How to Use RTC-DS1302: Examples, Pinouts, and Specs

The RTC-DS1302 is a real-time clock (RTC) module that provides accurate timekeeping capabilities. It is equipped with an integrated circuit (IC) DS1302 which communicates via a simple serial interface. The module includes a small coin cell battery that maintains the time when the main power is off. Common applications include clocks, data loggers, timers, and other devices that require an accurate time reference.

• Timekeeping Accuracy: ±2 minutes/month at 25°C
• Operating Voltage: 2.0V to 5.5V
• Battery Backup Voltage: 1.3V to 5.5V
• Operating Current: 2mA (max)
• Battery Current: 300nA (typical)
• Operating Temperature: 0°C to +70°C
• Interface: Serial (Simple 3-wire interface)

1. Power Connections: Connect VCC to a 2.0V to 5.5V power supply and GND to the ground.
2. Serial Interface: Connect CLK, DAT, and RST to the microcontroller's digital pins.
3. Battery Backup: Install a coin cell battery to the BAT pin to maintain timekeeping during power loss.

• Ensure that the power supply voltage does not exceed 5.5V to prevent damage.
• The battery should be installed correctly with the positive side facing up.
• Use pull-up resistors on the data line if required by the microcontroller.
• Avoid placing the module near heat sources or in environments with high humidity.

#include <DS1302.h>

// Initialize the DS1302
// RST pin, DAT pin, CLK pin
DS1302 rtc(7, 6, 5);

void setup() {
  // Set the clock to run-mode, and disable the write protection
  rtc.halt(false);
  rtc.writeProtect(false);

  // Setup Serial connection
  Serial.begin(9600);

  // The following lines can be uncommented to set the date and time
  // rtc.setDOW(FRIDAY);        // Set Day-of-Week to FRIDAY
  // rtc.setTime(12, 0, 0);     // Set the time to 12:00:00 (24hr format)
  // rtc.setDate(6, 8, 2010);   // Set the date to August 6th, 2010
}

void loop() {
  // Get the current time and date from the RTC
  Serial.print(rtc.getDOWStr());
  Serial.print(" ");
  
  // Print the time
  Serial.print(rtc.getTimeStr());
  Serial.print(" -- ");

  // Print the date
  Serial.println(rtc.getDateStr());

  // Wait one second before repeating :)
  delay (1000);
}

• Time not accurate: Ensure the battery is installed correctly and has charge.
• Module not responding: Check the wiring, especially the serial interface connections.
• Time resets on power cycle: Verify that the battery is present and functioning.

• Double-check the connections and ensure that the correct pins are used.
• Replace the battery if the module fails to keep time after power is removed.
• If using long wires, ensure they are securely connected and consider using shielded cables to reduce noise.

Q: Can the RTC-DS1302 be used in low-power applications? A: Yes, the RTC-DS1302 has a low-power consumption mode and can be used in battery-powered applications.

Q: How do I set the time on the RTC-DS1302? A: You can set the time by using the rtc.setTime() function in your code, as shown in the example above.

Q: What is the lifespan of the battery? A: The lifespan of the battery depends on the quality and type of battery used, but typically it can last for several years.

Q: Does the RTC-DS1302 account for leap years? A: Yes, the DS1302 chip has an automatic leap year compensation valid up to the year 2100.

Q: Can I use the RTC-DS1302 with other microcontrollers besides Arduino? A: Yes, the RTC-DS1302 can be interfaced with any microcontroller that supports a serial interface. Adjustments to the code may be necessary for different platforms.