I have everything wired up, and it is working good, but it seems like the cycle times for the fridge are a bit too frequent. I am using a full size fridge, and have added a few gallon jugs of liquid to act as a heat sink, but am thinking that I may need to put the temp probe in a jug of water as well. Anyone tried this? Here are some pics so you can get an idea of the setup. Anyone tried this? Here are some pics so you can get an idea of the setup.
You need to turn the controller/fridge off immediately. You may fry your compressor in just days/hours, depending on the short cycle prevention it has built in. The controller comes defaulted to 3 min, which is barely enough. Your probe appears to be in the direct air stream of the evaporator fan. This will cause the probe temp to drop below the SP almost immediately upon cooling, then rise almost immediately afterwards because no appreciable cooling took place.
RE: probe and larger thermal mass- Yes, this has been done, and you can find more info in the ebay aquar. controller thread. Most suggest taping the probe to the active fermenter, then insulating it (probe only). When you don't have an active fermenter in there, you can tape the probe to the side of a jug, then insulate it (probe only). Waterproofiness of the probe doesn't have to be worried about that way.
I would suggest a minimum of a couple of cornies/sixtels in there.
The controller is wired for heat, but I haven't added the space heater yet due to it consistently being well above 60 in my garage this time of year. I have my temp swing set @ 1 degree C. I haven't added a reinforced top shelf yet, but once that is done I will be able to handle 4 fermenters at once.
You can leave the temp diff at 1C or even lower it to .5C as long as you have the probe on a 2 liter jug or bigger. If you are a "probe in air" type, a temp diff of 3-5C is more acceptable. Set the compressor delay to its max- 10 minutes.
You may be able to fit 4 fermenters in there, but only one active fermentation at a time can be accurately controlled. Once a fermenter has past the exothermic phase, another new one can be added and the probe switched to it. The passive/finished beer in there with it will go a bit below the temp SP for the active one, but temp control is not real critical at that point anyway.