Step-by-Step Guide to Implementing Accurate Distance Measurement and Obstacle Avoidance with Arduino UNO and Ultrasonic Sensor

Only need 1 ultrasonic sensor + Arduino UNO, learn to measure object distance or achieve intelligent obstacle avoidance in 3 steps! From basic principles to complete code, even beginners can easily master it!

1. Project Highlights

✅ Low Cost: Materials cost less than 15 yuan✅ Easy to Learn: No complex circuit knowledge required✅ Highly Practical: Can be used in scenarios like robot obstacle avoidance, smart distance measuring devices, etc.✅ Strong Expandability: Can be combined with servos and motors for automatic navigation

2. Materials List

Component	Model/Parameters	Usage
Arduino UNO	Standard development board	Main control unit
HC-SR04 Ultrasonic Sensor	4.0-30cm distance measuring module	Measure distance or detect obstacles
Breadboard & Dupont Wires	For building circuits	–
LED Light (Optional)	For status indication	–

3. Hardware Connection Diagram

HC-SR04 → Arduino UNO:
  VCC → 5V           # Power positive
  GND → GND          # Common ground
  TRIG → D9           # Trigger signal output
  ECHO → D10          # Echo signal input

4. Core Code Implementation

const int trigPin =9;    // Trigger pin
const int echoPin =10;   // Echo pin
const long durationThreshold =20000; // 20cm maximum detection distance threshold

void setup(){
  Serial.begin(9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
}

void loop(){
// Send trigger signal
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);

// Read echo signal
long echoDuration = pulseIn(echoPin, HIGH);

// Calculate distance (cm)
float distance = echoDuration * 0.0343; // Speed of sound conversion factor

// Output result
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

// Optional: Add LED status indication
if(distance < 10){
    digitalWrite(LED_BUILTIN, HIGH); // Light up when close to obstacle
}else{
    digitalWrite(LED_BUILTIN, LOW);
}

delay(1000);
}

5. Detailed Working Principle

Trigger Signal: Send a 10μs high-level signal through the TRIG pin to activate the sensor
Echo Measurement: The sensor automatically emits ultrasonic waves and receives the reflected waves, the ECHO pin outputs the duration of the echo
Distance Calculation

    distance = (echoDuration * 0.0343) / 2; // Speed of sound 343m/s ÷ 2 (round trip distance)

Unit Conversion

<span> echoDuration × 0.0343</span> gives the distance in centimeters

Effective Range Minimum 2cm, maximum about 30cm (exceeding will return error value)

6. Debugging Tips

1. Test Sensor Functionality

Test with a known distance object (like a book), compare measured value with actual length
Example: A 20cm object should output about 58-60cm steadily (±5% affected by environmental humidity)

2. Solve Common Issues

Phenomenon	Solution
No measurement data	Check if the TRIG pin is sending the correct pulse
Data fluctuates wildly	Add a 100μF capacitor for filtering (between VCC and GND)
Measurement value too large	Ensure the object distance does not exceed 30cm

7. Extended Functions (Advanced Applications)

1. Obstacle Avoidance Car Implementation

#include <Servo.h>

Servo myservo; // Servo control
const int obstaclePin = A0;

void avoidObstacle(){
int distance = readUltrasonic();

if(distance < 20){ // Obstacle detected
    myservo.write(90); // Servo turns 90 degrees
    delay(1000);
    moveBackward();       // Move backward to avoid
}else{
    myservo.write(0);   // Move forward
    moveForward();
}
}

2. Automatic Door Control

// Open the door when someone approaches
if (distance < 50) {
  digitalWrite(motorPin, HIGH); // Start motor to open door
  delay(2000);
  digitalWrite(motorPin, LOW); // Stop motor
}

8. Precautions

Power Supply Requirements It is recommended to use a 5V regulated power supply to avoid voltage fluctuations affecting accuracy
Environmental Interference

Avoid using in strong electromagnetic field environments (like near speakers)
Measurement accuracy will decrease when measuring liquids or black light-absorbing materials

Sensor Protection Do not hit the probe emission surface with sharp objects

9. Application Scenarios

Smart Home Automatic curtain sensing open and close
Industrial Inspection Conveyor belt material size detection
Educational Experiments Physics class sound speed measurement teaching

Give it a try! If you successfully implement the distance measurement function, feel free to share your creative applications!