Sminlal is correct, and 505090 provided the corrective action for a 2 1/2 in HDD. For a 3 1/2 in drive a 12 Volt brick is required Vs the 5 Volt usb hub brick.
3 1/2 in regular HDDs require +12 V, not provided by a usb port. Usb Ports are low current (power) and even some of the 2 1/2 in HDDs exceed the power limitations for a usb port and require a "Brick"