So I've been helping my daughter with her science/engineering fair project. The project uses an arduino uno with a servo to automatically feed the dog twice a day. She started with a Futaba S3003 ...

You can also go the 9v battery route plugged into the on-board regulator of the Arduino but the low mAh rating of a 9v ... Also with AA cells you can share one charger among many battery powered ...

Arduino Measures Remaining Battery Power With Zero Components, No I/O Pin. 22 Comments . by: ... but he provides example Arduino code showing how handy this can be for battery-powered projects.