Accurate control of the mash tempterature is essential to maximise efficiency and improve repeatability of the same brew. Temperature can be controlled manually by turning the power on and off to the heating element and monitored with a thermometer. Alternately, a controller can be utilised to automatically control the mash temperature, facilitate step mashes and allow remote control of other devices such as pumps.
Building a controller to regulate mash temperature takes all the guess work out of maintaining a stable temperature. This can be done by anyone with some basic DIY knowledge and patience. However, if you are unfamiliar with power safety and electronics please ensure you get help from someone with the required knowledge. MAINS POWER KILLS and connecting live, neutral and ground wires incorrectly will create an extremely dangerous situation!There are many different types of controllers available in the market to suit all requirements and budgets. Some controllers will regulate temperature based on hysteresis (ie set point -/+ 1oC) to turn the heating element on and off. However, one main problem with these controllers is that the heating element turns off when the temperature sensor reads the desired set point. This sounds fine in theory, but in practice the liquid temperature will continue to rise after the element turns off. A good way to think about it is a car coming up to a stop sign only hitting the brakes when at the stop sign. The car won’t stop at the stop sign, but rather at some point past it. The other style are Proportional Integral Derivative (PID) controllers. These controllers continually calculate the error between the set point and current temperature and turns on the heating element in response to the error. This means that as the temperature approaches set point, the element will be switched on an off so as to minimise overshoot of the set point, and then will control the element to maintain the temperature at the set point. Visit Wikipedia for in depth information about PID controllers.
For the ultimate control of your brew rig we recommend CraftBeerPi. It is a free Raspberry Pi based open source software not just limited to controlling heating elements. If it can be connected to a solid state relay, then CraftBeerPi can control it, such as pumps and valves. It can also accept and display multiple one wire DS18B20 digital temperature sensors and control the associated heating elements.It has so many great features such as setting up step mashing programs, controllable from your mobile phone and can trend your mash temperature just to name a few. CraftBeerPi is the controller we have chosen for our brew rig due to both its flexibility and community nature of the project. Although it is completely free, you can donate via the CraftBeerPi website to help fund ongoing development.