I developed this code to use an ultrasonic sensor and a servo motor to create a smart trash that can opens automatically when someone approaches it. It also displays the temperature inside the trash can on an LCD screen.

The first few lines of the code include the necessary libraries and declare the necessary variables. 

• The Wire.h library is used for I2C communication

•  LiquidCrystal_I2C.h is used for controlling the LCD screen 

• Servo.h is used for controlling the servo motor. 

• The Servo A declaration creates an instance of the Servo class called A, which is used to control the servo motor. 

• The tempsensor variable is set to A0, which is the pin that the temperature sensor is connected to. 

• The LiquidCrystal_I2C declaration creates an instance of the LiquidCrystal_I2C class called lcd, which is used to control the LCD screen.

• The readUltrasonicDistance function is used to measure the distance using the ultrasonic sensor. It takes two arguments, triggerPin and echoPin, which are the pins that the ultrasonic sensor is connected to. The function first clears the trigger pin, sets it to a low state, and waits for 2 microseconds. It then sets the trigger pin to a high state for 10 microseconds and then sets it back to a low state. It sets the echo pin to an input mode, reads the echo pin, and returns the sound wave travel time in microseconds.

the state boolean variable bool state=false; is used to keep track of whether the trash can lid is open or closed. It is initialized to false in the beginning of the code.

When someone approaches the trash can and the distance measured by the ultrasonic sensor is less than or equal to 30, the state variable is set to true, which indicates that the lid is open.

When the lid is open, the LCD screen displays the message "Put Your Trash Here", and the servo motor is set to the 140-degree position to keep the lid open. This is done in the following lines of code:

lcd.clear();

lcd.backlight();

lcd.setCursor(0, 0);

lcd.print("Put Your Trash Here");

delay(1000);

A.write(140);

When the distance measured by the ultrasonic sensor is greater than 30, the program checks the value of the state variable. If it is true, it means the lid was previously open, so the LCD screen displays the message "Thank You" and the servo motor is kept at the current position to keep the lid open. This is done in the following lines of code:

if (state == true) {

  lcd.clear();

  lcd.setCursor(3, 0);

  lcd.print("Thank You");

  delay(1000);

}

Eng/Menna Elbadry is who advise me to use the boolean here in this part, thank you <3

The void setup function initializes the variables and sets up the necessary pins and communication protocols. 

The A.attach(9) function attaches the servo motor to pin 9.

 The A.write(0) function sets the servo motor to the 0-degree position.

 The pinMode(A0, INPUT) function sets pin A0 to an input mode for the temperature sensor. 

The lcd.init() function initializes the LCD screen.

 The Serial.begin(9600) function initializes the serial monitor with a baud rate of 9600. 

The Serial.print(0.01723 * readUltrasonicDistance(2, 3)) function prints the distance measured by the ultrasonic sensor to the serial monitor.