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Former Member over 13 years ago

Hello im new to arduinos and i need some help with this code that im using for a toaster oven hack im doing here is the code
/*******************************************************************************
* Title: Reflow Oven Controller
* Version: 1.10
* Date: 22-12-2011
* Company: Rocket Scream Electronics
* Website: www.rocketscream.com
*
* Brief
* =====
* This is an example firmware for our Arduino compatible reflow oven controller.
* The reflow curve used in this firmware is meant for lead-free profile
* (it's even easier for leaded process!). Please check our wiki
* (www.rocketscream.com/wiki) for more information on using this piece of code
* together with the reflow oven controller.
*
* Temperature (Degree Celcius)                 Magic Happens Here!
* 245-|                                               x x
*     |                                            x        x
*     |                                         x              x
*     |                                      x                    x
* 200-|                                   x                          x
*     |                              x    |                          |   x
*     |                         x         |                          |       x
*     |                    x              |                          |
* 150-|               x                   |                          |
*     |             x |                   |                          |
*     |           x   |                   |                          |
*     |         x     |                   |                          |
*     |       x       |                   |                          |
*     |     x         |                   |                          |
*     |   x           |                   |                          |
* 30 -| x             |                   |                          |
*     |< 60 - 90 s >|<    90 - 120 s   >|<       90 - 120 s       >|
*     | Preheat Stage |   Soaking Stage   |       Reflow Stage       | Cool
* 0 |_ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
*                                                                Time (Seconds)
*
* This firmware owed very much on the works of other talented individuals as
* follows:
* ==========================================
* Brett Beauregard (www.brettbeauregard.com)
* ==========================================
* Author of Arduino PID library. On top of providing industry standard PID
* implementation, he gave a lot of help in making this reflow oven controller
* possible using his awesome library.
*
* ==========================================
* Limor Fried of Adafruit (www.adafruit.com)
* ==========================================
* Author of Arduino MAX6675 library. Adafruit has been the source of tonnes of
* tutorials, examples, and libraries for everyone to learn.
*
* Disclaimer
* ==========
* Dealing with high voltage is a very dangerous act! Please make sure you know
* what you are dealing with and have proper knowledge before hand. Your use of
* any information or materials on this reflow oven controller is entirely at
* your own risk, for which we shall not be liable.
*
* Licences
* ========
* This reflow oven controller hardware and firmware are released under the
* Creative Commons Share Alike v3.0 license
* http://creativecommons.org/licenses/by-sa/3.0/
* You are free to take this piece of code, use it and modify it.
* All we ask is attribution including the supporting libraries used in this
* firmware.
*
* Revision Description
* ======== ===========
* 1.10      Arduino IDE 1.0 compatible.
* 1.00      Initial public release.
*******************************************************************************/
// ***** INCLUDES *****
#include <LiquidCrystal.h>
#include <max6675.h>
#include <PID_v1.h>

// ***** TYPE DEFINITIONS *****
typedef enum REFLOW_STATE{
REFLOW_STATE_IDLE,
REFLOW_STATE_PREHEAT,
REFLOW_STATE_SOAK,
REFLOW_STATE_REFLOW,
REFLOW_STATE_COOL,
REFLOW_STATE_COMPLETE,
REFLOW_STATE_ERROR
} reflowState_t;

typedef enum REFLOW_STATUS{
REFLOW_STATUS_OFF,
REFLOW_STATUS_ON
} reflowStatus_t;

typedef enum DEBOUNCE_STATE{
DEBOUNCE_STATE_IDLE,
DEBOUNCE_STATE_CHECK,
DEBOUNCE_STATE_RELEASE
} debounceState_t;

// ***** CONSTANTS *****
#define TEMPERATURE_ROOM 50
#define TEMPERATURE_SOAK_MIN 150
#define TEMPERATURE_SOAK_MAX 200
#define TEMPERATURE_REFLOW_MAX 250
#define TEMPERATURE_COOL_MIN 100
#define SENSOR_SAMPLING_TIME 1000
#define SOAK_TEMPERATURE_STEP 5
#define SOAK_MICRO_PERIOD 9000
#define DEBOUNCE_PERIOD_MIN 50
#define THERMOCOUPLE_DISCONNECTED 10000

// ***** PID PARAMETERS *****
// ***** PRE-HEAT STAGE *****
#define PID_KP_PREHEAT 300
#define PID_KI_PREHEAT 0.05
#define PID_KD_PREHEAT 400
// ***** SOAKING STAGE *****
#define PID_KP_SOAK 300
#define PID_KI_SOAK 0.05
#define PID_KD_SOAK 250
// ***** REFLOW STAGE *****
#define PID_KP_REFLOW 300
#define PID_KI_REFLOW 0.05
#define PID_KD_REFLOW 350
#define PID_SAMPLE_TIME 1000

// ***** LCD MESSAGES *****
const char* lcdMessagesReflowStatus[] = {
"Ready",
"Pre-heat",
"Soak",
"Reflow",
"Cool",
"Complete",
"Error"
};

// ***** DEGREE SYMBOL FOR LCD *****
unsigned char degree[8] = {140,146,146,140,128,128,128,128};

// ***** PIN ASSIGNMENT *****
int ssr = 5;
int thermocoupleSO = A5;
int thermocoupleCS = A4;
int thermocoupleCLK = A3;
int lcdRs = 7;
int lcdE = 8;
int lcdD4 = 9;
int lcdD5 = 10;
int lcdD6 = 11;
int lcdD7 = 12;
int ledRed = A1;
int ledGreen = A0;
int buzzer = 6;
int button1 = 2;
int button2 = 3;

// ***** PID CONTROL VARIABLES *****
double setpoint;
double input;
double output;
double kp = PID_KP_PREHEAT;
double ki = PID_KI_PREHEAT;
double kd = PID_KD_PREHEAT;
int windowSize;
unsigned long windowStartTime;
unsigned long nextCheck;
unsigned long nextRead;
unsigned long timerSoak;
unsigned long buzzerPeriod;
// Reflow oven controller state machine state variable
reflowState_t reflowState;
// Reflow oven controller status
reflowStatus_t reflowStatus;
// Button debounce state machine state variable
debounceState_t debounceState;
// Button debounce timer
long lastDebounceTime;
// Button press status
boolean buttonPressStatus;
// Seconds timer
int timerSeconds;

// Specify PID control interface
PID reflowOvenPID(&input, &output, &setpoint, kp, ki, kd, DIRECT);
// Specify LCD interface
LiquidCrystal lcd(lcdRs, lcdE, lcdD4, lcdD5, lcdD6, lcdD7);
// Specify MAX6675 thermocouple interface
MAX6675 thermocouple(thermocoupleCLK, thermocoupleCS, thermocoupleSO);

void setup()
{
// SSR pin initialization to ensure reflow oven is off
digitalWrite(ssr, LOW);
pinMode(ssr, OUTPUT);

// Buzzer pin initialization to ensure annoying buzzer is off
digitalWrite(buzzer, LOW);
pinMode(buzzer, OUTPUT);

// LED pins initialization and turn on upon start-up (active low)
digitalWrite(ledRed, LOW);
digitalWrite(ledGreen, LOW);
pinMode(ledRed, OUTPUT);
pinMode(ledGreen, OUTPUT);
          // Push button pins initialization
pinMode(button1, INPUT);
pinMode(button2, INPUT);

// Start-up splash
digitalWrite(buzzer, HIGH);
lcd.begin(8, 2);
lcd.createChar(0, degree);
lcd.clear();
lcd.print("Reflow");
lcd.setCursor(0, 1);
lcd.print("Oven 1.1");
digitalWrite(buzzer, LOW);
delay(2500);
lcd.clear();

// Serial communication at 57600 bps
Serial.begin(57600);

// Turn off LED (active low)
digitalWrite(ledRed, HIGH);
digitalWrite(ledGreen, HIGH);

// Set window size
windowSize = 2000;
// Initialize time keeping variable
nextCheck = millis();
// Initialize thermocouple reading varible
nextRead = millis();
}

void loop()
{
// Current time
unsigned long now;

// Time to read thermocouple?
if (millis() > nextRead)
{
    // Read thermocouple next sampling period
    nextRead += SENSOR_SAMPLING_TIME;
    // Read current temperature
    input = thermocouple.readCelsius();

    // If thermocouple is not connected
    if (input == THERMOCOUPLE_DISCONNECTED)
    {
      // Illegal operation without thermocouple
      reflowState = REFLOW_STATE_ERROR;
      reflowStatus = REFLOW_STATUS_OFF;
    }
}

if (millis() > nextCheck)
{
    // Check input in the next seconds
    nextCheck += 1000;
    // If reflow process is on going
    if (reflowStatus == REFLOW_STATUS_ON)
    {
      // Toggle red LED as system heart beat
      digitalWrite(ledRed, !(digitalRead(ledRed)));
      // Increase seconds timer for reflow curve analysis
      timerSeconds++;
      // Send temperature and time stamp to serial
      Serial.print(timerSeconds);
      Serial.print(" ");
      Serial.print(setpoint);
      Serial.print(" ");
      Serial.print(input);
      Serial.print(" ");
      Serial.println(output);
    }
    else
    {
      // Turn off red LED
      digitalWrite(ledRed, HIGH);
    }

    // Clear LCD
    lcd.clear();
    // Print current system state
    lcd.print(lcdMessagesReflowStatus[reflowState]);
    // Move the cursor to the 2 line
    lcd.setCursor(0, 1);

    // If currently in error state
    if (reflowState == REFLOW_STATE_ERROR)
    {
      // No thermocouple wire connected
      lcd.print("No TC!");
    }
    else
    {
      // Print current temperature
      lcd.print(input);
              #if ARDUINO >= 100
                lcd.write((uint8_t)0);
              #else
                                        // Print degree Celsius symbol
                                        lcd.print(0, BYTE);
              #endif
      lcd.print("C ");
    }
}

    // Reflow oven controller state machine
    switch (reflowState)
    {
        case REFLOW_STATE_IDLE:
            // If button is pressed to start reflow process
            if (buttonPressStatus)
            {
                // Ensure current temperature is comparable to room temperature
                                                                                // TO DO: To add indication that temperature is still high for
                                                                                // reflow process to start
                if (input <= TEMPERATURE_ROOM)
                {
                    // Send header for CSV file
                    Serial.println("Time Setpoint Input Output");
                    // Intialize seconds timer for serial debug information
                    timerSeconds = 0;
                    // Initialize PID control window starting time
                    windowStartTime = millis();
                    // Ramp up to minimum soaking temperature
                    setpoint = TEMPERATURE_SOAK_MIN;
                    // Tell the PID to range between 0 and the full window size
                    reflowOvenPID.SetOutputLimits(0, windowSize);
                    reflowOvenPID.SetSampleTime(PID_SAMPLE_TIME);
                    // Turn the PID on
                    reflowOvenPID.SetMode(AUTOMATIC);
                    // Proceed to preheat stage
                    reflowState = REFLOW_STATE_PREHEAT;
                }
            }
            break;

        case REFLOW_STATE_PREHEAT:
            reflowStatus = REFLOW_STATUS_ON;
            // If minimum soak temperature is achieve
            if (input >= TEMPERATURE_SOAK_MIN)
            {
                // Chop soaking period into smaller sub-period
                timerSoak = millis() + SOAK_MICRO_PERIOD;
                // Set less agressive PID parameters for soaking ramp
                reflowOvenPID.SetTunings(PID_KP_SOAK, PID_KI_SOAK, PID_KD_SOAK);
                // Ramp up to first section of soaking temperature
                setpoint = TEMPERATURE_SOAK_MIN + SOAK_TEMPERATURE_STEP;
                // Proceed to soaking state
                reflowState = REFLOW_STATE_SOAK;
            }
            break;

        case REFLOW_STATE_SOAK:
            // If micro soak temperature is achieved
            if (millis() > timerSoak)
            {
                timerSoak = millis() + SOAK_MICRO_PERIOD;
                // Increment micro setpoint
                setpoint += SOAK_TEMPERATURE_STEP;
                if (setpoint > TEMPERATURE_SOAK_MAX)
                {
                    // Set agressive PID parameters for reflow ramp
                    reflowOvenPID.SetTunings(PID_KP_REFLOW, PID_KI_REFLOW, PID_KD_REFLOW);
                    // Ramp up to first section of soaking temperature
                    setpoint = TEMPERATURE_REFLOW_MAX;
                    // Proceed to reflowing state
                    reflowState = REFLOW_STATE_REFLOW;
                }
            }
            break;

