1. Submitted by Project Title AUTOMATIC BELL SYSTEM FOR SCHOOLS/ COLLEGES
Under the Guidance of
Submitted by

2. ABSTRACT
Automatic college bell system for indicating the completion of
period is a reliable circuit that takes over the manual task of switch
on/off the college bell with respect to time.
It has an Inbuilt Real Time Clock (RTC) which tracks the Real
Time.
When this time equals to the programmed ‘ON’ time, then the
corresponding Relay for the device is switched ON and then OFF
as per the ‘OFF’ time that finally switches the load ON or OFF.
Multiple ON/OFF times entry is the biggest advantage with this
project.
Matrix keypad helps entering the time while relays used with relay
drivers for the loads.

3. PROJECT BLOCK DIAGRAM

4. HARDWARE COMPONENTS
POWER SUPPLY BLOCK
VOLTAGE REGULATOR (LM 7805)
MICROCONTROLLER (AT89S52/AT89C51)
DS1307 RTC
MATRIX KEYPAD
RELAY
SEVEN SEGMENT
BC547
RESISTORS
CAPACITORS

5. POWER SUPPLY Bridge rectifier 5v Regulator 230 V AC 50 Hz 5V DC
Filter(470µf)
12V step down
transformer

6. It is a smaller computer Has on-chip RAM, ROM, I/O ports...
MICROCONTROLLER
It is a smaller computer
Has on-chip RAM, ROM, I/O ports...
RAM
ROM
I/O Port
Timer
Serial COM Port
Microcontroller
CPU
A single chip

7. INTERNAL STRUCTURE OF A MICRO CONTROLLER-AT89S52/51
CPU
On-chip RAM
On-chip ROM for program code
4 I/O Ports
Timer 0
Serial Port
OSC
Interrupt Control
External interrupts
Timer 1
Timer/Counter
Bus Control
TxD RxD
P0 P1 P2 P3
Address/Data
Counter Inputs

8. Features of AT89S51/52 Compatible with MCS®-51 Products
8K Bytes of In-System Programmable (ISP) Flash Memory
Endurance: 10,000 Write/Erase Cycles
4.0V to 5.5V Operating Range
Fully Static Operation: 0 Hz to 33 MHz
256 x 8-bit Internal RAM
32 Programmable I/O Lines
Three 16-bit Timer/Counters
Eight Interrupt Sources
Full Duplex UART Serial Channel
Interrupt Recovery from Power-down Mode
Watchdog Timer
Dual Data Pointer

9. Pin Description

10. RELAY IT IS A ELECTRO MAGNETIC SWITCH
USED TO CONTROL THE ELECTRICAL DEVICES
COPPER CORE MAGNETIC FLUX PLAYS MAIN ROLE HERE

11. The relay's switch connections are usually labeled COM, NC and NO:
COM = Common, always connect to this; it is the moving part of the itch.
NC = Normally Closed, COM is connected to this when the relay coil is off.
NO = Normally Open, COM is connected to this when the relay coil is on

12. RELAY DRIVER (ULN 2003)
ULN2003 is a high voltage and high current Darlington transistor array
It consists of seven NPN Darlington pairs that feature high-voltage outputs with common-cathode Clamp diode for switching inductive loads.
The ULN2003 has a 2.7kW series base resistor for each Darlington pair for operation directly with TTL or 5V CMOS devices.
Current, Output Max:500mA
Voltage, Input Max:5V
Voltage, Output Max:50V

13. Fig: ULN 2003

14. Keypad
A keypad is a set of buttons arranged in a block or "pad" which usually bear digits, symbols and usually a complete set of alphabetical letters. If it mostly contains numbers then it can also be called a numeric keypad.
In order to detect which key is pressed from the matrix, the row lines are to be made low one by one and read the columns. Assume that if Row1 is made low, then read the columns.
If any of the key in row1 is pressed then correspondingly the column 1will give low that is if second key is pressed in Row1, then column2 will give low.

15. DS1307 RTC
RTC?
The RTC chip is a specialized chip that just keeps track of time
It runs on a battery and keeps time for you even when there is a power outage!
Using an RTC, you can keep track of long timelines, even if you reprogram your microcontroller or disconnect it from USB or a power plug.
The RTC we'll be using is the DS1307 . It's low cost, easy to solder, and can run for years on a very small coin cell.

16. 56 byte nonvolatile RAM for general data storage
FEATURES OF DS1307
Real time clock counts seconds, minutes, hours, date of month, month, day of week and year with leap year compensation valid up to 2100
56 byte nonvolatile RAM for general data storage
2-wrire interface (I2C)
Automatic power fail detect
Consumes less than 500 nA for battery back-up at 25'C

17. BC547 (NPN –Transistor)
The BC547 transistor is an NPN Epitaxial Silicon Transistor.
It is used in general-purpose switching and amplification BC847/BC547 series 45 V, 100 mA NPN general-purpose transistors.
The ratio of two currents (Ic/Ib) is called the DC Current Gain of the device and is given the symbol of hfe or nowadays Beta, (β).

18. The current gain from the emitter to the collector terminal, Ic/Ie, is called Alpha, (α), and is a function of the transistor itself

19. LIQUID CRYSTAL DISPLAY (LCD)
Most common LCDs connected to the microcontrollers are 16x2 and 20x2 displays.
This means 16 characters per line by 2 lines and 20 characters per line by 2 lines, respectively.
The standard is referred to as HD44780U, which refers to the controller chip which receives data from an external source (and communicates directly with the LCD.

20. If an 8-bit data bus is used the LCD will require 11 data lines
LCD BACKGROUND
If an 8-bit data bus is used the LCD will require 11 data lines
(3 control lines plus the 8 lines for the data bus)
The three control lines are referred to as EN, RS, and RW
EN=Enable (used to tell the LCD that you are sending it data)
RS=Register Select (When RS is low (0), data is treated as a command)
(When RS is High(1), data being sent is text data )
R/W=Read/Write (When RW is low (0), the data written to the LCD)
(When RW is low (0), the data reading to the LCD)

21. WORKING OF PROJECT
In a seven segment display all 7segments are connected in parallel making all anodes common.
Switching transistors are connected to each seven segment display in order to make that segment ON or OFF.
When logic 0 is given to the switching transistor then it does not conduct and when logic 1 is given then it conducts.
Suppose if it is needed to be displayed on 1st 7-segment display then 1st switching transistor should be given logic high and rest transistors be given logic 0 at their base

22. Soft ware Requirements
Keil an ARM Company makes C compilers, macro assemblers, real-time kernels, debuggers, simulators, integrated environments, evaluation boards, and emulators for ARM7/ARM9/Cortex-M3, XC16x/C16x/ST10, 251, and 8051 MCU families.
Compilers are programs used to convert a High Level Language to object code. Desktop compilers produce an output object code for the underlying microprocessor, but not for other microprocessors.

23. i.e the programs written in one of the HLL like ‘C’ will compile the code to run on the system for a particular processor like x86 (underlying microprocessor in the computer).
For example compilers for Dos platform is different from the Compilers for Unix platform  So if one wants to define a compiler then compiler is a program that translates source code into object code.

24. THANKYOU