ESP8266 - Ultrasonic Sensor - Servo Motor

This tutorial instructs you how to use ESP8266 and ultrasonic sensor to control servo motor. In detail:

Hardware Preparation

1×ESP8266 NodeMCU
1×Micro USB Cable
1×Ultrasonic Sensor
1×Servo Motor
1×Jumper Wires
1×(Optional) 5V Power Adapter for ESP8266
1×(Optional) ESP8266 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)
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Overview of Servo Motor and Ultrasonic Sensor

If you are unfamiliar with servo motors and ultrasonic sensors (including pinout, functionality, and programming), the following tutorials can provide some guidance:

Wiring Diagram

The wiring diagram between ESP8266 NodeMCU and Ultrasonic Sensor Servo Motor

This image is created using Fritzing. Click to enlarge image

See more in ESP8266's pinout and how to supply power to the ESP8266 and other components.

Please note that the wiring diagram shown above is only suitable for a servo motor with low torque. In case the motor vibrates instead of rotating, an external power source must be utilized to provide more power for the servo motor. The below demonstrates the wiring diagram with an external power source for servo motor.

The wiring diagram between ESP8266 NodeMCU and Ultrasonic Sensor Servo Motor Power

This image is created using Fritzing. Click to enlarge image

Please do not forget to connect GND of the external power to GND of ESP8266.

ESP8266 Code - Ultrasonic Sensor Controls Servo Motor

/* * This ESP8266 NodeMCU code was developed by * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * */ #include <Servo.h> #define TRIG_PIN D1 // The ESP8266 pin connected to Ultrasonic Sensor's TRIG pin #define ECHO_PIN D2 // The ESP8266 pin connected to Ultrasonic Sensor's ECHO pin #define SERVO_PIN D7 // The ESP8266 pin connected to Servo Motor's pin #define DISTANCE_THRESHOLD 50 // centimeters Servo servo; // create servo object to control a servo float duration_us, distance_cm; void setup() { Serial.begin (9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(TRIG_PIN, OUTPUT); // Configure the ESP8266 pin to the output mode pinMode(ECHO_PIN, INPUT); // Configure the ESP8266 pin to the input mode servo.attach(SERVO_PIN); // attaches the servo on pin 9 to the servo object servo.write(0); } void loop() { // Produce a 10-microsecond pulse to the TRIG pin. digitalWrite(TRIG_PIN, HIGH); delayMicroseconds(10); digitalWrite(TRIG_PIN, LOW); // Measure the pulse duration from the ECHO pin duration_us = pulseIn(ECHO_PIN, HIGH); // calculate the distance distance_cm = 0.017 * duration_us; if (distance_cm < DISTANCE_THRESHOLD) servo.write(90); // rotate servo motor to 90 degree else servo.write(0); // rotate servo motor to 0 degree // print the value to Serial Monitor Serial.print("distance: "); Serial.print(distance_cm); Serial.println(" cm"); delay(500); }

Detailed Instructions

To get started with ESP8266 on Arduino IDE, follow these steps:

  • Check out the how to setup environment for ESP8266 on Arduino IDE tutorial if this is your first time using ESP8266.
  • Wire the components as shown in the diagram.
  • Connect the ESP8266 board to your computer using a USB cable.
  • Open Arduino IDE on your computer.
  • Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
  • Connect a USB cable to the ESP8266 and the PC.
  • Launch the Arduino IDE, select the appropriate board and port.
  • Copy the code above and open it in the Arduino IDE.
  • Click the Upload button on the Arduino IDE to compile and upload the code to the ESP8266.
  • Move your hand in front of the sensor.
  • Check out the servo motor's response.


The code above is meant for educational purposes. The ultrasonic sensor is highly susceptible to noise. If you plan to use it in a real-world application, it is necessary to filter out the noise for the ultrasonic sensor. For more information on how to do this, please refer to how to filter noise for ultrasonic sensor.

Video Tutorial


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