ESP32 - Sound Sensor - Servo Motor

In this tutorial, we'll explore how to utilize the sound sensor to control servo motor. Specifically, we'll delve into two exciting applications:

Sound switch: When sound is detected (e.g knock), the ESP32 rotates servo motor to 90 degree if it's in 0 degree, and 0 degree if it's in 90 degree.
Sound-activated relay: Upon detecting sound, the ESP32 rotates servo motor to 90 degree for a specific period of time, and then rotates back to 0 degree.

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	Sound Sensor
1	×	Servo Motor
1	×	Jumper Wires
1	×	(Recommended) ESP32 Screw Terminal Adapter

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Disclosure: some of these links are affiliate links. We may earn a commission on your purchase at no extra cost to you. We appreciate it.

Introduction to Servo Motor and Sound Sensor

If you do not know about servo motor and sound sensor (pinout, how it works, how to program ...), learn about them in the following tutorials:

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.

ESP32 Code - Sound Switch toggles Angle of Servo Motor

The below code toggles the angle of servo motor between 0 and 90 degree each time the sound is detected.

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-sound-sensor-servo-motor */ #include <Servo.h> #define SENSOR_PIN 25 // The ESP32 pin GPIO25 connected to the sound sensor #define SERVO_PIN 26 // The ESP32 pin GPIO26 connected to the servo motor Servo servo; // create servo object to control a servo // variables will change: int angle = 0; // the current angle of servo motor int prev_sound_state; // the previous state of sound sensor int sound_state; // the current state of sound sensor void setup() { Serial.begin(9600); // initialize serial pinMode(SENSOR_PIN, INPUT); // set ESP32 pin to input mode servo.attach(SERVO_PIN); // attaches the servo on pin 9 to the servo object servo.write(angle); sound_state = digitalRead(SENSOR_PIN); } void loop() { prev_sound_state = sound_state; // save the last state sound_state = digitalRead(SENSOR_PIN); // read new state if (prev_sound_state == HIGH && sound_state == LOW) { // state change: HIGH -> LOW Serial.println("The sound has been detected"); // change angle of servo motor if (angle == 0) angle = 90; else if (angle == 90) angle = 0; // control servo motor arccoding to the angle servo.write(angle); } }

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Do the wiring as above image.
Connect the ESP32 board to your PC via a micro USB cable
Open Arduino IDE on your PC.
Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
Click to the Libraries icon on the left bar of the Arduino IDE.
Type ServoESP32 on the search box, then look for the servo library by Jaroslav Paral. Please be aware that both version 1.1.1 and 1.1.0 are affected by bugs. Kindly choose a different version.
Click Install button to install servo motor library for ESP32.

Connect ESP32 to PC via USB cable
Open Arduino IDE, select the right board and port
Copy the above code and open with Arduino IDE
Click Upload button on Arduino IDE to upload code to ESP32
Clap your hand in front of the sound sensor
See the change of servo motor

ESP32 Code - Sound-activated Servo Motor for a period of time

The below code rotates the servo motor to 90 degree for a period of time when the sound is detected. After the period of time, the servo motor is rotated back to 0 degree.

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-sound-sensor-servo-motor */ #include <Servo.h> #define SENSOR_PIN 25 // The ESP32 pin GPIO25 connected to the sound sensor #define SERVO_PIN 26 // The ESP32 pin GPIO26 connected to the servo motor #define TIME_PERIOD 5000 // in milliseconds Servo servo; // create servo object to control a servo // variables will change: int prev_sound_state; // the previous state of sound sensor int sound_state; // the current state of sound sensor void setup() { Serial.begin(9600); // initialize serial pinMode(SENSOR_PIN, INPUT); // set ESP32 pin to input mode servo.attach(SERVO_PIN); // attaches the servo on pin 9 to the servo object servo.write(0); sound_state = digitalRead(SENSOR_PIN); } void loop() { prev_sound_state = sound_state; // save the last state sound_state = digitalRead(SENSOR_PIN); // read new state if (prev_sound_state == HIGH && sound_state == LOW) { // state change: HIGH -> LOW Serial.println("The sound has been detected"); servo.write(90); // control servo motor to 90 degree delay(TIME_PERIOD); servo.write(0); // control servo motor to 0 degree } }

Please take note that the code mentioned above utilizes the delay() function for simplicity. However, if you incorporate additional code, it may get blocked during the delay time. To address this, the following code implements a non-blocking approach using the millis() function instead of delay to prevent blocking.

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-sound-sensor-servo-motor */ #include <Servo.h> #define SENSOR_PIN 25 // The ESP32 pin GPIO25 connected to the sound sensor #define SERVO_PIN 26 // The ESP32 pin GPIO26 connected to the servo motor #define TIME_PERIOD 5000 // in milliseconds Servo servo; // create servo object to control a servo // variables will change: int prev_sound_state; // the previous state of sound sensor int sound_state; // the current state of sound sensor unsigned long lastTime; // the current state of sound sensor int angle = 0; void setup() { Serial.begin(9600); // initialize serial pinMode(SENSOR_PIN, INPUT); // set ESP32 pin to input mode servo.attach(SERVO_PIN); // attaches the servo on pin 9 to the servo object servo.write(angle); sound_state = digitalRead(SENSOR_PIN); } void loop() { prev_sound_state = sound_state; // save the last state sound_state = digitalRead(SENSOR_PIN); // read new state if (prev_sound_state == HIGH && sound_state == LOW) { // state change: HIGH -> LOW Serial.println("The sound has been detected"); angle = 90; servo.write(angle); // control servo motor to 90 degree lastTime = millis(); } if (angle == 90 && (millis() - lastTime) > TIME_PERIOD) { angle = 0; servo.write(angle); // control servo motor to 0 degree } }

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