ABSTRACT

Aim of this project is control the unmanned rail gate automatically using embedded platform.

Today often we see news papers very often about the railway accidents happening at un-

attended railway gates. Present project is designed to avoid such accidents if implemented in

spirit.

This project utilizes two powerful IR transmitter and two receivers, one pair of transmitter and

receiver is fixed at upside (from the train comes) at a level higher than human being in exact

alignment and similarly other pair is fixed at down side of the train direction sensor activation

time is so adjusted by calculating the time taken at a certain speed to cross at least one

compartment of standard minimum size of the Indian railway, normally 5 seconds.

The sensors are fixed at 1000 meters on both sides of the gate, we call fore side sensor pair

for common towards gate train, and aft side sensors for the train just Crosses the gate. When

train cross the fore side sensor it gives signal to the gate receiver to close the gate. The buzzer

is activated to clear the gate area for drivers about 5 seconds. Gate motor is turned on in one

direction and gate is closed, and stay closed till train crosses the gate and reaches aft side

sensors when aft side receiver get activated motor turns in opposite direction and gate opens

and motor stops .

If there is any problem in the gate means it will operate red signal on both side fro the driver

indication.

Train arrival and departure sensing can be achieved by means of Relay techniques. When the

wheels of the train moves over, both tracks are shorted to ground and this acts as a signal to

microcontroller (89C51) indicating train arrival. RED signal appears for the road user, once the

train cuts the relay sensor placed before the 5Kms before the gate .A buzzer is made on as a pre

cautionary measure for the road users.

1

CHAPTER -1

INTRODUCTION

2

INTRODUCTION

Railway gate control is a project that can control the by pass road gates i.e when train is

coming near to the gate pass the gates motor will be active and both the gates now in closed

state so that no one can pass through it and when train completely passed through that passage

the gates will open shortly using sensor like IR module sensor that sense the train for coming

status as well as for complete passage of the train. the main application of this project is to

protect accidents and to provide new generation automation in train system.

Present project is designed using AT89C51 microcontroller to avoid railway accidents

happening at unattended railway gates, if implemented in spirit. This project utilizes two

powerful IR transmitters and two receivers; one pair of transmitter and receiver is fixed at up

side (from where the train comes) at a level higher than a human being in exact alignment and

similarly the other pair is fixed at down side of the train direction. Sensor activation time is so

adjusted by calculating the time taken at a certain speed to cross at least one compartment of

standard minimum size of the Indian railway. We have considered 5 seconds for this project.

Sensors are fixed at 1km on both sides of the gate. We call the sensor along the train direction

as ‘foreside sensor’ and the other as ‘aft side sensor’. When foreside receiver gets activated, the

gate motor is turned on in one direction and the gate is closed and stays closed until the train

crosses the gate and reaches aft side sensors. When aft side receiver gets activated motor turns

in opposite direction and gate opens and motor stops. Buzzer will immediately sound at the

fore side receiver activation and gate will close after 5 seconds, so giving time to drivers to

clear gate area in order to avoid trapping between the gates and stop sound after the train has

crossed.

The same principle is applied for track switching. Considering a situation wherein an express

train and a local train are traveling in opposite directions on the same track; the express train is

allowed to travel on the same track and the local train has to switch on to the other track. Two

sensors are placed at the either sides of the junction where the track switches. If there’s a train

approaching from the other side, then another sensor placed along that direction gets activated

and will send an interrupt to the controller. The interrupt service routine switches the track.

3

Indicator lights have been provided to avoid collisions. Here the switching operation is

performed using a stepper motor. Assuming that within a certain delay, the train has passed the

track is switched back to its original position, allowing the first train to pass without any

interruption. This concept of track switching can be applied at 1km distance from the stations.

Gate Control:

Railways being the cheapest mode of transportation are preferred over all the

other means .When we go through the daily newspapers we come across many railway

accidents occurring at unmanned railway crossings. This is mainly due to the carelessness in

manual operations or lack of workers. We, in this project has come up with a solution for the

same. Using simple electronic components we have tried to automate the control of railway

gates. As a train approaches the railway crossing from either side, the sensors placed at a

certain distance from the gate detects the approaching train and accordingly controls the

operation of the gate. Also an indicator light has been provided to alert the motorists about the

approaching train.

