Originally Posted by duboman
Get a temp controller and then you can plug the Bly into it and set the desired temp and it will turn in and off as necessary
What duboman said.
You can build a temperature controller pretty cheaply and easily using instructions from one of the STC-1000 threads over on the DIY forum.
I control temperature in my beers by putting a brew belt on the fermenter and putting my fermenter in a chest freezer. I plug the brew belt into the hot side and the chest freezer into the cold side of my STC-1000 unit. I put the probe from the STC-1000 against the fermenter and hold it in place with a doubled-up piece of a backpacking sleeping pad that is secured with a couple of bungee cords.
Using this setup my beers ferment at 18C (+/- 0.5C) all year round.
Total cost of my temperature control system: ~$290CDN. I probably could have done it a lot cheaper if I had of got the freezer second hand but I didn't want the hassle and bought it new.