Summary of Automatic School Bell
This Automatic School Bell System is a standalone device using a PIC18f4520 microcontroller to trigger bells at predefined times without PC dependency. It features an LCD display, keypad input, and an RTC1307 for accurate timekeeping with backup power. The system supports up to 10 bells, custom filters, and handles 1000W of AC load while storing timings in internal EEPROM.
Parts used in the Automatic School Bell:
- PIC18f4520 microcontroller
- RTC1307 IC
- MM74C922 decoder IC
- 16x2 LCD Display
- 4x4 Keypad
- Built-in back up battery supply
- Internal EEPROM
This project is an Automatic School bell system. Such a system triggers a bell (or operates any other load) at predifined time. In this version some advanced features are introduced:
– 16×2 LCD Display ( Displays current date, time and day)
– 4×4 Keypad for Inputs
– Stand alone product ( no PC required to program or maintain ringing schedule)
– No battery required to maintain clock and ringing schedule
– Variable ringing time
– Max 10 bells can be set
– Custom Weekend filters
– Monthly OFF / Weekly OFF
– Half Day
– Total AC Power Handling : 1000W (240V 5A)
– Connect as many AC electronic bells in parallel form
– Built-in back up battery supply
– Built in permanent memory for bell timings
– Auto-memory scan on system startup
I used PIC18f4520 microcontroller as the brain of the system. RTC1307 IC is used to maintain the clock,date and day with a 3V backup voltage battery. Bell timings are stored in the internal EEPROM of mcu.
MCU is reading time from RTC through I2C Serial protocol and compares the current time with stored memory time in a continous while(1) loop.
MM74C922 decoder IC is used for keyboard. Reading the sixteen buttons is done using 4-bits output of decoder IC.
Photos
PCB
Source : Automatic School Bell
- How does the system maintain time without a PC?
The RTC1307 IC maintains the clock, date, and day using a 3V backup voltage battery. - Can this system operate without a PC for programming?
Yes, it is a standalone product that requires no PC to program or maintain the ringing schedule. - What is the maximum number of bells the system can handle?
The system allows setting a maximum of 10 bells which can be connected in parallel form. - Does the system require a battery to maintain the clock?
No battery is required to maintain the clock and ringing schedule as it uses a built-in permanent memory and backup supply. - How are bell timings stored in the device?
Bell timings are stored in the internal EEPROM of the MCU. - What protocol does the MCU use to read time from the RTC?
The MCU reads time from the RTC through the I2C Serial protocol. - Is it possible to set custom weekend filters?
Yes, the system includes features for custom Weekend filters, Monthly OFF, Weekly OFF, and Half Day options. - What is the total AC power handling capacity of the system?
The system has a total AC power handling capacity of 1000W at 240V 5A.
