train alarm system by microchip design project
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INTRODUCTION:
Sometimes we people comes to know
accident of trains from news papers.
Whatever may be the cause there is great
loss of life and wealth. Lot of damage done torailway track and prevents other trains to
move on it. Trains are accident in remote
areas so it prevents people from quick
treatment, this leads to more loss of life.
Accident occurs due to derailing of trains due
to cracks develops in tracks & subversive
activities by terrorist. Accidents happen due
to collision between two trains. These
collisions are head on or from backside.
Accident due to collision is serious one which
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causes lot of loss in lives and wealth. This is
mainly due to human error.
Bad management & human error cause
accident between two trains. A train is in one
track & by mistake another train is released in
that track. This leads to head on or back side
collision.
Here we try to develop a system that helps in
alarming both trains and stopping one train
before being collided. It is a microcontroller
based system and wireless operated system.
Wireless because it sends signals to trains
about track information and alarm. Here we
use two eight bit microcontroller of 18 pin
(PIC 16F628) from microchip. The project also
use IR light beam for the purpose.
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BLOCK DIAGRAM:
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IR transmitter:
This section is usually fitted with a constant
voltage supply +5v which are constantlygiving the signal to the IR LED. So IRtransmitting LED will emit lights. The infraredtransmitter is to be faced at the matchinginfrared sensor mounted on the other side ofthe train track. Infrared signal follows all thetheories of light and do not make disturbance
in passage as it is not visible.
IR receiver:
It is the circuit, which contains IR sensors
which receives IR signal radiating out of the IR
LED. It converts it into electric signal. The
signal received and fed to microcontroller at
within specified voltage level.
Comparator:
It compares sensor output with a referencevoltage. So that it provides perfect digital
output. Two sensors have two OPAMP output.
Serial encoder:It encodes the parallel input signal from themicrocontroller to serial data.
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Radio transmitter:It is a frequency modulated ASK transmitter.
The digital data generated is super imposedupon the carrier frequency by ASK techniqueand is transmitted to air at 433 MHz.
Radio Receiver:It is the circuit, ASK receiver, which receives
the transmitted signal and separates the
encoded digital data from the carrier wave.
Serial decoder:It converts the serial data into parallel four
bit binary data.
Microcontroller section:This section takes the input of sensors andgenerates logic accordingly. This binary datais send to serial encoder.
Driver stage:This section helps in improving the power
level of serial decoder to sufficient level todrive the buzzer.
THEORY:
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Here the system is build around the
microcontroller. IR system is introduced forthe system. There are two barriers from both
sides. Here if a train comes from one side
that will cut or interrupts the IR barrier and
that is why a signal from the IR sensor comes
to microcontroller. It is then recorded inmicrocontroller memory and now second IR
barrier is also broken then second signal of
+5 volt is send to microcontroller. Now
microcontroller makes track no 1 busy by
sending a signal to parallel to serial decoder.
Which is transmitted to receiver section
through a ASK transmitter. This in turn glow a
single LED on the track map. If that train
passes the third IR barrier then it is alright. If
that is not happen a train from other
direction comes then other microcontroller
detects it and issue a signal at output pin to
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sends signal to ASK transmitter in similar
process as first microcontroller does. It is
transmitted at 433MHz frequency. Anotherred LED is also glow on the track. Showing
that two trains are on same track going for
head on collision.
IR beam moves in straight line and follows all
the rules of visible light source. If any opaque
comes on the way then dark area is created
behind it. IR beam used is of invisible in
nature. So sensor scheme is not affected by
other light source. As long as IR light falling
on the sensor, its output is low. IR sensor
output is made high as light is interrupted
due to train. This is transmitted to
microcontroller indicating a train is passing
through IR barrier. Two barrier schemes is
arranged to know the train is coming or
going.
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OPERATION PROCEDURE:
Now take track 1 into consideration, if a
train is coming from right side it interrupts
the first sensor then next sensor this
indicates that train is coming to protected
zone. Now microcontroller makes the track 1
is busy in its memory. This train is goingtowards left so sensors interrupted in
outgoing fashion, so now microcontroller
makes it free zone.
