How to Build a Selectable Power Source [Part 1]

July 5, 2013

Disclaimer: I am not an electrical engineer. Do this at your own risk!

I hate waste. In fact, the entire driver for this little project was because I can’t stand to see batteries be needlessly consumed. Is there really a need for a motorized baby swing to run on AA’s? I bet for 90% of its uses, it will be placed inside; most likely conveniently positioned right next to an outlet in a comfortable 73 degrees Fahrenheit.

Surprisingly, I have not found any great tutorials on how to build a circuit that works via a portable power source such as a couple of AA’s or by another means, such as using an AC/DC adaptor (wall wart).

The premise is simple: a switch to select one of two power sources: a battery pack or a wall plug.

Schematic Schematic

An image of a tested design will be shown in part 2.