Circuit and Working Fig. 2 shows the circuit diagram of the automatic school bell. It is built around Arduino Uno R3, 16×2 LCD display with I2C (MOD1), DS3231 RTC, 4×4 matrix keypad, 5V SPDT relay, ...

Automatic school bell system using Arduino, RTC module, and relay. Rings bells at scheduled times with an LCD display for real-time clock updates. Easily customizable for schedule changes. Includes ...