Help with i2c LCD showing alternate messages

Projects Programming
1

Thanks to this community I have successfully combined 2 different sketches that will display on a 16x2 i2c LCD (In much less time than I imagined). So I am moving on to the next step in my project. Unfortunately I won't have the hardware available to test my sketch for a few weeks. I would like to have the messages for each sketch I combined to display for around 5 seconds then switch to the next one in a loop.
The code is pretty long so here is what I believe is the pertinent part. I will add the entire code at the end.

void setup() {
  pinMode(PWM_pin, OUTPUT);
  TCCR2B = TCCR2B & B11111000 | 0x03;  // pin 3 and 11 PWM frequency of 928.5 Hz
  Time = millis();

  Last_State = (PINB & B00000001);  //Detect first state of the encoder

  PCICR |= (1 << PCIE0);    //enable PCMSK0 scan
  PCMSK0 |= (1 << PCINT0);  //Set pin D8 trigger an interrupt on state change.
  PCMSK0 |= (1 << PCINT1);  //Set pin D9 trigger an interrupt on state change.
  PCMSK0 |= (1 << PCINT3);  //Set pin D11 trigger an interrupt on state change.

  pinMode(11, INPUT);
  pinMode(9, INPUT);
  pinMode(8, INPUT);

  lcd.init();
  lcd.backlight();

  //Begin paste from DHT22

  {
    lcd.begin(16, 2);  // Initializes the interface to the LCD screen, and specifies the dimensions (width and height) of the display
  }                    //End Paste from DHT22
}

void loop() {

  //Begin paste from DHT22

  {
    int readData = DHT.read22(dataPin);
    float t = DHT.temperature;  // May need to be in Variables.
    float h = DHT.humidity;     // May need to be in Variables.
    lcd.setCursor(0, 1);
    lcd.print("Humidity: ");
    lcd.print(h);
    lcd.print(" %");
    lcd.setCursor(1, 0);
    lcd.print(t);  // Prints the temperature value from the sensor
    lcd.print(" ");
    lcd.print((char)223);  //shows degrees character
    lcd.print("C");
    lcd.setCursor(1, 9);
    lcd.print((t * 9.0) / 5.0 + 32.0);  // print the temperature in Fahrenheit
    lcd.print(" ");
    lcd.print((char)223);  //shows degrees character
    lcd.print("F");
    delay(5000);
    lcd.clear();

// This was original sketck from DHT22
    //Print temperature value in Celcius and Fahrenheit every alternate cycle
    //  if (showcelciusorfarenheit) {
    //  lcd.print(t);  // Prints the temperature value from the sensor
    //  lcd.print(" ");
    //   lcd.print((char)223);  //shows degrees character
    //   lcd.print("C");
    //  showcelciusorfarenheit = false;
    //   } else {
    //    lcd.print((t * 9.0) / 5.0 + 32.0);  // print the temperature in Fahrenheit
    //    lcd.print(" ");
    //    lcd.print((char)223);  //shows degrees character
    //   lcd.print("F");
    //   showcelciusorfarenheit = true;


    //lcd.setCursor(0, 1);
    //lcd.print("Humi.: ");
    //lcd.print(h);
    //lcd.print(" %");
    //delay(5000);
  }
  //End paste from DHT22

  if (menu_activated == 0) {
    // First we read the real value of temperature
    temperature_read = readThermocouple();
    //Next we calculate the error between the setpoint and the real value
    PID_error = set_temperature - temperature_read + 3;
    //Calculate the P value
    PID_p = 0.01 * kp * PID_error;
    //Calculate the I value in a range on +-3
    PID_i = 0.01 * PID_i + (ki * PID_error);


    //For derivative we need real time to calculate speed change rate
    timePrev = Time;  // the previous time is stored before the actual time read
    Time = millis();  // actual time read
    elapsedTime = (Time - timePrev) / 1000;
    //Now we can calculate the D calue
    PID_d = 0.01 * kd * ((PID_error - previous_error) / elapsedTime);
    //Final total PID value is the sum of P + I + D
    PID_value = PID_p + PID_i + PID_d;

