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INTRODUCTION
As the number of vehicles and the needs for greater transportation has grown in recent years, city streets and highways frequently face serious road traffic congestion problems. Due to this factor, traffic signals now become a common feature of cities controlling heavy traffic. Careful planning of these signals is important to increase the efficiency of traffic flow on road. Controlling traffic on oversaturated intersections is a big issue.
Conventional methods for traffic signal control based precise models fail to deal efficiently with the complex and varying traffic situations. They are modeled based on the preset cycle time to change the signal without any analysis of traffic situation. Due to fixed cycle time, such systems do not consider that which intersection has more load of traffic, so should kept green more or should terminate earlier then complete cycle time. In case of intersections, conventional control systems only consider waiting time of signals on different directions but not the vehicle directions. Such situations can be seen in various areas of Delhi and NCR where traffic flow varies in different hours and heavy traffic flows in morning and evening timings because of large number of offices on that route. Also, in different intersections, traffic flow abruptly changes in schools timings then other daily hours. Preset Cycle Time Controllers fail in such scenarios because they could not get complete information of vehicles earlier.
Fuzzy based controllers are proved to be well manager of traffic system in such scenarios. Fuzzy Logic based controllers have the ability to take decision even with incomplete information. More and more sophisticated controllers are being developed for traffic control.
These algorithms are continually improving the safety and efficiency by reducing the waiting delay of vehicles on signals. This increases the tempo of travel and thus makes signals more effective and traffic flow smooth. The key motivation towards Fuzzy Logic in traffic signal control is the existence of uncertainties in signal control. Decisions are taken based on imprecise information and the effect of evaluation is not well known.
METHODOLOGY:
The fuzzy logic controller determines whether to extend or terminate the current green phase based on a set of fuzzy rules. The fuzzy rules compare traffic conditions with the current green phase and traffic conditions with the next candidate green phase. The flow diagram of a controller is shown in figure 1.
A BRIEF INTRODUCTION TO 8051 MICROCONTROLLER:
When we have to learn about a new computer we have to familiarize about the machine capability we are using, and we can do it by studying the internal hardware design (devices architecture), and also to know about the size, number and the size of the registers.
A microcontroller is a single chip that contains the processor (the CPU), non-volatile memory for the program (ROM or flash), volatile memory for input and output (RAM), a clock and an I/O control unit. Also called a "computer on a chip," billions of microcontroller units (MCUs) are embedded each year in a myriad of products from toys to appliances to automobiles. For example, a single vehicle can use 70 or more microcontrollers. The following picture describes a general block diagram of microcontroller.
89s52: The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K 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's AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications. The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 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 AT89S52 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 con-tents but freezes the oscillator, disabling all other chip functions until the next interrupt
The hardware is driven by a set of program instructions, or software. Once familiar with hardware and software, the user can then apply the microcontroller to the problems easily.
The pin diagram of the 8051 shows all of the input/output pins unique to microcontrollers:
The following are some of the capabilities of 8051 microcontroller.
 Internal ROM and RAM
 I/O ports with programmable pins
 Timers and counters
 Serial data communication
The 8051 architecture consists of these specific features:
 16 bit PC &data pointer (DPTR)
 8 bit program status word (PSW)
 8 bit stack pointer (SP)
 Internal ROM 4k
 Internal RAM of 128 bytes.
 4 register banks, each containing 8 registers
 80 bits of general purpose data memory
 32 input/output pins arranged as four 8 bit ports0-P3
 Two 16 bit timer/counters: T0-T1
 Two external and three internal interrupt sources
 Oscillator and clock circuits
For any electronics project the power supply plays a very important role in its proper functioning.
In this project we are using external A.C supply (220 v) as input , this high voltage is converted into 12 Volts A.C by step down transformer , then we use voltage regulators and filters with bridge rectifier to convert the A.C into D.C voltage .
For voltage regulation we are using LM 7805 and 7812 to produce ripple free 5 and 12 volts D.C constant supply.