6th Sem Report

Christ Polytechnic Institute Page 1

A

Project Report

On

“Automatic railway crossing gate control ”

Guided By: Prepared By:

Mr. Raj Vyas 1. Dharaja Darshan D. (096100311047)

2.Koladiya Divyesh V. (096100311048)

Lab Teacher: 3.Mehta Kandarp H .(09610031059)

Mr.Raj Vyas

June : 2012

DEPARTMENT OF ELECTRONICS & COMMUNICATION

CHRIST POLYTECHNIC INSTITUTE



RAJKOT

CERTIFICATE

This is to certify that Mr. Dharajia Darshan Dilipbhai Enrollment

no. 096100311047 of Semester VI (E.C.) has satisfactorily

prepared and presented his project report on “Automatic railway

crossing gate control ” within four walls of the EC laboratory of

this institute during January to June 2012.

Date of Submission:

Guided By: Mr. Raj Vyas HOD (EC)

PRINCIPAL



RAJKOT

CERTIFICATE This is to certify that Mr. Koladiya Divyesh Vallabhbhai

Enrollment no. 096100311048 of Semester VI (E.C.) has

satisfactorily prepared and presented his project report on

“Automatic railway crossing gate control ” within four walls of

the EC laboratory of this institute during January to June 2012.

Date of Submission:


PRINCIPAL



RAJKOT

CERTIFICATE

This is to certify that Mr. Kandarp Hareshkumar Mehta

Enrollment no. 096100311059 of Semester VI (E.C.) has

satisfactorily prepared and presented his project report on

“Automatic railway crossing gate control ” within four walls of

the EC laboratory of this institute during January to June 2012.

Date of Submission:


PRINCIPAL


ABSTRACT

This project work aims at the design, development, fabrication and

testing of working model entitled Automatic Railway Gate Controller. It

is basically related to Radio communication and signaling system. An

Automatic Railway gate controller is unique in which the railway gate is

closed and opened or operated by the Train itself by eliminating the

chances of human errors.

The largest public sector in India is the Railways. The network of

Indian Railways covering the length and breath of Indian Railways

covering the length and breath of our country is divided into nine

Railway zones for operational convenience. The railway tracks criss-

cross the state Highways and of course village road along their own

length. The points or places where the Railway track crosses the road

are called level crossings. Level crossings cannot be used

simultaneously both by road traffic and trains, as this result in

accidents leading to loss of precious lives.

So to prevent this we use the concept of the automatic railway gate

controlled concept. Here we use two identical sensors on both the side

of the track. One on the right side which is forward sensor and another

on the left side which is afterward sensor. Train rolls over the path and

cuts the sensors so the gate will be automatically controlled.

By this there is less human effort and the technology will raise the level

from where it begins.

( i )


ACKNOWLEDGEMENT

I express my cavernous sense of obligation and gratitude to my guide

Shri Raj Vyas for his genuine guidance and constant encouragement

throughout this work. I am highly obliged as my honorable guide have

devoted his valuable time and shared his expertise knowledge.

I say heartly thanks to Mr. Niraj Trivedi & Mr. Saurabh Pansora

because without them our project can’t complete. They deeply conduct the

project during lab session. They helped us lot n the project work. They gave

us the opportunity to do the project work.

I extend my sincere thanks to HOD Mr. Jaldeep Vaghela Department

of Electronics & Communication Engineering with all faculty members of the

Christ Polytechnic Institute for providing me such an opportunity to do my

project work.

I also wish to express my heartfelt appreciation to Prof.A.R.Dave and

my parents, friends, colleagues and many who have rendered their support

for the successful completion of the project, both explicitly and implicitly.

Mr.Tarun Patel has explained in detailed about functioning in their

industry. Than he has personally ask some few question related to our

semester's subjects. Than he has assign us this project. He has also

discussed lot about this project with us gave basic idea to us etc...

Dharaja Darshan D. (096100311047)

Koladiya Divyesh V. (096100311048)

Mehta Kandarp H. (096100311059)

( ii )


CONTENT

Abstract i

Acknowledgement ii

List of Figures iii

List of Tables iv

List of Data-Sheets v

Chapter 1 Introduction 13 to 17

1.1 Introduction

1.2 Aim

1.3 Idea of choose this project

1.4 Problem Summary

1.5 Concept

1.6 Component list

1.7 Please read before using this circuit ideas

Chapter 2 Description of Problem 18 to 25

2.1 Detailed description of problem.

2.2 Gate control

2.3 Hardware description

2.4 8051 microcontroller interfacing

2.5 IR circuit

2.6 IR transmitter

2.7 IR receiver

2.8 Block diagram & its description


Chapter 3 Various part and circuits 26 to 49

3.1 Stepper motor circuit

3.2 Resister

3.3 Lights functioning

3.4 Gate mechanisms

3.5 Flasher operation

3.6 Gate crossing circuit operation notes

3.7 Function of stepper motor

3.7.1 Stepper motor Characteristics

3.7.2 open loop v/s close loop commutation

3.7.3 Types

3.7.4 Stepper motor drive ckt

3.7.5 Phase current waveform

3.7.6 Theory

3.7.7 Stepper motor rating and specification

3.7.8 Application

3.8 BC-547

3.8.1 Pin Diagram

3.8.2 Description

3.9 74LS-04/08

3.9.1 Internal construction and pin diagram

3.10 ULN2003

3.10.1 pin diagram

3.10.2 pin description

3.10.3 internal ckt


Chapter 4 Detailed Microcontroller 50 to 57

4.1 89c51 Introduction

4.2 89c51

4.2.1 Description

4.2.2 Features

4.2.3 Architecture block diagram

4.2.4 Pin description

Chapter 5 Concept of track 58 to 76

5.1 Overview & introduction

5.1.1 How to sense a black line ?

5.1.2 How to control DC motor ?

5.1.3 Components values

5.2 The Chasis

5.3 Motor & Power transmission

5.3.1 Introduction

5.3.2 Specification

5.4 The Wheels

5.5 Circuit Discription

5.6 Operting L293D motor driver

5.7 Operation of LM324

5.7.1 pin diagram

5.7.2 pin description

5.8 sensor

5.8.1 photo diode

5.8.2 principal of operation

5.8.3 other mode of operation

5.8.4 material

5.8.5 features

5.8.6 Application

5.8.7 photo-diode array


5.8.8 obstacle detection using IR-led photo diode

5.8.9 circuit

Advantages & Dis-advantages 77

Chapter 6 Conclusion 78

Chapter 7 Further Extended 79

Bibliography 80

Appendix


List of Figures

2.1 Arrangement of sensors 20

2.2 Gate control 21

2.3 Interfacing with 8051 23

2.4 block diagram of automatic gate control 25

3.1 Lights display 30

3.2 Old gate mechanism 32

3.3 Morden gate mechanism 33

3.4 Gate operation 34

3.5 Gate crossing circuit operation 36

3.6 Construction of stepper motor 37

3.7 Front view of stepper motor 38

3.8 Stepper motor with driver ckt 40

3.9 Phase current waveform 41

3.10 overview,symbols & pinconfiguration

of bc547 43

3.11 Pin diagram 44

3.12 Internal construction and configuration 46

3.13 Internal ckt of uln2003 47

3.14 pin diagram 48

3.15 pin description 48

4.1 Architecture 52

4.2 pin diagram 53

5.1 3d graphical representation of robot 58

5.2 pcb interfacing ckt of line follower robot 61

5.3 picture image of line-follower robot 62

5.4 construction and picture image of motor 63

5.5 internals of motor 64

5.6 wheels 66

5.7 l293d motor driver 69

5.8 pin configuration 70

5.9 symbol of photo-diode 71


List of Tables

1.1 Pin functions of ULN2003 48

1.2 Parts of line follower 59

1.3 Pin description of LM324 71

(iv)


List of Data-Sheets

1. L293D

2. Transister (BC547)

3. ULN2003

4. LM324

5. 74LS04

6. 74LS08

(v)


Chapter: 1

1.1 Introduction:

This project work aims at the design, development, fabrication and testing

of working model entitled Automatic Railway Gate Controller. It is basically

related to Radio communication and signaling system. An Automatic

Railway gate controller is unique in which the railway gate is closed and

opened or operated by the Train itself by eliminating the chances of

human errors.

