Chief Delphi - Exhaust in Solenoids

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Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Pneumatics (http://www.chiefdelphi.com/forums/forumdisplay.php?f=54)

- - Exhaust in Solenoids (http://www.chiefdelphi.com/forums/showthread.php?t=152523)

FRC Team CC

03-12-2016 21:38

Exhaust in Solenoids

Hey Teams!

Is there any way to block the exhaust holes on the sides of the solenoids (some screw or contraption)? We are trying to program a piston to move out and in and found the exhaust hole leaking out air.

Also, if we want to control both the A and the B holes, do we need a double solenoid? Or can we make do with a single solenoid?

Sorry about these simple questions; we are a new team and are trying to figure out all of these new components. We greatly appreciate your help.

Thanks,
Charging Champions

Mark McLeod

03-12-2016 21:59

Re: Exhaust in Solenoids

If you plug the exhaust ports, then the solenoid will cease to work. It only works by letting air out of the cylinder through the exhaust ports.
If air is leaking, then it is for other reasons.

Both double and single solenoids control all ports.
The difference between the two types is that a single solenoid has a home position it always returns to when power is cut or the robot is Disabled, while the double solenoid stays in the last position you put it when power is cut or the robot is Disabled.

What model solenoid are you trying to use?

ctt956

03-12-2016 22:59

Re: Exhaust in Solenoids

To maybe fix the leak, try checking the ends of the air tubes, and see if they're cut straight. If they've been cut at an angle, they can leak. Cutting them straight should fix it. Note that this may not be the issue, but it's a simple thing to check before you disassemble the whole pneumatics system. Just make sure to vent any air in the tank before working on anything! ::safety::

headlight

03-12-2016 23:26

Re: Exhaust in Solenoids

A single solenoid should be enough to control both the A and B ports. The important thing is that it is a 4/5 port solenoid.

If there is air leaking out of the exhaust port it is usually either an internal leak in the seal of the air cylinder or a leak in the gasket between the solenoid and the manifold block (if you are using a manifold setup).

FRC Team CC

04-12-2016 00:06

Re: Exhaust in Solenoids

1 Attachment(s)

Quote:

Originally Posted by Mark McLeod (Post 1619177)

What model solenoid are you trying to use?

We are using the solenoids from this link: http://www.wcproducts.net/pneumatics.

Quote:

Originally Posted by Mark McLeod (Post 1619177)

If you plug the exhaust ports, then the solenoid will cease to work. It only works by letting air out of the cylinder through the exhaust ports.

So we are trying to control a piston that is plugged in to one of the A ports (the solenoid is connected to port 0). It seems that if we don't block off the exhaust, the air tanks don't build up in pressure as all of the air leaks out of the solenoid exhaust. In our current setup, we have our compressor connected to our compressor and a regulator. The regulator is connected to the solenoids. Is something wrong with our setup that would cause this issue?

Quote:

Originally Posted by ctt956 (Post 1619181)

Our air tubes seem to be cut straight, so that shouldn't be an issue, but thanks for letting us know for future reference!

Quote:

Originally Posted by headlight (Post 1619183)

Our solenoids are 4 port solenoids. We have a picture attached for what our setup looks like.

Thanks,
Charging Champions

Owen Busler

04-12-2016 00:43

Re: Exhaust in Solenoids

Arent pneumatics not allowed in ftc?

headlight

04-12-2016 03:59

Re: Exhaust in Solenoids

Quote:

Originally Posted by FTC Team CC (Post 1619190)

We are using the solenoids from this link: http://www.wcproducts.net/pneumatics.

...

Our solenoids are 4 port solenoids. We have a picture attached for what our setup looks like.

Thanks,
Charging Champions

Looks good. We use that exact same setup on our FRC robot. How bad is the leak? I'm curious about what you have plugged into the B ports on the left side, and why there aren't corresponding tubes in the A ports. Also, are you feeding air into the threaded "P" port on the side of the manifold not shown in that picture?

Can you tell which exhaust the air is leaking out of? EA or EB? If you manually trigger each solenoid, does it switch which port it is leaking out of? This would be a way to narrow down which part of the circuit has the problem.

If I were trying to fix this I would unscrew each solenoid and wipe off the gasket and the mounting surface, then carefully re-mount them, alternately tightening the two screws to reduce the chance of the solenoid sitting crooked. We have also had the rare instance where the solenoid was leaking internally.

DaveL

04-12-2016 06:17

Re: Exhaust in Solenoids

Quote:

Originally Posted by Mark McLeod (Post 1619177)

If you plug the exhaust ports, then the solenoid will cease to work. It only works by letting air out of the cylinder through the exhaust ports.

I agree with what Mark has said if one input port is distributing air to 2 output ports with both output ports sending air to a cylinder (one for push and one for pull).

If you have constructed a system where no pneumatic air is used to retract the piston, then you will need a stopper on one valve port.

For example: if only one port on the cylinder is connected to a valve, when that valve is diverting air to the other output port (say port 4), all connected air stores will be dumped. In this case adding a stopper plug to port 4 and making that port the "home" port will stop air from exiting when the system is being pressurized.

