Green power LED is blinking

Development Tools IDE 1.x
1

Hi
I have a new Arduino Uno (replaced with a ATmega 168). I tried to connect an external power supply for a stepper circuit (like this: http://arduino.cc/en/uploads/Tutorial/Unipolar_bb.png).

Now when I plug in a 12V, 2A adapter the "green power LED" is blinking!? Does anyone knows what it means?

thanks a lot

2

The wiring diagram you pointed to has the external supply connected to the 5V pin on the Arduino. If you are using a higher voltage you should connect it to Vin, not 5V. Perhaps that is what the light is trying to tell you.