ACKNOWLEDGMENT

We would like to express our sincere thank to our beloved principal, staff members and special thanks to our guide Mr.Gurjot Singh The materials available with the listed reference books have a significant impact on this paper. We gratefully thank to the authors and publications of these reference books. My special thanks and regards also goes to my supervisors and engineers in developing the project and people who have willingly helped me out and motivated me with their abilities throughout. Lastly, we cannot forget the blessed showering of God upon us with which we are doing all the efforts and keeping us in a healthy state of mind. Finally, I am grateful to my parents, my elder siblings and the Eternal Lord for all that I have achieved in my life.

1.Introduction

The place where track and highway/road intersects each other at the same level is known as “level crossing”. There are mainly two types of level crossing they are manned level crossing and unmanned level crossing. Manned level crossing is classified into spl.Class, ‟A‟Class, ‟B‟Class,„C‟Class. Unmanned level crossing is classified into „C‟Class, „D‟Class. 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 paper have 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. When the wheels of the train moves over, both tracks are shorted to ground and this acts as a signal to the microcontroller indicating train arrival.

Also an indicator light has been provided to alert the motorists about the approaching train.

2. ACCIDENT DETAILS AVOIDENCE

When the train arrives in a particular direction the transmitter IR senses and generates appropriate signal, then at the same time the receiver IR receives the signal and generates an interrupt. When the interrupt is generated the stepper motor rotates in clockwise direction. When the interrupt ends the stepper motor rotates in anti clock wise direction.

HARDWARE IMPLEMENTATION

Micro Controller

Totally 40-pin DIP package manufactured with CMOS Technology.

L293D (motor driver)

Racially L293D 16DIP /ULN 2003 IC is used to drive the stepper motor.

STEPPER MOTOR

This is used to open and close the gates automatically when it is rotated clock wise or anticlockwise direction. Stepper motor requires 500m amps current, so use the uln2003 or L293D drivers to drive the stepper motor.

SOFTWARE IMPLEMENTATION

Keil software

3. BLOCK DIAGRAM DESCRIPTION

The block diagram consists of six major blocks, they are IR sensors, Microcontroller, L293D, Stepper motor, gate and power supply

3.1 IR SENSORS

Two IR sensor pairs (331,333) are used for transmitting and receiving signals.

3.1.1 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.

3.1.2 IR TRANSMITTER

The transmitter circuit consists of the following components:

1. Resistors

2. IR LED

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

The main aim of this project is to operate and control the unmanned railway gate in the proper manner in order to avoid the accidents in the unmanned railway crossing. In a country like ours where there are many unmanned railway crossings, accidents are increasing day by day. These train accidents are due to the absence of human power in the railway. In order to overcome the accidents due to the above problem we have planned to design the project. Automatic Railway Gate Control System with High Speed Alerting System is an innovative circuit which automatically controls the operation of railway gates detecting the arrival and departure of trains at the gate. It has detectors at the far away distance on the railway track which allows us to know the arrival and departure of the train. These detectors are given to microcontroller which activates the motors which open/close the railway gate correspondingly. Another feature of this circuit is that it has an intelligent alerting system which detects the speed of the train that is arriving. If the speed is found to be higher than the normal speed, then the microcontroller automatically activates the alarm present at the gate. This alerts the passengers at the railway crossing on the road about this. Also this circuit has the feature for Identification of train from other intruders i.e., animals etc .This can be implemented in manned level crossings also, as manual errors can be eliminated by automation.

Circuit Operation:

The operation of the circuit can be clearly explained as follows. Basically the circuit consists of four IR LED-Photodiode pairs arranged on either side of the gate such that IR LED and photodiodes are on either side of the track as shown in the figure below.

Initially transmitter is continuously transmitting the IR light which is made to fall on the receiver. When the train arrives it cuts the light falling on receiver. Let us assume the train is arriving from left to right, now when the train cuts the 1st sensor pair a counter is activated and when it crosses 2nd sensor pair the counter is stopped. This counter value gives the time period which is used to calculate the velocity of the train. The sensor2 output is sent to microcontroller which makes the relay activate which causes the gate to be closed. Now when the last carriage of the train cuts the sensor4 microcontroller de-activates the relay and gates are opened.

