This document describes an SMS-based wireless notice board project using a microcontroller and GSM modem. The system allows notices to be displayed on an LED matrix board remotely via SMS messages sent to the GSM modem. The microcontroller receives SMS texts with the GSM modem and MAX232 interface and displays the messages on the LED board. The project uses components like a 89S52 microcontroller, SIM300 GSM modem, 74138 and 74154 decoder ICs, and a 24C02 EEPROM for message storage.

1. Submitted By:
Swarnim Maurya
Bharat Bhagtani
Vishu Jain
(DR. K.N. Modi Institute of Engg. & Tech. , Modinagar,
Ghaziabad)

2. CONTENTS
1. Project Idea
2. Introduction
3. Working Principle
4. Flow Chart
5. Schematic Diagram
6. Components used
a) AT89S52
b)GSM Modem
c)MX232 and DB9 Connector
d)DECODER IC’s
i- IC 74154
ii- IC74138
e)EEPROM (IC 24C02)
7- LED MATRIX
8- APPLICATION
9- CONCLUSION
10- REFERENCES

3. PROJECT IDEA:
 Notice Board is primary thing in any institution or organization or
public utility places like bus stations, railway stations and parks. But
sticking various notices day-to-day is a difficult process.
 A separate person is required to take care of this notices display. This
project deals about an advanced hi-tech wireless notice board.
 The project is built around a micro controller which provides all the
functionality of the display and wireless control. Display is obtained
on LED
 The advantage of this project being low cost and low power
consumption.

4. INTRODUCTION
 It presents an SMS based notice board incorporating the
widely used GSM to facilitate the communication of
displaying message on notice board via user’s mobile phone.
 SIM300 GSM modem with a SIM card is interfaced to the
ports of the microcontroller with the help of AT commands.
 SIM300 is duly interfaced through a level shifter IC MAX32
to the microcontroller. The messaged is thus fetched into the
microcontroller.
 It is further displayed on an electronic notice board which
equipped with LED display interfaced to microprocessor
powered by a regulated power supply from mains supply of
230 volts ac.

5. WORKING PRINCIPLE
 The GSM Modem is first properly initialized and then it
checks for modem connectivity. The program is written in
microcontroller to perform this task.
 After that user has to send SMS to GSM modem and
message contents are finally displayed on the LED matrix.
The microcontroller used in this project is Atmel 89S52.
 The data is sent to microcontroller through MAX232
interface. MAX232 acts as logic level shifter IC. It means, it
converts TTL Logic Level to RS-232 and vise versa.

6. FLOW CHART

7. Schematic Diagram

8. COMPONENTS
HARDWARE USED
•IC 74138 AS A 3 TO 8 LINE
DECODER
•IC 74154 AS A 4 TO 16 LINE
DECODER
•L.E.D’S TOTAL 32 LINES IN 7
ROWS TOTAL 224 L.E.D’S
• 1 M OHM PRESET
 STEP DOWN TRANSFORMER
6 VOLT AC
 TWO DIODE AS A
RECTIFIERIN 4007
 ELECTROLYTIC CAPACITOR
470 uF, 100 uF, 10uF
 CRYSTAL 3.58 Mhz
 22pF CERAMIC CAPACITOR
WITH CRYSTAL
 7805 REGULATOR
 89S52 MICROCONTROLLER
 558 PNP TRANSISTOR 32 FOR
COLOUM LINES, 7 FOR DATA
LINE
SOFTWARE USED
 Keil u Vision
 Flash Magic

9. 89S52 Microcontroller
 Microcontroller is a small computer on a single
integrated circuit containing a processor core,
memory and programmable I/O peripherals.
 The 89S52 microcontroller has Harvard
architecture with RISC (Reduced Instruction Set
Computer) concept.
 The 89S52RB2/RC2/RD2 device contains a non-
volatile 16kB/32kB/64kB Flash program memory
that is both parallel programmable and serial In-
System and In-Application Programmable.
 89S52 has 8-bit ALU which can perform all the 8-
bit arithmetic and logical operations in one
machine cycle. The ALU is associated with two
registers A & B special function registers.

10. FEATURES
 4 KB on chip program
memory (ROM or EPROM)).
 128 bytes on chip data
memory (RAM).
 8-bit data bus
 16-bit address bus
 32 general purpose registers
each of 8 bits
 Two -16 bit timers T0 and T1
 Five Interrupts (3 internal
and 2 external).
 Four Parallel ports each of 8-
bits (PORT0, PORT1,
PORT2, PORT3) with a total
of 32 I/O lines.
 One 16-bit program counter
and One 16-bit DPTR ( data
pointer)
 One 8-bit stack pointer
 One Microsecond
instruction cycle with 12
MHz Crystal.
 One full duplex serial
communication port.

11. MICROCONTROLLER AT89S52
 PIN DIAGRAM

12. BLOCK DIAGRAM
schematic architecture
CPU
On-chip
RAM
On-chip
ROM for
program
code
4 I/O Ports
Timer 0
Serial
PortOSC
Interrupt
Control
External interrupts
Timer 1
Timer/Counter
Bus
Control
TxD RxDP0 P1 P2 P3

13. GSM MODEM
 A GSM modem is a wireless modem
that works with a GSM wireless
network.
 It operates at either the 900MHz or
1800MHz frequency band.
 It supports voice calls and data transfer
speeds of up to 9.6kbits/s, together
with the transmission of SMS (Short
Message Service).
 The GSM Modem comes with a serial
interface which the modem can be
controlled using AT command
interface.

