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I recently took up homebrewing and wondered how I could incorporate the Arduino. I think I can. I thought I’d use this article to show my thought process and planning before I even pick up an Arduino, or think about writing code. The Basic Idea Ideally, I need to keep my fermentation vessel between 18-25°C. The spare room that I’m using is sitting at about 16°C, so I need to find a way to control the heat around the vessel. I can’t put anything in the vessel as this may introduce contamination, or break the seal on the vessel. I’d also like some lighting to let me see what’s happening inside the vessel since the vessel is semi-transparent. Any other info would be a boon. OK, so I know what I roughly want. Let me look at the pros and cons of the various things.
Vessel Heating This is the one thing I really need, so this is the priority. Initially I was looking to modify something that’s readily available like a heated car seat, or a pet blanket. Mainly those as they’re low power (around 12V), but after more reading I’d be as well sticking with what I have just now, a reptile heat mat that I can wrap around the vessel. I just need to find a way to control the heat mat. Temperature Reading Like I mentioned earlier, I can’t put anything in the vessel so I’m going to have to make do with a reading from the outside. I know I can accomplish this with the DHT temperature/humidity module that I’ve used before. I’ll just have to make sure it’s firmly touching the outside of the vessel but not too fixed as it will need to be removed before cleaning the vessel.
Temperature Control Now that I have those two nailed, I can try to figure out a way of controlling the heat mat. After a lot of research I think a relay switch is the best option. With this I can use the Arduino’s 5V to trigger the switch to an on/off position. I’ve not used switches much, but the gist behind them is to put the live wire from the heat mat through the switch, which will break the circuit, then, when required, energise the switch with 5V to complete the circuit and the heat mat will come on. Controlling the heat mat, I’ll probably use the figures from the DHT module with code something like: if temperature <19 turn on heatmat else if temperature is >22 turn off heatmat My thinking for the 19 and 22 is that the final temperature should be around 20°C to 21°C, but either way anything from 19-25°C is fine.
Another reason for the not-so-strict heating in my pseudo-code is that the heat mat will take about 20-30 seconds to reach full heat. I’m not worried about this as it is never hotter than about 32°C, it will take a while to heat the liquid inside, and, conversely, it’ll take quite a while for the liquid to cool down. Hence, while the heat mat may be on for a little while it should need switching on/off only every few hours, at least, so it’s not like I’d be switching it on and off every few minutes. Well, that’s the theory. We’ll see how that pans out in the practical phase.
Logging I still have a spare ESP WiFi module, so I can probably do like I did with my plant monitoring project where I send the data to ThingSpeak. I’ll probably note the temperature and humidity over day and time. Of course, day and time may mean I need to use a real-time clock module. Unless ThingSpeak tags on the day/time. Not sure. Can’t remember if they do. I could also log the brightness of the room using an LDR, but the light level has no bearing on the brew, so scratch that. I’d like to have an alert system where I can get an SMS/email should the temperature go haywire. This is a possibility using ThingSpeak and Twilio, but is not something I’ve tinkered with before and will leave this to the end as it’s not critical.
Lighting Lighting is not critical, and will be manually controlled, so I’m not too worried about this. This will be a strip of 12V LED lighting with a transformer and a switch. No need for the Arduino to control the lighting. One major consideration for the lighting though is that it must be removable as the vessel has to be bleached sterile after use. I’ll probably just attach the light strip(s) to the vessel with some tape or blu-tac.
Additions I have a spare IP camera that doesn’t seem to move up/down or left/right properly, so I might use it to view the fermenting vessel by putting it near the top rim to see in. My only query here is that if the camera switches to night vision mode, will the IR lights reflect off the vessel and bleach the image making it useless? Not sure, but that’s something to test. A further addition could be an LCD screen. If I put the screen near the top of the vessel, and within range of the camera view, I could monitor the temperature remotely. As a quick visual-at-a-glance aid, I may add some LEDs to show if the temperature is within a certain range. Maybe between 20-22 could be a green LED with 25+ being red. Maybe 19 or less is a yellow LED.
Conclusion The basic idea of controlling the temperature of the liquid with a heat mat is definitely possible. Same with the logging. Shouldn’t be a problem. The lighting (to see inside) isn’t a necessity and not Arduino controlled, so it’ll be left until last probably. Same with the IP camera. Nice, but not a necessity, and not Arduino controlled. I’ll more than likely include the LCD screen as it’s a nice visual guide to the reading from the DHT and I can compare that against the thermometer that’s stuck to the side of the vessel. NEXT MONTH: The project begins with the LCD screen, DHT and WiFi modules.