Main Project Repor

8/2/2019 Main Project Repor

1/59

CHAPTER 1

INTRODUCTION

While travelling in air, there is a finite possibility of colliding with the objects thatappear in the surroundings. By using a Ultra sonic sensor and Direction sensor, we can detect

an objects accuarte position and get it displayed on the LCD screen so that one can prevent

collisions with that object by detecting it before hand and take necessary measures. Hence we

propose our model Indication of Object position based on Radar principle.

1.1 Requirements of the Project

Power Supply.

Micro Controller.

LCD.

Buzzer.

RF Transmitter and Receiver.

RF Encoder and Decoder.

Ultra Sonic sensor.

Direction sensor.

Stepper motor.

MAX232 and Rs232.

1.2 Why we are using 89s52 microcontroller

The AT89s52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K

bytes of Flash programmable and erasable read only memory (PEROM). The device is

manufactured using Atmels high-density nonvolatile memory technology and is compatible

with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the

1


2/59

program memory to be reprogrammed in-system or by a conventional nonvolatile memory

programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel

AT89s52 is a powerful microcomputer which provides a highly-flexible and cost-effective

solution to many embedded control applications.

1.3 Organization of Report

In chapter 2 the overall system block diagram of Indication of Object position

based on Radar principle is explained.

In chapter 3 the AT89S52 microcontroller, its internal structure and all its

components are explained.

In chapter 4 describes the power supply block diagram, LCD, Ultrasonic sensor,

Direction sensor, Stepper motor and RF transmitter and receiver is also explained.

The software code written in embedded C for the system is given with the helpof flow chart in chapter 5.

Results obtained and conclusions are presented in chapter 6.

The maximum ratings and DC characteristics of the LM7805 voltage regulator are

presented in appendix A . Finally the references are given.

2


3/59

CHAPTER 2

BLOCK DIAGRAM EXPLAINATION

This chapter deals with Indication of object position based on radar principle in which

all the components are embedded together and the circuit diagram are presented.

2.1Block Diagram

Indication of object position based on radar principle consists of microcontroller, LCD,

power Supply, Max 232, Ultrasonic sensor, Direction Sensor, RF transmitters and

Receivers, RF Encoders and Decoders and stepper motor.

3

89s52

Micro

Controller

Ultrasonic

Directio

n

NRF

Driver

Power


4/59

Receiver:

Fig. 2.1 Block Diagram of Indication of object position based on radar principle

Block Diagram Description

The brief Function of each block is given below

Micro controller

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with

8Kbytes of in-system programmable Flash memory. The device is manufactured using Atmels

high-density non-volatile memory technology and is compatible with the industry-standard

80C51 instruction set and pin-out. The on-chip Flash allows the program memory to be

reprogrammed in-system or by a conventional non-volatile memory programmer. By

combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the

4

Stepper Motor

Max23289s52

RF

ReceiverPC

(VB)

LCD


5/59

Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-

effective solution to many embedded control applications

LCD

LCD is a Liquid Crystal Display. It is used to display the outputs. LCDs can add a lot to

our application in terms of providing a useful interface for the user, debugging an application

or just giving it a "professional" look.

Power supply

In this power supply circuit we have to create a +5V DC which is given to the micro

controller. The below components are used to create the power supply.

Fig. 2.2 Block Diagram of Power Supply

Direction sensor

A magnetometer is a scientific instrument used to measure the strength and/or direction

of the magnetic field in the vicinity of the instrument. Magnetism varies from place to place

and differences in Earth's magnetic field (the magnetosphere) can be caused by the differing

nature of rocks and the interaction between charged particles from the Sun and the

magnetosphere. Magnetometers are a frequent component instrument on spacecraft that

explore planets.

Ultrasonic sensors

Ultrasonic sensors (also known as transceivers when they both send and receive) work

on a principle similar to radar or sonar which evaluate attributes of a target by interpreting the

echoes from radio or sound waves respectively. Ultrasonic sensors generate high frequency

sound waves and evaluate the echo which is received back by the sensor. Sensors calculate the

5

230V AC

Supply

Step down

transformer

Bridge

rectifierFilter Regulator
http://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Earth's_magnetic_fieldhttp://en.wikipedia.org/wiki/Magnetospherehttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Earth's_magnetic_fieldhttp://en.wikipedia.org/wiki/Magnetospherehttp://en.wikipedia.org/wiki/Sun


6/59

time interval between sending the signal and receiving the echo to determine the distance to an

object.

RF transmitters and Receivers

The STT-433 is ideal for remote control applications where low cost and longer range is

required. The transmitter operates from a1.5-12V supply, making it ideal for battery-powered

applications. The transmitter employs a SAW-stabilized oscillator, ensuring accurate frequency

control for best range performance.

The data is received by the RF receiver from the antenna pin and this data is available

on the data pins. Two Data pins are provided in the receiver module. Thus, this data can be

used for further applications.

RF Encoders and Decoders

The microcontroller sends the data to the transmitter, the transmitter is not able to

accept this data as this will be not in the radio frequency range. Thus, we need an intermediate

device which can accept the input from the microcontroller, process it in the range of radio

frequency range and then send it to the transmitter. Thus, an encoder is used.

. The data transmitted into the air is received by the receiver. The received data is taken

from the data line of the receiver and is fed to the decoder .The output of decoder is given to

microcontroller and then data is processed according to the applications.

Max 232

A line driver required to convert RS232 voltage levels to TTL levels, and vice versa. It

includes a capacitive voltage generator to supply TIA/EIA-232-F voltage levels from a single

5-V supply. Each receiver converts TIA/EIA-232-F inputs to 5-V TTL/CMOS levels. These

receivers have a typical threshold of 1.3 V, a typical hysteresis of 0.5 V, and can accept 30-V

inputs. Each driver converts TTL/CMOS input levels into TIA/EIA-232-F levels.

Stepper Motor

6


7/59

A stepper motor is a widely used device that translates electrical pulses into mechanical

movement. The stepper motor is used for position control in applications such as disk drives,

dot matrix printers and robotics.

CHAPTER 3

MICRO CONTROLLER (AT 89s52)

This chapter introduces features of the AT89S52 microcontroller, architecture,

pin diagram, oscillator characteristics, addressing modes.