4

CHAPTER -2

WORKING

5

WORKING OPERATION: -

The arrival of train is detected by the sensor placed on either side of the gate at about 5km

from the level crossing. Once the arrival is sensed , the sensed signal is sent to

the microcontroller and it checks for possible presence of vehicle between the gates, again

using sensors. Once, no vehicle is sensed in between the gate the motor is activated and the

gates are closed. When no obstacle is sensed GREEN light is indicated, and the train is to free

to move.

The departure of the train is detected by sensors placed at about 1km from the gate. The signal

about the departure is sent to the microcontroller, which in turn operates the motor and opens

the gate.

AUTOMATIC RAILWAY GATE CONTROL & TRACK SWITCHING

To avoid railway accidents happening at unattended railway gates, if implemented in spirit.

This project utilizes two powerful IR transmitters and two receivers; one pair of transmitter and

receiver is fixed at up side (from where the train comes) at a level higher than a human being in

exact alignment and similarly the other pair is fixed at down side of the train direction. Sensor

activation time is so adjusted by calculating the time taken at a certain speed to cross at least

one compartment of standard minimum size of the Indian railway. We have considered 5

seconds for this project. Sensors are fixed at 1km on both sides of the gate. We call the sensor

along the train direction as ‘foreside sensor’ and the other as ‘aft side sensor’. When foreside

receiver gets activated, the gate motor is turned on in one direction and the gate is closed and

stays closed until the train crosses the gate and reaches aft side sensors. When aft side receiver

gets activated motor turns in opposite direction and gate opens and motor stops. Buzzer will

immediately sound at the fore side receiver activation and gate will close after 5 seconds, so

giving time to drivers to clear gate area in order to avoid trapping between the gates and stop

sound after the train has crossed.

The same principle is applied for track switching. Considering a situation wherein an

express train and a local train are traveling in opposite directions on the same track; the express

train is allowed to travel on the same track and the local train has to switch on to the other 6

track. Two sensors are placed at the either sides of the junction where the track switches. If

there’s a train approaching from the other side, then another sensor placed along that direction

gets activated and will send an interrupt to the controller. The interrupt service routine switches

the track. Indicator lights have been provided to avoid collisions. Here the switching operation

is performed using a stepper motor. Assuming that within a certain delay, the train has passed

the track is switched back to its original position, allowing the first train to pass without any

interruption. This concept of track switching can be applied at 1km distance from the stations.

Th

e project is simple to implement and subject to further improvement.

2. BASIC IDEA

GATE CONTROL

Railways being the cheapest mode of transportation are preferred over all the other

means .When we go through the daily newspapers we come across many railway accidents

occurring at unmanned railway crossings. This is mainly due to the carelessness in manual

operations or lack of workers. We, in this project has come up with a solution for the same.

Using simple electronic components we have tried to automate the control of railway gates. As

a train approaches the railway crossing from either side, the sensors placed at a certain distance

7

from the gate detects the approaching train and accordingly controls the operation of the gate.

Also an indicator light has been provided to alert

Using the same principle as that for gate control, we have developed a concept of

automatic track switching. Considering a situation wherein an express train and a local train are

travelling in opposite directions on the same track; the express train is allowed to travel on the

same track and the local train has to switch on to the other track. Indicator lights have been

provided to avoid collisions .

8

9

CHAPTER -3

3. HARDWARE DESCRIPTION

The project consists of three main parts:

8051 microcontroller

IR Transmitter

IR Receiver

Stepper Motor Circuit

10

3. HARDWARE DESCRIPTION

The project consists of three main parts:

8051 microcontroller

IR Transmitter

IR Receiver

Stepper Motor Circuit

CIRCUIT DIAGRAM:-

11

COMPONENTS:

PIC16F877A (MICROCONTROLLER)

LM7805 Voltage Regulator +5V

Capacitor

1N4007 DIODE

Resistor

Potentiometer

Crystal Oscillator

Switch

LM358

IR sensor

PCB (Printed Circuit Board)

Geared motors

12

MICROCONTROLLER

PIC16F877A (MICROCONTROLLER):-

This document contains device specific information about the following devices:

• PIC16F877A

PIC16F874A/877A devices are available in 40-pin and 44-pin packages.

