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Interface a Seven Segment LED display to an Arduino Uno R3
For many Embedded system applications, there is no need to use an expensive LCD for display purposes, even a simple Seven Segment display can do the work.
Yes, for many Arduino and Embedded system applications if your aim is to display just the numbers, then you should most probably use a Cheaper 7 segment display.
You can lower down the cost of your project by using a 7 Segment display instead of an LCD display.
Moreover, Using a 7 segment display is much easier than an LCD.
Fig.1 and 2 displays the image of a Seven 7 segment LED display.
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| Fig. 1 Front view of 7 Segment Display |
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| Fig.2 Side View of 7 Segment display |
In the common cathode display (generally used) the cathodes of all seven LEDs and the DP (decimal point) are made common and connected to pin 3 and 8 of the LED display. In order to use the LED display effectively, we will have to connect ground to pin 3 and pin 8 and connect +5v supply to other pins to light up the LED of the corresponding pin i.e to light up the individual LEDs.
Fig. 3 shows the internal structure of the common cathode LED display.
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| Fig. 3 Internal Structure Common Cathode 7 Segment LED Display |
The common anode display is obtained by reversing the polarity, it is the complete opposite of the common cathode display. In the common anode display, the anodes of all seven LEDs and the DP (decimal point) are made common and connected to pin 3 and 8 of the LED display. In order to use the LED display effectively, we will have to connect +5v to pin 3 and pin 8 and connect Ground to other pins to light up the LED of the corresponding pin i.e to light up the individual LEDs.
Fig. 4 shows the internal structure of the common anode LED display.
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Fig. 4 Internal Structure of Common Anode 7 Segment LED Display |
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| Fig. 5 SSD Configuration of 7 Segment LED Display |
Table representing which LED should be ON and which should be OFF for a particular Digit in case of the common cathode display.
Digit | a | b | c | d | e | f | g | dp |
0 | On | On | On | On | On | On | Off | Off |
1 | Off | On | On | Off | Off | Off | Off | Off |
2 | On | On | Off | On | On | Off | On | Off |
3 | On | On | On | On | Off | Off | On | Off |
4 | Off | On | On | Off | Off | On | On | Off |
5 | ||||||||
6 | Off | |||||||
7 | ||||||||
8 | ||||||||
9 | ||||||||
A | ||||||||
B | ||||||||
C | ||||||||
D | ||||||||
E | ||||||||
F |
You can determine these states by the image shown below.
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| Fig. 6 shows the LED structure of 7 Segment LED Display. |
Experiment No. 1
In Experiment No. 1 we will simply turn on and off the LEDs to get familiar with the working of a 7 segment display.
Components Required:
1. Arduino Uno R3 Board x 1
2. 7 Segment LED Display x 1 (Common Cathode)
3. 220 Ohm Resistors x 7
4. Jumper Wires
5. BreadBoard x 1
Circuit Diagram:
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| Fig. 7 Pin Diagram of 7 Segment Display |
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| Fig. 8 Circuit Diagram for Experiment 1 |
Arduino Code :
int a= 2; //Connect a to Pin 2
int b = 3; //Connect b to Pin 3
int c = 4; //Connect c to Pin 4
int d = 5; //Connect d to Pin 5
int e = 6; //Connect e to Pin 6
int f = 7; //Connect f to Pin 7
int g = 8; //Connect g to Pin 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()
{
//Loop to turn on the LEDs of 7 segment display
for(int i=2;i<9;i++)
{
digitalWrite(i,HIGH);
delay(500); //delay for 0.5 seconds
}
//Loop to turn off the LEDs of 7 Segment Display
for(int i=2;i<9;i++)
{
digitalWrite(i,LOW);
delay(500); //delay for 0.5 seconds
}
delay(1000);}
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