PROJECT REPORTON

“Automatic Railway Gate Controller Using Stepper Motor”

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 signalling 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.

INDEXS.no List of contents page No

01 Introduction

1.1 Introduction

1.2 Block diagram & Description

02 Stepper motor

3.1 Introduction to stepper motor 3.2 types & applications. 03 ULN 2003 4.1 Introduction to ULN 2003

4.2 Pin description of ULN 2003

04 LM 324 5.1 LM 324 & Features

05 Light Dependable Resistor

06 Interfacing Devices

7.1 Interfacing of Stepper Motor with ULN2003

7.2 Stepper Motor Interfacing with AT89C51

7.3 Interfacing of Lm324 with At89c51

7 Regulated Power Supply

8.1 Regulated Power Supply & Features

8 Conclusion

9 Bibliography

CHAPTER 1

INTRODUCTION

1.1 INTRODUCTIONAim 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 un- attended 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 it’s a 16 pin IC.

Features:

There is no time lag to operate the device

Accuracy.

1

BLOCK DIAGRAM:

Fig 1. 1.1 Block Diagram of AUTOMATIC RAILWAY GATE

CONTROLLER

2

1.2 BLOCK DIAGRAM DESCRIPTION:

ULN 2003

LM324

LIGHT DEPENDANT RESISTOR

STEPPER MOTOR REGULATED

POWER SUPPLY

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.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 signalling 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.

3

CHAPTER 2

STEPPER MOTOR

STEPPER MOTOR

3.1 Introduction to stepper motor:

A stepper motor (or step motor) is a brushless, synchronous electric motor that

can divide a full rotation into a large number of steps. The motor's position can be

controlled precisely, without any feedback mechanism (see open loop control). Stepper

motors are similar to switched reluctance motors (which are very large stepping motors

with a reduced pole count, and generally are closed-loop commutated).

Fig no: 3.1.1 Basic stepper motor

Fundamentals of Operation:

Stepper motors operate differently from normal DC motors, which rotate 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 thus

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 integral number of steps making a full rotation.

In that way, the motor can be turned by a precise angle.

Stepper motor characteristics:

Stepper motors are constant power devices. As motor speed increases, torque

decreases. The torque curve may be extended by using current limiting drivers and

increasing the driving voltage. Steppers exhibit more vibration than other motor types, as

the discrete step tends to snap the rotor from one position to another. This vibration can

become very bad at some speeds and can cause the motor to lose torque. The effect can

be mitigated by accelerating quickly through the problem speed range, physically

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.

Open-loop versus closed-loop commutation

Steppers are generally commutated open loop, 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

(eg. an 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.

3.2 Types & Applications:

There are three main types of stepper motors:

Permanent Magnet Stepper

Hybrid Synchronous Stepper

Variable Reluctance Stepper

Two-phase stepper motors:

There are two basic winding arrangements for the electromagnetic coils in a two

phase stepper motor: bipolar and unipolar.

Unipolar motors:

A unipolar stepper motor has logically two windings per phase, one for each

direction of magnetic field. Since in this arrangement a magnetic pole can be reversed

without switching the direction of current, the commutation circuit can be made very

simple (e.g. a single transistor) for each winding. Typically, given a phase, one end of

each winding is made common: giving three leads per phase and six leads for a typical

two phase motor. Often, these two phase commons are internally joined, so the motor has

only five leads.

Fig 3.2 Unipolar stepper motor coils

In the construction of unipolar stepper motor there are four coils. One end of each coil is tide together and it gives common terminal which is always

connected with positive terminal of supply. The other ends of each coil are given for interface.  Specific color code may also be given. Like in my motor orange is first coil (L1), brown is second (L2), yellow is third (L3), black is fourth (L4) and red for common terminal.

By means of controlling a stepper motor operation we can

1. Increase or decrease the RPM (speed) of it2. Increase or decrease number of revolutions of it3. Change its direction means rotate it clockwise or anticlockwise

To vary the RPM of motor we have to vary the PRF (Pulse Repetition Frequency). Number of applied pulses will vary number of rotations and last to change direction we have to change pulse sequence.

So all these three things just depends on applied pulses. Now there are three different modes to rotate this motor

1. Single coil excitation2. Double coil excitation3. half coil excitation

Unipolar stepper motors with six or eight wires may be driven using bipolar drivers

by leaving the phase commons disconnected, and driving the two windings of each phase

together [diagram needed]. It is also possible to use a bipolar driver to drive only one

winding of each phase, leaving half of the windings unused [diagram needed].

Bipolar motor:

Bipolar motors have logically a single winding per phase. The current in a

winding needs to be reversed in order to reverse a magnetic pole, so the driving circuit

must be more complicated, typically with an H-bridge arrangement. There are two leads

per phase, none are common.

Static friction effects using an H-bridge have been observed with certain drive

topologies Because windings are better utilized, they are more powerful than a unipolar

motor of the same weight.

Applications:

Computer-controlled stepper motors are one of the most versatile forms of

positioning systems. They are typically digitally controlled as part of an open loop

system, and are simpler and more rugged than closed loop servo systems.

