1

CHAPTER 1

INTRODUCTION

There is one death every four minutes due to a road accident in

India.16 children die on Indian roads daily. One serious road accident in the

country occurs every minute and 16 die on Indian roads every hour. Tamil

Nadu is the state with the maximum number of road crash injuries. This project

“ADAPTIVE ZONE PREDICTION SYSTEM” aims to reduce this statistics by

providing a safe environment for pedestrians especially in major zones such as

schools, hospitals and highways. The project consists of two units: The wireless

location informer and the vehicle unit. The former unit is present within the

zone whereas the latter unit is present inside the vehicle. These two units

communicate using RF communication. Here, the speed of the vehicle is

controlled in school zones, the horn intensity level is controlled in hospital

zones and the headlight is controlled in highway zones. We employ the use of

PIC16F887 microcontroller, RF Transmitter and Receiver modules and

individual control units for each zone.

2

CHAPTER 2

PROJECT OVERVIEW

2.1 BLOCK DIAGRAM

Fig 2.1.1 Block Diagram of Wireless Location Informer

3

Fig 2.1.2 Block Diagram of Vehicle Unit

2.2 WORKING

Each zone consists of a transmitter unit. The data regarding that zone

(school zone, hospital zone or highway zone) is encoded using HT12E encoder

and transmitted through a 433MHz RF Transmitter.

The data is received by the 433MHz RF Receiver present in the vehicle

unit and is decoded using a HT12D decoder. The decoded data is passed

through a buffer and then sent to the PIC16F887 microcontroller. The controller

then processes these inputs and sends control inputs to the corresponding

circuits. On entering the school zone, the speed of the vehicle is controlled. In

hospital zone the horn intensity level of the vehicle is controlled and in highway

zone the headlight intensity of the vehicle is controlled. The LCD display

present on the dashboard of the vehicle displays the details of the zone.

4

CHAPTER 3

POWER SUPPLY

3.1 INTRODUCTION

A power supply is a device that supplies electrical energy to one or more

electric loads. The term is most commonly applied to devices that convert one

form of electrical energy to another.

A regulated power supply is one that controls the output voltage or

current to a specific value, the controlled value is held nearly constant despite

variations in either load current or the voltage supplied by the power supplies

energy source.

Every power supply obtains the energy it supplies to its load, as well as

any energy it consumes while performing that task, from an energy source.

A power supply may be implemented as a discrete, stand-alone device or

as an integral device that is hardwired to its load. In the latter case, for example

low voltage DC power supplies are commonly integrated with their loads in

devices such as computers and household electronics.

Fig 3.1.1 Block Diagram of Power Supply

5

3.2 WORKING PRINCIPLE

The ac voltage, typically 220V rms, is connected to a transformer, which

steps that ac voltage down to the level of the desired dc output. A diode rectifier

then provides a full-wave rectified voltage that is initially filtered by a simple

capacitor filter to produce a dc voltage. This resulting dc voltage usually has

some ripple or ac voltage variation.

A regulator circuit removes the ripples and also remains the same dc

value even if the input dc voltage varies, or the load connected to the output dc

voltage changes. This voltage regulation is usually obtained using one of the

popular voltage regulator IC units.

6

CHAPTER 4

TRANSMITTER

4.1 INTRODUCTION

A transmitter or radio transmitter is an electronic device which, with the

aid of an antenna, produces radio waves. The transmitter itself generates a radio

frequency alternating current, which is applied to the antenna. When excited by

this alternating current, the antenna radiates radio waves. In addition to their use

in broadcasting, transmitters are necessary component parts of many electronic

devices that communicate by radio, such as cell phones, wireless computer

networks, Bluetooth enabled devices, garage door openers, two-way radios in

aircraft, ships, spacecraft, radar sets and navigational beacons. The term

transmitter is usually limited to equipment that generates radio waves

for communication purposes, or radiolocation, such as radar and navigational

transmitters. Generators of radio waves for heating or industrial purposes, such

as microwave ovens or diathermy equipment, are not usually called transmitters

even though they often have similar circuits.

The term is popularly used more specifically to refer to a broadcast

transmitter, a transmitter used in broadcasting, as in FM radio

transmitter or television transmitter. This usage typically includes the

transmitter, the antenna, and often the building it is housed in.

