Building Multiple Traffic Light Controller with a Cross Walk and an Emergency Buzzer

In the summer 2019, finishing up the class Introduction to Digital Devices CEIS114, we are working on a project to build a traffic light system with a motion sensor that give pedestrians time to pass the street with timer before green lights are turn on again. A set of emergency buttons are also implemented to hold the traffic by turning on a blue light to signal an incoming emergency.

Gathering Materials

From the IoT Starter Kits, the items needed are:

ESP32 Board

Two sets of Colored LEDs: Red, Yellow and Green

One Blue LED

Push Buttons

LCD Unit

Buzzer

Motion Detector

Wires

Breadboard

Mini Smart Router (Optional) Unfortunately I find out this router isn't working till the end of the project

Testing first set of lights

First prototype is build to test the codes and the basic components for the circuit are working.

A little help with Flow Chart

After the basic circuit is working well, we use flow chart to show what will happen based on the conditions if there are pedestrian or motion detected to change the traffic light signals.

ESP32

This helps to identify which port to use

Two Sets of traffic lights

Next stage is to add another set of traffic lights and see they traverse from green to yellow then to red while the other set only has red light stays on. When one set of light ends on red light the other set will start cycling from green to yellow to red. The cycle keeps going as long as the power supply is available.

Adding LCD and Touch Sensor

With working sets of traffic lights we add the LCD and the touch sensor. Notice that I am holding the tip of a white wire that sends the signal to turn Red lights.

Final Result

Final prototype is finished with replacing the touch sensor(white wire in the previous photo) with the Motion Sensor and a Blue led light on top left of the breadboard. By pressing the button as shown in the video the Blue led will light up to indicate it's an emergency.

Codes and Serial Monitor Output

This is the code for the final stage and also the Serial Monitor that shows the outputs while the program is running

#include <Wire.h> //lcd

#include <LiquidCrystal_I2C.h> //lcd

LiquidCrystal_I2C lcd(0x27,16,2); //set the LCD address to 0x27 for a 16 chars and 2-line display

// if it does not work then try 0x3F, if both addresses do not work then run the scan code below

const int bzr=14; // GPIO14 to connect the Buzzer

// Set GPIOs for LED and PIR Motion Sensor

const int led = 16; // Flashing White (Blue) Led

const int motionSensor = 17;

int pirState = 0 ;

int j,Em_value,Xw_value;

const int Em_button = 23; // Emergency button

const int Xw_button = 19; //Cross Walk button

//==================== LCD ====================

// the setup function runs once when you press reset or power the board

const int red_LED1 = 4; // The red LED1 is wired to ESP32 board pin GPIO04

const int yellow_LED1 = 2; // The yellow LED1 is wired to ESP32 board pin GPIO02

const int green_LED1 = 15; // The green LED1 is wired to ESP32 board pin GPIO15

const int red_LED2 = 25; // The red LED2 is wired to Mega board pin GPIO25

const int yellow_LED2 = 26; // The yellow LED2 is wired to Mega board pin GPIO 26

const int green_LED2 = 27; // The green LED2 is wired to Mega board pin GPIO 27

void setup() {

//================Motion Detector initialization =====

// PIR Motion Sensor mode INPUT

pinMode(motionSensor, INPUT);

pinMode(Em_button, INPUT_PULLUP); // 0=pressed, 1 = unpressed button

pinMode(Xw_button, INPUT_PULLUP); // 0=pressed, 1 = unpressed button

pinMode(bzr,OUTPUT);

pinMode(led, OUTPUT);

digitalWrite(led, LOW); // Set Flashing White (Blue) Light to LOW

//=======================================

Serial.begin(115200);

lcd.init(); // initialize the lcd

lcd.backlight();

lcd.setCursor(0,0); // column#4 and Row #1

lcd.print(" === CEIS114 ===");// can be replaced with your name

pinMode(red_LED1, OUTPUT); // initialize digital pin 4 (Red LED1) as an output.

pinMode(yellow_LED1, OUTPUT); // initialize digital pin 2 (yellow LED1) as an output.

pinMode(green_LED1, OUTPUT); // initialize digital pin 15 (green LED1) as an output.

pinMode(red_LED2, OUTPUT); // initialize digital pin 25(Red LED2) as an output.

pinMode(yellow_LED2, OUTPUT); // initialize digital pin 26 (yellow LED2) as an output.

pinMode(green_LED2, OUTPUT); // initialize digital pin 27 (green LED2) as an output.

