micro controller

CHAPTER 1

MICROCONTROLLER

INTRODUCTION :

The microcontroller 89C51 is manufactured by Atmel, MC, USA. This is

the advanced version of 8031. This Micro controller have inbuilt 4K bytes of flash

ROM, 256 bytes of RAM, 32 I/O lines (4 bit ports) and 6 vectored interrupts.

CMOS technology is used in this micro controller.

FEATURES :

Extensive Boolean processing (Single - bit Logic) Capabilities.

8 Bit CPU optimized for control applications.

On - Chip Flash Program Memory.

On - Chip Data RAM.

Bi-directional and Individually Addressable I/O Lines.

Multiple 16-Bit Timer/Counters.

Full Duplex UART.

On - Chip Oscillator and Clock circuitry.

On - Chip EEPROM.

PIN DIAGRAM:

INPUT/ OUTPUT PORTS:

There are four I/O ports available in AT89C51. They are port 0, port 1, port

2, and port 3. All these ports are eight bit ports. All these ports can be controlled

as eight-bit port or it can be controlled individually. One of the main feature of this

micro controller is it can control the port pins individually. In 89C51 port 1 is

available for user, Port 3 is combined with interrupts. This can be used as

interrupts (or) I/O ports, ports 2 & port 0 is combined with address bus & data

bus.

All these port lines are available with internal pull-ups except port 0. If we

want to use port 0 as I/O port we have to use pull up resistors.

This Micro controller is working at a maximum speed of 24MHz. This

micro controller is available with inbuilt oscillator; just crystal has to be connected

to its terminal.

MEMORY ORGANIZATION:

All Atmel Flash micro controllers have separate address spaces for

program and data memory. The logical separation of program and data memory

allows the data memory to be accessed by 8 bit addresses.

Program memory can only be read. There can be up to 64K bytes of

directly addressable program memory. The read strobe for external program

memory is the Program Store Enable Signal (PSEN). Data memory occupies a

separate address space from program memory. Up to 64K bytes of external

memory can be directly addressed in the external data memory space.

The CPU generates read and write signals, RD and WR, during external

data memory accesses. External program memory and external data memory

can be combined by applying the RD and PSEN signal to the inputs of AND gate

and using the output of the fate as the read strobe to the external program/data

memory.

PROGRAM MEMORY:

After reset, the CPU begins execution from location 0000h. Each interrupt

is assigned a fixed location in program memory. The interrupt causes the CPU to

jump to that location, where it executes the service routine. If external Interrupt 0

is used, its service routine must begin at location 0003h. If the interrupt is not

used its service location is available as general-purpose program memory.

The interrupt service locations are spaced at 8 byte intervals 0003h for

External interrupt 0, 000Bh for Timer 0, 0013h for External interrupt 1,001Bh for

Timer1, and so on. If an Interrupt service routine is short enough it can reside

entirely within that 8-byte interval. Longer service routines can use a jump

instruction to skip over subsequent interrupt locations. The lowest addresses of

program memory can be either in the on-chip Flash or in an external memory. To

make this selection, strap the External Access (EA) pin to either Vcc or GND.

DATA MEMORY:

The Internal Data memory is divided into three blocks namely,

The lower 128 Bytes of Internal RAM.

The Upper 128 Bytes of Internal RAM.

Special Function Register.

Internal Data memory Addresses are always 1 byte wide, which implies an

address space of only 256 bytes. However, the addressing modes for internal

RAM can accommodate 384 bytes. Direct addresses higher than 7Fh access one

memory space and indirect addresses higher than 7Fh access a different

Memory Space.

The lowest 32 bytes are grouped into 4 banks of 8 registers. Program

instructions call out these registers as R0 through R7. Two bits in the Program

Status Word (PSW) select which register bank is in use. This architecture allows

more efficient use of code space, since register instructions are shorter than

instructions that use direct addressing.

The next 16-bytes above the register banks form a block of bit

addressable memory space. The micro controller instruction set includes a wide

selection of single - bit instructions and this instruction can directly address the

128 bytes in this area. These bit addresses are 00h through 7Fh

The Special Function Register includes Port latches, timers, peripheral

controls etc., direct addressing can only access these register. In general, all

Atmel micro controllers have the same SFRs at the same addresses. However,

upgrades to the AT89C51 have additional SFRs. Sixteen addresses in SFR

space are both byte and bit Addressable. The bit Addressable SFRs are those

whose address ends in 000B. The bit addresses in this area are 80h through

FFh.

OSCILLATOR AND CLOCK CIRCUIT:

XTAL1 and XTAL2 are the input and output respectively of an inverting

amplifier which is used as a crystal oscillator in the frequency range of 1.2 Mhz to

12 Mhz. XTAL2 is also used as the input to the internal clock generator.

To drive the chip with an internal oscillator XTAL1 and XTAL2 are

grounded. Since the input to the clock generator is divided by two flip flop there

are no requirements on the duty cycle of the external oscillator signal. However,

minimum high and low times must be observed.

The clock generator divides the oscillator frequency by 2 and provides a

two phase clock signal to the chip. The phase 1 signal is active during the first

half of each clock period and the phase 2 signals are active during the second

half of each clock period.

CPU TIMING:

A machine cycle consists of 6 states. Each state is divided into a phase /

half, during which the phase 1 clock is active and phase 2 half. Arithmetic and

Logical operations take place during phase1 and internal register to register

transfer take place during phase 2.

