Removing Vss on USB cable to controller

I want to avoid that the Nano/Uno/Mega board draw current from the PC, since I use an external power source.

I assume it will not disturb the communication between the Arduino and the PC if the Vcc is cut, or? So, before doing so I want to ask here if is it OK to cut the Vcc wire.

It is perfectly OK to cut the 5V wire in the USB cable itself as long as you don't need the voltage that it supplies. Why do you want to do this ?

On the Nano it is no problem as there is a diode between the USB input and the 5 V line - if the external 5 V is the same or more than the USB voltage, the diode will not be conducting.

UKHeliBob:
It is perfectly OK to cut the 5V wire in the USB cable itself as long as you don't need the voltage that it supplies. Why do you want to do this ?

My PC sometime complain about high load on the USB port - even if I have an active USB hub. When it complain it freeze and I have to use the Reset button to restart it.

I do not understand why, since the controller + other components have separate power supply.

It sounds like there is more wrong than just the current drawn by the Arduino

UKHeliBob:
It sounds like there is more wrong than just the current drawn by the Arduino

It only happens a few times.

Agree - Window$ should not react in this way. Anyway - I also want to make sure the power to the controller comes from the power source - not the computer.

I also want to make sure the power to the controller comes from the power source - not the computer.

OK, cut the 5V line in cable but check which wire is 5V. As in all good "defuse the bomb" scenarios it may not be the red one !

thehardwareman:
My PC sometime complain about high load on the USB port - even if I have an active USB hub. When it complain it freeze and I have to use the Reset button to restart it.

If by “an active USB hub”, you mean one that is powered with a separate 5 V supply, then that is the same problem cited when you are advised not to connect a 5 V regulated supply to the UNO “5V” terminal when the USB is connected to a PC. This does not apply to a Nano, no such problem.

Most powered USB hubs (even “branded” ones) connect all output 5 V lines together with the 5 V from the external supply and the USB input and thus may “backfeed” the PC’s USB port causing that problem and possibly permanent damage. :astonished:

So there is a warning about doing this on the UNO but it is somewhat surprising that such a problem is not frequently reported with the powered USB hubs which one would expect to be far more commonly used than Arduino UNOs. :roll_eyes: