How to produce CO2 gas
There are two major ways to produce CO2 gas.
Yeast generated CO2
On the internet, you will find many different methods and recepies to produce CO2 from yeast. All of the works in some way.
I will describe how the carbon regulator can be used with CO2 from yeast production.
First thing you need is a good bottle with cap. A PET bottle is very good to use.
Since the diffuser work at preasure around 0.2Bar, you need to make sure your hose connector to the cap is tight and does not leak gas.
It is not easy to get it preasure tight with just glue or silicone.
After much experimets I have found a perfect quick connector for 6 mm hose.
This quick connector has O-ring and only need a M5 nut. I drill a 5 mm hole in the cap and simply mount the quick connector through the cap.
Inside the cap I have a M5 screw to keep it tight and firm. The quick connector can handle high preasure and has no leakage.
Another advantage is that the hose is very simple to connect and remove from the quick connector.
Carbon Regulator with yeast generated CO2
The picture below show the complete system to generata and control CO2 in an aquarium.
The yeast mixture is in the PET bottle (8). The carbon regulator (2) measure the pH (1) in the aquarium and control the gas valve (3).
By time, a CO2 preasure (P1) will build up inside the PET bottle. When the valve (3) opens, the gas will flow to the diffuser (4) inside the aquarium.
The Carbon regulator (2) will control the gas flow and keep the pH stable in the aquarium.
What happens if the presure get to high in the PET bottle?
The yeast mixture produce CO2 continously and to avoid explosions due to over preasure in the PET bottle you need some kind of safety vale or over preasure valve.
We have solved it by adding a restrictor (6) and a second diffuser (7) placed in a jar filled with some water.
The second diffuser (7) is a mini diffuser which is smaller in size and need high presure to work than diffuser (4) in the aquarium.
A mini diffusor need almost double presure compared to the normal difusor to work properly.
The restrictor help to make larger difference in presure P1 and P2. The restrictor is closed to the bottom and then opend just a quarter of a turn. This gives a good preasure difference betwen P1 and P2.
When presure (P1) builds up too high, it will simply leak out to diffusor (7) in the jar.
In this way there can be no explosion of the PET bottle.
CO2 gas in tube
The picture below show a CO2 tube with regulator and solenoid valve.
The carbon regulator is connected to the solenoid valve and regulate the gasflow from the CO2 tube.
The main advantage with a gas tank is the large amount of gas in the tank. The tank will last for more than a year.
Many use Soda-Club / Soda Stream bottle which has 4.4 mm pitch trapezoidal thread, so you must add an adapter.
There are adapters for trapez to standard EU (w21.8-14) or US (CGA-320) Valve used in the regulator.
Warning, avoid single stage regulators like the picture below
Do not use the cheaper single stage regulators together with solenoid valves. See picture above for some single stage regulators.
The reason is simple, these type of regulators does not lower the pressure at the secondary side, they only lower the flow of gas.
This means that if you add a closed solenoid valve, the pressure will eventually build up (to the max tube pressure) and the solenoid valve breaks.
Always use dual stage (dual gauge) regulators where the pressure at the secondary side is constant.