Born of parallel developments in computer architecture and integrated circuit

fabrications, the microprocessor or computer on chip first becomes a commercial reality in

1971. With the introduction of the 4 bit 4004 by a small, unknown company by the name

of Intel corporation other, well established, semiconductor firms soon followed Intels

pioneering technology, so that by the late 1970s we could choose from a half dozen or so

microprocessor types.

The 1970s also saw the growth of the number of the personal computer users from

a handful of hobbyists and hackers to millions of business, industrial, governmental,

defense, and educational and private users now enjoying the advantages of inexpensive

computing.

3.1 Features

Compatible with MCS-51 Products

8K Bytes of In-System Programmable (ISP) Flash Memory

Endurance: 1000 Write/Erase Cycles

4.0V to 5.5V Operating Range

7


8/59

Fully Static Operation: 0 Hz to 33 MHz

Three-level Program Memory Lock

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Three 16-bit Timer/Counters

Full Duplex UART Serial Channel

Low-power Idle and Power-down Modes

Interrupt Recovery from Power-down Mode

Watchdog Timer

Dual Data Pointer

3.2 Architecture of AT89S52

The Architecture of AT89S52 provides the following standard features: 8K bytes

of Flash, 256 bytes of RAM, 32 I/O lines, watchdog timer, two data pointers, three 16-bit

timer/counters, full duplex serial port, on-chip oscillator, and clock circuitry as shown in

8


9/59

9


10/59

Fig. 3.1 Architecture of Microcontroller AT89S52

In addition, the AT89S52 is designed with static logic for operation down to zero

frequency and supports two software selectable power saving modes. The idle mode stops

the CPU while allowing the RAM timer/counters, serial port, and interrupt system to

continue functioning. The power-down mode saves the RAM contents but freezes the

oscillator, disabling all other chip functions until the next interrupt or hardware reset.

3.3 Pin Diagram of AT89S52

The 40 pin Dual- In- Line package of AT89S52 microcontroller is shown in

Fig.3.2.

10


11/59

Fig. 3.2 Pin diagram of Microcontroller AT89S52

3.3.1 Pin Description of AT89S52

Vcc

Supply voltage.

GND

Ground.

Port 0

11


12/59

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can

sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high

impedance inputs. Port 0 can also be configured to be the multiplexed low order

address/data bus during access to external program and data memory. In this mode, P0 has

internal pull-ups. Port 0 also receives the code bytes during Flash programming and

outputs the code bytes during program verification. External pull-ups are required during

program verification.

Port 1

Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output

buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled

high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are

externally being pulled low will source current because of the internal pull-ups addition, P1.0

and P1.1 can be configured to be the timer/counter 2 external count input (P1.0/T2) and the

timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the following Table 3.1.

Port 1 also receives the low-order address bytes during Flash programming and verification.

Table 3.1 Port 1 Pin Details

Port Pin Alternate Functions

P1.0 T2 (external count input to

Timer/Counter 2),

clock-out

P1.1 T2EX (Timer/Counter 2 capture/reload

trigger

and direction control)

12


13/59

P1.5 MOSI (used for In-System

Programming)

P1.6 MISO (used for In-System

Programming)

P1.7 SCK (used for In-System

Programming)

Port 2


buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are

pulled high by the internal pull-ups and can be used as inputs.

Port 2 emits the high-order address byte during fetches from external program

memory and during access to external data memory that uses 16-bit addresses (MOVX

@DPTR). In this application, Port 2 uses strong internal pull-ups when emitting 1s

During access to external data memory that uses 8-bit addresses (MOVX @ RI),

Port 2 emits the contents of the Special Function Register. Port 2 also receives the high-

order address bits and some control signals during Flash programming and verification.

Port 3


buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are

pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that

are externally being pulled low will source current because of the pull-ups. Port 3 also

serves the functions of various special features of the AT89C52, as shown in the following

Table 3.2. Port 3 also receives some control signals for Flash programming and

verification.

Table 3.2 Alternative function of Port 3 Pins

13


14/59

RST

Reset input. A high on this pin for two machine cycles while the oscillator is running

resets the device. This pin drives high for 96 oscillator periods after the watchdog times out.

The DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In the

default state of bit DISRTO, the RESET HIGH out feature is enabled.

ALE/PROG

Address Latch Enable (ALE) is an output pulse for latching the low byte of the address

during access to external memory. This pin is also the program pulse input (PROG) during

Flash programming. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator

14

Port Pin Alternate Functions

P3.0 RXD (serial input port)

P3.1 TXD (serial output port)

P3.2 INT0 (external interrupt 0)

P3.3 INT1 (external interrupt 1)

P3.4 T0 (timer 0 external input)

P3.5 T1 (timer 1 external input)

P3.6 WR (external data memory write strobe)

P3.7 RD (external data memory read strobe)


15/59

frequency and may be used for external timing or clocking purposes. Note, however, that one

ALE pulse is skipped during each access to external data Memory. If desired, ALE operation

can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only

during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the

ALE-disable bit has no effect if the microcontroller is in external execution mode.

PSEN

Program Store Enable (PSEN) is the read strobe to external program memory.

When the AT89C52 is executing code from external program memory, PSEN is activated

twice each machine cycle, except that two PSEN activations are skipped during each

access to external data memory.

EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the device

to fetch code from external program memory locations starting at 0000H up to FFFFH.

Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. A

should be strapped to VCC for internal program executions. This pin also receives the 12-

volt Programming enables voltage (VPP) during Flash programming.

XTAL1

Input to the inverting oscillator amplifier and input to the internal clock operating

circuit.

XTAL2

Output from the inverting oscillator amplifier.

3.3.2 Oscillator Characteristics

15


16/59

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

amplifier that can be configured for use as an on-chip oscillator, as shown in Figure3.3.

Either a quartz crystal or ceramic resonator may be used. To drive the device from an

external clock source, XTAL2 should be left unconnected while XTAL1 is driven. Fig 3.3

shows the oscillator connections.

Fig. 3.3 Oscillator Connection

3.4 Addressing Modes

An addressing mode refers to the address of a given memory location. In

summary, the addressing modes are as follows, with an example of each:

Immediate Addressing MOV A, #20 H

Direct Addressing MOV A, 30 H

Indirect Addressing MOV A, @R0

Immediate Addressing

16


17/59

Immediate addressing is so named because the value to be stored in memory

immediately follows the operation code in memory. That is to say, the instruction itself

dictates what value will be stored in memory.

