While waiting for parts to arrive for our upcoming Yeast Forge product I’ve been putting in some hours on an old project called BrewMonitor. As an aside, when I say a long time, I mean a loong time! Check out an early video I posted back in 2011!

BrewMonitor is an electronic device for monitoring your temperature and airlock activity throughout fermentation so that you can spend less time monitoring your brew manually. It measures the temperature with a digital temperature probe and the airlock activity is measured with an Infrared Photointerruptor attached to a standard goose neck airlock using a 3D printed attachment.

BrewMonitor's airlock sensor

BrewMonitor’s airlock sensor

The current revision (v1.3) control circuit is based on an AVR microcontroller and is very similar to Arduino Leonardo board because it uses an ATMEGA32U4 which has onboard USB support.

BrewMonitor PCB v1.3

A Partially completed BrewMonitor PCB

The firmware and hardware has been almost complete for quite some time and I just felt the software needed a more modern look so that’s where most of my recent focus has been – adding a new Metro style theme and touching up some of the functionality like exporting data for review in Excel.

Here’s a screenshot of the “explore” tab which allows you to explore the memory contents of the BrewMonitor which contain data it has recorded.

The explore tab in brewmonitor software

The explore tab in brewmonitor software

This shot shows temperature and fermentation activity from a recent brew of mine (an Australian Pale Ale). You can see the temperature (blue line) initially dropping down from 20C to around 17C which my fridge’s temperature controller was set to. At this time I pitched my yeast and by looking at the grey area series you can see that there was a lag phase of about 12 hours before airlock activity began. For the first 2 days the temperature is fluctuating rapidly by about a degree while the fridge turns on and off to maintain its set temperature. Meanwhile you can see the bulk of the fermentation activity also took place in the first 48 hours (the grey area series beneath the temperature series).

With airlock activity slowing significantly I increased the temperature controller’s set point up to 20C to allow the fermentation to finish off nicely. This is shown by a very gradual rise in the temperature because I had no heater in the fridge and it actually took a few days to rise to 20C. Over this period you can also see from the bubbles series that there was practically no fermentation activity taking place.

Finally I crash cooled my beer by setting the temperature controller to 4C. Here you can see a sharp drop in the temperature that started quick, but slowed down and took nearly 2 days to complete. This is because the fridge itself was set to never go lower than the target temperature of 4C, so it took a while to get the beer to reach the target temperature – no big deal really.

After this I let it sit another day or two for the yeast to settle out some more before kegging.

The insights that can be gained from the BrewMonitor are great if you want to step up your brewing quality or investigate your process by recording and reviewing your fermentation parameters, but what’s really exciting is that by having a programmable device that can monitor fermentation activity, adding temperature “control” based on this feedback is just another simple step.

Having a temperature controller that can automate a brewing schedule by making intelligent decisions based on both time AND fermentation activity is a step ahead of the other “smart” temperature controllers on the market like STC-1000+, Fermostat or BrewPi which only alter the temperature steps based on the elapsed time.

To follow or contribute the BrewMonitor project head on over to our source repo at GitHub.com, and if you’d like to follow our progress head on over to our discussion thread on the AussieHomebrewer forum.

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