RTC DS1307 Module Specifications

General

• Real-Time Clock (RTC) IC: DS1307

• Communication Interface: I²C (IIC)

• Timekeeping: Seconds, minutes, hours, day, date, month, year

• 12-hour or 24-hour format

Electrical

• Operating Voltage: 5V DC

• Backup Battery: CR2032 (for maintaining time during power-off)

• I²C Clock Frequency: 100 kHz (standard mode)

Accuracy

• Typical Accuracy: ±2 minutes per month at 25°C

• Temperature Range: 0°C to +70°C

• Battery Backup: Keeps clock running for years (depends on battery)

Physical

• Module Dimensions: ~20 × 20 mm (varies by manufacturer)

• Pinout: VCC, GND, SDA, SCL, sometimes SQW

Features

• Square-wave output: optional 1Hz, 4kHz, 8kHz, 32kHz (programmable)

• Can set alarms with external circuitry

• Widely used for Arduino / Raspberry Pi projects

RTC DS3231 Module Specifications

General

• Real-Time Clock IC: DS3231 (temperature-compensated)

• Communication Interface: I²C

• Timekeeping: Seconds, minutes, hours, day, date, month, year

• 12-hour or 24-hour format

Electrical

• Operating Voltage: 3.3–5V DC

• Backup Battery: CR2032 (for continuous operation)

• I²C Clock Frequency: 100 kHz

Accuracy

• Temperature-compensated crystal oscillator

• Typical Accuracy: ±2 minutes per year (much better than DS1307)

• Temperature Range: −40°C to +85°C

Physical

• Module Dimensions: ~20 × 20 mm (depends on manufacturer)

• Pinout: VCC, GND, SDA, SCL, SQW

Features

• On-chip temperature sensor

• Square-wave output (1Hz, 4kHz, 8kHz, 32kHz)

• Battery backup ensures clock continues when main power is off

• Suitable for high-precision timekeeping projects