1.2 AIM :

The largest public sector in India is the Railways. The network of Indian

Railways covering the length and breath of Indian Railways covering the

length and breath of our country is divided into nine Railway zones for

operational convenience. The railway tracks crises-cross the state Highways

and of course village road along their own length. The points or places where

the Railway track crosses the road are called level crossings. Level crossings

cannot be used simultaneously both by road traffic and trains, as this result in


Aim of this project is to control the unmanned rail gate automatically using

embedded platform. Today often we see news papers very often about the

railway accidents happening at unattended railway gates. Present project is

designed to avoid such accidents if implemented in spirit. This project is

developed in order to help the INDIAN RAILWAYS in making its present

working system a better one, by eliminating some of the loopholes existing in

it. Based on the responses and reports obtained as a result of the significant

development in the working system of INDIAN RAILWAYS.


This project can be further extended to meet the demands according to

situation. This can be further implemented to have control room to regulate

the working of the system. Thus becomes the user friendliness.

In this project AT89c51 Micro controller Integrated Chip plays the main role.

The program for this project is embedded in this Micro controller Integrated

Chip and interfaced to all the peripherals. The timer program is inside the

Micro controller IC to maintain all the functions as per the scheduled time.

Stepper motors are used for the purpose of gate control interfaced with

current drivers chip ULN2003 itâ„¢s a 16 pin IC.

1.3 Idea of choose this project :

We read in to the news papers very often about the railway accidents

happening at un-attended railway gates. In too many villages there are

still absences of the railway crossing gates. Many human-beings as

well as animals are being victim of this situation.

By this only we get the idea of the automatic railway gate which is

controlled automatically. Whenever the train is coming from the near

by distance the gate will automatically closed with the help of

SENSORS placed near by at some distance.

And whenever the train is pass through some distance from the gate

than the gate will automatically open respectively

Present project is designed to avoid such accidents if implemented in

spirit.


1.4 Problem summary :

Automatic railway crossing gate control is the name of our IDP. The

respected project is assigned to us by the owner of the Industry NISUS

MICROTECH.

We the members of this project haspersonally visited this company on

08\08\2011. The following company is there in Ahmedabad. Basically it works

on Microcontroller. It also works on the following functions:

• PLC (Programmable Logic Controller)

• SCADA (Supervisory control & Data Acquit ion)

• HMI (Human Machine Interfaces)

• AC/DC/Servo Drive

• Process Instrument

• Switch Gear & Heavy Electric

• DCS (Distributed control system)

Our aim of problem is to Controlling Gate while crossing the railway

automatically. Which is to be done with the help sensors which spread IR

rays?


1.5 Concept :

Concept of our project is automatic gate will be controlled. For this we use

two powerful IR sensors on both the sides before and after the gate. For open

and close of the gate steeper motor is used which is controlled by the

controller 8051. As the train will pass through the sensors on either by sides

the IR rays will be cuts-off. This message is sensed by controller and gives

command to the steeper motor and respectively it will open or close the gate.

The concept is purely designed by us only. Also how to control the steeper

motor and how to sense the signal from the sensor is to be finalized by the

controller 8051 only with the help of specific programming with it.

1.6 Railway Crossing Circuit Component List

2 - 8051 Microcontroller

2 - Steeper Motor

LED ( Red , Green )

2 - L293D ( Motor Driver )

BC-547 for sensor section

1 - 74ls04

1 - 74ls08

2 – ULN2003

Registers & capacitors

IR-led and Photodiode for sensors (x’mitter & receiver)


1.7 Please Read Before Using These Circuit Ideas

The explanations for the circuits on these pages cannot hope to cover every

situation on every layout. For this reason be prepared to do some

experimenting to get the results you want. This is especially true of circuits

such as the "Across Track Infrared Detection" circuits and any other circuit

that relies on other than direct electronic inputs, such as switches.

If you use any of these circuit ideas, ask your parts supplier for a copy of the

manufacturer’s data sheets for any components that you have not used

before. These sheets contain a wealth of data and circuit design information

that no electronic or print article could approach and will save time and

perhaps damage to the components themselves. These data sheets can

often be found on the web site of the device manufacturers.

Although the circuits are functional the pages are not meant to be full

descriptions of each circuit but rather as guides for adapting them for use by

others. If you have any questions or comments please send those to the

email address on the Circuit Index page.


Chapter: 2 Description of Problem

2.1 Detailed Description of Problem:

Present project is designed using 8051 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’ which is on the forward side

of the gate and the other as ‘aft side sensor’ which are on the after side of

the gate.

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

respectively this phenomenon happens for the another train comes.

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.


Fig.1.1arrange of the sensors.

2.2 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.


As we know that there are two sensors place at both the sides on forward-

side and another on the after-side.

So when the train will come from the forward side it will cut the rays of the

forward-sensor and the stepper motor runs with the help of relay and the

gate will be closed.

Now as the train will pass through the gate than it will travel to the

afterword direction and the after-side sensors’ rays will cut’s off so the

steeper motor will close its function and remain off and the gate will

automatically open respectively.

Fig.1.2 Gate Control

Here as we have talked earlier two sensors are placed before and after

side of the gate. One traffic light indicator is placed for giving the warning

to the people who crosses the track.


2.3 Hardware Description:

The project consists of four main parts:

• 8051 microcontroller

• IR Transmitter

• IR Receiver

• Stepper Motor Circuit

2.4 8051 Microcontroller Interfacing

The I/O ports of the 8051 are expanded by connecting it to an 8255 chip.

The 8255 is programmed as a simple I/O port for connection with devices

such as LEDs, stepper motors and sensors.

There is no necessity to connect 8255 chip. But here we connected it to

overcome from the loadingeffect.The following block diagram shows the

various devices connected to the different ports of an 8255 and indirectly

with the 8051.

The ports are each 8-bit. The individual ports of the 8255 can be

programmed to be input or output, and can be changed dynamically. The

control register is programmed in simple I/O mode with port A, port B and

port C (upper) as output ports and port C (lower) as an input port.

Here steeper motor for gate controlling is interface with the controller.

Indicating lights for indicating whether the way is clear or not is interface

with controller. And the IR sensors are interfaced with it to sense whether

the train has passed through it or not.


Figure 1.3 Interfacing with 8051

2.5 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.


2.6 IR Transmitter:

The transmitter circuit consists of the following components:

• IC 555

• Resistors

• Capacitors

• IR LED

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

generate IR signal, 555 IC based astablemultivibrator is used. Infrared

LED is driven through transistor BC 548.

IC 555 is used to construct an astablemultivibrator which has two quasi-

stable states. It generates a square wave of frequency 38 kHz and

amplitude 5Volts. It is required to switch ‘ON’ the IR LED.

2.7 IR Receiver:

The receiver circuit consists of the following components:

• TSOP1738 (sensor)

• IC 555

• Resistors

• Capacitors

The receiver unit consists of a sensor and its associated circuitry. In

receiver section, the first part is a sensor, which detects IR pulses

transmitted by IR-LED. Whenever a train crosses the sensor, the output of

IR sensor momentarily transits through a low state.


As a result the monostable is triggered and a short pulse is applied to the

port pin of the 8051 microcontroller. On receiving a pulse from the sensor

circuit, the controller activates the circuitry required for closing and

opening of the gates and for track switching.

2.8 Block Diagram & its description:

1.4 Block diagram of automatic gate control

Above is the detailed block diagram of the Automatic gate control. It

consists of various blocks. Description of each and every block is shown

below,

• Track: The idea of using track here is of Line-follower. The line

follower is the which can considered as the train and the Black line which

is sensed by it is our track. As the robot is continous sensing the black

line and follow the track

• Gate ( 1 & 2 ): Gate is the design which allow the public to go through

the track when there is no conversation. It is simply made by plastic

material. Gate get the signaling from motor. There are two gate on by the

side of the track. It runs as per the mechanical work.