    //We define PWM range between 0 and 255
    if (PID_value < 0) { PID_value = 0; }
    if (PID_value > 255) { PID_value = 255; }
    //Now we can write the PWM signal to the mosfet on digital pin D3
    //Since we activate the MOSFET with a 0 to the base of the BJT, we write 255-PID value (inverted)
    analogWrite(PWM_pin, 255 - PID_value);
    previous_error = PID_error;  //Remember to store the previous error for next loop.

    delay(250);  //Refresh rate + delay of LCD print
    //lcd.clear();

    lcd.setCursor(0, 0);
    lcd.print("Filament Dryer v1");
    lcd.setCursor(0, 1);
    lcd.print("S:");
    lcd.setCursor(2, 1);
    lcd.print(set_temperature, 1);
    lcd.setCursor(9, 1);
    lcd.print("R:");
    lcd.setCursor(11, 1);
    lcd.print(temperature_read, 1);
  }  //end of menu 0 (PID control)




  //First page of menu (temp setpoint)
  if (menu_activated == 1) {
    analogWrite(PWM_pin, 255);
    if (set_temperature != last_set_temperature) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set  temperature");
      lcd.setCursor(0, 1);
      lcd.print(set_temperature);
    }
    last_set_temperature = set_temperature;


  }  //end of menu 1


  //Second page of menu (P set)
  if (menu_activated == 2) {

    if (kp != last_kp) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set   P  value  ");
      lcd.setCursor(0, 1);
      lcd.print(kp);
    }
    last_kp = kp;


  }  //end of menu 2


  //Third page of menu (I set)
  if (menu_activated == 3) {

    if (ki != last_ki) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set   I  value  ");
      lcd.setCursor(0, 1);
      lcd.print(ki);
    }
    last_ki = ki;


  }  //end of menu 3


  //Forth page of menu (D set)
  if (menu_activated == 4) {

    if (kd != last_kd) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set   D  value  ");
      lcd.setCursor(0, 1);
      lcd.print(kd);
    }
    last_kd = kd;
  }  //end of menu 4

}  //Loop end
    //   lcd.print((char)223);  //shows degrees character
    //   lcd.print("C");
    //  showcelciusorfarenheit = false;
    //   } else {
    //    lcd.print((t * 9.0) / 5.0 + 32.0);  // print the temperature in Fahrenheit
    //    lcd.print(" ");
    //    lcd.print((char)223);  //shows degrees character
    //   lcd.print("F");
    //   showcelciusorfarenheit = true;


    //lcd.setCursor(0, 1);
    //lcd.print("Humi.: ");
    //lcd.print(h);
    //lcd.print(" %");
    //delay(5000);
  }
  //End paste from DHT22

  if (menu_activated == 0) {
    // First we read the real value of temperature
    temperature_read = readThermocouple();
    //Next we calculate the error between the setpoint and the real value
    PID_error = set_temperature - temperature_read + 3;
    //Calculate the P value
    PID_p = 0.01 * kp * PID_error;
    //Calculate the I value in a range on +-3
    PID_i = 0.01 * PID_i + (ki * PID_error);


    //For derivative we need real time to calculate speed change rate
    timePrev = Time;  // the previous time is stored before the actual time read
    Time = millis();  // actual time read
    elapsedTime = (Time - timePrev) / 1000;
    //Now we can calculate the D calue
    PID_d = 0.01 * kd * ((PID_error - previous_error) / elapsedTime);
    //Final total PID value is the sum of P + I + D
    PID_value = PID_p + PID_i + PID_d;

    //We define PWM range between 0 and 255
    if (PID_value < 0) { PID_value = 0; }
    if (PID_value > 255) { PID_value = 255; }
    //Now we can write the PWM signal to the mosfet on digital pin D3
    //Since we activate the MOSFET with a 0 to the base of the BJT, we write 255-PID value (inverted)
    analogWrite(PWM_pin, 255 - PID_value);
    previous_error = PID_error;  //Remember to store the previous error for next loop.

    delay(250);  //Refresh rate + delay of LCD print
    //lcd.clear();

    lcd.setCursor(0, 0);
    lcd.print("Filament Dryer v1");
    lcd.setCursor(0, 1);
    lcd.print("S:");
    lcd.setCursor(2, 1);
    lcd.print(set_temperature, 1);
    lcd.setCursor(9, 1);
    lcd.print("R:");
    lcd.setCursor(11, 1);
    lcd.print(temperature_read, 1);
  }  //end of menu 0 (PID control)




