Sanat Vidwans

Published November 2, 2026

Build an Arduino Ultrasonic Distance Meter with OLED and LED

Build an Arduino ultrasonic distance meter with an OLED display and LED proximity alert using the HC-SR04 sensor. Perfect for beginners!

IntermediateFull instructions provided5 hours9

Build an Arduino Ultrasonic Distance Meter with OLED and LED

Things used in this project

Hardware components

Arduino UNO R3 compatible development board – 1 Qty

from https://rajivelectronics.com

×

1

HC-SR04 ultrasonic distance sensor – 1 Qty

from https://rajivelectronics.com

×

1

0.96-inch I2C OLED display, 128x64 SSD1306 – 1 Qty

from https://rajivelectronics.com

×

1

Red LED – 1 Qty

from https://rajivelectronics.com

×

1

Breadboard

from https://rajivelectronics.com

×

1

Jumper wires – 1 Set

from https://rajivelectronics.com

×

1

Compatible USB data cable – 1 Qty

from https://rajivelectronics.com

×

1

Software apps and online services

Arduino IDE

Story

Build an Arduino Ultrasonic Distance Meter with OLED and LED Alert

Introduction

In this project, we will build a simple ultrasonic distance meter using an Arduino UNO, HC-SR04 ultrasonic sensor, and a 0.96-inch OLED display.

The system measures the distance between the sensor and an object, displays the result in centimetres, and activates a warning LED whenever an object comes within 15 cm.

This beginner-friendly electronics project demonstrates ultrasonic sensing, microcontroller programming, I2C communication, and proximity detection.

How It Works

The HC-SR04 sensor emits a short ultrasonic pulse and listens for the returning echo.

The Arduino measures the time between transmission and reception and estimates the distance using the approximate speed of sound.

Distance (cm) = Echo time (microseconds) × 0.0343 / 2

The calculated distance is displayed on the OLED screen.

When the measured distance is 15 cm or less, the warning LED switches on. When the object moves farther away, the LED switches off.

If no valid echo is received, the display shows "NO ECHO".

Components Required

Arduino UNO R3 compatible development board – 1 Qty

Arduino UNO R3 compatible development board – 1 Qty

HC-SR04 ultrasonic distance sensor – 1 Qty

HC-SR04 ultrasonic distance sensor – 1 Qty

0.96-inch I2C OLED display, 128x64 SSD1306 – 1 Qty

0.96-inch I2C OLED display, 128x64 SSD1306 – 1 Qty

Red LED – 1 Qty

Red LED – 1 Qty

220 Ohm resistor – 1 Qty

220 Ohm resistor – 1 Qty

Breadboard – 1 Qty

Breadboard – 1 Qty

Jumper wires – 1 Set

Jumper wires – 1 Set

Compatible USB data cable – 1 Qty

Compatible USB data cable – 1 Qty

Step 1: Connect the Ultrasonic Sensor

Connect the HC-SR04 sensor to the Arduino UNO:

VCC → Arduino 5V

VCC → Arduino 5V

GND → Arduino GND

GND → Arduino GND

TRIG → Digital Pin 9

TRIG → Digital Pin 9

ECHO → Digital Pin 10

ECHO → Digital Pin 10

The TRIG pin initiates the measurement, while the ECHO pin sends the returning pulse timing to the Arduino.

Step 2: Connect the OLED Display

Use a 4-pin SSD1306 I2C OLED module rated for 5V operation.

VCC → Arduino 5V

VCC → Arduino 5V

GND → Arduino GND

GND → Arduino GND

SDA → Arduino A4

SDA → Arduino A4

SCL → Arduino A5

SCL → Arduino A5

The OLED communicates using I2C, requiring only two signal connections.

Check your particular display's voltage rating before connecting power.

Step 3: Connect the Warning LED

Connect Arduino Digital Pin 6 through a 220 Ohm resistor to the LED anode.

Connect the LED cathode to Arduino GND.

The resistor limits LED current and protects the LED from excessive current.

Step 4: Install Arduino Libraries

Open the Arduino IDE and navigate to Library Manager.