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In busy condition another train comes into
protected zone then microcontroller detectsit create a visible alarm signal and send to
both train through a wireless digital
transmission. This makes the train driver alert
about two trains on the same track. Train
driver make the train off.
CIRCUIT DESCRIPTION:
There are four sections: transmitter sectionReceiver sectionIR transmitter &
receiverPower supply
section
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TRANSMITTER SECTION:
Here used TX433 as ASK transmitter & HT12E
as parallel to serial encoder. Single bit data is
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fed to pin 10 of encoder. Pin 1 to 8 are
address bit & 10 to 13 are data input. It
converts 4 bit data & 8 bit address in to serialdata so that it can be transmitted serially
through ASK transmitter. Tx is built using SMD
components and very small in size. Pin 4 of
the TX is antenna and is 17 cm long wire and
that is telescopic antenna. Data fed to tx at
pin 2.
ASK transmitter & serial encoder:
Here TX433 ASK transmitter circuit is used.
It is a integrated chip. It operates in +5
volt. There four terminals.
Pin 1 - Ground
Pin2 - Data input from serial encoder
Pin3 - Vcc
Pin4 - Antenna
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12 bit serial encoder HT12 E is used for
converting the binary data input to serialdata. Inputs are provided at pin 10 to 13
from microcontroller. There is a oscillator
resistor 1 M connected in between 15 & 16.
Pin 1 to 8 is for address pin.
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RECEIVER & SERIAL
DECODER:
ASK receiver RX433 operates at 433 MHz.There are 8 pins in this chip.
Pin 1, 6 & 7 --- GNDPin 2 --- data outputPin 4, 5 --- + VccPin 8 --- Antenna
The data is fed into HT12D, the serialdecoder. It converts the serial data into fourbit binary output.
Pin 10 to 13 --- four bit binary outputPin 13 --- connected with audioindicator using driver amplifier.Pin 14 --- data inputPin 1 to 8 --- address pinPin 15 & 16 --- Oscillator resistorsPin 17 --- data receive
acknowledgement
A NAND gate 4093 is used for detection of
two head on situation and makes alarm. Its
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inputs are 1 & 2 with output is 3. Output is
provided with a PNP transistor driver to drive
the buzzer.
IR BARRIER USING IR LED & TRANSISTOR:
Here IR led is connected directly to power
supply +5v using a proper value of resistor.
IR led emits light straight. It follows all the
theories of light like reflection & refraction. It
can not pass the opaque object as light
passes through it. As IR light falls on the IR
transistor, it starts to switch ON. Here we are
making a optical coupling between a LED & a
transistor. This is called IR barrier. According
to intensity of light falls on base of transistor,
its output varies. When a person enters into
barrier it totally blocks the light flow therefore
making a large change in output signal. This
signal variation may be high or low according
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to transistor type NPN/PNP. This signal is to be
fed to logic device for further action. Before
that the signal must be made 1/0. So anOPAMP is used as a comparator to make it
possible.
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(IR BARRIER 1)
(IR BARRIER 2)
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The circuit uses a IR transistor as the basic
element for IR sensing. The variation in light
reflection light will result into a correspondingvariation in voltage at collector/emitter of the
transistor which is provided to pin 3 & pin5 of
each MCP602 opamp. A 10k resistor is used in
collector. Preset 100k is used as a
reference voltage generator. There are two
OPAMPS inside the IC so two comparators
operates simultaneously in it. Two sensor
inputs are provided to pin 3 & 5. Reference
voltage is given to pin 2 & 6. Power supply
given +5 v to pin 8 & ground to pin 4.
MICROCONTROLLER
SECTION:
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Microcontroller PIC16F628.
CIRCUIT DESCRIPTION:
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description in theory section the
microcontroller is programmed.
POWER SUPPLY:
The microcontroller needed to be operating in
DC power supply. The microcontroller needs
+5V supply. The transformer is a center tap
12-0-12V 500mA. It is then rectified using fullwave rectifier. A 1000F capacitor is used for
filtration purpose. The three terminal voltage
regulators 7805 provides regulated DC
outputs for the operation of the circuit. A
good grounding is necessary for the proper
functioning of the circuit.