MOV A, #20H

This instruction uses immediate addressing because the accumulator will be

loaded with the value that immediately follows, in this case 20(hexadecimal). Immediate

addressing is very fast since the value to be loaded is included in the instruction. However,

since the value to be loaded is fixed at compile time it is not very flexible.

Direct Addressing

Direct addressing is so named because the value to be stored in memory is

obtained by directly retrieving it from another memory location.

MOV A, 30H

This instruction will read the data out of internal RAM address 30(hexadecimal)

and store it in the accumulator. Direct addressing is generally fast since, although the value

to be loaded isnt included in the instruction, it is quickly accessible since it is stored in the

8051s internal RAM. It is also much more flexible than immediate addressing since the

value to be loaded is whatever is found at the given address which may be variable. Also

it is important to note that when using direct addressing any instruction that refers to an

address between 00h and 7FH is referring to the SFR control registers that control the

89S52 microcontroller itself.

Indirect Addressing

Indirect addressing is a very powerful addressing mode, which in many cases

provides an exceptional level of flexibility. Indirect addressing is also the only way to

17


18/59

access the extra 128 bytes of internal RAM found on the 8052. Indirect addressing appears

as below.

MOV A, @R0

This instruction causes the 89S52 to analyze Special Function Register Memory.

Special Function Registers (SFR) is areas of memory that control specific functionality of

the 89S52 processor.

3.5 Modes of Operation

Idle Mode

In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain

active. The mode is invoked by software. The content of the on-chip RAM and all the special

functions registers remain unchanged during this mode. The idle mode can be terminated by

any enabled interrupt or by a hardware reset. Note that when idle mode is terminated by a

hardware reset, the device normally resumes program execution from where it left off, up to

two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits

access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate

the possibility of an unexpected write to a port pin when idle mode is terminated by a reset, the

instruction following the one that invokes idle mode should not write to a port pin or to

external memory.

Power down Mode

In the power-down mode, the oscillator is stopped, and the instruction that invokes

power-down is the last instruction executed. The on-chip RAM and Special Function Registers

retain their values until the power-down mode is terminated. Exit from power-down mode can

be initiated either by a hardware reset or by an enabled external interrupt. Reset redefines theSFRs but does not change the on-chip RAM. The reset should not be activated before VCC is

restored to its normal operating level and must be held active long enough to allow the

oscillator to restart and stabilize.

18


19/59

3.6 Watchdog Timer(WDT)

(One-time Enabled with Reset-out)

The WDT is intended as a recovery method in situations where the CPU may be

subjected to software upsets. The WDT consists of a 13-bit counter and the Watchdog Timer

Reset (WDTRST) SFR. The WDT is defaulted to disable from exiting reset. To enable the

WDT, a user must write 01EH and 0E1H in sequence to the WDTRST register (SFR location

0A6H). When the WDT is enabled, it will increment every machine cycle while the oscillator

is running. The WDT timeout period is dependent on the external clock frequency. There is no

way to disable the WDT except through reset (either hardware reset or WDT overflow reset).

When WDT overflows, it will drive an output RESET HIGH pulse at the RST pin.

3.7 Timers and Counters

Timer 0 and Timer 1

The Timer or Counter function is selected by control bits C/T in the Special

Function Register TMOD. These two Timer/Counters have four operating modes, which are

selected by bit-pairs (M1, M0) in TMOD. Modes 0, 1, and 2 are the same for both

Timers/Counters. Mode 3 is different. The four operating modes are described as follows

Mode 0

Putting either Timer into Mode 0 makes it look like an 8048 Timer, which is an 8-bit

Counter with a divide-by-32 prescaler. In mode 0, the Timer register is configured as a 13-bit

register. As the count rolls over from all 1s to all 0s, it sets the Timer interrupt flag TF1. The

counted input is enabled to the Timer when TR1 = 1 and either GATE = 0 or INT1 = 1.

(Setting GATE = 1 allows the Timer to be controlled by external input INT1, to facilitate pulse

width measurements). TR1 is a control bit in the Special Function Register TCON (Figure 4).

GATE is in TMOD. The 13-bit register consists of all 8 bits of TH1 and the lower 5 bits of

TL1. The upper 3 bits of TL1 are indeterminate and should be ignored. Setting the run flag

19


20/59

(TR1) does not clear the registers. Mode 0 operation is the same for the Timer 0 as for Timer 1.

There are two different GATE bits, one for Timer 1 (TMOD.7) and one for Timer0 (TMOD.3).

Mode 1

Mode 1 is the same as Mode 0, except that the Timer register is being run with all 16

bits.

Mode 2

Mode 2 configures the Timer register as an 8-bit Counter (TL1) with automatic reload

Overflow from TL1 not only sets TF1, but also reloads TL1 with the contents of TH1, which is

preset by software. The reload leaves TH1 unchanged. Mode 2 operation is the same for

Timer/Counter 0.

Mode 3

Timer 1 in Mode 3 simply holds its count. The effect is the same as setting TR1 = 0.

Timer 0 in Mode 3 establishes TL0 and TH0 as two separate counters. The logic for Mode 3 on

Timer 0 is shown in Figure 3.4. TL0 uses the Timer 0 control bits: C/T, GATE, TR0, INT0,

and TF0. TH0 is locked into a timer function (counting machine cycles) and takes over the use

of TR1 and TF1 from Timer 1. Thus, TH0 now controls the Timer 1 interrupt. Mode 3 is

provided for applications requiring an extra 8-bit timer on the counter. With Timer 0 in Mode

3, an 89s52 can look like it has five timer/Counters. When Timer 0 is in Mode 3, Timer 1 can

be turned on and off by switching it out of and into its own Mode 3, or can still be used by the

serial port as a baud rate generator, or in fact, in any application not requiring an interrupt.

20


21/59

Fig. 3.4 TMOD register

Fig. 3.5 TCON register

Timer 2

Timer 2 is a 16-bit Timer/Counter that can operate as either a timer or an event counter.

The type of operation is selected by bit C/T2 in the SFR T2CON. Timer 2 has three operating

modes shown in table 3: capture, auto-reload (up or down counting), and baud rate generator.

