SREE NARAYANA GURUKULAM COLLEGE OF ENGINEERINGKADAYIRUPPU, KOLENCHERY

MINI PROJECT REPORT ON

AUTOMATIC RAILWAY GATE CONTROLDEPARTMENT OF ELECTRONICS & COMMUNICATIONS ENGG SNG COLLEGE OF ENGINEERING KOLENCHERY 2009

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SREE NARAYANA GURUKULAM COLLEGE OF ENGINEERINGKADAYIRUPPU, KOLENCHERY

MINI PROJECT REPORT 2009AUTOMATIC RAILWAY GATE CONTROL

BY: NEERAJA KUMAR NEETHU BHASKARAN NEETHU S NAIR

GUIDED BY: Mr. ANOOP.T.R Mrs. ASHA.R.S Mrs. SONIA.P

Internal Examiner4

External Examiner

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SREE NARAYANA GURUKULAM COLLEGE OF ENGINEERINGKADAYIRUPPU, KOLENCHERY

Department of Electronics and Communication

MINI-PROJECT REPORT 2009 CERTIFICATE This is to certify that this project report entitled AUTOMATIC RALLWAY GATE CONTROL is a report of the mini- project work done by. during the year 2008.Kadayiruppu Date Staff in charge Head of the Department

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Internal examiner

External examiner

ACKNOWLEDGEMENTFirst of all I thank God almighty for his blessings that gave me the courage and mental ability to present y mini project and make it a great success. I am happy to express my gratitude to the Head of the Department Mr.A.C.Mathai who encouraged me to make this project great success. I also thank Mr.Anoop.T.K, Mrs.Asha.R.S and Mrs.Sonia.P, lecturers in Electronics and Communication Department for giving guidance for the project. I also take this great opportunity to thank all other lecturers of Electronics and Communication Department whose valuable suggestions and active participation made this project a great success. Last but certainly not the least; I thank all my friends for their help and Cooperation.

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CONTENTS

1. ABSTRACT 2. BLOCK DIAGRAM BLOCK DIAGRAM EXPLANATION MATERIALIZATION OF BLOCK DIAGRAM 3. CIRCUIT DIAGRAM CIRCUIT EXPLANATION 4. WORKING 5. ALGORITM 6. FLOW CHART 7. PROGRAM 8. PCB FABRICATION 9. PCB CIRCUIT AND COMPONENT PLACING 10. COMPONENT LIST AND COST ESTIMATE 11. CONCLUSION 12. REFERENCE 13. DATA SHEETS5

ABSTRACT

Electronically or remotely controlled railway gate systems are emerging as a replacement to the manual systems presently under use. It has been observed time and again that most of the accidents occur at level crossings due to human error. The system devised and envisaged in the project is a microcontroller based Railway Gate Control system with facilities for controlling the road signals. It will help a long way in reducing accidents due to human error since both audio and visual indications are provided for warning.

It may not be out of place to mention that by adding additional features supported by advanced on board computers the power of the system can be enhanced to suit multiple tracks and multiple roads. The system devised will be very cost effective and hundred percent full proof and will be extremely efficient In comparison to manual systems.

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BLOCK DIAGRAM

1

2

DC MOTOR

Buzzer

Dis pla y

Sensor 1

Sensor 2

Microcontroller

Rela y1

Relay driver

Relay 2

Switches

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BLOCK DIAGRAM EXPLANATION

Microcontroller The heart of this system is the microcontroller, which performs the arithmetical and logical functions thereby steering the peripherals for a full proof and successful performance. It is easy to use an eight-bit microcontroller in this section. Sensor Here we are using pressure sensors. This section senses and intimates the CPU about the presence of any obstacles. Here we require two sensors. The sensors produce a logic low output when a train is passing over the sensor. The C determine the direction of the train by analyzing the priority of these outputs of the sensors. Relay and Relay Drivers The relays are used to isolate both the controlling and controlled equipments. The relay is an electromagnetic device, which consumes comparatively large amount of power. Hence it is impossible for the interface IC to drive the relay satisfactorily. To enable this, a driver circuitry, which will act as a buffer circuit, is to be incorporated between of them. The Driver circuitry senses the presence of a high level at the input and drives the relay from another Voltage source. Here the relays are used to switch the electrical supply to a DC motor in order to get the motor rotation in both clockwise and counter clockwise directions.

