Prototype Rf Controlled Unmanned Railway Gate Control

PROTOTYPE RF CONTROLLED UNMANNED RAILWAY GATE CONTROL

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1. INTRODUCTION

College Of Engineering, Chengannur


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1. INTRODUCTIONRailways have provided railway gates for safety at the level crossings. These gates are closed for road traffic when a train is expected to arrive on the track. The gates are opened for road users once the train levels the crossing. Level crossing in India can be divided into two categories. Manned Un- Manned Manned level crossings are those which are guarded by a gatemen as employee of Railways. The gate inhibits the Road traffic by closing the gate on the receipt of approaching train information from control cabin through a telephone line. Also in this type of system the engine driver obtains a green signal only when the railway gate is closed. Most of the level crossings nearer to Railway station or in rural areas are manned. Un-Manned level crossings are places which are un-guarded. Therefore a slight amount of negligence on the part of road users leads to accidents at such places. Most of the crossings in remote areas or villages with low population density are of un-manned type. It may be worth mentioning here that most of train accidents leading to loss of property and life occurred at un-manned level crossings. But of course warning all level crossings in the vast network of Indian Railways is practically impossible. Accidents did occur even at manned level crossings due to the errors committed by gateman. An idea has been given by us in overcoming this problem of accidents at Railway gates. The advantage of this system is that human error is eliminated. The problem of accident risks at un-manned level crossings is solved. Financial burden on railway is reduced due to reduction of manpower.



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2. BLOCK DIAGRAM



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2.1 TRANSMITTER SECTION POWER SUPPLY

ENCODER IC

RF TRANSMITTE R

Figure.1 2.2 RECEIVER SECTIONGATE CONTROL SWITCHES

DC MOTOR

POWER SUPPLY

MOTOR DRIVER IC

RF RECEIVER DECODER IC PIC MICROCONTROLLER

ALARM SIGNAL LIGHTS MODE SELECT

Figure.2

GATE SENSOR SWITCHES



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3. BLOCK DIAGRAM DESCRIPTION



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3. BLOCK DIAGRAM DESCRIPTIONThe railway gate control system consists of the following functional blocks: Power supply unit RF Transmitter and Receiver Encoder and decoder section Microcontroller Gate control unit Signal lights and alarm Gate control and sensor switches

3.1 POWER SUPPLY: It converts ac voltage of the main supply into dc voltage. Generally it consists of a transformer, followed by a rectifier, smoothing filter and a voltage regulator circuit. The LM7805 ICs are used to produce regulated voltages of +5V at the output.

3.2 RF TRANSMITTER AND RECEIVER: The RF module, as the name suggests, operates at Radio frequency. The corresponding frequency range varies between 30 kHz & 300 GHz. In this RF system, the digital data is represented as variations in the amplitude of carrier wave. This kind of modulation is known as Amplitude Shift Keying (ASK). Transmission through RF is better than IR (infrared) because of many reasons. Firstly, signals through RF can travel through larger distances making it suitable for long range applications. Also, while IR mostly operates in line-of-sight mode, RF signals can travel even when there is an obstruction between transmitter & receiver. Next, RF transmission is more strong and reliable than IR transmission. RF communication uses a specific frequency unlike IR signals which are affected by other IR emitting sources.



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This RF module comprises of an RF Transmitter and an RF Receiver. The transmitter/receiver (Tx/Rx) pair operates at a frequency of 433 MHz. An RF transmitter receives serial data and transmits it wirelessly through RF through its antenna connected. The transmission occurs at the rate of 1Kbps - 10Kbps.The transmitted data is received by an RF receiver operating at the same frequency as that of the transmitter.

3.3 ENCODER AND DECODER SECTION: The RF module is often used along with a pair of encoder/decoder. The encoder is used for encoding parallel data for transmission feed while reception is decoded by a decoder. The encoder decoder ICs used here is HT12E-HT12D, which belongs to Holteks 212 series. The 212 encoders and decoders are a series of CMOS LSIs for remote control system applications.

3.4 MICROCONTROLLER: The microcontroller used here is PIC16F877A which is a CMOS FLASHbased 8-bit microcontroller and is upward compatible with the PIC16C5x, PIC12Cxxx and PIC16C7x devices. It features 200 ns instruction execution, 256 bytes of EEPROM data memory, self programming, an ICD, 2 Comparators, 5 channels of 10-bit Analog-to-Digital (A/D) converter, 2 capture/compare/PWM functions, a synchronous serial port that can be configured as either 3-wire SPI or 2-wire I2C bus, and a USART.

3.5 GATE CONTROL UNIT: This unit comprises of DC motor and its driver circuit. 3.5.1 DC Motor: DC motors convert electrical energy into mechanical motion. These motors rotate based on the polarity of the input voltage. Every DC motor has six basic parts -axle, rotor, stator, commutator, field magnet(s), and brushes. In most common DC motors eternal magnetic field is produced by high-strength permanent magnets. The



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stator is the stationary part of the motor -- this includes the motor casing, as well as two or more permanent magnet pole pieces. The rotor (together with the axle and attached commutator) rotate with respect to the stator. The rotor consists of windings (generally on a core), the windings being electrically connected to the commutator.

