Overview
Things
Story

How the Project Works
Understanding the Arduino Code
1. Setup and Initialization
2. The Logic Loop
3. Refreshing the Display

Published February 21, 2026 © MIT

Arduino Mega Ultrasonic Distance Monitor with OLED

This project uses an ultrasonic sensor to detect distance and display it on an OLED Display with an Arduino Mega microcontroller.

BeginnerFull instructions provided1 hour228

Arduino Mega Ultrasonic Distance Monitor with OLED

Things used in this project

Hardware components

Arduino Mega 2560

ElectroPeak 0.96" OLED 64x128 Display Module

Ultrasonic Sensor - HC-SR04 (Generic)

Software apps and online services

Arduino IDE

Story

This project creates a real-time distance monitor by combining an HC-SR04 ultrasonic sensor with an SSD1306 OLED display controlled by an Arduino Mega.

How the Project Works

The system operates on a simple "send and receive" principle:

Triggering: The Arduino sends a short electrical pulse to the ultrasonic sensor.

Triggering: The Arduino sends a short electrical pulse to the ultrasonic sensor.

Sound Wave: The sensor converts this pulse into a high-frequency sound wave (ultrasonic) that travels through the air.

Sound Wave: The sensor converts this pulse into a high-frequency sound wave (ultrasonic) that travels through the air.

Reflection: When the sound hits an object, it bounces back as an echo.

Reflection: When the sound hits an object, it bounces back as an echo.

Measurement: The sensor detects the returning echo and sends a signal back to the Arduino. The Arduino measures how long the round trip took in microseconds.

Measurement: The sensor detects the returning echo and sends a signal back to the Arduino. The Arduino measures how long the round trip took in microseconds.

Calculation: The code converts this time into centimeters using the speed of sound.

Calculation: The code converts this time into centimeters using the speed of sound.

Display: The calculated distance is formatted and sent to the OLED screen via the I2C communication protocol (using pins 20 and 21).

Display: The calculated distance is formatted and sent to the OLED screen via the I2C communication protocol (using pins 20 and 21).

Understanding the Arduino Code

The code is structured into three main sections:

1. Setup and Initialization

Libraries: It includes the Adafruit_SSD1306 and Wire libraries to handle the complex communication needed for the OLED display.

Libraries: It includes the Adafruit_SSD1306 and Wire libraries to handle the complex communication needed for the OLED display.

Pin Definitions: It assigns the Trigger pin to D22 and the Echo pin to D23.

Pin Definitions: It assigns the Trigger pin to D22 and the Echo pin to D23.

Initialization: In setup(), it sets the pin modes and initializes the display. If the display isn't found at address 0x3C, the code stops to prevent errors.

Initialization: In setup(), it sets the pin modes and initializes the display. If the display isn't found at address 0x3C, the code stops to prevent errors.

2. The Logic Loop

The Pulse: To get a reading, the code pulls the trigPin HIGH for 10 microseconds and then LOW again. This "pokes" the sensor to send a sound wave.

The Pulse: To get a reading, the code pulls the trigPin HIGH for 10 microseconds and then LOW again. This "pokes" the sensor to send a sound wave.

The Math: It uses pulseIn() to catch the echo. It multiplies the duration by 0.034 (the speed of sound in cm/us) and divides by 2 (because the sound traveled to the object and back).

The Math: It uses pulseIn() to catch the echo. It multiplies the duration by 0.034 (the speed of sound in cm/us) and divides by 2 (because the sound traveled to the object and back).

3. Refreshing the Display

Clearing:display.clearDisplay() wipes the previous reading so numbers don't overlap.

Clearing:display.clearDisplay() wipes the previous reading so numbers don't overlap.

Formatting: It sets the text size to 2 and moves the "cursor" to the top-left corner.

Formatting: It sets the text size to 2 and moves the "cursor" to the top-left corner.

Output: Finally, display.display() is called. Without this specific command, the data remains in the Arduino's memory and never actually appears on the screen

Output: Finally, display.display() is called. Without this specific command, the data remains in the Arduino's memory and never actually appears on the screen

Code

arduino_ultrasonic_distance_monitor.ino

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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

const int trigPin = 22;
const int echoPin = 23;

void setup() {
  // put your setup code here, to run once:
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)){
    for(;;);
  }
  display.clearDisplay();
}

void loop() {
  // 1. Trigger the sensor
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW); // <--- ADD THIS: Stops the trigger pulse

  // 2. Measure the bounce
  long duration = pulseIn(echoPin, HIGH);
  int distance = (duration * 0.034) / 2; // (Using 0.034 for better accuracy)
  
  // 3. Update the OLED
  display.clearDisplay();
  display.setTextSize(2); // Size 3 might be too big for "Dist: 100cm"
  display.setTextColor(SSD1306_WHITE); // Explicitly set color just in case
  display.setCursor(0, 0);
  
  display.print("Dist: ");
  display.print(distance);
  display.print("cm");

  display.display(); // <--- ADD THIS: Actually pushes the data to the glass!
  
  delay(100); // Give the sensor a tiny rest
}

Credits

ZAIRobotics

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Arduino Mega Ultrasonic Distance Monitor with OLED