"See" like a bat – bat goggles code

Code for controlling an HC-SR04 Ultrasonic distance sensor and piezo buzzer to mimic sonar.

Here be code to make an Arduino, HC-SR04 Ultrasonic distance sensor and a piezo buzzer mimic sonar. I've used this to for bat goggles but you could equally hack it to control a wall avoiding robot. This was written for a series of workshops I'm delivering for MadLab.

becky wearing the prototype bat goggles
Becky wearing the prototype bat goggles

This code is based on Suneth Attygalle's batgoggles code, and the Arduino Ping Tutorial

// declare the pins

const int trigPin = 5;
const int echoPin = 6;
const int buzzerPin = 4;

// set up constants

const long scalingfactor = 10;

// set global variables

int cm;
unsigned long time1, time2, i, duration;
unsigned long maxtime = 1000;

void setup() {
    // initialise all the pins

    pinMode(trigPin, OUTPUT);
    pinMode(echoPin, INPUT);
    pinMode(buzzerPin, OUTPUT);

    // uncomment this if you need to check why things aren't
    // working
    // Serial.begin(9600);

void loop() {
    // beep
    tone(buzzerPin, 262);
    // sets the note to middle c (ish)


    // if the sensor doesn't time out remove the time it took for
    // the sensor to be polled from the remaining delay so that
    // the beeps remain even

    if (time2-time1<30) {


    // delay

    i = 0;

    // resets the counter

    while (i < maxtime){ // do this until maxtime is reached

        if (i % 60 == 0){

        ++i; // increment counter

void check_distance(){
    // note the time before checking the sensor
    time1 = millis();

    // The sensor is triggered by a HIGH pulse of 10 or more
    // microseconds. Giving a short LOW pulse beforehand ensures a
    // clean HIGH pulse.

    digitalWrite(trigPin, LOW);
    digitalWrite(trigPin, HIGH);
    digitalWrite(trigPin, LOW);

    // read the signal from the sensor: a HIGH pulse whose duration
    // is the time (in microseconds) from the sending of the Ping
    // to the reception of its echo from an object. This will time
    // out after 30ms.

    duration = pulseIn(echoPin, HIGH);

    // note the time after checking the sensor time2 = millis();
    // translate the pulse duration into centimeters
    // The speed of sound is 340 m/s or 29 microseconds per
    // centimeter. The ping travels out and back, so to find the
    // distance of the object we take half the distance travelled.

    cm = duration / 29 / 2; maxtime = cm * scalingfactor;

    // Not sure why it's not working? Uncomment this to check that
    // your sensor is giving the correct output
    // Serial.print(duration);
    // Serial.print(" millis");
    // Serial.println();
    // Serial.print(cm);
    // Serial.print(" cm");
    // Serial.println();

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