Arduino powered Rice-cooker Sous Vide

SousVide-MK2.ino

#include <AutoPID.h>
#include <LiquidCrystal.h>
#include <max6675.h>

double currentTemp = 0.0;
double targetTemp = 60.0;
bool powerState = LOW;

//!MARK: LCD setup
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);

// define some values used by the panel and buttons
int lcd_key     = 0;
int adc_key_in  = 0;
#define btnRIGHT  0
#define btnUP     1
#define btnDOWN   2
#define btnLEFT   3
#define btnSELECT 4
#define btnNONE   5
int prev_btn = btnNONE;

//!MARK: Thermocouple setup
int thermo_gnd_pin = 13;
int thermo_vcc_pin = 12;
int thermo_so_pin  = 11;
int thermo_cs_pin  = 3;
int thermo_sck_pin = 2;
MAX6675 thermocouple(thermo_sck_pin, thermo_cs_pin, thermo_so_pin);

//!MARK: PID setup
unsigned long previousMillis = 0;
const long thermo_interval = 800;

int relay_pin = 19;
bool relay_state = LOW;

#define PULSEWIDTH 2500
double kP = 0.3;
double kI = 0.001;
double kD = kI / 2;
AutoPIDRelay myPID(&currentTemp, &targetTemp, &relay_state, PULSEWIDTH, kP, kI, kD);

//!MARK: LCD methods
int read_LCD_buttons() {
	adc_key_in = analogRead(0);      // read the value from the sensor
	// my buttons when read are centered at these valies: 0, 144, 329, 504, 741
	// we add approx 50 to those values and check to see if we are close
	if (adc_key_in > 1000) return btnNONE;
	// For V1.0 comment the other threshold and use the one below:
	if (adc_key_in < 50)   return btnRIGHT;
	if (adc_key_in < 195)  return btnUP;
	if (adc_key_in < 380)  return btnDOWN;
	if (adc_key_in < 555)  return btnLEFT;
	if (adc_key_in < 790)  return btnSELECT;

	return btnNONE;  // when all others fail, return this...
}

void updateScreen() {
	lcd.setCursor(0,0);            // move cursor to second line "1" and 9 spaces over
	lcd.print("Current: ");
	lcd.print(currentTemp);
	lcd.print(char(223));
	lcd.print("C ");

	lcd.setCursor(0,1);            // move to the begining of the second line
	if(powerState) {
		lcd.print("Target : ");
		lcd.print(targetTemp);
		lcd.print(char(223));
		lcd.print("C ");
	}
	else {
		lcd.print("  OFF  :(");
		lcd.print(targetTemp);
		lcd.print(")  ");
	}
	
	lcd_key = read_LCD_buttons();  // read the buttons

	if(lcd_key == btnNONE && prev_btn != btnNONE) {
			switch (prev_btn) {        // action based on released button
			case btnRIGHT:
				targetTemp += 5;
				break;
			case btnLEFT:
				targetTemp -= 5;
				break;
			case btnUP:
				targetTemp += 0.5;
				break;
			case btnDOWN:
				targetTemp -= 0.5;
				break;
			case btnSELECT:
				powerState = !powerState;
				break;
			case btnNONE:
				break;
		}
	}

	prev_btn = lcd_key;
}

//!MARK: Arduino
void setup() {
	Serial.begin(9600);

	myPID.setBangBang(4);
  myPID.setTimeStep(4000);
	
	lcd.begin(16, 2);
	lcd.setCursor(2,0);
	lcd.print("Sous Viduino");
	lcd.setCursor(11,1);
	lcd.print("MK2");

	pinMode(relay_pin, OUTPUT);
	digitalWrite(relay_pin, relay_state);

	pinMode(thermo_vcc_pin, OUTPUT);
	pinMode(thermo_gnd_pin, OUTPUT);
	digitalWrite(thermo_vcc_pin, HIGH);
	digitalWrite(thermo_gnd_pin, LOW);

	// wait for MAX chip to stabilize
	delay(PULSEWIDTH);
	lcd.clear();
}

void loop() {
	unsigned long currentMillis = millis();

	if (currentMillis - previousMillis >= thermo_interval) {
		previousMillis = currentMillis;
		currentTemp = thermocouple.readCelsius() - 3;
	}
	
	updateScreen();

	if(powerState) {
		myPID.run();
		digitalWrite(relay_pin, relay_state);
	}
	else {
    myPID.stop();
    relay_state = LOW;
    digitalWrite(relay_pin, relay_state);
	}
}