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USB Hub question?

Discussion in 'Hardware' started by Bonecrusher123, Jul 20, 2011.

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  1. Bonecrusher123

    Bonecrusher123 Thread Starter

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    hey guys, i bought a 4 port USB hub that isn't powered. i've never used one before. these are my questions:

    - by plugging my mouse into the hub, would the 'reaction speed' change at all? would it be better to plug the mouse (as it's the most important device) directly into a USB port?
    - could an external portable HDD (one that's not plugged into a wall) work? or would it need power? would it be able to charge a small mp3 player battery? i'm not worried about how speed will be effected, just if the devices will work or not. the salesguy said they'd work, but a printer would not.
    - is there anything else i need to consider as far as limitations of USB hubs go?
    - i had some other questions, but cant recall them.

    thanks
     
  2. Fractalogic

    Fractalogic

    Joined:
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    Messages:
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    Hi there!

    1. Since a USB hub is a passive component, there should be no difference.

    2.
    Yes, an external HDD that normally is not plugged to the mains will still work when connected to a USB hub, just as if it was connected to the USB port directly.

    3. Yes, it will be able to charge Mp3 players that are designed to be charged via the USB port, just as if it was connected to the USB port directly.

    4. A USB capable printer is usually using the USB port for communicating with the computer, but it relies on the mains outlet for its power supply. This is because printers usually need much more current than what can be delivered from a standard USB port. A USB port can deliver between 500 mA to 900 mA depending on the USB specification. A USB printer requires about 1.8 A, that's 1800 mA, or even more. There are however powered USB controllers and USB hubs which use additional power lines and can deliver up to 6 A. But this is not the subject of this thread anyway.

    I think you're good to go. You can start connecting your USB devices. You can for instance connect your devices like this.

    Port 1: Mp3 player
    Port 2: Mobile phone
    Port 3: External HDD
    Port 4: Digital camera

    USB hubs, the passive non-powered ones in particular, are usually used for USB devices that you use on the go. They are not intended for permanent installations. Not that it cannot be used for that, but it's just not convenient for that purpose. They usually just sit on desktops, waiting for you to come back home or to the office and connect whatever USB device you have with you. To connect your camera for instance, to transfer your newly taken pictures.

    For this reason alone, I avoid using USB hubs for things like USB keyboard and mouse. I connect these directly to the computer. I usually connect them to the first two USB ports.

    I actually have a system for connecting USB devices. I connect my USB devices according to their importance and how often I connect or disconnect them, or how "permanent" the installation will be is another way to put it. Like, for instance I connect the receiver for my wireless keyboard and mouse to the first USB port. Then I would connect the USB cable to my USB hub built inside the monitor. Then I would connect my WLAN adapter USB cradle cable to the next port. I would work my way like these down to my printer and scanner and until there are no devices to connect.

    The benefit I see with doing it like this is that I can more easily group, sort, and line up the USB cables for those devices that I know I will not be disconnecting and reconnecting often. And I have the remaining USB ports easily accessible, with no tangled USB cables in the way, no cable mess to deal with. So I use the remaining ports only for removable devices. But not only that, I use these remaining ports, only after I have managed to occupy all my USB hub ports on my monitor. Which almost never happens, so I am not at all running out of USB ports at any time. I have 6 of them on the computer, and 2 additional on the monitor. That's enough for my needs.

    Could this be an idea worth copying? I sure like to keep all my cabling work nice and snug. It makes it more fun to deal with it later on when you are trying to fix a problem. I hate messy cabling work where all the cables are nested and ****ed up. I just wanna grab them and rip them apart altogether and redo the work the proper way. I guess it becomes second nature when working with cables all the time as an electrician for several years.

    I hope this answers your questions. Feel free to ask if you got further questions.
     
  3. Courtneyc

    Courtneyc

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    Fractalogic is almost correct, but he missed one important part of your question. Your USB hub is unpowered.

    That means that all power, including what is needed to power the USB hub itself, must come from the USB port on the computer. That means that you get 500mA for use for all 4 ports combined. You are good with the mouse, which will take about 100mA. But the external hard drive will use 500mA alone. You will get a Windows popup that says one of your USB devices has exceeded power limits and the hub's devices will quit working (including your mouse). You will have to disconnect all of the devices, unplug the hub, and plug it back in.


    An unpowered hub is actually designed for devices that have their own power, devices, such as self-powered hard drives, or printers. It doesn't really work well for devices that get their power from the hub.

    I would suggest you purchase an inexpensive powered hub. Alternatively, look at your hub; it may be powered. If you see a small hole on the device, it can be powered. You can get the cable at most Radio Shacks. It will have a tiny power plug on one end, and a USB plug on the other. (It will be a 12 Volt plug.)
     
  4. pbanutcase

    pbanutcase

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    Jul 12, 2011
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    all usb devices in the system will share the total available bandwidth for usb, meaning two external drives copying files over usb will work at half the speed of one usb drive copying files.
     
  5. Fractalogic

    Fractalogic

    Joined:
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    Yes, that is true. External disk drives need between 400 mA and 500 mA to operate. Exactly how much current it needs would depend on things like the capacity of the drive - the higher the capacity the more platters it needs, and that in turn requires more current.

    It would also depend on what type of drive it is. You know, SSD (solid state disk) drives don't require as much electrical power as traditional mechanical hard disk drives found in external disk products. A typical USB flash drive for instance would need about 90 mA for idling and up to 150 mA for read and write operations.

    But if 100 mA is used by the USB hub alone, then I don't really know how I manage to use my SanDisk Cruzer USB flash drives from the USB hub. On one computer I have it connected to the built in hub on the monitor, and it might just be a powered hub, I don't know. But on another computer, I connect it to an ST Lab branded unpowered USB hub and yet it still works just fine. Is it magic?!... I have several SanDisk USB flash drives, but I never use them all simultaneously though.

    It would also depend on how many other USB devices you have connected to the computer, or the USB hub alone. I seem to have two USB controllers on one of my computers. I think the Intel ICH9R controller has support for up to 4 USB ports, but I have additional 2 USB ports supported by what appears to be a Gigabyte chip. A configuration like this would obviously distribute and balance the power consumption much better, without overloading one single USB controller.

    Bonecrusher123, would you be so kind and try connecting only your external disk drive to that USB hub, and tell us if it works? I am curious to know if it will work or not. If it works, then you can try adding more USB devices to the hub. Please let us know your findings.
     
  6. Bonecrusher123

    Bonecrusher123 Thread Starter

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    that's great thanks.

    the mp3 player, USB flash drive work fine. no issues yet. but i dont have an external portable hdd to try.
     
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