Arduino UNO R4 - 74HC595 4-Digit 7-Segment Display
A typical 4-digit 7-segment display is used in projects like clocks, timers, and counters, and usually needs 12 connections. The 74HC595 module simplifies this by using only 5 connections: 2 for power and 3 to control the segments.
This tutorial will not give you too much complex information about hardware. Instead, you will learn how to connect a 4-digit 7-segment display to an Arduino UNO R4 and how to program it to display information.
This guide will show how to use the 4-dot, 4-digit, 7-seegment display module that can show float values. If you need to display a colon separator, please use the TM1637 4-digit 7-segment Display Module.
Hardware Preparation
Or you can buy the following sensor kits:
| 1 | × | DIYables Sensor Kit (30 sensors/displays) | |
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
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Additionally, some of these links are for products from our own brand, DIYables.
Overview of 74HC595 4-digit 7-segment Display
A 74HC595 4-digit 7-segment display module usually includes 4 7-segment LEDs, 4 small dot LEDs, and a 74HC595 driver for each digit. It is perfect for showing temperatures or any numbers with decimals.
Pinout
The 74HC595 module for a 4-digit 7-segment display has 5 pins:
- SCLK pin: This is a clock input pin. Connect it to any digital pin on the Arduino UNO R4.
- RCLK pin: This is another clock input pin. Connect it to any digital pin on the Arduino UNO R4.
- DIO pin: This is a Data Input/Output pin. Connect it to any digital pin on the Arduino UNO R4.
- VCC pin: This pin provides power to the module. Connect it to a power supply between 3.3V and 5V.
- GND pin: This is a ground pin. Connect it to the ground.
Wiring Diagram
This table shows how to connect the Arduino UNO R4 pins to a 74HC595 4-digit 7-segment display:
| Arduino UNO R4 | 74HC595 7-segment display |
|---|---|
| 5V | 5V |
| 7 | SCLK |
| 6 | RCLK |
| 5 | DIO |
If you use different pins, change the pin numbers in the code.
This image is created using Fritzing. Click to enlarge image
Library Installation
To easily set up programming for a 74HC595 4-digit 7-segment Display, install the DIYables_4Digit7Segment_74HC595 library from DIYables.io. Here are the steps to install the library:
- Click on the Libraries icon on the left side of the Arduino IDE.
- Type “DIYables_4Digit7Segment_74HC595” in the search box, and look for the DIYables_4Digit7Segment_74HC595 library from DIYables.io
- Press the Install button.
You can also view this library on Github
How To Program For 74HC595 4-digit 7-segment using Arduino UNO R4
- Include the library
#include <DIYables_4Digit7Segment_74HC595.h>
- Connect the Arduino UNO R4 to the display module like this: D7 to SCLK, D6 to RCLK, and D5 to DIO.
#define SCLK 7 // The Arduino UNO R4 pin connected to SCLK
#define RCLK 6 // The Arduino UNO R4 pin connected to RCLK
#define DIO 5 // The Arduino UNO R4 pin connected to DIO
- Make a display item called DIYables_4Digit7Segment_74HC595.
DIYables_4Digit7Segment_74HC595 display = DIYables_4Digit7Segment_74HC595(CLK, DIO);
- You can show whole numbers with leading zeros, including negative numbers.
display.printInt(-13, false); // displays an integer without leading zeros
- You can show numbers with decimal points, add zeros in front, and include negative numbers.
display.printFloat(-9.2, 1, false);
- You can also show each number, decimal point, or character one by one using basic functions.
// display temperature 9.3°C
display.clear();
display.setNumber(1, 9); // Display number '9' at position 1
display.setDot(1); // Enable decimal point at position 1
display.setNumber(2, 3); // Display number '3' at position 2
display.setChar(3, SegChars::DEGREE); // Display degree symbol at position 3
display.setChar(4, SegChars::C); // Display character 'C' at position 4
display.show(); // Refresh display to show the set characters and numbers
- The 74HC595 4-digit 7-segment module controls each segment and LED by using a method called multiplexing. Therefore, the Arduino UNO R4 code MUST:
- Use the display.show() function in the main loop.
