The “Bubble Logger” Project!

I am working on a ferment Logger/controller, measuring “Temperature and Sound detection of CO2 bubbles” for NodeMCU (ESP8266). The software give an indicative SG estrimate based on S-airlock is used with a precise amount of water (4 ml)!


This project measure:
1. the Sound-bubbles as CO2 escape the fermenter by a digital Sound Sensor Detecting Module LM393
2. Temperature by ds18b20 and offset correction!
3. SG is calculated from complex model.
4. One channel Relay to control a heat source.
(I used the cold sheed or cold utility floor as cooling, and hence, only need a heat source)

Hence, we simply make use of the “Big Blops” coming from airlock during fermentation. Ever tried to put you ear near to the airlock? You be surprised how loud the sound is and this is what we measure!

As frontend “Ubidots for Education” or “Ubidots STERM” is used!


Knowing the yeast activity though CO2 bubble measurements over time including the start of decline, we can better foresee when the SG is close to FG, and better make decision on dry-hopping, temperature changes, etc.!

Brooklyn Lager Clone:

“Yoga Pils”:

Project outcome

Hence, the goal is to have a temperature logger/controller, one tiny device to take care of measurement of fermentation rate, e.g. showing Acivity as CO2 “Sound-bubbles pr Minute” (SBM) and a same time control the temperature at one setpoint! Secondly, to give an indicative SG estrimate with a offset of +/- 2 SG units. The idea is to get one device instead of having both a temperature controller and fermentation-rate logger at a very low price, e.g. 10$ or EUR! Secondly, the idea is also to remove a lot of soldering (e.g. Ispindel) and to get away from placing anything in the tank (e.g. Ispindel/Tilt). In some sense this is a DIY Plaato.


* Airtight – For CO2 to be measured the fermenter needs to be airtight! Hence, FORGET you buckets! You need sealed AIRTHIGHT tanks to do this!
* Sound detecting is prone to sound, hence, best placed in box/fridge even the calibration is set to allow rather much noise nearby.
* Sound sensor is prone to moisture, needs a “condom” (small water balloon, se below)!
* Krausen-yeast-particles or wort shooting out onto the sound detector will set-off the measurements! hence, …..
– A airtight Blow-off system is needed if you use low headspace,
– Or, a high headspace of 33% together with a low temperature and hence a slow fermentation can also overcome the issue!
* All calculations is based on precise amounts of wort, hence, keep eye on you amounts in Liters.
* The logger post to Ubidots every second minte, and as missing SBM post will influrence on precision of SG estrimation, you need good/steedy WiFi.