Install:

Adafruit GFX Library

Adafruit GFX Library

Adafruit SSD1306

Adafruit SSD1306

Install any additional dependencies requested by the library manager.

Step 5: Upload the Arduino Code

Open the supplied Arduino sketch.

Select the appropriate Arduino UNO board and serial port.

Upload the program to the development board.

The sketch reads the ultrasonic sensor, calculates the distance, updates the OLED display, and controls the warning LED automatically.

Step 6: Test the Project

After uploading the code, place a flat object approximately 30 cm in front of the ultrasonic sensor.

The OLED should display the measured distance and indicate "STATUS: CLEAR".

Move the object closer than 15 cm.

The OLED should show "ALERT: TOO CLOSE", and the LED should illuminate.

Move the object away, and the warning LED should switch off.

Compare the measurements with a ruler to check the working accuracy of your assembled prototype.

Troubleshooting

OLED not displaying: Check power connections, SDA/SCL wiring, and the I2C address. The supplied code assumes address 0x3C.

No distance reading: Check the ultrasonic sensor's TRIG and ECHO connections, power supply, and target orientation.

LED not working: Check LED polarity, the series resistor, and the connection to Digital Pin 6.

Applications

Educational Arduino electronics projects

Educational Arduino electronics projects

Robotics obstacle detection demonstrations

Robotics obstacle detection demonstrations

Ultrasonic sensor experiments

Ultrasonic sensor experiments

Distance measurement prototypes

Distance measurement prototypes

Proximity warning systems

Proximity warning systems

STEM and engineering laboratory activities

STEM and engineering laboratory activities

Further Improvements

The project can be expanded with an audible buzzer, adjustable warning distance, or multiple indicator LEDs.

More advanced versions could include data logging or wireless monitoring using an ESP32 board.

About Rajiv Electronics

This educational project has been prepared by Rajiv Electronics, Pune, India, to help students, hobbyists, and electronics enthusiasts learn practical microcontroller interfacing.

Electronic components, development boards, sensors, and prototyping supplies are available at:

https://rajivelectronics.com/

Schematics

Code

Arduino Ultrasonic Distance Meter with OLED Display and LED Alert

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

#define TRIG_PIN 9
#define ECHO_PIN 10
#define LED_PIN 6

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
#define OLED_ADDRESS 0x3C

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

const float ALERT_DISTANCE = 15.0;

float measureDistance() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  unsigned long duration =
    pulseIn(ECHO_PIN, HIGH, 25000UL);

  if (duration == 0) return -1;

  float distance = duration * 0.0343 / 2.0;

  if (distance < 2 || distance > 400) return -1;

  return distance;
}

void setup() {
  Serial.begin(9600);

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);

  digitalWrite(TRIG_PIN, LOW);
  digitalWrite(LED_PIN, LOW);

  Wire.begin();

  if (!display.begin(
      SSD1306_SWITCHCAPVCC, OLED_ADDRESS)) {
    Serial.println("OLED initialization failed");
    while (true) {
      delay(1000);
    }
  }
}

void loop() {
  float distance = measureDistance();

  bool alert = distance >= 0 &&
               distance <= ALERT_DISTANCE;

  digitalWrite(LED_PIN, alert ? HIGH : LOW);

  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);

  display.setCursor(15, 0);
  display.println("DISTANCE METER");
  display.drawLine(0, 12, 127, 12, SSD1306_WHITE);

  if (distance < 0) {
    display.setTextSize(2);
    display.setCursor(20, 25);
    display.println("NO ECHO");
    Serial.println("No valid echo");
  } else {
    display.setTextSize(2);
    display.setCursor(10, 23);
    display.print(distance, 1);
    display.println(" cm");

    display.setTextSize(1);
    display.setCursor(8, 52);

    if (alert) {
      display.println("ALERT: TOO CLOSE");
    } else {
      display.println("STATUS: CLEAR");
    }

    Serial.print("Distance: ");
    Serial.print(distance, 1);
    Serial.println(" cm");
  }

  display.display();
  delay(200);
}

Credits

Sanat Vidwans

Sanat Vidwans

1 project • 0 followers

Thanks to Rajiv Electronics .

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