21


22/59

The modes are selected by bits in T2CON, as shown in Table 3.6 Timer 2 consists of two 8-bit

registers, TH2 and TL2. In the Timer function, the TL2 register is incremented every machine

cycle. Since a machine cycle consists of 12 oscillator periods, the count rate is 1/12 of the

oscillator frequency.

Table. 3.6 Timer 2 operating modes

In the counter function, the register is incremented in response to a 1-to-0 transition at

its corresponding external input pin, T2.

Capture mode

In the capture mode, two options are selected by bit EXEN2 in T2CON. If EXEN2 =

0, Timer 2 is a 16-bit timer or counter which upon overflow sets bit TF2 in T2CON. This bit

can then be used to generate an interrupt. If EXEN2 = 1, Timer 2 performs the same operation,

but a 1- to-0 transition at external input T2EX also causes the current value in TH2 and TL2 to

be captured into RCAP2H and RCAP2L, respectively. In addition, the transition at T2EX

causes bit EXF2 in T2CON to be set. The EXF2 bit, like TF2, can generate an interrupt. The

capture mode is illustrated in Figure

22


23/59

Fig. 3.6 Timer in capture mode

Auto-reload (Up or Down Counter)

Timer 2 can be programmed to count up or down when configured in its 16-bit auto-

reload mode. This feature is invoked by the DCEN (Down Counter Enable) bit located in the

SFR T2MOD. Upon reset, the DCEN bit is set to 0 so that timer 2 will default to count up.

When DCEN is set, Timer 2 can count up or down, depending on the value of the T2EX pin.

Fig. 3.7 Timer 2 in auto reload mode

Figure 3.7 shows Timer 2 automatically counting up when DCEN=0. In this mode, two

options are selected by bit EXEN2 in T2CON. If EXEN2 = 0, Timer 2 counts up to 0FFFFH

and then sets the TF2 bit upon overflow. The overflow also causes the timer registers to be

reloaded with the 16-bit value in RCAP2H and RCAP2L. The values in Timer in Capture

23


24/59

ModeRCAP2H and RCAP2L are preset by software. If EXEN2 = 1, a 16-bit reload can be

triggered either by an overflow or by a 1-to-0 transition at external input T2EX. This transition

also sets the EXF2 bit. Both the TF2 and EXF2 bits can generate an interrupt if enabled.

Rate Generator

Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in

T2CON. Note that the baud rates for transmit and receive can be different if Timer 2 is used for

the receiver or transmitter and Timer 1 is used for the other function.

The baud rates in Modes 1 and 3 are determined by Timer 2s overflow rate according

to the following equation.

The Timer can be configured for either timer or counter operation. In most applications,

it is configured for timer operation The timer operation is different for Timer 2 when it is used

as a baud rate generator.

Normally, as a timer it increments every machine cycle (at 1/12 the oscillator

frequency).As a baud rate generator, however, it increments every state time (at 1/2 the

oscillator frequency).

The baud rate formula is given below.

where (RCAP2H, RCAP2L) is the content of RCAP2H and RCAP2L taken as a 16-bit

unsigned integer.

3.8 Interrupts

24


25/59

The AT89S52 has a total of six interrupt vectors: two external interrupts (INT0

and INT1), three timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. These

interrupts are all shown in Figure3.8.

Each of these interrupt sources can be individually enabled or disabled by setting or

clearing a bit in Special Function Register IE. IE also contains a global disable bit, EA, which

disables all interrupts at once. In the AT89S51, bit position IE.5 is also unimplemented. User

software should not write 1s to these bit positions, since they may be used in future AT89

products. Timer 2 interrupt is generated by the logical OR of bits TF2 and EXF2 in register

T2CON.

Fig. 3.8 Interrupt sources

Neither of these flags is cleared by hardware when the service routine is vectored to. In

fact, the service routine may have to determine whether it was TF2 or EXF2 that generated the

interrupt, and that bit will have to be cleared in software. The Timer 0 and Timer 1 flags, TF0

and TF1, are set at S5P2 of the cycle in which the timers overflow. The values are then polled

by the circuitry in the next cycle. However, the Timer 2 flag, TF2, is set at S2P2 and is polled

in the same cycle in which the timer overflows.

CHAPTER 4

25


26/59

HARDWARE IMPLEMENTATION

4.1 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 d.c

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.

Fig. 4.1 Power Supply

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.

26

RegulatorFilterBridge

Rectifier

Step down

transformer

230V AC

50HzD.C

Output


27/59

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.

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.

Voltage regulator

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 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 Soil Moisture sensor is a high performance and accurate soil moisture sensor. It measures

soil moisture from 0 to 200 centibar (cb). The Soil Moisture sensor includes the

WATERMARK soil moisture sensor, Fouriers adaptor and BNC/alligator cable.

4.2 LCD

In 1968, RCA Laboratories developed the first liquid crystal display (LCD). Since then,

LCDs have been implemented on almost all types of digital devices, from watches to

computer to projection TVs .LCDs operate as a light valve, blocking light or allowing it to

pass through. An image in an LCD is formed by applying an electric field to alter the chemical

properties of each LCC (Liquid Crystal Cell) in the display in order to change a pixels light

27


28/59

absorption properties. These LCCs modify the image produced by the backlight into the

screen output requested by the controller. Through the end output may be in color, the LCCs

are monochrome, and the color is added later through a filtering process. Modern laptop

computer displays can produce 65,536 simultaneous colors at resolution of 800 X 600.

To understand the operation of an LCD, it is easiest to trace the path of a light ray from

the backlight to the user. The light source is usually located directly behind the LCD, and can

use either LED or conventional fluorescent technology. From this source, the light ray will

pass through a light polarizer to uniformly polarize the light so it can be acted upon by the

liquid crystal (LC) matrix. The light beam will then pass through the LC matrix, which will

determine whether this pixel should be on or off. If the pixel is on, the liquid crystal cell

is electrically activated, and the molecules in the liquid will align in a single direction. This

will allow the light to pass through unchanged. If the pixel is off, the electric field is

removed from the liquid, and the molecules with in scatter. This dramatically reduces the light

that will pass through the display at that pixel.

Fig. 4.2 General Purpose Alphanumeric LCD

Interfacing LCD To The Microcontroller

This is the first interfacing example for the parallel port. We will star with something

simple. This example does not use the Bi-directional feature found on newer ports, thus it

should work with most, if no all Parallel Ports. It however does not show the use of the status

port as an input. So what are we interfacing? A 16 Character X 2 Line LCD Module to the

28


29/59

Parallel Port. These LCD Modules are very common these days, and are quite simple to work

with, as all the logic required running them is on board.