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SOME IMPORTANT
DISCUSSIONS:
ASK ( AMPLITUDE SHIFT KEYING ):-
MODULATION:
Modulation is the process of modifying the
characteristic of one signal in accordance withsome characteristic of another signal. In most
cases, the information signal, be it voice,
video, binary data, or some other information,
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is normally used to modify a higher-frequency
signal known as the carrier. The information
signal is usually called the modulatingsignal, and the higher-frequency signal which
is being modulated is called the carrier or
modulated wave.The carrier is usually a sine
wave, while the information signal can be of
any shape, permitting both analog and digital
signals to be transmitted. In most cases, the
carrier frequency is considerably higher than
the highest information frequency to be
transmitted.
AMPLITUDE MODULATION WITH SINE WAVES:
In AM, the information signal varies the
amplitude of the carrier sine wave. In other
words, instantaneous value of the carrier
amplitude changes in accordance with the
amplitude and frequency variations of the
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modulating signal. Figure 2-1 shows a single-
frequency sine wave modulating a higher-
frequency carrier signal. Note that the carrierfrequency remains constant during the
modulation process but that its amplitude
varies in accordance with the modulating
signal. An increase in the modulating signal
amplitude causes the amplitude of the carrier
to increase. Both the positive and negative
peaks of the carrier wave vary with the
modulating signal. An increase or decrease- in
the amplitude of the modulating signal causes
a corresponding increase or decrease in both
the positive and . negative peaks of the
carrier amplitude.
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If you interconnect the positive and negative
peaks of the carrier waveform with animaginary line (shown dashed in Fig. 2-1),
then you re-create the exact shape of the
modulating information signal. This imaginary
line on the carrier waveform is known as the
envelope, and it is the same as themodulating signal. Because complex
waveforms like that shown in Fig. 2-1 are
difficult to draw, they are usually simplified by
representing the high frequency carrier waves
simply many equally spaced vertical lines
whose amplitudes vary in accordance with a
modulating signal. Figure 2-2 shows a sine
wave tone modulating a higher-frequency
carrier. We will use this method of
representation throughout this book.
In AM, the information signal varies the
amplitude of the carrier sine wave. In other
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words, instantaneous value of the carrier
amplitude changes in accordance with the
amplitude and frequency variations of themodulating signal. Figure 2-1 shows a single-
frequency sine wave modulating a higher-
frequency carrier signal. Note that the carrier
frequency remains constant during the
modulation process but that its amplitude
varies in accordance with the modulating
signal. An increase in the modulating signal
amplitude causes the amplitude of the carrier
to increase. Both the positive and negative
peaks of the carrier wave vary with the
modulating signal. An increase or decrease- in
the amplitude of the modulating signal causes
a corresponding increase or decrease in both
the positive and . negative peaks of the
carrier amplitude.
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The signals illustrated in Figs. 2-1 and 2-2
show the variation of the carrier signal withrespect to time. Such signals are said to be in
the time domain.Time-domain signals are the
actual variation of voltage over time. They are
what you would see displayed on the screen
of an oscilloscope. In this section we show the
AM types of modulation. Later you will see
that modulated signals can also be expressed
in the frequency domain
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(Amplitude Modulation with Digital Signals)
Digital, usually binary, signals may also be
used to amplitude modulate a carrier. Figure
2-4 shows a binary signal modulating a sine
wave carrier. In Fig. 2-4(a), the binary 1 level
produces maximum carrier amplitude and the
binary 0 level produces a lower-value carrier.
Amplitude modulation in which the carrier is
switched between two different carrier levels
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is known as amplitude shift keying (ASK). A
special fonn of ASK is one in which the carrier
is simply switched on or off. See Fig. 2-4(b).The binary 1 level turns the carrier on, and
the binary 0 level turns the carrier off. This is
called on-off keying (OOK). Some digital
signals have more than two levels. As long as
a signal varies in discrete steps, it is
considered digital. Figure 2-5 shows a four-
level digital signal and the resulting AM
signal. To improve the speed of digital
transmission in computer modems, 4-, 8-, 16-
and 32-level digital signals are commonly
used. Amplitude modulation is combined with
simultaneous phase modulation of a carrier to
produce quadrature amplitude modulation
(QAM).
