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1. INTRODUCTION
With the increased demand for railway services, train speed and density are consistently increasing in the last two decades. As a result, more strict safety requirements for railway signaling, control and infrastructure are needed. Accompanying that trend, in recent years, wireless communication techniques have also advanced rapidly. Especially with smart low cost wireless communication techniques like WIFI, Bluetooth, and ZigBee going into maturity, thus making it possible to develop a wireless system to monitor a railway's signaling or control or infrastructure condition. An effective low cost monitor system will help the normal function of railway systems. This paper gives a description of the development of one such monitoring system. The whole system consists of a remote controller and many monitor units. The remote controller gets data from the monitor units and sends control commands and monitoring control information to the monitor units. The paper will show how such a basic set up could be deployed for railway monitoring using wireless technology.
Many a times in the train we observe the necessity to come to know as to which station is approaching, mostly in the nights when we need to descent at the desired station. Especially for the lady passengers it becomes a situation of panic when they can’t decide as to which station is approaching in the nights when they can’t even ask the fellow passengers. Also, many of the Indian Railway stations are dark and without the appropriate lighting on the platforms making it very difficult to find-out the name of the station in the nights.
To solve this problem we propose to fit the train Bogies (compartments) with the Station Identification Systems, which can wirelessly get the information from the Station Master’s Room and can display it in required format inside the Bogey.


2. BLOCK DIAGRAMThe station monitoring system consists of Micro-controller, Oscillator and Reset circuits, Key Pad, LCD display, Output latches, Output drivers, LED indicators, Buzzer and Power supply.
2.1 MICRO-CONTROLLER
The heart of the system is the micro-controller. The Atmel 89S8253 with internal 8 Kbytes flash program memory and 2 Kbytes EEPROM memory is used as the controller. The intelligent railway station monitoring system algorithm is programmed in the micro-controller. The micro-controller circuit is completed by adding power-on reset and oscillator circuits. The controller receives the user commands from the keypad and sets various working modes of the system.
2.2 OSCILLATOR
The micro-controller has to be provided with a clock signal for its timing and control signals. Only an external crystal and two small capacitors are sufficient to form an oscillator with the internal phase shift amplifier.
2.3 RESET CIRCUIT
A power on reset circuit is provided for the proper initialization of the micro-controller after power up.
2.4 LCD DISPLAY
The LCD display provides the display of the relevant information and station name. The LCD display is a dual line 16-character display. 8 data lines and 3 control lines viz RS, R/W and E accomplishes the inter face to the LCD display. The LCD The display works from a single +5V supply.


Fig 3:- LIQUID CRYSTAL DISPLAY
The display has provision of backlit by the way of LEDs mounted at the back of the display for the visibility at dark condition. The display mounted on the front panel and is connected to the micro-controller board by means of a ribbon cable and connector.
2.5 OUTPUT LATCHES AND DRIVERS
The output port lines of the micro-controller are expanded using a latches. A total of 32 LED drive lines are required for drive 32 separate LED and Buzzer. Eight lines from Port2 are connected to the D input of the octal D-type latch 74HC573.
The 74HC573 are octal D-type transparent latches featuring separate D-type inputs for each latch and 3-state outputs for bus oriented applications. A latch enable (LE) input and an output enable (OE) input are common to all latches. When LE is HIGH, data at the Dn inputs enter the latches. When LE is LOW the latches store the information that was present at the D-inputs. When OE is LOW, the contents of the 8 latches are available at the outputs.
In the circuit the LE lines to individual latches are coming from Port 3.0-3.3. Hence Port2 output can be latched to anyone of the latch selected by the LE. The OE line permanently connected to ground so that latch output is available all the time.
The output driving capacity of the 74HC573 latch is limited; hence latch output is buffered by open collector driver ULN 2803. The ULN2803 is high voltage, high current darlington arrays each containing eight open collector darlington pairs with common emitters. Each channel rated at 500mAand can withstand peak currents of 600mA. Suppression diodes are included for inductive load driving.
2.6 POWER SUPPLY
The intelligent railway station monitoring system is operated from the mains supply. A 9V-0-9V step down transformer provides the 9VAC, which is rectified and filtered to get an unregulated +12V. 1N4007 rectifier diodes are used for the rectification of ac supply into dc supply. A 470uF/25V capacitor in parallel with 0.1uF capacitor provides the necessary filtering of the rectified output. This voltage is regulated to +5V by means of fixed voltage regulator LM7805. The regulated output is again filtered by a 470uF/25V capacitor in parallel with 0.1uF capacitor.


3 HARDWARE DESCRIPTION
3.1 POWER SUPPLY
These form an important equipment of any Electronics laboratory. Power supplies are essential for the testing and implementation of any useful electronic circuit. If power supplies are not available then the only way to provide power to a circuit is the battery. For long-term use and frequent manipulation these are not feasible. More over these are not as flexible as modern day power supplies. They do not provide for overload protection and thermal protection.
The following units form the backbone of any modern day power supply
1. Full wave bridge rectifier
2. Filter circuit
3. Voltage regulator
In the case if modern power supplies, the required power is derived from the AC mains. For this at first the 230V/50 Hz is step down using a step down transformer. Then The AC voltage is converted to DC using a rectifier circuit. The bridge rectifier is considered the apt choice since it avoids the center-tapped transformer. The ripples from the rectifier output are removed by filtering.
The filter can be any of the following:
1. L filter
2. C filter
3. LC filter
4. CRC filter and we use capacitive filtering.
The function of the voltage regulator is to provide a stable DC voltage for powering other electronic circuits. The voltage regulator must be capable of providing substantial output current. They must provide a constant voltage regardless of changes in load current, temperature, and AC line voltage. Although voltage regulators can be designed using op amps, it is quicker and easier to use IC Voltage regulators. Furthermore, IC voltage regulators are versatile and relatively inexpensive and are available with features such as programmable output, current / voltage boosting, internal short –circuit current limiting, thermal shut down, and floating operation for high voltage applications.
Voltage regulator may be classified as:
1. Series regulator
2. Switching regulator
Series regulators use a power transistor connected in series between the unregulated DC input and the load. The output voltage is controlled by the continuous voltage drop-taking place across the series pass transistor. Since the transistor conducts in the active or the linear region, these regulators are also called linear regulators. Linear regulators may have fixed or variable output voltages and could be positive or negative. Voltage regulators such as the 78XX series and the IC 723 are commonly used.

4 CIRCUIT DIAGRAM
4.1 CIRCUIT DESCRIPTION
4.1.1 MICRO-CONTROLLER
The heart of the intelligent railway station monitoring system is the Atmel AT89S8253 micro-controller. The AT89S8253 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of in-system programmable Flash memory and 2Kbytes of EEPROM data memory. The device is compatible with the industry standard 80C51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the Atmel AT89S8252 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications.
The AT89S8253 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 2K bytes of EEPROM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S8252 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 interrupt or hardware reset.
With few discrete components for oscillator and reset, a complete micro-controller system can be implemented. Port 0 lines are connected to the LCD display circuit. Port 0 lines require external pull up resistors to maintain logic levels. 10k ohm resistors are connected from port0 lines to VCC. Port2 is connected to the output latches. Port 3 provides latch enable lines for the latches. Port 1 is configured as input to read the key pad status.
The /EA line tied to the VCC through a 10K ohm resistance so that the micro-controller is configured to use internal memory.