Code complete Version 1.00

After 7 alpha and 23 beta revisions, here's version 1.0 of the code. It's amazingly simple.

/*
Kegerator Thermostat Version 1.0

The circuit:
* LCD RS pin to digital pin 12
* LCD Enable pin to digital pin 11
* LCD D4 pin to digital pin 5
* LCD D5 pin to digital pin 4
* LCD D6 pin to digital pin 3
* LCD D7 pin to digital pin 2
* LCD pin 1 to ground
* LCD pin 2 to +5v
* LCD pin 3 to 4.7K ohm res to ground

* LM-34 Vout pin to Analog 0

* Button up to digital pin 7
* Button down to digital pin 8

* Relay on digital pin 13

*/

// include the library code:
#include

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

// set pin numbers:
const int relay = 13; // the number of the relay pin
const int buttonUpPin = 8; // the number of the Temp Up pin
const int buttonDnPin = 7; // the number of the Temp Down pin
const int tempPin = 0; // analog temp sensor pin
// set wait values
const int maxOffWait = 50000; // How many ms to wait to turn off
const int maxOnWait = 50000; // How many ms to wait to turn on


// variables:
int setTemp = 50; // variable storing the Set temp
int currTemp = 0; // variable storing the actual, current temp
int tempTemp = 0; // temporary temp
int buttonUpState = 0; // variable for reading the pushbutton status
int buttonDnState = 0; // variable for reading the pushbutton status
int tempIn = 0; // get temperature variable
int flagOff = 0; // flag for off delay loop
int flagOn = 0; // flag for on delay loop


void setup() {
// set up the LCD's number of rows and columns:
lcd.begin(16, 2);
// initialize the pushbutton pins as input:
pinMode(relay, OUTPUT);
digitalWrite(relay, HIGH);
pinMode(buttonUpPin, INPUT);
pinMode(buttonDnPin, INPUT);
lcd.setCursor(0, 0);
lcd.print(" Key Largo");
lcd.setCursor(0, 1);
lcd.print(" Brewery");
delay(500);
lcd.setCursor(0, 1);
lcd.print(" ");
}

void loop() {
// Print header line of output
lcd.setCursor(0, 0);
lcd.print(" Current | Set ");

// set the cursor to column 0, line 1
// (note: line 1 is the second row, since counting begins with 0):
lcd.setCursor(3, 1);
lcd.print(currTemp);
lcd.print("F ");
lcd.setCursor(9, 1);
lcd.print("|");
lcd.setCursor(11, 1);

// Check buttons for set temp
buttonUpState = digitalRead(buttonUpPin);
if (buttonUpState == HIGH) {
// add 1 to setTemp
setTemp++;
delay(250);
}
buttonDnState = digitalRead(buttonDnPin);
if (buttonDnState == HIGH) {
// subtr 1 from setTemp
setTemp--;
delay(250);
}
lcd.print(setTemp);
lcd.print("F ");

//Get the temp
tempIn = analogRead(tempPin)/8.0;
currTemp = (tempIn * 9)/ 5 + 32; // converts to fahrenheit
tempTemp = setTemp-1;

//Relay switch off logic (Anti-thrashing)
if ((tempTemp > currTemp)&&(flagOff == 0)) {
flagOff = 1;
}
if ((flagOff != 0)&&(flagOff <= maxOffWait)){
++flagOff;
}
if (flagOff >= maxOffWait){
// turn on relay
lcd.setCursor(15, 1);
lcd.print("-");
digitalWrite(relay, LOW);
flagOff = 0;
}

//Relay switch on logic (Anti-thrashing)
if ((setTemp < flagon ="="">
flagOn = 1;
}
if ((flagOn != 0)&&(flagOn <= maxOnWait)){
++flagOn;
}
if (flagOn >= maxOnWait){
// turn off relay
lcd.setCursor(15, 1);
lcd.print("+");
digitalWrite(relay, HIGH);
flagOn = 0;
}
}