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Arduino - Touch Sensor
Touch sensor (also called touch button or touch switch) is widely used to control devices (e,g. touchable lamp). It has the same functionality as a button. It is used instead of the button on many new devices because it makes the product look neat.
In this tutorial, we will learn how to use the touch sensor with Arduino.
Hardware Required
Or you can buy the following sensor kit:
| 1 | × | DIYables Sensor Kit 30 types, 69 units |
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About Touch Sensor
Pinout
Touch sensor has 3 pins:
- GND pin: needs to be connected to GND (0V)
- VCC pin: needs to be connected to VCC (5V or 3.3v)
- SIGNAL pin: is an output pin: LOW when it is NOT touched, HIGH when it is touched. This pin needs to be connected to Arduino's input pin.
How It Works
- When the sensor is NOT touched, the sensor's SIGNAL pin is LOW
- When the sensor is touched, the sensor's SIGNAL pin is HIGH
Arduino - Touch Sensor
The touch sensor's SIGNAL pin is connected to an Arduino's input pin.
By reading the state of Arduino's pin (configured as an input pin), we can detect whether the touch sensor is touched or not.
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
How To Program For Touch Sensor
- Initializes the Arduino pin to the digital input mode by using pinMode() function. For example, pin 7
pinMode(7, INPUT_PULLUP);
- Reads the state of the Arduino pin by using digitalRead() function.
int inputState = digitalRead(7);
※ NOTE THAT:
There are two wide-used use cases:
- The first: If the input state is HIGH, do something. If the input state is LOW, do another thing in reverse.
- The second: If the input state is changed from LOW to HIGH (or HIGH to LOW), do something.
Depending on the application, we choose one of them. For example, in case of using a touch sensor to control an LED:
- If we want the LED to be ON when the sensor is touched and OFF when the sensor is NOT touched, we SHOULD use the first use case.
- If we want the LED to be toggle between ON and OFF each time we touch the sensor, we SHOULD use the second use case.
- How to detect the state change from LOW to HIGH
// constants won't change. They're used here to set pin numbers:
const int SENSOR_PIN = 7; // the Arduino's input pin that connects to the sensor's SIGNAL pin
// 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 Arduino'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;
}
Touch Sensor - Arduino Code
We will run four example codes:
- Reads the value from the touch sensor and print to the Serial Monitor.
- Controls LED according to the sensor's state.
- Detects the sensor is touched or released.
- Toggles LED when the sensor is touched (This is the most common-used).
Reads the value from the touch sensor and print to the Serial Monitor
/*
* Created by ArduinoGetStarted.com
*
* This example code is in the public domain
*
* Tutorial page: https://arduinogetstarted.com/tutorials/arduino-touch-sensor
*/
// constants won't change. They're used here to set pin numbers:
const int SENSOR_PIN = 7; // the Arduino's input pin that connects to the sensor's SIGNAL pin
void setup() {
// initialize serial communication at 9600 bits per second:
Serial.begin(9600);
// initialize the Arduino'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 Steps
- Copy the above code and open with Arduino IDE
- Click Upload button on Arduino IDE to upload code to Arduino
- Touch your finger to the sensor and release.
- See the result on Serial Monitor.
COM6
0
0
0
1
1
1
1
1
1
0
0
Autoscroll
Clear output
9600 baud
Newline
Controls LED according to the sensor's state
If the sensor is touched, turn LED on. If the sensor is not touched, turn LED off.
/*
* Created by ArduinoGetStarted.com
*
* This example code is in the public domain
*
* Tutorial page: https://arduinogetstarted.com/tutorials/arduino-touch-sensor
*/
// constants won't change. They're used here to set pin numbers:
const int SENSOR_PIN = 7; // the Arduino's input pin that connects to the sensor's SIGNAL pin
void setup() {
// initialize serial communication at 9600 bits per second:
Serial.begin(9600);
// initialize the Arduino's pin as aninput
pinMode(SENSOR_PIN, INPUT);
// initialize digital pin LED_BUILTIN as an output.
pinMode(LED_BUILTIN, OUTPUT);
}
void loop() {
// read the state of the the input pin:
int state = digitalRead(SENSOR_PIN);
// control LED according to the sensor's state
digitalWrite(LED_BUILTIN, state);
}
Quick Steps
- Copy the above code and open with Arduino IDE
- Click Upload button on Arduino IDE to upload code to Arduino
- Touch your finger to the sensor and keep touching.
- See LED state ⇒ LED should be on.
- Release your finger from the sensor.
- See LED state ⇒ LED should be off.
Detects the sensor is touched or released
// constants won't change. They're used here to set pin numbers:
const int SENSOR_PIN = 7; // the Arduino's input pin that connects to the sensor's SIGNAL pin
// 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 Arduino'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");
else if(lastState == HIGH && currentState == LOW)
Serial.println("The sensor is is released");
// save the the last state
lastState = currentState;
}
Quick Steps
- Copy the above code and open with Arduino IDE
- Click Upload button on Arduino IDE to upload code to Arduino
- Touch your finger to the sensor and keep touching.
- See the result on Serial Monitor.
COM6
The sensor is touched
Autoscroll
Clear output
9600 baud
Newline
- Release your finger from the sensor.
- See the result on Serial Monitor.
COM6
The sensor is touched
The sensor is is released
Autoscroll
Clear output
9600 baud
Newline
Toggles LED when the sensor is touched.
/*
* Created by ArduinoGetStarted.com
*
* This example code is in the public domain
*
* Tutorial page: https://arduinogetstarted.com/tutorials/arduino-touch-sensor
*/
// constants won't change. They're used here to set pin numbers:
const int SENSOR_PIN = 7; // the Arduino's input pin that connects to the sensor's SIGNAL pin
// Variables will change:
int lastState = LOW; // the previous state from the input pin
int currentState; // the current reading from the input pin
int ledState = LOW; // the current LED state
void setup() {
// initialize serial communication at 9600 bits per second:
Serial.begin(9600);
// initialize the Arduino's pin as aninput
pinMode(SENSOR_PIN, INPUT);
// initialize digital pin LED_BUILTIN as an output.
pinMode(LED_BUILTIN, OUTPUT);
}
void loop() {
// read the state of the the input pin:
currentState = digitalRead(SENSOR_PIN);
if(lastState == LOW && currentState == HIGH){
// toggle LED state
if(ledState == LOW)
ledState = HIGH;
else if(ledState == HIGH)
ledState = LOW;
// control LED
digitalWrite(LED_BUILTIN, ledState);
}
// save the the last state
lastState = currentState;
}
Quick Steps
- Copy the above code and open with Arduino IDE
- Click Upload button on Arduino IDE to upload code to Arduino
- Touch your finger to the sensor and release.
- See LED state ⇒ LED should be on.
- Touch your finger to the sensor and release.
- See LED state ⇒ LED should be off.
- Touch your finger to the sensor and release.
- See LED state ⇒ LED should be on.
Video Tutorial
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