5.3 Seven-Segment Display

5.3.1 What is a Seven-Segment Display?

A seven-segment display is an electronic display consisting of seven individual LED segments arranged to form numbers and some letters.

 

The seven segments are normally named:

The segments are:

a, b, c, d, e, f, and g

By switching different segments ON and OFF, the display can produce different numbers.

5.3.2 Displaying Numbers

For example, to display 0, segments:

a, b, c, d, e, f

are ON, while g is OFF.

To display 8, all seven segments are ON.

5.3.3 Types of Seven-Segment Displays

There are two common types:

Common Cathode

All LED cathodes are connected together.

The common terminal is normally connected to GND.

A segment is illuminated by applying a HIGH signal to that segment.

Common Anode

All LED anodes are connected together.

The common terminal is normally connected to the positive supply.

A segment is illuminated by applying a LOW signal to that segment.

5.3.4 Seven-Segment Display Connection

A basic connection can contain:

Arduino → Resistors → LED segments

A resistor is normally used with each LED segment to limit current.

5.3.5 Simple Seven-Segment Example

For a common-cathode display:

int a = 2;

int b = 3;

int c = 4;

int d = 5;

int e = 6;

int f = 7;

int g = 8;

 

void setup() {

  pinMode(a, OUTPUT);

  pinMode(b, OUTPUT);

  pinMode(c, OUTPUT);

  pinMode(d, OUTPUT);

  pinMode(e, OUTPUT);

  pinMode(f, OUTPUT);

  pinMode(g, OUTPUT);

}

 

void loop() {

 

  // Display number 8

  digitalWrite(a, HIGH);

  digitalWrite(b, HIGH);

  digitalWrite(c, HIGH);

  digitalWrite(d, HIGH);

  digitalWrite(e, HIGH);

  digitalWrite(f, HIGH);

  digitalWrite(g, HIGH);

 

}

5.3.6 Seven-Segment Applications

Seven-segment displays are commonly used in:

• Digital clocks
• Counters
• Calculators
• Electronic meters
• Timers
• Scoreboards
• Temperature displays
• Number displays
• Industrial control equipment

Advantages

• Simple construction
• Easy to understand
• Easy to control
• Good for displaying numbers
• Relatively inexpensive
• Easy to read from a distance

Disadvantages

• Limited character representation
• Cannot easily display complex graphics
• Requires several control lines unless a driver is used
• Multiple digits require additional hardware or multiplexing