Pneumatics

Pneumatics are air pressure powered pistons that provide explosive and strong power. We control our pneumatics using valves called "solenoids", which determine the direction that air flows. These valves can be programmed to provide mechanical motor, like motors and servos. We have used pneumatics in the past (on Janus for example), but have mainly stopped using them.

What comes with Pneumatics?

There are really 3 main objects that come with the pneumatics package, the Pneumatics Control Module (PCM), the Compressor, and the Solenoid. There are other things that exist, but in the code those are really the only things you need to worry about. The PCM is the hub, both the solenoid and compressor both plug into the PCM and tells them what they should be doing. The solenoid is the actual piston that moves back and forth, but it requires air to function. Lastly, the compressor is the object that actually makes the air pressure. It is loud, but do not be alarmed, it will shut off if wired correctly.

How do I program them?

First of all, let's initialize a solenoid. The compressor and PCM do not need any initialization unless you want to do something with them

import edu.wpi.first.wpilibj.DoubleSolenoid;

public class Pneumatics extends SubsystemBase {
    
    private DoubleSolenoid solenoid;
    public pneumatics(){
    
    }
}

Wow. That was so fun guys, we made a solenoid. I will note that a DoubleSolenoid is different from a regular Solenoid. A regular Solenoid only has 1 channel to move in, whereas a DoubleSolenoid has 2. Usually we use a DoubleSolenoid because we like to have the capability to move in both directions.

To program a DoubleSolenoid, you need to know that they have 3 states: Forward, Reverse, and Off. Forward is the state of the solenoid that pushes outward, Reverse is the state that retracts inward and Off is the state that stops the DoubleSolenoid, making it do nothing.

Forward and Reverse have their own numbered channels that you can assign them to. They have to be wired into the solenoid, but each port has a number so you can figure out with port/number is associated with the Forward and Reverse states of the solenoid. Now let's actually give the solenoid some numbers. They take 3 values: The manufacturer of the solenoid, the forward channel port, and the reverse channel port.

import edu.wpi.first.wpilibj.DoubleSolenoid;
import edu.wpi.first.wpilibj.PneumaticsModuleType;

public class Pneumatics extends SubsystemBase {
    
    private DoubleSolenoid solenoid;
    public pneumatics(){
        //For the purposes of this example, the forward channel is 0 and the reverse channel is 1
        solenoid = new DoubleSolenoid(PneumaticsModuleType.CTREPCM, 0, 1);
    }
}

Now that we have a solenoid, let's make some methods to go with it so we can call it in a command. We are going to need kForward and kReverse values. These values tell the solenoid to activate a certain method.

import edu.wpi.first.wpilibj.DoubleSolenoid;
import edu.wpi.first.wpilibj.PneumaticsModuleType;
import edu.wpi.first.wpilibj.DoubleSolenoid.Value;

public class Pneumatics extends SubsystemBase {
    
    private DoubleSolenoid solenoid;
    public pneumatics(){
        //For the purposes of this example, the forward channel is 0 and the reverse channel is 1
        solenoid = new DoubleSolenoid(PneumaticsModuleType.CTREPCM, 0, 1);
    }

    public void setInwards{
        //this method will make the solenoid retract
        solenoid.set(Value.kReverse);
    }

    public void setOutwards{
        //this method will make the solenoid retract
        solenoid.set(Value.kForward);
    }

//Techically we have all the other calls that the SubsystemBase comes with, but these are really all we are going to worry about
}

That's pretty much it! If you want to call them in a command, you should refer to command based programming. Good luck with these Pneumatics!