A 7-segment display is a device that can display numerals and letters. It's made up of seven LEDs connected in parallel. Different letters/numbers can be shown by connecting pins on the display to the power source and enabling the related pins, thus turning on the corresponding LED segments. In this lesson let's learn how to display specific characters on it.

Step 1: Components

- Arduino Uno board * 1

- USB cable * 1

- 7-segment display (Common Cathode) *1

- Resistor (220Ω) * 8

- Breadboard * 1

- Jumper wires

Step 2: Principle

A 7-segment display is an 8-shaped component which packages 7 LEDs. Each LED is called a segment – when energized, one segment forms part of a numeral (both decimal and hexadecimal) to be displayed. An additional 8th LED is sometimes used within the same package thus allowing the indication of a decimal point (DP) when two or more 7-segment displays are connected together to display numbers greater than ten.

Each of the LEDs in the display is given a positional
segment with one of its connection pins led out from the rectangular plastic package. These LED pins are labeled from "a" through to "g" representing each individual LED. The other LED pins are connected together forming a common pin. So by forward biasing the appropriate pins of the LED segments in a particular order, some segments will brighten and others stay dim, thus showing the corresponding character on the display.

The common pin of the display generally tells its type. There are two types of pin connection: a pin of connected cathodes and one of connected anodes, indicating Common Cathode (CC) and Common Anode (CA). As the name suggests, a CC display has all the cathodes of the 7 LEDs connected when a CA display has all the anodes of the 7 segments connected.

Common Cathode 7-Segment Display

In a common cathode display, the cathodes of all the LED segments are connected to the logic "0" or ground. Then an individual segment (a-g) is energized by a "HIGH", or logic "1" signal via a current limiting resistor to forward bias the anode of the segment.

Common Anode 7-Segment
Display

In a common anode display, the anodes of all the LED segments are connected to the logic "1". Then an individual segment (a-g) is energized by a ground, logic "0" or "LOW" signal via a current limiting resistor to the cathode of the segment.

Step 3: The Schematic Diagram

Step 4: Procedures:

In this experiment, connect each of pin a-g of the 7-Segment Display to one 220ohm current limiting resistor respectively and then to pin 4–11. GND connects to GND. By programming, we can set one or several of pin4-11 as High level to light up the corresponding LED(s).

Step 1:

Build the circuit.

Step 2:

Download the code from https://github.com/primerobotics/Arduino

Step 3:

Upload the sketch to the Arduino Uno board

Click the Upload icon to upload the code to the control board.

If "Done uploading" appears at
the bottom of the window, it means the sketch has been successfully uploaded.

You should now see the 7-segment display from 0 to 9 and then A to F, back and forth.

