USB hubs

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kenny1999

Member
USB hubs 1-to-4

It's said, improper current / voltage etc might lead to damage or even burn of the USB devices

So, when I looking for a USB hub, should I also look at the current of the device and the current of my computer?

How to know how much current or voltage will be drawn from my USB port on my computer side?

Becuase I do not want to purchase one that comes with power supply. I want to keep things little
 
All usb devices are rated at 5v, the only thing you need to worry about is making sure you have enough amperage to run all the devices plugged in, fortunately most of the time when you don't have enough amperage devices just don't work properly and don't burn anything.
Download and install cpu-z, then navigate to the mainboard tab and you can find out your motherboards manufacturer and product code. Use this code on the manufacturers website to find out the specifications of your motherboard and they should tell you what amperage the usb's are rated at.
You should also get an idea how much amperage your devices require to work properly, then you just try to stay under the max amperage.

Edit: On further research:

The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire to power connected USB devices.

A unit load is defined as 100 mA in USB 2.0, and 150 mA in USB 3.0. A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0; 6 (900 mA) in USB 3.0.
 
Last edited:
Shlouski said:
All usb devices are rated at 5v, the only thing you need to worry about is making sure you have enough amperage to run all the devices plugged in, fortunately most of the time when you don't have enough amperage devices just don't work properly and don't burn anything.
Download and install cpu-z, then navigate to the mainboard tab and you can find out your motherboards manufacturer and product code. Use this code on the manufacturers website to find out the specifications of your motherboard and they should tell you what amperage the usb's are rated at.
You should also get an idea how much amperage your devices require to work properly, then you just try to stay under the max amperage.

Edit: On further research:

The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire to power connected USB devices.

A unit load is defined as 100 mA in USB 2.0, and 150 mA in USB 3.0. A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0; 6 (900 mA) in USB 3.0.
Click to expand...



Do you mean for any device it can draw a max of 5 unit loads from ANY USB port of ANY computer?

If the USB port is connected to a USB hub, and the hub is connected to two USB devices

Does it draw a max of 5 unit loads or 10 unit loads


If I just ignore all this and pick up ANY USB hubs in the market without power supply, in the worst case it only does not work but it won't damage or burn my USB devices right???? Are you sure about that?? Thanks!
 
kenny1999 said:
Do you mean for any device it can draw a max of 5 unit loads from ANY USB port of ANY computer?

If the USB port is connected to a USB hub, and the hub is connected to two USB devices

Does it draw a max of 5 unit loads or 10 unit loads


If I just ignore all this and pick up ANY USB hubs in the market without power supply, in the worst case it only does not work but it won't damage or burn my USB devices right???? Are you sure about that?? Thanks!
Click to expand...

As far as I understand each usb2.0 port should be rated at 500ma or half an amp which sounds about right considering they are usually provided enough power for things like 2,5 inch external drives. The hub on its own will use very little power, buy whatever hub you want, its the devices that you plug into the hub that will need to share that available 500ma. If you plug in too many devices that require more amps than available then most likely something is going to stop working until it gets the current it needs, you would need to unplug other devices until enough current is available. Most likely in the short term nothing will be damaged by going over the available amperage, but of course I cant guarantee this, you need to do a little research and get an idea how much current your devices use so you don't put yourself at risk. Things like flash drives and mice normally use very little current and a hub running of one usb should be able to power many at the same time, but things like external HDD's which require more current (unless powered by their own source) are better off running off one port alone.
 
A USB 2.0 port is limited to 5V @ 500mA. If you are powering things like a keyboard, mouse, external hard drive that has it's own power supply, etc. you should be fine. If you end up plugging in large power draw devices like portable hard drives with only the USB cable, multiple flash drives, etc. you will need a powered USB hub.
 
The latest USB 2 revision can allow for 1.5A. I would recommend just getting a USB 3 PCIe card and installing that if your motherboard supports it.
 
Okedokey said:
The latest USB 2 revision can allow for 1.5A. I would recommend just getting a USB 3 PCIe card and installing that if your motherboard supports it.
Click to expand...
From a computers USB port? I have never seen one that can output that much current. I've seen plenty of USB 2.0 ports on chargers and end devices that can utilize up to 2.4A.
 
Okedokey said:
Thats the spec.
Click to expand...
That's only for the charging ports. Not for actual USB ports from your i/o panel on the mobo. The revision is for the Battery Charging revision 1.2 and only covers things like powered usb hubs from what I see in that gigantic pdf file.
 
Okedokey said:
Yes, but they're USB 2 and they are rated over 500mA, that was my point.
Click to expand...
I never said USB 2.0 was limited to 500mA, I said USB 2.0 ports on computers are limited to 500mA to the best of my knowledge. USB 3.0 allows for 900mA. However on dedicated USB 2.0 charging ports you can output 2-2.4A.
 
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