For Guy and others who are interested. This is the controller I built for my 350 gal propane tank offset smoker. It was inexpensive and does a great job keeping my pit within 5 degrees of set temp. I usually see a 2-3 degree fluctuation over the course of a few hours. My pit leaks around the doors a little and I haven't run any high temp gasket yet, but plan on getting it done asap. It's raining here so I didn't actually hook it all up.
The PID controller in a project box. The black and white wires are the wires that supply power to the CPU fans, the extension cord end provides power to the PID controller and the temp probe goes inside the cook chamber and lays on the grate.
Built these fan mounts with square tubing (think its 4"x4" ID), some c channel and diamond plate. The fans are 60 cfm, and there is one on either side of the firebox.
I plug an extension cord into the plug that hangs below the outlet box, and plug the PID into one of the outlets.
This pic shows the set temp of 250 and the current temp as measured by the temp probe that would sit on the grate in the pit, in the hottest area (close to where the firebox is connected to the cooking chamber)
This pic shows the current temp as measured by the temp probe, and also shows the percentage of fan power. It isn't hooked up to the fans, but if it was they would be running full speed because the current temp is so far from the set temp. Once it gets close, it drastically reduces power to the fans and provides air as needed. Whenever I open a door to remove meat to wrap or take a peek, the temp will drop and the fans will kick on full power, and as soon as the temp starts climbing the fan power will reduce so it doesn't overshoot the set temperature because it is tuned properly. That is the hardest part but just takes some tinkering with the P, I and D values.