The Atmel AVR ONE! must be powered by an external power supply (provided) which is capable of supplying 15W at 12V DC. The polarity of the DC jack is positive-centre. When powering up the AVR ONE!, the power LED should illuminate immediately. If the LED does not light up, check that the correct power supply is being used, or check that the polarity is positive-centre if a different power supply is being used.