In the field of 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.

In floppy disk drives, flatbed scanners, computer printers, plotters and many more

devices.

CHAPTER 3

ULN 2003

ULN 2003

4.1 Introduction:

The ULN2003 is a high-voltage, high current Darlington drivers comprised of

seven NPN Darlington pairs.

Features:

1) Output current (single output) 500mA MAX.

2) High sustaining voltage output 50V MIN.

3) Input compatible with various types of logic.

Applications:

Relay

Hammers

Lamp and display(LED)drivers

4.2 PIN DIAGRAM:

Fig:4.2.1 Pin diagram of ULN2003

Features:

No. of pins:16

Temperature, Operating Range:-20°C to +85°C

Transistor Polarity:NPN

No. of Transistors:7

Case Style:DIP-16

Min operating temperature:-20°C

Max operating temperature:85°C

Base Number:2003

Max Output current:500mA

IC Generic Number:2003

Input Type:TTL, CMOS 5V

Output Type: Open Collector

Transistor Type: Power Darlington

Max Input Voltage:5V

Max Output voltage:50V

PIN CONNECTIONS OF ULN2003:

Fig 4.2.2 Pin configuration of ULN 2003

The ULN2001A, ULN2002A, ULN2003 and ULN2004Aare high Voltage, high

current Darlington arrays each containing seven open collector Darlington pairs with

common emitters. Each channel rated at 500mAand can withstand peak currents of

600mA.Suppressiondiodesare included for inductive load driving and the inputs are

pinned opposite the outputs to simplify board layout.

These versatile devices are useful for driving a wide range of loads including

solenoids, relays DC motors; LED displays filament lamps, thermal print heads and high

power buffers. The ULN2001A/2002A/2003A and 2004A are supplied in 16 pin plastic

DIP packages with a copper lead frame to reduce thermal resistance. They are available

also in small outline package (SO-16) as ULN2001D/2002D/2003D/2004D.

SCHEMATIC DIAGRAM OF DARLINGTON PAIR: The circuit below is

a ‘Darlington Pair’ driver. The first transistor’s emitter feeds into the second transistor’s

base and as a result the input signal is amplified by the time it reaches the output.

Darlington pairs are back to back connection of two transistors with some source

resistors.

Fig: 4.2.3 The Darlington pair connection of transistor.

The important point to remember is that the Darlington Pair is made up of two

transistors and when they are arranged as shown in the circuit they are used to amplify

weak signals. The amount by which the weak signal is amplified is called the ‘GAIN’.

.

CHAPTER 4 LM 324

LM 324:

5.1 Introduction:

These amplifiers are designed to specifically to operate from a solitary supply

over a wide range of voltages. Also can function when the difference between the two

supplies is 3V to 30V and VCC is at least 1.5V more positive than the input common

mode voltage.

Fig: 5.1 Pin diagram of LM324

Pin Descriptions

V+ = Supply voltage

GND = Gnd (0V) connection for supply voltage

Input(s) = Input to Op-Amp

Output(s) = Output of Op-Amp

Features: Supply voltage V + : +32VDC or +16VDC

Differential Input Voltage : 32VDC

Input Voltage : -0.3VDC to +32VDC

Power Dissipation : 570mW

Operating Temperature : 0 to 70C degree

Output Current Source : Typical 40mA

Output Current Source : Typical 40mA

Output Current Sink : Typical 20mA

Input Offset Voltage : Typical 2.0mVDC

Operates on a single supply over a range of voltages

Unique features: In the linear mode, the input common-mode voltage range includes ground

and the output voltage can also swing to ground, even though operated from only a

single power supply voltage. The unity gain crossover frequency and the input bias

current are temperature-compensated.

Applications:

In Transducer amplifiers.

DC amplification blocks and conventional operations.

24

CHAPTER 5

LIGHT DEPENDENT RESISTOR

LIGHT DEPENDENT RESISTOR

6.1 Description:

This practical is about using a light dependent resistor (LDR) as a sensor. The

LDR must be part of a voltage divider circuit in order to give an output voltage, Vout ,

which changes with illumination.

A light dependent resistor is a resistor whose resistance decreases with increasing incident light intensity. It can also be referenced as a photo conductor. An LDR is made of a high resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron (and its hole partner) conduct electricity, thereby lowering resistance.

An LDR device can be either intrinsic or extrinsic. An intrinsic semiconductor has its own charge carriers and is not an efficient semiconductor, e.g. silicon. In intrinsic devices the only available electrons are in the valence band, and hence the photon must have enough energy to excite the electron across the entire band gap. Extrinsic devices have impurities, also called do pants, and added whose ground state energy is closer to the conduction band; since the electrons do not have as far to jump, lower energy photons (i.e., longer wavelengths and lower frequencies) are sufficient to trigger the device. If a sample of silicon has some of its atoms replaced by phosphorus atoms (impurities), there will be extra electrons available for conduction.

