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View Full Version : USB Hub Scare



TomS
02-05-2007, 09:08 PM
I just purchased a Kensington DomeHub and after installing and testing it I turned my computer off. The LED's on the Demo board On-Board USB to Serial converter came on with what I would say is extreme brightness. I immediatly pulled the plug on the hub. I then decided to find out if there was an actual problem. It seems the voltage drop across the 100 ohm resistor in series with the LED's was 1.5VDC and the power dissipation in the resistor is only 22.5mW. A 0402 resistor can safely handle that power level. I guess the brightness of the LED's freaked me out. The same thing happens with the Propeller clip/plug. I don't know if the voltage on pin 1 of the mini USB connector is supposed to go to zero or not when the computer is turned off but it doesn't appear to harm anything.

Out of curiosity does anyone know of any other usb hubs behaving this way? The two, small, Belkin 4-port hubs I used previously didn't exhibit this behavior.

Tom