Artec replies on USB self-powered vs. bus-powered hub issues

Last time, we reported on a problem with connecting devices to a Macally USB iHUB. Bailey Walker purchased one of these hubs for his iMac so that he could connect both his Artec 1236 USB Scanner and Epson Stylus Color 740 printer connected simultaneously. He notes:

"The Artec scanner is unusual in that it does not have a separate power supply and draws its power from the USB port. It works flawlessly when connected to one of the USB ports on the iMac. However, I cannot get it to work when connected to the Macally USB iHUB, even when the power supply is connected. I suspect that the Macally USB iHUB is not providing sufficient power to the USB ports, even when the power supply is used but I have no way of verifying this."

However, he did contact Artec Technical Support about this issue. They offered an informative reply about using USB self-powered vs. bus-powered hubs:

The Artec 1236USB is classified as "high power" USB device. It will consume about 470mA of power from the USB port. According to the USB standard, a self-powered USB hub should be able to provide 500mA of power per port, and a bus-powered USB hub should be able to provide 100mA of power per port. Therefore, Artec 1236USB scanner has to be used with self-powered hub.

Please be sure the USB hub you are using provides 500mA of power per port. The "Root Hub", which is the USB ports on your iMac, also provides 500mA of power. If the scanner could work with the Root Hub, it should be able to work on a self-powered USB hub that provides 500mA per port. Try to check this with USB organization on the web. Or check the AC adapter of your USB hub. If the AC adapter doesn't provide at least 2.0A, then you know the hub most likely won't output 500mA per port.

To get the scanner to work, they suggested connecting the scanner directly to one of the iMac's ports and connecting the hub to the other port. Then connect all other USB devices, including the keyboard, through the hub.