The ‘pinching’ arm is raised and lowered by an RC Car servo. When the valve is in the closed position, the servo does not need to continually apply pressure, the servo is powered down and the ...

similar to the throttle valve in most gasoline-powered cars. The butterfly vane rotates to vary the flow, turned by a small SG90 servo. A Wemos D1 Mini is used to run a pair of the valves ...