Originally Posted by helibrewer
I think he means he would like to implement PID functionality through software (Arduino style) rather by using a physical PID controller (MyPin or Auberins style).
Yup. Got that. My point is that however you go about it you still have to build a control panel. His statement of "no hardware building" isn't achievable. I am trying to help him not make a decision based on a fictitious notion that doing it in software will result in no hardware building. I think it is pretty safe to say that nobody on this forum is using a true analog hardware PID controller. That would consist of only opamps, transistors, resistors, capacitors and inductors. However you go about it everyone is using digital PID that runs software/firmware on a microcontroller.