Arduino Kiln Control

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pardydon:
I would like to offer my input for controlling a kiln with an Arduino. I am using an Arduino Uno and a LCD panel 16 by 2 that uses the I2C interface. I also use the max 31855. These are all from Adafruit. I used a type K thermocouple from a pottery supply company. The thermocouple has to be of heavy gauge wire at least number 14.
On the input side I added a 10k pot and a push button switch. On the output side I directly wired the Arduino to 2 SSR relays.
There are postings on the Internet to do this with PID control. I found this to be very complex and not necessary for my application. I use it to fire pottery to cone 6. (2170 f)
My kiln is approx 13" dia and 12" deep inside . It is approx 3000 watts. The SSR relays are rated at 40 amp. I put them on large heat sink and run a computer fan to cool them.
The posting on this forum titled oven control is very similar to what I did. I will post my code when I figure out how to do that.

pardydon:
the code

/*
Kiln Controller
Mod Jan 7 2014 added hold time and slow cool Jan 13

*/
// include the library code:
#include "Adafruit_MAX31855.h"
#include <Wire.h>
#include <Adafruit_MCP23017.h>
#include <Adafruit_RGBLCDShield.h>

Adafruit_RGBLCDShield lcd = Adafruit_RGBLCDShield();

// constants won't change. They're used here to
// set pin numbers:
const int buttonPin = 2; // the number of the pushbutton pin
const int ledPin = 12; // the number of the LED pin
const int ledPinTwo = 11; //for 2nd element
const int sensorMin = 0; // sensor minimum
const int sensorMax = 1023; // sensor maximum

int thermoCLK = 5; //pins for MAX32855 chip
int thermoCS = 4;
int thermoDO = 3;
// Initialize the Thermocouple
Adafruit_MAX31855 thermocouple(thermoCLK, thermoCS, thermoDO);

// variables will change:
int buttonState = 0;// variable for reading pushbutton status
#define WHITE 0x7 // backlight color

void setup() {

Serial.begin(9600); // initialize serial communication:
lcd.begin(16, 2);
lcd.setBacklight(WHITE);
// initialize the LED pin as an output:
pinMode(ledPin, OUTPUT); // from button sketch
pinMode(ledPinTwo, OUTPUT); // 2nd element
// initialize the pushbutton pin as an input:
pinMode(buttonPin, INPUT);
pinMode(8,OUTPUT); //pin for speaker
// wait for MAX chip to stabilize
delay(5000);
}

void loop() {

// check if the pushbutton is pressed.
// if it is, the buttonState is HIGH:
while(buttonState = digitalRead(buttonPin),buttonState == LOW) {
delay(44); // stabilize button press

//This section of code is to display the choice as you adjust the pot

switch (knobRead()) {

case 0: // pot reading 0 to 255
displayMode();
lcd.setCursor(0, 1);
lcd.print("Full on 1 hr");
delay(1000);
break;

case 1: // higher reading
displayMode();
lcd.setCursor(0, 1);
lcd.print("Bisque");
delay(1000);
break;

case 2: // even higher
displayMode();
lcd.setCursor(0, 1);
lcd.print("Glaze");
delay(1000);
break;

case 3: // higher still
displayMode();
lcd.setCursor(0, 1);
lcd.print("Glaze Program 2");
delay(1000);
break;

case 4: // pot reading higher
displayMode();
lcd.setCursor(0, 1);
lcd.print("Show Temp only");
delay(1000);
break;

case 5: // pot reading higher
displayMode();
break;

case 6: // pot reading max
displayMode();
break;
};

};//end of while loop

//When button is pressed we jump to the selected mode***************

switch (knobRead()) {

case 0: // full on 1 hr
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("FULL ON 60 mins");

for (int i =0; i<= 3600; i++){
heatHigh();
showTemperatureAndTime();
delay (1000);
}
break;

case 1: // bisque

lcd.clear(); //print bisque
lcd.setCursor(0, 0);
lcd.print("BISQUE Warm Up");

//warm for 2 hours at 200F

while (elapsedTime() < 120){
showTemperatureAndTime();
while (tempVal() < 200){

showTemperatureAndTime();
heatLow(); //power to element
delay (200);

}//end of while loop for temp
}//end of while loop for time

// second stage of fire
do{

lcd.clear(); //print bisque 2nd stage
lcd.setCursor(0, 0);
lcd.print("2nd stage BISQUE");

showTemperatureAndTime();
heatMedium();

}
while (tempVal() < 600);

// Third stage of fire

do{

lcd.clear(); //print bisque 3rd stage
lcd.setCursor(0, 0);
lcd.print("3rd stage BISQUE");

showTemperatureAndTime();
heatHigh();
delay (2000);
}
while (tempVal() < 1888); //cone 05 iss 1888 F

heatOff();
slowCool();
//clear display and print DONE mssg.
lcd.clear();
lcd.setCursor(2, 0);
lcd.print("BISQUE DONE ");
endSignal();

break;
//*******************************************************************
case 2: // glaze
lcd.clear(); //print glaze
lcd.setCursor(0, 0);
lcd.print(" GLAZE Warming");

// warm for 2 hours at 200F

while (elapsedTime() < 120){
showTemperatureAndTime();
while (tempVal() < 200){

showTemperatureAndTime();
heatLow(); //power to element
delay (200);

}//end of while loop for temp
}//end of while loop for time

// second stage of fire
lcd.clear(); //print 2nd stage mssg
lcd.setCursor(0, 0);
lcd.print("Glaze 2nd stage");

do{
heatMedium();
showTemperatureAndTime();

}
while (tempVal() < 600);