How does the sensor know the last carriage?

Here as previously mentioned the counter value is used to calculate the velocity of the train, which means that every wheel of the carriage cuts the sensor pair within small fraction of time based on its velocity. After the last carriage is passed there is no obstacle to the sensor pair within that fraction of time hence it knows that the train has left. One more feature of this circuit is detecting a train accurately i.e., there may be a chance that some obstacle (for e.g. some animal) may cut the sensor then in such a case the counter is made to run for certain period of time (this time period is set considering the possible lowest speed of train) if the

obstacle does not cut the 2nd sensor before this predefined time then this obstacle is not considered as train and gates remain opened.

One more advantage of calculating the velocity of train is, if the speed of the train crosses a limit i.e., if it is travelling at an over speed then the passengers are alerted using a by activating a buzzer. The system basically comprises two IR LED – Photodiode pairs, which are installed on the railway track at about 1 meter apart, with the transmitter and the photodiode of each pair on the opposite sides of the track. The installation is as shown in the block diagram. The system displays the time taken by the train in crossing this distance from one pair to the other with a resolution of 0.01 second from which the speed of the vehicle can be calculated as follows:

Speed (kmph) = Distance/Time

As distance between the sensors is known and constant, the time is counted by the microcontroller and from this information, we can calculate the speed. This circuit has been designed considering the maximum permissible speed for trains as per the traffic rule. The microcontroller is used to process the inputs that are provided by the sensors and generate the desired outputs appropriately.

MICROCONTROLLER

It is designed using 8051 microcontroller to avoid railway accidents happening at unattended railway gates. The Micro controller is a low power; high performance CMOS 8-bit micro controller with 4K bytes of Flash programmable and erasable read only memory (PEROM). The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional non-volatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel is a powerful microcomputer, which provides a highly flexible and cost-effective solution to many embedded control applications. By using this controller the data inputs from the smart card is passed to the Parallel Port of the pc and accordingly the software responds. The IDE for writing the embedded program used is KEI L software.

FEATURES OF MICROCONTROLLER The AT89C52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16-bit timer/counters, six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89C52 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.

3.2.1 Keil Micro vision Integrated Development Environment. Keil Software development tools for the 8051 micro controller family support every level of developer from the professional applications engineer to the student just learning about embedded software development. The industry-standard Keil C Compilers, Macro Assemblers, Debuggers, Real-time Kernels, and Single-board Computers support ALL 8051- compatible derivatives and help you get your projects completed on schedule. The source code is written in assembly language .It is saved as ASM file with an extension. A51.the ASM file is converted into hex file using keil software. Hex file is dumped into micro controller using LABTOOL software. At once the file is dumped and the ROM is burnt then it becomes an embedded one.

3.3 L293D PUSH-PULL FOUR CHANNEL DRIVER WITH DIODES 600ma output current capability per channel 1.2a peak output current (non repetitive) per channel enable facility over temperature protection logical "0" input voltage up to 1.5 v (high noise immunity) internal clamp diodes

The Device is a monolithic integrated high voltage, high current four channel driver designed to accept standard DTL or TTL logic levels and drive inductive loads (such as relays solenoids, DC and stepping motors) and switching power transistors. To simplify use as two bridges each pair of channels is equipped with an enable input. A separate supply input is provided for the logic, allowing operation at a lower voltage and internal clamp diodes are included. This device is suitable for use in switching applications at frequencies up to 5 kHz. The L293D is assembled in a 16 lead plastic package which has 4 centre pins connected together and used for heat sinking. The L293DD is assembled in a 20 lead surface mount which has 8 centre pins connected together and used for heat sinking.

3.1 ADVANTAGES AND DISADVANTAGES OF L293D

ADVANTAGES

Efficient way of speed control of DC motor. Produces more torque. Produces less noise.

DISADVANTAGES

It is not applicable for AC motor.

