Arduino Parking Sensor

/**************************************************
 *              Arduino Parking Sensor            *
 *              learnelectronics 2023             *
 *              arduino0169@gmail.com             *
 *              www.youtube.com/learnelectronics  *
 *              based on code by Muhammad Ansar   *
 **************************************************/

/* No Libraries required*/






                                                // First we will define where the HCSR04 pins are connected

#define echo 8                                  //Echo pin
#define trigger 9                               //Trigger pin

                                                //Next we define where the buzzer is connected

#define buzzer 7                                //Piezo buzzer pin

                                                //Finally we define where the 3 LED traffic light is connected

#define R_led 4                                 //Red Led
#define Y_led 3                                 //Yellow Led
#define G_led 2                                 //Green Led

                                                // Now we create 2 integer (whole number) variables
int distance_cm;                                // Distance to sensor
int flag=0;                                     // Flag set or not

                                                // Setup routine - are pins input or output? Serial comms etc
                                                // setup routine runs only one time at the beginning

void setup() {                                  // Create setup ruotine
Serial.begin(9600);                             //turn on serial comms for debugging and distance reporting

pinMode(echo, INPUT);                           // set pin 8 as input (HCSR04 echo pin)
pinMode(trigger, OUTPUT);                       // set pin 9 as ouput (HCSR04 trigger pin)

pinMode(buzzer,OUTPUT);                         // set pin 7 as output (buzzer)

pinMode(R_led,OUTPUT);                          // set pin 4 as output (red LED)
pinMode(Y_led,OUTPUT);                          // set pin 3 as output (yellow LED)
pinMode(G_led,OUTPUT);                          // set pin 2 as output (green LED)

delay(100);                                     //wait 1/10 of a second
}                                               //end setup

//***************************************************************************************************************


void loop() {                                   //Main program loop



distance_cm = Ultrasonic_read();                //set the value of variable distance_cm to reading of HRSC04

     if(distance_cm<4){                         //if car is less than 4cm from sensor turn on red led and others off
flag = !flag;                                   // set flag to not flag
digitalWrite(R_led, HIGH);                      // LED Turn On
digitalWrite(Y_led, LOW);                       // LED Turn Off
digitalWrite(G_led, LOW);                       // LED Turn Off
}

else if(distance_cm>=4 && distance_cm<12){      //if car is between 4 and 12 cm from sensor turn on yellow and others off
flag=0;
digitalWrite(R_led, LOW);                       // LED Turn Off
digitalWrite(Y_led, HIGH);                      // LED Turn On
digitalWrite(G_led, LOW);                       // LED Turn Off
}

else if(distance_cm>=12 && distance_cm<25){     //if car is between 12 and 25cm from sensor turn on green and others off
flag=0;
digitalWrite(R_led, LOW);                       // LED Turn Off
digitalWrite(Y_led, LOW);                       // LED Turn Off
digitalWrite(G_led, HIGH);                      // LED Turn On
 }
else{                                           //if nothing triggers sensor turn all leds off
flag=0;
digitalWrite(R_led, LOW);                       // LED Turn Off
digitalWrite(Y_led, LOW);                       // LED Turn Off
digitalWrite(G_led, LOW);                       // LED Turn Off
}

digitalWrite(buzzer, flag);                     //if car is less than 4 cm from sensor turn on buzzer
Serial.print("cm: ");                           //write "cm: " to serial port
Serial.println(distance_cm);                    //write the distance in cm to serial port
delay(150);
}

                                                //Ultrasonic_read
int Ultrasonic_read(){
digitalWrite(trigger, LOW);                     //trigger off
delayMicroseconds(2);                           //wait
digitalWrite(trigger, HIGH);                    //trigger on
delayMicroseconds(10);                          //wait
long time = pulseIn(echo, HIGH);                //create variable time and make it equal to reading from HRSC04
return distance_cm = time / 28.5 / 2;           //distance in cm is equal to time divided by 28.5 divided by 2
}