Pressure Switch Issue

Hey all! Was having an issue with our pneumatical test bench, and I was just wondering if anyone had advice as I’ve never seen this issue before. The air compressor will either turn on with the robot. Meaning even without it being enabled it is turned on, will not shut off, and will build air but its gauges are weird. Or it won’t turn on at all. I can go between these modes by messing with the pressure switch cables and the actual switch itself (while the robot is off, of course). I hoping someone had an idea. As I tried replacing the components with tested working ones.
Thanks in advance
Hatchet Robotics, 8116

If you can show a diagram of how you’ve wired and plumbed everything and share the relevant code that would help. If you can describe “weird” in the format “I expect X but I experience Y” that would also help.

The compressor should only turn on when the robot is enabled. That will be the behavior when you’ve plugged the compressor into the dedicated compressor output on a PH or PCM unless you are overriding it with code or the PH/PCM is broken in a way that provides power to the compressor constantly. If you’re using a relay to power the compressor, you’re on your own to ensure the controls are correct in code.

When the robot is enabled, the compressor should only turn on if the pressure switch indicates that the pressure is below its threshold (roughly 115 psi for the Nason KOP switch). The Nason switch is closed when the pressure is below the threshold and open when it’s above the threshold. I haven’t worked with the Rev analog sensor but the rules are the same and I imagine its default behavior is game-legal.

If you haven’t already, it would be good to isolate the air supply system (compressor, relief valve, switch, gauge, manual release valve) from the rest of your pneumatics so you can make sure just the control is correct without downstream systems interfering.

This is basically the minimum legal pneumatics system. The best way to avoid troubleshooting pneumatics problems is to build the system one piece at a time and make sure it all works as expected before adding the next system.

Please post photos showing clearly all the connections in your pneumatic system. It would also be good for you to have a meticulous team mate and/or mentor check your system against the drawing provided by @Ninja_Bait

It will build air, but the gauge won’t move. Sort of flickering in place. That might just be a leak. I know its building air as when I twist the handle of the pressure vent. Large amounts of air will release.

I don’t have any images as I plan to put the test bench back together with the rookies step by step. as for asking mentors, they don’t have a clue either.

If the gauge is not measuring pressure correctly (and you’re seeing the same behavior with multiple gauges) then it might be hooked up wrong. A common mistake is mixing up the ports on a pressure regulator which creates all kinds of weird behaviors. But then again, if you’re building step-by-step you shouldn’t have a pressure regulator at this stage.

The bench was finished. It even had double solenoid values for pistons. I’m guessing since only rookies built it and I could only advise them (I’m the only person with experience as the others graduated in 2022). So I’m assuming something was built incorrectly.

I have no doubt something is wrong :smile: but without details all I can tell you is to build it gooder. Rather than try and troubleshoot an unknown number of problems, take the whole thing apart (code included) and start over from scratch, working your way step by step. This is the manual to follow: frc_pneumatics_manual.pdf (

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thanks for the advice! We will try that at our next session. Have a great day!

No problem, pneumatics are the number one thing I deal with as a Robot Inspector. One thing that isn’t in the manual but is important to keep in mind as you teach about the system is that all of this control complication is for safety - if a pneumatics system over-pressurizes and blows up in a kid’s face, that’s bad news.

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They don’t need to understand pneumatics. A reasonably astute and careful person who is paying attention should be able to follow the drawing and detect errors such as the pressure switch installed downstream of the regulator (a robot I inspected had this error).

Look at your team members and ask the ones who have the attitude such that they are careful, meticulous and demonstrate good workmanship to do all the electrical and pneumatic work. Skills can be taught. It is really difficult to teach a good attitude.