The Electronics Hobbyist

This month’s Arduino project is to build two 2-digit 7-segment LED display circuits and sketches, one that counts up and one that counts up using mini push buttons. The next posts will explain the circuits and the Arduino sketches.

Materials:

• Arduino Duemilanove
• 1 2-digit 7-segment display (I got a 50-piece LED display grab bag for better value; the one I used was configured as shown)
• 2 Mini push button switches
• 9 Resistors, 100 Ohm
• 2 Resistors, 10K Ohm



• 2 2N3906 transistors (PNP)
• 1 Solderless breadboard
• Jumper Wires in assorted lengths

Sketch for counting up without buttons:

// www.TheElectronicsHobbyist.com/blog
// Natalia Fargasch Norman
// Dual seven-segment LED Display
// Common Anode digit 1 pin 10
// Common Anode digit 2 pin 5

//       CA1 G  F  A  B
//        |  |  |  |  |      -> pins and segments they control
//   ---------    ---------
//   |   A   |    |   A   |
//  F|       |B  F|       |B
//   |---G---|    |---G---|
//  E|       |C  E|       |C
//   |   D   |    |   D   |
//   ---------    ---------
//        |  |  |  |  |      -> pins and segments they control
//        D  DP E  C CA2         

// Segments that make each number when lit:
// 0 => -FEDCBA
// 1 => ----BC-
// 2 => G-ED-BA
// 3 => G--DCBA
// 4 => GF--CB-
// 5 => GF-DC-A
// 6 => GFEDC-A
// 7 => ----CBA
// 8 => GFEDCBA
// 9 => GF-DCBA

// Arduino digital pins used to light up
// corresponding segments on the LED display
#define A 3
#define B 2
#define C 6
#define D 8
#define E 7
#define F 4
#define G 5

// Pins driving common anodes
#define CA1 13
#define CA2 12

// Pins for A B C D E F G, in sequence
const int segs[7] = { 3, 2, 6, 8, 7, 4, 5 };

// Segments that make each number
const byte numbers[10] = { 0b1000000, 0b1111001, 0b0100100, 0b0110000, 0b0011001, 0b0010010,
0b0000010, 0b1111000, 0b0000000, 0b0010000 };

void setup() {
  pinMode(A, OUTPUT);
  pinMode(B, OUTPUT);
  pinMode(C, OUTPUT);
  pinMode(D, OUTPUT);
  pinMode(E, OUTPUT);
  pinMode(F, OUTPUT);
  pinMode(G, OUTPUT);
  pinMode(CA1, OUTPUT);
  pinMode(CA2, OUTPUT);
}

void loop() {
  for (int digit1=0; digit1 < 10; digit1++) {
    for (int digit2=0; digit2 < 10; digit2++) {
      unsigned long startTime = millis();
      for (unsigned long elapsed=0; elapsed < 600; elapsed = millis() - startTime) {
        lightDigit1(numbers[digit1]);
        delay(5);
        lightDigit2(numbers[digit2]);
        delay(5);
      }
    }
  }
}

void lightDigit1(byte number) {
  digitalWrite(CA1, LOW);
  digitalWrite(CA2, HIGH);
  lightSegments(number);
}

void lightDigit2(byte number) {
  digitalWrite(CA1, HIGH);
  digitalWrite(CA2, LOW);
  lightSegments(number);
}

void lightSegments(byte number) {
  for (int i = 0; i < 7; i++) {
    int bit = bitRead(number, i);
    digitalWrite(segs[i], bit);
  }
}

Here’s a video of the 2-digit 7-segment display counter in action.

You might also enjoy:

1. Arduino 2-Digit 7-Segment Display with Buttons
2. Arduino 2-Digit 7-Segment Display Counter: Sketch
3. Controlling a Seven-Segment Display Using Arduino Part 4
4. Controlling a Seven-Segment Display Using Arduino Part 3