The RF module, as the name suggests, operates at Radio Frequency. The

corresponding frequency range varies between 30 kHz & 300 GHz. In this RF

system, the digital data is represented as variations in the amplitude of carrier

wave. This kind of modulation is known as Amplitude Shift Keying (ASK).

7

Radio Frequency transmission is more strong and reliable than Infrared

transmission because of the following reasons:

Radio Frequency signals can travel longer distances than Infrared.

Only line of sight communication is possible through Infrared while

radio frequency signals can be transmitted even when there are

obstacles.

Infrared signals will get interfered by other IR sources but signals on

one frequency band in RF will not interfered by other frequency RF

signals.

4.2 RF TRANSMITTER

An RF transmitter module is a small PCB sub-assembly capable of

transmitting a radio wave and modulating that wave to carry data. Transmitter

modules are usually implemented alongside a micro controller which will

provide data to the module which can be transmitted. RF transmitters are

usually subject to regulatory requirements which dictate the maximum

allowable transmitter power output, harmonics, and band edge requirements.

The transmitter operates at a frequency of 434MHz. An RF transmitter

receives serial data and transmits it wirelessly. The transmission occurs at the

rate of 1Kbps - 10Kbps.The transmitted data is received by an RF receiver

operating at the same frequency as that of the transmitter.

8

Fig 4.2.1 Pin Diagram of RF Transmitter

4.2.1 PIN DESCRIPTION

Pin

No Function Name

1 Ground (0V) Ground

2 Serial data input pin Data

3 Supply voltage; 5V Vcc

4 Antenna output pin ANT

Table 4.2.1 Pin Description

9

4.2.2 ELECTRICAL CHARACTERISTICS

T=25oC, Vcc=3.6V, Frequency=433.92MHZ

Characteristic Min. Typ. Max. Unit

Operating Frequency (200Khz) - 433.92 - MHZ

Data Rate - - 100 Kbps

Peak Input Current, 12 Vdc Supply - 45 - mA

Peak Output Power - 10 - mW

Turn on / Turn Off Time - - 1 µs

Operating Ambient Temperature -20 - +85 oC

Table 4.2.2 Electrical Characteristics

4.3 ENCODER

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

(AD0-AD3) 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.

10

4.3.1 FEATURES

• 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

Fig 4.3.1 Circuit Diagram of Encoder

11

4.3.2 PIN DESCRIPTION

Fig 4.3.2 Pin Diagram of HT12E Encoder

VCC: Positive power supply pin.

OSC1 and OSC2: Input and output pin of the oscillator respectively.

TE: Used for enabling the transmission; a low signal in this pin will enable

the transmission of data bits.

A0 – A7: Input address pins used for secured transmission. These pins can be

connected to GND for low signal or left open for high state.

AD0 – AD3: Used for feeding data into the IC. These pins may be connected

to GND for sending LOW since it is an active low pin

OUTPUT: Output pin of the encoder

12

4.3.3 ELECTRICAL CHARACTERISTICS

Ta=250C

Symbol Parameter Test Conditions Min Typ Max Unit

VDD Conditions

VDD Operating

Voltage - - 2.4 5 12 V

ISTB

Standby Current 3V Oscillator

stops

- 0.1 1 µA

12V - 2 4 µA

IDD

Operating Current 3V No load

fOSC= 3kHz

- 40 80 µA

12V - 150 300 µA

IDOUT

Output Drive

Current 5V

VOH=0.9VDD

(Source) -1 -1.6 - mA

VOL=0.1VDD

(Sink) 1 1.6 - mA

VIH “H” Input

Voltage - - 0.8VDD - VDD V

VIL “L” Input Voltage - - 0 - 0.2VDD V

fOSC Oscillator

frequency 5V ROSC=1.1MΩ - 3 - kHz

RTE TE pull high

resistance 5V VTE=0V - 1.5 3 MΩ

Table 4.3.1 Electrical Characteristic of HT12E

13

4.3.4 WORKING OF HT12E IC

Fig 4.3.3 Transmission Timing Diagram of HT12E

HT12E starts working with a low signal on the TE pin. After receiving a

low signal the HT12E starts the transmission of 4 data bits as shown in the

timing diagram above. And the output cycle will repeats based on the status of

the TE pin in the IC. If the TE pin retains the low signal the cycle repeats as

long as the low signal in the TE pin exists. The encoder IC will be in standby

mode if the TE pin is disabled and thus the status of this pin was necessary for

encoding process. The address of these bits can be set through A0 – A7 and the

same scheme should be used in decoders to retrieve the signal bits.

