//reuk.co.uk November 2013

//for information and the schematic circuit diagram for this
//solar water heating pump controller design, visit:
//http://www.reuk.co.uk/wordpress/arduino-solar-water-heating-pump-controller-design-and-code/

const int PANELSENSOR = A2;
const int TANKSENSOR = A0;
const int RELAY = 12;

const int diffON = 6;
const int diffOFF = 3;

void setup(){
  Serial.begin(9600); 
 
  pinMode(PANELSENSOR, INPUT);
  pinMode(TANKSENSOR, INPUT);
  
  pinMode(RELAY, OUTPUT);
  digitalWrite(RELAY, LOW);
}

void loop(){
   float solarPanelTemperature = ((analogRead(PANELSENSOR) / 1024.0) * 5000)/10;
   float hotWaterTankTemperature = ((analogRead(TANKSENSOR) / 1024.0) * 5000)/10;       
   if(solarPanelTemperature > (hotWaterTankTemperature + diffON)){
     digitalWrite(RELAY, HIGH);
     do{
       delay(250);
       solarPanelTemperature = ((analogRead(PANELSENSOR) / 1024.0) * 5000)/10;
       hotWaterTankTemperature = ((analogRead(TANKSENSOR) / 1024.0) * 5000)/10;
     }while(solarPanelTemperature > (hotWaterTankTemperature + diffOFF));
     digitalWrite(RELAY, LOW);
   }
   delay(250);
}