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This USB 2.0 hub gets the power from one this PC's one of USB port. The hub is connected to six of this USB DAQ devices. The hub both communicates and powers the six DAQ boards.The power for the DAQ is given as:

enter image description here

I have read here that max current cen be drawn from a USB 2.0 port is 500mA and for USB 3.0 port is 900mA.

In my case it seems the current needed for six DAQ is 230 * 6 = 1.5A. Does that mean I'm exceeding limits for the PC's USB port??

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closed as off-topic by brhans, RoyC, Finbarr, awjlogan, Lior Bilia Dec 11 '18 at 14:15

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  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – brhans, RoyC, Finbarr, awjlogan, Lior Bilia
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Yes, you are definitely trying to draw too much current from USB 2.0 port if you add more than one of those devices in one port.. I recommend to add external power supply.

Edit: Seems like hub had external power supply so good to go.

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  • \$\begingroup\$ If I use a 5V 5A AC an adapter for the USB Hub, would it be adequate for six 230mA loads i.e like in total 2A? \$\endgroup\$ – atmnt Dec 7 '18 at 12:45
  • \$\begingroup\$ You need to carefully observe datasheet of the usb hub. But usually externally powered hubs can deliver that kind of currents for every USB device. \$\endgroup\$ – JuhoR Dec 7 '18 at 12:47
  • \$\begingroup\$ Found your hub datasheet manualzz.com/doc/2953476/cables-direct-usb2-3010ten. And it clearly says its delivered with 2.5A power adapter. So you are good to go. Good luck! \$\endgroup\$ – JuhoR Dec 7 '18 at 12:50
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You definitely exceed the current limit. Further more the standard says 500mA and 900mA, but you can not count on these values. A lot of USB ports provide far less current than that (except of course those that are designated chargers) and will shut of if you load them to even half of the value.

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The USB 2.0 standard requires that each port can supply 100mA and puts a maximum value of 500mA on a port.

When I device connects it must draw 100mA or less until it has enumerated. Enumeration is the process by which a device connects to a host. Part of this is requesting the current the device requires up to 500mA. A device should not draw more than 100mA until it has requested it and the request has been accepted.

For this reason unpowered hubs are usually limited to 4 ports or less: 100mA per device plus up to 100mA to run the hub.

So yes you are asking more current than the host port on your PC is guaranteed to be capable of.


Dedicated chargers are an exception and may provide more, for example the charger for my mp3 player will provide 1.5A max.

Powered hubs usually provide 500mA a port and may have more than 4 ports as a result.

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