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Buzzer It is necessary to indicate an activated system or a depressed switch in time. For this we can accommodate either a visual indication or an audio indication. This block is introduced here to achieve the audio indication. The buzzer is one of the piezo-electric sensors, which converts the electrical oscillations to the acoustical waves. Signal lamps and Display This is used to give the green, orange and red signals to the vehicles on the road. The display used here is of common anode type. The display, displays the remaining time to close the gate. Switches The switches are used to intimate the system about the arrival of a train. There must be at least two switches to distinguish the direction of the train. Motor The motor is used to close and open the gate. Thus the direction of the motor must be reversed. Therefore we use a DC motor.

Power supply The system requires a regulated voltage of +5v along with an unregulated 12v supply for relay. These low voltages are obtained from the domestic supply with the help of this block.

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MATERIALIZATION OF BLOCK DIAGRAM

The first step before getting into the system design is to select the microcontroller. There are a number of microcontrollers available in the market. Various manufacturers makes there own microcontrollers. Here we can select the MCS51 family microcontrollers, since it is the first generation microcontrollers. Also many manufacturers like INTEL, ATMEL and PHILIPS makes these chips. The most popular IC in the MCS 51 family is 8051. This IC holds 128 byte of internal ram and 4kilo bytes of internal prom. The 89xx family holds the Electrically Alterable Programmable Read Only Memory (EAPROM) or Flash memory. Thus we are going to use the IC 8951

Sensor section: Since the system is for demonstration we can use two pressure sensors Relay:A 12V, 6Amp, 100- relay is sufficient for demonstration purpose. An NPN transistor can easily drive it. The Transistor cannot be connected to the microcontroller since sourcing capacity is of the port is less than one milliampere. Therefore we must use two transistors, wired as a Darlington pair. The transistors are biased to operate either in cut off region or in saturation region.

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Power supply:-

Since the system requires a +5v regulated power supply it is necessary to use a step down transformer. A 12-0-12V, 1amp transformer is sufficient to step down the AC voltage in the domestic power socket. A center tap rectifier is thus required for this purpose. For the regulation a 7805 IC can be accommodated after a capacitor filter. The +12V supply for the relay can be taken from the input of the regulator IC. Buzzer: A piezo-electric buzzer with internal oscillator circuitry is readily available in market. It is operated from 1.5V to 2.7V consuming the power only in milli watts. This buzzer can there fore be driven directly by the PPI. Signal lamps and Display One bilateral LED can be used as the signal lamp. In the display section we can use the 7-segment displays LT542

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CIRCUIT DIAGRAM

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CIRCUIT OPERATION

MicrocontrollerU1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 RST P3.0 P3.1 P3.2 P3.3 P3.4 P3.5 P3.6 P3.7 XTAL2 XTAL1 AT89C52 P0.0 P0.1 P0.2 P0.3 P0.4 P0.5 P0.6 P0.7 EA ALE/PROG PSEN P2.7 P2.6 P2.5 P2.4 P2.3 P2.2 P2.1 P2.0 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21

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The 8-bit microcontroller 89C51 from ATMEL is selected to control the system. This is a 40-pin chip, which contains four input /output ports, 128 byte ram, 4Kbyte of prom. The power is applied across the Vcc (pin 40) and Gnd (pin 20) pins. The external execution is eliminated by connecting the EA pin to Vcc through a resistor. Clock inputs The X1 and X2 inputs are connected to the ends of a piezo electric crystal. We can choose the crystal frequency from 1Mhz to 24Mhz. Also both of the crystal inputs are connected to ground through capacitors of vale 33pf. The clock pin connections are shown below.

