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Lesson 42: 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
Arduino UNO R3 or R4	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

   const int touchSensorPin = 2;  // Touch sensor pin
   const int rledPin = 7;         // Red LED pin
   const int yledPin = 8;         // Yellow LED pin
   const int gledPin = 9;         // Green LED pin
   int lastTouchState;            // Previous touch sensor state
   int currentTouchState;         // Current touch sensor state
   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 communication
     pinMode(touchSensorPin, INPUT);  // Set touch sensor pin as input
     // Configure LED pins as outputs
     pinMode(rledPin, OUTPUT);
     pinMode(yledPin, OUTPUT);
     pinMode(gledPin, OUTPUT);
     currentTouchState = digitalRead(touchSensorPin); // Read initial touch state
   }
   

   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;                        // Store the last state
     currentTouchState = digitalRead(touchSensorPin);           // Read new touch state
     if (lastTouchState == LOW && currentTouchState == HIGH) {  // Detect touch
       Serial.println("Sensor touched");
       turnAllLEDsOff();  // Turn off all LEDs
       // Activate 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

   void turnAllLEDsOff() {
     // Set all LED pins to LOW, turning them off
     digitalWrite(rledPin, LOW);
     digitalWrite(yledPin, LOW);
     digitalWrite(gledPin, LOW);
   }
   

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