FLASH ROM:

4-kilo byte ROM is available in the Micro controller. It can be erased and

reprogrammed. If the available memory is not enough for program, it can be

interfaced with external ROM .It has 16 address lines, so maximum of (2^16) i.e.

64 bytes of ROM can be interfaced with this Micro controller. Both internal and

external ROM cannot be used simultaneously.

For external accessing of ROM, a pin is provided in Micro controller itself

i.e. pin no.31 EA. It should be high to use internal ROM, low to use external ROM

RAM:

Internal 256 bytes of RAM are available for user. These 256 bytes of RAM

can be used along with the external RAM. Externally 64-kilo bytes of RAM can be

connected with micro controller. In internal RAM first 128 bytes of RAM is

available for user and the remaining 128 bytes are used as special function

registers (SFR). These SFR’s are used as control registers for timer, serial port

etc.

PROGRAMS:

To program microcontrollers, the trend is to use the C language, due to its

efficiency and ease of use relative to the Assembly language makes most things

possible using the least amount of memory (code and date) and time, and offers

increased productivity.

Typically, a software developer can write more codes to do more things

using C than when using Assembly. This is important because at least half the

cost of developing an MCU application is in paying people to develop the

software.

Since C source code is standardized and portable, many people know

hoe to program in C. it can be written anywhere and then complied for the target

processor of choice. Writing microcontroller software often requires knowledge of

bits, registers, etc. C is considered to be a good language for real-time control

applications, as it has more or less compactness and speed features of the high-

level language features of portability. Also flow control is more flexible and easy

to use.

A micro controller unit (MCU) uses the microprocessor as its central

processing unit (CPU) and incorporates memory, timing reference, I/O

peripherals, etc on the same chip. Limited computational capabilities and

enhanced I/O are special features.

The micro controller is the most essential IC for continuous process-

based applications in industries like chemical, refinery, pharmaceutical

automobile, steel, and electrical, employing programmable logic systems (DCS).

PLC and DCS thrive on the programmability of an MCU.

There are many MCU manufacturers. To understand and apply general

concepts, it is necessary to study one type in detail. This specific knowledge can

be used to understand similar features of other MCU.

INTERFACING OF 89C51 TO 74HC541

CHAPTER 2

TRANSMITTER UNIT

INTRODUCTION:

Radio frequency (RF) transmitters are widely used in radio frequency

communications systems. With the increasing availability of efficient, low cost

electronic modules, mobile communication systems are becoming more and

more widespread.

A terminal apparatus used in the radio communications system receives a

radio frequency signal transmitted from a base station, by an antenna, inputs the

signal to a receiving radio-frequency unit via an antenna duplexer, high

frequency amplifies the signal, removes unnecessary waves outside the

receiving band from the signal, converts the signal to an intermediate frequency

signal, demodulates the intermediate frequency signal by a demodulator, and

converts the signal into a baseband signal.

Generally, a radio transmitter is used for performing a radio transmission

operation, whereby a high frequency signal outputted from a modulator is

transmitted to an antenna of the radio transmitter and is transmitted there from to

a remote radio transmitter thereby a signal is transmitted.

The transmitting baseband signal is subjected to a predetermined signal

process, input to a modulator, which modulates a carrier wave signal. The

modulated carrier wave signal is converted into a radio frequency by a

transmitting radio-frequency circuit and amplified to a predetermined transmitting

power, and transmitted to the base station from the antenna via the duplexer.

Communication systems are known to support wireless and wire lined

communications between wireless and/or wire lined communication devices.

The function of a radio frequency (RF) transmitter is to modulate,

upconvert, and amplify signals for transmission into free space. An RF

transmitter generally includes a modulator that modulates an input signal and a

radio frequency power amplifier that is coupled to the modulator to amplify the

modulated input signal. The radio frequency power amplifier is coupled to an

antenna that transmits the amplified modulated input signal. Power amplifiers are

required in radio telecommunication systems to amplify signals before

transmitting, because a radio signal attenuates on the radio path.

CIRCUIT OF TRANSMITTER UNIT

For efficiency, the amplifier is often a non-linear amplifier operated near its

peak capacity. To avoid distortion of the transmitted signals due to the non-

linearity, the signals are pre-distorted by a predistorter before they are

transmitted. The predistortion is required to prevent transmitter from transmitting

signals on channel bands other than the band assigned to the transmitter. The

predistortion values are chosen such that the product values entering the power

amplifier will be distorted by the power amplifier to return to a substantially linear

amplification of the modulated signals.

A direct conversion transmitter system to produce a transmission signal is

generally comprised of a low oscillator (LO), a phase locked loop (PLL), a

quadrature generator, a modulator, a power amplifier (PA), and one or more

filters. The low oscillator, coupled to the PLL, produces a signal with a frequency

that is substantially equal to the frequency of a desired RF transmission signal.

The quadrature generator is coupled to the low oscillator and the modulator.

The PA is coupled to the quadrature generator, and receives the

transmission signal and amplifies it. The amplified signal may go through a filter

to reduce noise or spurious outputs outside of the transmission band. High

quality RF transmitters typically include bandpass filters, such as surface

acoustic wave (SAW) filters provide excellent performance.

A typical system may employ a bandpass filter following the power

amplifier to reduce undesired noise present at the antenna in different portion of

RF spectrum to meet various standards' regulations and specifications.