Chapter: 3 Various parts & Circuits:

3.1 Stepper Motor Circuit:

Here a stepper motor is used for controlling the gates. A stepper motor is

a widely used device that translates electrical pulses into mechanical

movement. They function as their name suggests – they “step” a little bit

at a time.

Steppers don’t simply respond to a clock signal. They have several

windings which need to be energized in the correct sequence before the

motor’s shaft will rotate. Reversing the order of the sequence will cause

the motor to rotate the other way.

3.2 Resister:

A linear resistor is a linear, passive two-terminal electrical component that

implements electrical resistance as a circuit element. The current through a

resistor is in direct proportion to the voltage across the resistor's terminals.

Thus, the ratio of the voltage applied across a resistor's terminals to the

intensity of current through the circuit is called resistance. This relation is

represented by Ohm's law:

Resistors are common elements of electrical networks and electronic circuits

and are ubiquitous in most electronic equipment. Practical resistors can be

made of various compounds and films, as well as resistance wire (wire made

of a high-receptivity alloy, such as nickel-chrome). Resistors are also

implemented within integrated circuits, particularly analog devices, and can

also be integrated into hybrid and printed circuits.


The electrical functionality of a resistor is specified by its resistance: common

commercial resistors are manufactured over a range of more than nine orders

of magnitude. When specifying that resistance in an electronic design, the

required precision of the resistance may require attention to the

manufacturing tolerance of the chosen resistor, according to its specific

application. The temperature coefficient of the resistance may also be of

concern in some precision applications. Practical resistors are also specified

as having a maximum power rating which must exceed the anticipated power

dissipation of that resistor in a particular circuit: this is mainly of concern in

power electronics applications. Resistors with higher power ratings are

physically larger and may require heat sinks. In a high-voltage circuit,

attention must sometimes be paid to the rated maximum working voltage of

the resistor.

Practical resistors have a series inductance and a small parallel capacitance;

these specifications can be important in high-frequency applications. In a low-

noise amplifier or pre-amp, the noise characteristics of a resistor may be an

issue. The unwanted inductance, excess noise, and temperature coefficient

are mainly dependent on the technology used in manufacturing the resistor.

They are not normally specified individually for a particular family of resistors

manufactured using a particular technology.[1] A family of discrete resistors is

also characterized according to its form factor, that is, the size of the device

and the position of its leads (or terminals) which is relevant in the practical

manufacturing of circuits using them.

The ohm (symbol: Ω) is the SI unit of electrical resistance, named after

George Simon Ohm. An ohm is equivalent to a volt per ampere. Since

resistors are specified and manufactured over a very large range of values,

the derived units of milliohm (1 mΩ = 10−3 Ω), kilo ohm (1 kΩ = 103 Ω), and

mega ohm (1 MΩ = 106 Ω) are also in common usage.


The reciprocal of resistance R is called conductance G = 1/R and is

measured in Siemens (SI unit), sometimes referred to as a mho. Hence,

Siemens is the reciprocal of an ohm: S = Ω − 1. Although the concept of

conductance is often used in circuit analysis, practical resistors are always

specified in terms of their resistance (ohms) rather than conductance.

The behavior of an ideal resistor is dictated by the relationship specified by

Ohm's law:

Ohm's law states that the voltage (V) across a resistor is proportional to the

current (I), where the constant of proportionality is the resistance (R).

Equivalently, Ohm's law can be stated:

This formulation states that the current (I) is proportional to the voltage (V)

and inversely proportional to the resistance (R). This is directly used in

practical computations. For example, if a 300 ohm resistor is attached across

the terminals of a 12 volt battery, then a current of 12 / 300 = 0.04 amperes

(or 40 mill amperes) occurs across that resistor.

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.

Christ Polytechnic Institute

3.3 Lights Functioning

Figure 3.1 light display.

The most formal terms for the lights on the signal mast seem to be crossing

flashers or flashing light units. The lights on the gate are simply called gate

lamps. A diagram for crossing lights in operation is shown in Figure 3 with a

total of eight lamps, as would be used in an installation like the one in

It might easily be imagined that the lights would be wired something like the


Functioning :




as would be used in an installation like the one in


Page 29




as would be used in an installation like the one in Figure.



left side of Figure, but that would be incorrect. Actually, they are wired as on

the right side of the diagram under "correct." The difference is that in the

correct scheme, the left and right lamps are basically connected in series to

begin with, and the flasher relay contacts merely short or bypasses half the

bulbs rather than supply them.

All the relays shown above reside in the relay cabinet or equipment housing

near the crossing with wires running out to the signals; they are not parts of

the signals themselves. In the correct wiring scheme, the three wires going

out to the lamps are here designated EN, EB, and E. (Another naming

scheme uses LL, RL, and FL, respectively.)

3.4 Gate Mechanisms:

A gate mechanism is very similar to a semaphore mechanism in that it has a

circuit controller, a motor that lifts the gate and resists its fall by the electric

retarder principle, and a normally energized hold-clear device (here

designated HC). See the article "How Semaphores Work" on this website. It is

very different, though, in two main ways: first, the gate motor actually drives

the gate down for about the first half (45°) of the descent, and retards only for

the final portion of the descent; second, the gate mechanism itself contains a

relay called the motor control relay (MCR). Although the gates are

counterweighted, they are required to be a little heavier than the

counterweights by moments. The gates would still fall the entire distance by

gravity, albeit more slowly at first, without the motor's assistance.


Figure 3.2 Old gate mechanisms.

Figure an older style WRRS crossing gate mechanism with case open.The

purpose of the MCR is to change the connections to the motor, since it drives

both up and down; to reverse its supply polarity and select the appropriate

circuit controller segments for the up or down movement. Generally, it is

energized when the gate is supposed to rise and de-energized when the gate

is supposed to fall.


The control of the gate, then, generally centers on the status of a normally

energized "UP" signal from which the supply for the coils of the HC and MCR

are derived. However, gate mechanism wirings may vary with the particular

design, and the individual supplies of the HC and MCR may be broken by the

circuit controller in the gate mechanism when they are not needed.

Specifically, the MCR is energized when the gate is rising to the up position,

but the circuit controller may or may not cut the MCR out after it gets there.

Conversely, the HC does not need to be energized until the gate is fully up,

and it may not be energized until it is cut in at that time by the circuit

controller.

Figure 3.3 Modern gate mechanisms.

Sometimes the term "power down" is used in connection with crossing gates.

This refers to the situation where the motor drives the gate down under


power, as intended. The term is not used in the modern sense where a

machine conserves energy by "going to sleep." A less confusing synonym is

"motor down."

3.5 Railway Grade Crossing Flasher Operation:

Figure 3.4 Gate operation


• When a train traveling in either direction covers one of the "START"

sensors, the crossing signals will start to flash.

• The signals will remain ON until approximately two seconds after the

last car has passed completely through the crossing, uncovering both

of the "STOP" sensors.

• As the train leaves the protected section of track, the "DISABLE"

sensors prevent the flashers from being turned ON again by

deactivating the "START" sensors.

• The "START" sensors are reactivated approximately 5 seconds after

the "DISABLE" sensors have been uncovered.

• Sensors 1 or 6 must be covered before sensors 2 or 5, depending on

the direction of travel, or the signals will not start. Sensors 2 and 5

disable sensors 1 and 6.

• Variable resistor R15 sets the flashing rate of the crossing signals.

• The next diagram show the changes in the output terminals of the

crossing circuit as a train passes through the protected section of

track.


The next diagram show the changes in the output terminals of the crossing

circuit as a train passes through the protected section of track

Figure 3.5 Gate crossing circuit operation.

