Guys, to be honest, I'm quite a newbie to electronics on this level but I'm not sure why a PID is the way to go. Let me explain:
I'm a Delphi programmer and I noticed there are examples of Delphi programs working with Arduino boards using the com port.
What I want to do is switch the power of the kettle on or off, depending on the readings of a temperature sensor. When the power switches and for how long is going to be decided by a Delphi program, using the rise in temperature per minute, the amount of fluid, current temperature and target temperature etc.
In future I maybe also switch an overhead stirrer on and off, based on the timing in the program and the recipe I'm using (don't call me lazy!.....)