This kind of set up can be used to save air when the cylinder has a return spring or other method of returning the piston to its starting position.

A stopper can be made with a round urethane belt (tube) or use a tee fitting and connect 2 of the openings together with one tube to make a dead end, then connect the tee to your valve port.

Dave

FRC Team CC

04-12-2016 16:32

Re: Exhaust in Solenoids

Quote:

Originally Posted by Owen Busler (Post 1619195)

Arent pneumatics not allowed in ftc?

We are an FRC team. Its just that the account that we are using right now is the one we used last year when we were an FTC team :] . Sorry about the confusion.

Quote:

Originally Posted by headlight (Post 1619208)

I'm not exactly sure if there is a leak. It seems that we are only able to control the A ports on the solenoid. We are not able to control the B ports, so the air keeps leaking out of there and makes the A ports useless.

Here is our code. Let us know where we are making a mistake:

Code:

package org.usfirst.frc.team6560.robot;



import edu.wpi.first.wpilibj.Compressor;

import edu.wpi.first.wpilibj.IterativeRobot;

import edu.wpi.first.wpilibj.Timer;



import edu.wpi.first.wpilibj.*;

import edu.wpi.first.wpilibj.smartdashboard.SendableChooser;

import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;



/**

* The VM is configured to automatically run this class, and to call the

* functions corresponding to each mode, as described in the IterativeRobot

* documentation. If you change the name of this class or the package after

* creating this project, you must also update the manifest file in the resource

* directory.

*/

public class Robot extends IterativeRobot {

   static final long TIME = 10000; // ms

   static final int SAMPLE_COMPRESSOR = 0;



   Compressor sample_compressor;

   long m_autoStartTime;

   long m_autoStartTime1;

   long m_autoStartTime2;



   Solenoid solenoid_0;

   Solenoid solenoid_1;

   Solenoid solenoid_2;

   Solenoid solenoid_3;



   public void robotInit() {

       sample_compressor = new Compressor(SAMPLE_COMPRESSOR);

       solenoid_0 = new Solenoid(0);

       solenoid_1 = new Solenoid(1);

       solenoid_2 = new Solenoid(2);

       solenoid_3 = new Solenoid(3);

   }



   public void autonomousInit() {

       m_autoStartTime = System.currentTimeMillis();



   }



   public void autonomousPeriodic() {

           

           solenoid_0.set(true);

           solenoid_1.set(true);

           solenoid_2.set(true);

           solenoid_3.set(true);

       

   }



}

Thanks,
Charging Champions

Mark McLeod

04-12-2016 16:36

Re: Exhaust in Solenoids

For a single solenoid
if
solenoid_0.set(true); - seems to be activating your A port (B port off)
then
solenoid_0.set(false); - would switch to activate the B port (A port off)

P.S.
You want to watch what the individual indicator lights are doing on the Pneumatic Control Module (PCM).
If your software works correctly, the status light for each solenoid will be (could be the reverse of this):

lit=port A deactivated/port B activated
unlit= port A activated/port B deactivated

And you should be able to see them change as your code changes the solenoid from true to false to true.

Once you are sure your code is doing what it is supposed to be doing, then look at the plumbing on the manifold. But make sure your code is operating correctly first.

headlight

04-12-2016 16:56

Re: Exhaust in Solenoids

Each solenoid only has two states.

State 1: Port A is connected to supply Pressure (P), Port B is connected to Exhaust B (EB).

State 2: Port B is connected to supply Pressure (P), Port A is connected to Exhaust A (EA).

With the solenoids you are using, one of these states will be the default. If you are using air cylinders that are powered in both directions by air you should have tubes running to both A and B ports. If you are using air cylinders that are not powered by air in both directions, then you should plug the unused port. I'm personally a fan of these plugs, but some people like these better. You can also get them from here.

FRC Team CC

04-12-2016 17:24

Re: Exhaust in Solenoids

Quote:

Originally Posted by Mark McLeod (Post 1619251)

lit=port A deactivated/port B activated
unlit= port A activated/port B deactivated

Does activated mean open or closed valve?

Mark McLeod

04-12-2016 17:49

Re: Exhaust in Solenoids

Quote:

Originally Posted by FTC Team CC (Post 1619256)

Does activated mean open or closed valve?

You can think of the one solenoid as two valves that always do the opposite of each other, or as a single value with two positions.
In one position (deactivated), it is trying to fill one end of a cylinder (let's call it cylinder end A) by sending pressurized air out port A, simultaneously it is trying to empty the other end of the cylinder (let's call it cylinder end B) by releasing the other pressurized end out an exhaust port.

In the opposite position (activated), it reverses the cylinder action by sending pressurized air through port B to fill cylinder end B, while simultaneously emptying cylinder end A by connecting port A to an exhaust port.

FRC Team CC

04-12-2016 18:03

Re: Exhaust in Solenoids

Quote:

Originally Posted by Mark McLeod (Post 1619261)

We tested it out, and we have no control over any of the valves, even though we used the same code mentioned above and the solenoids are lighting up...

FRC Team CC

04-12-2016 18:08

Re: Exhaust in Solenoids

Do we need to manually lock the solenoids to property use it (the lock mechanism is the blue screw)?

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