NCICT-2016 Special Issue 2 Page 155

Abstract

Notice Board is primary thing in any

institution / 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 notice board. The project is built

around the AT89S52 micro controller from Atmel.

This micro controller provides all the functionality

of the display and control. It also takes care of

creating different display effects for given text.

Matrix type display is designed using 5mm LED

on a printed circuit board. A driver circuit is

designed to drive all these LEDs. A simple PC key

board can be connected to this system to enter the

required text or notice. Several scrolling effects can

be selected using function keys of keyboard. The

scrolling speed of the text also can be changed

according to user requirement. After entering the

text, the user can disconnect the keyboard. At any

time the user can add or remove or alter the text

according to his requirement.This project uses

regulated 5V, 1A power supply. 7805 three

terminal voltage regulator is used for voltage

regulation. Bridge type full wave rectifier is used to

rectify the ac out put of secondary of 230/12V step

down transformer.

Introduction

An embedded system is a combination of software

and hardware to perform a dedicated task.

Some of the main devices used in embedded

products are Microprocessors and Microcontrollers.

Microprocessors are commonly referred to as

general purpose processors as they simply accept the

inputs, process it and give the output. In contrast, a

microcontroller not only accepts the data as inputs

but also manipulates it, interfaces the data with

various devices, controls the data and thus finally

gives the result. As everyone in this competitive

world prefers to make the things easy and simple to

handle, this project sets an example to some extent.

Block diagram

SMS BASED WIRELESS ELECTRONIC NOTICE BOARD USING GSM/3G MOBILE PHONE

KHANDOBA.R1, JYOTI.BHURE

2, DIVYABHARATI.S

3 AMBIKA.MATH

4.

1. Assistant Professor, E & CE. Dept. Basavakalyan Engineering College, Basavakalyan-585327,

2, 3,4, Students E & CE. Dept. Basavakalyan Engineering College, Basavakalyan-585327

NCICT-2016 Special Issue 2 Page 156

BLOCK DESCRIPTION

POWER SUPPLY: The input to the circuit is applied from the

regulated power supply. The a.c. input i.e., 230V

from the mains supply is step down by the

transformer to 12V and is fed to a rectifier. The

output obtained from the rectifier is a pulsating d.c

voltage. So in order to get a pure dc voltage, the

output voltage from the rectifier is fed to a filter to

remove any a.c components present even after

rectification. Now, this voltage is given to a voltage

regulator to obtain a pure constant dc voltage.

Transformer:

Usually, DC voltages are required to operate

various electronic equipment and these voltages are

5V, 9V or 12V. But these voltages cannot be

obtained directly. Thus the a.c input available at the

mains supply i.e., 230V is to be brought down to

the required voltage level. This is done by a

transformer. Thus, a step down transformer is

employed to decrease the voltage to a required

level

Rectifier:

The output from the transformer is fed to the

rectifier. It converts A.C. into pulsating D.C. The

rectifier may be a half wave or a full wave rectifier.

In this project, a bridge rectifier is used because of

its merits like good stability and full wave

rectification.

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The Bridge rectifier is a circuit, which converts an

ac voltage to dc voltage using both half cycles of

the input ac voltage. The Bridge rectifier circuit is

shown in the figure. The circuit has four diodes

connected to form a bridge. The ac input voltage is

applied to the diagonally opposite ends of the

bridge. The load resistance is connected between

the other two ends of the bridge.

For the positive half cycle of the input ac

voltage, diodes D1 and D3 conduct, whereas diodes

D2 and D4 remain in the OFF state. The

conducting diodes will be in series with the load

resistance RL and hence the load current flows

through RL.For the negative half cycle of the input

ac voltage, diodes D2 and D4 conduct whereas, D1

and D3 remain OFF. The conducting diodes D2

and D4 will be in series with the load resistance

RL and hence the current flows through RL in the

same direction as in the previous half cycle.