}

// the loop function runs over and over again forever

void loop() {

// Check the emergency button

int Em_value=digitalRead(Em_button);

if (Em_value == 0){ // Emergency button was pressed so allow about 10 seconds

skipnow: // jump here in case of emergency ====================

Serial.println("Emergency button was pressed ");

// Both sides are RED with flashing White (Blue) light

digitalWrite(yellow_LED1 , LOW); // This should turn off the YELLOW LED1

digitalWrite(green_LED1, LOW); // This should turn off the GREEN LED1

digitalWrite(red_LED1, HIGH); // This should turn on the RED LED1

digitalWrite(red_LED2, HIGH); // This should turn on the RED LED2

digitalWrite(yellow_LED2 , LOW); // This should turn off the YELLOW LED2

digitalWrite(green_LED2, LOW); // This should turn off the GREEN LED2

for (j=0;j<10;j++){ // total of 10 seconds, can be changed

digitalWrite(led,HIGH);

delay(500); //Flashing white (blue) light every .5 sec -- ON

digitalWrite(led,LOW);

delay(500); //Flashing white (blue) light every .5 sec -- OFF

}

} // End of (if) statement for Emergency button

Em_value=digitalRead(Em_button);

int Xw_value=digitalRead(Xw_button);

pirState = digitalRead(motionSensor);

if (Em_value == 1){ // Emergency button not pressed

if (pirState == 1 || Xw_value == 0 ){ // Emergency button not pressed, X-button or motion pressed

// Transition: If a button is pressed, yellow on major street for 1sec. before switching

if(pirState == 1){Serial.println("motion detected");}

delay(500);

digitalWrite(green_LED1, LOW); // This should turn off the GREEN LED1

digitalWrite(yellow_LED1, HIGH); // This should turn on the Yellow LED1

delay(1500);

digitalWrite(bzr, HIGH);

digitalWrite(yellow_LED1 , LOW); // This should turn off the YELLOW LED1

digitalWrite(green_LED1, LOW); // This should turn off the GREEN LED1

digitalWrite(red_LED1, HIGH); // This should turn on the RED LED1

digitalWrite(red_LED2, LOW); // This should turn on the RED LED2

digitalWrite(yellow_LED2 , LOW); // This should turn off the YELLOW LED2

digitalWrite(green_LED2, HIGH); // This should turn off the GREEN LED2

// LED1 is a major street

for (int i=10; i>= 0; i--) {

Em_value=digitalRead(Em_button);// check for emergency button pressing

if (Em_value == 0)goto skipnow; // if so break and execute emergency at skipnow label

Serial.print(" Count = ");

Serial.print(i);

Serial.println(" == Walk == ");

lcd.setCursor(0,1); // set the cursor to column 1, line 2

// lcd.clear(); // clears the display to print new message

lcd.print(" ");

lcd.setCursor(0,1); // set the cursor to column 1, line 2

lcd.print(" == Walk == "); // Print T= characters to the LCD.

lcd.print(i); // Print the temperature in F to the

delay(1000);

digitalWrite(bzr, LOW);

delay(500);

} // End of counter

// clears the display to print new message

// ===== lcd.clear();

lcd.setCursor(0,1); // set the cursor to column 1, line 2

lcd.print(" ");

//====================================

// Transition

digitalWrite(green_LED2 , LOW); // This should turn off the YELLOW LED2

digitalWrite(yellow_LED2 , HIGH); // This should turn off the YELLOW LED2

delay(1000);

} // End of Emergency button not pressed, X-button pressed or Motion was detected

} //End of Emergency button not pressed

//===============================================

// No motion, No Emergency, No crossing, then LED1=Green, LED2=Red always

lcd.setCursor(0,1); // set the cursor to column 1, line 2

lcd.print(" = Do Not Walk ="); // Print T= characters to the LCD.

Serial.println(" == Do Not Walk == ");

digitalWrite(yellow_LED1 , LOW); // This should turn off the YELLOW LED1

digitalWrite(green_LED1, HIGH); // This should turn off the GREEN LED1

digitalWrite(red_LED1, LOW); // This should turn on the RED LED1

digitalWrite(red_LED2, HIGH); // This should turn on the RED LED2

digitalWrite(yellow_LED2 , LOW); // This should turn off the YELLOW LED2

digitalWrite(green_LED2, LOW); // This should turn off the GREEN LED2

delay(1000);

//====================End Motion ==========

}// End of loop

Obstacles

During the entire project there are few obstacles required more attention

Obstacle #1: Ground port for black wire on the LCD

As shown on the circuit schematic, the LCD wasn't working because it's recommended to connect the black wire to the Ground blue on side of the breadboard. I have connected to the ESP32 ground port instead in order for it to work. It's towards the end of the breadboard and the 2nd port right above the red wire in the diagram.

Obstacle #2: LCD square fuse is missing

The LCD wasn't working during the first trial because there is a missing part. Notice these two exact same components but the fuse on the bottom LCD is missing so that one wasn't working so I order another 2 LCD as backup and found out the problem.

Acquired Skills

I am very satisfied with the end result and the guidance of the teachers. This is the first time I have programmed ESP32 with a LCD and the buttons. Unfortunately the mini wireless router wasn't working so I couldn't work on controlling the traffic lights with the cloud service but I will try to work on it after I order new parts.

Coding Python is getting more fun after this project because I can build a circuitry to direct the current to do what my program is designed to do.

Better troubleshooting is also another skill set I've acquired for both coding and on the hardware. I have to change the code so the LCD will work and also to check all the small details on the LCD and breadboard to make the project work. Not to forget to follow the diagram of the instructional manual to know which wire goes to which port.

This project has provided me with a great head start to acquire more skill on building different IoT devices in the future as I learn to program different sensors and actuators and other components. Thanks a million DeVry University professors!

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