3.5.2 DC Motor Driver Circuitry: 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 solenoides, 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 packaage which has 4 center pins connected together and used for heatsinking 3.6 SIGNAL LIGHTS AND ALARM: This section consists of a pair of red and green LEDs to provide warnings for both road users and train. A Buzzer alarm is also provided at the gate side which sounds a warning in the form of an intermittent beeping sound prior to the train arrival. 3.7 GATE CONTROL SWITCHES: Two sensor switches are provided to get feedback for proper opening and closing of gate. Two additional control switches are also included for manual operation of gate for more flexibility.



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4. CIRCUIT DIAGRAM



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4.1 TRANSMITTER SECTION

Figure.3



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4.2 RECEIVER SECTION

Figure.4



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5. CIRCUIT DIAGRAM EXPLANATION



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5. CIRCUIT DIAGRAM EXPLANATIONThe circuit consists of two sections, transmitter section which is placed in train and receiver section which is placed near the railway gate. It has two mode of operation namely automatic mode (normal mode) and manual mode.

5.1 AUTOMATIC MODE The transmitter section consists of an RF transmitter module operating at 433MHz and an encoder IC HT12E which is used as a binary pattern generator. The HT12E has 8 address pins and 4 data pins. We can select a particular pattern by giving VDD or ground potential to the corresponding pins. This pattern is transmitted via an RF transmitter antenna as long as the Transmission Enable pin (TE) of HT12E is held LOW. The transmission rate is 4kB/sec. The digital data is represented as variations in the carrier amplitude. This kind of modulation is called Amplitude Shift Keying (ASK). Transmission through RF is better than IR (infrared) because of many reasons. Firstly, signals through RF can travel through larger distances making it suitable for long range applications. Also, while IR mostly operates in line-of-sight mode, RF signals can travel even when there is an obstruction between transmitter & receiver. Next, RF transmission is more strong and reliable than IR transmission. RF communication uses a specific frequency unlike IR signals which are affected by other IR emitting sources. Transmitted data is received by an RF receiver operating at the same frequency as that of transmitter. The received serial data is fed to the Data In pin of the HT12D IC and the address pins are made identical to that in HT12E. The decoded data bits appear at the data pins 10, 11, 12, and 13 of HT12D.The Valid Transmission output of HT12D is fed as the input to the microcontroller. Upon receiving the data, microcontroller alerts the road users regarding the arrival of train by using buzzer and proper Traffic lights. When the alarms and signal



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lights are given, a time delay is provided after which the gate is closed. Time delay is employed for the passage of the road users who were in the track at the time of detection of train. When the train leaves the range of RF module, the Valid Transmission pin goes LOW. Now the gate is opened and the signal lights are set to initial condition. Two sensor switches are provided to get the feedback that gate is closed/opened properly. The DC motor which is used for gate operation is interfaced through a motor driver IC L293D, whose absolute maximum output current is 1.2A.

5.2 MANUAL MODE In this mode of operation, the gate is controlled manually by switches. The sensor switches provide the feedback that gate is closed/opened perfectly. Upon pressing CLOSE SWITCH the gate closes and when the CLOSE SENSOR is pressed indicating that the gate is closed, gate operation is stopped. For opening the gate, the OPEN SWITCH is pressed and when the OPEN SENSOR is pressed further gate opening is stopped.



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6. FLOWCHART



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6. FLOWCHART

Start

Make initial settings for traffic light and alarm G

Is mode = AUTO? YES NO Is train coming? YES Give alarmvncnvcjfjjfjchcvhjcvjhc

NO A

Turn ON RED signal for road

Call delay C Close the gate

B



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B

Is Close Sensor pressed?

NO C

YES Stop closing the gate

Turn ON GREEN signal for train

NO

Has train departed?

YES Open gate n

Is Open Sensor pressed?

NO

YES D



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D

Stop opening the gate

Turn ON GREEN signal for road and RED signal for train A

Is Open Switch pressed?

NO

E

YES Open gate n

Is Open Sensor pressed?

NO

YES Stop opening the gate

Turn ON RED signal for train

F



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F E

Is Close Switch pressed?

NO G

YES Close gate n

Is Close Sensor pressed?

NO

YES Stop closing the gate

Turn ON GREEN signal for train

G



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7. COMPONENT DESCRIPTION



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7. COMPONENT DESCRIPTIONThe Main components are: 1. ENCODER IC - HT12E 2. DECODER IC - HT12D 3. SHORT RANGE RF TRANSMITTER AND RECEIVER MODULES 4. PIC 16F877A 5. L293D 6. DC MOTOR 7. LED 8. BUZZER

7.1 HT12E General Description The 212 encoders are a series of CMOS LSIs for remote control system applications. They are capable of encoding information which consists of N address bits and 12-N data bits. Each address/data input can be set to one of the two logic states. The programmed addresses/data are transmitted together with the header bits via an RF or an infrared transmission medium upon receipt of a trigger signal.

