Direct current (DC) specifies a unidirectional flow of electrons; that is they flow in one direction only.

The simple nature of direct current lends itself well to creating digital logic circuits, because it can represent binary 1 when on (within a given voltage range), and binary 0 when off (at ground, or 0V). It’s also the type of current that batteries generate.

Because DC is used as the primary type of current in digital logic circuits, most of this tutorial will focus on DC circuits.

Direct curent is also used in long distance, high power, electrical transmission lines (usually >250kV) because of lower electrical losses.

Netduino provides two power rails that supply 5V and 3.3V direct current. They can be found on the power header:

DC Power Symbols

A general DC power source symbol looks like the following:

DC Power Symbol; a Circle with a Plus and Minus Sign

But many specific power sources have their own symbols, such as batteries, as we’ll see later.

Let’s examine AC next.

Next - Alternating Current