3.6 Grade Crossing Circuit Operation Notes:

The flashers will turn OFF if a train enters and then backs out of the

crossing. The circuit is ready for the next train in either direction

approximately five seconds after the "DISABLE" sensors are uncovered. If

the departing train is still covering a "START" sensor after this time the

flashers will turn on again.

Manual controls can start or stop the flashers as desired. The START

push button could be replaced by a toggle switch in order to keep the

flashers activated during switching operations. Normal room lighting is

used to detect the trains. If night operation is needed the circuit can be

controlled by other circuits or by providing infrared light for the sensors.


The circuit is designed to use phototransistors but can also be controlled

by CdS photocells by changing the values of resistors R1, R2 and R3.The

Crossing Circuit requires a regulated 12 volt power supply. The current

draw is about 3 milliamps when the flashers are OFF and about 35

milliamps when they are ON.

Crossing gates and bells can be controlled buy using the Multitask

terminal as an output to control these devices. The MultiTrack terminal is

also used to connect the circuit boards together for crossings with two or

more tracks.

3.7 Function of stepper motor

3.6 construction of stepper motor

Frame 1: The top electromagnet (1) is turned on, attracting the nearest teeth of the gear-shaped iron rotor. With the teeth aligned to electromagnet 1, they will be slightly offset from electromagnet 2. Frame 2: The top electromagnet (1) is turned off, and the right electromagnet (2) is energized, pulling the teeth into alignment with it. This results in a rotation of 3.6° in this example. Frame 3: The bottom electromagnet (3) is energized; another 3.6° rotation occurs. Frame 4: The left electromagnet (4) is energized, rotating again by 3.6°. When the top electromagnet (1) is again enabled, the rotor will have rotated by one tooth position; since there are 25 teeth, it will take 100 steps to make a full rotation in this example.

A stepper motor (or step motor) is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor's position can then be commanded to move and hold at one of these steps without any


feedback sensor (an open-loop controller), as long as the motor is carefully sized to the application.

Switched reluctance motors are very large stepping motors with a reduced pole count, and generally are closed-loop commutated.

3.7 Front view of stepper motor

DC brush motors rotate coninuously when voltage is applied to their terminals. Stepper motors, on the other hand, effectively have multiple "toothed" electromagnets arranged around a central gear-shaped piece of iron. The electromagnets are energized by an external control circuit, such as a microcontroller. To make the motor shaft turn, first, one electromagnet is given power, which makes the gear's teeth magnetically attracted to the electromagnet's teeth. When the gear's teeth are aligned to the first electromagnet, they are slightly offset from the next electromagnet. So when the next electromagnet is turned on and the first is turned off, the gear rotates slightly to align with the next one, and from there the process is repeated. Each of those slight rotations is called a "step", with an integer number of steps making a full rotation. In that way, the motor can be turned by a precise angle.

3.7.1 Stepper motor characteristics

• Stepper motors are constant power devices.

• As motor speed increases, torque decreases. Most motors exhibit maximum torque when stationary, however the torque of a motor when stationary (holding torque) defines the ability of the motor to maintain a desired position while under external load. The torque curve may be extended by using current limiting drivers and increasing the driving voltage (sometimes referred to as a 'chopper' circuit; there are several off the shelf driver chips capable of doing this in a simple manner).

• Steppers exhibit more vibration than other motor types, as the discrete step tends to snap the rotor from one position to another (called a detent). The vibration makes stepper motors noisier than DC motors. This vibration can become very bad at some speeds and can cause the motor to lose torque or lose direction. This is because the rotor is


being held in a magnetic field which behaves like a spring. On each step the rotor overshoots and bounces back and forth, "ringing" at its resonant frequency. If the stepping frequency matches the resonant frequency then the ringing increases and the motor loses synchronism, resulting in positional error or a change in direction. At worst there is a total loss of control and holding torque so the motor is easily overcome by the load and spins almost freely. The effect can be mitigated by accelerating quickly through the problem speeds range, physically damping (frictional damping) the system, or using a micro-stepping driver. Motors with a greater number of phases also exhibit smoother operation than those with fewer phases (this can also be achieved through the use of a micro-stepping driver).

• Stepper motors with higher inductance coils provide greater torque at low speeds and lower torque at high speeds compared to stepper motors with lower inductance coils.

3.7.2 Open-loop versus closed-loop commutation

Steppers are generally commutated (electrically switched) using "open loop" electronics, i.e. the driver has no feedback on where the rotor actually is. Stepper motor systems must thus generally be over engineered, especially if the load inertia is high, or there is widely varying load, so that there is no possibility that the motor will lose steps. This has often caused the system designer to consider the trade-offs between a closely sized but expensive servomechanism system and an oversized but relatively cheap stepper.

A new development in stepper control is to incorporate a rotor position feedback (e.g. a rotary encoder or resolver), so that the commutation can be made optimal for torque generation according to actual rotor position. This turns the stepper motor into a high pole count brushless servo motor, with exceptional low speed torque and position resolution. An advance on this technique is to normally run the motor in open loop mode, and only enter closed loop mode if the rotor position error becomes too large — this will allow the system to avoid hunting or oscillating, a common servo problem.

3.7.3 Types:

There are four main types of stepper motors:[1]

1. Permanent magnet stepper (can be subdivided in to 'tin-can' and 'hybrid', tin-can being a cheaper product, and hybrid with higher quality bearings, smaller step angle, higher power density)

2. Hybrid synchronous stepper 3. Variable reluctance stepper


4. Lavet type stepping motor

Permanent magnet motors use a permanent magnet (PM) in the rotor and operate on the attraction or repulsion between the rotor PM and the stator electromagnets. Variable reluctance (VR) motors have a plain iron rotor and operate based on the principle that minimum reluctance occurs with minimum gap, hence the rotor points are attracted toward the stator magnet poles. Hybrid stepper motors are named because they use a combination of PM and VR techniques to achieve maximum power in a small package size.

3.12.4 Stepper motor drive circuits

3.8 Stepper motor with drive circuit

Stepper motor performance is strongly dependent on the drive circuit. Torque curves may be extended to greater speeds if the stator poles can be reversed more quickly, the limiting factor being the winding inductance. To overcome the inductance and switch the windings quickly, one must increase the drive voltage. This leads further to the necessity of limiting the current that these high voltages may otherwise induce.

3.7.5 Phase current waveforms

A stepper motor is a polyphase AC synchronous motor (see Theory below), and it is ideally driven by sinusoidal current. A full step waveform is a gross approximation of a sinusoid, and is the reason why the motor exhibits so much vibration. Various drive techniques have been developed to better approximate a sinusoidal drive waveform: these are half stepping and microstepping.


3.9 Different drive modes showing coil current on a 4motor

3.7.6 Theory

A step motor can be viewed as a synchronous AC motor with the number of poles (on both rotor and stator) increased, taking care that tcommon denominator. Additionally, soft magnetic material with many teeth on the rotor and stator cheaply multiplies the number of poles (reluctance motor). Modern steppers are of hybrid design, having both permanent magnets and soft iron cores.

To achieve full rated torque, the coils in a stepper motor must reach their full rated current during each step. Winding inductance and reverse EMF generated by a moving rotor tend to resist changes in drive current, so that as the motor speeds up, less and less time is spent at full current reducing motor torque. As speeds further increase,the rated value, and eventually the motor will cease to produce torque.

3.7.7 Stepper motor ratings and specifications

Stepper motors nameplates typically give only the winding current and occasionally the voltage and winding rproduce the rated winding current at DC: but this is mostly a meaningless rating, as all modern drivers are current limiting and the drive voltages greatly exceed the motor rated voltage.


Different drive modes showing coil current on a 4-phase unipolar stepper

A step motor can be viewed as a synchronous AC motor with the number of poles (on both rotor and stator) increased, taking care that tcommon denominator. Additionally, soft magnetic material with many teeth on the rotor and stator cheaply multiplies the number of poles (reluctance motor). Modern steppers are of hybrid design, having both permanent magnets and

To achieve full rated torque, the coils in a stepper motor must reach their full during each step. Winding inductance and reverse EMF

generated by a moving rotor tend to resist changes in drive current, so that as the motor speeds up, less and less time is spent at full current reducing motor torque. As speeds further increase, the current will not reach the rated value, and eventually the motor will cease to produce torque.

