mutiple_control.ino

#include "SevSeg.h"
SevSeg sevseg; //Initiate a seven segment controller object

// constants won't change. They're used here to set pin numbers:
const int SENSOR_PIN = A4; // the Arduino's input pin that connects to the sensor's SIGNAL pin 
const int LED_PIN = A5;
const int FAN_PIN = A0;
const int VOLTAGE_PIN = A2;
const int BUTTON_PIN = 1;
#define MQ2pin (A1)

// Variables will change:
int lastState = LOW;      // the previous state from the input pin
int currentState;         // the current reading from the input pin
int brightness = 0;
int fadeAmount = 25;

int btnCount = 0;
int btnCurrentState;
int btnLastState = LOW;
int btnLedState = LOW;

float sensorValue;  //variable to store sensor value
float voltageSensorVal;    
void setup() {
  // initialize serial communication at 9600 bits per second:
  Serial.begin(9600);
  // initialize the Arduino's pin as aninput
  pinMode(SENSOR_PIN, INPUT);
  pinMode(LED_PIN,OUTPUT);
  pinMode(FAN_PIN,OUTPUT);
  pinMode(BUTTON_PIN, INPUT);
  byte numDigits = 4;  
  byte digitPins[] = {2, 3, 4, 5};
  byte segmentPins[] = {6, 7, 8, 9, 10, 11, 12, 13};
  bool resistorsOnSegments = true;
  // variable above indicates that 4 resistors were placed on the digit pins.
  // set variable to 1 if you want to use 8 resistors on the segment pins.
  sevseg.begin(COMMON_ANODE, numDigits, digitPins, segmentPins, resistorsOnSegments);
  sevseg.setBrightness(90);
}

void loop() {

   btnCurrentState = digitalRead(BUTTON_PIN);

  if (btnLastState == HIGH && btnCurrentState == LOW) {   
    btnLedState = !btnLedState;
    if(btnCount < 2){
      btnCount++;
    }
    else{
      btnCount = 0;
    }
    
    Serial.println(btnCount);
  }
  btnLastState = btnCurrentState;  
  if(btnCount == 2){
      voltageSensorVal = analogRead(VOLTAGE_PIN); 
      float Vout = (voltageSensorVal/40.92);
      Serial.print("Voltage = ");             
      Serial.print(Vout);
      Serial.println("V");
      sevseg.setNumber(Vout*100 , 2);
      sevseg.refreshDisplay(); // Must run repeatedly
  }

  if(btnCount == 1){
    float gassensorValue = analogRead(MQ2pin); // read analog input pin 0
    Serial.print("Sensor Value: ");
    Serial.print(gassensorValue);
    if(gassensorValue > 300)
    {
      Serial.print(" | Smoke detected!");
    }
    sevseg.setNumber(gassensorValue*100 , 2);
    sevseg.refreshDisplay(); // Must run repeatedly
  }

  if(btnCount == 0){
    currentState = digitalRead(SENSOR_PIN);
    analogWrite(LED_PIN, brightness);
    sevseg.setNumber(brightness , 0);
    sevseg.refreshDisplay(); // Must run repeatedly
    analogWrite(FAN_PIN,brightness);

    if(lastState == LOW && currentState == HIGH){
      Serial.println("The sensor is touched");
      // change the brightness for next time through the loop:
      
      brightness = brightness + fadeAmount;
      // reverse the direction of the fading at the ends of the fade:
      if (brightness <= 0 || brightness >= 250) {
        fadeAmount = -fadeAmount;
      }

    }

    // save the the last state
    lastState = currentState;
  }


  
}