ESP32 - Ultrasonic Sensor - Relay

We are going to learn how to:

By connecting relay to light bulb, led strip, motor or actuator... We can use the ultrasonic sensor to control light bulb, led strip, motor or actuator...

Hardware Required

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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About Relay and Ultrasonic Sensor

If you do not have knowledge of relay and ultrasonic sensor (pinout, how they work, how to connect them to ESP32, how to program for them...), learn about them in the following tutorials:

Wiring Diagram

ESP32 Ultrasonic Sensor Relay Wiring Diagram

Image is developed using Fritzing. Click to enlarge image

ESP32 Code

/* * Created by esp32io.com * * This example code is in the public domain * * Tutorial page: https://esp32io.com/tutorials/esp32-ultrasonic-sensor-relay */ // constants won't change const int TRIG_PIN = 23; // ESP32 pin GIOP23 connected to Ultrasonic Sensor's TRIG pin const int ECHO_PIN = 22; // ESP32 pin GIOP22 connected to Ultrasonic Sensor's ECHO pin const int RELAY_PIN = 27; // ESP32 pin GIOP27 connected to Relay's pin const int DISTANCE_THRESHOLD = 50; // centimeters // variables will change: 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 Steps

  • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE
  • Connect the ESP32 board to your PC via a micro USB cable
  • Open Arduino IDE, select the right ESP32 board and COM port
  • Copy the above code and paste it to Arduino IDE
  • Click Upload button on Arduino IDE to compile and upload code to ESP32 board
  • Arduino IDE Upload Code
  • Move your hand in front of sensor
  • See the change of relay's state

Code Explanation

Read the line-by-line explanation in comment lines of source code!

Video Tutorial

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