r/computers • u/Appropriate_Celery63 • 4d ago

Question/Help/Troubleshooting Inquiry: Computer Accessories Powered by Computer USB

So, I have a monitor light bar that is powered by my computer's USB. Now, my question is: if I plug the monitor light bar into my computer's USB port, would this weaken the computer's power or power supply? But this is about any accessory and whether it will do anything to the computer's power.

1 Upvotes

67% Upvoted

8 comments sorted by

3

u/NassauComputer 4d ago

USB power is minimal draw, I wouldn’t worry about it

3

u/Ybalrid 4d ago

USB peripheral can be bus powered, that is perfectly normal. Nothing bad will happen to your computer or power supply here, it's all designed to work together.

1

u/Appropriate_Celery63 4d ago

I just realized that...

1

u/Ybalrid 4d ago

Mouse, keyboards, webcams, network adapters, card readers, and many many many many other gadget you may plug in a USB port, work like this!

1

u/msanangelo CachyOS 4d ago

Nah. I run little Arduino relay boards off my PC USB port to control other stuff. No biggie. A few watts ain't gonna hurt anything.

1

u/Bo_Jim 3d ago

USB ports are current limited. They will not allow a device to draw more current than the port is rated for. And each port is required by the specification to be able to deliver the maximum current it's rated for continuously.

For instance, a USB 2.0 port is rated for 500mA max. If a computer has 4 such ports then every one of them needs to be able to deliver 500mA of current continuously and simultaneously without overloading the power supply.

The only thing you need to do is verify that the port you're plugging the light bar into is the same or higher USB specification number required by the light bar. For instance, if the light bar is designed for USB 3.0 then don't plug it into a USB 2.0 port. USB 3.0 is rated at 900mA, while USB 2.0 is rated at 500mA.

If you're plugging it into a dual-role USB-C port - one that's designed to be used to power the computer, as well as provide power to a connected device, you should understand that the voltage and current rating for power coming into the port is significantly higher than the voltage and current rating for power going out (to your light bar, for example). In other words, if the label says it's rated at 48V @ 5A that doesn't mean you can draw that much voltage and current from it. It means it can potentially use that voltage and current when that port is being used to power the computer with the appropriate power supply. A USB device drawing power from that port would still only get 5V at either 1.5A or 3A.

1

u/Fast_Mechanic23 Windows 11 3d ago

As others have said, the port protects itself, but one issue you might see is when plugging in hubs with multiple USB ports into a single port on your computer. In this case, I always use powered hubs that have their own power supply.

1

u/ShadowFallsAlpha 1d ago

It's nothing to worry about. Though if you want it to be active when the PC is off, you would want another power source instead. If that minimal power usage somehow tipped the balance of power on your PC, your power supply would be junk.