mattnett: Arduino - How to detect obstacles/objects and react?

How to detect an obstacle with an Arduino and HC-SR04 Ultrasonic Module?

In this post we will detect an obstacle using the HC-SR04 Ultrasonic Ranging module with an Arduino. Basically, we will write an embedded C program for Arduino to read the Ultrasonic sensor data every second, followed by converting the sensor data into distance and in the end run a piece of logic that if the detected object (i.e. motion due to moving object) is within 10 centimeters then a Piezo Buzzer will be beeped. Check out the Youtube video below demonstrating my experiment with detecting motion.

The breadboard setup for detecting an obstacle has been provided below as a reference. You may use this wiring scheme for hooking up your HC-SR04 along with the Piezo Buzzer to your Arduino. Be careful not to connect the wrong wires, as it might result in a short circuit.

Figure 1 - Breadboard Wiring for obstacle detection

The figure below shows the schematic wiring diagram for detecting an obstacle.

Figure 2 - Schematic wiring for obstacle detection

Join the wiring as follows:

HC-SR04: Connect Vcc (on HC-SR04) to 5V (on Arduino)
HC-SR04: Connect Gnd (on HC-SR04) to Gnd (on Arduino)
HC-SR04: Connect Trig (on HC-SR04) to Pin 4 (on Arduino)
HC-SR04: Connect Echo (on HC-SR04) to Pin 12 (on Arduino)
Piezo Buzzer: Connect the + Terminal (Longer leg) to Pin 8 (on Arduino)
Piezo Buzzer: Connect the - Terminal (Shorter leg) to Gnd (on Arduino)

That C sketch for detecting an obstacle with the Arduino is very simple and is provided for reference below.

int trigPin = 4;
int echoPin = 12;
int buzzerPin = 8;

void setup()
{
  // initialize the pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
}

void loop()
{
  long duration, distance;

// Signal a quick LOW just before giving a HIGH signal
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

// After 2 milli-seconds of LOW signal, give a HIGH signal to trigger the sensor
  digitalWrite(trigPin, HIGH);
  // Keep the digital signal HIGH for
  // at least 10 milli-seconds (required by HC-SR04 to activate emission of
  // ultra sonic waves
  delayMicroseconds(10);

// After 10 milli-seconds, signal a LOW
  digitalWrite(trigPin, LOW);

// Now wait for the Ultra sonic echo to return from an obstacle
  duration = pulseIn(echoPin, HIGH);

// Convert the distance to centimeters
  distance = (duration/2) / 29.1;

if (distance < 80)
  {
    //Serial.print(distance);
    //Serial.println(" cm");
    buzz();
  }

delay(250);
}

void buzz()
{
  tone(buzzerPin, 500, 250);
}

Hope you enjoyed this post. Please share this post if you found it useful and write your comments below this post. I would love to read your your thoughts and experiences with the HC-SR04 Ultrasonic Ranging module.

In my next post, I will show you how you can use your Arduino and HC-SR04 to create a reverse parking alarm for a car!

Cheers!
KBRC

Arduino - How to detect obstacles/objects and react?

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