We are trying to use a spare USB3 port on a PC to drive an LED as an indication that the PC is powered ON. The PC has a power on LED but it's in a rack and is not visible to the operator. We have connected the LED across the USB3 VBUS and USB 3 GND pins and have discovered that it doesn't work. We believe however that it would work with a USB2 port (as I have found numerous articles telling me how to get 5VDC from a USB 2 port by simply connecting the red and black wires to whatever we wanted to power). Can anyone please confirm that USB3 operates differently ? Our tests would suggest that the power isn't available unless the PC detects the presence of a device connected across the data pins. If this is the case can someone please advise if there is a simple way to trick it to believe that there is a something there ?
In reply to Why not to use a better by Michal Podmanický
Thanks for your response. The computer is a sealed mission computer so we have no way to access the internals and only can make use of the pins that are available on the interface connectors. The USB 3 port is the only thing we can potentially make use of.
And advice:
Discover if your PC_Led- pin is Gnd, I draw this schematic as an example only.
If you can be safe to not damage your PC, use an optocoupler to sense PC_Led voltage.
In reply to And advice: by Michal Podmanický
Thanks for your response. The computer is a sealed mission computer so we have no way to access the internals and only can make use of the pins that are available on the interface connectors. The USB 3 port is the only thing we can potentially make use of.
PC USB3 port generelly provide power without any additional detection. However, what is the connector type? Connectors have different protocols such as type C.
Michal Podmanický
Joined November 06, 2020 64Friday at 08:06 PM
Why not to use a better source of information about runnig PC, like power ON Led.