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# 7 Segment Display

If your Arduino application only needs to display numbers, consider using a seven-segment display. The seven-segment display has seven LEDs arranged in the shape of number eight. They are easy to use and cost effective. The picture below shows a typical seven-segment display.

Seven segment displays are of two types: common anode and common cathode. The Internal structure of both types is nearly the same. The difference is the polarity of the LEDs and common terminal. In a common cathode seven-segment display (the one we used in the experiments), all seven LEDs plus a dot LED have the cathodes connected to pins 3 and pin 8. To use this display, we need to connect GROUND to pin 3 and pin 8 and, and connect +5V to the other pins to make the individual segments light up. The following diagram shows the internal structure of common-cathode seven-segment display:

anode display is the exact opposite. In a common-anode display, the positive terminal of all the eight LEDs are connected together and then connected to pin 3 and pin 8. To turn on an individual segment, you ground one of the pins. The following diagram shows the internal structure of the common-anode seven-segment display.

The seven segment are labelled a-g, with the dot being “dp,” as shown in the figure below:

To display a particular number, you turn on the individual segments as shown in the table below:

 Digit    gfedcba abcdefg a b c d e f g 0             0×3F 0×7E on on on on on on off 1             0×06 0×30 off on on off off off off 2             0×5B 0×6D on on off on on off on 3             0×4F 0×79 on on on on off off on 4             0×66 0×33 off on on off off on on 5             0×6D 0×5B on off on on off on on 6             0×7D 0×5F on off on on on on on 7             0×07 0×70 on on on off off off off 8             0×7F 0×7F on on on on on on on 9             0×6F 0×7B on on on on off on on A             0×77 0×77 on on on off on on on B             0×7C 0×1F off off on on on on on C             0×39 0×4E on off off on on on off D             0×5E 0×3D off on on on on off on E             0×79 0×4F on off off on on on on F             0×71 0×47 on off off off on on on

Interfacing with Arduino

The pins of seven-segment display are connected to Arduino pins 2-9, as shown in the table below. Common pins (pin 3 and pin 8) are connected to GND and dp is left unconnected, because it is not used in this experiment

 Seven segment pins Arduino pins Wire Color 1(e) 6 orange 2(d) 5 white 3,8(COM) GND n/a c 4 yellow 5(dp) – 6(b) 3 red 7(a) 2 blue 9(f) 7 cyan 10(g) 8 green

# Code

void setup()

{

// define pin modes

pinMode(2,OUTPUT);

pinMode(3,OUTPUT);

pinMode(4,OUTPUT);

pinMode(5,OUTPUT);

pinMode(6,OUTPUT);

pinMode(7,OUTPUT);

pinMode(8,OUTPUT);

}

void loop()

{

// loop to turn leds od seven seg ON

for(int i=2;i<9;i++)

{

digitalWrite(i,HIGH);

delay(600);

}

// loop to turn leds od seven seg OFF

for(int i=2;i<9;i++)

{

digitalWrite(i,LOW);

delay(600);

}

delay(1000);

}

## Applications of Seven Segment Displays

• The applications of seven segments are mostly in digital calculators, electronic meters, digital clocks, odometers, digital clocks, clock radios, etc.
• Today most of the 7 segment applications are using LCDs, because of low current consumption.