BrewPi: Raspberry Pi and Arduino Powered Fermentation Chamber 96
For the homebrew hardware nerds out there who also homebrew beer: "BrewPi is an open source fermentation controller that runs on an Arduino (for now) and a Raspberry Pi. It can control your beer temperature with 0.1 degree precision, log temperature data in nice graphs and is fully configurable from a web interface."
Source code. The article has lots of photos and screenshots. The project involves rewiring the compressor's electrical connection through a PID controller, and includes both a fancy OLED display on the fridge and support for logging statistics and control over the web. If you've ever had the joy of gradually crash-cooling a lager (not too fast, not too slow), the software includes settings to effect gradual temperatures changes in the fermenting wort. Certainly fancier than a Johnson controller and a probe attached to a fermenter with a strip of insulating tape.
Re:Do the same with a handful of transistors (Score:5, Insightful)
You reckon you can do temperature control in an uncontrolled environment with a handful of transistors? Keep in mind the external temperature is uncontrolled. The yeast itself generates heat within the ferment at varying (and often unpredictable) rates.
The simplest approach you can reasonable consider for the level of control they're looking for in their environment would be a PID controller, which if memory serves me correctly will have more than a handful of transistors in it. You're going to need a pretty decent PID to handle temperature profiling, which their solution
They're using cheap, off-the-shelf parts to solve their problem, which in turn allow them to put extra features in there like web control, and it's now much easier for anyone to do the same thing. The parts may not have existed in 1964, but you need to keep in mind The Doors aren't the only good thing to happen since then.
Re:Do the same with a handful of transistors (Score:4, Insightful)
Why does it have to be a Raspberry? Why do you have to control it in C? Is it because people don't teach or know how to do it the old school way anymore?
Do you want to explain how to make a tunable PID loop out of transistors? Yes it can be done, but the commercial loop controllers I used 30 years ago certainly had their foibles. And there is a hell of a lot of useful fundamental old school control theory that can be learned in doing it the way they have. Proper manual loop tuning is just as much an education as building a circuit out of individual parts.
Re:Do the same with a handful of transistors (Score:5, Insightful)
Why does it have to be a Raspberry? Why do you have to control it in C? Is it because people don't teach or know how to do it the old school way anymore? Is the effect somehow less if you DONT have a fancy OLED display?
Why? Because these methods are objectively better than the old way. And I say this as someone reasonably experienced in the old school way.
The controller is far more sophisticated than a simple PID loop, even if you ignore the ability to log the temperature history, store profiles, query the status remotely, etc.
The OLED display isn't necessary, but it's actually a helpful, useful feature to be able to display the status of the system clearly and unambiguously.
And good luck implementing this "the old school way" in the same period of time as someone using these tools could do it.
It doesn't have to be a Raspberry Pi or Arduino with a spiffy display, but there's no glory in doing things the hard way. There's educational value in it, and in knowing the basics, but a system that works doesn't benefit from having been hard to build.