14

4.3.4.1 ENCODER OPERATION FLOW CHART

The encoder operation can be represented by a flowchart as shown in Fig 4.3.4

Fig 4.3.4 Encoder Operation Flow Chart

15

Fig 4.3.5 Circuit Diagram

HT12E Encoder IC will convert the 4 bit parallel data given to pins D0 –

D3 to serial data and will be available at DOUT. This output serial data is given

to ASK RF Transmitter. Address inputs A0 – A7 can be used to provide data

security and can be connected to GND (Logic ZERO) or left open (Logic ONE).

Status of these Address pins should match with status of address pins in the

receiver for the transmission of the data. Data will be transmitted only when the

Transmit Enable pin (TE) is LOW. 1.1MΩ resistor will provide the necessary

external resistance for the operation of the internal oscillator of HT12E.

16

CHAPTER 5

RECEIVER

5.1 INTRODUCTION

In radio communications, a radio receiver is an electronic device that

receives radio waves and converts the information carried by them to a usable

form. It is used with an antenna. The antenna intercepts radio waves

(electromagnetic waves) and converts them to tiny alternating currents which

are applied to the receiver, and the receiver extracts the desired information.

The receiver uses electronic filters to separate the desired radio frequency signal

from all the other signals picked up by the antenna, an electronic amplifier to

increase the power of the signal for further processing, and finally recovers the

desired information through demodulation.

The information produced by the receiver may be in the form of sound

(an audio signal), images (a video signal) or data (a digital signal). A radio

receiver may be a separate piece of electronic equipment, or an electronic

circuit within another device. Devices that contain radio receivers

include television sets, radar equipment, two-way radios, cell phones, wireless

computer networks, GPS navigation devices, satellite dishes, radio

telescopes, Bluetooth enabled devices, garage door openers, and baby monitors.

17

5.2 RF RECEIVER:

An RF receiver module receives the modulated RF signal,

and demodulates it. There are two types of RF receiver modules: super

heterodyne receivers and super-regenerative receivers. Super-regenerative

modules are usually low cost and low power designs using a series of amplifiers

to extract modulated data from a carrier wave. Super-regenerative modules are

generally imprecise as their frequency of operation varies considerably with

temperature and power supply voltage. Super heterodyne receivers have a

performance advantage over super-regenerative; they offer increased accuracy

and stability over a large voltage and temperature range. This stability comes

from a fixed crystal design which in turn leads to a comparatively more

expensive product.

This is a PLL based ASK Hybrid 433Mhz RF receiver module and is

ideal for short-range wireless control applications where quality is a primary

concern. The receiver module requires no external RF components except for

the antenna. The super-regenerative design exhibits exceptional sensitivity at a

very low cost.

Fig 5.2.1 Pin Diagram of RF Receiver

18

5.2.1 PIN DESCRIPTION

Pin

No Function Name

1 Ground (0V) Ground

2 Serial data output pin Data

3 Linear output pin; not connected NC

4 Supply voltage; 5V Vcc

5 Supply voltage; 5V Vcc

6 Ground (0V) Ground

7 Ground (0V) Ground

8 Antenna input pin ANT

Table 5.2.1 Pin Description of RF 433 MHz Receiver

19

5.2.2 ELECTRICAL CHARACTERISTICS

Characteristic Symbol Min. Typ. Max. Unit

Reception Bandwidth BWrx - 1.0 - MHZ

Centre Frequency Fc - 433.92 - MHZ

Sensitivity - - -105

dBm

Operating current Icc - 3.5 4.5 mA

Peak Output Power Po - 10 - mW

Turn on Time Ton - 25 - us

Operating Voltage Vcc 4.5 5.0 5.5 Vdc

Operating Ambient Temperature Top -10 - +60 °C

Max Data Rate - 300 1k 3k Kbit/s

Table 5.2.2 Electrical Characteristic of RF Receiver

5.3 DECODER

HT12D is a decoder integrated circuit that belongs to 212

series of

decoders. This series of decoders are mainly used for remote control system

applications, like burglar alarm, car door controller, security system etc. It is

mainly provided to interface RF and infrared circuits. They are paired with

212

series of encoders.