BRIEF TALK ON MICROCONTROLLER:
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The past three decades have seen the
introduction of a technology that has radically
changed the way in which we analyze thecontrol the world around us. Born of parallel
developments in computer architecture and
integrated circuit fabrication, the
microprocessor or computer on a chip first
became a commercial reality in 1971 with
introduction of 4-bit 4004 by Intel corp.A byproduct of microprocessor development
was the microcontroller. The same
fabrication techniques and programming
concept that make possible the general
purpose microprocessor also yielded the
microcontroller.
Microcontroller are not as well as known to
the general public, or to many in the
technical community, as are he more
glamorous microprocessor . The public is
however very aware that something isresponsible for all of the smart VCRs, clock
radios, washers and dryers, video games,
telephones, microwaves ,TVs, automobiles,
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toys vending machines, copiers, elevators,
irons and myriads of other articles that are
intelligent and programmable. Companiesare also aware that being competitive in this
age of microchip requires their products, or
the machinery they use to make those
products, to have some smart.
Figure below shows the block diagram of a
typical microcontroller, which is truecomputer on a chip. The design incorporates
all of the features found in a microprocessor
CPU; ALU, PC, SP, register. It also has added
the other features needed to make a
complete computer: ROM, RAM, parallel I/O,
serial I/O, counters, and a clock circuit.
Like the microprocessor, a microcontroller is a
general purpose device, but one that is meant
to read data, performs limited calculations on
that data, and control its environment based
on those calculation. The prime use of amicrocontroller is to control the operation of a
machine using a fixed program that is stored
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in ROM and that does not change over the
lifetime of the system.
The design approach of the microcontrollermirrors that of the microprocessor: make a
single design that can be used in as many
applications as possible in order to sell,
hopefully, as many as possible. The
microprocessor accomplishes the goal by
having a very flexible and extensiverepertoire of multisystem instructions. These
instruction work in a hardware configuration
that enables large amounts of memory and
I/O to be connected address and data bus
pins on integrated circuit package. Much of
the activity in the microprocessor has to do
with moving code and data to and from
external memory to the CPU. The architecture
feature s working registers that can be
programmed to take part in the memory
access process, and instruction set is aimedat expediting this activity in order to improve
throughput. The pins connected to the
microprocessor to external memory are
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unique, each having a single function. Data
is handled in byte, or larger , sizes.
The microcontroller design uses a much morelimited set of single and double byte
instructions that are used to move code and
data from internal memory to ALU. Many
instructions are coupled with pins on
integrated circuit package, the pins are
programmable that is capable of havingseveral different functions depending on the
wishes of the programmer. The
microcontroller is concerned with getting
data from and to its own pins ; the
architecture and instruction set are
optimized to handle data in bit and byte size.
In AM, the information signal varies the
amplitude of the carrier sine wave. In other
words, instantaneous value of the carrier
amplitude changes in accordance with the
amplitude and frequency variations of the
modulating signal. Figure 2-1 shows a single-
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frequency sine wave modulating a higher-
frequency carrier signal. Note that the carrier
frequency remains constant during themodulation process but that its amplitude
varies in accordance with the modulating
signal. An increase in the modulating signal
amplitude causes the amplitude of the carrier
to increase. Both the positive and negative
peaks of the carrier wave vary with the
modulating signal. An increase or decrease- in
the amplitude of the modulating signal causes
a corresponding increase or decrease in both
the positive and . negative peaks of the
carrier amplitude.
The contrast between a microcontroller and a
microprocessor is best exemplified by the
fact that most microprocessor s have manyoperational codes(opcodes) for moving data
from external memory to the CPU;
microcontrollers may have one or two.
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Microprocessor may have one or two types of
bit handling instructions; microcontrollers
have many.
