Traffic Light Controller for Four-Way Intersection

A digital logic implementation of an intelligent traffic light control system for a four-way intersection using state machine design with D-flip flops.

🚦 Overview

This project implements a traffic light controller that manages traffic flow at a four-way intersection using a finite state machine approach. The system uses two D-flip flops to create four distinct states, each controlling the traffic light patterns for North-South and East-West directions.

📋 Features

• 4-State Traffic Control: Manages complete traffic light cycle for both directions
• Timing-Based Transitions: Uses 5-second and 15-second timing intervals
• Safe Traffic Flow: Ensures proper yellow light transitions and prevents conflicts
• Digital Logic Implementation: Built using D-flip flops and combinational logic

🔧 System Architecture

State Machine Design

The controller uses 2 D-flip flops (A, B) to create 4 states:

State	A	B	North-South	East-West
00	0	0	🟢 Green	🔴 Red
01	0	1	🟡 Yellow	🔴 Red
10	1	0	🔴 Red	🟢 Green
11	1	1	🔴 Red	🟡 Yellow

Timing Control

The system uses two timing inputs:

• x = 1: When counter reaches 5 seconds (for yellow light duration)
• y = 1: When counter reaches 15 seconds (for green light duration)

🚀 Implementation

Hardware Requirements

• 2 × D-flip flops
• Combinational logic gates (AND, OR, NOT)
• Timing counter circuit
• LED indicators for traffic lights

Software Tools

• Digital logic simulator (e.g., Logisim)

📊 Operation Cycle

1. State 00: North-South GREEN (15 seconds) → East-West RED
2. State 01: North-South YELLOW (5 seconds) → East-West RED
3. State 10: North-South RED → East-West GREEN (15 seconds)
4. State 11: North-South RED → East-West YELLOW (5 seconds)
5. Repeat: Returns to State 00

🔬 Design Methodology

This project demonstrates:

• Finite State Machine Design: Systematic approach to sequential logic
• State Encoding: Efficient use of flip-flops for state representation
• Timing Constraints: Real-world timing requirements integration
• Safety Considerations: Proper traffic light sequencing

🧪 Testing

The design includes comprehensive testing scenarios:

• State transition verification
• Timing constraint validation
• Edge case handling
• Safety requirement compliance

🤝 Contributing

Contributions are welcome! Please feel free to submit pull requests for:

• Design optimizations
• Additional timing modes
• Enhanced safety features
• Documentation improvements

🎓 Educational Context

This project is designed for digital logic and computer engineering coursework, demonstrating practical applications of:

• Sequential logic design
• State machine implementation
• Real-world timing constraints
• Safety-critical system design

📞 Contact

For questions or suggestions regarding this traffic light controller implementation, please contact me at: [email protected].

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This project demonstrates the practical application of digital logic principles in traffic management systems, emphasizing both technical implementation and safety considerations.