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RE S E T

31 R 11 10K

E A /V P P U2

C 7 19 33P F C9 33P F Y 1 12M H z 18 X 2 X 1

P 0 . 6 (A D 6 ) P 0 . 7 (A D 7 ) P 1 .0 (T 2 ) P 1 .1 (T 2 E X ) P 1 .2 P 1 .3 P 1 .4 P 1 .5 P 1 .6 P 1 .7 P 2 .0 (A 8 ) P 2 .1 (A 9 ) P 2 .2 (A 1 0 ) P 2 .3 (A 1 1 ) P 2 .4 (A 1 2 ) P 2 .5 (A 1 3 ) P 2 .6 (A 1 4 ) P 2 .7 (A 1 5 ) P 3 . 0 (R X D ) P 3 .1 (T X D ) P 3 .2 (IN T 0 ) P 3 .3 (IN T 1 ) P 3 .4 (T 0 ) P 3 .5 (T 1 ) P 3 .6 (W R ) P 3 .7 (R D ) P S E N A L E /P R O G

32 1 2 3 4 5 6 7 8 21 22 23 24 25 26 27 28 10 11 12 13 14 15 16 17 29 30

Reset inputs80C 52

. The reset pin is connected to a power On reset circuit. The capacitor voltage at the time of power on will be 1. This will reset microcontroller. The voltage drops to zero shortly after some time. This will remove the reset condition and the microcontroller will start fetching now.

Buzzer

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The buzzer contains a piezo-electric crystal. The crystal is so cut that the natural frequency lies between 1 and 2 K Hz. In order to oscillate this crystal at this frequency it is necessary to apply the same frequency between the opposite faces. This crystal is stamped to a thin metal film. This metal film is mounted on a plastic or acrylic enclosure, which produce a sufficient air column. When ever the buzzer is vibrating in its natural frequency the metal film will also vibrate which results in an air column vibration or simply the audible sound.

Since the user do not know the exact natural frequency it is impossible to vibrate the crystal efficiently. Hence the manufacturers introduced an LC oscillator along with a transistor in side the enclosure. The natural frequency of the LC tank circuit is so calibrated that it will be exactly same as the natural frequency of the crystal. This internal oscillator will contain a BC 547 transistor with the above LC circuit connected at its collector. The crystal is also connected in parallel to this LC circuit. There is a feed back element, which is also stamped in the metal frame. When the metal frame vibrates this feed back element will also vibrate producing an electrical voltage in the same frequency. Out of the two terminals one is connected to the positive rail, which is common to the above circuit, and the other is connected to the base of the transistor via a current limiting resistor. This arrangement will keep the oscillation from damping resulting in a continuous sound.

The entire arrangement will reduce the cost, weight and the external circuitories. Hence the user is supposed to connect only a DC voltage across the two

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wires, which are leading out from the enclosure. One of this is connected to the emitter of the transistor. This must be connected to the negative terminal of the battery while the other one to the positive terminal. This is why because this wire is connected to the collector via the LC tank circuit and the crystal. In addition, there is an advantage that the working voltage lays between a wide range of 1.5V and 27 Volts.

Sensor Here we are using two pressure sensors. The output of the sensors indicate the presence of the train. Whenever the train is crossing the sensor the output goes to low state . A high indicates that the train has passed away.

Relay Driver The relay is an electromagnetic device, which consists of solenoid, moving contacts, fixed contact and a restoring spring. Depending on the output connectivity the relays are classified into two. 1. Single pole double throw relay (SPDT) 2. Double pole double throw relay (DPDT) The specification of the relay will contain the working voltage, solenoid impedance current and voltage rating of the contacts. Here we are using 12V, 100ohm 6Amp. relays.

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When we connect the rated voltage across the coil the back Emf opposes the current flow but after a short time the supply voltage will overcome the back emf and the current flow through the coil increase. When this current is equal to the activating current of the relay the core is magnetized and it attracts the moving contact. Now the moving contact leaves from its initial position where it makes a contact with a fixed terminal known as normally closed terminal (N/c). Now the common contact or moving contact establishes a connection with a new terminal which is indicated as normally open terminal (N/O). Whenever the supply to the coil is withdrawn the magnetizing force is vanished. Now the restoring spring pulls the moving contact back to initial position, where it makes a connection with N/C terminal. However it is also to be noted that at this time also a back emf produced. The withdrawal time may be in microseconds, the back emf may be in the range of few kilovolts and in opposite polarity with the supply terminals. This voltage is known as surge voltage. It must be nutralised or else it may damage the system. A diode across the relay coil in reverse bias, will act as a short circuit for this surge voltage and it will nutralise here itself.