APPLICATIONS

Industries. Traction. Home appliance.

STEPPER MOTOR

3.4 STEPPER MOTOR the stepper tutorial deals with the basic final stage drive circuitry for stepping motors. This circuitry is centered on a single issue, switching the current in each motor winding on and off, and controlling its direction. The circuitry discussed in this section is connected directly to the motor windings and the motor power supply, and this circuitry is controlled by a digital system that determines when the switches are turned on or off. This section covers all types of motors, from the elementary circuitry needed to control a variable reluctance motor, to the H-bridge circuitry needed to control a bipolar permanent magnet motor. Each class of drive circuit is illustrated with practical examples, but these examples are not intended as an exhaustive catalogue of the commercially available control circuits, nor is the information given here intended to substitute for the information found on the

manufacturer's component data sheets for the parts mentioned. This section only covers the most elementary control circuitry for each class of motor. All of these circuits assume that the motor power supply provides a drive voltage no greater than the motor's rated voltage, and this significantly limits motor performance. The next section, on current limited drive circuitry, covers practical high-performance drive circuits

3.4.1 Stepping Sequences for a Four-Phase Unipolar Permanent Magnet Stepper Motor This kind of motor has four coils which, when energized in the correct sequence, cause the permanent magnet attached to the shaft to rotate. There are two basic step sequences. After step 4, the sequence is repeated from step 1 again reversing the order of the steps in a sequence will reverse the direction of rotation. Here are some possible connection diagrams and some software

3.4.2 Single-Coil Excitation - Each successive coil is energized in turn. This sequence produces the smoothest movement and consumes least power.

3.4.3Two-Coil Excitation - Each successive pair of adjacent coils is energized in turn. This is not as smooth and uses more power but produces greater torque the excitation of Coil 1. is always the inverse of the excitation of Coil 3. So, with the right circuit the excitation of Coil 4 is always the inverse of the excitation of Coil 2. You can generate this sequence with only two data lines. Interleaving the two sequences will cause the motor to half-step.

4. APPLICATIONS Real time transport systems.

5. ADVANTAGES Accident avoidance. Human Resource. Safety and quality of services

POWER SUPPLY

COMPONENTS:-

Transformer 12-0-12(500MA) Diodes IN4007 (4) Voltage regulator (7812), (7809), (7805) Capacitor 470uF Capacitor 1uF (2)

TRANSFORMER (12-0-12):-

It is a step down transformer used to step down the main supply voltage from 230 AC to lower value .this 230 AC voltages cannot be used directly, thus it is stepped down. The transformer consists of primary and secondary coils. To reduce or step down the voltage, the transformer is designed to contain less number of turns in it secondary core .the output from secondary core is also AC waveform. Thus the conversion from AC to DC is essential. This conversion is achieved by using rectifier unit.

12-0-12 means that the voltage or the potential difference (p.d.) between each of the end terminals of the secondary winding and the mid-point of the secondary winding of the transformer is 12V. And, between the two ends of the secondary winding, you will get 12 + 12 = 24V. 500mA means the current delivery capability of the secondary winding of the transformer. Normally it is said in VA. In your case it would be 25 x 0.5 = 12VA. The ratings are arrived at based on the requirements of the loads that are to be connected to the transformer. The limiting criteria are the winding wire thickness and the insulation of the winding.

This means the output voltage available is 12 volts from center on both sides. End to end is 24 volts. The safe maximum current rating of this transformer is 500 ma. 

The ratings depend on the thickness and the number of secondary windings on the core. More the thickness of the copper wires more the current rating and larger the size of the transformer. 

Generally the transformer rating will be in VA (volt amperes). The ones used for TVs will be in the range of 250 VA and for refrigerators will be 750 to 12-0-12 means that the voltage or the potential difference (p.d.) between each of the end terminals of the secondary winding and the mid-point of the secondary winding of the transformer is 12V. And, between the two ends of the secondary winding, you will get 12 + 12 = 24V. 500mA means the current delivery capability of the secondary winding of the transformer. Normally it is said in VA. In your case it would be 25 x 0.5 = 12VA. The ratings are arrived at based on the requirements of the loads that are to be connected to the transformer. The limiting criteria are the winding wire thickness and the insulation of the winding.

