7-segment Display

Overview

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.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Elite Explorer Kit	300+	Elite Explorer Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
Arduino Uno R4 WiFi	-
Breadboard	BUY
Jumper Wires	BUY
Resistor	BUY
7-segment Display	BUY

Wiring

Schematic Diagram

In this experiment, connect each of pin a-g of the 7-Segment Display to one 1000 ohm 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).

Code

Note

• You can open the file 13-7_segment.ino under the path of elite-explorer-kit-main\basic_project\13-7_segment directly.

• Or copy this code into Arduino IDE.

Code Analysis

The code may be a little long for this experiment. But the syntax is simple. Let’s take a look.

Call the function in loop()

digital_1(); //display 1 to the 7-segment

delay(1000); //wait for a second

digital_2(); //display 2 to the 7-segment

delay(1000); //wait for a second

digital_3(); //display 3 to the 7-segment

delay(1000); //wait for a second

digital_4(); //display 4 to the 7-segment

Calling these functions into the loop() is to let the 7-Segment display 0-F. The functions are shown below. Take digital_2() for example:

Detailed analysis of digital_2()

void digital_2()  //display 2 to the 7-segment
{
  turnOffAllSegments();
  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  digitalWrite(g, HIGH);
  digitalWrite(e, HIGH);
  digitalWrite(d, HIGH);
}

First, we need to understand how the numeral 2 appears on the 7-Segment display. It is achieved by powering on segments a, b, d, e, and g. In programming, pins connected to these segments are set to a High level while c and f are set to Low level. We start by using the function turnOffAllSegments() to turn off all segments and then light up the required ones.

After running this part, the 7-segment will display 2. Similarly, the display of other characters are the same. Since the letters b and d in upper case, namely B and D, would look the same with 8 and 0 on the display, they are displayed in lower case instead.