.

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Display Thedisplay section consists of seven-segment display, current limiting

resistors and decoding chip. The seven-segment display has 10 pins. It consists of 8 LEDs, 7 for segments and one for a dot point. One of the two terminals of these LEDs are connected to a single point namely common. This makes two types of displays known as common anode and common cathode displays. As the name indicates a common anode display has one anode and 8 cathodes. One should connect the anode to positive terminal and cathode to appropriate outputs of decoder chip. However there should be a resistor to limit the current flow because excess current can damage the display itself. A value anywhere between 330 ohm and 680 ohm is sufficient for the typical brightness of the display. A logic zero at the segment pins will activate the segment LED. By turning on appropriate segments, we can create numbers from zero to nine.

Power supply

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+12V

1

D6 2 1N4007 D7 2 1N4007 D8 2 1N4007 D10 2 1 1N4007 + 3 + C11 2200mf U5 L7805/TO220 GND VIN VOUT 2 C13 2200mfd VCC 2 1 + C12 10mfd

230V

1

T1

5 6

1

230V

4

8

1

1

12-0-12v/1A 1

The system requires a +5v supply. This can be delivered from the 230V domestic supply. Before applying this to the system we must step down this high voltage to an appropriate value. After that it should be rectified. This will provide a unidirectional current. To achieve a +5V DC we should regulate this. All these are done in the power supply circuitry, which is explained below.

A 12-0-12V step down transformer is connected to provide the necessary low voltage. The transformer also works as an isolator between the hot and cold end. The hot end refers to the 230V supply, which is a hazardous one, and the cold one refers to the low, safe voltage. Now the hot portion appears only at the primary of the transformer. The secondary of the transformer deliver 12V ac pulses along with a ground.

2

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This ac supply goes to a center tap rectifier, which converts the ac into a unidirectional voltage. The ripples in the resulting supply is filtered and smoothed by a 2200FD/25V capacitor. The resulting supply has the magnitude above 17V. This voltage is fed to the regulator IC 7805. This IC provides a regulated 5V positive supply at its 3rd pin. The required input for this is more than 7.5V. The driving voltage for the relays can be taken from the input of this IC. An ON/OFF switch is provided before the IC in order to switch the system. The logic behind this is the safety. Also there is an LED in series with a 470 resistor. This will act as a power ON indicator

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WORKING

As soon as the power is switched on the C will reset due to the action of power on reset circuitry. This will restore the content of the program counter as 0000H. Now the C will start fetching from this location. The C will switch ON the green signal to the road after the reset pulse is vanished. Also the microcontroller will open the gate. After these operations the system checks the trigger switches, which are kept at the stationmasters room. The logic level at the pin where the switches are connected will be at logic high level due to the action of the internal pull up resistors. The logic level goes to low as soon as the switch connected to than pin is closed. The system then enters in a time loop of 30 Sec ( for right side) and 20 Sec ( for left side). The time count will be decremented after each second. The remaining time will be displayed in the 7-segment displays.. When this loop ends the

C gives an audio warning along with a red signal to the road users. This will last for5 seconds and after this duration the motor is switched on and thereby the gate is closed. Now it is the time to wait for the train.

In order to find the presence the train, the microcontroller analyses the output of the sensors. Whenever the train crosses a sensor, the output of that sensor

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goes to logic high level. This will load the program counter to the initial position where it opens the gate and give green signal to the road. If the output of the first sensor goes high first, the system checks the second sensors output for a logic 1state. After the train crosses the second

sensor, the program counter jumps to the address location 0000h. The gate will be opened and the red light will turned to green light.

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ALGORITHM1. Switch on the green signal in the road and open gate 2. Check the status of the switches. The station master closes any of the two switches depending on the direction of the train If the left switch is found closed then green led is OFF, orange led is ON and wait for 30seconds. This delay is derived from the maximum track speed and the distance between starting station and the gate. Here we are counting this delay in seconds since this is a demonstration project. The delay for right switch may be different. Also display the remaining time. 3. After the time delay turn OFF the orange signal and switch ON the red signal. Switch on the warning alarm. 4. Wait for some time, so that the vehicles on the level cross will get sufficient time to leave the level cross before the gate is closed. 5. close gate 6. Check the sensors fitted on both side of the gate. If the left sensor is found active, then check the right sensor and vice versa. 7. Go to first step if both sensors are activated ,which means the train had crossed the gate.

