Introduction:
We are happy to present to you Arduino DS3231 Based Real-Time Clock with Alarm & Temperature Monitor. This is a simple real-time clock with time, day, date using Arduino UNO board, and DS3231 module. We have also added two alarm functions and temperature monitors to further extend this project.
The alternative IC for DS3231 is DS1307. The DS3231 RTC has a built-in alarm function as well as a temperature sensor with a resolution of 0.25 and an accuracy of ±3°C which makes this project easier.
You can check the previous version of the similar project here:
1. Arduino DS3231 Real Time Clock (RTC) with Temperature Monitor
2. ESP8266 and DS3231 Based Real Time Clock (RTC)
3. Arduino GPS Clock
Components Required:
To design Arduino DS3231 Based Real-Time Clock with Alarm & Temperature Monitor, we need the following components.
| S.N. | Components | Quantity | Purchase Links |
|---|---|---|---|
| 1 | Arduino UNO Board | 1 | Amazon | AliExpress |
| 2 | RTC Module DS3231 | 1 | Amazon | AliExpress |
| 3 | 20x4 LCD Display | 1 | Amazon | AliExpress |
| 4 | Potentiometer 10K | 1 | Amazon | AliExpress |
| 5 | Push Button Switch | 3 | Amazon | AliExpress |
| 6 | Buzzer 5V | 1 | Amazon | AliExpress |
| 7 | Resistor 330-ohm | 1 | Amazon | AliExpress |
| 8 | Connecting Wires | 10 | Amazon | AliExpress |
| 9 | Breadboard | 1 | Amazon | AliExpress |
DS3231 RTC Module:
Introduction:
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. Check the DS3231 Datasheets
The RTC maintains seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with an active-low AM/PM indicator. Two programmable time-of-day alarms and a programmable square-wave output are provided.
A precision temperature-compensated voltage reference and comparator circuit monitors the status of VCC to detect power failures, to provide a reset output, and to automatically switch to the backup supply when necessary. Additionally, the active-low RST pin is monitored as a pushbutton input for generating a µP reset.
Key Features:
- Highly Accurate RTC Completely Manages All Timekeeping Functions
- Real-Time Clock Counts Seconds, Minutes, Hours, Date of the Month, Month,
Day of the Week, and Year, with Leap-Year Compensation Valid Up to 2100 - Accuracy ±2ppm from 0°C to +40°C
- Accuracy ±3.5ppm from -40°C to +85°C
- Digital Temp Sensor Output: ±3°C Accuracy
- Register for Aging Trim
- Active-Low RST Output/Pushbutton Reset Debounce Input
- Two Time-of-Day Alarms
- Programmable Square-Wave Output Signal
- Simple Serial Interface Connects to Most Microcontrollers
- Fast (400kHz) I2C Interface
- Battery-Backup Input for Continuous Timekeeping
- Low Power Operation Extends Battery-Backup Run Time
- 3.3V Operation
- Operating Temperature Ranges: Commercial (0°C to +70°C) and Industrial (-40°C to +85°C)
- Underwriters Laboratories® (UL) Recognized
Circuit Diagram: Arduino DS3231 Based Real-Time Clock with Alarm & Temperature
The DS3231 module is supplied with 5V as the 20*4 LCD (JHD204). There are 3 data lined connected between the DS3231 Module & Arduino board. SCL line is connected to analog pin 5, SDA is connected to analog pin 4 and the INT line is connected to digital pin 2 which is the external interrupt pin of the Arduino. The DS3231 interrupts the microcontroller when there is an alarm (alarm1 or alarm2).
In the circuit, there are 3 push buttons: B1, B2, and B3. These buttons are used to set time, calendar & alarms.
For setting Time & Date:
Button B1 = Button B1 selects time or date parameter like an hour, minute, day, date, month.
Button B2 = B2 increments the selected parameter.
For setting Alarm:
Button B3 = Button B3 selects the parameter
Button B2 = Button B2 increments the selected parameter.
