Traffic Light Controller with Pedestrian crossing

Man and movement 

The first Traffic lights were installed outside the Palace of Westminster London on 10th December 1868 to control the increasing number of vehicles there. However, according to some sources, the Traffic lights controller later exploded and injured the policeman operating it [1]. This Traffic Light design was adapted for controlling movement of vehicles and pedestrians at a critical busy junction. 

According to the UK Department of Transport, the number of vehicles plying the road has increased exponentially from about 4 million in 1950 to over 35 million in 2013. As a result, controlling movement of these vehicles has become very essential for the sake of a safe environment for all. Many junctions with traffic lights also have pedestrian crossings built into them. The pedestrian crossing use different indicators to prompt pedestrians when it is safe to cross upon pressing a push-button. 

How the system works

The traffic light controller operates in a cyclic manner illuminating the red, amber and green lights indicators accordingly using the UK Traffic lights sequence. Whenever the system detects that the pedestrian push button is pressed, the control system should allow an ongoing vehicle traffic lights cycle to complete before attending to the pedestrian request to cross safely. Once the cycle finishes, the control system should alert the pedestrian that it is safe to cross by sounding an alarm with red illuminated. Upon pressing the push button, an LED will be illuminated to alert the pedestrian to wait for an alarm before crossing safely. 

Implementing the system 

The complete schematic of the traffic light system is shown in figure 1.0 below. The traffic controller used for this implementation is PIC16F648A micro-controller. The device is a Flash-Based, 8-Bit CMOS device nanoWatt Technology.

figure 1.0: System schematic

MPLAB IDE was the program software used to implement the C code using the inbuilt functions of the HI-TECH C compiler inside the MPLAB. The pedestrian push button request is implemented  as an interrupt function. The complete code developed for the system is listed below:

/******************************************************************************************** C Program for Traffic Light Control

Author: Uche Ejiofor,24/08/14

Version: 1.1 
**********************************************************************************************/

#include <htc.h> //include HITECH C Compiler header file

/*CONFIGURATION*/
__CONFIG(FOSC_INTOSCIO & WDTE_OFF & PWRTE_ON & BOREN_OFF & LVP_OFF & CP_OFF & CPD_OFF);
#define _XTAL_FREQ 4000000L //INTERNAL 4MHz CLOCK

// GLOBAL VARIABLE DECLARATION
unsigned char IntFile;

/*CODE ORIGIN*/
void main()
{
//OSCF=0X01;                 //INTOSC Oscillator Frequency set at 48KHZ
GIE = 1; // enable general interrupt
INTE = 1; //INTERRUPTS at pin RB0/INT enabled 
INTEDG = 1; //RISING-EDGE TRIGGERD INTERRUPT ENABLED AT PIN RBO/INT

TRISA=0x00;             //ALL pins at PORTA SET to OUTPUT PORT
TRISB=0x01;             //PORTB RB0 pin SET to input, rest OUTPUT 
PORTB=0x00; //clear PORTB for wrong signalling


while(1){

PORTB=0x90;            //NORTH RED, WEST AMBER
    __delay_ms(4000);    //LOOP 4 TIMES, 4-SECOND DELAY
        
    
     PORTB=0xD0;            //NORTH RED AND AMBER, WEST RED
     __delay_ms(4000);    //LOOP 4 TIMES, 4-SECOND DELAY
     
     PORTB=0x30;            //NORTH GREEN, WEST RED
     __delay_ms(10000);    //LOOP 10 TIMES, 25-SECOND DELAY
        
     PORTB=0x50;            //NORTH AMBER, WEST RED
     __delay_ms(4000);    //LOOP 4 TIMES, 4-SECOND DELAY
       
     PORTB=0x90;            //NORTH RED, SDRY RED
     __delay_ms(4000);    //LOOP 4 TIMES, 4-SECOND DELAY
       
     PORTB=0x98;            //NORTH RED, WEST RED AND AMBER
     __delay_ms(4000);    //LOOP 4 TIMES, 4-SECOND DELAY
        
     PORTB=0x84;            //NORTH RED, WEST GREEN
     __delay_ms(10000);    //LOOP 25 TIMES, 25-SECOND DELAY
        
PORTB=0x88;            //NORTH RED, WEST AMBER
    __delay_ms(4000);    //LOOP 4 TIMES, 4-SECOND DELAY

        
   if (IntFile==0xFF){         //Check if there was a pin change on RB0/INT pin
    RA0 = 0;
    PORTB=0x92;         //NORTH TRAFFIC RED, WEST TRAFFIC RED, PIEZZO SOUNDER ACTIVATED 
    __delay_ms(10000);   //LOOP 15 TIMES, 15-SECOND DELAY
       
IntFile = 0; //clear interrupt bit
}
 } //END WHILE
} //END MAIN

void interrupt isr(void) // Interrupt function 

{
if(INTF==1){ // check if pedestrian button is pressed  
      
        RA0 = 1; //light up LED for wait
IntFile = 0xFF;

INTF=0; // clear flag bit 
        }
return;
}

Results

Video of results located in media 1 can be played to appreciate the system demonstration.

Media 1: Traffic light video of results

Epilogue

The traffic lights sequence is tabulated for microcontroller implementation. The push button light can be designed in software to be ON and OFF at certain times using different ways!