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Lesson 40: Touch toggle light

This project is a simple implementation of a traffic light control system utilizing a touch sensor and a traffic light LED module. Activating the touch sensor initiates a sequence where LEDs illuminate in the following order: Red -> Yellow -> Green.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Universal Maker Sensor Kit	94	Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction	Purchase Link
ESP32 & Development Board (ESP32 Board)	BUY
Touch Sensor Module	-
Traffic Light Module	-
Breadboard	BUY

Wiring

Code

Code Analysis

The operation of this project is straightforward: a touch detection on the sensor triggers the illumination of the next LED in the sequence (Red -> Yellow -> Green), controlled by the currentLED variable.

1. Define pins and initial values

   // Define pins for touch sensor and LEDs
   const int touchSensorPin = 14;  // touch sensor pin
   const int rledPin = 27;         // red LED pin
   const int yledPin = 26;         // yellow LED pin
   const int gledPin = 25;         // green LED pin
   
   int lastTouchState;     // the previous state of touch sensor
   int currentTouchState;  // the current state of touch sensor
   int currentLED = 0;     // current LED 0->Red, 1->Yellow, 2->Green
   

   These lines establish the pin connections for the Arduino board components and initialize the touch sensor and LED states.

2. setup() function

   void setup() {
     Serial.begin(9600);              // initialize serial
     pinMode(touchSensorPin, INPUT);  // configure touch sensor pin as input
   
     // set LED pins as outputs
     pinMode(rledPin, OUTPUT);
     pinMode(yledPin, OUTPUT);
     pinMode(gledPin, OUTPUT);
   
     currentTouchState = digitalRead(touchSensorPin);
   }
   

   This function configures the initial setup for the Arduino, defining input and output modes and starting serial communication for debugging.

3. loop() function

   void loop() {
     lastTouchState = currentTouchState;               // save the last state
     currentTouchState = digitalRead(touchSensorPin);  // read new state
   
     // check if the touch sensor was just touched
     if (lastTouchState == LOW && currentTouchState == HIGH) {
       Serial.println("The sensor is touched");
   
       turnAllLEDsOff();  // Turn off all LEDs
   
       // switch on the next LED in sequence
       switch (currentLED) {
         case 0:
           digitalWrite(rledPin, HIGH);
           currentLED = 1;
           break;
         case 1:
           digitalWrite(yledPin, HIGH);
           currentLED = 2;
           break;
         case 2:
           digitalWrite(gledPin, HIGH);
           currentLED = 0;
           break;
       }
     }
   }
   

   The loop continuously monitors the touch sensor, cycling through the LEDs when a touch is detected, ensuring only one LED is on at any given time.

4. Turn off LEDs function

   // function to turn off all LEDs
   void turnAllLEDsOff() {
     digitalWrite(rledPin, LOW);
     digitalWrite(yledPin, LOW);
     digitalWrite(gledPin, LOW);
   }
   

   This auxiliary function turns off all LEDs, aiding in the cycling process.