Also, there is a buzzer connected to Arduino pin 12, this buzzer
Source Code:
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// include LCD library code #include <LiquidCrystal.h> // include Wire library code (needed for I2C protocol devices) #include <Wire.h> // LCD module connections (RS, E, D4, D5, D6, D7) LiquidCrystal lcd(3, 4, 5, 6, 7, 8); const int button1 = 9; // button1 pin number const int button2 = 10; // button1 pin number const int button3 = 11; // button1 pin number const int alarm_pin = 12; // Alarms pin number void setup() { pinMode(9, INPUT_PULLUP); pinMode(10, INPUT_PULLUP); pinMode(11, INPUT_PULLUP); pinMode(12, OUTPUT); digitalWrite(alarm_pin, LOW); // set up the LCD's number of columns and rows lcd.begin(20, 4); Wire.begin(); // Join i2c bus attachInterrupt(digitalPinToInterrupt(2), Alarm, FALLING); } // Variables declaration bool alarm1_status, alarm2_status; char Time[] = " : : ", calendar[] = " / /20 ", alarm1[] = "A1: : :00", alarm2[] = "A2: : :00", temperature[] = "T: . C"; byte i, second, minute, hour, day, date, month, year, alarm1_minute, alarm1_hour, alarm2_minute, alarm2_hour, status_reg; void Alarm(){ digitalWrite(alarm_pin, HIGH); } void DS3231_read(){ // Function to read time & calendar data Wire.beginTransmission(0x68); // Start I2C protocol with DS3231 address Wire.write(0); // Send register address Wire.endTransmission(false); // I2C restart Wire.requestFrom(0x68, 7); // Request 7 bytes from DS3231 and release I2C bus at end of reading second = Wire.read(); // Read seconds from register 0 minute = Wire.read(); // Read minuts from register 1 hour = Wire.read(); // Read hour from register 2 day = Wire.read(); // Read day from register 3 date = Wire.read(); // Read date from register 4 month = Wire.read(); // Read month from register 5 year = Wire.read(); // Read year from register 6 } void alarms_read_display(){ // Function to read and display alarm1, alarm2 and temperature data byte control_reg, temperature_lsb; char temperature_msb; Wire.beginTransmission(0x68); // Start I2C protocol with DS3231 address Wire.write(0x08); // Send register address Wire.endTransmission(false); // I2C restart Wire.requestFrom(0x68, 11); // Request 11 bytes from DS3231 and release I2C bus at end of reading alarm1_minute = Wire.read(); // Read alarm1 minutes alarm1_hour = Wire.read(); // Read alarm1 hours Wire.read(); // Skip alarm1 day/date register alarm2_minute = Wire.read(); // Read alarm2 minutes alarm2_hour = Wire.read(); // Read alarm2 hours Wire.read(); // Skip alarm2 day/date register control_reg = Wire.read(); // Read the DS3231 control register status_reg = Wire.read(); // Read the DS3231 status register Wire.read(); // Skip aging offset register temperature_msb = Wire.read(); // Read temperature MSB temperature_lsb = Wire.read(); // Read temperature LSB // Convert BCD to decimal alarm1_minute = (alarm1_minute >> 4) * 10 + (alarm1_minute & 0x0F); alarm1_hour = (alarm1_hour >> 4) * 10 + (alarm1_hour & 0x0F); alarm2_minute = (alarm2_minute >> 4) * 10 + (alarm2_minute & 0x0F); alarm2_hour = (alarm2_hour >> 4) * 10 + (alarm2_hour & 0x0F); // End conversion alarm1[8] = alarm1_minute % 10 + 48; alarm1[7] = alarm1_minute / 10 + 48; alarm1[5] = alarm1_hour % 10 + 48; alarm1[4] = alarm1_hour / 10 + 48; alarm2[8] = alarm2_minute % 10 + 48; alarm2[7] = alarm2_minute / 10 + 48; alarm2[5] = alarm2_hour % 10 + 48; alarm2[4] = alarm2_hour / 10 + 48; alarm1_status = bitRead(control_reg, 0); // Read alarm1 interrupt enable bit (A1IE) from DS3231 control register alarm2_status = bitRead(control_reg, 1); // Read alarm2 interrupt enable bit (A2IE) from DS3231 control register if(temperature_msb < 0){ temperature_msb = abs(temperature_msb); temperature[2] = '-'; } else temperature[2] = ' '; temperature_lsb >>= 6; temperature[4] = temperature_msb % 10 + 48; temperature[3] = temperature_msb / 10 + 48; if(temperature_lsb == 0 || temperature_lsb == 2){ temperature[7] = '0'; if(temperature_lsb == 0) temperature[6] = '0'; else temperature[6] = '5'; } if(temperature_lsb == 1 || temperature_lsb == 3){ temperature[7] = '5'; if(temperature_lsb == 1) temperature[6] = '2'; else temperature[6] = '7'; } temperature[8] = 