All devices in the PIC16F87XA family share common architecture withthe following

differences:

• The PIC16F873A and PIC16F874A have one-half of the total on-chip memory of the

PIC16F876A and PIC16F877A.

• The 28-pin devices have three I/O ports, while the 40/44-pin devices have five.

• The 28-pin devices have fourteen interrupts, while the 40/44-pin devices have fifteen.

• The 28-pin devices have five A/D input channels, while the 40/44-pin devices have eight.

• The Parallel Slave Port is implemented only on the 40/44-pin devices.

13

14

15

IR CIRCUITS

This circuit has two stages: a transmitter unit and a receiver unit. The transmitter unit

consists of an infrared LED and its associated circuitry. unit. The transmitter unit consists of an

infrared LED and its associated circuitry.

IR TRANSMITTER

The transmitter circuit consists of the following components:

Resistors

Capacitors

IR LED

The IR LED emitting infrared light is put on in the transmitting unit. To generate IR

signal, 555 IC based astable multivibrator is used. Infrared LED is driven through transistor

BC 548.

IC 555 is used to construct an astable multivibrator which has two quasi-stable states.

It generates a square wave of frequency 38kHz and amplitude 5Volts. It is required to switch

‘ON

16

LM7805 Voltage Regulator +5V

A voltage regulator is designed to automatically maintain a constant voltage level. A voltage

regulator may be a simple "feed-forward" design or may include negative feedback control

loops. It may use an electromechanical mechanism, or electronic components. Depending on

the design, it may be used to regulate one or more AC or DC voltages.

The 78xx (sometimes LM78xx) is a family of self-contained fixed linear voltage regulator

integrated circuits. The 78xx family is commonly used in electronic circuits requiring a

regulated power supply due to their ease-of-use and low cost. For ICs within the family, the xx

is replaced with two digits, indicating the output voltage (for example, the 7805 has a 5 volt

output, while the 7812 produces 12 volts). The 78xx line are positive voltage regulators: they

produce a voltage that is positive relative to a common ground.

CIRCUITS OF VOLTAGE REGULATING IC’S

The 78XX series of voltage regulator are intended to provide a fixed voltage for use with a

variety of different circuits. They are available in a range of different voltages as shown below

and, although only the positive variety are considered here, there is a complimentary range of

negative regulators that are essentially identical. The voltage regulators are capable of

providing currents of up to 1.5A with adequate heat-sinking and internal protection circuitry

17

makes them almost indestructible. In other configurations and with extra components, these

regulators can be employed as variable voltage sources or constant current sources

CAPACITOR :-

Capacitors are components that are used to store an electrical charge. Sometimes capacitors are

used to smooth a current in a circuit. When power is supplied to a circuit that includes a

capacitor - the capacitor charges up. When power is turned off the capacitor discharges its

electrical charge slowly.

18

Symbols of capacitors

A battery will transport charge from one plate to other until the voltage produced by the

charge buildup is equal to the battery voltage.

19

Capacitor Polarization generally refers to the electrolytic type capacitors but mainly the

Aluminium Electrolytic's, with regards to their electrical connection. The majority of

electrolytic capacitors are polarized types, that is the voltage connected to the capacitor

terminals must have the correct polarity, i.e. positive to positive and negative to negative.

1N4007 DIODE:-

The most common function of a diode is to allow an electric current to pass in one direction

(called the diode's forward direction), while blocking current in the opposite direction

(the reverse direction). Thus, the diode can be viewed as an electronic version of a check valve.

This unidirectional behavior is called rectification, and is used to convert alternating

current to direct current, including extraction of modulation from radio signals in radio

receivers these diodes are forms of rectifiers.

20

RESISTOR:-

A resistor is a component of an electrical circuit that resists the flow of electrical current.

A resistor has two terminals across which electricity must pass, and is designed to drop the

voltage of the current.

A resistor is primarily used to create and maintain a known safe current within an electrical

component.

Resistance is measured in ohms , after Ohm 's law.

This rule states that electrical resistance is equal to the drop in voltage across the terminals of

the resistor divided by the current being applied to the resistor.

A high ohm rating indicates a high resistance to current.