1000 VA.

DIODES(IN4007):-

This is a simple, very common rectifier diode. Often used for reverse voltage protection, the 1N4007 is a staple for many powers, DC to DC step up, and breadboard projects. 1N4007 is rated for up to 1A/1000V. 

Features

• Diffused Junction

• High Current Capability and Low Forward Voltage Drop

• Surge Overload Rating to 30A Peak

• Low Reverse Leakage Current

• Lead Free Finish, RoHS Compliant (Note 3) ODES

Mechanical Data

• Case: DO-41

• Case Material: Moulded Plastic. UL Flammability Classification

Rating 94V-0

• Moisture Sensitivity: Level 1 per J-STD-020D

• Terminals: Finish - Bright Tin. Plated Leads Solderable per

MIL-STD-202, Method 208

• Polarity: Cathode Band

• Mounting Position: Any

• Ordering Information

• Marking: Type Number

• Weight: 0.30 grams (approximate)

VOLTAGE REGULATOR:-

The 78xx (sometimes L78xx, LM78xx, MC78xx...) is a family of self-contained fixed linear voltage regulator integrated circuits. The 78xx family is commonly used in electronic circuits

requiring a regulated power supply due to their ease-of-use and low cost. For ICs within the family, the xx is replaced with two digits, indicating the output voltage (for example, the 7805 has a 5 volt output, while the 7812 produces 12 volts). The 78xx lines are positive voltage regulators: they produce a voltage that is positive relative to a common ground. There is a related line of 79xx devices which are complementary negative voltage regulators. 78xx and 79xx ICs can be used in combination to provide positive and negative supply voltages in the same circuit.

78xx ICs have three terminals and are commonly found in the TO220 form factor, although smaller surface-mount and larger TO3packages are available. These devices support an input voltage anywhere from a couple of volts over the intended output voltage, up to a maximum of 35 to 40 volts depending on the make, and typically provide 1 or 1.5 amperes of current (though smaller or larger packages may have a lower or higher current rating)

ADVANTAGES

78xx series ICs do not require additional components to provide a constant, regulated source of power, making them easy to use, as well as economical and efficient uses of space. Other voltage regulators may require additional components to set the output voltage level, or to assist in the regulation process. Some other designs (such as a switched) may need substantial engineering expertise to implement.

78xx series ICs have built-in protection against a circuit drawing too much power. They have protection against overheating and short-circuits, making them quite robust in most applications. In some cases, the current-limiting features of the 78xx devices can provide protection not only for the 78xx itself, but also for other parts of the circuit.

DISADVANTAGES

The input voltage must always be higher than the output voltage by some minimum amount (typically 2 volts). This can make these devices unsuitable for powering some devices from certain types of power sources (for example, powering a circuit that requires 5 volts using 6-volt batteries will not work using a 7805).

As they are based on a linear regulator design, the input current required is always the same as the output current. As the input voltage must always be higher than the output voltage, this means that the total power (voltage multiplied by current) going into the 78xx will be more than the output power provided. The extra input power is dissipated as heat. This means both that for some applications an adequate heat sink must be provided, and also that a (often substantial) portion of the input power is wasted during the process, rendering them less efficient than some other types of power supplies. When the input

voltage is significantly higher than the regulated output voltage (for example, powering a 7805 using a 24 volt power source), this inefficiency can be a significant issue.