TRANSMITTER MODULE TXC1:

The TXC1 is an ASK transmitter module .The result is excellent

performance in a simple-to-use .The TXC1 is designed specifically for remote-

control , wireless mouse and car alarm system operating at 315/433.92 MHz in

the USA under FCC Part 15 regulation. These are pre-built 433MHz wireless

transmitter / receiver modules. They feature ASK encoding, and perform very

well. They are ideal for devices using short data bursts such as remote controls,

trigger pulses etc.

SPECIFICATIONS:

Output power: 3dBm.

Supply voltage: 3V.

Supply current: 10mA max.

Data rate: 300bps to 10kbps.

PCB measures: 18.5(H) x 14.5(W) mm (excluding pins).

Transmitter Module: ZW-3100

Receiver Module: ZW-3102

Ideal for 315/433.92MHz remote keyless-entry transmitter

By SAW resonator

ASK modulation

315/433.92MHz

PIN ASSIGNMENT:

pin Connections1 GND2 DATA3 VCC4 ANT

ABSOLUTE MAXIMUM RATINGS

PARAMETER VALUE UNITS

Power supply 3 V

Operating temperature -20 to +60 °c

RECEIVER CHARACTERISTICS:

PARAMETER SYMBOL CONDITION VALUE UNIT

min typ max

Output power - Vcc=30V,

TA-27°c ,

50Ωload

315

MHz

2 3 6 dBm

434

MHz

1 3 6 dBm

Supply current Icc - 9 10 19 mA

Supply voltage

range

Vcc - - 3 - V

Data rate - - 300 1K 10K bps

TYPICAL TEST CIRCUIT

TYPICAL TRANSMITTER APPLICATION

REMARK:

Antenna Length:

22.6cm for 315 MHz

17.2 cm for 434 MHz

APPLICATIONS:

Specifically for remote-control, wireless mouse and car alarm system

operating at 315/433.92MHz in the USA under FCC Part 15 regulation

CHAPTER 3

RECEIVER UNIT

INTRODUCTION:

Receivers for communication systems generally are designed such that

they are tuned to receive one of a multiplicity of signals having widely varying

bandwidths and which may fall within a particular frequency range.

The RF receiver receives an RF signal, converts the RF signal to an IF

signal, and then converts the IF signal to a base band signal, which it then

provides to the base band processor. As is also known, RF transceivers typically

include sensitive components susceptible to noise and interference with one

another and with external sources.

The RF receiver is coupled to the antenna and includes a low noise

amplifier, one or more intermediate frequency stages, a filtering stage, and a data

recovery stage. The low noise amplifier receives an inbound RF signal via the

antenna and amplifies it.

The one or more intermediate frequency stages mix the amplified RF signal

with one or more local oscillations to convert the amplified RF signal into a base

band signal or an intermediate frequency (IF) signal.

CIRCUIT DIAGRAM OF RECEIVER UNIT:

RECEIVER MODULE RXB1:

The receiver module used in our project is ASK Super Heterodyne

Receiver Module, belongs to the category ST-RXB1. The ST- RX04-ASK is an

Ask Super Heterodyne Receiver Module with PLL Synthesizer and Crystal

Oscillator. The circuit shape is PLL.

ST- RX04

PIN DIAGRAM

SPECIFICATIONS:

Frequency Range : 315/434 MHz

Operation Voltage: 5V

IF Frequency: 500k

Typical sensitivity: -105dBm

Supply Current: 2.3Ma

FEATURES:

Low power consumption.

Easy for application.

On-chip VCO with integrated PLL using crystal oscillator reference.

Integrated IF and data filters.

Operation temperature range : -40 °c to +80 °c

MECHANICAL DIMENSIONS:

ELECTRICAL CHARACTERISTICS:

CHARACTERISTIC MIN TYP MAX UNIT

VCC Supply voltage - 5 - VDC

Is Supply Current - 2.3 3 mA

Fr Receiver

Frequency

- 315/434 - MHz

RF Sensitivity - -105 - dBm

Max Data Rate 0.3 1 3 Kbit/s

Voh High Level

Output

0.7Vcc - - VDC

Vol Low Level

Output

- - 0.3Vcc VDC

Turn On Time 25 30 - ms

Top

Operating

Temperature Range

-40 - 80 °c

Output Duty 40 - 60 %

TYPICAL APPLICATION:

REMARK:

Antenna length about:

23cm for 315 MHz

17 cm for 434 MHz

APPLICATIONS:

Car security system

Wireless security systems

Sensor reporting

Automation system

Remote Keyless entry

CHAPTER 4

ENCODER

INTRODUCTION:

An encoder can be a device used to change a signal (such as a bitstream)

or data into a code. The code serves any of a number of purposes such as

compressing information for transmission or storage, encrypting or adding

redundancies to the input code, or translating from one code to another.

This is usually done by means of a programmed algorithm, especially if

any part is digital, while most analog encoding is done with analog circuitry.

ENCODER HT12E:

The HT12E encoder is a CMOS IC built especially for remote control

system applications. It is capable of encoding 8 bits of address (A0-A7) and 4

bits of data (AD8-AD11) information. Each address/data input can be set to one

of the two logic states, 0 or 1.

Grounding the pins is taken as a 0 while a high can be given by giving +5V

or leaving the pins open (no connection). Upon reception of transmit enable

(TE-active low), the programmed address/data are transmitted together with the

header bits via an RF medium.

PIN DIAGRAM:

PIN DESCRIPTION:

Pin Name I/O Internal Connection Description

A0-A7 I NMOS

TRANSMISSION

GATE

Input pins for address A0-A7

setting. They can be externally

set to VDD or VSS.