This rating can be written in a number of different ways depending on the ohm rating.

For example- 81R represents 81 ohms, while 81K represents 81,000 ohms.

Series and parallel connection of resistors

In a series configuration, the current through all of the resistors is the same, but the voltage

across each resistor will be in proportion to its resistance. The potential difference (voltage)

seen across the network is the sum of those voltages, thus the total resistance can be found as

the sum of those resistances:

21

The parallel equivalent resistance can be represented in equations by two vertical lines "||" (as

in geometry) as a simplified notation. Occasionally two slashes "//" are used instead of "||", in

case the keyboard or font lacks the vertical line symbol. For the case of two resistors in

parallel, this can be calculated using:

POTENTIOMETER (POT / VARIABLE RESISITOR) :-

A pot in electronics technology is a component. A three-terminal resistor with a sliding

contact that forms an adjustable voltage divider. If only two terminals are used, one end

and the wiper, it acts as a variable resistor or rheostat. A potentiometer measuring

instrument is essentially a voltage divider used for measuring electric potential (voltage); The

component is an implementation of the same principle, hence its name.

22

SYMBOLS OF VARIABLE RESISTOR

Linear taper potentiometer

A linear taper potentiometer (linear describes the electrical characteristic of the device,

not the geometry of the resistive element) has a resistive element of constant cross-section,

resulting in a device where the resistance between the contact (wiper) and one end terminal

is proportional to the distance between them. Linear taper potentiometers are used when the

division ratio of the potentiometer must be proportional to the angle of shaft rotation (or slider

position), for example, controls used for adjusting the centering of an analog cathode-

ray oscilloscope

23

CRYSTAL OSCILLATOR:-

A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a

vibrating crystal of piezoelectric material to create an electrical signal with a very precise

frequency. This frequency is commonly used to keep track of time (as in quartz wristwatches),

to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for

radio transmitters and receivers. The most common type of piezoelectric resonator used is the

quartz crystal, so oscillator circuits incorporating them became known as crystal oscillators,

but other piezoelectric materials including polycrystalline ceramics are used in similar circuits.

Quartz crystals are manufactured for frequencies from a few tens of kilohertz to tens of

megahertz. More than two billion crystals are manufactured annually. Most are used for

consumer devices such as wristwatches, clocks, radios, computers, and cell phones. Quartz

crystals are also found inside test and measurement equipment, such as counters, signal

generators, and oscilloscopes.

24

SWITCH:-

In electrical engineering, a switch is an electrical component that can break an electrical

circuit, interrupting the current or diverting it from one conductor to another.

The most familiar form of switch is a manually operated electromechanical device with one or

more sets of electrical contacts, which are connected to external circuits. Each set of contacts

can be in one of two states: either "closed" meaning the contacts are touching and electricity

can flow between them, or "open", meaning the contacts are separated and the switch is

nonconducting. The mechanism actuating the transition between these two states (open or

closed) can be either a "toggle" (flip switch for continuous "on" or "off") or "momentary"

(push-for "on" or push-for "off") type.

25

LIGHT EMITING DIODE (LED) :-

A light-emitting diode (LED) is

a semiconductor light source. LEDs are used as

indicator lamps in many devices and are increasingly

used for other lighting. When a light-

emitting diode is forward biased (switched

on), electrons are able to recombine with electron

holes within the device, releasing energy the form

of photons. This effect is called electro luminescence

and the color of the light (corresponding to the

energy of the photon) is determined by the energy

gap of the semiconductor. An LED is often small in

area (less than 1 mm2), and integrated optical

components may be used to shape its radiation pattern. LEDs present many advantages over

incandescent light sources including lower energy consumption, longer lifetime, improved

physical robustness, smaller size, and faster switching. LEDs powerful enough for room

lighting are relatively expensive and require more precise current and heat management than

compact fluorescent lamp sources of comparable output.

26

Appearing as practical electronic components in 1962, early LEDs emitted low-intensity red

light, but modern versions are available across the visible, ultraviolet,

and infrared wavelengths, with very high brightness.