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GREEN SIGNAL ON GATE OPEN

Is left switch closed? No No Is right switch closed?

Yes

Green LED off and orange LED on Delay for 30 sec Display remaining time

Yes Orange led on , delay for 20sec Display remaining time Display remaining time

Red signal ON Alarm On

Delay for 5 Sec

Close gate No

Is left sensor on?No No

Yes

Is right sensor On?

Yes

No Yes Is left sensor on ? Yes

Is right sensor On ?

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PROGRAM

GRN ORN RED BZR RL1 RL2 SW1 SW2 SN1 SN2 D1S1 D1S2

EQU EQU EQU EQU EQU EQU EQU EQU EQU EQU EQU EQU

P2.0 P2.1 P2.2 P2.5 P2.6 P2.7 P0.0 P0.1 P0.2 P0.3 P1.X P3.X

MAIN PROGRAMORG 0000H MOV P1, #11111111B MOV P3, #11111111B SETB SW1 SETB SW2 SETB SN1 SETB SN2 START: CLR BZR SETB GRN CLR ORN CLR RED SETB RL1 SETB RL2 ACALL DLY ACALL DLY ACALL DLY ACALL DLY CLR RL1 CLR RL2 JNB SW1, TIME1 Buzzer off Green LED On Orange LED Off Red LED Off ; Switch On Motor ; Gate Open ; Delay ; ; ; ;

; Switch Off Motor ; Check Switch1

WAIT:

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JNB SW2, TIME2 SJMP WAIT TIME1: SETB ORN CLR GRN MOV R0, #02H MOV P3, #10010100B MOV P1, #10001000B ACALL DLY ACALL DIS10 AJMP BOTH SETB ORN CLR GRN MOV R0, #03H MOV P3, #11000100B MOV P1, #10001000B ACALL DLY ACALL DIS10

; Check Switch2 ; Repeat Loop ; Orange LED On ; Green LED Off ; 3 ; 0

TIME2:

; 2 ; 0

BOTH:

CLR ORN SETB RED SETB BZR MOV R0, #0FFH ACALL AS12 MOV P1, #11111111B MOV P3, #11111111B SETB RL1 CLR RL2 ACALL DLY ACALL DLY ACALL DLY ACALL DLY CLR RL1 CLR RL2 CLR BZR

; Orange LED Off ; Red LED On ; Buzzer On ; Extra 5secs ; Motor On ; Gate Close

; Switch Off Motor ; Buzzer Off ; Check o/p of first sensor, if ; Check o/p of second sensor, if ; Repeat ; Check Sensors

SN: JNB SN1, SNR1 it is 0 go to SNR1 JNB SN2, SNR2 it is 0 go to SNR2 AJMP SN SNR1: JNB SN1, $ JB SN2, $

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JNB SN2, $ AJMP START SNR2: JNB SN2, $ JB SN1, $ JNB SNI, $ AJMP START

DIS10: AS5:

CJNE R0, #06H, AS6 MOV P3, #11000001B AJMP DIS1 AS6: CJNE R0, #05H, AS7 MOV P3, #11100010B AJMP DIS1 AS7: CJNE R0, #04H, AS8 MOV P3, #11000100B AJMP DIS1 AS8: CJNE R0, #03H, AS9 MOV P3, #10010100B AJMP DIS1 AS9: CJNE R0, #02H, AS10 MOV P3, #11101110 AJMP DIS1 AS10: CJNE R0, #01H, AS11 MOV P3, #10001000B AJMP DIS1 AS11: RET MOV P1, #10110000B CALL DLY MOV P1, #10000000B CALL DLY MOV P1, #10111100B CALL DLY MOV P1, #10000001B CALL DLY MOV P1, #10010001B CALL DLY MOV P1, #10110010B CALL DLY MOV P1, #10010100B CALL DLY MOV P1, #11000100B CALL DLY MOV P1, #10111110B

; 5 ; 4 ; 3 ; 2 ; 1 ; 0

DIS1:

; 9 ; 8 ; 7 ; 6 ; 5 ; 4 ; 3 ; 2 ; 1

AS12:

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CALL DLY MOV P1, #10001000B CALL DLY DJNZ R0, DIS10 RET

; 0

DLY: MOV R4, #20 ; Delay program for 1sec DL1: MOV R3, #200 ; R4, R3, R2 = count for 1 sec, 1000000 DL2: MOV R2, #250 DL3: DJNZ R2, DL3 ; Decrement counts, each decrement will take 1micro sec DJNZ R3, DL2 DJNZ R4, DL1 RET ; Return to the main program END

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PRINTED CIRCUIT BOARD

Printed Circuit Board (PCB) is a piece of art. The performance of an electronic circuit depends on the layout and design of PCB. A PCB mechanically supports and connects components by conductive pathways, etched from copper sheets laminated on to insulated substrate. PCB, are used to rotate electrical currents and signals through copper tracts which are firmly bonded to an insulating base. PCB Fabrication involves the following steps: 1. Drawing the layout of the PCB in a paper. The track layout of the Electronic circuit should be made in such manner that the paths are in easy routes. It is then transferred to a Mylar sheet. The sheet is then touched with black ink. 2. The solder side of the Mylar sheet is placed on the shiny side of the five- Star sheet and is placed in a frame. Then it is exposed to sunlight with Mylar sheet facing the sunlight. 3. The exposed five-star sheet is put in Hydrogen Peroxide solution. Then it is put in hot water and shook till unexposed region becomes transparent. 4. This is put in cold water and then the rough side is stuck on to the silk screen. This is then pressed and dried well. 5. The plastic sheet of the five-star sheet is removed leaving the pattern on the screen. 6. A copper clad sheet is cut to the size and cleaned. This is placed under screen.

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7. As it resistant ink if spread on the screen so that a pattern of tracks and a pad is obtained on a copper clad sheet. It is then dried. 8. The dried sheet is then etched using Ferric Chloride solution (32Baume) till all the unwanted Copper is etched away. Swish the board to keep the each fluid moving. Lift up the PCB and check whether all the unwanted Copper is removed. Etching is done by immersing the marked Copper clad in Ferric Chloride solution. After that the etched sheet is dried. 9. The unwanted resist ink is removed using Sodium Hydroxide solution Holes are then dried.

PCB PARAMETERSCopper thickness Track width Clearance Pad width Pad height Pad shape Pad hole size On board Hole size Base PCB Quality - 72mil (1mm=39.37mils) - 60mil - 60mil - 86mil - 86mil - Oval - 25mil - Through - 0.9mm (36mil) -Paper phenolic, Hylam - FRC4

COMPONENT PLACING

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PCB CIRCUIT

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SOLDERINGSoldering is the process of joining metals by using lower melting point to weld or alloy with

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joining surface.

SOLDERSolder is the joining materials that melts below 427 degree connections between components. The popularly used solders are alloys of tin (Sn) and lead (Pb) that melts below the melting point of tin.

Types: 1. Rosin core:- 60/40 Sn/Pb and 63/67 Sn/Pb solders are the most commontypes used for electronics assembly. These solders are available in various diameters and are most appropriate for small electronics work (0.02-0.05 dia. Is recommended )

2. Lead free:- Lead free solders are used as more environmental-friendlysubstitutes for leaded solder, but they are typically not as easy to use mainly because of their higher melting point and poorer wetting properties.

3. Silver:- Silver solders are typically used for low resistance connections butthey have a higher melting point and are more expensive than sn/Pb solders.

4. Acid-Core:- Acid-Core solders should not be used for electronics. They areintended for plumbing or non-electronics assembly work. The acid core flux will cause corrosion of circuitry and can damage components.

5. Other special solders: Various melting point eutectics: These special solders are typically used for non-electronic assembly of difficult to

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construct mechanical items that must be assembled in a particular sequence.

Paste solders: These solders are used in field applications or in specialized manufacturing application.