Stepper motor ratings and specifications

Stepper motors nameplates typically give only the winding current and occasionally the voltage and winding resistance. The rated produce the rated winding current at DC: but this is mostly a meaningless rating, as all modern drivers are current limiting and the drive voltages greatly

ceed the motor rated voltage.

Page 40

phase unipolar stepper

A step motor can be viewed as a synchronous AC motor with the number of poles (on both rotor and stator) increased, taking care that they have no common denominator. Additionally, soft magnetic material with many teeth on the rotor and stator cheaply multiplies the number of poles (reluctance motor). Modern steppers are of hybrid design, having both permanent magnets and

To achieve full rated torque, the coils in a stepper motor must reach their full during each step. Winding inductance and reverse EMF

generated by a moving rotor tend to resist changes in drive current, so that as the motor speeds up, less and less time is spent at full current — thus

the current will not reach the rated value, and eventually the motor will cease to produce torque.

Stepper motors nameplates typically give only the winding current and esistance. The rated voltage will

produce the rated winding current at DC: but this is mostly a meaningless rating, as all modern drivers are current limiting and the drive voltages greatly


A stepper's low speed torque will vary directly with current. How quickly the torque falls off at faster speeds depends on the winding inductance and the drive circuitry it is attached to, especially the driving voltage.

Steppers should be sized according to published torque curve, which is specified by the manufacturer at particular drive voltages or using their own drive circuitry.

3.7.8 Applications

Computer-controlled stepper motors are a type of motion-control positioning system. They are typically digitally controlled as part of an open loop system for use in holding or positioning applications.

In the field of lasers and optics they are frequently used in precision positioning equipment such as linear actuators, linear stages, rotation stages, goniometers, and mirror mounts. Other uses are in packaging machinery, and positioning of valve pilot stages for fluid control systems.

Commercially, stepper motors are used in floppy disk drives, flatbed scanners, computer printers, plotters, slot machines, image scanners, compact disc drives, intelligent lighting and many more devices.


3.8 BC-547

3.10 overview , symbol , pin configuration of BC-547

BC547 is an NPN bi-polar junction transistor. A transistor, stands for transfer of resistance, is commonly used to amplify current. A small current at its base controls a larger current at collector & emitter terminals.


BC547 is mainly used for amplification and switching purposes. It has a maximum current gain of 800. Its equivalent transistors are BC548 and BC549. The transistor terminals require a fixed DC voltage to operate in the desired region of its characteristic curves. This is known as the biasing. For amplification applications, the transistor is biased such that it is partly on for all input conditions. The input signal at base is amplified and taken at the emitter. BC547 is used in common emitter configuration for amplifiers. The voltage divider is the commonly used biasing mode. For switching applications, transistor is biased so that it remains fully on if there is a signal at its base. In the absence of base signal, it gets completely off. 3.8.1 Pin Diagram:

3.11 Pin diagram


3.8.2 Description

The BC548 is a general purpose epitaxial silicon NPN bipolar junction transistor found commonly in European electronic equipment. The part number is assigned by Pro Electron, which allows many manufacturers to offer electrically and physically interchangeable parts under one identification. The BC548 is commonly available in European Union countries. It is often the first type of bipolar transistor young hobbyists encounter, and is often featured in circuit diagrams and designs published in hobby electronics magazines.

If the plastic TO-92 package is held in front of one's face with the flat side facing toward you and the leads downward, (see picture) the order of the leads, from left to right is collector, base, emitter.

3.8.3 Specifications

Devices registered to this Pro Electron number must have minimum performance characteristics.

Breakdown voltage, with base open VCBO = 30 V Rated collector current IC = 100 mA Rated total power dissipation Ptotal = 500 mW Transition frequency (gain-bandwidth product) ft = 300 MHz


3.9 74LS-04/08

3.9.1 Internal construction and Pin configuration

3.12 internal construction and pin configuration


3.10 ULN2003 ULN2003 is a high voltage and high current Darlington array IC. It

contains seven open collector darlington pairs with common emitters. A darlington pair is an arrangement of two bipolar transistors.

ULN2003 belongs to the family of ULN200X series of ICs. Different versions of this family interface to different logic families. ULN2003 is for 5V TTL, CMOS logic devices. These ICs are used when driving a wide range of loads and are used as relay drivers, display drivers, line drivers etc. ULN2003 is also commonly used while driving Stepper Motors. Refer Stepper Motor interfacing using ULN2003.

Each channel or darlington pair in ULN2003 is rated at 500mA and can withstand peak current of 600mA. The inputs and outputs are provided opposite to each other in the pin layout. Each driver also contains a suppression diode to dissipate voltage spikes while driving inductive loads. The schematic for each driver is given below:

3.13 Internal circuit


3.10.1 Pin Diagram:

3.10.2 Pin Discription


Chapter: 4

Detailed of Microcontroller

4.1 89C51:

AT89C51 is a 40 pin dip micro controller, can be divided in to four ports, it is

driven by 5v supply. In this project Atmel 89c51 Micro controller Integrated

Chip plays the main role. The program for this project is embedded in this

Micro controller Integrated Chip and interfaced to all the peripherals. The

timer program is inside the Micro controller IC to maintain all the functions as

per the scheduled time. The Light dependent resistor is interfaced to Atmel

89c51 Micro controller to display the message, stepper motors are used for

the purpose of gate control interfaced with current drivers chip ULN2003.

ULN2003 is a current driver chip used for supply control to the stepper motor;

it is a 16 pin dip.

Here a stepper motor is used for controlling the gates. A stepper motor is a

widely used device that translates electrical pulses into mechanical

movement. They function as their name suggests - they step a little bit at a

time. Steppers motors simply respond to a clock signal. They have several

windings which need to be energized in the correct sequence before the

motorâ„¢s shaft will rotate. Reversing the order of the sequence will cause the

motor to rotate the other way. This project work aims at the design,

development, fabrication and testing of working model entitled Automatic

Railway Gate Controller.


It is basically related to Radio communication and signaling system. An

Automatic Railway gate controller is unique in which the railway gate is closed

and opened or operated by the Train itself by eliminating the chances of

human errors. The largest public sector in India is the Railways. The network

of Indian Railways covering the length and breath of Indian Railways covering

the length and breath of our country is divided into nine Railway zones for

operational convenience. The railway tracks criss-cross the state Highways

and of course village road along their own length. The points or places where

the Railway track crosses the road are called level crossings. Level crossings

cannot be used simultaneously both by road traffic and trains, as this result in


4.2 89C51 MICTROCONTROLLER:

4.2.1 Description:

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 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.


4.2.2 features:

• 4Kbytes of Flash memory, 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.


4.3 Architecture Block diagram

Figure 4.1 Architecture of 8051.


4.4 PIN DISCRIPTION

Figure4.2 pin diagram of 8051.

VCC:Supply voltage.

GND: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 20th 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.


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.




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 [at] 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 [at] 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.





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.

RST:Reset 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.

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.

XTAL1: Input to the inverting oscillator amplifier and input to the internal clock

operating.

XTAL2: It is the output from the inverting oscillator amplifier.


Chapter 5:

Concept of track

5.1 Overview & Introduction

This small line follower robot, was designed to be easily built at home without

any special equipment, and using a minimum number of mechanical parts.

You wont need more than 2 small motors, 2 free wheels and a piece of pcb

(to hold the micro-controller, the motors driver and the line sensor) and

sure..your soldering iron.

The main trick making this design simple and affordable, is that the robot's

chassis is actually the main board of the robot, where some supports for

the wheels - also made of small parts of copper boards - are soldered to it. All

themotors, and the skids are mounted on the main PCB. For an electronics

hobbyist, PCB manufacturing is a skill that will be learnt sooner or later, so

this design lets you use your experience in PCB manufacturing to design a

high precision chassis for your robot.

