ESP8266 - Ultrasonic Sensor - LED

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

Hardware Preparation

1×ESP8266 NodeMCU
1×Micro USB Cable
1×Ultrasonic Sensor
1×220 ohm resistor
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 LED and Ultrasonic Sensor

If you are unfamiliar with LED and ultrasonic sensor (including pinout, functioning, programming, etc.), the following tutorials can help:

Wiring Diagram

The wiring diagram between ESP8266 NodeMCU and Ultrasonic Sensor LED

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.

ESP8266 Code

/* * 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: * */ #define TRIG_PIN D1 // The ESP8266 pin D1 connected to Ultrasonic Sensor's TRIG pin #define ECHO_PIN D2 // The ESP8266 pin D2 connected to Ultrasonic Sensor's ECHO pin #define LED_PIN D7 // The ESP8266 pin D7 connected to LED's pin #define DISTANCE_THRESHOLD 50 // centimeters 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 pinMode(LED_PIN, OUTPUT); // Configure the ESP8266 pin to the output mode } 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) digitalWrite(LED_PIN, HIGH); // turn on LED else digitalWrite(LED_PIN, LOW); // turn off LED // 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 your ESP8266 to your computer using a USB cable.
  • 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 in the Arduino IDE to send the code to the ESP8266.
Arduino IDE Upload Code
  • Move your hand in the vicinity of the sensor and
  • Observe the alteration in the state of the LED.

Code Explanation

Check out the line-by-line explanation contained in the comments of the source code!


The code above is for educational purposes. The ultrasonic sensor is very susceptible to interference. If you intend to use it in practice, you should filter out 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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