Figure.5



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The capability to select a TE trigger on the HT12E or a DATA trigger on the HT12A further enhances the application flexibility of the 212 series of encoders. The HT12A additionally provides a 38 kHz carrier for infrared systems. Features Operating voltage 2.4V~5V for the HT12A 2.4V~12V for the HT12E Low power and high noise immunity CMOS technology Low standby current: 0.1A (typ.) at VDD=5V HT12A with a 38 kHz carrier for infrared transmission medium Minimum transmission word Four words for the HT12E One word for the HT12A Built-in oscillator needs only 5% resistor Data code has positive polarity Minimal external components

7.2 HT12D General Description These decoders are a series of CMOS LSIs for remote control system applications. They are paired with Holteks 212 series of encoders. For proper operation, a pair of encoder/decoder with the same number of addresses and data format should be chosen. The decoders receive serial addresses and data from a programmed 212 series of encoders that are transmitted by a carrier using an RF or an IR transmission medium. They compare the serial input data three times continuously with their local addresses. If no error or unmatched codes are found, the input data codes are decoded and then transferred to the output pins. The VT pin also goes high to indicate a valid transmission. The 2 12 series of decoders are capable of decoding informations that consist of N bits of address and 12-N bits of data. Of this series, the



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HT12D is arranged to provide 8 address bits and 4 data bits, and HT12F is used to decode 12 bits of address information. Features Operating voltage: 2.4V~12V Low power and high noise immunity CMOS technology Low standby current Capable of decoding 12 bits of information Binary address setting Received codes are checked 3 times Address/Data number combination HT12D: 8 address bits and 4 data bits HT12F: 12 address bits only Built-in oscillator needs only 5% resistor Valid transmission indicator Easy interface with an RF or an infrared transmission medium Minimal external components Pair with Holteks 212 series of encoders 18-pin DIP, 20-pin SOP package Figure.6

7.3 RF MODULE

7.3.1 Transmitter Module Model: FS 1000 A Range LOS, Open Ground: 80m Working Voltage: 3 12 V Dimension: 22mm X 23mm Working Current: 10 15 mA Working Mode: AM Transport Speed: 4KB/S Transmit Frequency: 315/433 MHz Figure.7



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Transmit Power: 10mW External Antenna: 315 MHz (use 25 cm normal cores or single core wire)

7.3.2 Receiver Module Model: PCR 2 A Receive Sensitivity: -95 dbm Working Voltage: 5 V Dimension: 37mm X 16mm Receive Frequency: 315/433 MHz External Antenna: 18 25 cm Transport Speed: 4KB/S Working Temperature: -10 to +70 Working Current: 0.5 0.8 mA Figure.8

7.4 PIC 16F877A High performance RISC CPU Only 35 single word instructions All single instruction except for program branches which are two cycle Operating speed: DC - 20 MHZ clock input DC - 200ns instruction cycle Up to 8k 14 words of FLASH program memory, up to 368 8 bytes of data memory (RAM) up to 256 8 bytes of EEPROM data memory Pin out compatible to the PIC 16F873/74/76 interrupt capability (up to 14 internal/external interrupt sources) Eight level deep hardware stack Direct, indirect, and relative addressing modes Power On Reset (POR),Power up Timer (PWRT) AND Oscillator Start up Timer(OST) Watchdog Timer (WDT) with its own on chip RC oscillator for reliable operation Programmable code protection Power saving SLEEP mode Selectable oscillator options Low power ,high speed CMOS FLASH/EEPROM technology



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Fully static design In circuit serial programming via two pins Only single 5V source needed for programming In Circuit Debugging via two pins Processor read/write access to program memory Wide operating voltage range : 2.0V to 5.5V

Figure.9 7.5 L293D 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 solenoides, DC and stepping motors) and switching power transistors.

Figure.10



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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 packaage which has 4 center pins connected together and used for heatsinking 7.6 DC MOTOR: At the most basic level, electric motors exist to convert electrical energy into mechanical energy. This is done by way of two interacting magnetic fields -- one stationary, and another attached to a part that can move. A number of types of electric motors exist, but most BEAMbots use DC motors in some form or another. DC motors have the potential for very high torque capabilities (although this is generally a function of the physical size of the motor), are easy to miniaturize, and can be "throttled" via adjusting their supply voltage. DC motors are also not only the simplest, but the oldest electric motors. The basic principles of electromagnetic induction were discovered in the early 1800's by Oersted, Gauss, and Faraday. By 1820, Hans Christian Oersted and Andre Marie Ampere had discovered that an electric current produces a magnetic field. The next 15 years saw a flurry of cross-Atlantic experimentation and innovation, leading finally to a simple DC rotary motor. A number of men were involved in the work, so proper credit for the first DC motor is really a function of just how broadly you choose to define the word "motor." DC motors convert electrical energy into mechanical motion. These motors rotate based on the polarity of the input voltage. Every DC motor has six basic parts -axle, rotor, stator, commutator, field magnet(s), and brushes. In most common DC motors eternal magnetic field is produced by high-strength permanent magnets. The stator is the stationary part of the motor -- this includes the motor casing, as well as two or more permanent magnet pole pieces. The rotor (together with the axle and attached commutator) rotate with respect to the stator. The rotor consists of windings (generally on a core), the windings being electrically connected to the commutator. In real life DC motors will always have more than two poles (three is a very common number). In particular, this avoids "dead spots" in the commutator. You can imagine how with our example two-pole motor, if the rotor is exactly at the middle of its rotation (perfectly aligned with the field magnets), it will get "stuck" there. Meanwhile, with a two-pole motor, there is a moment where the commutator shorts out the power supply (i.e., both brushes touch both commutator contacts simultaneously). This would be bad for the power supply, waste energy, and damage motor components as well. Yet another disadvantage of such a simple motor is that it would exhibit a high amount of torque "ripple" (the amount of torque it could produce is cyclic with the position of the rotor).