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BLOCK DIAGRAM OF MICROCONTROLLER
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COMPONENT DESCRIPTION:
PIC16F84A / F628 ( 8-BIT FLASH
MICROCONTROLLER):
Microcontroller features:
Only 35 instructions to learn
High performance RISC CPU
All single cycle instruction except forprogram branches which are two cycle
Operating speed DC- 20MHz clock inputDC 200 ns instruction
cycle 1024 words of program memory
68 bytes of data EEPROM
64 bytes of data EEPROM
14-bit wide instruction words
8-bit wide data bytes
15 special function hardware registers
eight level deep hardware stack
direct , indirect and relative addressingmodes
four interrupt sources
- external RB0/INT pin
- TMR0 timer overflow
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- PortB ,7:4> interrupt on change
- Data EEPROM write complete
Peripheral features:
13 I/O pins with individual direction control
high current sink/source for direct LED drive
- 25mA sink max per pin
- 25mA source max per pin
TMR0 : 8-bit timer /counter with 8-bitprogrammable prescaler
Special microcontroller features:
1000 erase/write cycles enhanced flashprogram memory
1,000,000 typical typical erase/write cyclesEEPROM data memory
EEPROM DATA RETENTION > 40 YEARS
INCIRCUIT SERIAL PROGRAMMING - VIA
TWO PINS POWER ON RESET (POR) POWER UP TIMER
(PWRT)OSILLATOR START-UP TIMER (OST)
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WATCHDOG TIMER (wtd) WITH ITS OWN
ON-CHIP RC OSCILLATOR FOR RELIABLE
OPERATION CODE PROTECTION
POWER SAVING SLEEP MODE
SELECTABLE OSCILLATOR OPTIONS
CMOS ENHANCED FLASH/EEPROM TECHNOLOGY:
LOW POWER, HIGH-SPEED TECHNOLOGY
FULLY STATIC DESIGN
WIDE OPERATING VOLTAGE RANGE
- COMMERCIAL : 2.0 V TO 5.5 V
-
INDUSTRIAL : 2.0 V TO 5.5 V LOW POWER CONSUMPTION
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ARCHITECTURAL OVERVIEW:
The high performance of the PIC16F84A can
be attributed to a number of architectural
features commonly found in RISC
microprocessors. To being with, thePIC16F84A uses a Harvard architecture, in
which, program and data are accessed from
separate memories. This improves bandwidth
over traditional von Neumann architecture
where program and data are fetched from the
same memory. Separating program and data
memory further allows instructions to be
sized differently than the 8-bit wide data
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word. Instruction opcodes are 14-bits wide
making it possible to have all single word
instructions. A 14-bit wide program memoryaccess but fetches a single cycle. A two-stage
pipeline overlaps fetch and execution of
instructions (see Example 3-1). Consequently,
all instructions execute in a single cycle (200
ns @ 20 MHz) except for program branches.
The PIC16F84A addresses 1K x 14 programmemory. All program memory is internal.
The PIC16F84A can directly indirectly address
its register files or data memory. All special
function registers including the program
counter are mapped in the data memory. An
orthogonal (symmetrical) instruction set that
makes it possible to carry out any operation
on any register using any addressing mode.
This symmetrical nature and lack of special
optimal situations make programming with
the PIC16F84A simple yet efficient. Inaddition, the learning curve is reduced
significantly.
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PIC16F84A devices contain an 8-bit ALU and
working register. The ALU is a general
purpose arithmetic unit. It performsarithmetic and Boolean functions between
data in the working register and any register
file.
The ALU is 8-bit wide and capable of addition,
subtraction, shift and logical operations.
Unless otherwise mentioned, arithmeticoperations are twos complement in nature. In
two operand instruction, typically one
operand is the working register (W register),
and the other operand is a file register or an
immediate constant. In single operand
instructions, the operand is either the W
register or a file register.
The W register is an 8-bt working register
used for ALU operation. It is not an
addressable register. Depending on the
instruction executed, the ALU may affect thevalues of the Carry , Digit Carry (DC), and
Zero (Z) bits in the STATUS register. The C
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and DC bits operate as a borrow and digit
borrow out bit, respectively, in subtraction.
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MEMORY ORGANIZATION:
There are two memory blocks in the
PIC16F84A. These are the program memory
and the data memory. Each block has its own
bus, so that access to each block can occur
during the same oscillator cycle. The data
memory can further be broken down into the
general purpose RAM and the Special
Function Registers (SFRs). The operation of
the SFRs that control the core are described
here. The SFRs used to control the peripheral
modules are described in the sectiondiscussing each individual peripheral module.
