If you really want to analyse whats going on inside your fermentation cabinet temperature-wise you really need a number of temperature sensors attached to a computer program to log temperatures then post the output into easy-to-read graphs.
Background
About 10 years ago I bought myself a simple thermostat from a hydroponics shop that would allow me to have some control over the temperature of my wort during the fermentation stage. The theory I concocted for myself (and was not validated by someone who understands the physics of temperature control) was that if I could control the ambient temperature of the air surrounding the fermenter (in Australia we don’t generally use the term “carboy”. The most common term here is “fermenter” and this is the term being used in this article) containing the wort then I could reasonably expect that the temperature of the wort would be more or less the same as the ambient temperature. I was really tired of having to make a point of checking the fermentation cabinet each day to make sure all things were as they should be and manually switching on lights to heat the wort or open the door to let some heat out. I wanted a solution that I could “set and forget” until fermentation was well and truly done AND leave me reasonably comfortable that I could rely on the solution to keep my prized wort where it should be temperature wise.
I am happy to say that to this day I still use the thermostat but it does have its limitations. For a large number of these 10 years I lived in Brisbane, Queensland, Australia where the temperature all year round is extremely moderate, typically around the mid 20s in winter to low 30s in summer. This was a main factor that allowed me to use a heating only thermostat in a reasonably well insulated cabinet quite successfully. The other factor was that our garage was under the main roof of the house and was insulated. Some time ago we moved to Toowoomba, Queensland where the temperature variances are not so moderate and can change significantly and quickly, also my home brew setup in now in a 6mx6m (approx 20′ x 20′) tin shed. I can distinctly remember one day where we had the air conditioner during the day as it was very hot then had the heater on that night when a cold snap moved in!
Since moving to Toowoomba I have purchased a cooling thermostat, one which switches something on when the temp gets too high, and have set up an old fridge as the cabinet for brewing in summer. I still use my main cabinet with the heating thermostat for brewing in winter. Both work quite admirably but it relies on the ambient temp of the shed staying on the right side for the thermostat and cabinet I have chosen for fermenting the brew. That is, the ambient temp of shed must be lower than thermostat setting on heating thermostat OR ambient temp of shed must be higher than thermostat setting on cooling thermostat. Most of the time this has worked ok but when weather changes unexpectedly and remains for a number of days I have had to intervene and manually “fix” the temperature problem.
Computerization – Temperature logging: the input
The other nagging question in the back of my mind has been “how right am I on my theories of maintaining wort temp by maintaining ambient air temperature”? The only way to effectively do this is to somehow hook up a computer to various temperature reading devices and record the data.
I am happy to say I have successfully completed this task and provide the statistics of my first “logged” brew for you to view. After looking at the graphs I can say that my theory was “partly” correct however I did manage to maintain a reasonably accurate ambient temperature of the wort for the full duration of the fermentation stage. Due to unforseen circumstances the wort sat for 11 days before bottling but that has not affected the brew at all, it just means there is more data. My brews are typically ready for bottling between 5-7 days.
The fermenter and cabinet setup
Here is a picture of my fermenter in the cabinet. The pics were taken after the brew was bottled, thats why the fermenter is empty. Note the points where the sensors are located.
Here is a close up of the wort sensor. I cut an insulated cover of 10mm neoprene to protect the sensor from the cabinet ambient temperature and all is held in place with duct tape. The actual sensor is located about the middle of the neoprene cover. I dont know for sure how acurate this was as the placement was another theory. I will be running a test soon with the wort sensor in place as well as a sensor in the liquid (probably just water, as a test) to see what variances might be between them.
Here is a close up of the thermostat. It runs on 240V AC. I set the temp I want to maintain with the dial and when the temp drops too low below the setting the light comes on. The switch on the left allows me to switch off the thermostat. If you look closely you will see the Globe sensor held in place with duct tape on the top of the thermostat control box on the right.
Here is a close up of the thermostat sensor with my sensor attached to it. I was able to obtain accurate information about what temperature the thermostat switched on and off at (called hysterysis). The silver probe is the sensor attached to the thermostat, the black probe is my sensor attached to the computer.