Fig 6.1.1 Light dependent resistor26

Note that an LDR responds in an extremely non-linear way to the light intensity. The

resistance of a LDR changes from a few meg-ohms in dim light to a few kilo ohms in

bright light (maybe even a few ohms depending upon the light intensity and LDR used.).

So I would suggest that u first connect the LDR as

VCC ------ LDR------- LM 324 -------- Microcontroller.

and plot the voltage across the 1K resistor with respect to different light intensities on the

LDR.Then connect this voltage output to a ADC via a simple non-inverting op-amp

amplifier and connect the ADC to the Microcontroller.

Applications:

Camera light meters, street lights, clock radios, alarms, and outdoor clocks.

They are also used in so dynamic compressors together with a small incandescent

lamp or light emitting diode to control gain reduction.

Lead sulfide and Idiam sulfide LDRs are used for the mid infrared spectral

region.Ge: Cu photoconductors are among the best far-infrared detectors

available, and are used for infrared astronomy and infrared spectroscopy.

CHAPTER 6

INTERFACING DEVICES

28

6.1 INTERFACING OF STEPPER MOTOR WITH ULN2003

Fig no:7.1.1 ULN2003 is interfaced with the stepper motor

ULN2003 is a 16 pin dip. Its connections can be explained as follows

First 4-pins of chip are connected to microcontroller pin at 37-40 pins and second

at 21-24 pins. And 8th pin of chip is grounded. A stepper contains 5 terminals, 4 winding

wires and a power supply wire. These 4 winding wires are connected to chip and another

to supply. in this circuit too the four pins "Controller pin 1",2,3 and 4 will control the

motion and direction of the stepper motor according to the step sequence sent by the

controller.

29

7.2 STEPPER MOTOR INTERFACING WITH AT89C51

fig no: 7.2.1 stepper motor interfacing with AT89C51 using ULN2003.

The interfacing of stepper motor consists of several parts like AT89C51

microcontroller, stepper motor, and ULN2003 current driver chip. This can be used in

1 vcc 40 2 393 384 37 5 366 A 357 T 348 8 33 9 9 32 10 C 3111 5 3012 1 2913 28 14 2715 2616 2517 2418 2319 22 20 21

MOTOR

1 u 92 l 103 n 114 2 12 5 0 136 0 147 3 15 8 16

this project for the purpose of gate control . For the gate control a 12v stepper motor is

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

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

driven by 5v supply.

30

Fig no: 7.2.2 The block diagram of stepper motor interfacing

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.

31

7.3 INTERFACING OF LM 324 with AT 89C51 MICROCONTROLLER

15Kohm

Fig 7.3.1 Interfacing of LM324 with AT89c51 Microcontroller

The LM324 integrated circuit is a Quad operational amplifier(op-amp).The device has four individual Op-amp circuits housed in a single package.

1 L 14 2 M 133 3 124 2 115 4 106 97 8

40 A T 8 99 C 5 1

31 18

19 20

32

CHAPTER 7

REGULATED POWERSUPPLY

33

8.1 REGULATED POWER SUPPLY:

A variable regulated power supply,also called a variable bench power supply,is one

which you can continuously adjust the output voltage to your requirements. Varying the

output of the power supply is recommended way to test a project after having double checked

parts placement against circuit drawings and the parts placement

This type of regulation is ideal for having a simple variable bench power supply.

Actually this is quite important because one of the first projects a hobbyist should

undertake is the construction of a variable regulated power supply. While a dedicated

supply is quite handy e.g 5V or 12V,it’s much handier to have a variable supply on hand,

especially for testing.

Most digital logic circuits and processors need a 5 volt power supply. To use these

parts we need to build a regulated 5 volt source. Usually you start with an unregulated

power to make a 5 volt power supply, we use a LM7805 voltage regulator IC (Integrated

Circuit).

The IC is shown below.

Fig: 8.1.1 LM 7805 block diagram

34

Fig: 8.1.2 Pin representation of LM 7805

The LM7805 is simple to use. You simply connect the positive lead of your

unregulated DC power supply(anything from 9VDC to 24VDC) to the Input pin, connect

the negative lead to the Common pin and then when you turn on the power, you get a 5

volt supply from the Output pin.

Circuit features:

Brief description of operation: Gives out well regulated +5V output,

output current capability of 100mA.

Circuit protection: Built-in overheating protection shuts down output when

regulator IC gets too hot.

Circuit complexity: Very simple and easy to build.

Circuit performance: Very stable +5V output voltage, reliable operation

Availability of components: Easy to get, uses only very common basic

components.

Design testing: Based on datasheet example circuit, I have used this circuit

successfully as part of many electronic projects.

Applications: Part of electronics devices, small laboratory power supply

35

CHAPTER 8

CONCLUSION

8 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 on

attendant it is more economical at above mentioned places than traditional railway

crossing gate system. We know that though it is very beneficial but it is also

impossible to install such system at each and every places, but it gives certainly a

considerable benefit to us, thereby to our nation.

CHAPTER 9

BIBLIOGRAPHY

43

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