ESP32 - Touch Sensor

This tutorial instructs you how to use ESP32 with the touch sensor (also known as touch switch, or touch button).

Hardware Used In This Tutorial

1×ESP-WROOM-32 Dev Module
1×Micro USB Cable
1×Touch Sensor
3×Jumper Wires
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Introduction to Touch Sensor

Touch Sensor Pinout

Touch sensor has 3 pins:

  • GND pin: connect this pin to GND (0V)
  • VCC pin: connect this pin to VCC (5V or 3.3v)
  • SIGNAL pin: is an output pin: LOW when NOT touched, HIGH when touched. This pin needs to be connected to ESP32's input pin.
  • Touch Sensor Pinout

How Touch Sensor Works

  • The state of the SIGNAL pin is LOW when the touch sensor is NOT touched
  • The state of the SIGNAL pin is HIGH when the touch sensor is touched

ESP32 - Touch Sensor

We can connect the touch sensor's SIGNAL pin to an ESP32's input pin and use the ESP32 code to read the state of touch sensor.

Wiring Diagram between Touch Sensor and ESP32

wiring diagram between esp32 touch sensor

This image is created using Fritzing. Click to enlarge image

How To Program Touch Sensor

  • Initializes the ESP32 pin to the digital input mode by using pinMode() function. For example, pin GIOP18
pinMode(18, INPUT_PULLUP);
  • Reads the state of the ESP32 pin by using digitalRead() function.
int inputState = digitalRead(18);

Touch Sensor - ESP32 Code

The below code reads the state of the touch sensor and print it to the Serial Monitor.

/* * 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 */ #define SENSOR_PIN 18 // ESP32 pin GIOP18 connected to the sensor's SIGNAL pin of touch sensor void setup() { // initialize serial communication at 9600 bits per second: Serial.begin(9600); // initialize the ESP32's pin as aninput pinMode(SENSOR_PIN, INPUT); } void loop() { // read the state of the the input pin: int state = digitalRead(SENSOR_PIN); // print state to Serial Monitor Serial.println(state); }

Quick Instructions

  • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
  • Copy the above code and paste it to Arduino IDE.
  • Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
  • Touch your finger to the sensor and release.
  • See the result on Serial Monitor. It looks like the below:
  • COM6
    Send
    0 0 0 1 1 1 1 1 1 0 0
    Autoscroll Show timestamp
    Clear output
    9600 baud  
    Newline  

How to detect the state change from LOW to HIGH

/* * 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 */ #define SENSOR_PIN 18 // ESP32 pin GIOP18 connected to the sensor's SIGNAL pin of touch sensor // Variables will change: int lastState = LOW; // the previous state from the input pin int currentState; // the current reading from the input pin void setup() { // initialize serial communication at 9600 bits per second: Serial.begin(9600); // initialize the ESP32's pin as aninput pinMode(SENSOR_PIN, INPUT); } void loop() { // read the state of the the input pin: currentState = digitalRead(SENSOR_PIN); if (lastState == LOW && currentState == HIGH) Serial.println("The sensor is touched"); // save the the last state lastState = currentState; }

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