Arduino Project

Arduino Ultrasonic Distance Meter with OLED V7

Kit purchase

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Name	Includes Arduino board	PURCHASE LINK
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
3 in 1 Ultimate Starter Kit	Arduino Uno R4 Minima	BUY
Ultimate Sensor Kit	Arduino Uno R4 Minima	BUY
Universal Maker Sensor Kit	×	BUY

Course Introduction

In this project, we use an HC-SR04 ultrasonic sensor, an OLED display, and an active buzzer with the Arduino UNO R4 WiFi to create a distance alarm system.

The OLED displays the measured distance in real time. As an object gets closer, the buzzer beeps faster and sounds continuously when the distance is below 7 cm.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

1.1 Install Arduino IDE(Important)
1.2 Introduction of Arduino IDE

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 WIFI	1	BUY
2	USB Type-C cable	1	×
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	Ultrasonic Sensor Module	1	BUY
6	OLED Display Module	1	BUY
7	Active Buzzer	1	×

Wiring

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Common Connections:

OLED Display Module
SDA: Connect to SDA on the Arduino.
SCK: Connect to SCL on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.

Ultrasonic Sensor Module
Trig: Connect to 10 on the Arduino.
Echo: Connect to 11 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.

Active Buzzer
＋: Connect to 2 on the Arduino.
－: Connect to breadboard’s negative power bus.

Writing the Code

Note
You can copy this code into Arduino IDE.
To install the library, use the Arduino Library Manager and search for Adafruit SSD1306 and Adafruit GFX and install it.
Don’t forget to select the board(Arduino UNO R4 WIFI) and the correct port before clicking the Upload button.

 /*
  Arduino Distance Alarm 6.0

  Board: Arduino UNO R4 WiFi
  Components:
  - HC-SR04 Ultrasonic Sensor
  - SSD1306 OLED Display
  - Active Buzzer

  Distance >= 18 cm: Buzzer OFF
  Distance < 18 cm: Slow beeps
  Distance < 12 cm: Fast beeps
  Distance < 7 cm: Continuous beep
*/

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

// Define pins
#define TRIG_PIN 10
#define ECHO_PIN 11
#define BUZZER_PIN 2

// OLED settings
#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
);

// Distance thresholds
const float SLOW_DISTANCE = 18.0;
const float FAST_DISTANCE = 12.0;
const float CONTINUOUS_DISTANCE = 7.0;

// Buzzer timing
const unsigned long SLOW_ON_TIME = 200;
const unsigned long SLOW_OFF_TIME = 500;

const unsigned long FAST_ON_TIME = 150;
const unsigned long FAST_OFF_TIME = 150;

// Sensor timing
const unsigned long SENSOR_INTERVAL = 100;

unsigned long lastSensorTime = 0;
unsigned long lastBuzzerChange = 0;

// Distance values
float distance = -1;
float filteredDistance = -1;

// Buzzer state
bool buzzerOn = false;
int currentMode = -1;

// Read distance
float readDistance() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

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

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

  if (duration == 0) {
    return -1;
  }

  return duration * 0.0343 / 2.0;
}

// Update distance with simple filtering
void updateDistance() {
  float newDistance = readDistance();

  if (newDistance < 0) {
    distance = -1;
    filteredDistance = -1;
    return;
  }

  // Smooth sudden changes
  if (filteredDistance < 0) {
    filteredDistance = newDistance;
  } else {
    filteredDistance =
      filteredDistance * 0.6 +
      newDistance * 0.4;
  }

  distance = filteredDistance;
}

// Display distance on OLED
void updateDisplay() {
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);

  display.setTextSize(1);
  display.setCursor(0, 5);
  display.println("Distance Alarm");

  display.drawLine(
    0, 18, 128, 18, SSD1306_WHITE
  );

  if (distance < 0) {
    display.setTextSize(2);
    display.setCursor(12, 30);
    display.println("No Echo");
  } else {
    display.setTextSize(2);
    display.setCursor(0, 30);
    display.print(distance, 1);
    display.print(" CM");
  }

  display.display();
}

// Get alarm mode
int getBuzzerMode() {
  if (distance < 0) return 0;

  if (distance < CONTINUOUS_DISTANCE) {
    return 3;
  }

  if (distance < FAST_DISTANCE) {
    return 2;
  }

  if (distance < SLOW_DISTANCE) {
    return 1;
  }

  return 0;
}

// Set buzzer output
void setBuzzer(bool state) {
  buzzerOn = state;

  digitalWrite(
    BUZZER_PIN,
    state ? HIGH : LOW
  );
}

// Control buzzer without delay
void updateBuzzer(unsigned long now) {
  int mode = getBuzzerMode();

  // Start beeping immediately when mode changes
  if (mode != currentMode) {
    currentMode = mode;
    lastBuzzerChange = now;

    if (mode == 0) {
      setBuzzer(false);
    } else {
      setBuzzer(true);
    }

    return;
  }

  // Safe distance
  if (mode == 0) {
    setBuzzer(false);
    return;
  }

  // Continuous beep below 7 cm
  if (mode == 3) {
    setBuzzer(true);
    return;
  }

  unsigned long onTime;
  unsigned long offTime;

  if (mode == 1) {
    onTime = SLOW_ON_TIME;
    offTime = SLOW_OFF_TIME;
  } else {
    onTime = FAST_ON_TIME;
    offTime = FAST_OFF_TIME;
  }

  unsigned long elapsed =
    now - lastBuzzerChange;

  // Turn off after ON time
  if (buzzerOn && elapsed >= onTime) {
    setBuzzer(false);
    lastBuzzerChange = now;
  }

  // Turn on after OFF time
  else if (!buzzerOn && elapsed >= offTime) {
    setBuzzer(true);
    lastBuzzerChange = now;
  }
}

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

  // Initialize pins
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  digitalWrite(TRIG_PIN, LOW);
  setBuzzer(false);

  // Initialize OLED
  if (!display.begin(
        SSD1306_SWITCHCAPVCC,
        OLED_ADDRESS
      )) {
    Serial.println("OLED failed!");

    while (true) {
      setBuzzer(false);
      delay(1000);
    }
  }

  display.clearDisplay();
  display.display();

  Serial.println("Distance Alarm Ready!");
}

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

  // Update sensor every 100 ms
  if (now - lastSensorTime >= SENSOR_INTERVAL) {
    lastSensorTime = now;

    updateDistance();
    updateDisplay();

    // Serial Monitor
    Serial.print("Distance: ");

    if (distance < 0) {
      Serial.print("No Echo");
    } else {
      Serial.print(distance, 1);
      Serial.print(" cm");
    }

    Serial.print(" | Mode: ");
    Serial.println(getBuzzerMode());
  }

  // Update buzzer continuously
  updateBuzzer(millis());

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Arduino Project

Arduino Ultrasonic Distance Meter with OLED V7

Kit purchase

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino Ultrasonic Distance Meter with OLED V7

Kit purchase

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

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