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 > Added code according to answer. int temperature; int setpoint; int status = 0; int pulses = 0; int integral = 4; int derivative = 5; int upperTemp = 1000; //100.0C int upperLimit = 100; //pulses per time frame //WITH PULSING 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); //when temperature increases, //pulses decreases...vice versa //take this value of pulses to update the timer interval //timer's interval = pulses per second or minute } timer { if(Relay On) Relay Off; else Relay On; } //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; }