does.

 

The extension cord is haunted. Or maybe it's possessed?

 

23 hours ago, Marco2G said:

has become such a commodity that nobody gives a fuck these days whether the stuff they sell even remotely works.

So, just like pretty much everything else then.

 

Seriously, no idea what to make of that...

[OhioYJ]

On 8/25/2021 at 9:34 AM, Marco2G said:

 The hub will probably do the same, I think.

 

Powered hubs do not feed power into the motherboard. At least they should not. Powered hubs take the load off of the motherboard. A USB port can only supply a specific amount of current. It's like a wall outlet, you can overload it, and fry it. A powered hub prevents this, only sending the data, supplying it's own power to devices. It also make sure high power devices receive the correct amount of power. Also keep in mind some motherboards keep USB ports powered at all times to charge devices as a "feature". This can be enabled / disabled sometimes in the BIOS, and this could possibly explain what you saw before? I don't know for sure though. I've used repeater cables before without any weird behavior (mine were just powered by the USB port though).

 

I have several USB hubs around here, and I probed a couple of them, none of them output 5v+ on the PC side. Only on the device side. Which is what would be expected.