AD8-AD11 I NMOS

TRANSMISSION

Input pins for data AD8-AD11

setting. They can be externally

set to VDD or VSS.

DOUT O CMOS OUT Encoder data serial transmission

output

TE I CMOS IN pull-high Transmission Enable, active low

OSC 1 I OSCILLATOR 1 Oscillator input pin

OSC2 O OSCILLATOR 2 Oscillator output pin

VSS I - Negative power supply(GND)

VDD I - Positive power supply

CIRCUIT DIAGRAM OF ENCODER HT12E:

FEATURES OF HT12E:

• 2.4-12V Operation

• Low power, high noise immunity CMOS technology

• Low standby current of < 1μA at 5V supply

• Built-in oscillator with only a 5% resister

• Minimal external components

ELECTRICAL CHARACTERISTICS ENCODER:

ENCODER OPERATION:

The encoder starts a 4 word transmission cycle upon reception of a

transmit enable (TE active low). This cycle repeats itself as long as TE is held

low. Once the TE goes high,the encoder completes its final cycle and stops as

shown in Fig below.

ENCODER CYCLE TIMING:

As soon as a transmit enable occurs, the encoder scans and transmits the status

of the 12 bits of address/data serially in the order A0 to AD11.

ENCODER OPERATION FLOWCHART:

Encoder operation can be represented by a flowchart as shown

in Fig .As an illustration of the way the data is sent serially, if all the 8 address

lines were left open (no connection) and all 4 data lines were grounded, then the

serial output would look like all open circuit address lines will be read as logic

high and all 4 data bits will be read as 0 since they were grounded.

ENCODER OSCILLATION FREQUENCY:

Since the encoder comes with a built in RC oscillator, its oscillation

frequency can be set by connecting a resistor between OSC1 (pin 16) and OSC2

(pin15). The oscillation frequency depends on the resistor value as well as the

supply voltage, as shown in Fig.

ENCODER OSCILLATION GRAPH:

CHAPTER 5

DECODER

INTRODUCTION:

A decoder is a device which does the reverse of an encoder, undoing the

encoding so that the original information can be retrieved. The same method

used to encode is usually just reversed in order to decode.

In digital electronics this would mean that a decoder is a multiple-input,

multiple-output logic circuit that converts coded inputs into coded outputs.

Enable inputs must be on for the decoder to function, otherwise its outputs

assume a single "disabled" output code word. Decoding is necessary in

applications such as data multiplexing, 7 segment display and memory address

decoding.

HT12D:

The HT12D is a decoder IC made especially to pair with the HT12E

encoder.it is a CMOS IC made for remote control system application. The

decoder is capable of decoding 8 bits of address (A0-A7) and 4 bits of data

(AD8-AD11) information. For proper operation, a pair of encoder/decoder with

the same number of addresses and data format should be chosen.

The decoders receive serial addresses and data from a programmed

encoders that are transmitted by a carrier using an RF or an IR transmission

medium. They compare the serial input data three times continuously with their

local addresses. If no error or unmatched codes are found, the input data codes

are decoded and then transferred to the output pins. The VT pin also goes high

to indicate a valid transmission.

The decoders are capable of decoding information that consists of N bits

of address and 12_N bits of data. Of this series, the HT12D is arranged to

provide 8 address bits and 4 data bits, and HT12F is used to decode 12 bits of

address information.

PIN DESCRIPTION:

Pin Name I/O Internal Connection Description

A0-A11 I NMOS

TRANSMISSION

GATE

Input pins for address A0-A7

setting. They can be externally

set to VSS or left open.

D8-D11 O CMOS OUT Output data pins, power on-state

is low.

DIN I CMOS IN Serial data input pin.

VT O CMOS OUT Valid Transmission, active high

OSC 1 I OSCILLATOR 1 Oscillator input pin

OSC2 O OSCILLATOR 2 Oscillator output pin

VSS I - Negative power supply(GND)

VDD I - Positive power supply

ELECTRICAL CHARACTERISTICS:

DECODER OPERATION:

HT12D receives digital serial data from its DIN(pin14). A signal in the DIN

activates the oscillator which then decodes the incoming address and data.

Decoder Timing

After decoding, it checks the serial input data three times continuously with its

local addresses. If no error or unmatched codes are found, the input data codes

are decoded and then transferred to the data output pins.This pin remains high

for 214=16384 decoder clocks after the encoder’s DOUT pin goes low. Since the

decoder operates at 150KHz, it takes 150000*16384=0.1 seconds for the VT pin

to go low. This pin also goes low if the address code is incorrect or no signal is

received.

The 4 data pins are latched to their respective pins, meaning that the

previous data remains on the pins unless a new data arrives to replace the

existing one.

FEATURES:

Operating voltage: 2.4V~12V

Low power and high noise immunity CMOS Technology

Low standby current

Capable of decoding 12 bits of information

Binary address setting

Received codes are checked 3 times

Address/Data number combination

HT12D: 8 address bits and 4 data bits

HT12F: 12 address bits only

Built-in oscillator needs only 5% resistor

Valid transmission indicator

Easy interface with an RF or an infrared transmission medium

Minimal external components

FLOWCHART:

The oscillator is disabled in the standby state and activated when a logic

highsignal applies to the DIN pin. That is to say, the DIN should be kept low if

there is no signal input.

The decoder operation can be represented by a flowchart as shown

above.

