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15. 7 segment LED Display 1.8" Blue Common Cathode with Shift Register 74HC595N


Arduino MEGA
7 Segment Display Blue
Breadboard
74HC595N
Breadboard jumpers


Big 7-segment displays have more than one LED in series per segment. Usually three. The DP has usually a single LED. Thats why I don't use resistors. For the dot you should use one.
For more info. (Datasheets)

Starting project.
Put the 74HC595N and the 7 Segment Display on the board.


The pinlayout from the blue segment display (18011AB) differs slightly from the red one.

Pins:
74HC595N7 segment displayArduino
pin 1Pin 10--
pin 2Pin 9--
pin 3Pin 8--
pin 4Pin 7--
pin 5Pin 6--
pin 6Pin 3--
pin 7Pin 1--
pin 8--GND
pin 9----
pin 10--5V
pin 11Pin 8--
pin 12Pin 7--
pin 13--GND
pin 14Pin 4--
pin 15Pin 2--
pin 16--5V
--Pin 4GND

Code
const int dataPin = 4;  // 74HC595 pin 14
const int latchPin = 7; // 74HC595 pin 12
const int clockPin = 8; // 74HC595 pin 11

//const char common = 'a';    // common anode
const char common = 'c';    // common cathode
byte digits[10] = {
  B10101111, B00000110, B11001101, B11001110, B01100110, B11101010, B11101011, B00001110, B11101111, B11101110
};

bool decPt = false;  // decimal point display flag
 
void setup() {
  pinMode(dataPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
}

void loop() {
  for (int i = 0; i <= 9; i++) {
    byte bits = digits[i];

    if (decPt) {
      bits = bits | B00010000;  // add decimal point if needed
    }
    
    myfnUpdateDisplay(bits);    // display alphanumeric digit
    delay(1000);                 // pause for second
  }
}

void myfnUpdateDisplay(byte eightBits) {
  if (common == 'a') {                  // using a common anonde display?
    eightBits = eightBits ^ B11111111;  // then flip all bits using XOR 
  }
  digitalWrite(latchPin, LOW);  // prepare shift register for data
  shiftOut(dataPin, clockPin, LSBFIRST, eightBits); // send data
  digitalWrite(latchPin, HIGH); // update display
}


Download : ino