Features

Interface with either 4-bit or 8-bit microprocessor.

Display data RAM

Character generator ROM

160 different 5 and 7 dot-matrix character patterns.

Character generator RAM

8 different user programmed 5 and 7 dot-matrix patterns.

Display data RAM and character generator RAM may be

accessed by the microprocessor.

Numerous instructions

Clear Display, Cursor Home, Display ON/OFF, Cursor

ON/OFF, Blink Character, Cursor Shift, Display Shift.

Built-in reset circuit is triggered at power ON.

Pin Configuration

Fig. 4.3 Pin Configuration of 2x16 Character LCD Display

29


30/59

Vcc and Vss are supply pins and VEE (Pin no.3) is used for controlling LCD contrast.

Pin No.4 is Rs pin for selecting the register, there are two very important registers are there in

side the LCD. The RS pin is used for their selection as follows. If RS=0, the instruction

command code register is selected, allowing the user to send data to be displayed on the LCD.

R/W is a read or writes Pin, which allows the user to write information to the LCD or read

information from it. R/W=1 when reading R/W=0 when writing. The LCD to latch information

presented to its data pins uses the enable (E) pin. The 8-bit data pins, D0-D7, are used to send

information to the LCD or read the contents of the LCDs internal registers. To display letters

and numbers, we must send ASCII codes for the letters A-Z, and number 0 -9 to these pins

while making RS=1.

Table 4.1 Pin Configurations of LCD Display

30


31/59

Lcd Interfacing With The Microcontroller

Fig. 4.4 Lcd Interfacing With The Microcontroller

4.3 DIRECTION SENSOR

A magnetometer is a scientific instrument used to measure the strength and/or

direction of the magnetic field in the vicinity of the instrument. Magnetism varies from place to

place and differences in Earth's magnetic field can be caused by the differing nature of rocks

and the interaction between charged particles from the Sun and the magnetosphere.

Magnetometers are a frequent component instrument on spacecraft that explore planets.

Fig. 4.5 Magnetometer

31

Vcc

Gn

d

PRESET

(CONTRAST

CONTROL)

VccFOR

BACKLIGHT

PURPOSE

P2.0

P2.

1

P2.

2

AT89s52

P0.0

4 (RS)1

5 (R/W)

2

6(EN)

3

LCD

Gnd
http://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Earth's_magnetic_fieldhttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Earth's_magnetic_fieldhttp://en.wikipedia.org/wiki/Sun


32/59

Magnetometers can be divided into two basic types:

Scalar magnetometers measure the total strength of the magnetic field to which they are

subjected, and

Vector magnetometers have the capability to measure the component of the magnetic

field in a particular direction, relative to the spatial orientation of the device.

The use of three orthogonal vector magnetometers allows the magnetic field strength,

inclination and declination to be uniquely defined. Examples of vector magnetometers are

fluxgates, superconducting quantum interference devices (SQUIDs), and the atomicSERF

magnetometer. Some scalar magnetometers are discussed below.

A magnetograph is a special magnetometer that continuously records data.

Uses

Magnetometers are used in ground-based electromagnetic geophysical surveys(such as

magnetotellurics and magnetic surveys) to assist with detecting mineralization and

corresponding geological structures. Airborne geophysical surveys use magnetometers that can

detect magnetic field variations caused by mineralization, using airplanes like the Shrike

Commander. Magnetometers are also used to detect archaeological sites, shipwrecks and other

buried or submerged objects, and in metal detectors to detect metal objects, such as guns in

security screening. Magnetic anomaly detectorsdetect submarines for military purposes.

They are used in directional drilling for oil or gas to detect the azimuth of the drilling

tools near the drill bit. They are most often paired up with accelerometersin drilling tools so

that both the inclination and azimuth of the drill bit can be found.

Magnetometers are very sensitive, and can give an indication of possible auroral

activity before one can see the light from the aurora. A grid of magnetometers around the

world constantly measures the effect of the solar wind on the Earth's magnetic field, which is

published on the K-index.

32
http://en.wikipedia.org/wiki/Spatial_orientationhttp://en.wikipedia.org/wiki/Superconducting_quantum_interference_devicehttp://en.wikipedia.org/wiki/SERFhttp://en.wikipedia.org/wiki/SERFhttp://en.wikipedia.org/wiki/Geophysical_surveyhttp://en.wikipedia.org/wiki/Geophysical_surveyhttp://en.wikipedia.org/wiki/Magnetotelluricshttp://en.wikipedia.org/wiki/Magnetic_survey_(archaeology)http://en.wikipedia.org/wiki/Shrike_Commanderhttp://en.wikipedia.org/wiki/Shrike_Commanderhttp://en.wikipedia.org/wiki/Archaeological_sitehttp://en.wikipedia.org/wiki/Shipwreckhttp://en.wikipedia.org/wiki/Metal_detectorhttp://en.wikipedia.org/wiki/Magnetic_anomaly_detectorhttp://en.wikipedia.org/wiki/Magnetic_anomaly_detectorhttp://en.wikipedia.org/wiki/Submarinehttp://en.wikipedia.org/wiki/Directional_drillinghttp://en.wikipedia.org/wiki/Azimuthhttp://en.wikipedia.org/wiki/Accelerometershttp://en.wikipedia.org/wiki/Accelerometershttp://en.wikipedia.org/wiki/Inclinationhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Auroral_lighthttp://en.wikipedia.org/wiki/Auroral_lighthttp://en.wikipedia.org/wiki/K-indexhttp://en.wikipedia.org/wiki/K-indexhttp://en.wikipedia.org/wiki/Spatial_orientationhttp://en.wikipedia.org/wiki/Superconducting_quantum_interference_devicehttp://en.wikipedia.org/wiki/SERFhttp://en.wikipedia.org/wiki/Geophysical_surveyhttp://en.wikipedia.org/wiki/Magnetotelluricshttp://en.wikipedia.org/wiki/Magnetic_survey_(archaeology)http://en.wikipedia.org/wiki/Shrike_Commanderhttp://en.wikipedia.org/wiki/Shrike_Commanderhttp://en.wikipedia.org/wiki/Archaeological_sitehttp://en.wikipedia.org/wiki/Shipwreckhttp://en.wikipedia.org/wiki/Metal_detectorhttp://en.wikipedia.org/wiki/Magnetic_anomaly_detectorhttp://en.wikipedia.org/wiki/Submarinehttp://en.wikipedia.org/wiki/Directional_drillinghttp://en.wikipedia.org/wiki/Azimuthhttp://en.wikipedia.org/wiki/Accelerometershttp://en.wikipedia.org/wiki/Inclinationhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Auroral_lighthttp://en.wikipedia.org/wiki/K-index


