ESP32 - Touch Sensor Toggle Relay

This tutorial instructs you how to use ESP32 to toggle the a relay's state between ON and OFF when a touch sensor is touched. More specifically:

We can extend this tutorial to use the touch sensor to toggle the state of a solenoid, fan, light bulb, or actuator... by connnecting them to the relay.

Hardware Used In This Tutorial

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

We have specific tutorials about relay and touch 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 touch sensor relay

This image is created using Fritzing. Click to enlarge image

ESP32 Code - Touch Sensor Toggles Relay

/* * 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-touch-sensor-toggle-relay */ #define TOUCH_SENSOR_PIN 22 // ESP32 pin GIOP22 connected to touch sensor's pin #define RELAY_PIN 27 // ESP32 pin GIOP27 connected to relay's pin // The below are variables, which can be changed int relayState = LOW; // the current state of relay int lastTouchState; // the previous state of touch sensor int currentTouchState; // the current state of touch sensor void setup() { Serial.begin(9600); // initialize serial pinMode(TOUCH_SENSOR_PIN, INPUT); // set ESP32 pin to input mode pinMode(RELAY_PIN, OUTPUT); // set ESP32 pin to output mode currentTouchState = digitalRead(TOUCH_SENSOR_PIN); } void loop() { lastTouchState = currentTouchState; // save the last state currentTouchState = digitalRead(TOUCH_SENSOR_PIN); // read new state if (lastTouchState == LOW && currentTouchState == HIGH) { Serial.println("The sensor is touched"); // toggle state of relay relayState = !relayState; // control relay arccoding to the toggled state digitalWrite(RELAY_PIN, relayState); } }

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
  • Keep touching the touch sensor several seconds and then release it.
  • 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!

In the code, relayState = !relayState is equivalent to the following code:

if(relayState == LOW) relayState = HIGH; else relayState = LOW;

Video Tutorial

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