223; // Put the degree symbol lcd.setCursor(10, 0); lcd.print(temperature); // Display temperature lcd.setCursor(0, 2); lcd.print(alarm1); // Display alarm1 lcd.setCursor(17, 2); if(alarm1_status) lcd.print("ON "); // If A1IE = 1 print 'ON' else lcd.print("OFF"); // If A1IE = 0 print 'OFF' lcd.setCursor(0, 3); lcd.print(alarm2); // Display alarm2 lcd.setCursor(17, 3); if(alarm2_status) lcd.print("ON "); // If A2IE = 1 print 'ON' else lcd.print("OFF"); // If A2IE = 0 print 'OFF' } void calendar_display(){ // Function to display calendar switch(day){ case 1: strcpy(calendar, "Sun / /20 "); break; case 2: strcpy(calendar, "Mon / /20 "); break; case 3: strcpy(calendar, "Tue / /20 "); break; case 4: strcpy(calendar, "Wed / /20 "); break; case 5: strcpy(calendar, "Thu / /20 "); break; case 6: strcpy(calendar, "Fri / /20 "); break; case 7: strcpy(calendar, "Sat / /20 "); break; default: strcpy(calendar, "Sat / /20 "); } calendar[13] = year % 10 + 48; calendar[12] = year / 10 + 48; calendar[8] = month % 10 + 48; calendar[7] = month / 10 + 48; calendar[5] = date % 10 + 48; calendar[4] = date / 10 + 48; lcd.setCursor(0, 1); lcd.print(calendar); // Display calendar } void DS3231_display(){ // Convert BCD to decimal second = (second >> 4) * 10 + (second & 0x0F); minute = (minute >> 4) * 10 + (minute & 0x0F); hour = (hour >> 4) * 10 + (hour & 0x0F); date = (date >> 4) * 10 + (date & 0x0F); month = (month >> 4) * 10 + (month & 0x0F); year = (year >> 4) * 10 + (year & 0x0F); // End conversion Time[7] = second % 10 + 48; Time[6] = second / 10 + 48; Time[4] = minute % 10 + 48; Time[3] = minute / 10 + 48; Time[1] = hour % 10 + 48; Time[0] = hour / 10 + 48; calendar_display(); // Call calendar display function lcd.setCursor(0, 0); lcd.print(Time); // Display time } void Blink(){ byte j = 0; while(j < 10 && (digitalRead(button1) || i >= 5) && digitalRead(button2) && (digitalRead(button3) || i < 5)){ j++; delay(25); } } byte edit(byte x, byte y, byte parameter){ char text[3]; while(!digitalRead(button1) || !digitalRead(button3)); // Wait until button B1 is released while(true){ while(!digitalRead(button2)){ // If button B2 is pressed parameter++; if(((i == 0) || (i == 5)) && parameter > 23) // If hours > 23 ==> hours = 0 parameter = 0; if(((i == 1) || (i == 6)) && parameter > 59) // If minutes > 59 ==> minutes = 0 parameter = 0; if(i == 2 && parameter > 31) // If date > 31 ==> date = 1 parameter = 1; if(i == 3 && parameter > 12) // If month > 12 ==> month = 1 parameter = 1; if(i == 4 && parameter > 99) // If year > 99 ==> year = 0 parameter = 0; if(i == 7 && parameter > 1) // For alarms ON or OFF (1: alarm ON, 0: alarm OFF) parameter = 0; lcd.setCursor(x, y); if(i == 7){ // For alarms ON & OFF if(parameter == 1) lcd.print("ON "); else lcd.print("OFF"); } else{ sprintf(text,"%02u", parameter); lcd.print(text); } if(i >= 5){ DS3231_read(); // Read data from DS3231 DS3231_display(); // Display DS3231 time and calendar } delay(200); // Wait 200ms } lcd.setCursor(x, y); lcd.print(" "); // Print two spaces if(i == 7) lcd.print(" "); // Print space (for alarms ON & OFF) Blink(); // Call Blink function lcd.setCursor(x, y); if(i == 7){ // For alarms ON & OFF if(parameter == 1) lcd.print("ON "); else lcd.print("OFF"); } else{ sprintf(text,"%02u", parameter); lcd.print(text); } Blink(); if(i >= 5){ DS3231_read(); DS3231_display();} if((!digitalRead(button1) && i < 5) || (!digitalRead(button3) && i >= 5)){ i++; // Increment 'i' for the next parameter return parameter; // Return parameter value and exit } } } void loop() { if(!digitalRead(button1)){ // If B1 button is pressed i = 0; hour = edit(0, 0, hour); minute = edit(3, 0, minute); while(!digitalRead(button1)); // Wait until button B1 released while(true){ while(!digitalRead(button2)){ // If button B2 button is pressed day++; // Increment day if(day > 7) day = 1; calendar_display(); // Call display_calendar function lcd.setCursor(0, 1); lcd.print(calendar); // Display calendar delay(200); } lcd.setCursor(0, 1); lcd.print(" "); // Print 3 spaces Blink(); lcd.setCursor(0, 1); lcd.print(calendar); // Print calendar Blink(); // Call Blink function if(!digitalRead(button1)) // If button