LED CONNECTION:-

DIFFERENT TYPES OF LED:-

LM35 sensor (Precision Centigrade Temperature Sensors)

27

General Description

The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is

linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage

over linear temperature sensors calibrated in ˚ Kelvin, as the user is not required to subtract a

large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does

not require any external calibration or trimming to provide typical accuracies of ±1⁄4˚C at

room temperature and ±3⁄4˚C over a full −55 to +150˚C temperature range. Low cost is assured

by trimming and calibration at the wafer level. The LM35’s low output impedance, linear

output, and precise inherent calibration make interfacing to readout or control circuitry

especially easy. It can be used with single power supplies, or with plus and minus supplies. As

it draws only 60 µA from its supply, it has very low self-heating, less than 0.1˚C in still air.

The LM35 is rated to operate over a −55˚ to +150˚C temperature range, while the LM35C is

rated for a −40˚ to +110˚C range (−10˚ with improved accuracy). The LM35 series is available

packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are

also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-

lead surface mount small outline package and a plastic TO-220 package.

28

FEATURES:-

n Calibrated directly in ˚ Celsius (Centigrade)

n Linear + 10.0 mV/˚C scale factor

n 0.5˚C accuracy guaranteeable (at +25˚C)

n Rated for full −55˚ to +150˚C range

n Suitable for remote applications

n Low cost due to wafer-level trimming

n Operates from 4 to 30 volts

n Less than 60 µA current drain

n Low self-heating, 0.08˚C in still air

n Nonlinearity only ±1⁄4˚C typical

n Low impedance output, 0.1 Ω for 1 mA load

29

APPLICATIONS OF LED:-

In general, all the LED products can be divided into two major parts, the public lighting and

indoor lighting. LED uses fall into four major categories:

Visual signals where light goes more or less directly from the source to the human eye, to

convey a message or meaning.

Illumination where light is reflected from objects to give visual response of these objects.

Measuring and interacting with processes involving no human vision.

Narrow band light sensors where LEDs operate in a reverse-bias mode and respond to incident

light, instead of emitting light.

For more than 70 years, until the LED, practically all lighting was incandescent and fluorescent

with the first fluorescent light only being commercially available after the 1939 World's Fair.

30

DIGITAL INPUTS:-

Digital inputs can be define as that which inputs those having in digital signal condition i.e.

high or low, either Vs or VE on other hand in binary form 1 or 0 these types of signal are

known as digital inputs signals. These digital inputs are provide by digital sensor modules or

switches.

Here we use for digital inputs some switches and IR sensor digital module which gives us a

digital inputs to the controlling part of this project

IR MODULE :-

In this tutorial we will see how to make simple infrared sensor module for detecting reflecting

surface. This sensor can be used to detect reflecting silver/white strip, obstacle detection, flame

detection, etc. These sensors are primary requirement of any simple line follower robocar.

WORKING OF IR SENSORS:-

IR LED emits infrared radiation. This radiation illuminates the surface in front of LED.

Surface reflects the infrared light. Depending on reflectivity of the surface, amount of light

reflected varies. This reflected light is made incident on reverse biased IR sensor. When

photons are incident on reverse biased junction of this diode, electron-hole pairs are generated,

which results in reverse leakage current. Amount of electron-hole pairs generated depends on

intensity of incident IR radiation. More intense radiation results in more reverse leakage

current. This current can be passed through a resistor so as to get proportional voltage. Thus as

intensity of incident rays varies, voltage across resistor will vary accordingly.

31

This voltage can then be given to OPAMP based comparator. Output of the comparator can be

read.

IR LED is used as a source of infrared rays. It comes in two packages 3mm or 5mm. 3mm is

better as it is requires less space. IR sensor is nothing but a diode, which is sensitive for

infrared radiation. This infrared transmitter and receiver is called as IR TX-RX pair. It can be

obtained from any decent electronics component shop and costs less than 10Rs. Following

snap shows 3mm and 5mm IR pairs. Colour of IR transmitter and receiver is different.

However you may come across pairs which appear exactly same or even has opposite colours

than shown in above pic and it is not possible to distinguish between TX and RX visually. In

case you will have to take help of

multimeter to distinguish between them

The IR LED is just like any other LED, in

that a current-limiting resistor is useful to

control the device current and therefore the

light intensity. With a 100 ohm resistor and

the approximately 1.5V forward voltage

drop of the IR LED, we'll have a LED current of about 35mA. That's fairly high, but more light

emitted will yield more light coming back to our sensor.

