I've been working on this chamber for some time just recently got it performing properly. The first version used a dorm-room fridge for cooling, but I found that it had to work pretty damn hard to maintain mid-60's temps and I would really like to start doing some lagers w/o having to use space in my keezer.
Here's a shot of the inside - Enough space for (4) corney's and a couple of carboys on the bottom level w/the possibility for a couple more carboys on a shelf (would not trust the bit of wood thats just sitting there in this picture)
so; with the mini fridge as the cooler the chamber would hold right around 62 deg w/o a temp. controller or anything, but the thing ran way more than it should have... I added another layer of insulation and that seemed to help the fridge a bit but it really never got any cooler than 60deg.
I was talking to one of my friends and he mentioned that he had an extra window air conditioning unit he wasn't using and needed a mini fridge, I took the opportunity and traded the fridge for the AC. After re-working the chamber a bit to seal around the AC instead of the fridge I switched her on and managed to get everything down to about 60 deg. The AC definitely has way more cooling power than the minifridge and its compressor doesn't cycle on nearly as much, so again, this is fine for doing ales, but I want to lager.
I did a bit of reasearch and ended up grabbing a couple of Solid State Relays off of ebay (25amp/120v i think they were $7 each, shipped from china). I took out the AC's thermostat and wired in one of the SSR's. I plan on using the second SSR for running a heat source of some kind
I've been working on a "generic" arduino controller w/the goal of using it to control a brew rig at some point in the future, so i thought this would be a good test case for it. I Hooked it up to the relay and did some quick modifications to my program and now have it running the show (using a DS18B20 as the temp. probe) The brew controller includes 32k of eeprom and a real-time-clock chip, so my next step is to modify the program to do some sort of data logging of the actual beer temp and possibly program in timed temp. changes..
Here's a shot of the controller, set to 45 deg.
I did an empty test run and managed to get the chamber down to 34 deg in about 15 minutes. So far so good.
I've got a batch cold crashing right now and plan on fermenting in it at some point in the next few days.
Its a bit of a hack job but it seems to be working great!
I couldn't have done it with out all of the great information in this forum!