Problem: Pneumatics Not Firing

[hectorcastillo]

We're having an issue with our pneumatics where our operator is pushing the button on his controller to fire a set of pneumatic cylinders, and the cylinders are not actuating. After clicking the button a few times, the cylinders finally actuate. Sometimes it takes three or four clicks, sometimes a lot more, sometimes the cylinders never fire. This happens even when we have full air pressure going to the system. We are having this problem with two systems (the ones we use the most) with one solenoid and two cylinders each. This problem started yesterday during preparation for an off-season event.

We have tried recreating the problem by just firing our systems repeatedly, but the systems run fine. The problem happens mostly while we're doing practice matches both while running motors and not.

Any help with this would be greatly appreciated!

[thatprogrammer]

Have you tried an alternate controller? Maybe your buttons are just damaged.

[hectorcastillo]

Our operator says he tried it and the same problem happened. I don't remember seeing that, so I'm asking him to try it again.

[Rangel(kf7fdb)]

Could it be that your code is running in a way that it checks for button presses at a certain time in the main loop and it doesn't register if the button is pressed when the code is not checking for it? It's unlikely to be the problem based on you guys being unable to recreate the problem but something to check for.

// Sudo Code For Potential Problem
While (true)
  Code
  Code
  Delay         // Main reason button press gets missed
  Check for button press Code
  Code
  Code
End While

[Big Ideas]

Don't forget to check the device.
use the solenoid valve manual override button to verify the valve runs normally. Then operate the solenoid directly with the proper voltage to verify the part is working. Most small solenoid valves must operate with a minimum pressure (15psi depending on device) because the actuator is "piloted" using air pressure assist. try attaching a different (or known good) solenoid and listen for electrical click when energizing. Then trace your wiring. Pay particular attention to the connectors and crimps, looking for loose connections.

[frcguy]

Originally Posted by Big Ideas

Don't forget to check the device.
use the solenoid valve manual override button to verify the valve runs normally. Then operate the solenoid directly with the proper voltage to verify the part is working. Most small solenoid valves must operate with a minimum pressure (15psi depending on device) because the actuator is "piloted" using air pressure assist. try attaching a different (or known good) solenoid and listen for electrical click when energizing. Then trace your wiring. Pay particular attention to the connectors and crimps, looking for loose connections.

+1. My first thought is that you have some sort of problem with your solenoid or wiring. Also, if you have another PCM, you might want to swap it in and check if there is any change.

[Jon Stratis]

I'd recommend a couple of approaches for this. The key is to narrow down where the problem is - you have code, roboRio, PCM, solenoids, cylinders, wiring, and tubing all involved. The notes below can help you figure out where the problem is, which makes fixing it a whole lot easier!

Programming - add some debug code to put an output every time you open or close the actuator. Hopefully, you'll see the appropriate output once each button click, but I have seen improper coding cause it to alternate rapidly with each button click, ending on a seemingly random state.

Mechanical - check out the solenoids themselves - do you hear them change position? do they have indicator lights to tell you when each side is open, and if so what are they doing?

Electrical - probe the outputs from the PCM. Do you see the voltage changing appropriately? Are the signal lights on the PCM showing that everything is OK? Does the PCM receive constant power? Is the voltage jumper in the correct location (24V solenoids have been known to appear like they're working with the LED's when driven by 12V, but not actually work reliably)?

[hectorcastillo]

All great suggestions! Thank you so much! I'll reply with an update after we try some of these out.

[ahartnet]

I know sometimes the solenoids can be wired in a place that's hard to see - but I believe most of them have little red lights for when they're actuated. If you see them turn red when the operator is trying to actuate - it might be that your cylinders (or is it a piston? I can't remember if the hashtag is #IACNAP or #IAPNAC...) is binding up/bent. A little bit of torque in the wrong direction may cause inconsistent failures.

[indieFan]

How big are your cylinders? How big are your air tanks, and how many do you have? What is the load on your cylinder when you try to fire it?

My team learned the hard way this season that a 2" bore, 24" stroke cylinder needed 5 black Clippard tanks to be able to deploy and retract the cylinder without requiring a recharge time.