[gaffa]

Howdy, I am having a problem with my stepper motors. When I turn on my power supply and then turn on my computer the motors get power to them. However as the computer boots up the motors loose all power. The only reason I can think this is happening is because I run my driver board power from a usb power (5v) and the usb somehow resets as the computer loads (????). Should I be running the boards 5 volt power from a separate supply?

[TOTALLYRC]

Howdy, I am having a problem with my stepper motors. When I turn on my power supply and then turn on my computer the motors get power to them. However as the computer boots up the motors loose all power. The only reason I can think this is happening is because I run my driver board power from a usb power (5v) and the usb somehow resets as the computer loads (????). Should I be running the boards 5 volt power from a separate supply?

Not for anything, but you should be booting the computer first, and then powering your drives for safetys sake. This would also prevent the usb from reseting your drives if that is the problem.

[neilw20]

Look www.usb.org and read the standard.
The power available, may not be as expected, and when expected.
In certain cases laptops, for example may turn off the USB power when a lack complex communications have deemed that the power should be off.
Short of a properly designed interface, power may be unreliable, depending on the computer and BIOS design.
Buy a plugpack and you will never have the problem.