DECODER OSCILLATION FREQUENCY:

The decoder has a built in oscillator hence its clock can be set by

connecting a resistor between OSC1 (pin 16) and OSC2 (pin 15). The oscillation

frequency depends on the resistor value as well as the power supply as shown

below. This project uses a 5V supply and it is recommended by the Holtek that

oscillator frequency of decoder = 50*oscillator frequency of encoder. Since the

HT12E encoder works at 3KHz, the decoder frequency has to be 150KHz. This

requires a 51k resistor.

Fosc vs supply voltage

APPLICATIONS:

Burglar alarm system

Smoke and fire alarm system

Garage door controllers

Car door controllers

Car alarm system

Security system

Cordless telephones

Other remote control systems

CHAPTER 6

LCD DISPLAY

INTRODUCTION:

A liquid crystal display (LCD) is an electronically-modulated optical

device shaped into a thin, flat panel made up of any number of color or

monochrome pixels filled with liquid crystals and arrayed in front of a light source

(backlight) or reflector. It is often utilized in battery-powered electronic devices

because it uses very small amounts of electric power.

LCD has material, which continues the properties of both liquids and

crystals. Rather than having a melting point, they have a temperature range

within which the molecules are almost as mobile as they would be in a liquid, but

are grouped together in an ordered from similar to a crystal.

LCD consists of two glass panels, with the liquid crystal materials

sandwiched in between them. The inner surface of the glass plates is coated

with transparent electrodes which define in between the electrodes and the

crystal, which makes the liquid crystal molecules to maintain a defined orientation

angle.

When a potential is applied across the cell, charge carriers flowing

through the liquid will disrupt the molecular alignment and produce turbulence.

When the liquid is not activated, it is transparent. When the liquid is activated the

molecular turbulence causes light to be scattered in all directions and the cell

appears to be bright.Thus the required message is displayed.

When the LCD is in the off state, the two polarizer’s and the liquid

crystal rotate the light rays, such that they come out of the LCD without any

orientation, and hence the LCD appears transparent. When sufficient voltage is

applied to the electrodes the liquid crystal molecules would be aligned in a

specific direction. The light rays passing through the LCD would be rotated by

the polarizer, which would result in activating/highlighting the desired characters.

The power supply should be of +5v, with maximum allowable transients

of 10mv. To achieve a better/suitable contrast for the display the voltage (VL) at

pin 3 should be adjusted properly. A module should not be removed from a live

circuit. The ground terminal of the power supply must be isolated properly so

that voltage is induced in it. The module should be isolated properly so that stray

voltages are not induced, which could cause a flicking display.

LCD is lightweight with only a few, millimeters thickness since the LCD

consumes less power, they are compatible with low power electronic circuits, and

can be powered for long durations. LCD does not generate light and so light is

needed to read the display. By using backlighting, reading is possible in the

dark. LCDs have long life and a wide operating temperature range. Before LCD

is used for displaying proper initialization should be done.

LCDs with a small number of segments, such as those used in digital

watches and pocket calculators, have individual electrical contacts for each

segment. An external dedicated circuit supplies an electric charge to control each

segment. This display structure is unwieldy for more than a few display elements.

Small monochrome displays such as those found in personal organizers,

or older laptop screens have a passive-matrix structure employing super-twisted

nematic (STN) or double-layer STN (DSTN) technology—the latter of which

addresses a color-shifting problem with the former—and color-STN (CSTN)—

wherein color is added by using an internal filter. Each row or column of the

display has a single electrical circuit. The pixels are addressed one at a time by

row and column addresses. This type of display is called passive-matrix

addressed because the pixel must retain its state between refreshes without the

benefit of a steady electrical charge. As the number of pixels (and,

correspondingly, columns and rows) increases, this type of display becomes less

feasible. Very slow response times and poor contrast are typical of passive-

matrix addressed LCDs.

High-resolution color displays such as modern LCD computer monitors

and televisions use an active matrix structure. A matrix of thin-film transistors

(TFTs) is added to the polarizing and color filters. Each pixel has its own

dedicated transistor, allowing each column line to access one pixel. When a row

line is activated, all of the column lines are connected to a row of pixels and the

correct voltage is driven onto all of the column lines. The row line is then

deactivated and the next row line is activated. All of the row lines are activated in

sequence during a refresh operation. Active-matrix addressed displays look

"brighter" and "sharper" than passive-matrix addressed displays of the same

size, and generally have quicker response times, producing much better images.

A general purpose alphanumeric LCD, with two lines of 16 characters. So

the type of LCD used in this project is16 characters * 2 lines with 5*7 dots with

cursor, built in controller, +5v power supply, 1/16 duty cycle.

In this project LCD is used to display the following messages:

i) Device (1,2,3,4) is located.

ii) Ready to detect.

Fig. LCD

PIN DESCRIPTION FOR LCD:

Pin Symbol i/o Description

1 VSS -- Ground

2 VCC -- +5v Power Supply

3 VEE -- Power Supply To Control Contrast

4 RS I RS=0 to select command register,

RS=1 to select data register

5 R/W I R/W=0 for Write, R/W=1 for Read

6 E I/O Enable

7 DB0 I/O The 8-bit data bus

8 DB1 I/O The 8-bit data bus

9 DB2 I/O The 8-bit data bus

10 DB3 I/O The 8-bit data bus

11 DB4 I/O The 8-bit data bus

12 DB5 I/O The 8-bit data bus

13 DB6 I/O The 8-bit data bus

14 DB7 I/O The 8-bit data bus

LCD PIN DESCRIPTIONS:

The function of each pins of LCD is described below

VCC, VSS and VEE

While v and v provide +5v and ground, respectively, v is used for

controlling LCD contrast.