FluxIn order to make the surface accept the solder readily, the components terminals should be free Oxides and other obstructing films. The lead should be cleaned chemically or by abrasion using blades or knives. Small amount of lead coating can be done on the portion of the leads using soldering iron. This process is called thinning. Zinc chloride or Ammonium chloride separately or in combination is mostly used as fluxes. These are available in petroleum jelly as paste flux. Flux is a medium used to remove the degree of wetting. The desirable properties of flux are: It should provide a liquid cover over the materials and exclude air gap up to the soldering temperature. It should dissolve any Oxide on the metal surface. It should be easily displaced from the metal by the molten soldering operation. Residues should be removable after completing soldering operation. The most common flux used in hand soldering of electronic components is rosin, a combination of mild organic acids extracted from pine tree.

Soldering Iron

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It is the tool used to melt the solder and apply it at the joint in the circuit. It operates in 230V supply. The iron bit at the tip gets heated while few minutes. The 50W and 25W soldering irons are commonly used for soldering of electronic circuits.

Soldering Steps1. Make the layout of the components in the circuit. Plug in the chord of the soldering iron into the mains to get heated. 2. Straighten and clean the component leads using a blade or a knife. 3. Mount the components on the PCB by bending the leads of the components. Use nose pliers. 4. Apply flux on the joints and solder the joints. Soldering must be done in minimum time to avoid dry soldering and heating up of the components. 5. Wash the residue using water and brush. 6. Solder joints should be inspected when completed to determine if they have been properly made.

Qualities of a good solder joint:A. Shiny surface B. Good, smooth fillet.

Qualities of a poor solder joint:1. Dull or crystallized surfaces:- this is an indicator of a cold solder joint. Cold solder joint result from moving the components after the soldering has been removed, but

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before the solder has hardened. Cold solder joints may work at first, but will eventually fail. 2. Air pockets:- Air pockets (voids) result from incomplete wetting of surfaces, allowing air to be in contact with the connecting metals. This will cause oxidation of the joint and eventual failure. Blowholes can occur due to vaporization of the moisture on the surface of the board and existing through the molten solder. Boards should be clean and dry prior to soldering. Ethanol (100%) can be used as a moisture chaser if boards are wet prior to soldering. 3. Dimples:- Dimples in the surface do not always indicate a serious problem, but they should be avoided since they are precursors to voids. 4. Floaters:- Black spots floating in the soldering fillet should be avoided because they indicate contamination and a potential for failure as in the case of voids. These black spots usually result from overheated (burnt) Rosin or other contaminants such as burnt wire insulation. Maintaining a clean tip will help to avoid these problems. 5. Balls:- A solder ball, instead of a fillet can occur if the trace was heated but the lead was not (vice versa). This prevents proper wetting of both surfaces and result in solder being attached to only one surface (component or trace). 6. Excess solder:- Excess solder usage can cover up other potential problems and should be avoided. It can also lead to solder bridges. In addition, spherical solder joints can result from the application of too much solder.

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COMPONENT LIST AND COST ESTIMATE

COMPONENTSCapacitor 1uf Capacitor 33pf Capacitor 2200uf Capacitor 10uf Resistor 5.6k Resistor 180ohm Resistor 10k Crystal 12MHz Display LT542 AT89C51 ULN2003 LED

QUANTITY1 2 2 1 4 1 1 1 2 1 1 3 1 .20 6 1 .15 .15 .15 6 6 40 8 1

PER COST1 .40 12 1 .6 .15 .15 6 12 40 8 3

COST

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Relay Buzzer Switches Sensor L78XX Rectifier Transformer 12v Ribbon connectors Pcb Total

1 1 2 2 2 1 1 4

60 30 8 5 9 15 100 3 250 Rs 595

60 30 16 10 18 15 100 12 250

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CONCLUSION

We can conclude that the device is so simple and user friendly. It takes over the task of controlling the railway gate systems .It may not be out of place to mention that by adding additional features supported by advanced on board computers the power of the system can be enhanced to suit multiple tracks and multiple roads. The system devised will be very cost effective and hundred percent full proof and will be extremely efficient In comparison to manual systems.

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REFERENCE

Micro controller architecture, programming, applications, with 8051 -By Kenneth J Ayala second edition Cmos Data book Digital Principles and Applications- By Malvino and Leach Data sheet links www.atmel.com www.st.com

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