Servo Controlled Pneumatic Valve

Recently I came across the 8 mm pneumatic tubing with its various valves, quick-fit couplers, etc. They are very cheap and usable for both air and water at substantial pressure.
One of the things I could not find, however, were low-voltage valves (those I found were basaed on 24V solenoids and used some current * ALWAYS* when turned on. Additionally, they did not allow partial opening, which is not of much importance for me but still not cool.

So what I did was adapting a valve intended for