I need to select/choose a wall wort to power an Arduino Duemilanove, and I went up to Radio Shack earlier today to find an appropriate power supply, by selecting one based on the criteria listed in this guide. The guide states for a 2.1mm plug, but Radio Shack had measurements for inner and outer diameter, so I was not sure what measurement this 2.1mm plug statement was referring to. :-l (inside maybe?)
Also, when I got home, I decide to look through my junk drawer. I discovered two possible candidates to power the Arduino. One is a Radio Shack power supply with a Cat No: 43-742/743/744/747 The output is listed as follows, OUTPUT AC 9V 780mA but there is no labeling on the power supply describing whether or not it is center positive or not. :-l
The second candidate is US Robotics P/N 1.015.1286 with an output as follows, OUTPUT: 9V AC 1000mA. As stated with the first power supply listed there is no markings on the power supply stating whether it is center positive or center negative. If you can shed some light on this situation I would appreciate it.