        case REFLOW_STATE_REFLOW:
            // We need to avoid hovering at peak temperature for too long
            // Crude method that works like a charm and safe for the components
            if (input >= (TEMPERATURE_REFLOW_MAX - 5))
            {
                // Set PID parameters for cooling ramp
                reflowOvenPID.SetTunings(PID_KP_REFLOW, PID_KI_REFLOW, PID_KD_REFLOW);
                // Ramp down to minimum cooling temperature
                setpoint = TEMPERATURE_COOL_MIN;
                // Proceed to cooling state
                reflowState = REFLOW_STATE_COOL;
            }
            break;

        case REFLOW_STATE_COOL:
            // If minimum cool temperature is achieve
            if (input <= TEMPERATURE_COOL_MIN)
            {
                // Retrieve current time for buzzer usage
                buzzerPeriod = millis() + 1000;
                // Turn on buzzer and green LED to indicate completion
                digitalWrite(ledGreen, LOW);
                digitalWrite(buzzer, HIGH);
                // Turn off reflow process
                reflowStatus = REFLOW_STATUS_OFF;
                // Proceed to reflow Completion state
                reflowState = REFLOW_STATE_COMPLETE;
            }
            break;

        case REFLOW_STATE_COMPLETE:
            if (millis() > buzzerPeriod)
            {
                // Turn off buzzer and green LED
                digitalWrite(buzzer, LOW);
                digitalWrite(ledGreen, HIGH);
                // Reflow process ended
                reflowState = REFLOW_STATE_IDLE;
            }
            break;

        case REFLOW_STATE_ERROR:
            // If thermocouple is still not connected
            if (input == THERMOCOUPLE_DISCONNECTED)
            {
                // Wait until thermocouple wire is connected
                reflowState = REFLOW_STATE_ERROR;
            }
            else
            {
                // Clear to perform reflow process
                reflowState = REFLOW_STATE_IDLE;
            }
            break;
    }

    // If button is pressed
    if (buttonPressStatus == true)
    {
        // If currently reflow process is on going
        if (reflowStatus == REFLOW_STATUS_ON)
        {
            // Button press is for cancelling
            // Turn off reflow process
            reflowStatus = REFLOW_STATUS_OFF;
            // Reinitialize state machine
            reflowState = REFLOW_STATE_IDLE;
        }
    }

// Simple button debounce state machine (for button #1 only)
          // TO DO: To be replaced with interrupt version in next revision
    switch (debounceState)
    {
        case DEBOUNCE_STATE_IDLE:
            // No valid button press
            buttonPressStatus = false;
            // If button #1 is pressed
            if (digitalRead(button1) == LOW)
            {
                // Intialize debounce counter
                lastDebounceTime = millis();
                // Proceed to check validity of button press
                debounceState = DEBOUNCE_STATE_CHECK;
            }
            break;

        case DEBOUNCE_STATE_CHECK:
            // If button #1 is still pressed
            if (digitalRead(button1) == LOW)
            {
                // If minimum debounce period is completed
                if ((millis() - lastDebounceTime) > DEBOUNCE_PERIOD_MIN)
                {
                    // Proceed to wait for button release
                    debounceState = DEBOUNCE_STATE_RELEASE;
                }
            }
            // False trigger
            else
            {
                // Reinitialize button debounce state machine
                debounceState = DEBOUNCE_STATE_IDLE;
            }
            break;

        case DEBOUNCE_STATE_RELEASE:
            if (digitalRead(button1) == HIGH)
            {
                // Valid button press
                buttonPressStatus = true;
                // Reinitialize button debounce state machine
                debounceState = DEBOUNCE_STATE_IDLE;
            }
            break;
    }

    // PID computation and SSR control
    if (reflowStatus == REFLOW_STATUS_ON)
    {
        //unsigned long now;
        now = millis();

        reflowOvenPID.Compute();

        if((now - windowStartTime) > windowSize)
        {
            // Time to shift the Relay Window
            windowStartTime += windowSize;
        }
        if(output > (now - windowStartTime)) digitalWrite(ssr, HIGH);
        else digitalWrite(ssr, LOW);
    }
    // Reflow oven process is off, ensure oven is off
    else
    {
        digitalWrite(ssr, LOW);
    }
}
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Former Member over 13 years ago

