Before I started the TempMaster controller project, I had a PitmasterIQ 110. It kept temperature well but I had to come back after the initial fire start and check on it after 30 min and adjust the fan damper. As an engineer I can't help but wonder that kind of defeats the purpose of using a variable speed fan. (PartyQ does not use variable speed fan so the grill temperature will swing a lot more.) That leads to my motivation to re-write the controller program from scratch to control fan speed based on thermodynamic basics.
Some seasoned Pitmasters will argue that 20~30 degrees overshoots don't make a noticeable taste difference in the final results. True to that, but that also means the controller will not control a weber kettle, or a weber go-anywhere, or an Akorn jr or a PK grill that well...all the PID controller is tuned to control a large ceramic kamado so you may see even larger temperature swing on a smaller grill. Many of us own multiple grills and why not use one controller to control them all within 3 degrees of swing? It can be done, but no reason to do it if one company has dominated the controller game for so long or corporate with well established distribution network. But we are makers, so my motivation is different - If can be done better, we do it better.
It's like vacuums, all vacuums vac but then there is Dyson.
Your grill temperature graph should look like this.
