The first was a temperature controller I made a few weeks ago. It's absolutely critical to producing good beer, to maintain the temperature at the right level throughout fermentation. Yeast hates variations in temperature.
Up until now, I'd been putting the fermentation vessels into a small room and relying on keeping the air temperature as constant as possible. I'd done this by turning fan heaters on and off and opening and closing doors and windows. It was as hit-and-miss as it sounds.
I decided to sort it out and made an electronic temperature control unit, copying this design. The unit is based around this little device, which I bought off Ebay:
The screen displays the temperature of the fermenting beer, via a temperature probe mounted in the wall of the tank. You simply set the desired temperature and when it gets too cold it switches on a heating circuit and when it gets too hot it switches on a cooling circuit. It's currently cool enough to operate only the heating circuit and rely on the ambient room temperature to do the cooling.
This is my current fermentation set-up, with the FV on the left. It's wrapped in a foam jacket, to regulate the temperature losses and is sat on a 40W electric heating mat. The heat mat is plugged into the heating circuit on the controller, which is the grey box to the right. The clear vessel in the middle is being purged with CO2, ready for use as a conditioning tank later on.
I also came to the conclusion that my boiler wasn't quite getting hot enough to produce a proper rolling boil. It was always a bit weedy really, so I wrapped a bit of foam around it to reduce heat loss through the sides. This worked brilliantly and meant that I had a nice vigorous boil.