33/59

A three-axis fluxgate magnetometer was part of the Mariner 2 and Mariner 10

missions. A dual technique magnetometer is part of the Cassini-Huygens mission to explore

Saturn. This system is composed of a vector helium and fluxgate magnetometers.[5]

Magnetometers are also a component instrument on the Mercury MESSENGERmission. A

magnetometer can also be used by satellites like GOES to measure both the magnitude and

direction of a planet's or moon's magnetic field.

4.4 ULTRASONIC SENSOR

Ultrasonic sensors (also known as transceivers when they both send and receive) work

on a principle similar to radar or sonar which evaluate attributes of a target by interpreting the

echoes from radio or sound waves respectively. Ultrasonic sensors generate high frequency

sound waves and evaluate the echo which is received back by the sensor. Sensors calculate the

time interval between sending the signal and receiving the echo to determine the distance to an

object.

This technology can be used for measuring: wind speed and direction (anemometer),

fullness of a tank and speed through air or water. For measuring speed or direction a device

uses multiple detectors and calculates the speed from the relative distances to particulates in the

air or water. To measure the amount of liquid in a tank, the sensor measures the distance to thesurface of the fluid. Further applications include: humidifiers, sonar, medical ultrasonography,

burglar alarms and non-destructive testing.

Systems typically use a transducer which generates sound waves in the ultrasonic

range, above 18,000 hertz, by turning electrical energy into sound, then upon receiving the

echo turn the sound waves into electrical energy which can be measured and displayed.

The technology is limited by the shapes of surfaces and the density or consistency of

the material. For example foam on the surface of a fluid in a tank could distort a reading.

33
http://en.wikipedia.org/wiki/Magnetometer#Fluxgate_magnetometerhttp://en.wikipedia.org/wiki/Magnetometer#Fluxgate_magnetometerhttp://en.wikipedia.org/wiki/Magnetometer#Fluxgate_magnetometerhttp://en.wikipedia.org/wiki/Mariner_2http://en.wikipedia.org/wiki/Mariner_10http://en.wikipedia.org/wiki/Mariner_10http://en.wikipedia.org/wiki/Cassini-Huygenshttp://en.wikipedia.org/wiki/Magnetometer#Vector_heliumhttp://en.wikipedia.org/wiki/Magnetometer#Fluxgate_magnetometerhttp://en.wikipedia.org/wiki/Magnetic_field_sensors#cite_note-4http://en.wikipedia.org/wiki/Magnetic_field_sensors#cite_note-4http://en.wikipedia.org/wiki/MESSENGERhttp://en.wikipedia.org/wiki/GOEShttp://en.wikipedia.org/wiki/Magnitude_(mathematics)http://en.wikipedia.org/wiki/Direction_(geometry,_geography)http://en.wikipedia.org/wiki/Humidifierhttp://en.wikipedia.org/wiki/Sonarhttp://en.wikipedia.org/wiki/Medical_ultrasonographyhttp://en.wikipedia.org/wiki/Non-destructive_testinghttp://en.wikipedia.org/wiki/Magnetometer#Fluxgate_magnetometerhttp://en.wikipedia.org/wiki/Mariner_2http://en.wikipedia.org/wiki/Mariner_10http://en.wikipedia.org/wiki/Cassini-Huygenshttp://en.wikipedia.org/wiki/Magnetometer#Vector_heliumhttp://en.wikipedia.org/wiki/Magnetometer#Fluxgate_magnetometerhttp://en.wikipedia.org/wiki/Magnetic_field_sensors#cite_note-4http://en.wikipedia.org/wiki/MESSENGERhttp://en.wikipedia.org/wiki/GOEShttp://en.wikipedia.org/wiki/Magnitude_(mathematics)http://en.wikipedia.org/wiki/Direction_(geometry,_geography)http://en.wikipedia.org/wiki/Humidifierhttp://en.wikipedia.org/wiki/Sonarhttp://en.wikipedia.org/wiki/Medical_ultrasonographyhttp://en.wikipedia.org/wiki/Non-destructive_testing


34/59

Transducers

Fig. 4.6 Ultrasonic Transducer

An ultrasonic transducer is a device that converts energy into ultrasound, or sound

waves above the normal range of human hearing. While technically a dog whistle is an

ultrasonic transducer that converts mechanical energy in the form of air pressure into ultrasonic

sound waves, the term is more apt to be used to refer topiezoelectric transducers that convert

electrical energy into sound. Piezoelectric crystals have the property of changing size when a

voltage is applied, thus applying an alternating current (AC) across them causes them to

oscillate at very high frequencies, thus producing very high frequency sound waves.

The location at which a transducer focuses the sound can be determined by the active

transducer area and shape, the ultrasound frequency, and the sound velocity of the propagation

medium.

Detectors

Since piezoelectric crystals generate a voltage when force is applied to them, the same

crystal can be used as an ultrasonic detector. Some systems use separate transmitter and

receiver components while others combine both in a single piezoelectric transceiver.

Alternative methods for creating and detecting ultrasound include magnetostriction and

capacitive actuation.

34
http://en.wikipedia.org/wiki/Ultrasoundhttp://en.wikipedia.org/wiki/Dog_whistlehttp://en.wikipedia.org/wiki/Piezoelectricityhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Magnetostrictionhttp://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Actuatorhttp://en.wikipedia.org/wiki/Ultrasoundhttp://en.wikipedia.org/wiki/Dog_whistlehttp://en.wikipedia.org/wiki/Piezoelectricityhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Magnetostrictionhttp://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Actuator


35/59

4.5 RF TRANSMITTER AND RECEIVER

RF Transmitter STT-433MHz

Fig. 4.7 STT-433 MHZ Transmitter

About the transmitter

The STT-433 is ideal for remote control applications where low cost and longer rangeis required.

