See a preview of the board and buy the parts from the kitspace.org page.

A power switch using a push button. It turns on with a single press and only turns off when you hold the button down. This could be used to get functionality similar to most laptops where a single press when on will initiate a "soft" shutdown but you can force a "hard" shutdown by holding it down.

The circuit is from this article.

The board is my own design and features:

• Standard 0.1" spacing, fits neatly onto a breadboard
• On-board button (and pins to connect your own)
• Two LEDs indicate input and output power
• Configurable to automatically turn on or stay off on initial power through a solder jumper (auto-off is the default)
• Can switch 3-20V and up to 4A