B31DD Course Project — Traffic Light System

Sun, 08 Dec 2024 00:00:00 +0000

B31DD Mini-Project Report

Traffic Light Display System with Servo Control and Serial Monitoring

1. Project Introduction

The Traffic Light Display System is an embedded project designed to simulate a real-world traffic light controller using an AVR microcontroller. This system manages traffic flow by controlling red, yellow, and green LEDs, incorporates a servo motor to represent mechanical signaling (e.g., pedestrian crossing), displays countdown timers on an LCD, and logs traffic light changes via serial communication. Additionally, it features an interrupt-driven button allowing pedestrians to request crossing, thereby altering the normal traffic sequence.

Key Techniques Used:

Input/Output
Timer
Interrupt
PWM and Servo Control
Serial Communication
LCD Display

2. Functionalities

Traffic Light Control: Manages red, yellow, and green LEDs to simulate traffic signals.
Servo Motor Integration: Adjusts the servo position based on the active traffic light (0° for red, 90° for green).
LCD Display: Shows the current traffic light status and a countdown timer.
Serial Communication: Logs traffic light changes to a serial monitor for monitoring and debugging.
Interrupt-Driven Pedestrian Button: Allows pedestrians to request crossing, triggering a modified traffic sequence.

3. Hardware Components and Schematics

3.1 Components Used

Microcontroller: AVR (e.g., ATmega328P)
LEDs: Red, Yellow, Green
Servo Motor: Standard hobby servo
LCD Display: 16x2 character LCD
Button: Momentary push-button
Resistors: Current-limiting resistors for LEDs
Power Supply: 5V regulated supply
Miscellaneous: Breadboard, jumper wires, USB-to-Serial adapter

3.2 Connection Overview

LEDs:
- Red LED: Connected to PORTB3 through a current-limiting resistor.
- Yellow LED: Connected to PORTB4 through a current-limiting resistor.
- Green LED: Connected to PORTB5 through a current-limiting resistor.
Servo Motor:
- Control Pin: Connected to PORTB2 (OC1B).
- Power: Connected to an external 5V supply with a common ground.
LCD Display:
- Data Lines (D4-D7): Connected to PORTD4-PORTD7.
- Control Lines (RS, EN): Connected to PORTB0 and PORTB1.
Button:
- One Terminal: Connected to PORTD3.
- Other Terminal: Connected to GND with an internal pull-up resistor enabled.
Serial Communication:
- TX Pin (PD1): Connected to RX of USB-to-Serial adapter.
- Common Ground: Ensured between microcontroller and adapter.

4. Techniques and Methodologies

4.1 LED Control

Utilized PORTB pins to control red, yellow, and green LEDs.
Employed bitwise operations to set and clear specific LED states without affecting others.

4.2 Servo Motor Control

Implemented PWM (Pulse Width Modulation) using Timer1 in Fast PWM mode.
Mapped specific angles (0° and 90°) to corresponding pulse widths to position the servo accurately.
Configured the servo to reset to 0° during red light and move to 90° during green light.

4.3 LCD Display

Initialized the LCD in 4-bit mode for efficient data transmission.
Displayed the current traffic light status and a countdown timer on two lines.
Utilized sprintf for formatting countdown strings.

4.4 Serial Communication

Configured USART for serial communication at 9600 baud rate.
Implemented functions to initialize USART, transmit single characters, and send strings.
Logged every traffic light change with appropriate messages for monitoring.

4.5 Interrupt Handling

Configured an external interrupt (INT1) on PORTD3 to detect button presses.
Employed a sequence in the ISR, when the button is pressed, to display the yellow light for 3 seconds and then the green light for 5 seconds for pedestrians crossing the road.

5. Demo Results

5.1 Normal Traffic Sequence

Red Light:
- LED: Red LED on.
- Servo: Positioned at 0°.
- LCD: Displays “RED LIGHT” with an 8-second countdown.
- Serial: Logs “RED LIGHT”.
Green Light:
- LED: Green LED on.
- Servo: Positioned at 90°.
- LCD: Displays “GREEN LIGHT” with a 4-second countdown.
- Serial: Logs “GREEN LIGHT”.
Yellow Light:
- LED: Yellow LED on.
- LCD: Displays “YELLOW LIGHT” with a 2-second countdown.
- Serial: Logs “YELLOW LIGHT”.
  (Repeat cycle)

5.2 Pedestrian Request Sequence

Button Press Detected: Triggers the ISR to execute the special sequence.

Yellow Light:
- LED: Yellow LED on.
- LCD: Displays “Pedestrians” with a 3-second countdown.
- Serial: Logs “YELLOW LIGHT”.
Green Light:
- LED: Green LED on.
- Servo: Positioned at 90°.
- LCD: Displays “GREEN LIGHT” with a 5-second countdown.
- Serial: Logs “GREEN LIGHT”.
Return to Normal Sequence:
- Servo: Resets to 0°.
- Resumes Normal Traffic Cycle.

6. Performance Evaluation

Timing Accuracy: _delay_ms() provided sufficient timing for demonstration purposes, but hardware timers are recommended for higher precision.
Interrupt Responsiveness: The system detected button presses and executed pedestrian requests promptly.
Servo Control: Smooth and accurate transitions between designated angles.
Serial Logging: Reliable logging of traffic light changes for monitoring.
LCD Display: Consistently displayed accurate statuses and countdowns.

Areas for Improvement:

Implement software or hardware debouncing for the button.
Extend servo angle functionality for versatile signaling.
Replace _delay_ms() with timer-based delays for concurrent tasks.
Add error handling for USART transmission and routine interruptions.

7. Conclusion

The Traffic Light Display System integrates various embedded system components controlled by an AVR microcontroller. Interrupt-driven button handling adds interactivity and realism, showcasing practical applications of PWM, serial communication, and user interfaces.

8. References

AVR Microcontroller Datasheet
Arduino Documentation
LCD Display Lab3 Tutorials
Servo Motor Control course material
Serial Communication course material

Arduino on Decsnow Media