20

HT12D converts the serial input into parallel outputs. It decodes the serial

addresses and data received by, say, an RF receiver, into parallel data and sends

them to output data pins. The serial input data is compared with the local

addresses three times continuously. The input data code is decoded when no

error or unmatched codes are found. A valid transmission in indicated by a high

signal at VT pin.

HT12D is capable of decoding 12 bits, of which 8 are address bits and 4

are data bits. The data on 4 bit latch type output pins remain unchanged until

new is received.

5.3.1 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

Fig 5.3.1 Circuit Diagram of HT12D Decoder

21

5.3.2 PIN DESCRIPTION:

Fig 5.3.2 Pin Diagram of HT12D Decoder

VCC and GND are used to provide power to the IC, Positive and

Negative of the power supply respectively.

Osc1 and Osc2:OSC1 is the oscillator input pin and OSC2 is the

oscillator output pin.

A0 – A7 are the address input pins. These pins can be connected to VSS

or left open.

INPUT is the serial data input pin.

D8 – D11 are the data output pins.

VT stands for Valid Transmission. This output pin will be HIGH when

valid data is available at D8 – D11 data output pins.

22

5.3.3 ELECTRICAL CHARACTERISTICS

Ta=250C

Symbol Parameter Test Conditions Min Typ Max Unit

VDD Conditions

VDD Operating Voltage - - 2.4 5 12 V

ISTB

Standby Current 5V Oscillator

stops

- 0.1 1 µA

12V - 2 4 µA

IDD

Operating Current 5V

No load

fOSC=150kHz - 200 400 µA

IO Data Output

Source Current 5V VOH=4.5V -1 -1.6 - mA

Data Output Sink

Current 5V VOL=0.5V 1 1.6 - mA

IVT VT Output Source

Current 5V

VOH=4.5V -1 -1.6 - mA

VT Output Sink

Current VOL=0.5V 1 1.6 - mA

VIH “H” Input Voltage 5V - 3.5 - 5 V

VIL “L” Input Voltage 5V - 0 - 1 V

fOSC Oscillator

frequency 5V ROSC=51 kΩ - 150 - kHz

Table 5.3.1 Electrical Characteristics of HT12D Decoder

23

5.3.4 WORKING

Fig 5.3.3 Timing Diagram of HT12D Decoder

HT12D decoder will be in standby mode initially i.e., oscillator is

disabled and a HIGH on DIN pin activates the oscillator. Thus the oscillator will

be active when the decoder receives data transmitted by an encoder. The device

starts decoding the input address and data. The decoder matches the received

address three times continuously with the local address given to pin A0 – A7. If

all matches, data bits are decoded and output pins D8 – D11 are activated. This

valid data is indicated by making the pin VT (Valid Transmission) HIGH. This

will continue till the address code becomes incorrect or no signal is received.

24

5.3.4.1 FLOW CHART

Fig 5.3.4 Operational Flow Chart of HT12D Decoder

25

5.3.4.2 CIRCUIT DIAGRAM:

Fig 5.3.5 Circuit Diagram of RF 433 MHz Receiver

ASK RF Receiver receives the data transmitted using ASK RF

Transmitter. HT12D decoder will convert the received serial data to 4 bit

parallel data D0 – D3. The status of these address pins A0-A7 should match

with status of address pin in the HT12E at the transmitter for the transmission of

data. The LED connected to the above circuit glows when valid data

transmission occurs from transmitter to receiver. 51KΩ resistor will provide the

necessary resistance required for the internal oscillator of the HT12D.

26

CHAPTER 6

LCD DISPLAY

6.1 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. Liquid

crystal cell displays (LCDs) are used in similar applications where LEDs are

used. These applications are to display of numeric and alphanumeric characters

in dot matrix and segmental displays.

A 16x2 LCD means it can display 16 characters per line and there

are two such lines. In this LCD each character is displayed in 5x7 pixel matrix.

This LCD has 2 registers namely command and data. The command register

stores the command instructions given to the LCD. A command is an instruction

given to LCD to do a predefined task like initializing it, clearing its screen,

setting the cursor position, controlling the display, etc. The data register stores

the data to be displayed in the LCD. The data is the ASCII value of the

character to be displayed.

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

sandwiched 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.

27

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 polarizers 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.

