I am trying to build a door to a hidden room and want to use pneumatics to open the door. I have purchased some equipment to test with, namely a 12 inch Parker air cylinder and a U.S. Solid 5 way 2 position valve. After hooking everything up I have the following configuration: Arduino connected to relay, relay connected to valve and barrel plug. When I connect the barrel plug to a 24v 5amp DC power brick, attach to pressure (currently have the compressor set to somewhere like 5-10 psi but have tested with 20-30), and run a simple "turn the pin on and off" Arduino code the relay clicks as expected and the valve sounds like it is engaging, however the airflow doesn't change. It remains coming out of the A output. I contacted U.S. Solid and have already got a replacement valve but the same issue occurred with their replacement so I'm beginning to think I'm doing something wrong.

  • $\begingroup$ Are you sure you are supplying enough pressure to the solenoid? Double check nothing is in backwards, physically or code wise too - that's a common mistake everyone makes. $\endgroup$
    – J. Ari
    Feb 1, 2021 at 20:42

1 Answer 1


The specification for that valve states:

Working Pressure: 0.15 ~ 0.8 Mpa

For those still using colonial units, that's a minimum pressure of 28 psi.

The reason it doesn't move is that it's a pilot operated valve. A small airline is tapped off the pressure inlet and goes across the valve to the pilot. The solenoid opens the pilot allowing air to push the valve spool to the left in your photo against the force of the return spring. You haven't got enough pressure to beat the spring.

enter image description here

Figure 1. A pilot-operated 5/2 valve in the off position. Image source: Hafner.

Note in Figure 1:

  • The spring pushing the spool into the home position.
  • The cross-valve pilot air path ending in the solenoid stopper. When the solenoid is operated air is allowed through the white hole and into the spool chamber to push it to the right.

The advantage with this type of configuration is that a low current is sufficient to operate the valve and so they are much more efficient than direct solenoid operated valves, smaller and run cooler.

The downside is that they can't switch low pressure or vacuum without a separate pilot supply - if the feature is available on the valve.

Tip: Amazon is not a good source for component data. "No datasheet? No sale!"


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