Microcontroller Classroom Schedule Bell

Manual bell ringing in local schools frequently suffers from human delays and inconsistency during exam and period changes.

Use a battery-backed DS3231 real-time clock connected to an ATmega328P to cycle a 30A electromagnetic relay connected to the school electric gong.

Constructed on a custom copper-clad prototype board with an optical isolation optocoupler (PC817) to prevent high-voltage AC back-EMF from resetting the microcontroller.

Ran continuously for 30 consecutive days in a laboratory simulation, clock drift was measured under 2 seconds over the full month.

Demonstrated complete scheduling reliability with an intuitive keypad for manual overrides during holidays and emergency assemblies.

Adding an ESP8266 Wi-Fi module for web-based schedule updates from the headmaster’s phone.