Fig 6.1.1 Pin Description of 16x2 LCD Display

28

6.2 WORKING

When sufficient voltage is applied to the electrodes the liquid crystal

molecules will 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.

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.

The pixels are addressed one at a time by row and column

addresses. Each pixel has its own dedicated transistor, all of 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.

29

Fig 6.2.1 Internal Block Diagram of 16x2 LCD Display

30

CHAPTER 7

PIC16F887

7.1 INTRODUCTION

PIC is a family of Harvard architecture microcontrollers made by

Microchip Technology, developed by General Instrument's Microelectronics

Division. The name PIC initially refers to "Peripheral Interface Controller".

PICs are popular with developers due to their low cost, wide availability, large

user base, extensive collection of application notes, availability of low cost or

free development tools, and serial programming (and re-programming with

flash memory) capability.

The microcontroller used in our project is PIC16F887.It is a 40 pin flash-

based, 8-bit CMOS microcontroller with nanoWatt Technology.

It is a high performance RISC CPU with the following specifications:

• Only 35 instructions to learn:

- All single-cycle instructions except branches

• Operating speed:

- DC – 20 MHz oscillator/clock input

- DC – 200 ns instruction cycle

• Interrupt capability

• 8-level deep hardware stack

• Direct, Indirect and Relative Addressing modes

31

7.2 FEATURES OF PIC16F887

7.2.1 SPECIAL MICROCONTROLLER FEATURES

• Precision Internal Oscillator:

- Factory calibrated to ±1%

- Software selectable frequency range of 31 kHz to 8 MHz

- Two-Speed Start-up mode

- Crystal fail detect for critical applications

- Clock mode switching during operation for power savings

• Power-Saving Sleep mode

• Wide operating voltage range (2.0V-5.5V)

• Industrial and Extended Temperature range

• Power-on Reset (POR)

• Power-up Timer (PWRT) and Oscillator Start-up Timer (OST)

• Brown-out Reset (BOR) with software control option

• Enhanced low-current Watchdog Timer (WDT) with on-chip oscillator

• Multiplexed Master Clear with pull-up/input pin

• Programmable code protection

• High Endurance Flash/EEPROM cell:

- 100,000 write Flash endurance

- 1,000,000 write EEPROM endurance

32

- Flash/Data EEPROM retention: > 40 years

• Program memory Read/Write during run time

• In-Circuit Debugger (on board)

7.2.2 LOW POWER FEATURES

• Standby Current: - 50 nA @ 2.0V, typical

• Operating Current: - 11 μA @ 32 kHz, 2.0V, typical - 220 μA @ 4 MHz,

2.0V, typical

• Watchdog Timer Current: -1 μA @ 2.0V, typical

7.2.3 PERIPHERAL FEATURES

• 35 I/O pins with individual direction control:

- High current source/sink for direct LED drive

- Interrupt on change pin

- Ultra Low-Power Wake-up (ULPWU)

• Analog Comparator module with:

- Two analog comparators

- Programmable on-chip voltage reference (CVREF) module

- Fixed voltage reference (0.6V)

- Comparator inputs and outputs externally accessible

- External Timer1 Gate (count enable)

• A/D Converter:

- 10-bit resolution and 14 channels

33

• Timer0:

- 8-bit timer/counter with 8-bit programmable prescalar

• Enhanced Timer1:

- 16-bit timer/counter with prescalar

- External Gate Input mode

• Timer2:

- 8-bit timer/counter with 8-bit period register, prescalar and postscalar

• Enhanced Capture, Compare, PWM+ module:

- 16-bit Capture, max. resolution 12.5 ns

- Compare, max. resolution 200 ns

- 10-bit PWM with 1 output channel

- PWM output steering control

•Capture, Compare, PWM module:

- 16-bit Capture, max. resolution 12.5 ns

- 16-bit Compare, max. resolution 200 ns

- 10-bit PWM, max. frequency 20 kHz

• Enhanced USART module

• In-Circuit Serial Programming (ICSP) via two pins

• Master Synchronous Serial Port (MSSP) module supporting 3-wire SPI (all 4

modes) and I2C Master and Slave Modes with I2C address mask

34

7.3 PIN CONNECTIONS

Fig 7.3.1 Pin Diagram of PIC16F887

Pin No. 1 : Vpp (+5V)

Pin No. 2 : Connected to potentiometer (For speed adjustment)