Step 5: Code

//7-SegmentDisplay
//You should now
see the 7-segment display cycle from 0 to F
//Email:
info@primerobotics.in
//Website:www.primerobotics.in
const int a=7; //a
of 7-segment attach to digital pin 7
const int b=6; //b
of 7-segment attach to digital pin 6
const int c=5; //c
of 7-segment attach to digital pin 5
const int d=11;//d
of 7-segment attach to digital pin 11
const int e=10;//e
of 7-segment attach to digital pin 10
const int f=8;//f
of 7-segment attach to digital pin 8
const int g=9;//g
of 7-segment attach to digital pin 9
const int
dp=4;//dp of 7-segment attach to digital pin 4
void setup()
{
  //loop over thisPin from 4 to 11 and set them
all to output
  for(int thisPin = 4;thisPin <=
11;thisPin++)
  {
    pinMode(thisPin,OUTPUT);
  }
  digitalWrite(dp,LOW);//turn the dp of the
7-segment off 
}
void loop()
{
  digital_1();//diaplay 1 to the 7-segment
  delay(1000);//wait for a second
  digital_2();//diaplay 2 to the 7-segment
  delay(1000); //wait for a second
  digital_3();//diaplay 3 to the 7-segment
  delay(1000); //wait for a second
  digital_4();//diaplay 4 to the 7-segment
  delay(1000); //wait for a second
  digital_5();//diaplay 5 to the 7-segment
  delay(1000); //wait for a second
  digital_6();//diaplay 6 to the 7-segment
  delay(1000); //wait for a second
  digital_7();//diaplay 7 to the 7-segment
  delay(1000); //wait for a second
  digital_8();//diaplay 8 to the 7-segment
  delay(1000); //wait for a second
  digital_9();//diaplay 8 to the 7-segment
  delay(1000); //wait for a second
  digital_A();//diaplay 8 to the 7-segment
  delay(1000); //wait for a second
  digital_b();//diaplay 8 to the 7-segment
  delay(1000); //wait for a second
  digital_C();//diaplay 8 to the 7-segment
  delay(1000); //wait for a second
  digital_d();//diaplay 8 to the 7-segment
  delay(1000); //wait for a second
  digital_E();//diaplay 8 to the 7-segment
  delay(1000); //wait for a second
  digital_F();//diaplay 8 to the 7-segment
  delay(1000); //wait for a second
}
void digital_1(void)
//diaplay 1 to the 7-segment
{
  digitalWrite(c,HIGH);//turn the c of the
7-segment on
  digitalWrite(b,HIGH);//turn the b of the
7-segment on
  for(int j = 7;j <= 11;j++)//turn off the
others
    digitalWrite(j,LOW);
}
void
digital_2(void) //diaplay 2 to the 7-segment
{
  digitalWrite(b,HIGH);
  digitalWrite(a,HIGH);
  for(int j = 9;j <= 11;j++)
    digitalWrite(j,HIGH);
  digitalWrite(c,LOW);
  digitalWrite(f,LOW);
}
void
digital_3(void) //diaplay 3 to the 7-segment
{
  unsigned char j;
  digitalWrite(g,HIGH);
  digitalWrite(d,HIGH);
  for(j=5;j<=7;j++)
    digitalWrite(j,HIGH);
  digitalWrite(f,LOW);
  digitalWrite(e,LOW);
}
void
digital_4(void) //diaplay 4 to the 7-segment
{
  digitalWrite(c,HIGH);
  digitalWrite(b,HIGH);
  digitalWrite(f,HIGH);
  digitalWrite(g,HIGH);
  digitalWrite(a,LOW);
  digitalWrite(e,LOW);
  digitalWrite(d,LOW);
}
void
digital_5(void) //diaplay 5 to the 7-segment
{
  unsigned char j;
  for(j = 7;j <= 9;j++)
    digitalWrite(j,HIGH);
  digitalWrite(c,HIGH);
  digitalWrite(d,HIGH);
  digitalWrite(b,LOW);
  digitalWrite(e,LOW);
}
void
digital_6(void) //diaplay 6 to the 7-segment
{
  unsigned char j;
  for(j = 7;j <= 11;j++)
    digitalWrite(j,HIGH);
  digitalWrite(c,HIGH);
  digitalWrite(b,LOW);
}
void digital_7(void)
//diaplay 7 to the 7-segment
{
  unsigned char j;
  for(j = 5;j <= 7;j++)
    digitalWrite(j,HIGH);
  for(j = 8;j <= 11;j++)
    digitalWrite(j,LOW);
}
void
digital_8(void) //diaplay 8 to the 7-segment
{
  unsigned char j;
  for(j = 5;j <=11;j++)
   
digitalWrite(j,HIGH);
}
void
digital_9(void) //diaplay 9 to the 7-segment
{
  unsigned char j;
  for(j = 5;j <=9;j++)
    digitalWrite(j,HIGH);
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
}
void
digital_A(void) //diaplay A to the 7-segment
{
  unsigned char j;
  for(j = 5;j <=10;j++)
    digitalWrite(j,HIGH);
  digitalWrite(d,LOW);
}
void
digital_b(void) //diaplay b to the 7-segment
{
  unsigned char j;
  for(j = 7;j <=11;j++)
    digitalWrite(j,HIGH);
  digitalWrite(a,LOW);
  digitalWrite(b,LOW);
}
void
digital_C(void) //diaplay C to the 7-segment
{
  digitalWrite(a,HIGH);
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,HIGH);
  digitalWrite(e,HIGH);
  digitalWrite(f,HIGH);
  digitalWrite(g,LOW);
}
void
digital_d(void) //diaplay d to the 7-segment
{
  unsigned char j;
  digitalWrite(a,LOW);
  digitalWrite(f,LOW);
  digitalWrite(b,HIGH);
  digitalWrite(c,HIGH);
  digitalWrite(j,HIGH);
  for(j = 9;j <=11;j++)
    digitalWrite(j,HIGH);
}
void
digital_E(void) //diaplay E to the 7-segment
{
  unsigned char j;
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  for(j = 7;j <=11;j++)
    digitalWrite(j,HIGH);
}
void
digital_F(void) //diaplay F to the 7-segment
{
  unsigned char j;
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,LOW);
  for(j = 7;j <=10;j++)
    digitalWrite(j,HIGH);
}