reflow/reflowctl/reflowctl.ino

#define START_STATE 0
#define PREHEAT_STATE 1
#define RAMP_UP_STATE 2
#define TAL_FIRST_STATE 3
#define PEAK_STATE 4
#define TAL_SECOND_STATE 5
#define RAMP_DOWN_STATE 6
#define END_STATE 7
#define ERROR_STATE 8

// error conditions
#define E_RAMPUP 1 // oven heats up too fast
#define E_RAMPDOWN_TOO_FAST 2 // oven cools down too fast
#define E_RAMPDOWN_TOO_SLOW 3 // oven cools down too slow
#define E_TIME_MAX 4 // reflow process does take too long
#define E_PEAK_TOO_LONG 5 // package was roasted

unsigned int time = 0; // profile seconds
unsigned int temperatur = 25; // actual oven temp
unsigned int last_temperatur = 25;


// profile stuff
unsigned int Ts_max = 200; // °C
unsigned int Ts_min = 150; // °C
unsigned int Tp = 260; // 245-260°C
unsigned int rampup_rate = 50; // 3°C/s
unsigned int preheat_duration = 100; // 60-180s
unsigned int Tl = 217; // 217°C
unsigned int Tl_duration = 100; // 60-150s
unsigned int peak_duration = 30; // 20-40s
unsigned int rampdown_max = 6; // 6°C/s max
unsigned int rampdown_min = 2; // 2°C/s max
unsigned int time_max = 480; // 8*60s max

unsigned int Ts_min_time = 0;
unsigned int Ts_max_time = 0;
unsigned int Tl_time_start = 0;
unsigned int Tl_time_end = 0;
unsigned int Tp_time_start = 0;
unsigned int Tp_time_end = 0;
unsigned int error_condition = 0;

boolean is_oven_heating = false;

byte state = START_STATE;

int analogPin = 2;

int hysteresis = 0;

int set_min = 0;
int set_max = 0;

void setup() {
  Serial.begin(9600);
  get_temp();
  last_temperatur = temperatur;
  control_oven(Tp, Tp);
}


void set_temp(int min, int max) {
  set_min = min;
  set_max = max;
}

void control_oven() {
  if (temperatur < set_min) {
    is_oven_heating = true;
    Serial.println("Oven turned on");
  }
  else if (temperatur < set_max) {
    is_oven_heating = false;
    Serial.println("Oven turned off");
  }
}

void get_temp() {
  // simulating an +1K/s rampup oven
  last_temperatur = temperatur;
  temperatur = int(float(analogRead(analogPin)) * 0.2929);
}

void check_rampup_rate() {
  if (temperatur - last_temperatur > rampup_rate) {
    error_condition = E_RAMPUP;
    control_oven(false);
  }
  else
    control_oven(true);
}

boolean check_rampdown_rate() {
  unsigned int dt = temperatur - last_temperatur;
  if (dt > rampdown_max) {
    error_condition = E_RAMPDOWN_TOO_FAST;
    return false;
  }

  if (dt < rampdown_min) {
    error_condition = E_RAMPDOWN_TOO_SLOW;
    return false;
  }
  return true;
}


boolean check_max_duration() {
  if (time > time_max) {
    error_condition = E_TIME_MAX;
    return false;
  }
}

boolean check_Tl_duration() {
  if (time > time_max) {
    error_condition = E_TIME_MAX;
    return false;
  }
}


void handle_start_state() {
  if (temperatur > Ts_min) {
    Serial.println("Changing state to PREHEAT_STATE");
    Ts_min_time = time;
    state++;
  }
}



void handle_peak_state() {
  Serial.println("PEAK_STATE");
  if (temperatur > Tp)
    control_oven(false);
  else
    control_oven(true);

  if (time - Tp_time_start > peak_duration) {
    Serial.println("Changed state to TAL_SECOND_STATE");
    Tp_time_end = time;
    state++;
  }
}


void loop() {
  time = millis() / 1000;
  get_temp();
  Serial.print(time);
  Serial.print(" ");
  Serial.print(temperatur);
  Serial.print(" ");
  Serial.print(last_temperatur);
  Serial.print(" ");
  Serial.println(state);

  
  switch (state) {
      case START_STATE:
        Serial.println("START_STATE");
        // going from room temp to preheat, nothing to check here
        handle_start_state();
        break;
      case PREHEAT_STATE:
        Serial.println("PREHEAT_STATE");
        check_rampup_rate();
        if (temperatur > Ts_max) {
          Serial.println("Changed state to RAMP_UP_STATE");
          Ts_max_time = time;
          state++;
        }
        break;
      case RAMP_UP_STATE:
        Serial.println("RAMP_UP_STATE");
        check_rampup_rate();
        if (temperatur > Tl) {
          Serial.println("Changed state to TAL_FIRST_STATE");
          Tl_time_start = time;
          state++;
        }
        break;
      case TAL_FIRST_STATE:
        Serial.println("TAL_FIRST_STATE");
        check_rampup_rate();
        if (temperatur > Tp - 5) {
          Serial.println("Changed state to PEAK_STATE");
          Tp_time_start = time;
          state++;
        }
        break;
      case PEAK_STATE:
        handle_peak_state();
        break;
      case TAL_SECOND_STATE:
        Serial.println("TAL_SECOND_STATE");
        if (temperatur < Tl) {
          Serial.println("Changed state to RAMP_DOWN_STATE");
          Tl_time_end = time;
          state++;
        }
        break;
      case RAMP_DOWN_STATE:
        Serial.println("RAMP_DOWN_STATE");
        if (temperatur < Ts_min) {
          Serial.println("Changed state to END_STATE");
          state++;
        }
        break;
      case END_STATE:
        Serial.println("END_STATE");
      default:
        break;
  }

  control_oven();
  delay(1000);

  return;

error:
  state = END_STATE;
  Serial.print("Error: ");
  Serial.println(error_condition);
}