Computerization – Graphing the results: the output
Click on any of the days in the calendar control below to open a graph page in a new window to see that days temperature logs. Once the graph page is open you can scroll through the various days. The links to last 12 hours and last 6 hours allowed me to see what my brew has been doing lately when it was live – it probably doesnt mean much here. As I started the fermentation stage at 4:30pm on Sunday 10th October, the 24 hour period starts and finishes at this time each day. The logging was switched off at about 8am on the 21st October.
There are 5 temperature sensors:
Wort: duct taped (100mph tape) to the side of the fermenter and insulated from cabinet ambient temp with a piece of neoprene (stubbie cooler material). The first few days I was insulating with a folded teatowel so I changed it when it “seemed” to me that it wasnt providing accurate temps.
Globe: this sensor is placed about 5cm from the globe that is used to heat the cabinet. I wanted to see when the globe was switched on and when it was switched off. This worked very well. This data allows me to estimate the electricity running costs for the brew.
Sensor: the sensor is actually taped to the sensor probe of the thermostat. This is located near the bottom of the fermenter which is about the middle of the cabinet. This tells me the hysterysis that is programmed into the thermostat I have been using (which I have never known until now). This is preset and I cannot adjust it.
Shed Ambient: the ambient temperature of my tin shed. This temperature is extremely important as it is one of the most important factors dictating the internal ambient temp of the cabinet. The other factor that is equally important is the effectiveness of insulation I have in my cabinet.
Top: the temperature at the very top of the cabinet. I was interested to see how much the temperature changed between top and bottom of the cabinet.
Considerations when viewing graphs
You will see the hysterysis “shift” higher and lower at several points. This is where I have adjusted the temperature for the thermostat to compensate for wort temps.
To view a time section in any graph, click and drag left or right and the selected time period will be displayed in the full width of the graph.
The graph page should resize (width wise at least) to your browser. Please let me know if it doesnt (provide browser and screen res you are using). For whatever reason, the graphs are not viewable on iPhones (well, mine at least, its a 3G).
This dataset is not what you would call a completely controlled experiment however there are some interesting findings. For instance, when the shed ambient temp was lower but close to my thermostat setting of 22 degrees (say 18 degrees), the wort seemed to gradually drop in temperature. when the shed ambient temp was lower but further away (like 10 degrees) the wort seemed to increase gradually in temperature. It also tells me that maintaining cabinet ambient temp is not enough to keep a strictly accurate wort temp. More sophisticated methods might be required to achieve this. More controlled tests need to be performed but this is a very good starting point. I am really quite pleased with the information I have been able to gather.
Where to from here?
The upshot is that for the duration of the brew I was able to remotely access my home server to see what the latest readings were and therefore monitor my brew 24/7 without having to go into the shed. I created a simple page on my server that provided details of all the required services that need to be running to log the temps, when the temps were last read and what the temps were and all accessible through my iPhone. I found this information invaluable and needless to say it impressed my friends, particularly the home brewing ones!
In time we intend to provide all the necessary details on how you can set this system up for yourself with minimal outlay. All the software we have used for this project is open source and therefore free – that was one of our main priorities. However, we do encourage you to donate to the various groups that provide their software for free as without the thousands of hours that have been dedicated to developing all the various software packages we have used (not to mention the Ubuntu operating system) this post would never have been written.
Our end goal is to provide a website where you can login and monitor and maintain your brews remotely. The idea is that once you have an account at www.fermentinator.com you can enter these details into our software on your home server and your data will be “pushed” from your home server to the website. Opening up your home network to the internet is not difficult to do but its not for the faint hearted. You need to have a solid understanding of what you are doing and what the implications might be (ie having your home computers hacked). I have dedicated firewalls, logging and security systems in place to protect my home network. We make no recommendations about remotely accessing your own home server, do so at your peril.
Now, if you partner this work with the work that Andrew has done on building a heat sink and peltier module (my next project), introduce some new computer hardware to control the switching on and off of the peltier modules (USB Relay devices) and pretty much all my issues with ambient temps and current weather patterns will disappear!
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