I have been considering building a fermentation chamber using a mini-fridge as a cold air source, and was wondering how the Ranco or Johnson controllers work. With the Johnson it appears that you just plug the fridge power cord into the controller unit, and place the probe in your chamber, when the temp drops below your set-point the controller powers the fridge until the temp at the probe reaches the set point, and then it shuts the fridge down. Is this correct? Is this how they all work? It seems to me that powering a fridge on an off often would not be good for the compressor, and being able to modify the internal fridge temp controller (if possible?) to reach my desired set-point would be less harmful to the compressor. I guess this goes back to always being told by old timers that when you lost power, you need to wait 5 minutes or so before turning anything back on that uses a compressor for cooling. Am I wrong and possibly missing something? Are there any controllers availble that actually replace the fridges controller and cycle on and off as the fridge was intended to cycle?