Hi! I'm working on an experiment regarding the biodegradability of materials. For this we use a system composed of jars that contain different materials and that are connected via tubes that allow air to flow from one jar to the other. To make the air flow we use a standard air blower used for fish tanks (the little ones, they don't generate much pressure). To measure the CO2 emitted we need to redirect the flow of air from one of the jars to a container where we trap air and use a CO2 sensor to measure it. After measuring then we need to redirect the air flow again to the jar.
To control this we thought of using two electric valves in opposite states (when one is open the other one is closed). This way by opening and closing the valves we can control if the air either goes to the container for measurement or to the jar. We would use an Arduino UNO to control the opening and closing of the valves (using relays if necessary). The problem with this is that most electric valves we've found are for liquids and not air. The few valves we found for air are really expensive and go beyond our budget.
Any help, advise or personal experience that could help us with this project is deeply appreciated!
I'll leave you guys a photo we took of our setup so far. You can't see the container with the CO2 sensor in this photo (because we don't have it yet) but the basic idea is to introduce it in between the jars and somehow redirect the flow of air to it using and Arduino whenever we need to make a measurement.
There are plenty of cheap solenoid valves that will be fine for controlling air. Just hop on ebay or Amazon or whatever marketplace you like and search for "solenoid valve".
You may have to search for solenoid "gas" valves. They make them for flammable or non-flammable gasses. Solenoid air/gas or liquid valves for industrial or lab use usually aren't cheap.
Most solenoid valves I found in my country's store are made for cars and I worry about possible leaks. Are you sure a car valve would not have leaks? They're kind of expensive since I would have to buy 8 in total.
I've used quite a few solenoid valves, both the cheapest of the cheap from the Chinese sellers on eBay, and well used ones purchased from eBay or salvaged myself. I don't remember every running into one that leaked. I haven't used an automotive solenoid valve, but it wouldn't likely do much good to a car if it leaked, so I'd guess they have that sorted. One thing to look out for: a solenoid is just an electromagnetic coil, which is used to drive a linear actuator. So be careful that you are getting the entire actuator + valve assembly, rather than the coil alone or the coil+actuator. You can purchase replacement solenoids for a solenoid valve, but the solenoid alone won't be super useful for your application.
Those are the sort I was using for my applications which required higher pressure and flow, so I haven't experience with the small and cheaper ones. But this common and cheap style looks very interesting:
