First: I am new to all this. A programmer for many years, but new to RPi and "physical computing". That said,
I am looking to only-very-minorly regulate the flow of air (through a fish tank sized small vinyl air hose) using RPi/GPIO.
I know of solenoids, but as far as I know they strictly are all-the-way engaged or all-the-way UNengaged (open or closed)...I need a similar device, only that allows partial movement...a percentage of the line to be open (similar to the precision of a servo or stepping motor...maybe in about 4 increments (I don't necessarily need like 100 degrees of precision, just at-least a few steps...to release air at the PSI I decide through software.