- Avoid using the delay() function in the main loop.
For more details, visit the library reference.
Arduino UNO R4 Code - Display Integer
#include <DIYables_4Digit7Segment_74HC595.h> // DIYables_4Digit7Segment_74HC595 library
#define SCLK 7 // The Arduino UNO R4 pin connected to SCLK
#define RCLK 6 // The Arduino UNO R4 pin connected to RCLK
#define DIO 5 // The Arduino UNO R4 pin connected to DIO
DIYables_4Digit7Segment_74HC595 display(SCLK, RCLK, DIO);
void setup() {
Serial.begin(9600);
display.printInt(-13, false); // you can display a value from -999 to 9999
//display.printInt(-132, false);
//display.printInt(9132, false);
//display.printInt(132, false);
//display.printInt(32, false);
//display.printInt(2, false);
//display.printInt(2, true);
}
void loop() {
display.loop(); // MUST call the display.loop() function in loop()
// DO SOMETHING HERE
// NOTE: do NOT use the delay() function in loop because it affects to the multiplexing
}
Detailed Instructions
Follow these instructions step by step:
- If this is your first time using the Arduino Uno R4 WiFi/Minima, refer to the tutorial on setting up the environment for Arduino Uno R4 WiFi/Minima in the Arduino IDE.
- Connect the 74HC595 4-digit 7-segment Display to the Arduino Uno R4 according to the provided diagram.
- Connect the Arduino Uno R4 board to your computer using a USB cable.
- Launch the Arduino IDE on your computer.
- Select the appropriate Arduino Uno R4 board (e.g., Arduino Uno R4 WiFi) and COM port.
- Copy the code and open it using Arduino IDE.
- Click the Upload button in Arduino IDE to send the code to Arduino UNO R4.
- Observe the changes on the 7-segment display.
Arduino UNO R4 Code - Display Float
#include <DIYables_4Digit7Segment_74HC595.h> // DIYables_4Digit7Segment_74HC595 library
#define SCLK 7 // The Arduino UNO R4 pin connected to SCLK
#define RCLK 6 // The Arduino UNO R4 pin connected to RCLK
#define DIO 5 // The Arduino UNO R4 pin connected to DIO
DIYables_4Digit7Segment_74HC595 display(SCLK, RCLK, DIO);
void setup() {
Serial.begin(9600);
display.printFloat(-9.2, 1, false);
//display.printFloat(-92.4, 1, false);
//display.printFloat(-9.24, 2, false);
//display.printFloat(192.4, 1, false);
//display.printFloat(19.24, 2, false);
//display.printFloat(1.924, 3, false);
}
void loop() {
display.loop(); // MUST call the display.loop() function in loop()
// DO SOMETHING HERE
// NOTE: do NOT use the delay() function in loop because it affects to the multiplexing
}
Arduino UNO R4 Code - Display Temperature
#include <DIYables_4Digit7Segment_74HC595.h> // DIYables_4Digit7Segment_74HC595 library
#define SCLK 7 // The Arduino UNO R4 pin connected to SCLK
#define RCLK 6 // The Arduino UNO R4 pin connected to RCLK
#define DIO 5 // The Arduino UNO R4 pin connected to DIO
DIYables_4Digit7Segment_74HC595 display(SCLK, RCLK, DIO);
void setup() {
Serial.begin(9600);
// display 9.3°C by controlling digit by digit
display.clear();
display.setNumber(1, 9); // set 9 at the 1st digit
display.setDot(1); // set . at the 1st digit
display.setNumber(2, 3); // set 3 at the 2nd digit
display.setChar(3, SegChars::DEGREE); // set ° at the 3rd digit
display.setChar(4, SegChars::C); // set C at the 3rd digit
display.show(); // show on the display
}
void loop() {
display.loop(); // MUST call the display.loop() function in loop()
// DO SOMETHING HERE
// NOTE: do NOT use the delay() function in loop because it affects to the multiplexing
}