### Project 10 Make a clock

**1.Introduction**

Time is of essence in our life. We have all sort of stuff that tells time. In this lesson, we will make a device of our own using the DS3231 clock module. Combine with a buzzer, you can make an alarm or just a time telling device when combined with an LCD.

**2.Hardware required**

- EASY plug controller Board x1
- USB cable x1
- EASY plug cable x1
- EASY plug DS3231 Clock Module x1

Below is a brief introduction of this module.

![](media/image-20251126144816818.png)

The DS3231 is a low-cost, extremely accurate I2C real-time clock (RTC) with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. The device incorporates a battery input, and maintains accurate timekeeping when main power to the device is interrupted. The integration of the crystal resonator enhances the long-term accuracy of the device as well as reduces the piece-part count in a manufacturing line. The DS3231 is available in commercial and industrial temperature ranges, and is offered in a 16-pin, 300-mil SO package. Below are its specifications:

- Temperature range: -40 to +85; 
- Timing accuracy : ± 5ppm (±0.432 seconds / day)
- Device package and function compatible with DS3231
- Two calendar clock
- Output: 1Hz and 32.768kHz
- Reset output and Input Debounce of Pushbutton
- High speed (400kHz), I2C serial bus
- Supply voltage: +3.3V to +5.5V
- Digital temperature sensor with a precision of±3℃
- Working temperature: -40 ~ ℃ to +85 ~ ℃
- 16 pins Small Outline Package (300mil)
- Certified by American Association of Underwriters Laboratories (UL)
- Size: 38*20mm
- Weight: 4g

**3.Connection Diagram**

Now, connect the DS3231 module to the IIC port of the controller board using the EASY plug cable.

![](media/image-20251126145017856.png)

**4.Sample Code**

Connect the board to your PC using the USB cable; copy below code into Arduino IDE, and click upload to upload it to your board.

```c
#include <Wire.h>   // place file “Wire.h” under the directory “libraries” of Arduino
#include "DS3231.h"  // place file “DS3231.h” under the directory “libraries” of Arduino
DS3231 RTC; //Create the DS3231 object
char weekDay[][4] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
//year, month, date, hour, min, sec and week-day(starts from 0 and goes to 6)
//writing any non-existent time-data may interfere with normal operation of the RTC.
//Take care of week-day also.
DateTime dt(2015, 12, 16, 10,25, 33, 3);//open the series port and you can check time here or make a change to the time as needed.

void setup () 
{   Serial.begin(57600);//set baud rate to 57600
    Wire.begin();
    RTC.begin();
    RTC.adjust(dt); //Adjust date-time as defined 'dt' above 
}

void loop () 
{   DateTime now = RTC.now(); //get the current date-time
    Serial.print(now.year(), DEC);
    Serial.print('/');
    Serial.print(now.month(), DEC);
    Serial.print('/');
    Serial.print(now.date(), DEC);
    Serial.print(' ');
    Serial.print(now.hour(), DEC);
    Serial.print(':');
    Serial.print(now.minute(), DEC);
    Serial.print(':');
    Serial.print(now.second(), DEC);
    Serial.println();
    Serial.print(weekDay[now.dayOfWeek()]);
    Serial.println();
    delay(1000);
}
```

**5.Result**

Now, open serial monitor, set baud rate to 57600, it will display the date we set in the program. You can change the code for it to display different dates; the module will then begin time counting, as below picture shows.

![](media/3.png)