B1 is pressed break; } date = edit(4, 1, date); // Edit date month = edit(7, 1, month); // Edit month year = edit(12, 1, year); // Edit year // Convert decimal to BCD minute = ((minute / 10) << 4) + (minute % 10); hour = ((hour / 10) << 4) + (hour % 10); date = ((date / 10) << 4) + (date % 10); month = ((month / 10) << 4) + (month % 10); year = ((year / 10) << 4) + (year % 10); // End conversion // Write time & calendar data to DS3231 RTC Wire.beginTransmission(0x68); // Start I2C protocol with DS3231 address Wire.write(0); // Send register address Wire.write(0); // Reset sesonds and start oscillator Wire.write(minute); // Write minute Wire.write(hour); // Write hour Wire.write(day); // Write day Wire.write(date); // Write date Wire.write(month); // Write month Wire.write(year); // Write year Wire.endTransmission(); // Stop transmission and release the I2C bus delay(200); } if(!digitalRead(button3)){ // If B3 button is pressed while(!digitalRead(button3)); // Wait until button B3 released i = 5; alarm1_hour = edit(4, 2, alarm1_hour); alarm1_minute = edit(7, 2, alarm1_minute); alarm1_status = edit(17, 2, alarm1_status); i = 5; alarm2_hour = edit(4, 3, alarm2_hour); alarm2_minute = edit(7, 3, alarm2_minute); alarm2_status = edit(17, 3, alarm2_status); alarm1_minute = ((alarm1_minute / 10) << 4) + (alarm1_minute % 10); alarm1_hour = ((alarm1_hour / 10) << 4) + (alarm1_hour % 10); alarm2_minute = ((alarm2_minute / 10) << 4) + (alarm2_minute % 10); alarm2_hour = ((alarm2_hour / 10) << 4) + (alarm2_hour % 10); // Write alarms data to DS3231 Wire.beginTransmission(0x68); // Start I2C protocol with DS3231 address Wire.write(7); // Send register address (alarm1 seconds) Wire.write(0); // Write 0 to alarm1 seconds Wire.write(alarm1_minute); // Write alarm1 minutes value to DS3231 Wire.write(alarm1_hour); // Write alarm1 hours value to DS3231 Wire.write(0x80); // Alarm1 when hours, minutes, and seconds match Wire.write(alarm2_minute); // Write alarm2 minutes value to DS3231 Wire.write(alarm2_hour); // Write alarm2 hours value to DS3231 Wire.write(0x80); // Alarm2 when hours and minutes match Wire.write(4 | alarm1_status | (alarm2_status << 1)); // Write data to DS3231 control register (enable interrupt when alarm) Wire.write(0); // Clear alarm flag bits Wire.endTransmission(); // Stop transmission and release the I2C bus delay(200); // Wait 200ms } if(!digitalRead(button2) && digitalRead(alarm_pin)){ // When button B2 pressed with alarm (Reset and turn OFF the alarm) digitalWrite(alarm_pin, LOW); // Turn OFF the alarm indicator Wire.beginTransmission(0x68); // Start I2C protocol with DS3231 address Wire.write(0x0E); // Send register address (control register) // Write data to control register (Turn OFF the occurred alarm and keep the other as it is) Wire.write(4 | (!bitRead(status_reg, 0) & alarm1_status) | ((!bitRead(status_reg, 1) & alarm2_status) << 1)); Wire.write(0); // Clear alarm flag bits Wire.endTransmission(); // Stop transmission and release the I2C bus } DS3231_read(); // Read time and calendar parameters from DS3231 RTC alarms_read_display(); // Read and display alarms parameters DS3231_display(); // Display time & calendar delay(50); // Wait 50ms } |
Video Preview & Explanation:
DS3231 Tutorial - Real Time Clock with Alarm & Temperature Monitor using Arduino
6 Comments
Can you please adjust the code if I had LCD 1602
Good day, a very nice and useful program. Unfortunately, it does not work. Is there a newer version?
There are some mis-controls in the flow and I think it might be due to a newer version of the DS3241 module. The temperature is displayed incorrectly and the program reacts incorrectly to the key commands. Unfortunately I am not able to find the errors as I am a beginner.
Greetings Gerd
He forgot to set INPUT/PULLUP the interrupt pin… pinMode(2, INPUT_PULLUP);
Can this DS3231 project perform daily tasks?
Will using an I2c backpack on the LCD work OK? I don’t have enough Digital Pins leftover to use on my program.
Thanks
What has to change in the code to use a 12c backpack on the LCD. I would like to try this project but I only have a 20×4 LCD with a !@c backpack. Please help if you can. Thank you.