Thus a bi-directional wave is converted into a

unidirectional wave

Filter

Capacitive filter is used in this project. It removes

the ripples from the output of rectifier and

smoothens the D.C. Output received from this

filter is constant until the mains voltage and load is

maintained constant. However, if either of the two

is varied, D.C. voltage received at this point

changes. Therefore a regulator is applied at the

output stage

As the name itself implies, it regulates the input

applied to it. A voltage regulator is an electrical

regulator designed to automatically maintain a

constant voltage level. In this project, power supply

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of 5V and 12V are required. In order to obtain

these voltage levels, 7805 and 7812 voltage

regulators are to be used. The first number 78

represents positive supply and the numbers 05, 12

represent the required output voltage levels. The

L78xx series of three-terminal positive regulators is

available in TO-220, TO-220FP, TO-3, D2PAK

and DPAK packages and several fixed output

voltages, making it useful in a wide range of

applications. These regulators can provide local on-

card regulation, eliminating the distribution

problems associated with single point regulation.

Each type employs internal current limiting,

thermal shut-down and safe area protection,

making it essentially indestructible. If adequate

heat sinking is provided, they can deliver over 1 A

output current.

Although designed primarily as fixed voltage

regulators, these devices can be used with external

components to obtain adjustable voltage and

currents.

Machine cycle for the 8052

The CPU takes a certain number of clock cycles to

execute an instruction. In the 8052 family, these

clock cycles are referred to as machine cycles. The

length of the machine cycle depends on the

frequency of the crystal oscillator. The crystal

oscillator, along with on-chip circuitry, provides the clock

source for the 8052 CPU.

The frequency can vary from 4 MHz to 30 MHz,

depending upon the chip rating and manufacturer.

But the exact frequency of 11.0592 MHz crystal

oscillator is used to make the 8052 based system

compatible with the serial port of the IBM PC.

In the original version of 8052, one machine cycle

lasts 12 oscillator periods. Therefore, to calculate

the machine cycle for the 8052, the calculation is

made as 1/12 of the crystal frequency and its

inverse is taken.

Light Emitting Diodes

(LED’s)

Example:

circuit symbol:

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Function

LED’s emit light when an electric current passes

through them.

Connecting and soldering

LED’s must be connected the correct way round,

the diagram may be labeled a or + for anode and k

or - for cathode (yes, it really is k, not c, for

cathode!). The cathode is the short lead and there

may be a slight flat on the body of round LED’s. If

you can see inside the LED the cathode is the larger

electrode (but this is not an official identification

method).

LED’s can be damaged by heat when soldering, but

the risk is small unless you are very slow. No

special precautions are needed for soldering most

LED’s.

Testing an LED:

Never connect an LED directly to a battery or

power supply!

It will be destroyed almost instantly because too

much current will pass through and burn it out.

LED’s must have a resistor in series to l imit the

current to a safe value, for quick testing

purposes a 1k resistor is suitable for most

LED’s if your supply voltage is 12V or less.

Remember to connect the LED the correct way

round!

Colors of LED’s

LED’s are available in red, orange, amber,

yellow, green, blue and white. Blue and white

LED’s are much more expensive than the other

colors.

The color of an LED is determined by the

semiconductor material, not by the coloring of the

'package' (the plastic body). LED’s of all colors are

available in uncolored packages which may be

diffused (milky) or clear (often described as 'water

clear'). The colored packages are also available as

diffused (the standard type) or transparent.

Light emitting diode

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Red, green and blue LED’s of the 5mm type

Single Color LED NOTICE BOARD

Today LED Advertisement Boards has

become a very efficient mode of

advertising.

These advertising displays are available/

applicable for indoor and outdoor

advertising

This is a scrolling messaging electronic

display board which displays the messages

received from any of the input mode

(SMS/GPRS/Wi-Fi/ RS232c)

These displays can be kept at different

parts of the city and send/load message

from one centralized place for instant

viewing of news or advertisements to

the common public.

Specifications

1)Imported high quality chips

2)Flex to install, easy to control

3)Durable, stable, long life

4)Moving effects

ATmega-8L Microcontroller

Microprocessors and microcontrollers are widely

used in embedded systems products.

Microcontroller is a programmable device. A

microcontroller has a CPU in addition to a fixed

amount of RAM, ROM, I/O ports and a timer

embedded all on a single chip. The fixed amount of

on-chip ROM, RAM and number of I/O ports in

microcontrollers makes them ideal for many

applications in which cost and space are critical.