  //First page of menu (temp setpoint)
  if (menu_activated == 1) {
    analogWrite(PWM_pin, 255);
    if (set_temperature != last_set_temperature) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set  temperature");
      lcd.setCursor(0, 1);
      lcd.print(set_temperature);
    }
    last_set_temperature = set_temperature;


  }  //end of menu 1


  //Second page of menu (P set)
  if (menu_activated == 2) {

    if (kp != last_kp) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set   P  value  ");
      lcd.setCursor(0, 1);
      lcd.print(kp);
    }
    last_kp = kp;


  }  //end of menu 2


  //Third page of menu (I set)
  if (menu_activated == 3) {

    if (ki != last_ki) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set   I  value  ");
      lcd.setCursor(0, 1);
      lcd.print(ki);
    }
    last_ki = ki;


  }  //end of menu 3


  //Forth page of menu (D set)
  if (menu_activated == 4) {

    if (kd != last_kd) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set   D  value  ");
      lcd.setCursor(0, 1);
      lcd.print(kd);
    }
    last_kd = kd;
  }  //end of menu 4

}  //Loop end

The goal is to have the alternating messages and keep the menus accessed through the button push on the rotary encoder. I'm still learning about "if/else" but am not sure if they will be affected.

Here is the full sketch so far. It compiles without error.

/*    Max6675 Module  ==>   Arduino
 *    CS              ==>     D10
 *    SO              ==>     D12
 *    SCK             ==>     D13
 *    Vcc             ==>     Vcc (5v)
 *    Gnd             ==>     Gnd      */
#include <SPI.h>

//LCD config
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x3f, 16, 2);  //sometimes the adress is not 0x3f. Change to 0x27 if it dosn't work.

/*    i2c LCD Module  ==>   Arduino
 *    SCL             ==>     A5
 *    SDA             ==>     A4
 *    Vcc             ==>     Vcc (5v)
 *    Gnd             ==>     Gnd      */

//I/O
int PWM_pin = 3;  //Pin for PWM signal to the MOSFET driver (the BJT npn with pullup)
int clk = 8;      //Pin 1 from rotary encoder
int data = 9;     //Pin 2 from rotary encoder


//Variables
float set_temperature = 0;  //Default temperature setpoint. Leave it 0 and control it with rotary encoder

float temperature_read = 0.0;
float PID_error = 0;
float previous_error = 0;
float elapsedTime, Time, timePrev;
float PID_value = 0;
int button_pressed = 0;
int menu_activated = 0;
float last_set_temperature = 0;

//Vraiables for rotary encoder state detection
int clk_State;
int Last_State;
bool dt_State;

//PID constants
//////////////////////////////////////////////////////////
int kp = 90;
int ki = 30;
int kd = 80;
//////////////////////////////////////////////////////////

int PID_p = 0;
int PID_i = 0;
int PID_d = 0;
float last_kp = 0;
float last_ki = 0;
float last_kd = 0;
int PID_values_fixed = 0;

//Pins for the SPI with MAX6675
#define MAX6675_CS 10
#define MAX6675_SO 12
#define MAX6675_SCK 13

//Begin paste fromDHT22
#include <dht.h>
#define dataPin 7

dht DHT;
bool showcelciusorfarenheit = false;

//End Paste from DHT22

void setup() {
  pinMode(PWM_pin, OUTPUT);
  TCCR2B = TCCR2B & B11111000 | 0x03;  // pin 3 and 11 PWM frequency of 928.5 Hz
  Time = millis();

  Last_State = (PINB & B00000001);  //Detect first state of the encoder

  PCICR |= (1 << PCIE0);    //enable PCMSK0 scan
  PCMSK0 |= (1 << PCINT0);  //Set pin D8 trigger an interrupt on state change.
  PCMSK0 |= (1 << PCINT1);  //Set pin D9 trigger an interrupt on state change.
  PCMSK0 |= (1 << PCINT3);  //Set pin D11 trigger an interrupt on state change.

  pinMode(11, INPUT);
  pinMode(9, INPUT);
  pinMode(8, INPUT);

  lcd.init();
  lcd.backlight();

