This article covers following content:
- 1: Introduction to Seven Segment
- 2: Seven Segment Pinout
- 3: Types of Seven Segment
- 4: How to Check a Seven Segment is Common Anode or Common Cathode
- 5: Interfacing Seven Segment with ESP32 and Push Button
- 5.1: Schematic
- 5.2: Hardware
- 5.3: Installing the Required Library
- 6: Designing a Seven Segment 0 to 9 Counter Using ESP32 and Push Button
- 6.1: Code
- 6.2: Output
1: Introduction to Seven Segment
A seven-segment can display numerical information using a microcontroller program. It consists of seven individual segments, each of which can be lit up or turned off independently to create various numerical characters.
A seven-segment display works by illuminating different combinations of its seven segments to display numerical characters. Each segment is controlled by an individual pin, which can be turned on or off to create the desired numerical character. When the segments are illuminated in the correct combination, the numerical character is visible to the viewer.
When using an ESP32 microcontroller to control a seven-segment display, the ESP32 sends signals to the specific pins on the seven-segment display, telling it which segments to turn on or off in order to display a specific numerical character.
2: Seven Segment Pinout
The seven-segment display typically has 10 pins, with one pin for each segment, one for the decimal and two common pins. Here is a table of the typical pinout:
| Pin Number | Pin Name | Description |
| 1 | b | Top Right LED Pin |
| 2 | a | Topmost LED Pin |
| 3 | VCC/GND | GND/VCC Depends on Configuration |
| 4 | f | Top Left LED Pin |
| 5 | g | Middle LED Pin |
| 6 | dp | Dot LED Pin |
| 7 | c | Bottom Right LED Pin |
| 8 | VCC/GND | GND/VCC Depends on Configuration |
| 9 | d | Bottom LED Pin |
| 10 | e | Bottom Left LED Pin |
Each segment is labeled as a, b, c, d, e, f and g. The common pin is typically used to control all of the segments at once. The common pin is either active low or active high depending on the display.
3: Seven Segment Types
Seven segment can be categorized in 2 types:
- Common Cathode
- Common Anode.
1: In a common cathode all negative LED segment terminals are connected.
2: In a common anode seven segment all positive LED segment terminals are connected.
4: How to Check a Seven Segment is Common Anode or Common Cathode
To check the type of seven segments we just need a simple tool – Multimeter. Follow the steps to check type of seven segment display:
- Hold the seven-segment display firmly in hand and identify pin 1 using the pinout explained above.
- Take a multimeter. Assume a red probe for positive (+) and black probe of a multimeter for negative (-).
- Set multimeter to continuity test.
- After that check working of the meter can be checked by touching both positive and negative probes. A beep sound will be produced if the meter is functioning properly. Otherwise replace the batteries in your multimeter with a new one.
- Put black probe on pin 3 or 8 of the multimeter. Both these pins are common and internally connected. Select any one pin.
- Now put the red or positive probe of the multimeter on other pins of seven-segments like 1 or 5.
- After touching the red probe if any segment glows the seven segment is a common cathode.
- Interchange the multimeter leads if no segment glows.
- Now connect the red lead to pin 3 or 8.
- After that put black or negative lead on the remaining pins of the display. Now if any of the segments of the display glows then the seven segments are common anode. As in COM anode all segments’ positive pins are common, and remaining are joined with negative supply.
- Repeat steps to check all other display segments one by one.
- If any of the segments does not glow, then it will be faulty.
Here is a reference image for a seven-segment test using a multimeter. We can see red probe is at COM pin 8 and black is at segment pin so we are using Common Anode seven segment:
5: Interfacing Seven Segment with ESP32 and Push Button
To interface a seven-segment display with an ESP32, you will need the following materials:
- An ESP32 microcontroller
- A seven-segment display
- Push Button
- A breadboard
- Jumper wires
ESP32 interfaces with seven segment displays in several simple steps.
1: First, connect the seven-segment display to the breadboard.
2: Next, connect the ESP32 with a seven-segment display using wires. The ESP32 will be used to send signals to the seven-segment display, telling it which segments to turn on or off.