The AVR core combines a rich instruction set with

32 general purpose working registers. All the 32

registers are directly connected to the Arithmetic

Logic Unit (ALU), allowing two independent

registers to be accessed in one single instruction

executed in one clock cycle. The resulting

architecture is more code efficient while achieving

Type Passive, optoelectronic

Working principle Electroluminescence

Invented Nick Holonyak Jr. (1962)

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throughputs up to ten times faster than

conventional CISC microcontrollers. It was popular

in the 1980s and early 1990s, but today it has

largely been superseded by a vast range of

enhanced devices with 8051-compatible processor

cores that are manufactured by more than 20

independent manufacturers including Atmel,

Infineon Technologies and Maxim Integrated

Products.

The ATmega8 is a low-power CMOS 8-bit

microcontroller based on the AVR RISC

architecture. By executing powerful instructions in

a single clock cycle, the ATmega8 achieves

throughputs approaching 1 MIPS per MHz,

allowing the system designer to optimize power

consumption versus processing speed. The present

project is implemented on Keil Uvision. In order to

program the device, proload tool has been used to

burn the program onto the microcontroller.

High-performance, Low-power AVR® 8-bit

Microcontroller

• Advanced RISC Architecture

– 130 Powerful Instructions – Most Single-clock

Cycle Execution

– 32 x 8 General Purpose Working Registers

– Fully Static Operation

– Up to 16 MIPS Throughput at 16 MHz

– On-chip 2-cycle Multiplier

• Nonvolatile Program and Data Memories

– 8K Bytes of In-System Self-Programmable Flash

Endurance: 10,000 Write/Erase Cycles

– Optional Boot Code Section with Independent

Lock Bits

In-System Programming by On-chip Boot Program

True Read-While-Write Operation

– 512 Bytes EEPROM

Endurance: 100,000 Write/Erase Cycles

– 1K Byte Internal SRAM

– Programming Lock for Software Security

• Peripheral Features

– Two 8-bit Timer/Counters with Separate

Prescaler, one Compare Mode

– One 16-bit Timer/Counter with Separate

Prescaler, Compare Mode, and Capture

Mode

– Real Time Counter with Separate Oscillator

– Three PWM Channels

– 8-channel ADC in TQFP and MLF package Eight

Channels 10-bit Accuracy

– 6-channel ADC in PDIP package Eight Channels

10-bit Accuracy

– Byte-oriented Two-wire Serial Interface

– Programmable Serial USART

– Master/Slave SPI Serial Interface

– Programmable Watchdog Timer with Separate

On-chip Oscillator

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– On-chip Analog Comparator

• Special Microcontroller Features

– Power-on Reset and Programmable Brown-out

Detection

– Internal Calibrated RC Oscillator

– External and Internal Interrupt Sources

– Five Sleep Modes: Idle, ADC Noise Reduction,

Power-save, Power-down, and

Standby

• I/O and Packages

– 23 Programmable I/O Lines

– 28-lead PDIP, 32-lead TQFP, and 32-pad MLF

• Operating Voltages

– 2.7 - 5.5V (ATmega8L)

– 4.5 - 5.5V (ATmega8)

• Speed Grades

– 0 - 8 MHz (ATmega8L)

– 0 - 16 MHz (ATmega8)

• Power Consumption at 4 Mhz, 3V, 25°C

– Active: 3.6 mA

– Idle Mode: 1.0 mA

– Power-down Mode: 0.5 μA

EEPROM (Electrically Erasable

Programmable Read only memory)

In the design of all microprocessors-based systems,

semiconductor memories are used as primary

storage for code and data. Semiconductor

memories are connected directly to the CPU and

they are the memory that the CPU first asks for

information (code and data). For this reas on,

semiconductor memories are sometimes referred to

as primary memory.

EEPROM has several advantages over other

memory devices, such as the fact that its method of

erasure is electrical and therefore instant. In

addition, in EEPROM one can select which byte to

be erased, in contrast to flash , in which the entire

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contents of ROM are erased. The main advantage

of EEPROM is that one can program and erase its

contents while it is in system board. It does not

require physical removal of the memory chip from

its socket. In general, the cost per bit for EEPROM

is much higher when compared to other devices.

The EEPROM used in this project is 24C04 type.

Features of 24C04 EEPROM:

1 mill ion erase/write cycles with 40 years

data retention.

Single supply voltage:

3v to 5.5v for st24x04 versions.

2.5v to 5.5v for st25x04 versions.

Hardware write control versions:

st24w04 and st25w04.

