In any electronic product or project there is always a need for a source of power for the system to work. This is called a power supply. To get power hassle-free to the power lines of a breadboard can be a challenge, you will need a convenient and safe way to get either a regulated 5V DC or 3.3V DC depending on your application  on your breadboard power rails. In this project we are going to design step by step a simple  Breadboard power supply that takes power from a 6 to 15V DC power supply and outputs a selectable 5V or 3.3V regulated voltage using a switch. This board can be easily inserted into a breadboard using a .1" (0.254 cm) headers mounted on the bottom of the PCB. Pins labeled VCC and GND plug directly into the power lines of a breadboard.