RS, register select

There are two very important registers inside the LCD. The RS pin is used

for their selection as follows. If RS=0, the instruction code register is selected,

allowing the user to send a command such as clear display, cursor at home,etc.if

RS=1 the data register is selected, allowing the user to send data to be displayed

on the LCD.

R/W, read/write

R/W input allows the user to write information to the LCD or read

information from it. R/W=1 when reading; R/W=0 when writing.

E, enable

The enable pin is used by the LCD to latch information presented on its

data pins. when data is supplied to data pins, a high to low pulse must be applied

to this pin in order for the LCD to latch in the data present at the data pins.

D0 - D7

The 8-bit data pins, D0 – D7, are used to send information to the LCD or

read contents of the LCD’S internal registers.

There are also instruction codes that can be sent to the LCD to clear the

display or force the cursor to the home position or blink the cursor.

RS=0 is used to check the busy flag bit to see if the LCD is ready to

receive information. The busy flag is D7 and can be read when R/W=1 and

RS=0, as follows: if R/W=1,RS=0.when D7=1,the LCD is busy taking care of

internal operation and will not accept any new information, when D7=0, the LCD

is ready to receive new information.

LCD CONNECTION:

LCD COMMAND CODES:

Code Command to LCD Instruction

1 Clear Display Screen

2 Return Home

4 Decrement cursor

6 Increment cursor

5 Shift display right

7 Shift display left

8 Display off, cursor off

A Display off, cursor on

C Display on, cursor off

E Display on, cursor blinking

F Display on, cursor blinking

10 Shift cursor position to left

14 Shift cursor position to right

18 Shift the entire display to left

1C Shift the entire display to right

80 Force cursor to beginning of first

line

C0 Force cursor to beginning of second

line

38 2 lines and 5x7 matrix

CHAPTER 7

POWER SUPPLY

INTRODUCTION:

Power supply is a reference to a source of electrical power. A device or

system that supplies electrical or other types of energy to an output load or

group of loads is called a power supply unit or PSU.

Fig Block diagram of a basic power supply

The first section is the TRANSFORMER. The transformer steps up or

steps down the input line voltage and isolates the power supply from the power

line. The RECTIFIER section converts the alternating current input signal to a

pulsating direct current. A FILTER section is used to convert pulsating dc to a

purer, more desirable form of dc voltage. The final section is the REGULATOR.

It maintains the output of the power supply at a constant level.

In fig 3, an input signal of 115 volts ac is applied to the primary of the

transformer. The transformer is a step-up transformer with a turns ratio of 1:3.

The output for this transformer can be found by multiplying the input voltage

by the ratio of turns in the primary to the ratio of turns in the secondary;

therefore, 115 volts ac 3 = 345 volts ac (peak-to- peak) at the output.

Because each diode in the rectifier section conducts for 180 degrees of the

360-degree input, the output of the rectifier will be one-half, or approximately

173 volts of pulsating dc.

The filter section, a network of resistors, capacitors, or inductors,

controls the rise and fall time of the varying signal; consequently, the signal

remains at a more constant dc level. The output of the filter is a signal of 110

volts dc, with ac ripple riding on the dc.

TYPES OF POWER SUPPLY:

There are many types of power supply. Most are designed to convert

high voltage AC mains electricity to a suitable low voltage supply for

electronics circuits and other devices. A power supply can be broken down into

a series of blocks, each of which performs a particular function.

For example a 5V regulated supply:

Block diagram of regulated power supply

Each of the blocks are described below:

Transformer - steps down high voltage AC mains to low voltage AC.

Rectifier - converts AC to DC, but the DC output is varying.

Smoothing - smoothes the DC from varying greatly to a small ripple.

Regulator - eliminates ripple by setting DC output to a fixed voltage.

Power supplies made from these blocks are described below with a circuit

diagram and a graph of their output:

Transformer only

Transformer + Rectifier

Transformer + Rectifier + Smoothing

Transformer + Rectifier + Smoothing + Regulator

Transformer only

The low voltage AC output is suitable for lamps, heaters and special AC

motors. It is not suitable for electronic circuits unless they include a rectifier

and a smoothing capacitor.

Transformer

Transformer + Rectifier

The varying DC output is suitable for lamps, heaters and standard

motors. It is not suitable for electronic circuits unless they include a

smoothing capacitor.

Transformer + rectifier

Transformer + Rectifier + Smoothing

Transformer + rectifier + smoothing

The smooth DC output has a small ripple. It is suitable for most electronic

circuits.

Transformer + Rectifier + Smoothing + Regulator

The regulated DC output is very smooth with no ripple. It is suitable for all

electronic circuits.

Dual Supplies

Some electronic circuits require a power supply with positive and

negative outputs as well as zero volts (0V). This is called a 'dual supply'

because it is like two ordinary supplies connected together as shown in the

diagram.

Dual supplies have three outputs, for example a ±9V supply has +9V,

0V and - 9V outputs.

Dual supplies

Simple 5V power supply for digital circuits

Summary of circuit features

Brief description of operation: Gives out well regulated +5V output,

output current capability of 100 mA

Circuit protection: Built-in overheating protection shuts down output

when regulator IC gets too hot

Circuit complexity: Very simple and easy to build

Circuit performance: Very stable +5V output voltage, reliable operation

Design testing: Based on datasheet example circuit, I have used this

circuit successfully as part of many electronics projects

Applications: Part of electronics devices, small laboratory power supply Power supply voltage: Unregulated DC 8-18V power supply Power supply current: Needed output current + 5 mA

Circuit description

This circuit is a small +5V power supply, which is useful when

experimenting with digital electronics. This circuit can give +5V output at

about 150 mA current, but it can be increased to 1 A when good cooling is

added to 7805 regulator chip. The circuit has overload and terminal

protection.

