Need help programming double solenoids!

[Zalmay]

I am a member of team 4528, the Automatons. I need help figuring out why my pneumatics code for double solenoids won't work.

package org.usfirst.frc.team4528.robot;

import edu.wpi.first.wpilibj.Compressor;		//Pneumatics
import edu.wpi.first.wpilibj.Joystick;			//DriveTrain
import edu.wpi.first.wpilibj.RobotDrive;		//DriveTrain
import edu.wpi.first.wpilibj.SampleRobot;		
import edu.wpi.first.wpilibj.DoubleSolenoid;	        //Pneumatics
import edu.wpi.first.wpilibj.Timer;				
import edu.wpi.first.wpilibj.Victor;			//Motors

public class Robot15 extends SampleRobot
{
	Victor frontLeft;
	Victor rearLeft;
	Victor frontRight;
	Victor rearRight;
	Victor pully;

	RobotDrive myRobot;
	XBoxJoystick gamestick;

	DoubleSolenoid pistonArm;
	Compressor compressor;

	public void Robot()
	{
		
		frontLeft = new Victor(1);	//Set to appropriate PWM port
		rearLeft = new Victor(2);	//Set to appropriate PWM port
		frontRight = new Victor(3);	//Set to appropriate PWM port
		rearRight = new Victor(4);	//Set to appropriate PWM port
		pully = new Victor(5);		//Set to appropriate PWM port

		pistonArm = new DoubleSolenoid(7, 6);
		compressor = new Compressor();	//Set to null

		gamestick = new XBoxJoystick(0);	//Set to appropriate victors
		myRobot = new RobotDrive(frontLeft, rearLeft, frontRight, rearRight);
	}

	public void useElavator()
	{
		if(gamestick.getRightZ() > 0)
		{
			pully.set(gamestick.getRightZ());	//Sets value of trigger to speed of motor
		}
		else if(gamestick.getLeftZ() > 0)
		{
			pully.set(-gamestick.getLeftZ());	//Sets value of trigger to speed of motor
		}
		else
		{
			pully.set(0.0);				//Doesn't run if trigger not pressed
		}
	}
	
	public void moveArm()
	{
		compressor.start();
		compressor.setClosedLoopControl(true);	//Lets PCM handle the automatic turning on and off of compressor once pressure hits 120 psi
		
		if(gamestick.getAButton() == true)
		{
			pistonArm.set(DoubleSolenoid.Value.kForward);	//Pushes piston whenever 'A' button is pressed
			System.out.println("'A' button is pressed: Piston moves forward");
		}
		else if(gamestick.getBButton() == true)
		{
			pistonArm.set(DoubleSolenoid.Value.kReverse); //Reverses piston  whenever 'B' button is pressed
	
			System.out.println("'B' button is pressed: Piston moves backward");
		}
		else
		{
			pistonArm.set(DoubleSolenoid.Value.kOff);		//Disables piston
		}
	}

	public void operatorControl()
	{
		myRobot.setSafetyEnabled(false);
		while(isOperatorControl() && isEnabled())
		{
			//squaredInputs help to lower speed value of analog sticks at lower values
			myRobot.tankDrive(gamestick.getLeftY(), gamestick.getRightY(), true);
			Timer.delay(0.005);
			useElavator();
			Timer.delay(0.005);
			moveArm();
		}
	}
}

We know that the problem is not with the hardware itself since we are able to use the pistons manually via the solenoid. It is most likely a problem with the code, specifically the moveArm() method.

[Team3266Spencer]

Please explain what you mean by "won't work."

[CreativeName55]

The two possibilities I see are the setting it to off, as I have no idea what that does (we've always set it to a position and left it there until we set it the other way), or if the solenoid's not receiving the right voltage. Some solenoid's are meant to receive 12V, some 24V. If they're wired wrong, they don't work

[GeeTwo]

We're not using pneumatics this year, and I was not programming last year, so maybe this won't make sense with the 2015 setup. However, I remember that our lead programmer last year spoke of "strobing" the double solenoids when the buttons were pressed rather than "setting" them. I believe that this is because (physical) double solenoid valves only need to be supplied with current for a fraction of a second; when no voltage is applied to either side, they physically maintain their state through the position of the internal piston.