How to stop Arduino from drawing power through USB I'm working on an embedded project, where I use arduinos as a "sensor shield" for RaspberryPi (I have model B).

The problem is, that the RaspberryPi's USB port is not powerfull enough to drive WiFi adapter and arduino with sensors. The solution is easy, I will power the sensors externally, not through the RPi. 

But I was wondering, is it possible to power whole Arduino externally (through Vin) and use the USB only for serial communication.

To clarify, I know how to solve my problem - use some other mean of communication, than USB - GPIO serial, I2C, wireless, etc... I'm just interested if the whole thing will work, with USB cable which has 5V lead cut, for example.

The main issue I can see with this is, that the USB&lt;->Serial chip is powered through USB only, then it will now work.
If you provide power to the Arduino through Vin this will disconnect USB power through the MOSFET switch.