There are common configurations for 78xx ICs, including 7805 (5 volt), 7806 (6 volt), 7808 (8 volt), 7809 (9 volt), 7810 (10 volt), 7812 (12 volt), 7815 (15 volt), 7818 (18 volt), and 7824 (24 volt) versions. The 7805 is common, as its regulated 5 volt supply provides a convenient power source for most TTL components. Each device in this series has minimum input voltage to be maintained to get regulated output

Positive regulator

1. Input pin2. Ground pin3. Output pin

Negative regulator

1. Ground pin 2. Input pin3. Output pin

CAPACITOR:-

Filter capacitors are capacitor used for filtering of undesirable frequencies. They are common in electrical and electronic equipment, and cover a number of applications, such as:

Glitch removal of Direct current  (DC) power rails Radio frequency interference (RFI) removal for signal or power lines entering or

leaving equipment

Capacitors used after a voltage regulator to further smooth DC power supply

Capacitors used in audio, Intermediate frequency (IF) or radio frequency (RF) frequency filters (e.g. low pass, high pass, notch, etc.)

Arc suppression, such as across the contact breaker or 'points' in a spark ignition engine

Filter capacitors are not the same as reservoir capacitor, the tasks the two perform are different, albeit related.

The capacitor-input filter, also called pi filter due to its shape that looks like the Greek letter π, is a type of electronic filter. Filter circuits are used to remove unwanted or undesired frequencies from a signal.

A typical capacitor input filter consists of a filter or reservoir capacitor  C1, connected across the rectifier output, an inductor  L, in series and another filter or smoothing capacitor, C2, connected across the load, RL. A filter of this sort is designed for use at a particular frequency, generally fixed by the AC line frequency and rectifier configuration. When used in this service, filter performance is often characterized by its regulation and ripple.

1. The capacitor C1 offers low reactance to the AC component of the rectifier output while it offers infinite resistance to the DC component. As a result the capacitor  shunts an appreciable amount of the AC component while the DC component continues its journey to the inductor L

2. The inductor L offers high reactance to the AC component but it offers almost zero resistance to the DC component. As a result the DC component flows through the inductor while the AC component is blocked.

3. The capacitor C2 bypasses the AC component which the inductor had failed to block. As a result only the DC component appears across the load RL.

The component value for the inductor can be estimated as an inductance that resonates the smoothing capacitor(s) at or below one tenth of the minimum ac frequency in the power supplied to the filter (100 Hz from a full-wave rectifier in a region where the power supply is 50Hz). Thus if reservoir and smoothing capacitors of 2200 microfarads are used, a suitable minimum value for the inductor would be that which resonates 2200 microfarads (μF) to 10 Hz, i.e. 1 mH. A larger value is preferable provided the inductor can carry the required supply current.

NOTE: Assuming a resonance equation of 

Capacitor input filters can provide extremely pure dc supplies, but have fallen out of favour because inductors tend to be unavoidably heavy, which has led to the often-preferred choice of voltage regulators instead.

Advantages

More output voltage & Ripple less output

Disadvantages

Large in size and weight & High cost

CONCLUSION

The accidents are avoided at places where there is no person managing the railway crossing gates. Here we use the stepper motor to open and close the gates automatically when it is rotated clockwise or anticlockwise direction. When the train arrives in a particular direction the transmitter IR senses and generates appropriate signal, then at the same time the receiver IR receives the signal and generates an interrupt. When the interrupt is generated the stepper motor rotates in clockwise direction. When the interrupt ends the stepper motor rotates in anti clock wise direction

REFERENCES

Adler, R. B., A. C. Smith, and R. L. Longani: “Introduction to Semiconductor Physics,” vol. 1, p. 78, Semiconductor

Electronics Education Committee, John Wiley & Sons, Inc., New York, 1964.

Schade, O. H.: “Analysis of Rectifier Operation”, proc. IRE, vol.31, pp. 341-361, July, 1943.

Stout, M. B.: “Analysis of Rectifier Circuits”, Elec. Eng., vol. 54, September, 1935.

Jacob Millman Christos C. Halkias.: “Electronic Devices And Circuits”, Tata McGraw-Hill Publishing Company Ltd. Sep, 2003.

The 8051 Microcontroller and Embedded Systems using Assembly and

C by Muhammad Ali Mazidi, Janice Gillispie, Rolin D.Mckinlay.

Part of stepping motors by Douglas W.Jones, the university of IOWA Department of computer science.

WEBSITES

WWW.circuit diagram.com

Electonicshub.com