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Types of DC Motors Permanent Magnet Motors The permanent magnet motor uses a magnet to supply field flux. Permanent magnet DC motors have excellent starting torque capability with good speed regulation. A disadvantage of permanent magnet DC motors is they are limited to the amount of load they can drive. These motors can be found on low horsepower applications. Another disadvantage is that torque is usually limited to 150% of rated torque to prevent demagnetization of the permanent magnets. Series Motors In a series DC motor the field is connected in series with the armature. The field is wound with a few turns of large wire because it must carry the full armature current. A characteristic of series motors is the motor develops a largeamount of starting torque. However, speed varies widelybetween no load and full load. Series motors cannot be used where a constant speed is required under varying loads. Additionally, the speed of a series motor with no load increases to the point where the motor can become damaged. Some load must always be connected to a series-connected motor. Series-connected motors generally are not suitable for use onmost variable speed drive applications. Shunt Motors In a shunt motor the field is connected in parallel (shunt) with the armature windings. The shunt-connected motor offers good speed regulation. The field winding can be separately excited or connected to the same source as the armature. An advantage to a separately excited shunt field is the ability of a variable speed drive to provide independent control of the armature and field. The shuntconnected motor offers simplified control for reversing. This is especially beneficial in regenerative drives. Compound Motors Compound motors have a field connected in series with the armature and a separately excited shunt field. The series field provides better starting torque and the shunt field provides better speed regulation. However, the series field can cause control problems in variable speed drive applications and is generally not used in four quadrant drives.



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8.SOFTWARES



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8. SOFTWARES MikroCMikroC is a powerful, feature rich development tool for PICmicros. It is designed to provide the programmer with the easiest possible solution for developing applications for embedded systems, without compromising performance or control. PIC and C fit together well: PIC is the most popular 8-bit chip in the world, used in a wide variety of applications, and C, prized for its efficiency, is the natural choice for developing embedded systems. mikroC provides a successful match featuring highly advanced IDE, ANSI compliant compiler, broad set of hardware libraries, comprehensive documentation, and plenty of ready-to-run examples.

Figure.11

OrCAD OrCAD is a proprietary software tool suite used primarily for electronic design automation. The software is used mainly to create electronic prints for manufacturing of printed circuit boards, by electronic design engineers and electronic technicians to manufacture electronic schematics and diagrams, and for their simulation. The name OrCAD is a portmanteau, reflecting the software's origins: Oregon + CAD.



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The OrCAD product line is fully owned by Cadence Design Systems. The latest iteration has the ability to maintain a database of available integrated circuits. This database may be updated by the user by downloading packages from component manufacturers, such as Analog Devices or Texas Instruments. Another announcement was, that ST Microelectronics will offer OrCAD PSpice models for all the power and logic semiconductors, since PSpice is the most used circuit simulator. Intel offers reference PCBs designed with Cadence PCB Tools in the OrCAD Capture format for embedded and personal computers.

Figure.12



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9. PCB FABRICATION



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PCB PREPARATION TECHNIQUES You need to generate a positive (copper black) UV translucent artwork film. You will never get a good board without good artwork, so it is important to get the best possible quality at this stage. The most important thing is to get a clear sharp image with a very solid opaque black. Nowadays, artwork is drawn using either a dedicated PCB CAD program or a suitable drawing/graphics package. It is absolutely essential that your PCB software prints holes in the middle of pads, which will act as center marks when drilling. It is virtually impossible to accurately hand-drill boards without these holes. If youre looking to buy PCB software at any cost level and want to do hand-prototyping of boards before production, check that this facility is available. If youre using a general-purpose CAD or graphics package, define pads as either a grouped object containing a black-filled circle with a smaller concentric white-filled circle on top of it, or as an unfilled circle with a thick black line (i.e. a black ring). When defining pad and line shapes, the minimum size recommended for vias (through-linking holes) for reliable results is 50mil, assuming 0.8mm drill size; 1mil = (1/1000)th of an inch. You can go smaller with smaller drill sizes, but throughlinking will be harder. 65mil round or square pads for normal components and DIL ICs, with 0.8mm hole, will allow a 12.5mil, down to 10mil if you really need to. Centre-to-centre spacing of 12.5mil tracks should be 25mil slightly less may be possible if your printer can manage it. Take care to preserve the correct diagonal track-track spacing on mitered corners; grid is 25mil and track width 12.5mil. The artwork must be printed such that the printed side is in contact with the PCB surface when exposing, to avoid blurred edges. In practice, this means that if you design the board as seen from the component side, the bottom (solder side) layer should be printed the correct way round, and the top side of a double-sided board must be printed mirrored.



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Media Artwork quality is very dependent on both the output device and the media used. It is not necessary to use a transparent artwork medium as long as it is reasonably translucent to UV, its fine-less translucent materials may need a slightly longer exposure time. Line definition, black opaqueness and toner/ink retention are much more important. Tracing paper has good enough UV translucency and is nearly as good as drafting film for toner retention. It stays flatter under laser-printer heat than polyester or acetate film. Get the thickest you can find as thinner stuff can crickle. It should be rated at least 90gsm; 120gsm is even better but harder to find. It is cheap and easily available from office or art suppliers.

