Bat Goggles

Bat Goggles

These were developed to mimic as closely as possible bio-sonar using an Arduino, HC-SR04 Ultrasonic distance sensor and a piezo buzzer as part of a workshop to introduce school children to the basics of electronics and coding.


The circuit is very simple for this particular project. It proved cheaper to import Arduino's from China than to use a stripped down circuit such as the shrimp.


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();

Because of the age of the children involved in this workshop we didn't use the Arduino IDE to create the code, instead we used a graphical interface (Ardublockly). I added a few new blocks to make it work for what I wanted but unfortunately ran out of time to get my code merged into the main codebase.