Display HH:MM:SS?

Projects Programming
1

Hello!
Can you teach me on how can I display HH:MM:SS? What should I remove here?

#include <DateTime.h>

// macros from DateTime.h 
/* Useful Constants */
#define SECS_PER_MIN  (60UL)
#define SECS_PER_HOUR (3600UL)
#define SECS_PER_DAY  (SECS_PER_HOUR * 24L)
 
/* Useful Macros for getting elapsed time */
#define numberOfSeconds(_time_) (_time_ % SECS_PER_MIN)  
#define numberOfMinutes(_time_) ((_time_ / SECS_PER_MIN) % SECS_PER_MIN) 
#define numberOfHours(_time_) (( _time_% SECS_PER_DAY) / SECS_PER_HOUR)
#define elapsedDays(_time_) ( _time_ / SECS_PER_DAY)  

void setup(){
 Serial.begin (9600);
}

void loop(){  
  time(millis() / 1000);
  delay(1000);
}

void time(long val){  
 int days = elapsedDays(val);
 int hours = numberOfHours(val);
 int minutes = numberOfMinutes(val);
 int seconds = numberOfSeconds(val);

  // digital clock display of current time
  Serial.print(days,DEC);  
  printDigits(hours);  
  printDigits(minutes);
  printDigits(seconds);
  Serial.println();  
  
}

void printDigits(byte digits){
  // utility function for digital clock display: prints colon and leading 0
  Serial.print(":");
  if(digits < 10)
    Serial.print('0');
  Serial.print(digits,DEC);  
}
2

What should I remove here?

Serial.print(days,DEC);
3

millis() reports the number of milliseconds since the Arduino restarted. It has NOTHING to do with what time it is now.

You are barking up the wrong tree.

4

No, not real time. I will be storing the number of hours when the fan I am monitoring turns on.
I want to display HH:MM:SS instead of DD:HH:MM:SS like 24:00:00 instead of 1:00:00:00.

Sorry I bothered you. I've been replacing time(millis()/1000) with time(86400000) to check for 24 hours :roll_eyes: I forgot the /1000.

This is what I used:

#include <DateTime.h>

/* Useful Constants */
#define SECS_PER_MIN  (60UL)
#define SECS_PER_HOUR (3600UL)
 
/* Useful Macros for getting elapsed time */
#define numberOfSeconds(_time_) (_time_ % SECS_PER_MIN)  
#define numberOfMinutes(_time_) ((_time_ / SECS_PER_MIN) % SECS_PER_MIN) 
#define numberOfHours(_time_) (( _time_ / SECS_PER_HOUR) % SECS_PER_HOUR) 

void setup(){
 Serial.begin (9600);
}

void loop(){  
  time(millis()/1000);
  delay(1000);
}

void time(long val){  
 int hours = numberOfHours(val);
 int minutes = numberOfMinutes(val);
 int seconds = numberOfSeconds(val);

  // digital clock display of current time
  Serial.print(hours,DEC);    
  printDigits(minutes);
  printDigits(seconds);
  Serial.println();  
  
}

void printDigits(byte digits){
  // utility function for digital clock display: prints colon and leading 0
  Serial.print(":");
  if(digits < 10)
    Serial.print('0');
  Serial.print(digits,DEC);  
}
5

But now (with the last code) is working, right?

6

arduinoTime:
No, not real time. I will be storing the number of hours when the fan I am monitoring turns on.
I want to display HH:MM:SS instead of DD:HH:MM:SS like 24:00:00 instead of 1:00:00:00.

try something like this:

unsigned long oneSecond = 1000UL;
unsigned long startTime;
int mySeconds = 0;
int myMinutes = 0;
int myHours = 0;
int myDays = 0;

void setup()
{
  Serial.begin(9600);
  startTime = millis();
}

void loop()
{
  if (millis() - startTime >= oneSecond)
  {
    displayTime();
    mySeconds++;
    startTime += oneSecond;
    if (mySeconds > 59)
    {
      myMinutes++;
      mySeconds = 0;
      if (myMinutes > 59)
      {
        myHours++;
        myMinutes=0;
        if (myHours > 23)
        {
          myDays++;
          myHours=0;
        }
      }
    }
  }
  //your other code here.....
}

void displayTime()
{
  //Serial.print(myDays);
  //Serial.print(":");
  if (myHours < 10) Serial.print("0");
  Serial.print(myHours);
  Serial.print(":");
  if (myMinutes < 10) Serial.print("0");
  Serial.print(myMinutes);
  Serial.print(":");
  if (mySeconds < 10) Serial.print("0");
  Serial.println(mySeconds);
}

or do all the work in the updateDisplay() function if you like:

void loop()
{
  if (millis() - startTime >= oneSecond)
  {
    displayTime();
  }
  //your other code here.....
}

void displayTime()
{
  startTime += oneSecond;
  if (mySeconds > 59)
  {
    myMinutes++;
    mySeconds = 0;
    if (myMinutes > 59)
    {
      myHours++;
      myMinutes=0;
      if (myHours > 23)
      {
        myDays++;
        myHours=0;
      }
    }
  }
  //Serial.print(myDays);
  //Serial.print(":");
  if (myHours < 10) Serial.print("0");
  Serial.print(myHours);
  Serial.print(":");
  if (myMinutes < 10) Serial.print("0");
  Serial.print(myMinutes);
  Serial.print(":");
  if (mySeconds < 10) Serial.print("0");
  Serial.println(mySeconds);
  mySeconds++;
}