Output devices Laser printers offer the best all-round solution. These are affordable, fast, and good-quality. The printer used must have at least 600dpi resolution for all but the simplest PCBs, as you will usually be working in multiples of 0.06cm (40 tracks per inch). 600 dpi divides into 40, so you get consistent spacing and line width. It is very important that the printer produces a good solid black with no toner pinholes. If youre planning to buy a printer for PCB use, do some test prints on tracing paper to check the quality first. If the printer has a density control, set it to the blackest. Even the best laser printers dont generally cover large areas well, but usually this isnt a problem as long as fine tracks are solid. When using tracing paper or drafting film, always use manual paper feed and set the straightest possible paper output path to keep the artwork as flat as possible and minimize jamming. For small PCBs, you can usually save paper by cutting the sheet in half. You may need to specify a vertical offset in your PCB software to make it print on the right part of the page. Some laser printers have poor dimensional accuracy, which can cause problems for large PCBs. But as long as any error is linear, it can be compensated by scaling the printout in software. Print accuracy is likely to be a noticeable problem when it causes misalignment of the sides on double-sided PCBs this can usually be avoided by careful arrangement of the plots on the page to ensure the error is the same on both



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layers; for example, choosing whether to mirror horizontally or vertically when reversing the top-side artwork. Photo resist PCB laminates Always use good-quality, pre-coated photo resist fiberglass (FR4) board. Check carefully for scratches in the protective covering and on the surface after peeling off the covering. You dont need darkroom or subdued lighting when handling boards, as long as you avoid direct sunlight, minimize unnecessary exposure, and develop immediately after UV exposure. Instagraphic Microtrak board develops really quickly, gives excellent resolution, and is available in thin (0.8mm) and heavy copper flavors. On using spray-on photo resist, you will always get dust settling on the wet resist. So it is not recommended unless you have access to a very clean area or drying oven, or you only want to make low-resolution PCBs.

Exposure The photo resist board needs to be exposed to UV light through the artwork, using a UV exposure box. UV exposure units can easily be made using standard fluorescent lamp ballasts and UV tubes. For small PCBs, two or four 8W, 30.5cm tubes will be adequate. For larger (A3) units, four 38cm tubes are ideal. To determine the tube-to-glass spacing, place a sheet of tracing paper on the glass and adjust the distance to get the most even light level over the surface of the paper. Even illumination is a lot easier to obtain with 4-tube units. The UV tubes you need are sold as replacements for UV exposure units, black light tubes for disco lighting, etc. These look white, occasionally black/blue when off, and light up with a light purple. Do not use short-wave UV lamps like EPROM eraser tubes and germicidal lamps that have clear glass, because these emit short-wave UV which can cause eye and skin damage. A timer that switches off the UV lamps automatically is essential, and should allow exposure times from 2 to 10 minutes in 15 to 30 second increments. It is useful if the timer has an audible indication when the timing period has completed. A timer from a scrap microwave oven would be ideal. Use glass sheet rather than plastic for the top of the UV unit, as it will flex less and be less prone to scratches. A combined unit, with switchable UV and white tubes, doubles as an exposure unit and a light-box for lining up double sided artworks. If you do a lot of double-sided PCBs, it may be



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worth making a double-sided exposure unit, where the PCB can be sandwiched between two light sources to expose both sides simultaneously. To find the required exposure time for a particular UV unit and laminate type, expose a test piece in 30 second increments from 2 to 8 minutes, develop, and use the time which gave the best image. Generally speaking, overexposure is better than underexposure. For a single sided PCB, place the artworks toner side up on the UV box glass, peel off the protective film from the laminate, and place its sensitive side down on top of the artwork. The laminate must be pressed firmly down to ensure good contact all over the artwork. To expose double sided PCBs, print the solder side artwork as normal and the component side mirrored. Place the two sheets together with the toner sides facing, and carefully line them up, checking all over the board area for correct alignment, using the holes in the pads as a guide. A light box is very handy here, but exposure can also be done with daylight by holding the sheets on the surface of a window. If printing errors have caused slight mis-registration, align the sheets to average the errors across the whole PCB, to avoid breaking pad edges or tracks when drilling. When these are correctly aligned, staple the sheets together on two opposite sides, about 10 mm from the edge of the board, forming a sleeve or envelope. The gap between the board edge and staples is important to stop the paper distorting at the edge. Use the smallest stapler you can find, so that the thickness of the staple is not much more than that of the PCB. Expose each side, covering up the top side with a reasonably light-proof soft cover when exposing the underside. Be very careful when turning the board over, to avoid the laminate slipping inside the artwork and ruining the alignment. After exposure, you can usually see a faint image of the pattern in the photosensitive layer.