The data memory area also contains the data
EEPROM memory. This memory is not directly
mapped into the data memory, but is
indirectly mapped. That is an indirect address
pointer specifies the address of the data
EEPROM memory to read/write. The 64 bytes
of data EEPROM memory have the address
range 00 - 3Fh.
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Program Memory Organization:
The PIC16F84A has a 13-bit program counter
capable of addressing an 8K x 14-program
memory space. For the PIC16F84A only the
first 1K x 14 (0000-03FFh) are physically
implemented. Accessing a location above the
physically implemented address will cause a
wrap-around. For example, locations 20h
420h, C20h, 1020h, 1420h, 1820h, and 1C20h
will be the same instruction. The reset vector
is at 0000h and the interrupt vector is at
0004h
Data Memory Organization:
The data memory is partitioned into twoareas. The first is the Special Function
Registers (SFR) area, while the second is the
General Purpose Registers (GPR) area. The
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SFRs control the operation of the device.
Portions of data memory are banked. This is
for both the SFR area and the GPR area. TheGPR area is banked to allow greater than 96
bytes of general purpose RAM. The banked
areas of the SFR are for the registers that
control the peripheral functions. Banking
requires the use of control bits for bank
selection. These control bits are located in theSTATUS Register.
Instructions MOVWF and MOVF and move
values from the W register to any location in
the register file (F), and vice-versa. The
entire data memory can be accessed either
directly or indirectly through the File Select
Register (FSR). Indirect addressing used the
present value of the RP1:RP0 bits for access
into the banked areas of data memory.
In AM, the information signal varies the
amplitude of the carrier sine wave. In otherwords, instantaneous value of the carrier
amplitude changes in accordance with the
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amplitude and frequency variations of the
modulating signal. Figure 2-1 shows a single-
frequency sine wave modulating a higher-frequency carrier signal. Note that the carrier
frequency remains constant during the
modulation process but that its amplitude
varies in accordance with the modulating
signal. An increase in the modulating signal
amplitude causes the amplitude of the carrier
to increase. Both the positive and negative
peaks of the carrier wave vary with the
modulating signal. An increase or decrease- in
the amplitude of the modulating signal causes
a corresponding increase or decrease in both
the positive and . negative peaks of the
carrier amplitude.
Data memory is partitioned into two banks
which contain the general purpose registers
and the special function registers. Bank 0 is
selected by clearing the RP0 bit
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(STATUS). Setting the RP0 bit select Bank
1. Each Bank extends up to 7Fh (128 bytes).
The lower locations of each Bank are reservedfor the Special Function Registers. Above the
Special Function Registers are General
Purpose Registers implemented as static
RAM.
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GENERAL PURPOSE REGISTER FILE:
The register file is accessed either directly or
indirectly through the FSR. All devices have
some amount of GPR area. The GPR is 8-bits
wide. When the GPR area is greater then 96,
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banking must be performed to access the
additional memory space
PORTA and TRISA Registers:
PORTA is a 5-bit wide latch. RA4 is a Schmitt
trigger input and an open collector output. All
other RA port pins have TTL input levels andfull CMOS output drivers. All pins have data
direction bits (TRIS registers) which can
configure these pins as output or input. A
1on any bit in the TRISA registers puts the
corresponding output driver in a high-
impedance mode. A 0 on any bit in theTRISA register puts the contents of the output
latch on the selected pin(s). Reading the
PORTA register reads the status of the pins
whereas writing to it will write to the port
latch. All write operations are read-modify
write operations. So a write to a port implied
that the port pins are firs read, then this value
is modified and written to the port data latch.
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PORTB and TRISB Registers:
PORTB is an 8-bit wide bi-directional port. The
corresponding data direction register is
TRISB. A 1 on any bit in the TRISB register
puts the corresponding output driver in a high
impedance mode. A 0 on any bit in the
TRISB register puts the contents of the output
latch on the selected pin(s).
Each of the PORTB pins have a weak internalpull-up. A single control bit can turn on all the
pull-ups. This is done by clearing the RBPU
(OPTION) bit. The weak pull-up is
automatically turned off when the port pin is
configured as an output the pull-ups are
disabled on POR. Four of PORTBs pins, RB7,
RB4, have an interrupt on change feature.
