Arduino HC-SR04 Ultrasonic Sensor Distance Meter with SSD1306 OLED Display

Arduino HC-SR04 Ultrasonic Sensor Distance Meter with SSD1306 OLED Display

May 20 2025
By: Arduino_Master
0 Comments

Learn how to build an Arduino-based distance measurement device using the HC-SR04 ultrasonic sensor and a 128×64 I2C OLED (SSD1306). Displays accurate distances in millimeters, centimeters, and meters. Perfect for DIY robotics, water level monitoring, parking sensors, and more.

🧰 Usage Examples of the Ultrasonic Distance Meter Project

1. Obstacle Detection for Robots

Mounted on the front of a mobile robot or drone.
Measures distance to obstacles for collision avoidance.
Ideal for DIY line followers, maze solvers, and autonomous bots.

✅ Why it fits:

Fast, accurate short-range detection.
Small and lightweight.

2. Smart Parking Sensor

Mount near the rear of a car or garage wall.
Shows exact distance between the vehicle and wall.

✅ Benefits:

Visual feedback in cm/mm helps with safe parking.
Add a buzzer or LED for alerts at close distances.

3. Water Level Monitoring

Mount sensor on top of a water tank or well.
Measures distance to the water surface.

✅ Why useful:

Calculate water height by subtracting distance from tank height.
Add alert if water drops too low or fills up.

4. Height Measurement Tool

Hold the sensor above a surface or a person’s head.
Measure vertical distance from sensor to the floor or top of object.

✅ Example uses:

DIY digital ruler or measuring stick.
School science experiments.

5. Security or Presence Detection

Place near a door or entryway.
Detect people approaching (e.g., doorbell activator, light on, etc.)

✅ Enhancements:

Trigger camera, log time, or activate a servo.

6. Industrial or Factory Use

Measure part position or distance on conveyor belts.
Detect material levels in bins or chutes.

✅ Why it’s practical:

Non-contact measurement.
Easy integration with microcontrollers and automation systems.

7. DIY Measuring Device

Handheld or wall-mounted tool to measure distance to objects.
Display in mm/cm/m makes it suitable for builders or hobbyists.

✅ Additions:

Save measurements to SD card.
Use buttons to scroll or reset.

Bonus 💡: Educational Use

Demonstrates:
- Physics (speed of sound, time-distance relationships).
- Embedded systems (sensors, timing with millis(), displays).
- Clean coding practices (non-blocking loops, sensor integration).

🧠 How It Works

🌀 1. Distance Measurement Using HC-SR04

The HC-SR04 has two pins:
- Trig (Trigger): Sends a short sound pulse.
- Echo: Receives the pulse after it bounces off an object.

✅ Process:

digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);   // Start ultrasonic pulse
delayMicroseconds(10);
digitalWrite(trigPin, LOW);    // End pulse

The pulseIn(echoPin, HIGH) measures the duration (in microseconds) that the Echo pin stays HIGH, i.e., how long it took for the echo to return.

✅ Convert time to distance:

distance_cm = duration * 0.0343 / 2;

0.0343 cm/µs is the speed of sound in air.
Divide by 2 because the pulse goes to the object and back.

💡 2. Distance Display on OLED

After calculating the distance:

In meters, centimeters, and millimeters,
The result is printed to the 128×64 pixel SSD1306 OLED display using:

display.setCursor(x, y);
display.print("Meters: ");
display.print(distance_m, 3);

This updates every 500 milliseconds.

⏲️ 3. millis() for Non-blocking Timing

Instead of delay(500), we use:

unsigned long currentMillis = millis();

if (currentMillis - previousMillis >= interval) {
  previousMillis = currentMillis;
  // Do distance measurement + display update
}

millis() gives the number of milliseconds since the program started.
This lets the loop run constantly, and only triggers the measurement every 500ms, without blocking other tasks.
Great for multitasking (e.g., button reading, networking, etc.).

✅ Summary

Part	Role
`millis()`	Controls when to take measurements (non-blocking)
`pulseIn()`	Measures echo return time
Distance formulas	Convert echo time to distance
OLED display	Shows distance in m, cm, mm
No `delay()`	Makes code responsive and multitask-friendly

📌 Notes

The 0.0343 factor is the speed of sound in cm/µs.
Make sure your OLED is on address 0x3C. Use an I2C scanner if unsure.
Adjust trigPin and echoPin if using other boards like ESP8266 or ESP32.

Here’s a complete Arduino sketch to measure distance using the HC-SR04 ultrasonic sensor and display the result in meters, centimeters, and millimeters on a 128×64 I2C OLED display (SSD1306).

✅ Required Libraries

Adafruit SSD1306
Adafruit GFX
(Install via Arduino Library Manager)

🧰 Wiring

HC-SR04:

VCC → 5V
GND → GND
Trig → D9
Echo → D8

OLED (SSD1306 I2C):

VCC → 3.3V or 5V
GND → GND
SCL → A5 (on UNO)
SDA → A4 (on UNO)

(Adjust pins for ESP32 / ESP8266 or other boards accordingly.)

✅ Code (Arduino Sketch)

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// HC-SR04 Pins
const int trigPin = 9;
const int echoPin = 8;

// Timing control
unsigned long previousMillis = 0;
const unsigned long interval = 500; // 500 ms between readings

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

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("SSD1306 allocation failed");
    while (true);
  }

  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println("Ultrasonic Distance");
  display.display();
  delay(2000); // Initial display only
}

void loop() {
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;

    long duration;
    float distance_cm, distance_m, distance_mm;

    // Send ultrasonic pulse
    digitalWrite(trigPin, LOW);
    delayMicroseconds(2);
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(10);
    digitalWrite(trigPin, LOW);

    // Read echo time
    duration = pulseIn(echoPin, HIGH);

    // Distance calculations
    distance_cm = duration * 0.0343 / 2;
    distance_m = distance_cm / 100.0;
    distance_mm = distance_cm * 10.0;

    // Debug output
    Serial.print("Distance: ");
    Serial.print(distance_m, 3);
    Serial.print(" m, ");
    Serial.print(distance_cm, 2);
    Serial.print(" cm, ");
    Serial.print(distance_mm, 1);
    Serial.println(" mm");

    // OLED output
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println("Ultrasonic Sensor");

    display.setCursor(0, 16);
    display.print("Meters: ");
    display.print(distance_m, 3);

    display.setCursor(0, 32);
    display.print("Centimeters: ");
    display.print(distance_cm, 2);

    display.setCursor(0, 48);
    display.print("Millimeters: ");
    display.print(distance_mm, 1);

    display.display();
  }
}

✅ Conclusion

This Arduino project using the HC-SR04 ultrasonic sensor and 128×64 I2C OLED display is a simple yet powerful way to measure distances with high precision in millimeters, centimeters, and meters. By using millis() instead of delay(), it stays responsive and ready for expansion—perfect for real-world applications like:

Obstacle avoidance in robotics
Smart parking sensors
Water level monitoring
DIY measuring tools
Educational demonstrations

Whether you’re a beginner learning sensors or a maker building smarter devices, this project lays a solid foundation for adding intelligent distance-sensing capabilities to your Arduino-based systems.

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If you found this project helpful or inspiring, please consider sharing it with fellow makers and tech enthusiasts on social media! 🚀
Your support helps others discover useful tutorials like this, and motivates us to keep creating more.

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