You can go as simple or as complex as you like. Many guys set up dual temperature controls with both a cooling and heating source. I went the simple route. I built a small box that fits in my fermentation chamber and rigged it up with a light bulb outlet. I then put a 40 watt bulb in the socket, cover the whole thing with tin foil so no light gets out and place it in the chamber. I'm currently fermenting at 75 degrees in my garage, which is between 30-50 degrees right now. Downside to my method is that your fermentation chamber cooling will kick on occasionally to keep the temperature down and the light bulb is always drawing electricity. I experimented with different bulb wattage and found the 40 watt was right for my chamber. Kept is warm enough, but not so warm that the cooler was running constantly. If the chamber is larger you may need a larger bulb.