Hello im new to arduinos and i need some help with this code that im using for a toaster oven hack im doing here is the code
/*******************************************************************************
* Title: Reflow Oven Controller
* Version: 1.10
* Date: 22-12-2011
* Company: Rocket Scream Electronics
* Website: www.rocketscream.com
*
* Brief
* =====
* This is an example firmware for our Arduino compatible reflow oven controller.
* The reflow curve used in this firmware is meant for lead-free profile
* (it's even easier for leaded process!). Please check our wiki
* (www.rocketscream.com/wiki) for more information on using this piece of code
* together with the reflow oven controller.
*
* Temperature (Degree Celcius)                 Magic Happens Here!
* 245-|                                               x x
*     |                                            x        x
*     |                                         x              x
*     |                                      x                    x
* 200-|                                   x                          x
*     |                              x    |                          |   x
*     |                         x         |                          |       x
*     |                    x              |                          |
* 150-|               x                   |                          |
*     |             x |                   |                          |
*     |           x   |                   |                          |
*     |         x     |                   |                          |
*     |       x       |                   |                          |
*     |     x         |                   |                          |
*     |   x           |                   |                          |
* 30 -| x             |                   |                          |
*     |< 60 - 90 s >|<    90 - 120 s   >|<       90 - 120 s       >|
*     | Preheat Stage |   Soaking Stage   |       Reflow Stage       | Cool
* 0 |_ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
*                                                                Time (Seconds)
*
* This firmware owed very much on the works of other talented individuals as
* follows:
* ==========================================
* Brett Beauregard (www.brettbeauregard.com)
* ==========================================
* Author of Arduino PID library. On top of providing industry standard PID
* implementation, he gave a lot of help in making this reflow oven controller
* possible using his awesome library.
*
* ==========================================
* Limor Fried of Adafruit (www.adafruit.com)
* ==========================================
* Author of Arduino MAX6675 library. Adafruit has been the source of tonnes of
* tutorials, examples, and libraries for everyone to learn.
*
* Disclaimer
* ==========
* Dealing with high voltage is a very dangerous act! Please make sure you know
* what you are dealing with and have proper knowledge before hand. Your use of
* any information or materials on this reflow oven controller is entirely at
* your own risk, for which we shall not be liable.
*
* Licences
* ========
* This reflow oven controller hardware and firmware are released under the
* Creative Commons Share Alike v3.0 license
* http://creativecommons.org/licenses/by-sa/3.0/
* You are free to take this piece of code, use it and modify it.
* All we ask is attribution including the supporting libraries used in this
* firmware.
*
* Revision Description
* ======== ===========
* 1.10      Arduino IDE 1.0 compatible.
* 1.00      Initial public release.
*******************************************************************************/
// ***** INCLUDES *****
#include <LiquidCrystal.h>
#include <max6675.h>
#include <PID_v1.h>

// ***** TYPE DEFINITIONS *****
typedef enum REFLOW_STATE{
REFLOW_STATE_IDLE,
REFLOW_STATE_PREHEAT,
REFLOW_STATE_SOAK,
REFLOW_STATE_REFLOW,
REFLOW_STATE_COOL,
REFLOW_STATE_COMPLETE,
REFLOW_STATE_ERROR
} reflowState_t;

typedef enum REFLOW_STATUS{
REFLOW_STATUS_OFF,
REFLOW_STATUS_ON
} reflowStatus_t;

typedef enum DEBOUNCE_STATE{
DEBOUNCE_STATE_IDLE,
DEBOUNCE_STATE_CHECK,
DEBOUNCE_STATE_RELEASE
} debounceState_t;

// ***** CONSTANTS *****
#define TEMPERATURE_ROOM 50
#define TEMPERATURE_SOAK_MIN 150
#define TEMPERATURE_SOAK_MAX 200
#define TEMPERATURE_REFLOW_MAX 250
#define TEMPERATURE_COOL_MIN 100
#define SENSOR_SAMPLING_TIME 1000
#define SOAK_TEMPERATURE_STEP 5
#define SOAK_MICRO_PERIOD 9000
#define DEBOUNCE_PERIOD_MIN 50
#define THERMOCOUPLE_DISCONNECTED 10000

// ***** PID PARAMETERS *****
// ***** PRE-HEAT STAGE *****
#define PID_KP_PREHEAT 300
#define PID_KI_PREHEAT 0.05
#define PID_KD_PREHEAT 400
// ***** SOAKING STAGE *****
#define PID_KP_SOAK 300
#define PID_KI_SOAK 0.05
#define PID_KD_SOAK 250
// ***** REFLOW STAGE *****
#define PID_KP_REFLOW 300
#define PID_KI_REFLOW 0.05
#define PID_KD_REFLOW 350
#define PID_SAMPLE_TIME 1000

// ***** LCD MESSAGES *****
const char* lcdMessagesReflowStatus[] = {
"Ready",
"Pre-heat",
"Soak",
"Reflow",
"Cool",
"Complete",
"Error"
};

// ***** DEGREE SYMBOL FOR LCD *****
unsigned char degree[8] = {140,146,146,140,128,128,128,128};

// ***** PIN ASSIGNMENT *****
int ssr = 5;
int thermocoupleSO = A5;
int thermocoupleCS = A4;
int thermocoupleCLK = A3;
int lcdRs = 7;
int lcdE = 8;
int lcdD4 = 9;
int lcdD5 = 10;
int lcdD6 = 11;
int lcdD7 = 12;
int ledRed = A1;
int ledGreen = A0;
int buzzer = 6;
int button1 = 2;
int button2 = 3;

// ***** PID CONTROL VARIABLES *****
double setpoint;
double input;
double output;
double kp = PID_KP_PREHEAT;
double ki = PID_KI_PREHEAT;
double kd = PID_KD_PREHEAT;
int windowSize;
unsigned long windowStartTime;
unsigned long nextCheck;
unsigned long nextRead;
unsigned long timerSoak;
unsigned long buzzerPeriod;
// Reflow oven controller state machine state variable
reflowState_t reflowState;
// Reflow oven controller status
reflowStatus_t reflowStatus;
// Button debounce state machine state variable
debounceState_t debounceState;
// Button debounce timer
long lastDebounceTime;
// Button press status
boolean buttonPressStatus;
// Seconds timer
int timerSeconds;

// Specify PID control interface
PID reflowOvenPID(&input, &output, &setpoint, kp, ki, kd, DIRECT);
// Specify LCD interface
LiquidCrystal lcd(lcdRs, lcdE, lcdD4, lcdD5, lcdD6, lcdD7);
// Specify MAX6675 thermocouple interface
MAX6675 thermocouple(thermocoupleCLK, thermocoupleCS, thermocoupleSO);

void setup()
{
// SSR pin initialization to ensure reflow oven is off
digitalWrite(ssr, LOW);
pinMode(ssr, OUTPUT);

// Buzzer pin initialization to ensure annoying buzzer is off
digitalWrite(buzzer, LOW);
pinMode(buzzer, OUTPUT);

// LED pins initialization and turn on upon start-up (active low)
digitalWrite(ledRed, LOW);
digitalWrite(ledGreen, LOW);
pinMode(ledRed, OUTPUT);
pinMode(ledGreen, OUTPUT);
          // Push button pins initialization
pinMode(button1, INPUT);
pinMode(button2, INPUT);

// Start-up splash
digitalWrite(buzzer, HIGH);
lcd.begin(8, 2);
lcd.createChar(0, degree);
lcd.clear();
lcd.print("Reflow");
lcd.setCursor(0, 1);
lcd.print("Oven 1.1");
digitalWrite(buzzer, LOW);
delay(2500);
lcd.clear();

// Serial communication at 57600 bps
Serial.begin(57600);

// Turn off LED (active low)
digitalWrite(ledRed, HIGH);
digitalWrite(ledGreen, HIGH);

// Set window size
windowSize = 2000;
// Initialize time keeping variable
nextCheck = millis();
// Initialize thermocouple reading varible
nextRead = millis();
}

void loop()
{
// Current time
unsigned long now;

// Time to read thermocouple?
if (millis() > nextRead)
{
    // Read thermocouple next sampling period
    nextRead += SENSOR_SAMPLING_TIME;
    // Read current temperature
    input = thermocouple.readCelsius();

    // If thermocouple is not connected
    if (input == THERMOCOUPLE_DISCONNECTED)
    {
      // Illegal operation without thermocouple
      reflowState = REFLOW_STATE_ERROR;
      reflowStatus = REFLOW_STATUS_OFF;
    }
}

if (millis() > nextCheck)
{
    // Check input in the next seconds
    nextCheck += 1000;
    // If reflow process is on going
    if (reflowStatus == REFLOW_STATUS_ON)
    {
      // Toggle red LED as system heart beat
      digitalWrite(ledRed, !(digitalRead(ledRed)));
      // Increase seconds timer for reflow curve analysis
      timerSeconds++;
      // Send temperature and time stamp to serial
      Serial.print(timerSeconds);
      Serial.print(" ");
      Serial.print(setpoint);
      Serial.print(" ");
      Serial.print(input);
      Serial.print(" ");
      Serial.println(output);
    }
    else
    {
      // Turn off red LED
      digitalWrite(ledRed, HIGH);
    }

    // Clear LCD
    lcd.clear();
    // Print current system state
    lcd.print(lcdMessagesReflowStatus[reflowState]);
    // Move the cursor to the 2 line
    lcd.setCursor(0, 1);

    // If currently in error state
    if (reflowState == REFLOW_STATE_ERROR)
    {
      // No thermocouple wire connected
      lcd.print("No TC!");
    }
    else
    {
      // Print current temperature
      lcd.print(input);
              #if ARDUINO >= 100
                lcd.write((uint8_t)0);
              #else
                                        // Print degree Celsius symbol
                                        lcd.print(0, BYTE);
              #endif
      lcd.print("C ");
    }
}

    // Reflow oven controller state machine
    switch (reflowState)
    {
        case REFLOW_STATE_IDLE:
            // If button is pressed to start reflow process
            if (buttonPressStatus)
            {
                // Ensure current temperature is comparable to room temperature
                                                                                // TO DO: To add indication that temperature is still high for
                                                                                // reflow process to start
                if (input <= TEMPERATURE_ROOM)
                {
                    // Send header for CSV file
                    Serial.println("Time Setpoint Input Output");
                    // Intialize seconds timer for serial debug information
                    timerSeconds = 0;
                    // Initialize PID control window starting time
                    windowStartTime = millis();
                    // Ramp up to minimum soaking temperature
                    setpoint = TEMPERATURE_SOAK_MIN;
                    // Tell the PID to range between 0 and the full window size
                    reflowOvenPID.SetOutputLimits(0, windowSize);
                    reflowOvenPID.SetSampleTime(PID_SAMPLE_TIME);
                    // Turn the PID on
                    reflowOvenPID.SetMode(AUTOMATIC);
                    // Proceed to preheat stage
                    reflowState = REFLOW_STATE_PREHEAT;
                }
            }
            break;

        case REFLOW_STATE_PREHEAT:
            reflowStatus = REFLOW_STATUS_ON;
            // If minimum soak temperature is achieve
            if (input >= TEMPERATURE_SOAK_MIN)
            {
                // Chop soaking period into smaller sub-period
                timerSoak = millis() + SOAK_MICRO_PERIOD;
                // Set less agressive PID parameters for soaking ramp
                reflowOvenPID.SetTunings(PID_KP_SOAK, PID_KI_SOAK, PID_KD_SOAK);
                // Ramp up to first section of soaking temperature
                setpoint = TEMPERATURE_SOAK_MIN + SOAK_TEMPERATURE_STEP;
                // Proceed to soaking state
                reflowState = REFLOW_STATE_SOAK;
            }
            break;

        case REFLOW_STATE_SOAK:
            // If micro soak temperature is achieved
            if (millis() > timerSoak)
            {
                timerSoak = millis() + SOAK_MICRO_PERIOD;
                // Increment micro setpoint
                setpoint += SOAK_TEMPERATURE_STEP;
                if (setpoint > TEMPERATURE_SOAK_MAX)
                {
                    // Set agressive PID parameters for reflow ramp
                    reflowOvenPID.SetTunings(PID_KP_REFLOW, PID_KI_REFLOW, PID_KD_REFLOW);
                    // Ramp up to first section of soaking temperature
                    setpoint = TEMPERATURE_REFLOW_MAX;
                    // Proceed to reflowing state
                    reflowState = REFLOW_STATE_REFLOW;
                }
            }
            break;

