Object Detection

Note

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes ESP32 board	PURCHASE LINK
ESP32 Ultimate Starter Kit	ESP32 WROOM 32E +	BUY
Universal Maker Sensor Kit		BUY

Course Introduction

This ESP32 project uses an IR sensor to detect obstacles. When an object is detected, a passive buzzer plays two alert tones (C5 and G5).

If no obstacle is present, the buzzer stays off. It’s a simple alert system for object detection.

Note

If this is your first time working with an ESP32 project, we recommend downloading and reviewing the basic materials first.

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	ESP-WROOM-32 ESP32 ESP-32S Development Board	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	IR Obstacle Avoidance Sensor Module	1	BUY
6	Passive Buzzer	1	BUY

Wiring

Common Connections:

Passive Buzzer
- ＋: Connect to GPIO4 on the ESP32.
- －: Connect to breadboard’s negative power bus.
IR Obstacle Avoidance Sensor Module
- OUT: Connect to GPIO23 on the ESP32.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.

Writing the Code

Note

Before you begin, you need to upload the pitches.h library to your Arduino. Copy the contents of the library into the Arduino IDE, save it as pitches.h and then upload it to your Arduino.

#define NOTE_B0  31
#define NOTE_C1  33
#define NOTE_CS1 35
#define NOTE_D1  37
#define NOTE_DS1 39
#define NOTE_E1  41
#define NOTE_F1  44
#define NOTE_FS1 46
#define NOTE_G1  49
#define NOTE_GS1 52
#define NOTE_A1  55
#define NOTE_AS1 58
#define NOTE_B1  62
#define NOTE_C2  65
#define NOTE_CS2 69
#define NOTE_D2  73
#define NOTE_DS2 78
#define NOTE_E2  82
#define NOTE_F2  87
#define NOTE_FS2 93
#define NOTE_G2  98
#define NOTE_GS2 104
#define NOTE_A2  110
#define NOTE_AS2 117
#define NOTE_B2  123
#define NOTE_C3  131
#define NOTE_CS3 139
#define NOTE_D3  147
#define NOTE_DS3 156
#define NOTE_E3  165
#define NOTE_F3  175
#define NOTE_FS3 185
#define NOTE_G3  196
#define NOTE_GS3 208
#define NOTE_A3  220
#define NOTE_AS3 233
#define NOTE_B3  247
#define NOTE_C4  262
#define NOTE_CS4 277
#define NOTE_D4  294
#define NOTE_DS4 311
#define NOTE_E4  330
#define NOTE_F4  349
#define NOTE_FS4 370
#define NOTE_G4  392
#define NOTE_GS4 415
#define NOTE_A4  440
#define NOTE_AS4 466
#define NOTE_B4  494
#define NOTE_C5  523
#define NOTE_CS5 554
#define NOTE_D5  587
#define NOTE_DS5 622
#define NOTE_E5  659
#define NOTE_F5  698
#define NOTE_FS5 740
#define NOTE_G5  784
#define NOTE_GS5 831
#define NOTE_A5  880
#define NOTE_AS5 932
#define NOTE_B5  988
#define NOTE_C6  1047
#define NOTE_CS6 1109
#define NOTE_D6  1175
#define NOTE_DS6 1245
#define NOTE_E6  1319
#define NOTE_F6  1397
#define NOTE_FS6 1480
#define NOTE_G6  1568
#define NOTE_GS6 1661
#define NOTE_A6  1760
#define NOTE_AS6 1865
#define NOTE_B6  1976
#define NOTE_C7  2093
#define NOTE_CS7 2217
#define NOTE_D7  2349
#define NOTE_DS7 2489
#define NOTE_E7  2637
#define NOTE_F7  2794
#define NOTE_FS7 2960
#define NOTE_G7  3136
#define NOTE_GS7 3322
#define NOTE_A7  3520
#define NOTE_AS7 3729
#define NOTE_B7  3951
#define NOTE_C8  4186
#define NOTE_CS8 4435
#define NOTE_D8  4699
#define NOTE_DS8 4978

Note

You can copy this code into Arduino IDE.
Don’t forget to select the board(ESP32 Dev module) and the correct port before clicking the Upload button.

// ESP32: IR obstacle + passive buzzer (C5/G5 tones), robust reads
const int SENSOR_PIN = 23;     // Sensor DO pin
const int BUZZER_PIN = 4;      // Passive buzzer pin
const bool ACTIVE_LOW = true;  // Set to false if your DO is HIGH on obstacle

const int FREQ_C5 = 523;       // Hz
const int FREQ_G5 = 784;       // Hz

void setup() {
  // Use pull-up to avoid floating if module DO is open-collector or weak
  pinMode(SENSOR_PIN, INPUT_PULLUP);
  pinMode(BUZZER_PIN, OUTPUT);
  Serial.begin(115200);
  Serial.println("ESP32 IR obstacle + buzzer ready.");
}

void loop() {
  int raw = digitalRead(SENSOR_PIN);
  bool obstacle = ACTIVE_LOW ? (raw == LOW) : (raw == HIGH);

  if (obstacle) {
    tone(BUZZER_PIN, FREQ_C5, 150);
    delay(150);
    tone(BUZZER_PIN, FREQ_G5, 150);
    delay(150);
  } else {
    noTone(BUZZER_PIN);
    delay(80);
  }
}