// Third stage of fire
lcd.clear(); //print 3rd stage mssg
lcd.setCursor(0, 0);
lcd.print("Glaze 3rd stage");

do{
heatHigh();
showTemperatureAndTime();
}
while (tempVal() < 2170); //cone 6 is 2170 F

// Fourth Stage Hold 15 mins

holdFifteen();

// Fifth stage slow cool with element on medium

slowCool();

heatOff(); // end of firing cycle

glazeDoneMessage(); //clear display and print DONE

break;
//*********************************************************************
case 3: //Glaze program 2 Jan 24

lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Glaze program 2");
delay (3000);
//Step 1 heat 2 hr @ 200f
while ( elapsedTime() < 120){
showTemperatureAndTime();
heatKiln(25,200);
}

// Step 2
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("GLAZE 2nd stage");

while (tempVal() < 600){
showTemperatureAndTime();
heatKiln(50,600);
}

// Step 3
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("GLAZE 3rd stage");

while (tempVal() < 1100){
showTemperatureAndTime();
heatKiln(75,1100);
}

// Step 4 cone 6 is 2170F
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("GLAZE 4th stage");

while (tempVal() < 2170){
showTemperatureAndTime();
heatHigh();
}
heatOff();

// Stage 5 Hold 15 mins

holdFifteen();

// stage 6 slow cool with element on medium

slowCool();

heatOff(); // end of firing cycle

glazeDoneMessage(); //clear display and print DONE

break;

case 4:
lcd.clear();
showTemperatureAndTime();
delay(10000);
break;

case 5:
break;

case 6:
break;

}//end of switch case

} //end of main program loop

//**************FUNCTIONS*****************************************

// func to pass range value.
int knobRead (){
// read the sensor:a 10k potentiometer
int sensorReading = analogRead(A0);//input from potentiometer(0-1023)
// map the sensor reading to a range of four options:
int range = map(sensorReading, sensorMin, sensorMax, 0, 6);

return range;
}

//function to display temp
int tempVal(){
int f = thermocouple.readFarenheit();
if (isnan(f))
{
lcd.print("T/C Problem");
}
else
{
return f;
delay(200);
}
}//end of func

//function to put text on LCD
void printKilnMode(){
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Kiln Mode ");
lcd.setCursor(11, 0);

}//end of func

void displayMode(){
printKilnMode();
lcd.print(knobRead());
delay(1000);
}//end of function

//function to get ET
//returns no of mins.since reset
int elapsedTime(){
unsigned long time = millis();//gives a minute counter
int elapsedTimeCalc = (time/60000);// since reset
return elapsedTimeCalc;
}//end of func.

//output to element 25%
void heatLow(){
digitalWrite(ledPin,HIGH);
delay(2000);//on time 2 sec
digitalWrite(ledPin,LOW);
delay(6000);//off time 6 sec
}//end of function

//output to element 50%
void heatMedium(){
digitalWrite(ledPin,HIGH);
delay(4000);//on time 4 sec
digitalWrite(ledPin,LOW);
delay(4000);//off time 4 sec
}//end of function

//output to element 100%
void heatHigh(){
digitalWrite(ledPin,HIGH);
digitalWrite(ledPinTwo,HIGH);
}//end of function

//output to element 0%
void heatOff(){
digitalWrite(ledPin,LOW);
digitalWrite(ledPinTwo,LOW);
}//end of function

void showTemperatureAndTime(){
lcd.setCursor(0, 1);//show temp
lcd.print("F=");
lcd.print(tempVal());
lcd.setCursor(8, 1); //print elapsed time
lcd.print("ET "); //since reset
lcd.setCursor(11, 1);
lcd.print(elapsedTime());
}//end of function

void slowCool(){
int slowCoolTime = elapsedTime();
int y = slowCoolTime +60;//add 1 hour

while (elapsedTime() < y){
lcd.clear(); //print mssg
lcd.setCursor(0, 0);
lcd.print("slow cool");

showTemperatureAndTime();
heatMedium();
}// end of while loop for slow cool

}

void holdFifteen(){

int holdTime = elapsedTime();
int x = holdTime +15; //add 15 to present time

while (elapsedTime() < x){
lcd.clear(); //print hold mssg
lcd.setCursor(0, 0);
lcd.print("Glaze Hold 15m");

showTemperatureAndTime();

while (tempVal() < 2170){
heatHigh();
showTemperatureAndTime();
delay(500);
}// end of while loop for temp hold

heatOff();

}// end of loop for hold time

}

void glazeDoneMessage(){
lcd.clear();
lcd.setCursor(6, 0);
lcd.print("GLAZE DONE ");

for(int x = 0; x < 6000; x++){
tone(8,500);// uses pin 8 to a speaker and resistor?
delay(500);// sounds tone for 100 minutes
noTone(8);
lcd.setCursor(0, 1);
lcd.print(tempVal());
lcd.print("F time ");//print time since stop
lcd.print(x/60);

}//end of for loop

}

void heatKiln (float percentHeat, int targetTemp){
//int f = thermocouple.readFarenheit();
if ( tempVal() < targetTemp){

digitalWrite(ledPin,HIGH);
delay((percentHeat/100) * 8000);//on time
digitalWrite(ledPin,LOW);
delay(((100-percentHeat)/100)*8000);//off time
}
}

void endSignal(){
for(int x = 0; x < 6000; x++){
tone(8,500);// uses pin 8 to a 120 ohm resistor and speaker
delay(500);// sounds tone for 100 minutes
noTone(8);
lcd.setCursor(0, 1);
lcd.print(tempVal());
lcd.print("F time ");//print time since stop
lcd.print(x/60);
lcd.print(" ");

}//end of for loop 100 mins
}

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