The phototransistor is a device with an exposed silicon junction. When light passes through the

plastic casing, most non-IR wavelengths are simply absorbed by the plastic, but the infrared

light makes it to the sensor within. Each photon striking the silicon junction causes an electron

to flow. Because this is a phototransistor and not a photodiode, this current is multiplied by the

transistor's current gain, so each photon may actually cause perhaps 10 to 100 electrons to

flow. This current has nowhere to go except through the 10K resistor, and as the current passes

through the resistor, the voltage across the resistor rises (V=IR). This change in voltage is read

by our microcontroller's Analog to Digital Converter (ADC).

32

LM324 (LOW POWER QUAD OPERATIONAL AMPLIFIERS) :-

These circuits consist of four independent, high gain, internally frequency compensated

operational amplifiers .

They operate from a single power supply over a wide range of voltages.

Operation from split power supplies is also possible and the low power supply current drain is

independent of the magnitude of the power supply voltage.

Operation from split power supplies is also possible so long as the difference between the two

supplies is 3 volts to 32 volts.

Application areas include transducer amplifier, DC gain blocks and all the conventional OP

Amp circuits which now can be easily implemented in single power supply systems.

Internally Frequency Compensated for Unity Gain

Large DC Voltage Gain: 100dB

Wide Power Supply Range: LM324: 3V~32V (or 1.5 ~16V)

Input Common Mode Voltage Range Includes Ground

33

Large Output Voltage Swing: 0V to VCC -1.5V

Power Drain Suitable for Battery Operation

34

APPLICATIONS OF LM:-

The LM35 can be applied easily in the same way as other integrated-circuit temperature

sensors. It can be glued or cemented to a surface and its temperature will be within about

0.01˚C of the surface temperature. This presumes that the ambient air temperature is almost the

same as the surface temperature; if the air temperature were much higher or lower than the

surface temperature, the actual temperature of the LM35 die would be at an intermediate

temperature between the surface temperature and the air temperature. This is expecially true

for the TO-92 plastic package, where the copper leads are the principal thermal path to carry

heat into the device, so its temperature might be closer to the air temperature than to the

surface temperature. To minimize this problem, be sure that the wiring to the LM35, as it

leaves the device, is held at the same temperature as the surface of interest. The easiest way to

do this is to cover up these wires with a bead of epoxy which will insure that the leads and

wires are all at the same temperature as the surface, and that the LM35 die’s temperature will

not be affected by the air temperature. The TO-46 metal package can also be soldered to a

metal surface or pipe without damage. Of course, in that case the V− terminal of the circuit will

be grounded to that metal. Alternatively, the LM35 can be mounted inside a sealed-end metal

tube, and can then be dipped into a bath or screwed into a threaded hole in a tank. As with any

IC, the LM35 and accompanying wiring and circuits must be kept insulated and dry, to avoid

leakage and corrosion. This is especially true if the circuit may operate at cold temperatures

where condensation can occur. Printed-circuit coatings and varnishes such as Humiseal and

epoxy paints or dips are often used to insure that moisture cannot corrode the LM35 or its

connections.These devices are sometimes soldered to a small light-weight heat fin, to decrease

the thermal time constant and speed up the response in slowly-moving air. On the other hand, a

small thermal mass may be added to the sensor, to give the steadiest reading despite small

deviations in the air temperature.

35

BUZZER :-

A buzzer or beeper is an audio signalling device, which may be mechanical, electromechanical,

or piezoelectric. Typical uses of buzzers and beepers include alarm devices, timers and

confirmation of user input such as a mouse click or keystroke.

PIEZOELECTRIC:-

A piezoelectric element may be driven by an oscillating electronic circuit or other audio signal

source, driven with a piezoelectric audio amplifier. Sounds commonly used to indicate that a

button has been pressed are a click, a ring or a beep.

36

DC MOTOR:-

A DC motor is a mechanically commutated electric motor powered from direct current (DC).

The stator is stationary in space by definition and therefore so is its current. The current in the

rotor is switched by the commutator to also be stationary in space. This is how the relative

angle between the stator and rotor magnetic flux is maintained near 90 degrees, which

generates the maximum torque.