Developing Do not use sodium hydroxides for developing photo resist laminates. It is a completely and utterly dreadful stuff for developing PCBs. Apart from its causticity, it is very sensitive to both temperature and concentration, and made-up solution doesnt last long. When its too weak it doesnt develop at all, and when too strong it strips all the resist off. It is almost impossible to get reliable and consistent results, especially when making PCBs in an environment with large temperature variations. A much



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better developer is a silicate based product that comes as a liquid concentrate. You can leave the board in it for several times the normal developing time without noticeable degradation. This also means that it is not temperature critical - no risk of stripping at warmer temperatures. Made-up solution also has a very long shelf-life and lasts until its used up. You can make the solution up really strong for very fast developing. The recommended mix is 1 part developer to 9 parts water. You can check for correct development by dipping the board in the ferric chloride very brieflythe exposed copper should turn dull pink almost instantly. If any shiny copper-colored areas remain, rinse and develop for a few more seconds. If the board is under-exposed, you will get a thin layer of resist which isnt removed by the developer. You can remove this by gently wiping with dry paper towel, without damaging the pattern. You can either use a photographic developing tray or a vertical tank for developing.

Etching Ferric chloride etchant is a messy stuff, but easily available and cheaper than most alternatives. It attacks any metal including stainless steel. So when setting up a PCB etching area, use a plastic or ceramic sink, with plastic fittings and screws wherever possible, and seal any metal screws with silicone. Copper water pipes may get splashed or dripped-on, so sleeve or cover them in plastic; heat-shrink sleeving is great if youre installing new pipes. Fume extraction is not normally required, although a cover over the tank or tray when not in use is a good idea. You should always use the hex hydrate type of ferric chloride, which should be dissolved in warm water until saturation. Adding a teaspoon of table salt helps to make the etchant clearer for easier inspection. Avoid anhydrous ferric chloride. It creates a lot of heat when dissolved. So always add the powder very slowly to water; do not add water to the powder, and use gloves and safety glasses. The solution made from anhydrous ferric chloride doesnt etch at all, so you need to add a small amount of hydrochloric acid and leave it for a day or two. Always take extreme care to avoid splashing when dissolving either type of ferric chloride, as it tends to clump together and you often get big chunks coming out of the container and splashing into the solution. It can damage eyes and permanently stain clothing. If youre making PCBs in a professional



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environment, where time is money, you should get a heated bubble-etch tank. With fresh hot ferric chloride, a PCB will etch in well under five minutes. Fast etching produces better edge-quality and consistent line widths. If you arent using a bubble tank, you need to agitate frequently to ensure even etching. Warm the etchant by putting the etching tray inside a larger tray filled with boiling water.

Tin plating Tin-plating a PCB makes it a lot easier to solder, and is pretty much essential for surface mount boards. Unless you have access to a roller tinning machine, chemical tinning is the only option. Unfortunately, tin-plating chemicals are expensive but the results are usually worth it. If you dont tin-plate the board, either leave the photo resist coating on (most resists are intended to act as soldering fluxes) or spray the board with rework flux to prevent the copper from oxidizing. Roomtemperature tin-plating crystals produce a good finish in a few minutes. There are other tinning chemicals available, some of which require mixing with acid or hightemperature use. Ensure that the temperature of the tinning solution is at least 25C, but not more than 40C. If required, either put the bottle in a hot water bath or put the tinning tray in a bigger tray filled with hot water to warm it up. Putting a PCB in cold tinning solution will usually prevent tinning, even if the temperature is subsequently raised. For a good tinned finish, strip the photo resist thoroughly. Although you can get special stripping solutions and hand applicators, most resists can be dissolved off more easily and cleanly using methanol (methylated spirit). Hold the rinsed and dried PCB horizontal, and dribble few drops of methanol on the surface, tilting the PCB to allow it to run over the whole surface. Wait for about ten seconds and wipe off with a paper towel dipped in methanol. Rub the copper surface all over with wire wool until it is bright and shiny. Wipe with a paper towel to remove the wire wool fragments and immediately immerse the board in the tinning solution. Dont touch the copper surface after cleaning, as finger marks will impair plating. The copper should turn silver in color within about 30 seconds. Leave the board for about five minutes, agitating occasionally; do not use bubble agitation. For double-sided PCBs prop the PCB at an angle to ensure the solution gets to both sides. Rinse the board thoroughly and rub dry with paper towel to remove any tinning crystal deposits. If the board isnt



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going to be soldered for a day or two, coat it with either a rework flux spray or a flux pen. Drilling If you have fiberglass (FR4) board, you must use tungsten carbide drill bits. Fiberglass eats normal high-speed steel (HSS) bits very rapidly, although HSS drills are all right for odd larger sizes (>2 mm). Carbide drill bits are expensive and the thin ones snap very easily. When using carbide drill bits below 1 mm, you must use a good vertical drill standyou will break drill very quickly without one. Carbide drill bits are available as straight-shank or thick (sometimes called turbo) shank. In straight shank, the whole bit is the diameter of the hole, and in thick shank, a standard-size (typically about 3.5 mm) shank tapers down to the hole size. The straight-shank drills are usually preferred because they break less easily and are usually cheaper. The longer thin section provides more flexibility. Small drills for PCB use usually come with either a set of collets of various sizes or a 3-jaw chuck. Sometimes the 3-jaw chuck is an optional extra and is worth getting for the time it saves on changing collets. For accuracy, however, 3-jaw chucks arent brilliant, and small drill sizes below 1 mm quickly form grooves in the jaws, preventing good grip. Below 1 mm, you should use collets, and buy a few extra of the smallest ones; keeping one collet per drill size, as using a larger drill in a collet will open it out and it no longer grips smaller drills well. You need a good strong light on the board when drilling, to ensure accuracy. A dichroic halogen lamp, under-run at 9V to reduce brightness, can be mounted on a microphone gooseneck for easy positioning. It can be useful to raise the working surface about 15 cm above the normal desk height for more comfortable viewing. Dust extraction is nice, but not essentialan occasional blow does the trick! A foot-pedal control to switch the drill off and on is very convenient, especially when frequently changing bits. Avoid hole sizes less than 0.8 mm unless you really need them. When making two identical boards, drill them both together to save time. To do this, carefully drill a 0.8mm hole in the pad near each corner of each of the two boards, getting the centre as accurate as possible. For larger boards, drill a hole near the centre of each side as well. Lay the boards on top of each other and insert a 0.8mm track pin in two opposite corners, using the pins as pegs to line the PCBs up. Squeeze or hammer the pins into the boards, and then into the remaining holes. The two PCBs are now nailed together accurately and can be drilled together



