Use the HBT search feature for 'brewpad' and there are a few threads on temp controlling them.
To really dial it in, it helps to have a thermowell inside the beer. I use a plastic fermenter, so just put a thermowell through a #2 stopper in the lid. The RANCO temp controller probe drops in and I can dial my temp in on the control panel.
n.b. I use my setup to cool my fermentation temps down to ale temps (California here) using a fountain pump and ice water bath for my fermenter.