DC motors have a rotating armature winding but non-rotating armature magnetic field and a

static field winding or permanent magnet. Different connections of the field and armature

winding provide different inherent speed/torque regulation characteristics. The speed of a DC

motor can be controlled by changing the voltage applied to the armature or by changing the

field current. The introduction of variable resistance in the armature circuit or field circuit

allowed speed control. Modern DC motors are often controlled by power electronics systems

called DC drives.

37

Alternating current differ from DC in the direction of electron flow , first in one direction for

a short time , then reverse direction and flow again in opposite direction for short time . The

flow of electrons in one direction and then in another direction is called a cycle of AC . The

number of cycles occur in one second of time is called “Cycles/Second”. In our country the

standard power line frequency is 50 Hz .

The major blocks of the power supply units are

Step down transformer

Rectifier diodes

Filters

Voltage regulators

STEP DOWN TRANSFORMER:-

The instrument transformer for power supply in this project is to convert AC from

230V to required low level such as 5V AC . This transformer apart from stepping down AC

voltage, gives isolation between power source and power supply circuitries.

38

RECTIFIER UNIT :-

In a power supply unit , rectification is normally achieved by a solid state diode .

Diode contains two electrodes called the anode and the cathode . A diode has the property that

will let electron flow easily in one direction . As a result when AC is applied to a diode,

electrons only flow when the anode is positive and cathode is negative. Reversing the polarity

of voltage applied to a diode will not permit electron flow .

The various method of rectifying AC to DC or half wave , full wave and bridge

rectifications . This project employs a full wave bridge rectifier which is most commonly used

in industries.

A bridge structure of four diodes is commonly used in power supply units to

achieve full wave rectification. When AC voltage is applied to the primary winding of power

transformer. It is stepped down to 5V AC across the secondary winding of the transformer.

Normally one alteration of the input voltage will cause the polarities to reverse. Opposite end

of the transformer will therefore, always be 180 degrees out of phase with each other.

For positive cycle, two diodes connected to the top winding gets positive voltage

and only one diode conducts for that cycle due to forward bias. At the same time one out of the

other two diodes conducts, for the negative voltage being applied from the bottom winding due

to forward bias for that diode DC of frequency 100Hz.

In the next alteration the two diodes conducted from top winding and bottom winding as they

are forward biased in this cycle. It is to be noted that the current flow through the load is

always in one direction for each alteration of the applied AC input. This is of course, means

that AC is rectified into DC. This DC output, in this case, has a ripple frequency of 100Hz,

since each alternation produces a resulting output pulse, the ripple frequency or 2*50 Hz

=100Hz. The output DC is not a pure DC. It is pulsating DC voltage.

39

Filter Unit:-

After pulsating DC has been produced by our rectifier, it must be filtered in or for it

to be usable in a power supply. Filtering involves the ripple frequency. The power supply unit

employed in this project used 7805 voltage regulator (for positive output voltages ) and a 7905

regulator ( for negative output voltages ).

Resistors R1 and R2 maintain line load regulation. Capacitors C2 and C4 act

as high frequency suppressors.

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CHAPTER -4

Microcontroller

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Microcontroller

INTRODUCTION :

A computer-on-a-chip is a variation of a microprocessor, which combines the processor core

(CPU), some memory, and I/O (input/output) lines, all on one chip. The computer-on-a-chip is called

the microcomputer whose proper meaning is a computer using a (number of) microprocessor(s) as its

CPUs, while the concept of the microcomputer is known to be a microcontroller. A microcontroller can

be viewed as a set of digital logic circuits integrated on a single silicon chip. This chip is used for only

specific applications.

7.2.1 ADVANTAGES OF USING A MICROCONTROLLER OVER MICROPROCESSOR:

A designer will use a Microcontroller to

1. Gather input from various sensors

2. Process this input into a set of actions

3. Use the output mechanisms on the Microcontroller to do something useful

4. RAM and ROM are inbuilt in the MC.

5. Cheap compared to MP.

6. Multi machine control is possible simultaneously.

Examples:

8051, 89C51 (ATMAL), PIC (Microchip), Motorola (Motorola), ARM Processor, Applications:

Cell phones, Computers, Robots, Interfacing to two pc’s.