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Cutting A small guillotine is the easiest way to cut fiberglass laminate. Ordinary saws (band saws, jigsaws, and hacksaws) will be blunted quickly unless these are carbidetipped, and the dust can cause sink irritation. A carbide tile-saw blade in a jigsaw might be worth a try. Its also easy to accidentally scratch through the protective film when sawing, causing photo resist scratches and broken tracks on the finished board. A sheet-metal guillotine is also excellent for cutting boards, provided the blade is fairly sharp. To make cut-outs, drill a series of small holes, punch out the blank, and file to size. Alternatively, use a fretsaw or small hacksaw, but be prepared to replace blades often. With practice its possible to do corner cutouts with a guillotine but you have to be very careful that you dont over-cut.



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10. SOLDERING AND CASING



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10. SOLDERING AND CASINGSOLDERING Soldering is the joining together of two metals to give physical bonding and good electrical conductivity. It is used primarily in electrical and electronic circuitry. Solder is a combination of metals, which are solid at normal room temperatures and become liquid at between 180 and 200C. Solder bonds well to various metals, and extremely well to copper. Soldering is a necessary skill you need to learn to successfully build electronic circuits. It is the primary way how electronics components are connected to circuit boards, wires and sometimes directly to other components. To solder you need a soldering iron. A modern basic electrical soldering iron consists of a heating element, a soldering bit (often called the tip), a handle and a power cord. The heating element can be either a resistance wire wound around a ceramic tube, or a thick film resistance element printed onto a ceramic base. The element is then insulated and placed into a metal tube for strength and protection. This is then thermally insulated from the handle. The heating element of soldering iron usually reaches temperatures of around 370 to 400C (higher than needed to melt the solder). The soldering bit is a specially shaped piece of copper plated with iron and then usually plated with chrome or iron. The tip planting makes it very resistant to aggressive solders and fluxes. The strength or power of a soldering iron is usually expressed in Watts. Irons generally used in electronics are typically in the range 12 to 25 Watts. Higher powered iron will not run hotter, but it will have more power available to quickly replace heat drained from the iron during soldering. Most irons are available in a variety of voltages, 12V, 24V, 115V, and 230V are the most popular. Today most laboratories and repair shops use soldering irons, which operate at 24V (powered by isolation transformer supplied with the soldering iron or by a separate low voltage outlet). You should always use this low voltage where possible, as it is much safer. For advanced soldering work (like very tiny very sensitive electronics components),



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you will need a soldering iron with a temperature control. In this type of soldering irons the temperature may be usually set between 200C and 450C . Many temperature-controlled soldering irons designed for electronics have a power rating of around 40-50W. They will heat fast and give enough power for operation, but are mechanically small (because the temperature controller stops them from overheating when they are not used). You will occasionally see gas-powered soldering irons which use butane rather than the mains electrical supply to operate. They have a catalytic element which, once warmed up, continues to glow hot when gas passes over them. Gaspowered soldering irons are designed for occasional "on the spot" use for quick repairs, rather than for mainstream construction or assembly work. You need to be careful in soldering because most electronic components are fragile, and heat sensitive. Usually our biggest concern is heat. Low enough soldering temperature and short enough soldering time keeps components in good shape. Electronics components are designed so that they can take high temperatures on their contacts/wires for some time without damage (to withstand the soldering). Prolonged exposure to high temperature will heat up when inside of the component can cause damage to it. Currently, the best commonly available, workable, and safe solder alloy is 63/37. That is, 63% lead, 37% tin. It is also known as eutectic solder. Its most desirable characteristic is that its solids ("pasty") state and its liquid state occur at the same temperature 361F. The combination of 63% lead and 37% tin melts at the lowest possible temperature. Nowadays there is tendency to move to use lead free solders, but it will takes years until they will catch on normal soldering work. Lead free solders are nowadays available, but they are generally more expensive and/or harder to work on than traditional solders that have lead in them. The metals involved are not the only things to consider in a solder. Flux is vital to a good solder joint. Flux is an aggressive chemical that removes oxides and impurities from the parts to be soldered. The chemical reactions at the point(s) of connection must take place for the metals to fuse. RMA-type flux (Rosin Mildly Active) is the least corrosive of the readily available materials, and provides an adequate oxide removal.



