I am trying to implement PI control algorithm in c#. I found some help in internet and i understand the formula how to use. I have measured value(PV)= 20 °C  and set point (SP)= 80°C; I would like to update every 2 sec in time. once the measured value reach to setpoint the controller has to switch off like that.

I found this code [link to pid algorithm][1]

but what i need is how to calculate gain factors Kp and Ki gains as well as what about dt. I am neglecting Derivative. So please can anyone explain me how to calculate those gain factors. I am using shimaden SR90 digital controller(i bought this). I found some factors in the manual but i am not sure can i use those gain factors. 


  [1]: http://www.codeproject.com/Articles/36459/PID-process-control-a-Cruise-Control-example

> Edited for doubts.

I have tried your code like this, i am not sure this is the correct way or not.

    int temperature;
    //int setpoint; // i have commented these because we never used.
    //int status = 0;
	int pulses = 0;
    //int integral = 4;
    //int derivative = 5;
	int upperTemp = 1000; //100.0C
	int upperLimit = 100; //pulses per time frame // i can take 100 pulses per sec.


     runtime //make a timer that runs and updates temperature value...lets say every second
    {
      read temperature; //every second
      temperature *= 10; //multiply by 10 for decimal place, but still keeping in integer
      pulses = map(temperature, upperTemp, 0, 0, upperLimit);
      
      //take this value of pulses to update the timer interval
       I didn't understand the above line if i am right then here i need to call the       
       timer like 
       if(pulses> somevalue)
         call timer
       else
         no call
      }

    //borrowed from arduino
    long map(long x, long in_min, long in_max, long out_min, long out_max)
    {
      return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
    }


I have some question here 
1) This method seems to be different than previous because we never used gains or error in this method?
2) I understand that "upperTemp" is the setpoint value.

I have tried with simple example like this

     int temperature = 20;
     int pulses = 0;
     int upperTemp = 800; //80.0C
     int upperLimit = 100; //pulses per time frame // i can take 100 pulses per sec.

     read temperature; //every second which is 20 in this case
     temperature *= 10; //multiply by 10 for decimal place, 20*10 =200;
      pulses = map(temperature, upperTemp, 0, 0, upperLimit);// map(200,800,0,0,100)

     //then map function will return pulses = 75;
      
    //then here i don't understand that much but i am thinking like that

    if(pulses> 75)
      switch on;
    else 
       switch off; 
I am not sure that i am doing right! can you suggest me some more here.