Temperature Displayed on 4 Digit 7 segment (common anode)

/*
 * created by Rui Santos, http://randomnerdtutorials.com
 * Temperature Sensor Displayed on 4 Digit 7 segment common anode 
 * 2013
 */
const int digitPins[4] = {
  4,5,6,7};                 //4 common anode pins of the display
const int clockPin = 11;    //74HC595 Pin 11 
const int latchPin = 12;    //74HC595 Pin 12
const int dataPin = 13;     //74HC595 Pin 14
const int tempPin = A0;     //temperature sensor pin
const byte digit[10] =      //seven segment digits in bits
{
  B00111111, //0
  B00000110, //1
  B01011011, //2
  B01001111, //3
  B01100110, //4
  B01101101, //5
  B01111101, //6
  B00000111, //7
  B01111111, //8
  B01101111  //9
};
int digitBuffer[4] = {
  0};
int digitScan = 0, flag=0,  soft_scaler = 0;
;
float tempK, tempC, tempF, temp;

void setup(){                
  for(int i=0;i<4;i++)
  {
    pinMode(digitPins[i],OUTPUT);
  }
  pinMode(tempPin, INPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);  
  pinMode(tempPin, INPUT);
}

//writes the temperature on display
void updateDisp(){
  for(byte j=0; j<4; j++)  
    digitalWrite(digitPins[j], LOW);

  digitalWrite(latchPin, LOW);  
  shiftOut(dataPin, clockPin, MSBFIRST, B11111111);
  digitalWrite(latchPin, HIGH);

  delayMicroseconds(100);
  digitalWrite(digitPins[digitScan], HIGH); 

  digitalWrite(latchPin, LOW);  
  if(digitScan==2)
    shiftOut(dataPin, clockPin, MSBFIRST, ~(digit[digitBuffer[digitScan]] | B10000000)); //print the decimal point on the 3rd digit
  else
    shiftOut(dataPin, clockPin, MSBFIRST, ~digit[digitBuffer[digitScan]]);

  digitalWrite(latchPin, HIGH);
  digitScan++;
  if(digitScan>3) digitScan=0; 
}

void loop(){ 
  tempK = (((analogRead(tempPin)/ 1023.0) * 5.0) * 100.0);  
  //Converts Kelvin to Celsius minus 2.5 degrees error
  tempC = tempK - 273.0;   
  tempF = ((tempK - 2.5) * 9 / 5) - 459.67;
  //Celsius temperature display
  tempC = int(tempC*100);
  digitBuffer[3] = int(tempC)/1000;
  digitBuffer[2] = (int(tempC)%1000)/100;
  digitBuffer[1] = (int(tempC)%100)/10;
  digitBuffer[0] = (int(tempC)%100)%10;
  updateDisp();
  delay(2);

  /*
  //Fahrenheit temperature display
  tempF = int(tempF*100);
  digitBuffer[3] = int(tempF)/1000;
  digitBuffer[2] = (int(tempF)%1000)/100;
  digitBuffer[1] = (int(tempF)%100)/10;
  digitBuffer[0] = (int(tempF)%100)%10;
  updateDisp();
  delay(2);
  */
}

How can that be working? You are setting HIGH a single pin from the Arduino as the anode pin to power simultaneously (because of 74hc595) the leds of a digit, which can be up to 8. You are using 220 ohms resistors for the segments, so each segment has 14ma of current. A single output pin could give power to only one segment, maybe two.

How can that be working?

I tried the code and wiring. It just works. Thanks @ruisantos16

Phil

It just works.

@deslauriersp @ruisantos16 since i use a different temperature sensor, i added two libraries and just a few other lines of code to read out the sensor data, but i dont get any useful result on the display.
I added a serial printout, the values of the sensor are fine, but it just shows garbage on the display, its not even numbers really.
what did i do wrong here?

/*
 * created by Rui Santos, http://randomnerdtutorials.com
 * Temperature Sensor Displayed on 4 Digit 7 segment common anode 
 * 2013
 */

#include <OneWire.h>
#include <DallasTemperature.h>

// Data wire is conntec to the Arduino digital pin 13
#define ONE_WIRE_BUS 13

// Setup a oneWire instance to communicate with any OneWire devices
OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature sensor 
DallasTemperature sensors(&oneWire);

 
const int digitPins[4] = {
  4,5,6,7};                 //4 common anode pins of the display
const int clockPin = 8;     //74HC595 Pin 11 
const int latchPin = 9;     //74HC595 Pin 12
const int dataPin = 10;     //74HC595 Pin 14

//------------------------------------------------------------------
const int TEST = 0000;
//------------------------------------------------------------------

const byte digit[10] =      //seven segment digits in bits
{
  B00111111, //0
  B00000110, //1
  B01011011, //2
  B01001111, //3
  B01100110, //4
  B01101101, //5
  B01111101, //6
  B00000111, //7
  B01111111, //8
  B01101111  //9
};
int digitBuffer[4] = {
  0};
int digitScan = 0, flag=0,  soft_scaler = 0;
;
float tempK, tempC, tempF, temp;

void setup(){                
  for(int i=0;i<4;i++)
  {
    pinMode(digitPins[i],OUTPUT);
  }
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);  

  sensors.begin();
  Serial.begin(9600);
}

//writes the temperature on display
void updateDisp(){
  for(byte j=0; j<4; j++)  
    digitalWrite(digitPins[j], LOW);

  digitalWrite(latchPin, LOW);  
  shiftOut(dataPin, clockPin, MSBFIRST, B11111111);
  digitalWrite(latchPin, HIGH);

  delayMicroseconds(100);
  digitalWrite(digitPins[digitScan], HIGH); 

  digitalWrite(latchPin, LOW);  
  if(digitScan==2)
    shiftOut(dataPin, clockPin, MSBFIRST, ~(digit[digitBuffer[digitScan]] | B10000000)); //print the decimal point on the 3rd digit
  else
    shiftOut(dataPin, clockPin, MSBFIRST, ~digit[digitBuffer[digitScan]]);

  digitalWrite(latchPin, HIGH);
  digitScan++;
  if(digitScan>3) digitScan=0; 
}

void loop(){ 
  // Call sensors.requestTemperatures() to issue a global temperature and Requests to all devices on the bus
  sensors.requestTemperatures(); 
  temp = sensors.getTempCByIndex(0);

//------------------------------------------------------------------
  temp = TEST;
//------------------------------------------------------------------

  Serial.print("Celsius temperature: ");
  Serial.print(temp); 
  Serial.print("\n");
  
  tempK = (((temp/ 1023.0) * 5.0) * 100.0);  
  //Converts Kelvin to Celsius minus 2.5 degrees error
  tempC = tempK - 273.0;   
  //tempF = ((tempK - 2.5) * 9 / 5) - 459.67;
  //Celsius temperature display
  tempC = int(tempC*100);
  digitBuffer[3] = int(tempC)/1000;
  digitBuffer[2] = (int(tempC)%1000)/100;
  digitBuffer[1] = (int(tempC)%100)/10;
  digitBuffer[0] = (int(tempC)%100)%10;
  updateDisp();
  delay(2);

  /*
  //Fahrenheit temperature display
  tempF = int(tempF*100);
  digitBuffer[3] = int(tempF)/1000;
  digitBuffer[2] = (int(tempF)%1000)/100;
  digitBuffer[1] = (int(tempF)%100)/10;
  digitBuffer[0] = (int(tempF)%100)%10;
  updateDisp();
  delay(2);
  */
}