Circuit diagram of 5V power supply

The capacitors must have enough high voltage rating to safely handle

the input voltage feed to circuit.

Component list

7805 regulator IC

100 uF electrolytic capacitor, at least 25V voltage rating

10 uF electrolytic capacitor, at least 6V voltage rating

100 nF ceramic or polyester capacitor

CHAPTER 8

PRINTED CIRCUIT BOARD

INTRODUCTION:

A printed circuit board, or PCB, is used to mechanically support and

electrically connect electronic components using conductive pathways, or

traces, etched from copper sheets laminated onto a non-conductive substrate.

Alternative names are printed wiring board (PWB),and etched wiring board. A

PCB populated with electronic components is a printed circuit assembly (PCA),

also known as a printed circuit board assembly (PCBA).

Printed circuit board

PCBs are rugged, inexpensive, and can be highly reliable. They require

much more layout effort and higher initial cost than either wire-wrapped or

point-to-point constructed circuits, but are much cheaper and faster for high-

volume production.

MANUFACTURING

MATERIALS

Conducting layers are typically made of thin copper foil. Insulating

materials have a wider scale: phenolic paper, glass fibre and different plastics

are commonly used. Other widely used materials are polyimide, teflon and

some ceramics. The PCB board is double sided, with through-hole plating,

green solder resist, and white silkscreen printing. Both surface mount and

through-hole components have been used.

PATTERNING (ETCHING)

The majority of printed circuit boards are made by bonding a layer of

copper over the entire substrate, then removing unwanted copper after

applying a temporary mask (eg. by etching), leaving only the desired copper

traces.

Photoengraving uses a photomask and chemical etching to remove the

copper foil from the substrate.

LAMINATION

Some PCBs have trace layers inside the PCB and are called multi-layer

PCBs. These are formed by bonding together separately etched thin boards.

DRILLING

Holes are typically drilled with tiny drill bits made of solid tungsten

carbide. The drilling is performed by automated drilling machines with

placement controlled by a drill tape or drill file.The drill file describes the

location and size of each drilled hole.

EXPOSED CONDUCTOR PLATING AND COATING

The places to which components will be mounted are typically plated,

because bare copper oxidizes quickly, and therefore is not readily solderable.

Exposed copper was plated with solder by hot air solder levelling and this

solder is a tin-lead alloy.

Edge connectors, placed along one edge of some boards, are often gold

plated.

SOLDER RESIST

Areas that should not be soldered to may be covered with a polymer

solder resist (solder mask) coating. The solder resist prevents solder from

bridging between conductors and thereby creating short circuits. Solder resist

also provides some protection from the environment.

SCREEN PRINTING

Line art and text may be printed onto the outer surfaces of a PCB by

screen printing. When space permits, the screen print text can indicate

component designators, switch setting requirements, test points, and other

features helpful in assembling, testing, and servicing the circuit board. Screen

print is also known as the silk screen, or, in one sided PCBs, the red print.

TEST

Unpopulated boards may be subjected to a bare-board test where each

circuit connection (as defined in a netlist) is verified as correct on the finished

board. A computer will instruct the electrical test unit to send a small amount of

current through each contact point.

After the printed circuit board (PCB) is completed, electronic

components must be attached to form a functional printed circuit assembly, or

PCA.

CHAPTER 9

BUFFER

INTRODUCTION:

The 74HC/HCT541 are high-speed Si-gate CMOS devices and are pin

compatible with low power Schottky TTL (LSTTL). They are specified in

compliance with JEDEC standard no. 7A. The 74HC/HCT541 are octal non-

inverting buffer/line drivers with 3-state outputs. The 3-state outputs are

controlled by the output enable inputs OE1 and OE2. A HIGH on OEn causes

the outputs to assume a high impedance OFF-state. The “541” is identical to

the “540” but has non-inverting outputs.

GENERAL DESCRIPTION:

TYPICALSYMBOL PARAMETER CONDITIONS UNIT

HC HCTtPHL/

tPLHpropagation delay An to Yn CL = 15 pF; VCC

= 5 V10 12 ns

CI input capacitance 3.5 3.5 pFCPD power dissipation capacitance

per buffernotes 1 and 2 37 39 pF

REMARK:

1. CPD is used to determine the

dynamic power dissipation (PD in

W)

2. CL = output load capacitance in pF

3. VCC = supply voltage in V

4. For HC the condition is

VI = GND to VCC

5. For HCT the condition

is VI = GND to VCC

1.5 V

FEATURES:

• Non-inverting outputs

• Output capability: bus driver

• ICC category: MSI

PIN DIAGRAM;:

PIN DESCRIPTION:

PIN NO. SYMBOL NAME AND FUNCTION1, 19

2, 3, 4, 5, 6, 7, 8, 910

18, 17, 16, 15, 14, 13, 12, 1120

OE1, OE2

A0to A7GND

Y0toY7

VCC

output enable input (active LOW)data inputs

ground (0 V)bus outputs

positive supply voltage

CHAPTER 10

BUZZER

INTRODUCTION:

A buzzer or beeper is a signaling electronic device typically used in

automobiles, household appliances such as a microwave oven, or game shows.

