Introduction to Arduino

Ultrasonic Distance Sensor with Piezo Buzzer

Arduino UNO R3 Pin Setup


    This project uses an HC-SR04 Ultrasonic Sensor to determines the distance to an object. This distance value is passed through a Low Pass Filter to create a smoother stream of values. The filtered data is then used to change the tone of the buzzer according to the object’s distance.

Parts List:
    1 HC-SR04 Ultrasonic Sensor
    1 Small Piezo Buzzer
    1 Arduino UNO R3
    1 Breadboard
    Connector Wires


    //------------- Code Starts Here ----------------------------
    //Published by
    //Created by Paul Illsley (
    //Please use and share so others can enjoy
    // Declaring pin 8 as the ultrasonic sensor's trigger pin (integer)
    int trigger_pin = 8;
    // Declaring pin 12 as the ultrasonic sensor's echo pin (integer)
    int echo_pin = 12;
    // Declaring pin 7 as the buzzer pin (integer)
    int buzzer_pin = 7;
    // Creating a variable to hold the ultrasonic sensor's data stream (floating point)  
    float RawData;
    // Creating a variable to hold information for the data smoothing process
    // A 0 value is required to start the process (floating point)
    float OldRawData = 0;
    // Creating a variable to hold the filtered (smoothed) data (floating point)
    float FilteredData;
    // Creating a variable to hold the Distance value (floating point)
    float Distance;
    void setup() 
      // Begin serial port at a baud rate of 9600
      Serial.begin (9600);
      // Setting the trigger pin as an output
      pinMode(trigger_pin, OUTPUT);
      // Setting the echo pin as an input
      pinMode(echo_pin, INPUT);
      // Setting the buzzer pin as an output
      pinMode(buzzer_pin, OUTPUT);
    void loop() 
      // Setting the trigger pin to low
      digitalWrite(trigger_pin, LOW);
      // delay 1 microseconds
      // Setting the trigger pin to high
      digitalWrite(trigger_pin, HIGH);
      // delay 5 microseconds
      // Setting the trigger pin to low
      digitalWrite(trigger_pin, LOW);
      // Populating the RawData variable with the echo data from the ultrasonic sensor
      // Values are milliseconds between the time the sound pulse left the transmitter and returned back to the receiver 
      RawData = pulseIn(echo_pin, HIGH);
      // Calculating the Distance (cm) from the semsor
      Distance = RawData * 0.034 / 2;
      // Filter the RawData to help create a smoother data flow.
      // The OldRawData is given an 80% weight which is added to the RawData having a 20% weight
      // The OldRawData value is derived from original 0 value or created later in the code from the previous loop's FilterdData value 
      // Setting up the serial port's readout format
      // Open the Serial Monitor to view your data values (Tools / Serial Monitor)
      // Open the Serial Plotter to view your data as a graph (Tools / Serial Plotter)
      Serial.print("Raw Data (ms): ");
      Serial.print(", ");
      Serial.print("Distance (cm): ");
      Serial.print(", ");
      Serial.print("Filtered Data (ms): ");
      // Mapping the buzzer's frequency range for the FilteredData range 
      // Creating a new variable called Sound (integer)
      // Data range is between 50 and 2000
      // Frequency range is between 120 and 1500 megahertz
      // These values can be changed to suit your data and desired frequency ranges
      int Sound = map(FilteredData, 50, 2000, 120, 1500);
      // Sending the remapped data (Sound) to pin 7 (the buzzer)
      tone(7, Sound, 0);
      // Making the variable OldRawData equal to FilteredData to be used in the next loop (for the smoothing process)
      //Delay 10 millisecond (then repeat the loop)
    //------------- Code Stops Here ----------------------------

    Created by Paul Illsley

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