Smart Traffic Light Controller with Pedestrian Detection

Overview

This project implements a fully embedded Smart Traffic Light System on an ATmega328P microcontroller. The system operates in multiple modes (Auto, Manual, Emergency), controls traffic lights using PWM brightness, detects pedestrians using a sonar distance sensor, and allows full system monitoring via USART serial communication.

The system demonstrates integration of multiple AVR modules including:
✅ ADC
✅ External Interrupts
✅ Pin Change Interrupts
✅ Timers (Overflow & PWM)
✅ USART with interrupt-driven RX
✅ Sonar (Ultrasonic Distance Measurement)
✅ PWM-based LED brightness control
✅ Buzzer alert generation

All modules are programmed directly with low-level AVR C — no Arduino libraries used.

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Project Features

• Multiple Operational Modes:

  • Auto Mode: Cycles lights automatically with pedestrian detection.
  • Manual Mode: User-controlled light switching.
  • Emergency Mode: Locks system to green for emergency flow.

• Sonar-based Pedestrian Detection:

  • Ultrasonic sensor detects nearby pedestrians.
  • Activates red light when pedestrians are within configurable distance.

• PWM-controlled Traffic Lights:

  • Smooth brightness control of red, yellow, and green LEDs.
  • Adaptive brightness based on ambient light using ADC.

• USART Debug Interface:

  • Real-time monitoring of system status and sensor readings.
  • Allows user to control debug output levels.

• Buzzer Alerts:

  • Beeping rate varies depending on pedestrian distance.

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Hardware Connections

Function	AVR Pin
Green Light (PWM)	PB1
Yellow Light (PWM)	PB2
Red Light (PWM)	PB3
Mode Change Button	PD2
Manual Light Button	PB0
Emergency Mode Button	PD3
Sonar Trigger	PD5
Sonar Echo	PD4
Buzzer Output	PD6
USART TX/RX	PD0 / PD1
Light Sensor (ADC)	PC2

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Software Modules Breakdown

• Timers:

  • Timer0: Overflow interrupt for periodic pedestrian detection checks.
  • Timer1: Fast PWM controlling Green/Yellow lights.
  • Timer2: Fast PWM controlling Red light.

• ADC:

  • Reads ambient light level for adaptive LED brightness.

• External Interrupts (INT1):

  • Emergency Mode toggle.

• Pin Change Interrupts (PCINT0, PCINT18):

  • Manual Mode light switching.
  • Mode switching.

• USART:

  • Serial debug output and runtime debug mode control via RX interrupt.

• Sonar Module:

  • Distance calculation for pedestrian detection with adaptive beep rates.

• Buzzer:

  • Audible alert when pedestrian detected, with variable beep intervals based on distance.

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