Only pins configured as inputs can cause this
interrupt to occur (i.e. any RB7:RB4 pin con-
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figured as an output is excluded from the
interrupt on change comparison). The pins
value in input mode are compared with theold value latched on the last read of PORTB.
The mismatch outputs of the pins are ORed
together to generate the RBIF interrupt
(INTCON).
DATA EEPROM MEMORY:
The EEPROM data memory is readable andwritable during normal operation (full VDDrange). This memory is not directly mapped inthe register file space. Instead it is indirectly
addressed through the Special FunctionRegisters. There are four SFRs used to readand write this memory. These registers are:
EECON1
EECON2 (Not a physically implementedregister)
EEDATA
EEADREEDATA holds the 8-bit data for read/write,and EEADR holds the address of the EEPROMlocation being accessed. PIC16F84A devices
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have 64 bytes of data EEPROM with anaddress range from oh to 3Fh.The EEPROM data memory allows byte read
and write. A byte write automatically erasesthe location and data memory is rated forhigh erase/write cycles. The write time iscontrolled by an on-chip timer. The write timewill vary with voltage and temperature as wellas from chip to chip. Please refer to ACspecifications for exact limits.
When the device is code protected, the CPUmay continue to read and write the dataEEPROM memory. The device programmercan no longer access this memory.
Reading the Eeprom Data Memory:
To read a data memory location, the usermust write the address to the EEADR registerand then set control bit RD (EECON1).The data is available, in the very next cycle,in the EEDATA register; therefore it can beread in the next instruction, EEDATA will holdthis value until another read or until it is
written to by the user (during a writeoperation).
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DATA EEPROM READBCF STATUS, RP0 ; Bank 0MOVLWCONFIG_ADDR ;MOVWFEEADR ; Address to read
BSF STATUS, RP0 ; Bank 1BSF EECON1, RD ; EE Read
BCF STATUS, RP0 ; Bank 0MOVF EEDATA, W ; W = EEDATA
Writing to the EEPROM Data Memory:To write an EEPROM data location, the usermust first write the address to the EEADRregister and the data to the EEDATA register.Then the user must follow a specific sequenceto initiate the write for each byte.BSF STATUS, RPO ; Bank 1BCF INTCON, GIE ; Disable INTs.BSF EECON1, WREN; Enable writeMOVLW55H ;MOVWFEECON2 ; Write 55hMOVLWAAh ;
MOVWFEECON2 ; Write AAhBSF EECON 1,WR ; Set WR bit beginwriteBSF INTCON, GIE ; Enable INTs.
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The write will not initiate if the abovesequence is not exactly followed (write 55h toEECON2, write AAh to EECON2, then set WR
bit) for each byte. We strongly recommendthat interrupts be disabled during this codesegment.Additionally, the WREN bit in EECON 1must beset to enable write. This mechanism preventsaccidental writes to data EEPROM due toerrant (unexpected) code execution (i.e., lost
programs). The user should keep the WRENbit clear at all times, except when updatingEEPROM. The WREN bit is not cleared byhardware.After a write sequence has been initiated,clearing the WREN bit will not affect thiswrite cycle. The WR bit will be inhibited frombeing set unless the WREN bit is set.At the completion of the write cycle, the WRbit is cleared in hardware and cycle, the WRbit is cleared in hardware and the EE WriteComplete Interrupt Flag bit (EEIF) is set. Theuser can either enable this interrupt or pollthis bit. EEIF must be cleared by software.
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Depending on the application goodprogramming practice may dictate that thevalue written to the Data EEPROM should beverified to the desired value to be written.
This should be used in applications where anEEPROM bit will be stressed near thespecification limit. The Total Endurance diskwill help determine your comfort level.
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Generally the EEPROM write failure will be abit which was written as a o, but reads backas a 1 (due to leakage off the bit).