It commonly consists of a number of switches or sensors connected to a control

unit that determines if and which button was pushed or a preset time has lapsed.

It illuminates a light on the appropriate button or control panel, and sounds a

warning in the form of a continuous or intermittent buzzing or beeping sound.

This device is based on an electromechanical system which is identical to

an electric bell without the metal gong which makes the ringing noise. these units

are anchored to a wall or ceiling and used the ceiling or wall as a sounding

board.

Another implementation with some AC-connected devices is to implement

a circuit to make the AC current into a noise loud enough to drive a loudspeaker.

ceramic-based piezoelectric sounder is a very popular buzzer which makes a

high-pitched tone. The buzzers are hooked up to "driver" circuits which varied the

pitch of the sound or pulsed the sound on and off.

The word "buzzer" comes from the rasping noise that buzzers made when

they were electromechanical devices, operated from stepped-down AC line

voltage at 50 or 60 cycles. Other sounds commonly used to indicate that a button

has been pressed are a ring or a beep.

The buzzer circuit uses a couple of resistors, a capacitor and 555 timer IC.

The 555 is setup as an astable multivibrator operating at a frequency of about

1kHz that produces a shrill noise when switched on. The frequency can be

changed by varying the 10K resistor.

This novel buzzer circuit uses a relay in series with a small audio transformer and

speaker. When the switch is pressed, the relay will operate via the transformer

primary and closed relay contact. As soon as the relay operates the normally

closed contact will open, removing power from the relay, the contacts close and

the sequence repeats, all very quickly...so fast that the pulse of current causes

fluctuations in the transformer primary, and hence secondary. The speakers tone

is thus proportional to relay operating frequency. The capacitor C can be used to

"tune" the note. The nominal value is 0.001uF, increasing capacitance lowers the

buzzers tone.

PROGRAM OF MICROCONTROLLER AT89C51

bzled1 equ 90h

bzled2 equ 91h Assigning address for led and buzzer.

bzled3 equ 92h

bzled4 equ 93h

prs equ 0a0h

prw equ 0a1h Assigning address for pins (registerselect,

pen equ 0a2h read/write,enable)

lcdd4 equ 0a4h

lcdd5 equ 0a5h

lcdd6 equ 0a6h Assigning address for lcd,data,andcommand.

lcdd7 equ 0a7h

data equ 70h

digit1 equ 51h

digit0 equ 50h

org 0000h Program initiallisation

mov p0,#0ffh

mov p1,#00h

mov p2,#00h

mov p3,#0ffh

mov a,#2ch

acall command

mov a,#0ch

acall command

mov a,#06h

acall command Lcd commands.

mov a,#01h

acall command

mov a,#80h

acall command

mov dptr,#wel

acall cont

mainloop:

mov a,p3

swap a

anl a,#0fh Main program.

mov 50h,a

cjne a,#01h,ed1

mov dptr,#device1

acall cont

setb bzled1

acall delay

sjmp mainloop

ed1: cjne a,#02h,ed2 Program subroutines including buzzer

mov dptr,#device2 and led commands.

acall cont

setb bzled2

acall delay

sjmp mainloop

ed2: cjne a,#04h,ed3

mov dptr,#device3

acall cont

setb bzled3

acall delay

sjmp mainloop

ed3: cjne a,#08h,ed4

mov dptr,#device4

acall cont

setb bzled4

acall delay

sjmp mainloop

ed4: mov dptr,#devicen

acall cont

mov p1,#00h

sjmp mainloop

cont:

mov a,#00h

movc a,@a+dptr

inc dptr

cjne a,#80h,d1

acall command

sjmp cont

d1 cjne a,#0c0h,d2

acall command

sjmp cont

d2 cjne a,#0ffh,d3

ret

d3 acall display

sjmp cont

command

acall ready

clr prs Lcd commands.

clr prw

acall succes

ret

display

acall ready

clr prw

setb prs

acall succes

ret

ready:

mov 75h,#00h

go: djnz 75h,go

ret

succes

clr prw

mov data,a

mov a,data

swap a

mov c,acc.0

mov lcdd4,c

mov c,acc.1

mov lcdd5,c

mov c,acc.2

mov lcdd6,c

mov c,acc.3

mov lcdd7,c

setb pen

clr pen

mov a,data

mov c,acc.0

mov lcdd4,c

mov c,acc.1

mov lcdd5,c

mov c,acc.2

mov lcdd6,c

mov c,acc.3

mov lcdd7,c

setb pen

clr pen

ret

delay Process delay commands.

mov r1,#10h

loop3 mov r2,#00h

loop2 mov r3,#00h

loop1 djnz r3,loop1

djnz r2,loop2

djnz r1,loop3

ret

txdelay:

mov r2,#03h

tldy3: mov r3,#00h Transmitter delay commands.

tldy2: mov r4,#00h

tldy1: djnz r4,tldy1

djnz r3,tldy2

djnz r2,tldy3

ret

sdelay:

mov r2,#01h

dly3: mov r3,#0fh

dly2: mov r4,#10h

dly1: djnz r4,dly1

djnz r3,dly2

djnz r2,dly3

ret

wel

db 80h," Device Locator ",0ffh

device1:

db 0c0h,"Device 1 Located",0ffh Assgning address for

characters to display in lcd.

device2:

db 0c0h,"Device 2 Located",0ffh

device3:

db 0c0h,"Device 3 Located",0ffh

device4:

db 0c0h,"Device 4 Located",0ffh

devicen:

db 0c0h,"Ready to detect ",0ffh