Arduino - 7 Segment LED

Arduino Project #3

9 Second Seven Segment LTD Countdown Buzzer

This is a 7 segment LED connected to a 595N shift register.  When it counts down from 9 to 0 second, the buzzer will be activated.

Arduino circuit and sketch

//Pin connected to latch pin (ST_CP) of 74HC595

const int latchPin = 9;

//Pin connected to clock pin (SH_CP) of 74HC595

const int clockPin = 10;

////Pin connected to Data in (DS) of 74HC595

const int dataPin = 8;

const int buzz = 7;

const byte CHAR_COUNT = 10;

const byte symbols[CHAR_COUNT] = {

B01111110, // 0

B00010010, // 1

B10111100, // 2 

B10110110, // 3

B11010010, // 4 

B11100110, // 5

B11101110, // 6 

B00110010, // 7

B11111110, // 8 

B11110110  // 9

};

void setup() {

  //set pins to output because they are addressed in the main loop

  pinMode(latchPin, OUTPUT);

  pinMode(dataPin, OUTPUT);  

  pinMode(clockPin, OUTPUT);

  pinMode(buzz, OUTPUT);

  

}

void loop() {

  pattern1();

}

void pattern1()

{

  int i=9;

  while(i<CHAR_COUNT)

  {

    writeLeds(symbols[i]);

    if (i==0)

    tone(buzz,1000,1000);

    else 

    i = i-1; 

    delay(1000);

     

  }

}

void writeLeds(byte pattern)

{

  // turn off the output so the pins don't light up

  // while you're shifting bits:

  digitalWrite(latchPin, LOW);

  // turn on the next highest bit in bitsToSend:

  Serial.println(pattern,BIN);

  // shift the bits out:

  shiftOut(dataPin, clockPin, MSBFIRST, pattern);

    // turn on the output so the LEDs can light up:

  digitalWrite(latchPin, HIGH);

  }

Component Required:
seven segment LED, 595N Shift register, Buzzer, 220 Ohm resistor

Problem you may encounter:
If your 7 segment LED randomly lights up instead of showing numbers, you may try to change all the '1' into '0' and all '0' into '1' when you define 'symbols[CHAR_COUNT]'.