Cherry Pie Brewery: A Microbrewery Control Strategy
``Are you working on your Cherry Pie again,'' she asks me. I was indeed busy configuring the Raspberry Pi to control my new fully automated brewery. My days of using malt extract and stirring a pot on the stove was over. I wanted to be a true artist and start all-grain brewing.
A Heat Exchange Recirculating Mash System (HERMS) was chosen as the perfect process to implement. For most home brewers, controlling the temperature is all that is needed, but I wanted to control as many variables as possible.
A control philosophy was developed for 12 steps in the HERMS stage. The fermentation stage required 5 steps, while a final clean-in-place stage required 11 steps. To achieve this, 28 inputs (temperature, level, flow) and outputs (pumps, valves, heating elements, motors) was needed.
The Raspberry Pi is a microcomputer, running the Linux operating system. It is low cost and supports other low cost instruments. A circuit board was designed to facilitate the connection between the Raspberry Pi and instruments. A decentralised control strategy with Proportional Integral Differential (PID) control, and the timing sequence for switching the equipment, was executed with Python code. It was also setup to serve as a control panel that could be accessed remotely over the internet. All the major electrical components were safely enclosed in a control box.
Magnetically coupled pumps where selected to drive the process liquids and solenoid valves controlled the flow. Three stainless steel vessels were used and equipped with fittings to connect to the silicon piping system. A custom actuated control valve was also designed.
There are several components still missing in the design and an advanced process control strategy will be considered for the future.
This is how the Cherry Pie Brewery was born.
Chapter 1: Introduction
Chapter 2: Process description
Chapter 3: Control philosophy
Section 3.2 HERMS
Section 3.3 Fermentation
Chapter 4: Mechanical design
Chapter 5: Electrical design
Chapter 6: Software design
Chapter 7: Control design
Chapter 8: Recommendations