3: Now write an Arduino code for ESP32 in IDE. The program will need to send signals to the specific pins on the seven-segment display, telling it which segments to turn on or off in order to display a specific numerical character.
4: The Arduino IDE provides a library using which we can easily control the state of each segment with simple commands.
5: Once the program is written and uploaded to the ESP32, the seven-segment display should start displaying the numerical characters as per the program.
5.1: Schematic
To design a push button counter using seven segments first we need to design the circuit given below and connect seven segments with push button and ESP32. Using the below reference schematic connects your ESP32 board with a seven segment display.
Following is the pinout table for ESP32 connection with a single seven segment display. A push button is also connected at D23:
| Pin Number | Pin Name | ESP32 Pin |
| 1 | b | D2 |
| 2 | a | D15 |
| 3 | COM | GND/VCC Depends on Configuration – Common Cathode/Anode |
| 4 | f | D19 |
| 5 | g | D21 |
| 6 | dp | Dot LED Pin |
| 7 | c | D4 |
| 8 | COM | GND/VCC Depends on Configuration – Common Cathode/Anode |
| 9 | d | D5 |
| 10 | e | D18 |
5.2: Hardware
Below image shows the hardware of ESP32 connect with push button and seven segment:
5.3: Installing the Required Library
After connecting seven segments we need to install a library in the Arduino IDE. Using this library, we can easily program ESP32 with seven segments.
Go to Library manager search for SevSeg library and install it in Arduino IDE.
6: Designing a Seven Segment 0 to 9 Counter Using ESP32 and Pushbutton
To design a real time counter from 0 to 9 using ESP32 a push button is needed. Pushbutton will send a signal at the digital pin of ESP32 which will display a digit on seven segments. Every time the button is pressed one digit is incremented on seven segments.
6.1: Code
Open IDE and connect ESP32. After that upload the given seven segment code to ESP32:
SevSeg sevseg; /*Seven Segment Variable*/
int state1; /*Variable to store pushbutton state*/
int count=0; /*Variable that will store counter value*/
#define button1 23 /*ESP32 pin for pushbutton */
void setup() {
pinMode(button1,INPUT_PULLUP); /*Assign button as input*/
byte sevenSegments = 1; /*Number of seven segments we are using*/
byte CommonPins[] = {}; /*Define common pins*/
byte LEDsegmentPins[] = {15, 2, 4, 5, 18, 19, 21}; /*ESP32 digital pins defined for seven segment sequence pin a to g*/
bool resistorsOnSegments = true;
sevseg.begin(COMMON_ANODE, sevenSegments, CommonPins, LEDsegmentPins, resistorsOnSegments);/*configuration of the seven-segment */
sevseg.setBrightness(80); /*Brightness of seven segment*/
}
void loop() {
state1=digitalRead(button1); /*Read pushbutton state*/
if (state1== LOW){ /*LOW state when pushup button is pressed*/
count++; /*Increase display value by 1*/
sevseg.setNumber(count); /*display the count value*/
sevseg.refreshDisplay(); /*refresh 7-segment */
delay(200);
}
if(count == 10)
{
count = 0;
}
sevseg.setNumber(count);/*display the count value*/
sevseg.refreshDisplay();/* refresh 7-segment*/
}
Code started by calling the SevSeg library. Here we created two variables state1 and count. Both these variables will store the current state of pushbutton and seven segment value respectively.
After that we defined the number of segments, we are using with ESP32. LED segment pins are defined for ESP32 boards. Change the pin according to the type of ESP32 you are using.
Any of the ESP32 digital pins can be used.
Next as we are using the Common Anode type, so we have defined it inside the code.
In case of Common Cathode replace it with below code.
At last, an if condition is used that will check the current state of the pushbutton and every time we press the button a value is incremented by 1. This will go on until the count variable value becomes 10. After that it will again be initialized from 0.
6.2: Output
Output shows digits printed from 0 to 9.
Conclusion
In conclusion, Using ESP32 with Push button and Arduino code, we can easily control the state of each segment in a seven-segment display, allowing for the creation of a custom real time counter for making interactive projects using Push button.