Pin No. 3 - 10 : No connection

Pin No. 11 : Vdd(+5V)

Pin No. 12 : Gnd

Pin No. 13 – 14 : Connected to 4 MHz oscillator

Pin No. 15 : Connected to horn control circuit

Pin No. 16 : Connected to headlight control circuit

35

Pin No. 17 : Connected to speed control circuit

Pin No. 18 : No connection

Pin No. 19 - 22 : D port connected to a decoder module

Pin No. 23 - 30 : No connection

Pin No. 31 : Gnd

Pin No. 32 : Vdd(+5V)

Pin No. 33 - 40 : B Port connected to LCD

7.4 PORT DESCRIPTION

Port A : Pins 2 to 7 , 13, 14

Port B : Pins 33 to 40

Port C : Pins 15 to 18 and 23 to 26

Port D : Pins 19 to 22 and 27 to 30

Port E : Pins 8 to 10

36

7.5 MEMORY ORGANIZATION

7.5.1 PROGRAM MEMORY ORGANIZATION

PIC16F887 has a 13-bit program counter capable of addressing a 8K x14

(0000h-1FFFh) program memory space. Accessing a location above these

boundaries will cause a wraparound within the first 8Kx14 space. The Reset

vector is at 0000h and the interrupt vector is at 0004h.

7.5.2 DATA MEMORY ORGANIZATION

The data memory is partitioned into four banks which contain the General

Purpose Registers (GPR) and the Special Function Registers (SFR). The Special

Function Registers are located in the first 32 locations of each bank. The

General Purpose Registers, implemented as static RAM, are located in the last

96 locations of each Bank. The actual number of General Purpose Resisters

(GPR) implemented in each Bank depends on the device. All other RAM is

unimplemented and returns ‘0’ when read. RP<1:0> of the STATUS register are

the bank select bits:

RP1 RP0

0 0 → Bank 0 is selected

0 1 → Bank 1 is selected

1 0 → Bank 2 is selected

1 1 → Bank 3 is selected

7.5.2.1 GENERAL PURPOSE REGISTER

The register file is organized as 368 x 8 in the PIC16F886/PIC16F887.

Each register is accessed, either directly or indirectly, through the File Select

Register (FSR).

37

7.5.2.2 SPECIAL FUNCTION REGISTERS

The Special Function Registers are used by the CPU and peripheral functions

for controlling the desired operation of the device. These registers are static

RAM. The special registers can be classified into two sets as

1. Core

2. Peripheral.

7.6 MPLAB IDE

7.6.1 INTRODUCTION

Integrated Development Environment (IDE) is an application that has

multiple functions for software development. MPLAB IDE is an executable

program that integrates a complier, an assembler, a project manager, an editor, a

debugger, simulator and an assortment of other tools within one windows

application. A user developing an application should be able to write code,

compile, debug and test the application without leaving the MPLAB IDE

desktop.

7.6.2 FEATURES

MPLAB IDE is a Windows Operating System (OS) based Integrated

Development Environment for the PIC MCU families. The MPLAB IDE

provides the ability to:

Create and edit source code using the built-in editor.

Assemble, compile and link source code.

38

Debug the executable logic by watching program flow with the

built-in simulator or in real time with in-circuit emulators or in-

circuit debuggers.

Make timing measurements with the simulator or emulator.

View variables in Watch windows.

Program firmware into devices with device programmers.

7.6.3 DESIGN CYCLE

The design cycle for developing an embedded controller application is:

1) Do the high level design – From the features and performance desired,

decide which PIC device you need, then design the associated hardware

circuitry.

2) Knowing which peripherals and pins control your hardware, write the

software. Use either assembly language, which is directly translatable into

machine code, or using a compiler that allows a more natural language for

creating programs. With these Language Tools you can write and edit code that

is more or less understandable, with constructs that help you organize your

code.

3) Compile or assemble the software using a Language Tool to convert your

code into machine code for the PIC device.

4) Test your code. Usually a complex program does not work exactly the way

you might have imagined, and “bugs” need to be removed from your design to

get it to act properly.

5) “Burn” your code into a microcontroller and verify that it executes correctly

in your finished application.