The transmitter operates from a1.5-12V supply, making it ideal for battery-powered

applications.

The transmitter employs a SAW-stabilized oscillator, ensuring accurate frequency

control for best range performance.

The manufacturing-friendly SIP style package and low-cost make the STT-433 suitable

for high volume applications.

Features

433.92 MHz Frequency

Low Cost

1.5-12V operation

35


36/59

Small size

Pin Description

Fig. 4.8 Pin diagram of STT-433MHz

GND

Transmitter ground. Connect to ground plane

DATA

Digital data input. This input is CMOS compatible and should be driven with CMOS level

inputs.

VCC

Operating voltage for the transmitter. VCC should be bypassed with a .01uF ceramic

capacitor and filtered with a 4.7uF tantalum capacitor. Noise on the power supply will degrade

transmitternoise performance.

ANTs

50 ohm antenna output. The antenna port impedance affects output power and harmonic

emissions. Antenna can be single core wire of approximately 17cm length or PCB trace

antenna

36


37/59

Application

Fig. 4.9 Basic Application circuit of STT-433MHz

The typical connection shown in the above figure cannot work exactly at all times

because there will be no proper synchronization between the transmitter and the

microcontroller unit. i.e., whatever the microcontroller sends the data to the transmitter, the

transmitter is not able to accept this data as this will be not in the radio frequency range. Thus,

we need an intermediate device which can accept the input from the microcontroller, process itin the range of radio frequency range and then send it to the transmitter. Thus, an encoder is

used.

RF Receiver STR-433 MHz

Fig. 4.10 RF Receiver STR-433MHz

37


38/59

The data is received by the RF receiver from the antenna pin and this data is available

on the data pins. Two Data pins are provided in the receiver module. Thus, this data can be

used for further applications.

Pin description

in ame Descript Fig. 4.11 Pin diagram of STR-433MHz

ANT

Antenna input.

GND

Receiver Ground. Connect to ground plane.

VCC (5V)

VCC pins are electrically connected and provide operating voltage for the receiver.

VCC can be applied to either or both. VCC should be bypassed with a .1F ceramic capacitor.

Noise on the power supply will degrade receiver sensitivity.

DATA

Digital data output.

This output is capable of driving one TTL or CMOS load. It is a CMOS compatible output.

38


39/59

Applications

Fig. 4.12 Basic Application circuit of STR-433MHz

Similarly, as the transmitter requires an encoder, the receiver module requires a decoder.

4.6 RF ENCODER AND DECODER

Encoder HT640

Fig. 4.13 Pin diagram of Encoder HT640

39


40/59

Pin Description

The Encoder Working

The 318 (3 power of 18) series of encoders begins a three-word transmission cycle

upon receipt of a transmission enable (TE for the HT600/HT640/HT680 or D12~D17 for the

HT6187/HT6207/HT6247, active high). This cycle will repeat itself as long as the transmission

enable (TE or D12~D17) is held high. Once the transmission enable falls low, the encoder

output completes its final cycle and then stops as shown below.

40


41/59

Basic Application Circuit Of HT640 Encoder

Fig. 4.14 Basic Application Circuit of HT640 Encoder

Transmission Circuit

41


42/59

Fig. 4.15 Basic Transmission Circuit

The data sent from the microcontroller is encoded and sent to RF transmitter. The data

is transmitted on the antenna pin. Thus, this data should be received on the destination i.e, on

RF receiver.

Decoder HT648L

Fig. 4.16 Decoder HT648L

Pin Description

42


43/59

Features

Operating voltage: 2.4V~12V.

Low power and high noise immunity CMOS technology.

Low standby current.

Capable of decoding 18 bits of information.

Pairs with HOLTEKs 318 series of encoders.

8~18 address pins.

0~8 data pins.

THE DECODER WORKING

The 3^18 decoders are a series of CMOS LSIs for remote control system applications.

They are paired with the 3^18 series of encoders.

For proper operation, a pair of encoder/decoder pair with the same number of address

and data format should be selected.

The 3^18 series of decoders receives serial address and data from that series of

encoders that are transmitted by a carrier using an RF medium.

A signal on the DIN pin then activates the oscillator which in turns decodes the

incoming address and data.

It then compares the serial input data twice continuously with its local address.

If no errors or unmatched codes are encountered, the input data codes are decoded and

then transferred to the output pins.

The VT pin also goes high to indicate a valid transmission. That will last until the

address code is incorrect or no signal has been received.

The 3^18 decoders are capable of decoding 18 bits of information that consists of N

bits of address and 18N bits of data.

43


44/59

Basic Application Circuit Of HT648L Decoder

Fig. 4.17 Basic Application Circuit of HT648L Decoder

Reception Circuit

Fig. 4.18 Basic Reception Circuit

44


45/59

The data transmitted into the air is received by the receiver. The received data is taken

from the data line of the receiver and is fed to the decoder .The output of decoder is given to

microcontroller and then data is processed according to the applications.

4.7 STEPPER MOTOR

Fig. 4.19 Stepper motor

A stepper motor is a widely used device that translates electrical pulses into mechanical

movement. The stepper motor is used for position control in applications such as disk drives,

dot matrix printers and robotics.

Stepper motors commonly have a permanent magnet rotor surrounded by a stator. The

most common stepper motors have four stator windings that are paired with a center-tapped

common. This type of stepper motor is commonly referred to as a four-phase or unipolar

stepper motor. The center tap allows a change of current direction in each of the two coils

when a winding is grounded, thereby resulting in a polarity change of the stator.

The direction of the rotation is dictated by the stator poles. The stator poles are determined by

the current sent through the wire coils. As the direction of the current is changed, the polarity is

also changed causing the reverse motion of the rotor.

45


46/59

It should be noted that while a conventional motor shaft runs freely, the stepper motor

shaft moves in a fixed repeatable increment, which allows one to move it to a precise position.

Thus, the stepper motor moves one step when the direction of current flow in the field coil(s)

changes, reversing the magnetic field of the stator poles. The difference between unipolar and

bipolar motors lies in the may that this reversal is achieved.

Fig. 4.20 Stepper motor operation

Advantages

1. The rotation angle of the motor is proportional to the input pulse.

2. The motor has full torque at standstill (if the windings are energized)

3. Precise positioning and repeatability of movement since good stepper motors have an

accuracy of 3 5% of a step and this error is non cumulative from one step to the next.