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89c51 Microcontroller IC

The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4Kbytes of Flash

programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s

high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51

instruction set and pin out. The on-chip Flash allows the 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 AT89C51 is a powerful microcomputer, which provides

a highly-flexible and cost-effective solution to many embedded control applications. The

AT89C51 provides the following standard features: 4Kbytes of Flash, 128 bytes of RAM, 32

I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex

serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 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 hardware

reset.

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7.2.2 Pin description of ATMEL At89c51:

Fig: 7.2. 2 The AT 89c51 micro controller is a 40-pin IC. The 40th pin of the controller is Vcc pin and the

5V dc supply is given to this pin. This 20 th pin is ground pin. A 12 MHZ crystal oscillator is

connected to 18th and 19th pins of the AT 89c51 micro controller and two 22pf capacitors are

connected to ground from 18th and 19th pins. The 9th pin is Reset pin.

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Port 0

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 may

also be configured to be the multiplexed low order address/data bus during accesses 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

(IIL) because of the internal pull-ups. Port 1 also receives the low-order address bytes during Flash

programming and verification.

Port 2

Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output 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. As inputs Port 2 pins that are externally being pulled low will source current (IIL)

because of the internal pull-ups. Port 2 emits the high-order address byte during fetches from external

program memory and during accesses to external data memory that uses 16-bit addresses (MOVX @

DPTR). In this application, it uses strong internal pull-ups when emitting 1s. During accesses to

external data memory that uses 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2

Special Function Register. Port 2 also receives the high-order address bits and some control signals

during Flash programming and verification.

Port 3

Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3 output 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

(IIL) because of the pull-ups. Port 3 also serves the functions of various special features of the

AT89C51 as listed below:

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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)

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

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

ALE/PROG

Address Latch Enable output pulse for latching the low byte of the address during accesses 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 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 micro controller is in external

execution mode.

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PSEN

Program Store Enable is the read strobe to external program memory. When the AT89C51 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. EA should be strapped to VCC for internal

program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash

programming, for parts that require 12-volt VPP.

XTAL1

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

XTAL2

It is the output from the inverting oscillator amplifier.

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CHAPTER -5

PCB MANUFACTURING PROCESS.

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PCB MANUFACTURING PROCESS:

It is an important process in the fabrication of electronic equipment. The design of PCBs

(Printed Circuit Boards) depends on circuit requirements like noise immunity, working

frequency and voltage levels etc. High power PCBs requires a special design strategy.

The fabrication process to the printed circuit board will determine to a large extent the price

and reliability to the equipment. A common target aimed is the fabrication of small series of

highly reliable professional quality PCBs with low investment cost. The target becomes

especially important for custom tailored equipment in the area of industrial electronics.

PREPARE SOLUTION FOR ITCHING LAYOUT:-

NOW DROP PRINTED CIRCUIT BOARD INTO SOLUTION:-

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WAIT FOR 3 MINUTES FOR COMPLETE CLEANING EXTRA COPPER ON BOARD:-

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CONCLUSION:

From the above discussion and information of this system we, upto now

surely comes to know that it is highly reliable effective and economical at dense

traffic area, sub urban area and the route where frequency of trains is more.

As it saves some auxiliary structure as well as the expenditure onattendant it is more

economical at above mentioned places than traditional railwaycrossing gate system. We know

that though it is very beneficial but it is alsoimpossible to install such system at each and every

places, but it gives certainly aconsiderable benefit to us, thereby to our nation.www

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REFERENCES:

1. Kenneth.J.Ayala”The 89C51 Microcontroller Architecture programming

and Applications”, Pen ram International.

2. D.Roychoudary and Sail Jain”L.I.C”, New Age International.

3. “Principles of Electronics” by V.K.MEHTA.

4. “Communication Systems” by Simon Hawkins.

5. “Electrical Technology – vol. 2- B.L. Theraja.

WEB REFERENCES:

1. http://www.learn-c.com/adc0809.pdf

2. http://www.atmel.com/dyn/resources/prod_documents/doc0265.pdf

3. http://www.ortodoxism.ro/datasheets/texasinstruments/max232.pdf

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