39

7.7 EMBEDDED C

7.7.1 INTRODUCTION

Embedded C is a set of language extensions for the IC programming

language by the C standards committee to address common issues that exist

between C extensions for different embedded systems. Historically, embedded

C programming requires nonstandard extensions to the C language in order to

support exotic features such as fixed-point arithmetic, multiple distinct memory

banks and basic I/O operations. In 2008, the C standards Committee extended

the C language to address these issues by providing a common standard for all

implementations to adhere to. It includes a number of features not available in

normal C such as fixed-point arithmetic, names address spaces and basic I/O

hardware addressing.

Embedded C uses most of the syntax and semantics of standard C. e.g.,

main() function , variable definition, data type declaration, conditional

statements(if, else, case), loops( while, for), functions, arrays and strings,

structures and union, bit operations, macros, etc.

7.7.2 ADVANTAGES

It is small and simpler to learn, understand, program and debug.

Compared to assembly language, C code written is more reliable and

scalable, more portable between different platforms.

C compliers are available for almost all embedded devices.

Unlike assembly language, C has advantage of process or independence

and is not specific to any particular microprocessor/microcontroller or

any system. This makes it convenient for a user to develop programs that

can run on most of the systems.

40

As C combines functionality of assembly language and features of high

level languages, C is treated as a 'middle-level computer language' or

'high level assembly language'.

It is fairly efficient.

It supports access to I/O and provides ease of management for large

embedded projects.

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CHAPTER 8

CONTROL UNITS

8.1 SPEED CONTROL

When the vehicle enters the school zone, the speed of the vehicle should

be adjusted so as to avoid accidents. This function is implemented using the

speed control module.

An RF transmitter present in the school zone sends the digital data

allocated for that zone (in this case, school zone corresponds to the data 1110)

in the form of serial data using a HT12E encoder explained in chapter-4. By RF

transmission, the RF receiver collects the data and decodes the serial data back

to parallel data which is sent to the PIC16F887 microcontroller for processing.

The PIC microcontroller is programmed in embedded C using MPLAB IDE

software.

Here, the speed is manually altered using a potentiometer. According to

the signal from this POT, the PIC is programmed to generate a Pulse Width

Modulated (PWM) signal with the voltage reduced to its preset threshold value

when the vehicle unit enters the school zone. This PWM signal is given to a DC

motor through a driver circuit as shown in Fig.8.1.1

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Fig.8.1.1 Circuit Diagram of Speed Control Unit

The circuit consists of a Darlington transistor pair to adjust the gain to the

required level and the speed change is shown using a DC motor. Thus, when the

vehicle unit is present in the school zone, its speed cannot be increased beyond

a preset value.

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8.2HORN CONTROL

When the vehicle enters the hospital zone, the horn intensity of the

vehicle is to be adjusted. This function is implemented using the horn control

module.

An RF transmitter present in the hospital zone sends the digital data

allocated for that zone (in this case, hospital zone corresponds to the data 1101)

in the form of serial data using a HT12E encoder explained in chapter-4. By RF

transmission, the RF receiver collects the data and decodes the serial data back

to parallel data which is sent to the PIC16F887 microcontroller for processing.

The PIC microcontroller is programmed in embedded C using MPLAB IDE

software.

Here, the horn is manually switched using a push button switch.

According to the signal from this switch, the PIC is programmed to generate an

analog signal with the voltage reduced to its preset threshold value when the

vehicle unit enters the hospital zone and thereby reducing the intensity of the

horn through a driver circuit as shown in Fig.8.2.1

Fig 8.2.1 Circuit Diagram of Horn control Unit

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It consists of a Darlington transistor pair to adjust the gain levels and a

relay, which acts a switch between high (+12V) and low (+5V) levels. Here, a

buzzer is used to play the role of a horn of the vehicle.

8.2.1 RELAY

A relay is an electrically operated switch. Current flowing through the

coil of the relay creates a magnetic field which attracts a lever and changes the

switch contacts. The coil current can be on or off so relays have two switch

positions and most have double throw (changeover) switch contacts.

Relays allow one circuit to switch a second circuit which can be

completely separate from the first. For example a low voltage battery circuit can

use a relay to switch a 230V AC mains circuit. There is no electrical connection

inside the relay between the two circuits; the link is magnetic and mechanical.

Fig 8.2.2 Relay

Relays are usually SPDT or DPDT but they can have many more sets of

switch contacts. The relay's switch connections are labeled COM, NC and NO:

COM = Common, always connected to this, it is the moving part of the switch.

