I'm trying to use an arduino to regulate the air pressure in a balloon. Is there an actual pressure regulator that exists that can be controlled with the arduino directly? The only solutions I can currently come up with are the following:
Use a servo to turn the knob on the pressure regulator to modify the pressure.
Open a valve to increase pressure and use PD control to regulate it
have different valves connected to different pressure regulators and open the valve with the corresponding pressure we want.
The latter is the old implementation, but I feel like there must be an easier way to do this. I've looked online for pressure regulators, but I've found only industrial equipment. Is there any regulator that would work with small volumes and low pressures? (e.g. 1-2 cm^3, <75 psi)
Yes, an SMC ITV will turn voltage directly into pressure. They're not cheap - even at eBay prices they usually go for more than $200. They are 'industrial' which means they take a 0-10v input, necessitating a few components to interface to an Arduino.
Look into VSO valves for something that can be directly controlled by PWM - it turns voltage into flow - this will work for option 2.
Just would like to add another possibility how to regulate the pressure. Solenoid valve can be used and the pressure can be regulated based on frequency (time) when the valve is opened.
I've actually considered connecting a motor to a standard pressure regulator for this purpose. I bought some cheap "untested, as is" SMC ITV electro-pneumatic regulators on eBay a while ago but didn't get them to do anything, they're probably broken. I haven't gotten around to opening them up to see if I can spot the problem.
I just checked for the VSO or proportional valves but didn't see much of interest at my price range. I have some oxygen concentrators that use nice little electric flowmeters for automatic flow control but I haven't found anything similar for sale at a reasonable price.
I'm currently using a solenoid valve system similar to your option 3 to provide two different gas flow rates, not pressure. I am considering using solenoid valves and pressure regulators to provide multiple pressure settings for another part of the system in a future upgrade.