  //Begin paste from DHT22

  {
    lcd.begin(16, 2);  // Initializes the interface to the LCD screen, and specifies the dimensions (width and height) of the display
  }                    //End Paste from DHT22
}

void loop() {

  //Begin paste from DHT22

  {
    int readData = DHT.read22(dataPin);
    float t = DHT.temperature;  // May need to be in Variables.
    float h = DHT.humidity;     // May need to be in Variables.
    lcd.setCursor(0, 1);
    lcd.print("Humidity: ");
    lcd.print(h);
    lcd.print(" %");
    lcd.setCursor(1, 0);
    lcd.print(t);  // Prints the temperature value from the sensor
    lcd.print(" ");
    lcd.print((char)223);  //shows degrees character
    lcd.print("C");
    lcd.setCursor(1, 9);
    lcd.print((t * 9.0) / 5.0 + 32.0);  // print the temperature in Fahrenheit
    lcd.print(" ");
    lcd.print((char)223);  //shows degrees character
    lcd.print("F");
    delay(5000);
    lcd.clear();
    //Print temperature value in Celcius and Fahrenheit every alternate cycle
    //  if (showcelciusorfarenheit) {
    //  lcd.print(t);  // Prints the temperature value from the sensor
    //  lcd.print(" ");
    //   lcd.print((char)223);  //shows degrees character
    //   lcd.print("C");
    //  showcelciusorfarenheit = false;
    //   } else {
    //    lcd.print((t * 9.0) / 5.0 + 32.0);  // print the temperature in Fahrenheit
    //    lcd.print(" ");
    //    lcd.print((char)223);  //shows degrees character
    //   lcd.print("F");
    //   showcelciusorfarenheit = true;


    //lcd.setCursor(0, 1);
    //lcd.print("Humi.: ");
    //lcd.print(h);
    //lcd.print(" %");
    //delay(5000);
  }
  //End paste from DHT22

  if (menu_activated == 0) {
    // First we read the real value of temperature
    temperature_read = readThermocouple();
    //Next we calculate the error between the setpoint and the real value
    PID_error = set_temperature - temperature_read + 3;
    //Calculate the P value
    PID_p = 0.01 * kp * PID_error;
    //Calculate the I value in a range on +-3
    PID_i = 0.01 * PID_i + (ki * PID_error);


    //For derivative we need real time to calculate speed change rate
    timePrev = Time;  // the previous time is stored before the actual time read
    Time = millis();  // actual time read
    elapsedTime = (Time - timePrev) / 1000;
    //Now we can calculate the D calue
    PID_d = 0.01 * kd * ((PID_error - previous_error) / elapsedTime);
    //Final total PID value is the sum of P + I + D
    PID_value = PID_p + PID_i + PID_d;

    //We define PWM range between 0 and 255
    if (PID_value < 0) { PID_value = 0; }
    if (PID_value > 255) { PID_value = 255; }
    //Now we can write the PWM signal to the mosfet on digital pin D3
    //Since we activate the MOSFET with a 0 to the base of the BJT, we write 255-PID value (inverted)
    analogWrite(PWM_pin, 255 - PID_value);
    previous_error = PID_error;  //Remember to store the previous error for next loop.

    delay(250);  //Refresh rate + delay of LCD print
    //lcd.clear();

    lcd.setCursor(0, 0);
    lcd.print("Filament Dryer v1");
    lcd.setCursor(0, 1);
    lcd.print("S:");
    lcd.setCursor(2, 1);
    lcd.print(set_temperature, 1);
    lcd.setCursor(9, 1);
    lcd.print("R:");
    lcd.setCursor(11, 1);
    lcd.print(temperature_read, 1);
  }  //end of menu 0 (PID control)




  //First page of menu (temp setpoint)
  if (menu_activated == 1) {
    analogWrite(PWM_pin, 255);
    if (set_temperature != last_set_temperature) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set  temperature");
      lcd.setCursor(0, 1);
      lcd.print(set_temperature);
    }
    last_set_temperature = set_temperature;


  }  //end of menu 1


  //Second page of menu (P set)
  if (menu_activated == 2) {

    if (kp != last_kp) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set   P  value  ");
      lcd.setCursor(0, 1);
      lcd.print(kp);
    }
    last_kp = kp;


  }  //end of menu 2


  //Third page of menu (I set)
  if (menu_activated == 3) {

    if (ki != last_ki) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set   I  value  ");
      lcd.setCursor(0, 1);
      lcd.print(ki);
    }
    last_ki = ki;


  }  //end of menu 3


  //Forth page of menu (D set)
  if (menu_activated == 4) {

    if (kd != last_kd) {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Set   D  value  ");
      lcd.setCursor(0, 1);
      lcd.print(kd);
    }
    last_kd = kd;
  }  //end of menu 4

}  //Loop end


//The function that reads the SPI data from MAX6675
double readThermocouple() {

  uint16_t v;
  pinMode(MAX6675_CS, OUTPUT);
  pinMode(MAX6675_SO, INPUT);
  pinMode(MAX6675_SCK, OUTPUT);

  digitalWrite(MAX6675_CS, LOW);
  delay(1);

  // Read in 16 bits,
  //  15    = 0 always
  //  14..2 = 0.25 degree counts MSB First
  //  2     = 1 if thermocouple is open circuit
  //  1..0  = uninteresting status

  v = shiftIn(MAX6675_SO, MAX6675_SCK, MSBFIRST);
  v <<= 8;
  v |= shiftIn(MAX6675_SO, MAX6675_SCK, MSBFIRST);

  digitalWrite(MAX6675_CS, HIGH);
  if (v & 0x4) {
    // Bit 2 indicates if the thermocouple is disconnected
    return NAN;
  }

  // The lower three bits (0,1,2) are discarded status bits
  v >>= 3;

  // The remaining bits are the number of 0.25 degree (C) counts
  return v * 0.25;
}


//The interruption vector for push button and rotary encoder
ISR(PCINT0_vect) {
  if (menu_activated == 1) {
    clk_State = (PINB & B00000001);  //pin 8 state? It is HIGH?
    dt_State = (PINB & B00000010);
    if (clk_State != Last_State) {
      // If the data state is different to the clock state, that means the encoder is rotating clockwise
      if (dt_State != clk_State) {
        set_temperature = set_temperature + 0.5;
      } else {
        set_temperature = set_temperature - 0.5;
      }
    }
    Last_State = clk_State;  // Updates the previous state of the clock with the current state
  }

  if (menu_activated == 2) {
    clk_State = (PINB & B00000001);  //pin 8 state?
    dt_State = (PINB & B00000010);
    if (clk_State != Last_State) {
      // If the data state is different to the clock state, that means the encoder is rotating clockwise
      if (dt_State != clk_State) {
        kp = kp + 1;
      } else {
        kp = kp - 1;
      }
    }
    Last_State = clk_State;  // Updates the previous state of the clock with the current state
  }


  if (menu_activated == 3) {
    clk_State = (PINB & B00000001);  //pin 8 state?
    dt_State = (PINB & B00000010);
    if (clk_State != Last_State) {
      // If the data state is different to the clock state, that means the encoder is rotating clockwise
      if (dt_State != clk_State) {
        ki = ki + 1;
      } else {
        ki = ki - 1;
      }
    }
    Last_State = clk_State;  // Updates the previous state of the clock with the current state
  }

  if (menu_activated == 4) {
    clk_State = (PINB & B00000001);  //pin 8 state?
    dt_State = (PINB & B00000010);
    if (clk_State != Last_State) {
      // If the data state is different to the clock state, that means the encoder is rotating clockwise
      if (dt_State != clk_State) {
        kd = kd + 1;
      } else {
        kd = kd - 1;
      }
    }
    Last_State = clk_State;  // Updates the previous state of the clock with the current state
  }



  //Push button was pressed!
  if (PINB & B00001000)  //Pin D11 is HIGH?
  {
    button_pressed = 1;
  }
  //We navigate through the 4 menus with each button pressed
  else if (button_pressed == 1) {

    if (menu_activated == 4) {
      menu_activated = 0;
      PID_values_fixed = 1;
      button_pressed = 0;
      delay(1000);
    }

    if (menu_activated == 3) {
      menu_activated = menu_activated + 1;
      button_pressed = 0;
      kd = kd + 1;
      delay(1000);
    } /*    Max6675 Module  ==>   Arduino
 *    CS              ==>     D10
 *    SO              ==>     D12
 *    SCK             ==>     D13
 *    Vcc             ==>     Vcc (5v)
 *    Gnd             ==>     Gnd      */
#include <SPI.h>

//LCD config
#include <Wire.h>
  }

  if (menu_activated == 2) {
    menu_activated = menu_activated + 1;
    button_pressed = 0;
    ki = ki + 1;
    delay(1000);
  }

  if (menu_activated == 1) {
    menu_activated = menu_activated + 1;
    button_pressed = 0;
    kp = kp + 1;
    delay(1000);
  }


  if (menu_activated == 0 && PID_values_fixed != 1) {
    menu_activated = menu_activated + 1;
    button_pressed = 0;
    set_temperature = set_temperature + 1;
    delay(1000);
  }
  PID_values_fixed = 0;
}

It will be for this schematic.

IMG_20230402_182611876_HDR~3
IMG_20230402_182611876_HDR~31920×1472 152 KB

2

Now is a great time to use: Wokwi - Online Arduino and ESP32 Simulator

3

Nice annotated schematic!

4

Thank you again. I literally just asked the community for this. I guess I'll leave it up in case I have problems. I don't always have internet out at sea.

5

You have an extremely long ISR.  Good practice notes the interrupt and does some minimal processing and/or sets a global variable, using the keyword volatile, which is then acted upon in the main code.  None of your variables use 'volatile'.

You also have a five second delay after writing to the LCD and several one second delays.  You do know nothing useful happens when in delay()?   No outputs updated, no inputs checked, etc.

You have #includes within the ISR.  Someone more knowledgeable might address whether or not this is a concern.

6

I appreciate your input on the ISR. Thankfully I'm not quite to that part of the sketch yet. I'm working my way down through it trying to be sure it is correct a little at a time. Currently just working on the display to LCD.

Crap... That 5 second delay was supposed to keep the 1st message up for 5 seconds then switch to the next message. The messages are data from the sensors. If nothing happens I need another way to alternate the messages. Thanks.

7

Interrupt Service Routine

That's the code within the brackets following ISR(PCINT0_vect).

Read about blink without delay in IDE -> file/examples/digital. Read about millis() timing - https://www.baldengineer.com/arduino-millis-examples.html

It is very important to nail down this concept of timing with millis.

You have at least five one-second delays in the ISR.

Rewriting to eliminate delay() and implement millis() timing will not be trivial.  Think carefully about what must happen.

8

Thank you. As I was editing my response I started thinking about millis(). You've pointed me in the right direction. Good thing I've got time on my hands while at work. Hopefully this will go as quickly as my last challenge.

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So far as I've been investigating, I've learned to use interrupts on my encoder I need to use the interrupt pins on my mini. Which happens to be 2 and 3. I have 3 assigned as output to my logic level MOSFET. Easy enough to re-assign to an unused digital pin such as 4. Then I would switch Clk and DT from 8 and 9 to 2 and 3. That should cover the schematic side of things. I've also read to use the interrupt in conjunction with millis(). I need to understand this more. I think originally the delay may have been to counter bounce but a full second seems like overkill. I may have gone off on a tangent and am learning the wrong homework though.

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Your project gives me a Adafruit Sous Vide feeling: https://learn.adafruit.com/sous-vide-powered-by-arduino-the-sous-viduino/sous-vide

They use a DS18B20 temperature sensor, and just the four buttons that come with that display module.
Perhaps you want too much. It is a simple project if you remove everything that is not necessary to dry filament.
Is your project already working and this is to make it more fancy ? Can you show the sketch of the working version as well ?

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Not working as of yet. I work offshore and find myself with an abundance of time. I imagined the setup and started looking at possibilities. This, once cleaned up and working properly, is the first iteration. I'll want to add more features later. For me, I learn through doing. I've read tons of Arduino books and done tons of simple projects. I've managed to cobble together a few more advanced ones that work well too. This is by far the most ambitious project to date. I'm learning about millis() as suggested by another member and it's starting to make sense. It's not my code so I can't take credit for it but ever time I read through it, I understand a little more. I was wondering if I could remove the Max6685 and just run the thermistor to the unused analog pins as well. That might simplify things a little.

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Well darn there's definitely more than one way to skin a cat.
Thank you for the link. If I had found this first I would have based my design off of it. And may still do so on another project I have in mind. Unfortunately I feel fully vested in the path I've taken and feel it will help me understand the options I have to the challenges I face. Once I get my 1st sketch working well, I may look into the auto tune part as an upgrade. I am wondering if the PID library would make things simpler and cleaner than what I have now. More research I guess. I'm not in a must have done by Thursday kinda situation.

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