Programmable write protection.

Two wire serial interface, fully i2c bus

compatible

Byte and multibyte write (up to 4 bytes).

Page write (up to 8 bytes).

Byte, random and sequential read modes

Self timed programming cycle

Automatic address incrementing

Enhanced ESD/Latch up performances

Fig: Signal Name

The DESCRIPTION

24C04 is a 4Kbit electrically erasable

programmable memory (EEPROM), organized as 2

blocks of 256 x8 bits. They are manufactured in ST

Microelectronics’ Hi-Endurance Advanced CMOS

technology which guarantees an endurance of one

million erase/write cycles with data retention of 40

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years. Both Plastic Dual-in-Line and Plastic Small

Outline packages are available. The memories are

compatible with the I2C standard, two wire serial

interfaces which uses a bi-directional data bus and

serial clock. The memories carry a built-in 4 bit,

unique device identification code (1010)

corresponding to the I2C bus definition. This is

used together with 2 chip enable inputs (E2, E1) so

that up to 4 x 4K devices may be attached to the

I2C bus and selected individually. The memories

behave as a slave device in the I2C protocol with

all memory operations synchronized by the serial

clock. Read and write operations are initiated by a

START condition generated by the bus master. The

START condition is followed by a stream of 7 bits

(identification code 1010), plus one read/write bit

and terminated by an acknowledge bit.

Types

LEDs are produced in a variety of shapes and sizes.

The 5 mm cylindrical package (red, fifth from the

left) is the most common, estimated at 80% of

world production .The color of the plastic lens is

often the same as the actual color of light emitted,

but not always. For instance, purple plastic is often

used for infrared LEDs, and most blue devices have

clear housings. There are also LEDs in SMT

packages, such as those found on blinkies and on

cell phone keypads (not shown).

The main types of LEDs are miniature, high power

devices and custom designs such as alphanumeric

or multi-color.

Miniature

MAX232:

The MAX232 is an integrated circuit that converts

signals from an RS-232 serial port to signals

suitable for use in TTL compatible digital logic

circuits. The MAX232 is a dual driver/receiver and

typically converts the RX, TX, CTS and RTS

signals.

The drivers provide RS-232 voltage level outputs

(approx. ± 7.5 V) from a single + 5 V supply via

on-chip charge pumps and external capacitors. This

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makes it useful for implementing RS-232 in

devices that otherwise do not need any voltages

outside the 0 V to + 5 V range, as power supply

design does not need to be made more complicated

just for driving the RS-232 in this case.

The receivers reduce RS-232 inputs (which may be

as high as ± 25 V), to standard 5 V TTL levels.

These receivers have a typical threshold of 1.3 V,

and a typical hysteresis of 0.5 V.

The later MAX232A is backwards compatible with

the original MAX232 but may operate at higher

band rates and can use smaller external capacitors –

0.1 μF in place of the 1.0 μF capacitors used with

the original device.[1]

The newer MAX3232 is also backwards

compatible, but operates at a broader voltage range,

from 3 to 5.5 V.

GSM Modem

Then the MODEM connected to the

display system will receive the SMS, the

microcontroller inside the system is

programmed in such a way that when the

modem receives any message the

microcontroller will read the message

form serial port and

displaying the messages in the LED

display system .

ADVANTAGES AND APPLICATIONS

ADVANTAGS:

Ease of Operation

Color

Appearance

Better Graphics and More Fonts

Significant Cost Savings Number

APPLICATIONS:

Colleges

Industries

Bus Stations

Railway Stations

Shopping Malls

Public Places

FUTURE SCOPE

The project better suits for displaying information

in long distances ,and the information can be send,

alter any time according to user requirement.

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CONCLUSION:

This Project presents an electronic notice board

display using LED array with the help of Keyboard

using 89S52 Microcontroller. Experimental work

has been carried out carefully. The result shows

that higher efficiency is indeed achieved using the

embedded system. The proposed method is verified

to be highly beneficial for the general purpose

display.

REFERENCES:

1. www. howstuffworks.com

2. EMBEDDED SYSTEM BY RAJ

KAMAL

3. 8052 MICROCONTROLLER AND

EMBEDDED SYSTEMS BY MAZZID

4. Magazines

5. Electronics for you

6. Electrikindia

7. www.google.com

8. www.electronic projects.com