PIC 3 show a closer look of the AC Adapter. Its current rating is 500mA. It has a selector switches for output voltage and output polarity. The switch settings are not clearly shown, but it is set at 12V. Any 12V (300-500 mA) adapter will work for this project. The polarity switch of the adapter, if any, may be set at one position but IT MUST REMAIN IN THE SAME POSITION DURING USE. It is only important to identify the polarity at the end of the long wire.