[Bruceb]

Not sure you really want to change the pressure by controlling the compressor. They are not the highest volume compressors and take a long time to charge a system. What you can do is have a high and low pressure leg on your pneumatics system. Just have 2 outputs from your storage tank feeding 2 pressure regulators set at different pressures. One goes to your high pressure solenoid and the other to your low pressure solenoid. Just remember to have a gauge attached to each regulator.
This is from the pneumatics manual and will help wiring the pressure switch.

We have included a pressure switch manufactured by Nason. This switch is normally
closed. The switches will open at approximately 115 psi and will not close again until the
pressure drops to approximately 95 psi. This will allow you to turn off the compressor once
you are up to 115psi, saving power in the battery. It must be wired directly to a digital
input and ground port on the Digital Sidecar. No specific GPIO port is designated for the
pressure switch. The cRIO must be programmed to react to the GPIO port that is connected to the
pressure switch. The cRIO will activate the designated Spike Relay to turn the compressor “on” and
“off”. There is no default program in the cRIO to control the compressor power. Do not put the pressure
switch in series with the power supply to the compressor.


Hope that helps.