powering arduino uno from a seperate supply whilst using serial monitor

hi, I need to power a project involving an arduino and also read the serial monitor output. The laptop used to read the data will not have enough power via the USB to power the project and I was wondering if anyone has any suggestions. My first thoughts were to split the USB cable and use the two data lines to the laptop and power the arduino via a stabilised 9v supply to the power socket, although it may require the 0v line to be commoned. Any thoughts would be gratefully recieved as I'm not too keen on killing either the laptop or the arduino yet.

Just supply the Uno with 9V to the power socket - it automatically derives its power from that source by preference. Don't muck about with USB cables.

Never, ever, would you do anything other than ensure the grounds are commoned.

Paul__B:
Just supply the Uno with 9V to the power socket
Don't muck about with USB cables.

I find it perfectly fine to connect to, program, monitor and debug an Arduino via USB while it is simultaneously powered via the power connector. It is slightly annoying that the standard USB/serial connection sends resets to the Arduino every time the serial port is opened by a terminal window or the serial monitor in the IDE. Sometimes I just want to attach, watch, and detach from the running Arduino's serial, without resetting it.

gardner:
It is slightly annoying that the standard USB/serial connection sends resets to the Arduino every time the serial port is opened by a terminal window or the serial monitor in the IDE. Sometimes I just want to attach, watch, and detach from the running Arduino's serial, without resetting it.

You can inhibit the 'reset on serial connection' function temporarily or permanently, if you want. See descriptions of using an Arduino as ISP for details.

gardner:
It is slightly annoying that the standard USB/serial connection sends resets to the Arduino every time the serial port is opened by a terminal window or the serial monitor in the IDE. Sometimes I just want to attach, watch, and detach from the running Arduino's serial, without resetting it.

There is a break on the Uno PCB (R3 at least) to disable that. If you find a really small switch, you might be able to solder it over the break.

On the other hand you can just put a cap between RST and GND to avoid cutting and soldering.