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In electronics a 60/40 fluxed core solder is used. This consists of 60% Lead and 40% Tin, with flux cores added through the length of the solder. There are certain safety measures which you should keep in mind when soldering. The tin material used in soldering contains dangerous substances like lead (40-60% of typical soldering tins are lead and lead is poisonous). Also the various from the soldering flux can be dangerous. While it is true that lead does not vaporize at the temperatures at which soldering is typically done, particulate matter is just as dangerous as fumes would be in terms of poisoning and there is particulate lead present to some extent in the fumes from your flux. When soldering keep the room well ventilated and use a small fan or fume trap. A proper fume trap or a fan will keep the most pollution away from your face. Professional electronics workshops use expensive fume extraction systems to protect their workers (needed for working safety reasons). Those fume extraction devices have a special filter, which filters out the dangerous fumes. If you can connect a duct to the output from the trap to the outside, that would be great. Always wash hands prior to smoking, eating, drinking or going to the bathroom. When you handle soldering tin, your hands will pick up lead, which needs to be washed out from it before it gets to your body. Do not eat, drink or smoke whilst working with soldering iron. Do not place cups, glasses or a plate of food near your working area. Wash also the table sometimes. As you solder, at times there will be a bit of spitting and sputtering. If you look you'll see tiny balls of solder that shoot out and can be found on your soldering table. The soldering iron will last longer with proper care. Before and during use wipe the bit on a damp sponge. Most bench stands incorporate a sponge for this purpose. When using a new bit, apply solder to it as it heats up. Always keep a hot iron in a bench stand, or suspended by the hook, when not in use. Turn of the iron when you do not use it. Periodically remove the bit and clear away any oxide build up. Regularly check the mains lead for burns or other damage (change mains lead if necessary).



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11. CONCLUSION



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11. CONCLUSIONUnmanned railway gate controller is successfully designed and tested and a demo part is fabricated. Since it is a demonstration unit, low range RF modules are used. For practical applications, this circuit can be modified by adding long range RF modules. By using a GPS module, the geometric coordinates can be compared for the detection of train arrival. Other parameters such as velocity of the train and the location can also be determined. The circuit is simple, economical and can be easily implemented.



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12. REFERENCES



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12. REFERENCES Julio Sanchez, Maria P. Canton, Microcontroller Programming The Microchip PIC, CRC Press, Taylor & Francis Group John B Peatman, Design with PIC microcontrollers, Pearson Education. Kirk Zurell, , C programming for embedded systems, R&D Books, CMP Media, Inc. http://www.8051projects.info/datasheets/HT12D.pdf http://www.engineersgarage.com/sites/default/files/HT12E_0.PDF http://www.mikroe.com/eng/products/view/7/mikroc-pro-for-pic/ http://ww1.microchip.com/downloads/en/devicedoc/30292c.pdfhttp://en.wikipedia.org/wiki



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APPENDIX



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13.1 APPENDIX 1 : PCB LAYOUT COMPONENT VIEW

Figure.13

Figure.14



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BOARD VIEW

Figure.15

Figure.16



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13.2 APPENDIX 2 : BILL OF MATERIALS COMPONENT PIC microcontroller SPECIFICATION 16F877A QUANTITY 1 SOURCE Matha Electronics Eranakulam Encoder IC Decoder IC Motor Driver IC RF module HT12E HT12D L293D BX R433A BX R435 1 1 1 1 1 Thomson Electronics Eranakulam Voltage Regulator Diode Buzzer Resistor 7805 1N4007 Piezo electric 4.7K 47K 1.2K 33K 750K Capacitor 22pF 0.001uF 220pF Crystal 12MHz 2 2 1 2 1 2 1 1 2 1 1 1



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13.3 APPENDIX 3 : PIC PROGRAM #define power portb.f0 #define ledr portb.f1 #define buzz portb.f2 #define m1 portb.f3 #define m2 portb.f4 #define m3 portb.f5 #define mauto porta.f0 #define recv porta.f1 #define clsfb porta.f2 #define openfb porta.f3 #define mopen porta.f4 #define mclose porta.f5 void main( ) { porta=0x00; portb=0x00; adcon1=0x07; trisa=0xff; trisb=0x00; power=1; while(1) { while(mauto = =0) {



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while(recv = =1) { } ledr=1; buzz=1; delay_ms(5000); while(clsfb = =0) { m1=0; m2=1; m3=1; } m1=0; m2=0; m3=0; while(recv ! =0) { } ledr=0; buzz=0; while(openfb = =0) { m1=1; m2=0; m3=0; } m1=0;



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m2=0; m3=0; } portd=0xff; while(mauto = =1) { if(mopen = =1) { while(clsfb = =0) { m1=0; m2=1; m3=1; } m1=0; m2=0; m3=0; } if(mclose = =1) { while(openfb = =0) { m1=1; m2=0; m3=0; } m1=0;



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m2=0; m3=0; } } } }



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13.4 APPENDIX 4 : DATA SHEETS



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Prototype Rf Controlled Unmanned Railway Gate Control

Documents

rf system

rf transmission

rf module

rf signals

rf communication

chengannur prototype

unmanned railway gate

alarm gate control