NC = Normally Closed, COM is connected to this when the relay coil is off.

NO = Normally Open, COM is connected to this when the relay coil is on.

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Fig 8.2.3 Pin Description of Relay

8.2.2 HORN (Buzzer)

A buzzer or beeper is a signaling device, usually electronic, typically

used in automobiles, household appliances such as a microwave oven, or game

shows.

Fig 8.2.4 Buzzer

It uses a ceramic-based piezoelectric sounder which makes a high-pitched

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

Usually these are hooked up to "driver" circuits which vary the pitch of the

sound or pulse the sound on and off.

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8.3 HEADLIGHT CONTROL

While driving the vehicle in the highway with high beam headlights can

increase the driver’s visibility, it can prove to be a blinding hazard for other

drivers. Thus, it is essential to control the vehicle’s headlight.

An RF transmitter present in the highway sends the digital data allocated

for that zone (in this case, highway zone corresponds to the data 1011) in the

form of serial data using a HT12E encoder explained in chapter-4. By RF

transmission, the RF receiver collects the data and decodes the serial data back

to parallel data which is sent to the PIC16F887 microcontroller for processing.

The PIC microcontroller is programmed in embedded C using MPLAB IDE

software.

Here, the headlight is manually altered using a SPDT switch. According

to the signal from this switch, the PIC is programmed to generate a Pulse Width

Modulated (PWM) signal with the voltage reduced to its preset threshold value

when the vehicle unit enters the highway. This PWM signal is given to the

vehicle’s headlights through a driver circuit as shown in Fig.8.3.1. This is used

to provide automatic switching between high and low beam headlights.

Fig 8.3.1 Circuit Diagram of Headlight Control Unit

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The circuit consists of a Darlington transistor pair to adjust the gain to the

required level. Here, a bulb or a flashlight maybe used in place of the vehicle

headlights. Thus, the automatic headlight control can perform a great deal in

reducing the manual efforts and fatigue of drivers in dipping the headlight while

driving through the highway and thus provide safe driving without blinding the

other drivers.

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CHAPTER 9

CONCLUSION

In this project, we have demonstrated a possible method that can be

implemented in order to reduce the accidents in the country. Also it reduces the

discomfort experienced by the people in hospitals due to continuous honking.

This method controls the head light intensity which is a major cause of

accidents in highways. The automatic head light intensity control can perform a

great deal in reducing the manual efforts and fatigue of drivers in dipping the

head light while driving through the highway and thus provides a safe driving

without blinding the other drivers. This project can be implemented in heavily

populated areas. The receiver has to be fitted in each vehicle which will reduce

the risk of collisions and its penalties. When implemented using antennas, it can

cover a wider range. This project can be implemented in automobiles using

cruise control systems.

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REFERENCES

[1] Ankita Mishra, Harshala Bakshi, Jyoti Solanki, Pranav Paranjpe, Priyanka

Saxena (2012), ‘Design of RF based speed control system for vehicles’,

International Journal of Advanced Research in Computer and Communication

Engineering, Vol. 1, Issue 8.

[2] Abdul Rahim Makandar, Deepa B Chavan, Faizal Hakeem Khan, Syed

Azimuddin Inamdar (2014), ‘Automatic Vehicle Speed Reduction System using

RF technology’, International Journal of Engineering Research and

Applications, Vol. 4, Issue 4, pp. 13-16.

[3] Atul Kumar Dewangan, Nibbedita Chakraborty, Sashi Shukla, Vinod Yadu

(2012), ‘PWM Based Automatic Closed Loop Speed Control of DC Motor’,

International Journal of Engineering Trends and Technology, Volume3, Issue 2.

[4] Larry O'Cull, Richard H. Barnett, Sarah Alison Cox, “Embedded C

Programming and the Microchip PIC”, Volume 1.

[5] Mark Siegesmund, “Embedded C Programming: Techniques and

Applications of C and PIC MCUS”.

[6] Danny Causey, Muhammad Ali Mazidi and Rolin D. Mckinlay, “Pic

Microcontrollers and Embedded Systems”.

[7] Milan Verle, “Pic Microcontrollers-Programming in C”

[8] Han Way Huang and Leo Chartrand, “PIC Microcontroller: An Introduction

to Software & Hardware Interfacing”.