5.1.1 How to sense a black line ?

The sensors used for the project are Reflective Object Sensors, 0PB710F

that are already ready in the Electronic Lab. The single sensor consists of an

infrared emitting diode and a NPN Darlington phototransistor. When a light

emitted from the diode is reflected off an object and back into the

phototransistor, output current is produced, depending on the amount of

infrared light, which triggers the base current of the phototransistor. In my

case, the amount of light reflected off a black line is much less than that of a

white background, so we can detect the black line somehow by measuring

the current. (This current is converted to voltage.)


5.1.2 How to control a DC motor ?

Instead of applying a constant voltage across a DC motor, we repeat

switching on and off the motor with a fixed voltage (Vcc) applied to the motor.

This is done by sending a train of PWM (Pulse Width Modulation) pulses to a

power MOSFET in order to turn it on and off. Then, the motor sees the

average voltage while it depends on duty cycle of PWM pulses. The speed of

rotation is proportion to this average voltage. By PWM method, it’s easier to

control the DC motor than by directly controlling the voltage across it. All we

have to do is to modulate pulse width, in order words, a duty cycle. Also, a

power MOSFET consumes only negligible power in switching.

Figure5.1 shows a 3D graphical representation of the robot, where different

parts can be clearly identified according to the following table:


Table 1.2 Parts lists of line follower

Part Description

1 The base of the robot, also the main PCB.

2 Front skid

3 Free Wheel, shaped as a pulley

4 Plastic pulley

5 Battery holder

6 Pipe clamp use to hold the motors

7 Ni-Cd 7.2V battery pack

8 1200 rpm 6V motor

5.1.3 Component Values:

• R1=6K, R2=1K, R3=20K, R4=10, R5=82, R6=5K(variable), R7=1K.

• C1=1µF, C2=0.1µF, C3=0.1µF.

It is clear that the drive train of this robot is differential type, meaning the two

rear wheels are responsible of moving the robot forward and backward, but

are also used to turn the robot in any required direction depending the

difference of speed between the right and left wheels.

The first thing that need some explanation is the fact that there are only 2

wheels, Well, while not being the best thing to do, a caster wheel can

sometimes be replaced with a skid, when the robot weight and size are not

important, and when the robot is designed for indoor environment, where the

robot can move on relatively smooth surfaces, where friction wont be a

seriousproblem.


It may seem strange that the battery was placed on the top of the robot, and it

is actually an important mistake, as a battery at that height totally destabilize

the robot because it raises the center of gravity, increasing the moment of

inertia. For more information about robot stability and moment of inertial

read this tutorial. For this size of robot, a smaller li-ion battery, placed beneath

the robot, would have given much better results.

5.2 The Chassis :

As you may have notices, the main board has a dual function: Electrical and

mechanical. From the mechanical point of view, this boards is the chassis of

the robot, where the motors, the wheels and the electronics are mounted. You

can see in figure 2.A that the holes to be used to fix the motors are present on

the layout, as well as the holes to mount the front and read skids. Using PCB

layout software to design the chassis, as well as PCB techniques to

manufacture it, gives a lot of accuracy which is very important for the

mechanical system to work correctly. You can see that the line sensor is

integrated in that same main board. It's important that the line sensor be as

far as possible from the drive wheels in a differential steering robot. This

principle is explained in detail in this article about line tracking sensors and

algorithms.

There are many kinds of materials from which the copper plated boards are

made. Try to choose a relatively thick one for this chassis, to be able to bear

the weight of the motors and the batteries, all concentrated in four points,

where the screws are fixed.


5.2 PCB interfacing diagram of line-follower circuit


5.3 picture image of the line follower robot


5.3 Motors and power transmission

5.4 construction and picture image of stepper motor


5.3.1 Introduction

• This is a 60 RPM low cost single shaft DC geared motor. It is most suitable for light weight robot requiring small power. This motor can be used with 69mm Diameter Wheel for Plastic Gear Motors and 87mm Diameter Multipurpose Wheel for Plastic Gear Motors. For robot with Tank Tracks use Tank Track Links with 87mm Diameter Multipurpose Wheel for Plastic Gear Motors.

• Drive shaft has clutch for non continuous protection from overload which protects gears from the sudden overload. Motor runs smoothly from 2V to 12V and gives wide range of RPM, and torque. Table below gives fairly good idea of the motor’s performance in terms of RPM, no load current as a function of voltage and stall torque, stall current as a function of voltage...

5.3.2 Specifications

• RPM: 60 at 12V • Voltage: 2V to 12V • Current: No load current and stall current are function of voltage. Fore

more data refer below tables • Clutch for non continuous protection from overload conditions • Motor weight: 30gms • Matched wheels:

o 69mm Diameter Wheel for Plastic Gear Motors o 87mm Diameter Multipurpose Wheel for Plastic Gear Motors

5.5 Internals of the Single Shaft Plastic Gear Motor

• The motors, which are DC motors originally made for cassette players, are

cylindrical and thus very difficult to mount and firmly fix to a chassis.

• So this unique technique was used, which is to use pipe clamps, originally

used to mount water pipes all along the walls of buildings (see figure 4.A).

Those pipe clamps are easily available for all the diameters you can imagine,

at least you will easily find a pipe clamp whose diameter fits the diameter of

your motor.


• You can notice a small black plastic pulley fixed at the end of the motor's

shaft, which will be then used to transmit power to the wheels using a belt.

This small pulley can be found from the same store where you can buy those

motors, the rubber belts, as well as all kind of accessories of cassette

players.

• When the motors and the pipe clamps are assembled as shown in figure 4.A,

they can finally be easily inserted in their place in the chassis (main board),

then all you need is to add a rubber belt to obtain the transmission system

shown in figure 4B.

• This pulley / belt assembly acts exactly as as the gearbox added to a DC

motors to reduce speed and increase torque.

• Depending on the size of the belt you have, you can adjust its tension by

adjusting the height of the motor itself, which can easily be done by changing

the position of the nuts on the screws holding the motors to the PCB. The

optimum tension in the belt can be easily found by trial and error.

5.4 The wheels

The wheels in this design also have a dual function, they act as a wheel and

as a pulley, with which power is transmitter from another smaller pulley using

a rubber belt.

Those wheels were originally free wheels used in sliding doors and windows.

they are small, cheap and can bear very important loads. They have been

modified as shown in figure 3.A so that they can be fixed to the chassis using

those 4mm standard screws. Note that the wheel is still free to rotate around


the axe of the screw, so the only way to transmit power to that wheel will be

though a belt directly mounted on it, as you shall see later.

You can also notice that the wheels are mounted on the chassis using small

rectangular piecesof copper board welded the main board using a regular

soldering iron, and where the center of the wheel is etched on it for maximum

accuracy, this way, both the right and left wheels are at the exact same

height.

You can also notice that another small piece of PCB is added to cary any

eventual shear stress on the main part holding the wheel. (see figure 3.B and

3.C)

Figure 5.6 Wheels


5.5 Circuit description:

Being powered from a 7.2V battery, the regulator U3 provides regulated 5V

for the microcontroller and for the logic gates of the motor driver. You can add

a capacitor between the output of the regulator and the ground to absorb the

noise caused by the presence of motors in the system, but I didn't use any,

and didn't face any problems regarding this issue.When the switch SW1 is

switched OFF, the battery can be charged using the jack J2.

The line sensor is composed of 4 cells, and is based on the IR

emission/reception technique described in this tutorial. D1 to D4 are IR LEDs

used as receivers, D9 to D12 are also IR LEDs, but used as emitters this

time. The output of the line sensor is directly fed from the Op Amps to the

microcontroller. Only two outputs are connected to the LEDs D7 and D8,

giving a direct indication of the output of the sensor, making the calibration

process very easy through the

potentiometer R6. For more information about line sensors, check this tutorial

specially dedicated to line tracking sensors and algorithms

Figure 5.B shows the 4 emitter and 4 receiver LEDs at the front of the robot.

