ESP32 - Ultrasonic Sensor

This tutorial instructs you how to use ESP32 with the ultrasonic sensor HC-SR04 to measure the distance to an object.

Hardware Used In This Tutorial

1×ESP-WROOM-32 Dev Module
1×USB Cable Type-C
1×Ultrasonic Sensor
1×Jumper Wires
1×(Optional) DC Power Jack
1×(Recommended) ESP32 Screw Terminal Adapter

Or you can buy the following sensor kit:

1×DIYables Sensor Kit 30 types, 69 units
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Introduction to Ultrasonic Sensor

The ultrasonic sensor HC-SR04 is used to measure the distance from the sensor to an object by using ultrasonic waves.

Ultrasonic Sensor Pinout

The ultrasonic sensor HC-SR04 includes four pins:

  • VCC pin: connect this pin to VCC (5V)
  • GND pin: connect this pin to GND (0V)
  • TRIG pin: this pin receives a control pulse from ESP32.
  • ECHO pin: this pin generates a pulse corresponding to the measured distance to ESP32.
Ultrasonic Sensor Pinout
image source:

How Ultrasonic Sensor Works

See How Ultrasonic Sensor Work

Wiring Diagram between Ultrasonic Sensor and ESP32

The wiring diagram with power supply from USB cable

ESP32 Ultrasonic Sensor Wiring Diagram

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

The wiring diagram with power supply from 5v adapter

ESP32 Ultrasonic Sensor Wiring Diagram

This image is created using Fritzing. Click to enlarge image

How To Program Ultrasonic Sensor

digitalWrite(23, HIGH); delayMicroseconds(10); digitalWrite(23, LOW);
  • Measures the pulse duration (µs) in ESP32's pin by using pulseIn() function. For example, pin GPIO22:
duration_us = pulseIn(22, HIGH);
  • Calculate distance (cm):
distance_cm = 0.017 * duration_us;

ESP32 Code

/* * This ESP32 code is created by * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit */ #define TRIG_PIN 23 // ESP32 pin GPIO23 connected to Ultrasonic Sensor's TRIG pin #define ECHO_PIN 22 // ESP32 pin GPIO22 connected to Ultrasonic Sensor's ECHO pin float duration_us, distance_cm; void setup() { // begin serial port Serial.begin (9600); // configure the trigger pin to output mode pinMode(TRIG_PIN, OUTPUT); // configure the echo pin to input mode pinMode(ECHO_PIN, INPUT); } void loop() { // generate 10-microsecond pulse to TRIG pin digitalWrite(TRIG_PIN, HIGH); delayMicroseconds(10); digitalWrite(TRIG_PIN, LOW); // measure duration of pulse from ECHO pin duration_us = pulseIn(ECHO_PIN, HIGH); // calculate the distance distance_cm = 0.017 * duration_us; // print the value to Serial Monitor Serial.print("distance: "); Serial.print(distance_cm); Serial.println(" cm"); delay(500); }

Quick Instructions

How to upload ESP32 code on Arduino IDE
  • Open Serial Monitor on Arduino IDE
How to open serial monitor on Arduino IDE
  • Move your hand in front of ultrasonic sensor
  • See the distance from the sensor to your hand on Serial Monitor
distance: 19.4 cm distance: 17.6 cm distance: 16.9 cm distance: 27.4 cm distance: 26.9 cm distance: 24.3 cm distance: 25.6 cm distance: 23.1 cm
Autoscroll Show timestamp
Clear output
9600 baud  

Line-by-line Code Explanation

The above ESP32 code contains line-by-line explanation. Please read the comments in the code!

How to Filter Noise from Distance Measurements of Ultrasonic Sensor

See How to Filter Noise from Distance Measurements of Ultrasonic Sensor

Video Tutorial

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