Common Anode 7 Segment Display

A common anode 7 Segment LED Display is a 7 segment display in which all the anode leads of the LEDs are wired together.

LED Types

When it comes to how 7 segment displays are wired, there are 3 types. There are either common anode LED displays or common cathode LED displays.

LED Leads

To better understand this topic, LEDs are 2-lead devices, meaning they have 2 leads. One lead is the anode and the other lead is the cathode. The anode is the side which receives positive voltage and the cathode is the side which is connects to the negative voltage or ground of the circuit. This is shown below:

In a common anode 7 segment display, all of the anode pins are tied together, meaning they are common.

Below is a typical LED display, with each LED segment labeled with an alphabetical character.

This is how the seven segment display will appear wired up in a common anode setup:

With a common anode display, all the anodes are tied together, so they're common. Once you place voltage on the positive anode pin, they will all have voltage across them. You turn on an LED when you connect it the cathode pin to ground. Those LEDs which you connect to ground turn on. Those which you leave open (unconnected to ground) stay shut off. This is how common anode LED displays work.