14. GSM SPECIFICATIONS
 Frequency Used : 890 to 960 Mhz
 Uplink Frequency : 890 to 915 Mhz
 Downlink Frequency: 935 to 960 Mhz
 Channel Bandwidth: 200 Mhz
 No. Of Channels: 124
 Modulation Used GMSK
 Mobile Station Power Output: 0.8w,2.5w,8w
 FDM-TDMA Technology is used in GSM.

15. AT COMMANDS

16. MAX 232

17. MAX 232 IC
• MAX 232 that converts signals from an RS-232 serial port
to signals suitable for use in TTL compatible digital logic
circuits.
• The MAX 232 is a dual driver/receiver and typically
converts the RX, TX CTS and RTS signals.
• It changes a TTL Logic 0 to between +3 and +15 V, and
changes TTL logic 1 to between -3 to -15V, and vice versa
for converting from RS232 to TTL.

18. DB9 Connector
 The DB9 connector is an analog 9-pin plug of the D-
Sub miniature connector family (D-Sub or Sub-D).
 The DB9 connector is mainly used for serial
connections, allowing for the asynchronous
transmission of data as provided for standard RS-232
(RS-232C).

19. External Memory-24c02
 It is a non-volatile memory and is used for the storage of message
in case any new SMS is not received by the modem.
 It used as memory reservoir to store previous message.
 Pins in 24C02-
1-SDA(Serial Data)
2-SCL(Serial Clock)
3-WP(Write Protect)
4-Device/Page Address pins(AO,A1,A2)
5-Ground(GND)
6-VCC

20. Power Supply
 In this project firstly we use one step down transformer. Step down
transformer step down the voltage from 220 volt Ac to 12 volt Ac.
 This AC voltage is further converted into DC with the help of
rectifier circuit. In rectifier circuit we use TWO diode.
 All the diodes are arranges as a bridge rectifier circuit. Output of
this rectifier is pulsating Dc. To convert this pulsating DC into
smooth dc we use one capacitor as a filter components.
 Capacitor converts the pulsating Dc into smooth DC with the help
of its charging and discharging effect.
 Output of the rectifier is now regulated with the help of IC
regulator circuit . We use 7805 regulator then its means its is 5 volt
regulator and if we use 7808 regulator then its means that it is 8
volt regulator circuit.
 In this project we use 5 volt dc regulated power supply for the
complete circuit. Separate 9 volt dc power supply is used for the
relay coil

21. Schematic View of Power Supply
Design
Transfor
mer
Diode for
Rectification
Capacitor
LED
Voltage
Regulator
IC

22. IC 74154 (4-16 line demultiplexer):
Each or these 4-line-to-16-line decoders utilizes TTL circuitry to decode four
binary-coded inputs into one of sixteen
mutually exclusive outputs when both the strobe inputs, G1 and G2, are
low. The demultiplexing function is performed
by using the 4 input lines to address the output line, passing data from
one of the strobe inputs with the other strobe
input low. When either strobe input is high, all outputs are high. These
demultiplexers are ideally suited for implementing
high-performance memory decoders. All inputs are buffered and input
clamping diodes are provided to minimize
transmission-line effects and thereby simplify system design.

23. IC 74154 Connection Diagram:

24. IC 74138
The DM74LS138 decodes one-of-eight lines, based upon the conditions at the three binary
select inputs and the three enable inputs.
Two active-low and one active-high enable inputs reduce the need for external gates or
inverters when expanding.
An enable input can be used as a data input for demultiplexing applications.
The DM74LS139 comprises two separate two-line-to-fourline
decoders in a single package. The active-low enable
input can be used as a data line in demultiplexing applications.

25. Features
 Designed specifically for high speed:
 Memory decoders
 Data transmission systems
 n DM74LS138 3-to-8-line decoders incorporates 3 enable
 inputs to simplify cascading and/or data reception
 n DM74LS139 contains two fully independent 2-to-4-line
decoders/demultiplex
 DM74LS138 21 ns
 n Typical power dissipation
 DM74LS138 -32 mW power

26. Schematic Diagram of IC74138

27. HOW LED MESSAGE IS DISPLAYED
Message M will have the code - db
080h,0dfh,0e7h,0dfh,080h,0ffh
HERE “db” means data is known as define bit

28. APPLICATIONS
• The Campus Display System is aimed at the colleges and
universities for displaying day-to-day information continuously
or at regular intervals during working hours. Display devices can
be setup at various places in the campus.
• Being GSM-based system, it offers flexibility to display flash
news or announcements faster than a programmable system.
• GSM-based campus display system can also be used at other
public places like schools, hospitals, railway stations, gardens
etc. without affecting the surrounding environment.

29. CONCLUSION
 The display boards are one of the major communications
medium for mass media.
 Local language can be added as a variation in this project. This
can be achieved by using graphics and other decoding
techniques. Also we realize that this project saves time, energy
and hence environment. Cost of printing and photocopying is
also reduced as information can be given to a large number of
people from our fingertips.
 Thus we can conclude that this project is just a start, an idea to
make use of GSM in communications to a next level.

30. References
• “The 8051 Microcontroller and Embedded
Systems” by Muhammad Ali Mazidi and Janice
Gillispie Mazidi, Pearson Education.
• ATMEL 89S52 Data sheets
 www.fadooengineers.com
 www.wikipedia.org

31. Thank You!!!