CO2 production sensors

Balloon CO2 production sensor
It is very interesting to follow carbon dioxide production during the fermentation. This gives information about how fast the fermentation is and when the fermentation is completely ready. When you measure the amount of produced carbon dioxide you can calculate the current SG without measuring the SG with a hydrometer. Tcontrol has the functionality on board to calculate the current SG when you fill in the amount of wort and the starting SG. Tcontrol only needs to receive digital pulses from the Ballon carbon dioxide production sensor to know the amount of produced CO2.

These digital pulses are made by the Balloon CO2 production sensor. I have developed a printed circuit board for this sensor. The sensor also has a three way air valve, a punch balloon, a pressure switch and a 24 Vdc power adapter. 

Now the CO2 production sensor I use mounted on a piece of wood to get a even more repeatable measurement. See the following photo an film.

Working carbondioxide production senor

                                    Complete CO2 production sensor

                                    Side view.

                                The sensor in action!

How does it work?
First the valve is off and the carbon dioxide flows from the fermentation vessel into the balloon. When a over pressure of about 2 mbar is reached in the balloon the pressure switch switches on. Now an adjustable timer is started (0.2 .. 24 seconds) and the valve is switched on so the carbon dioxide flows out of the balloon into the free air. The adjusted time should be that long so the balloon is empty to start the next cycle. Every time the valve switches on a galvanically isolated optocoupler output is switched on. This output can be connected to the Tcontrol-IO board to count these cycles (pulses) by Tcontrol.

How can I get it?
The complete CO2 production sensor including pulse stretcher board, three way valve, pressure switch, balloon and 24 Vdc adapter is EUR 92.50
Search on ebay for "Balloon CO2 production sensor" 

Specification for the Balloon CO2 production sensor:
Power supply: 100 .. 230 Vac for the 27,5 Vdc adapter EU type (USA type on request)
Outside diameter for the CO2 input: 9 mm
Measurement range is 0 till 50 liter CO2 per hour. This is enough for a fermentation peak of 50 liter young beer. 
Amount of CO2 per cycle: 74 ml. 
Optocoupler output: maximum 25 Vdc maximum 3 mA
Delay time: adjustable 0.2 till 24 seconds.

Build a CO2 production sensor yourself!

In the next picture you see a CO2 production sensor you can build yourself. This one is less accurate then the balloon sensor but this one can be good enough to see the fermentation activity. 
Success with building this sensor. Also this sensor can be connected with Tcontrol-IO to use it together with the software Tcontrol.
Please mail me your results with this sensor because I am curious for the results, 

Previous experiments with other types of CO2 production sensors
During fermentation of beer alcohol and carbon-dioxide are produced in a fixed ratio. When we can measure the amount of produced CO2 then we know the current SG of the beer during the fermentation. And when we count the produced CO2 per hour then we know the severity of the fermentation. This gives us more feedback of the used yeast or yeast starter. On the Dutch homebrew forum William came with the idea and RobertW found a good solution to make a simple bubble counter. During that time I integrated the bubble count possibility into Tcontrol. The purple curve in Tcontrol gives the severity of the fermentation per hour.

My first bubble counter looked like this.
This bubble counter was too small. During heavy fermentation too much of the carbon-dioxide was not measured correctly. Therefore I made a bigger bubble counter which could more easily measure a heavy fermentation.

Here a short film of the big bubble counter.
This one worked fine and accurate enough. But the disadvantage was that the water became dirty and I don't like that in the neighborhood of a beer fermentation.

That is why I developed a Pulsating  CO2  volume sensor with a silicone glove.
Near the hinge a micro switch with a changeover contact is used.
The disadvantage of this Pulsating sensor is the hard sound of these valves and that one valve is almost continuously on and becomes very hot. 

Balloon CO2 production sensor
The most promising sensor till now is the Balloon CO2 production sensor without water, sound and becoming hot. A film of this one is hereafter.

The bill of materials is.
  • Three Way Two Position 1/2" NPT Solenoid Valve
  • Pressure switch 1 .. 10 mbar
  • punch ball balloon
  • 3 pieces 1/2" brass hose 
  • Relay 24 Vdc with a changeover contact SPDT
  • Diode 1N4007
  • Silicone cork with two holes
  • 24 Vdc power supply 0.3 Ampere 
Build then a sensor like this one.

Connect the relay contacts to the counter inputs of Tcontrol-IO and the  CO2  production sensor is ready. Instead of a relay also a optocoupler can be used.