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Are their any limits to the power that can be drawn from a USB connection?

April 26, 2017connection drawn limits power USB

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Are their any limits to the power that can be drawn from a USB connection?

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Most USB devices get their power directly through the USB connection, so there is no need for external power supplies. The USB connection on your computer will furnish 5 volts DC at up to 500 milliamps. Drawing more than 500 milliamps will shut the port down. Some USB connections limit the current to less than 500 milliamps. This is common in laptop computers. The original Apple iMac limited the current to 200 milliamps. If you use a non-powered hub, the current from each port will be limited to approximately 500 milliamps, divided by the number of ports on the hub. It is good practice to use a self-powered hub, which has its own power supply, to make sure each port has a full 500 milliamp capability.