Note that this is the optimal position of the line sensor, as you can see in the

tutorial above about line sensors.It is also clear that they are mounted on the

copper side of the board, even through they are regular LEDs (not SMT type).

The Leads of the LEDs are used to adjust the height of the sensor from the

ground. 10 to 20 millimeters proved to be a fair height for the sensor to

function properly.

The connections around the microcontroller are standard in most of our 8051

based projects, they are the crystal resonator along with the two decoupling

capacitors, the debouncing circuit attached to the reset pin, and the ISP (In

system programming). Upon switching on the robot, The software loaded on

the microcontroller simply directs the robot to the line, using standard line

following algorithms described in the following article. You can download the


C code along with the HEX file to be loaded into the microcontroller at the end

of this article.

The two motors of the robot are driven using the reliable L293D Motor driver

IC, the motors are connected to the wire connections W3, W4, W5, and W6.

Being controlled by the microcontroller, the speed of the motors can be easily

adjusted using PWM pulses fed to the motor through the Enable PINs of the

driver. Note that each channel has it's own independent Enable PIN, making it

very easy to control the speed of two different motors simultaneously.

5.6 Operating the L293D motor driver

Using the L293D motor driver, makes controlling a motor as simple as

operating a buffer gate IC. It totally isolates the TTL logic inputs from the high

current outputs.Puttinga logic 1 on the pin In1 will makeOut1 pin go to Vpower

(36 Volts MAX.), while a logic 0 will make it go to 0V

Each couple of channels can be enabled and disabled using E1 and E2 pins.

When disabled a channel provide a very high impedance (resistance) to the

motor, exactly as if the motor wasn't connected to the driver IC at all, which

makes this feature very useful for PWM speed control.

One way is to use 2 channels to builda bi-directional motor driver, another

way is to use 1 channel per motor, building a unidirectional driver. In this

project, we will be using the 4 channels to drive the 2 motors in both

directions. To get more specific information on this very useful IC


Figure 5.7 L293D Motor driver.


5.7 Operation of LM324

LM324 is a 14pin IC consisting of four independent operational

amplifiers (op-amps) compensated in a single package. Op-amps are high

gain electronic voltage amplifier with differential input and, usually, a single-

ended output. The output voltage is many times higher than the voltage

difference between input terminals of an op-amp.

These op-amps are operated by a single power supply LM324 and

need for a dual supply is eliminated. They can be used as amplifiers,

comparators, oscillators, rectifiers etc. The conventional op-amp applications

can be more easily implemented with LM324.

5.7.1 Pin Diagram

5.8 pin configuration


5.7.2 Pin Discription

Pin No Function Name 1 Output of 1st comparator Output 1 2 Inverting input of 1st comparator Input 1- 3 Non-inverting input of 1st comparator Input 1+ 4 Supply voltage; 5V (up to 32V) Vcc 5 Non-inverting input of 2nd comparator Input 2+ 6 Inverting input of 2nd comparator Input 2- 7 Output of 2nd comparator Output 2 8 Output of 3rd comparator Output 3 9 Inverting input of 3rd comparator Input 3- 10 Non-inverting input of 3rd comparator Input 3+ 11 Ground (0V) Ground 12 Non-inverting input of 4th comparator Input 4+ 13 Inverting input of 4th comparator Input 4- 14 Output of 4th comparator Output 4

5.8 Sensors

There are 7 pairs of the sensors. The sensor consists of the 7 pair of

the IR led and Photodiode. It continuously sense the black line and follow the

path.

5.8.1 Photo-Diode:

• Three Si and one Ge (bottom) photodiodes


5.9Symbol for photodiode.

A photodiode is a type of either current or voltagecommon, traditional solar cellarea photodiode.

Photodiodes are similar to regular they may be either exposed (to detect with a window or optical fiberpart of the device. Many diodes designed for use specifically as a photodiode use a PIN junction rather than a response. A photodiode is designed to operate in

5.8.2 Principle of operation

A photodiode is a sufficient energy strikes the diode, it excites an electron, thereby creating a free electron (and a positively charged electron known as the inner photoelectric effectjunction's depletion regionare swept from the junction by the builtholes move toward the photocurrent is produced. This photocurrent is the sum of both the dcurrent (without light) and the light current, so the dark current must be minimized to enhance the sensitivity of the device.


Symbol for photodiode.

is a type of photodetector capable of converting voltage, depending upon the mode of operation.

solar cell used to generate electric solar power

Photodiodes are similar to regular semiconductor diodesthey may be either exposed (to detect vacuum UV or X-rays) or packaged

ptical fiber connection to allow light to reach the sensitive part of the device. Many diodes designed for use specifically as a photodiode

rather than a p-n junction, to increase the speed of response. A photodiode is designed to operate in reverse bias.

Principle of operation

A photodiode is a p-n junction or PIN structure. When a sufficient energy strikes the diode, it excites an electron, thereby creating a

(and a positively charged electron hole). This mechanism is also photoelectric effect. If the absorption occurs in the

depletion region, or one diffusion length away from it, these carriers are swept from the junction by the built-in field of the depletion region. Thus holes move toward the anode, and electrons toward the cathode

is produced. This photocurrent is the sum of both the dcurrent (without light) and the light current, so the dark current must be minimized to enhance the sensitivity of the device.

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capable of converting light into , depending upon the mode of operation.[1] The

solar power is a large

diodes except that ) or packaged

connection to allow light to reach the sensitive part of the device. Many diodes designed for use specifically as a photodiode

, to increase the speed of

. When a photon of sufficient energy strikes the diode, it excites an electron, thereby creating a

). This mechanism is also . If the absorption occurs in the

, or one diffusion length away from it, these carriers in field of the depletion region. Thus

cathode, and a is produced. This photocurrent is the sum of both the dark

current (without light) and the light current, so the dark current must be


5.8.3 Other modes of operation

Avalanche photodiodes have a similar structure to regular photodiodes, but they are operated with much higher reverse bias. This allows each photo-generated carrier to be multiplied by avalanche breakdown, resulting in internal gain within the photodiode, which increases the effective responsivity of the device.

A phototransistor is in essence a bipolar transistor encased in a transparent case so that light can reach the base-collector junction. It was invented by Dr. John N. Shive (more famous for his wave machine) at Bell Labs in 1948,[5]:205 but it wasn't announced until 1950.[6] The electrons that are generated by photons in the base-collector junction are injected into the base, and this photodiode current is amplified by the transistor's current gain β (or hfe). If the emitter is left unconnected, the phototransistor becomes a photodiode. While phototransistors have a higher responsivity for light they are not able to detect low levels of light any better than photodiodes.[citation

needed] Phototransistors also have significantly longer response times.

5.8.4 Materials

The material used to make a photodiode is critical to defining its properties, because only photons with sufficient energy to excite electrons across the material's bandgap will produce significant photocurrents.

Materials commonly used to produce photodiodes include

Material Electromagnetic spectrum wavelength range (nm)

Silicon 190–1100 Germanium 400–1700 Indium gallium arsenide 800–2600 Lead(II) sulfide <1000–3500

Because of their greater bandgap, silicon-based photodiodes generate less noise than germanium-based photodiodes.


5.8.5 Features

5.10 Response of a silicon photo diode vs wavelength of the incident light

• Critical performance parameters of a photodiode include:

Responsivity: The ratio of generated photocurrent to in

typically expressed in responsivity may also be expressed as a ratio of the number of photogenerated carriers to incident photons and thus a unitless quantity.

Dark current:

The current through the photodiode in the absence of light, when it is operated in photoconductive mode. The dark current includes photocurrent generated by background radiation and the saturation current of the semiconduaccounted for by accurate optical power measurement, and it is also a source of when a photodiode is used in an optical communication system.

Noise-equivalent power

(NEP) The minimum input optical power to generate photocurrent, equal to the rms noise current in a 1 NEP is essentially the minimum detectable power. The related characteristic "detectivity" (D) is the inverse of NEP, 1/NEP.

