Hello,
I disconnected the usb , and I pluged in with 12v. the sketch doesn't work.
how can I resolve that problem.
What board are you using?
Please post the code you've uploaded to it?
What (if anything) is connected to the Arduino?
With the 12v power connected (to Vin or barrel jack, I hope), what voltage do you measure between ground and 5v pin, assuming you have a multimeter?
Please answer all questions, and put code within code tags (click the </> button )