4. Excellent response to starting/ stopping/reversing.

5. Very reliable since there are no contact brushes in the motor. Therefore the life of the motor

is simply dependant on the life of the bearing.

6. The motors response to digital input pulses provides open-loop control, making the motor

simpler and less costly to control.

7. It is possible to achieve very low speed synchronous rotation with a load that is directly

coupled to the shaft.

46


47/59

8. A wide range of rotational speeds can be realized as the speed is proportional to the

frequency of the input pulses.

Disadvantages

1. Resonances can occur if not properly controlled.

2. Not easy to operate at extremely high speeds.

4.8 Buzzer

A buzzer or beeper is a signalling device, usually electronic, typically used in

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

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, and usually illuminatesa light on the appropriate button or control panel, and sounds a warning in the form of a

continuous or intermittent buzzing or beeping sound. Initially this device was based on an

electromechanical system which was identical to an electric bell without the metal gong

(which makes the ringing noise). Often these units were anchored to a wall or ceiling and used

the ceiling or wall as a sounding board.

Another implementation with some AC-connected devices was to implement a circuit

to make the AC current into a noise loud enough to drive a loudspeaker and hook this circuitup to a cheap 8-ohm speaker. Now-a-days, it is more popular to use a ceramic-based piezo-

electric sounder like a Sonalert which makes a high-pitched tone. Usually these were hooked

up to driver circuits which varied the pitch of the sound or pulsed the sound on and off

V C C

Q ?

B C 5

D ?

4 0 0 7

+

1 2 V

-

B u z

Fig. 4.21 Buzzer Circuit

47

C PORT


48/59

The circuit is designed to control the buzzer. The buzzer ON and OFF is

controlled by the pair of switching transistors (BC 547). The buzzer is connected in the Q2

transistor collector terminal. When high pulse signal is given to base of the Q1 transistors, the

transistor is conducting and close the collector and emitter terminal so zero signals is given to

base of the Q2 transistor. Hence Q2 transistor and buzzer is turned OFF state.

When low pulse is given to base of transistor Q1, the transistor is turned OFF.

Now 12V is given to base of Q2 transistor so the transistor is conducting and buzzer is

energized and produces the sound signal.

Applications

Annunciate panels

Electronic metronomes

Game shows

Microwave ovens and other household appliances

4.9 RELAY CIRCUIT

This is a regular general-purpose NPN type transistor. For control the 12V DCvoltage

electromechanical relay.BC547 is used in the relay circuit.This device is designed for use asgeneral purpose amplifiers and switches requiring collector currents to 300 mA. Sourced from

Process . Relay circuit acts as a switch in this purpiose .It also save the power .

48


49/59

Fig. 4.23 Relay Circuit

4.10MAX232 AND RS232

A line driver required to convert RS232 voltage levels to TTL levels, and vice versa. It

includes a capacitive voltage generator to supply TIA/EIA-232-F voltage levels from a single

5-V supply. Each receiver converts TIA/EIA-232-F inputs to 5-V TTL/CMOS levels. These

receivers have a typical threshold of 1.3 V, a typical hysteresis of 0.5 V, and can accept 30-V

inputs. Each driver converts TTL/CMOS input levels into TIA/EIA-232-F levels.

Pin Diagram

Fig. 4.24 MAX 232 pin configuration

49


50/59

Connection with Microcontroller and DB9

Fig. 4.25Connections with Microcontroller and DB9

8051 has two pins that are used specifically for transferring and receiving data serially. These

two pins are called TxD and RxD and are part of the port 3 group (P3.0 and P3.1).These pins

are TTL compatible; therefore, they require a line driver to make them RS232 compatible. To

allow data transfer between the PC and an 8051 system without any error, we must make sure

that the baud rate of 8051 system matches the baud rate of the PCs COM port.

How the RS-232 serial interface works

Most computers have one or two serial RS-232 interface as standard equipment.

Characteristics

An RS-232 interface has the following characteristics:

50


51/59

Uses a 9 pins connector "DB-9" (older PCs use 25 pins "DB-25").

Allows bidirectional full-duplex communication (the PC can send and receive data at

the same time).

Can communicate at a maximum speed of roughly 10KBytes/s.

DB-9 connector

You probably already saw this connector on the back of your PC.

Fig. 4.26 DB-9 connector

It has 9 pins, but the 3 important ones are:

pin 2: RxD (receive data).

pin 3: TxD (transmit data).

pin 5: GND (ground).

Using just 3 wires, you can send and receive data.

CHAPTER 5

SOFTWARE IMPLEMENTATION

5.1 FLOWCHART

51


52/59

Fig. 5.1 Flow chart for the Transmitter Section

52


53/59

Fig.5.2 Flow chart for the Receiver Section

5.2 code dumped in a micro controller

53


54/59

54


55/59

APPENDIX AIC7805

The specifications and absolute maximum ratings of IC7805 voltage regulator are

presented in this chapter.

A.1 Electrical Characteristics:

A.2 Maximum Ratings

55


56/59

APPENDIX B

Microcontroller(AT89S52)

The specifications and absolute maximum ratings of AT89S52 microcontroller are

presented in this chapter

B.1 DC Characteristics

56


57/59

B.2 Absolute Maximum Rating

B.3 AC Characteristics

57


58/59

REFERENCES

58


59/59

Books

The 8051 Microcontroller architecture, programming and applications -Kenneth

J.Ayala,second edition.

The 8051 Microcontroller and Embedded systems Muhammad Ali mazidi, Janice

Gillispoe mazidi,3rd edition.

C and the 8051 programing And MultitaskingSchultz.

URLs

www.atmel.com ATMEGA8952 Microcontroller

www.senet.com.au/~cpeacock RS 232

www.maxim-ic.com Max 220-249

www.mysunrise.ch/users/pfleury/avr-circuits.html LCD
http://www.atmel.com/http://www.senet.com.au/~cpeacockhttp://www.senet.com.au/~cpeacockhttp://www.maxim-ic.com/http://www.maxim-ic.com/http://www.mysunrise.ch/users/pfleury/avr-circuits.htmlhttp://www.atmel.com/http://www.senet.com.au/~cpeacockhttp://www.maxim-ic.com/http://www.mysunrise.ch/users/pfleury/avr-circuits.html

Documents

Main Project Repor