powering arduino and gsm separately

i need my arduino to communicate serially with the computer, so the usb cable will always be connected to computer. i tried to power gsm shield and arduino though this usb connection but the gsm shield wont register network, however when the gsm is powered with separate 9V delivering 2A will work.

9my question is that can i just power the gsm shield (which is connect to arduino) with 9V source while at the same time the arduino is connected to computer?, I am asking because i read somewhere that powering the two at the same time is not advisable

I have connected my computer and power to my arduino before. Most of the time it is fine. You do take a bit of a risk, but as long as you do not connect more than five volts to the USB port you should be fine.

Computers have built in protection. If there is too much power at a usb port the computer will shut down and should be fine. Overall I recommend being careful. A diode or two would not be a bad idea.

Lafred: I have connected my computer and power to my arduino before. Most of the time it is fine. You do take a bit of a risk, but as long as you do not connect more than five volts to the USB port you should be fine.

Computers have built in protection. If there is too much power at a usb port the computer will shut down and should be fine. Overall I recommend being careful. A diode or two would not be a bad idea.

thank you for the advice