Please help me out.
I am trying to use the Arduino Uno V3 to work with external power supply of around 5v.
However, after uploading the code into the Arduino board, it seems the Arduino does not work at all with my external power supply.
The green LED is light but the L LED keeps blinking quickly which seems a bit weird.
The code should be ok cause it works perfectly when the USB is connected.
Could anyone give me any suggestions?
Thank you all.