        case REFLOW_STATE_REFLOW:
            // We need to avoid hovering at peak temperature for too long
            // Crude method that works like a charm and safe for the components
            if (input >= (TEMPERATURE_REFLOW_MAX - 5))
            {
                // Set PID parameters for cooling ramp
                reflowOvenPID.SetTunings(PID_KP_REFLOW, PID_KI_REFLOW, PID_KD_REFLOW);
                // Ramp down to minimum cooling temperature
                setpoint = TEMPERATURE_COOL_MIN;
                // Proceed to cooling state
                reflowState = REFLOW_STATE_COOL;
            }
            break;

        case REFLOW_STATE_COOL:
            // If minimum cool temperature is achieve
            if (input <= TEMPERATURE_COOL_MIN)
            {
                // Retrieve current time for buzzer usage
                buzzerPeriod = millis() + 1000;
                // Turn on buzzer and green LED to indicate completion
                digitalWrite(ledGreen, LOW);
                digitalWrite(buzzer, HIGH);
                // Turn off reflow process
                reflowStatus = REFLOW_STATUS_OFF;
                // Proceed to reflow Completion state
                reflowState = REFLOW_STATE_COMPLETE;
            }
            break;

        case REFLOW_STATE_COMPLETE:
            if (millis() > buzzerPeriod)
            {
                // Turn off buzzer and green LED
                digitalWrite(buzzer, LOW);
                digitalWrite(ledGreen, HIGH);
                // Reflow process ended
                reflowState = REFLOW_STATE_IDLE;
            }
            break;

        case REFLOW_STATE_ERROR:
            // If thermocouple is still not connected
            if (input == THERMOCOUPLE_DISCONNECTED)
            {
                // Wait until thermocouple wire is connected
                reflowState = REFLOW_STATE_ERROR;
            }
            else
            {
                // Clear to perform reflow process
                reflowState = REFLOW_STATE_IDLE;
            }
            break;
    }

    // If button is pressed
    if (buttonPressStatus == true)
    {
        // If currently reflow process is on going
        if (reflowStatus == REFLOW_STATUS_ON)
        {
            // Button press is for cancelling
            // Turn off reflow process
            reflowStatus = REFLOW_STATUS_OFF;
            // Reinitialize state machine
            reflowState = REFLOW_STATE_IDLE;
        }
    }

// Simple button debounce state machine (for button #1 only)
          // TO DO: To be replaced with interrupt version in next revision
    switch (debounceState)
    {
        case DEBOUNCE_STATE_IDLE:
            // No valid button press
            buttonPressStatus = false;
            // If button #1 is pressed
            if (digitalRead(button1) == LOW)
            {
                // Intialize debounce counter
                lastDebounceTime = millis();
                // Proceed to check validity of button press
                debounceState = DEBOUNCE_STATE_CHECK;
            }
            break;

        case DEBOUNCE_STATE_CHECK:
            // If button #1 is still pressed
            if (digitalRead(button1) == LOW)
            {
                // If minimum debounce period is completed
                if ((millis() - lastDebounceTime) > DEBOUNCE_PERIOD_MIN)
                {
                    // Proceed to wait for button release
                    debounceState = DEBOUNCE_STATE_RELEASE;
                }
            }
            // False trigger
            else
            {
                // Reinitialize button debounce state machine
                debounceState = DEBOUNCE_STATE_IDLE;
            }
            break;

        case DEBOUNCE_STATE_RELEASE:
            if (digitalRead(button1) == HIGH)
            {
                // Valid button press
                buttonPressStatus = true;
                // Reinitialize button debounce state machine
                debounceState = DEBOUNCE_STATE_IDLE;
            }
            break;
    }

    // PID computation and SSR control
    if (reflowStatus == REFLOW_STATUS_ON)
    {
        //unsigned long now;
        now = millis();

        reflowOvenPID.Compute();

        if((now - windowStartTime) > windowSize)
        {
            // Time to shift the Relay Window
            windowStartTime += windowSize;
        }
        if(output > (now - windowStartTime)) digitalWrite(ssr, HIGH);
        else digitalWrite(ssr, LOW);
    }
    // Reflow oven process is off, ensure oven is off
    else
    {
        digitalWrite(ssr, LOW);
    }
}
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