ESP32 - Ultrasonic Sensor - Relay

This tutorial instructs you how to use ESP32 and Ultrasonic sensor to control the relay. In detail:

We can extend this tutorial to use the ultrasonic sensor to control a led strip, siren, light bulb, or motor... by connnecting them to the relay.

Hardware Used In This Tutorial

1×ESP-WROOM-32 Dev Module
1×Micro USB Cable
1×Ultrasonic Sensor
1×Relay
1×Warning Light Bright Waterproof
1×12V Power Adapter
n×Jumper Wires
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Introduction to Relay and Ultrasonic Sensor

We have specific tutorials about relay and ultrasonic sensor. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:

Wiring Diagram

wiring diagram between esp32 ultrasonic sensor relay

This image is created using Fritzing. Click to enlarge image

ESP32 Code

/* * 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-ultrasonic-sensor-relay */ #define TRIG_PIN 23 // ESP32 pin GIOP23 connected to Ultrasonic Sensor's TRIG pin #define ECHO_PIN 22 // ESP32 pin GIOP22 connected to Ultrasonic Sensor's ECHO pin #define RELAY_PIN 27 // ESP32 pin GIOP27 connected to Relay's pin #define DISTANCE_THRESHOLD 50 // centimeters // The below are variables, which can be changed float duration_us, distance_cm; void setup() { Serial.begin (9600); // initialize serial port pinMode(TRIG_PIN, OUTPUT); // set ESP32 pin to output mode pinMode(ECHO_PIN, INPUT); // set ESP32 pin to input mode pinMode(RELAY_PIN, OUTPUT); // set ESP32 pin to output mode } 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; if (distance_cm < DISTANCE_THRESHOLD) digitalWrite(RELAY_PIN, HIGH); // turn on Relay else digitalWrite(RELAY_PIN, LOW); // turn off Relay // print the value to Serial Monitor Serial.print("distance: "); Serial.print(distance_cm); Serial.println(" cm"); delay(500); }

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.
  • Copy the above code and paste it to Arduino IDE.
  • Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
  • Arduino IDE Upload Code
  • Move your hand in front of sensor
  • See the change of relay's state

Line-by-line Code Explanation

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

Video Tutorial

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