Dual Sharing Of Real Time Clock – An Example

This intermediate communication systems project demonstrates how a single DS3231 Real Time Clock module can be shared between two separate ATMEGA328-based Arduino Uno boards. The DS3231 communicates via the I2C protocol, allowing multiple master devices to read the timekeeping registers if properly configured. In this circuit setup, the first Arduino Uno acts as the primary controller running the DS3231_AC_Scheduler.ino sketch. It queries the DS3231 for real-time data to manage an AC scheduling timer, activating a 5V relay module at programmed intervals. The relay module in turn controls a heavy-duty 5kW AC contactor to switch high-power mains equipment. Meanwhile, the second Arduino Uno accesses the same shared DS3231 clock module to retrieve time data independently, using it to drive a TFT ILI9163 128x128 color display that visually renders the current time and system status. Connection wires tie the shared I2C data and clock lines between the real-time clock module and both microcontroller boards, establishing a dual-system architecture powered from a common time reference.