WRITE VERIFY:
BCF STATUS, RPO ; Bank o: ; Any code can go here: ;MOVF EEDATA, W ; Must be in Bank oBSF STATUS, RP0 ; Bank1 READBSF EECON1, RD ; YES, Read the
; value writtenBCF STATUS, RP0 ; Bank o;; Is the value written (in w reg) and;read (in EEDATA) the same
SUBWF EEDATA, W ;BTFSS STATUS, Z ; Is difference 0 ?GOTO WRITE_ERR ; NO, Write error : ; YES, Good write: ; Continue program
Configuration Bits:
The configuration bits can be programmed
(read as 0) or left unprogrammed (read as
1) to select various device configurations.
These bits are mapped in program memory
location 2007h.
Note that address 2007h is beyond the user
program memory space. In fact, it belongs to
the special test/configuration memory space
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(2000h 3FFh), which can be accessed only
during programming.
OSCILLATOR CONFIGURATION:
Oscillator types:
The PIC16F84A can be operated in fourdifferent oscillator modes. The user can
program two configuration bits (FOSC1 and
FOSCO) to select one of these four modes:
LP Low Power Crystal
XT Crystal/Resonator
HS High Speed Crystal/Resonator
RC Resistor/Capacitor
CRYSTAL OSCILLATOR / CERMIC RESONATORS:
In XT, LP or HS modes a crystal or ceramic
resonator is connected to the OSC1/CLKINand OSC2/CLKOUT pins to establish oscillation
(Figure 8-2). The PIC16F84A oscillator design
requires the use of a parallel cut crystal. Use
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of a series cut crystal may give a frequency
out of the crystal manufactures specifications.
When in XT, LP or HS modes, the device canhave an external clock source to drive the
OSC1/CLKIN PIN.
Watchdog Timer (WDT):
The watchdog timer is realized as a freerunning on-chip RC oscillator which does not
require any external components. This RC
oscillator is separate from the RC oscillator of
the OSC1/CLKIN pin. That means that the
WDT will run even if the clock on the
OSC1/CLKIN and OSC2/CLKOUT pins of the
device has been stopped, for example, by
execution of a SLEEP instruction. During
normal operation a WDT time-out generates
device RESET. If the device is in SLEEP mode,
a WDT time-out causes the device to wake-upand continue with normal operation. The WDT
can be permanently disabled by programming
configuration fuse WDTE as a 0.
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Code Protection:
The code in the program memory and data
EEPROM memory can be protected by
programming the code protect bit.
INSTRUCTION SET:
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A RISC processor has only 35 instructions.
.
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7805 ( +5V VOLTAGE REGULATOR) :-
3-Terminal 1A Positive Voltage Regulator
Features:
Output Current up to 1A
Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18,
24V
Thermal Overload Protection
Short Circuit Protection
Output Transistor Safe Operating Area
Protection
Description:
The MC78XX/LM78XX/MC78XXA series of
three terminal positive regulators are
available in the TO-220/D-PAK package andwith several fixed output voltages, making
them useful in a wide range of applications.
Each type employs internal current limiting,
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thermal shut down and safe operating area
protection, making it essentially
indestructible. If adequate heat sinking isprovided, they can deliver over 1A output
current. Although designed primarily as fixed
voltage regulators, these devices can be used
with external components to obtain
adjustable voltages and currents.
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TESTING PROCEDURE:
After completion of the assembling of the
electronics components on PCB. All the
circuits are arranged on a board. Power is
made on . Take a multimeter and check
output voltage of the power supply for +5v
& check in all parts of the project. Now IR
beam scheme is to check. When light falls
output of the sensor is 0.0v and when train
comes in front of the sensor output voltage
is +5v. Check output of the sensor 5.0v
when interrupted.
Transmitter is tuned to receiver. Transmitter
is sending signal at 433MHz frequency. Now
turn the trimmer at same time press the TE
switch so output of the receiver
acknowledgement signal high. Now it is
tuned.
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CONCLUSION:
The project is build around the
microcontroller; ASK communication & IR
barrier system. Project detects train
automatically using IR beam scheme. Alert
signal is provided to trains through ASK
transmission. Same ASK scheme can be used
in large number of tracks by varying the
address. Microcontroller is intelligent brain of
the project.
Here ASK transmitter is of low range therefore
it is applicable to small region. But it can be
improved to large region by using power
amplifier.
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