There is also the "divided by the sqaure root of the ar

). Although it is traditional to give (


Response of a silicon photo diode vs wavelength of the incident

Critical performance parameters of a photodiode include:

The ratio of generated photocurrent to incident light power, typically expressed in A/W when used in photoconductive mode. The responsivity may also be expressed as a Quantum efficiencyratio of the number of photogenerated carriers to incident photons and thus a unitless quantity.

The current through the photodiode in the absence of light, when it is operated in photoconductive mode. The dark current includes photocurrent generated by background radiation and the saturation current of the semiconductor junction. Dark current must be accounted for by calibration if a photodiode is used to make an accurate optical power measurement, and it is also a source of when a photodiode is used in an optical communication system.

alent power: (NEP) The minimum input optical power to generate

photocurrent, equal to the rms noise current in a 1 hertzNEP is essentially the minimum detectable power. The related

racteristic "detectivity" (D) is the inverse of NEP, 1/NEP.

There is also the "specific detectivity" ( ) which is the detectivity divided by the sqaure root of the area (A) of the photodetector, (

). Although it is traditional to give ( ) in many catalogues as a

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Response of a silicon photo diode vs wavelength of the incident

cident light power, when used in photoconductive mode. The

Quantum efficiency, or the ratio of the number of photogenerated carriers to incident photons and

The current through the photodiode in the absence of light, when it is operated in photoconductive mode. The dark current includes photocurrent generated by background radiation and the

ctor junction. Dark current must be if a photodiode is used to make an

accurate optical power measurement, and it is also a source of noise when a photodiode is used in an optical communication system.

(NEP) The minimum input optical power to generate hertz bandwidth.

NEP is essentially the minimum detectable power. The related racteristic "detectivity" (D) is the inverse of NEP, 1/NEP.

) which is the detectivity ea (A) of the photodetector, (

) in many catalogues as a


measure of the diode's quality, in practice, it is hardly ever the key paramater. It is not clear why it was ever used.

When a photodiode is used in an optical communication system, these parameters contribute to the sensitivity of the optical receiver, which is the minimum input power required for the receiver to achieve a specified bit error rate.

5.8.6 Applications

• P-N photodiodes are used in similar applications to other photodetectors, such as photoconductors, charge-coupled devices, and photomultiplier tubes. They may be used to generate an output which is dependent upon the illumination (analog; for measurement and the like), or to change the state of circuitry (digital; either for control and switching, or digital signal processing).

• Photodiodes are used in consumer electronics devices such as compact disc players, smoke detectors, and the receivers for infrared remote control devices used to control equipment from televisions to air conditioners. For many applications either photodiodes or photoconductors may be used. Either type of photosensor may be used for light measurement, as in camera light meters, or to respond to light levels, as in switching on street lighting after dark.

• Photosensors of all types may be used to respond to incident light, or to a source of light which is part of the same circuit or system. A photodiode is often combined into a single component with an emitter of light, usually a light-emitting diode (LED), either to detect the presence of a mechanical obstruction to the beam (slotted optical switch), or to couple two digital or analog circuits while maintaining extremely high electrical isolation between them, often for safety (optocoupler).

• Photodiodes are often used for accurate measurement of light intensity in science and industry. They generally have a more linear response than photoconductors.

• They are also widely used in various medical applications, such as detectors for computed tomography (coupled with scintillators), instruments to analyze samples (immunoassay), and pulse oximeters.

• PIN diodes are much faster and more sensitive than p-n junction diodes, and hence are often used for optical communications and in lighting regulation.

• P-N photodiodes are not used to measure extremely low light intensities. Instead, if high sensitivity is needed, avalanche photodiodes, intensified charge-coupled devices or photomultiplier tubes are used for applications such as astronomy, spectroscopy, night vision equipment and laser rangefinding.


5.8.7 Photodiode array

A one-dimensional array of hundreds or thousands of photodiodes can be used as a position sensoradvantage of photodiode arrays (PDAs) is that they allow for high speed parallel read out since the driving electronics may not be built in like a traditional CMOS or CCD

5.8.8 Obstacle Detection Using IR

I have tested my ir-led-surfaces they are just awesome but not intelligent (unlike TSOPs) but you can make them intelligent using your programming skills and some thinking with correct technique they can detect presenccase) up to 50cm (*conditions applied ) even in the presence of very iremitting audience.

5.11 working of Ir

in words : Take a reading with IRIR-led is ON. This way you get reading because of IRassumes that the neighbouring IR conditions remains unchanged in between two readings. 5.8.9 Circuit :

• Atmega8 • IR-led-Photodiode• reflecting surface


Photodiode array

dimensional array of hundreds or thousands of photodiodes can position sensor, for example as part of an angle sensor

advantage of photodiode arrays (PDAs) is that they allow for high speed parallel read out since the driving electronics may not be built in like a

CCD sensor.

Obstacle Detection Using IR -led-Photodiode

-photodiode pair for more than 30 different lights and surfaces they are just awesome but not intelligent (unlike TSOPs) but you can make them intelligent using your programming skills and some thinking with correct technique they can detect presence of white surface (paper in my case) up to 50cm (*conditions applied ) even in the presence of very ir

5.11 working of Ir

in words : Take a reading with IR-led OFF and subtract it from reading when s way you get reading because of IR-led only. This principle

assumes that the neighbouring IR conditions remains unchanged in between two readings.

Photodiode reflecting surface

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dimensional array of hundreds or thousands of photodiodes can angle sensor.[9] One

advantage of photodiode arrays (PDAs) is that they allow for high speed parallel read out since the driving electronics may not be built in like a

photodiode pair for more than 30 different lights and surfaces they are just awesome but not intelligent (unlike TSOPs) but you can make them intelligent using your programming skills and some thinking

e of white surface (paper in my case) up to 50cm (*conditions applied ) even in the presence of very ir-

5.11 working of Ir-photodiode

led OFF and subtract it from reading when led only. This principle

assumes that the neighbouring IR conditions remains unchanged in between two readings.


• BC547 or any switching element • some discretes

CAUTION: As you can see, there is no resistance in series with IR-led. so if the transistor is kept ON for more than few milliseconds, IR-led will be damaged. By default, the output of atmega pins is high when unprogrammed. So first program the chip and then connect IR-led, or use a toggle switch in between. So, how far can it go??? that’s the question which came in everyone's mind while using ir-sensors. normally, people think that ir-led-photodiode works up to 12-15 cms only for longer distances we should use TSOP. So here i tested my ir-pair for a distance of 50cms the main principle is to overdrive the ir-led at higher voltage with 7V i got 50cms. (CAUTION : remember, overdriving is risky if not done properly)


Advantages:

Reduced man efforts

Save time

Speedy

Economically cheaper

Required less space

Dis-Advantages:

Some times faulty

Affected by external wheather

Maintanence required

Not get specified Judgement


Chapter 6: Conclusion

By performing this project we at last concluded that when the Train (line

follower) will pass in the way than the IR rays of the sensors will cuts off and

the gate will automatically controlled.

By this we get the idea how to controlled the gate automatically and how this

problem helpful for others.


Chapter 7: Further Extended

Here we have use little different concept of our problem. Many of student

have an idea of this profect and also some what had also done it. Here in our

problem Automatic Railway Gate Crossing there is mainly relation wth the

Train and Gate (which is automatically opened).

But we have designed the retrived different concept in case of the train we

are making LINE FOLLWER ROBOT as our train and as the robot will pass

through the sensors the IR rays will cuts off and the Gate will automatically

closed.

So by this it seems little different than others.

Also our problem in future may be useful for traffic problem also useful for

Indian Railway for the auto-gate mechanisms as by this they reduced the jobs

for the gate watch man for controlling.


Bibliography:

indianengineer.wordpress.com

www.mycollegeproject.com

www.seminarprojects.com

www.electrofriends.com

www.scribd.com

www.engineers.com

www.wikipedia.com

www.robotics .com

www.engineersgarage.com

6th Sem Report

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