🌐

IoT Lab content is currently available in Arabic only. We're working on an English version.

Real Time Clock (RTC DS3231) | NexaLearn IoT Lab | NexaLearn

Time & Synchronization25 دقيقة

Real Time Clock (RTC DS3231)

How to make Arduino remember the time and date even after disconnecting power.

Lesson Content

Arduino has a millis() counter but it doesn't know the clock or date and starts from zero when power is lost. An RTC (Real Time Clock) module contains a precise chip and a small coin cell battery that keeps it counting time for years. It communicates via I2C protocol.

Components Needed

Arduino UnoDS3231 RTC Module

Wiring Notes

SDA to A4 and SCL to A5, like other I2C modules.

Code Example

#include <Wire.h>
#include "RTClib.h"
RTC_DS3231 rtc;
void setup() {
  Serial.begin(9600);
  if (!rtc.begin()) { Serial.println("RTC FAIL"); return; }
  if (rtc.lostPower()) {
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__))); // يضبطه وقت الرفع
  }
}
void loop() {
  DateTime now = rtc.now();
  Serial.print(now.hour()); Serial.print(':'); Serial.println(now.minute());
  delay(1000);
}

Common Mistakes

Expecting the RTC to automatically compensate for lost time without a 3V battery (CR2032) — the battery is the cornerstone of this component.