17-06-2013, 04:53 PM
AUTOMATIC RAILWAY SIGNALLING SYSTEM
AUTOMATIC RAILWAY.doc (Size: 1.68 MB / Downloads: 60)
INTRODUCTION
EMBEDDED SYSTEM:
An embedded system is a special-purpose system in which the computer is completely encapsulated by or dedicated to the device or system it controls. Unlike a general-purpose computer, such as a personal computer, an embedded system performs one or a few predefined tasks, usually with very specific requirements. Since the system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product. Embedded systems are often mass-produced, benefiting from economies of scale.
Personal digital assistants (PDAs) or handheld computers are generally considered embedded devices because of the nature of their hardware design, even though they are more expandable in software terms. This line of definition continues to blur as devices expand. With the introduction of the OQO Model 2 with the Windows XP operating system and ports such as a USB port — both features usually belong to "general purpose computers", — the line of nomenclature blurs even more.
Examples of Embedded Systems:
• Avionics, such as inertial guidance systems, flight control hardware/software and other integrated systems in aircraft and missiles
• Cellular telephones and telephone switches
• Engine controllers and antilock brake controllers for automobiles
• Home automation products, such as thermostats, air conditioners, sprinklers, and security monitoring systems
• Handheld calculators
• Handheld computers
ABSTRACT
The railroad industry’s own desire to maintain their ability to provide safe and secure transport of their customers hazardous materials, has introduced new challenges in rail security. Addressing these challenges is important, as railroads, and the efficient delivery of their cargo, play a vital role in the economy of the country.
The present project is designed to satisfy the security needs of the railways. This system provides the security in four ways: automatic gate opening/closing system at track crossing, signaling for the train driver, tracking the signals, and the track protection. The automatic gate opening/closing system is provided with the Reflection sensors placed at a distance of few kilometers on the both sides from the crossing road. These sensors give the train reaching and leaving status to the embedded controller at the gate to which they are connected. The controller operates (open/close) the gate as per the received signal from the Reflection sensors.
Block diagram explanation:
The objective of this project is to provide signaling system for the railways to enter and leave the track. The automatic gate opening/closing system is provided with the Reflection sensors placed at a distance of few kilometers on the both sides from the crossing road. These sensors give the train reaching and leaving status to the embedded controller at the gate to which they are connected. The controller operates (open/close) the gate as per the received signal from the Reflection sensors.
Hardware components:
MICRO CONTROLLER (AT89S51)
Introduction
A Micro controller consists of a powerful CPU tightly coupled with memory, various I/O interfaces such as serial port, parallel port timer or counter, interrupt controller, data acquisition interfaces-Analog to Digital converter, Digital to Analog converter, integrated on to a single silicon chip.
If a system is developed with a microprocessor, the designer has to go for external memory such as RAM, ROM, EPROM and peripherals. But controller is provided all these facilities on a single chip. Development of a Micro controller reduces PCB size and cost of design.
One of the major differences between a Microprocessor and a Micro controller is that a controller often deals with bits not bytes as in the real world application.
Intel has introduced a family of Micro controllers called the MCS-51.
Description
The AT89S51 is a low-power, high-performance CMOS 8-bit microcontroller with 4K bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry- standard 80C51 instruction set and pinout. 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 AT89S51 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications.
ALE/PROG:
Address Latch Enable (ALE) is an output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.