Pneumatics Control

Overview

WPILib provides classes for controlling pneumatic systems, including solenoids for actuators and compressors for maintaining air pressure. This guide covers the Pneumatics Control Module (PCM) and Pneumatic Hub (PH).

Pneumatics Modules

WPILib supports two types of pneumatics modules:

CTRE PCM (Pneumatics Control Module) - Legacy CAN-based module
REV PH (Pneumatic Hub) - Current generation CAN-based module with additional features

Module Types

Java
C++

import edu.wpi.first.wpilibj.PneumaticsModuleType;

// Specify module type
PneumaticsModuleType.CTREPCM;  // CTRE PCM
PneumaticsModuleType.REVPH;    // REV Pneumatic Hub

#include <frc/PneumaticsModuleType.h>

// Specify module type
frc::PneumaticsModuleType::CTREPCM;  // CTRE PCM
frc::PneumaticsModuleType::REVPH;    // REV Pneumatic Hub

Solenoids

Source: wpilibj/src/main/java/edu/wpi/first/wpilibj/Solenoid.java:14 Solenoids are electrically controlled pneumatic valves for actuating cylinders.

Single Solenoid

Single-acting solenoids have one state (extend/retract) controlled by air pressure:

Java
C++

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

public class IntakeSubsystem {
  private Solenoid m_solenoid;

  public IntakeSubsystem() {
    // Solenoid on channel 0 of default REV PH module
    m_solenoid = new Solenoid(PneumaticsModuleType.REVPH, 0);
    
    // Or specify module ID
    m_solenoid = new Solenoid(1, PneumaticsModuleType.REVPH, 0);
  }

  public void extend() {
    m_solenoid.set(true);
  }

  public void retract() {
    m_solenoid.set(false);
  }

  public void toggle() {
    m_solenoid.toggle();
  }

  public boolean isExtended() {
    return m_solenoid.get();
  }
}

#include <frc/Solenoid.h>
#include <frc/PneumaticsModuleType.h>

class IntakeSubsystem {
 public:
  IntakeSubsystem()
    // Solenoid on channel 0 of default REV PH module
    : m_solenoid(frc::PneumaticsModuleType::REVPH, 0)
  {
    // Or specify module ID:
    // m_solenoid(1, frc::PneumaticsModuleType::REVPH, 0)
  }

  void Extend() {
    m_solenoid.Set(true);
  }

  void Retract() {
    m_solenoid.Set(false);
  }

  void Toggle() {
    m_solenoid.Toggle();
  }

  bool IsExtended() {
    return m_solenoid.Get();
  }

 private:
  frc::Solenoid m_solenoid;
};

Double Solenoid

Double-acting solenoids control both extend and retract with air pressure:

Java
C++

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

public class ClawSubsystem {
  private DoubleSolenoid m_solenoid;

  public ClawSubsystem() {
    // Forward channel 0, reverse channel 1
    m_solenoid = new DoubleSolenoid(
      PneumaticsModuleType.REVPH,
      0,  // Forward channel
      1   // Reverse channel
    );
  }

  public void open() {
    m_solenoid.set(Value.kForward);
  }

  public void close() {
    m_solenoid.set(Value.kReverse);
  }

  public void off() {
    // Turn off both solenoids (holds position)
    m_solenoid.set(Value.kOff);
  }

  public Value getPosition() {
    return m_solenoid.get();
  }

  public boolean isOpen() {
    return m_solenoid.get() == Value.kForward;
  }
}

#include <frc/DoubleSolenoid.h>
#include <frc/PneumaticsModuleType.h>

class ClawSubsystem {
 public:
  ClawSubsystem()
    // Forward channel 0, reverse channel 1
    : m_solenoid(frc::PneumaticsModuleType::REVPH, 0, 1)
  {}

  void Open() {
    m_solenoid.Set(frc::DoubleSolenoid::kForward);
  }

  void Close() {
    m_solenoid.Set(frc::DoubleSolenoid::kReverse);
  }

  void Off() {
    // Turn off both solenoids (holds position)
    m_solenoid.Set(frc::DoubleSolenoid::kOff);
  }

  frc::DoubleSolenoid::Value GetPosition() {
    return m_solenoid.Get();
  }

  bool IsOpen() {
    return m_solenoid.Get() == frc::DoubleSolenoid::kForward;
  }

 private:
  frc::DoubleSolenoid m_solenoid;
};

Pulse Control

Source: wpilibj/src/main/java/edu/wpi/first/wpilibj/Solenoid.java:133 Create timed pulses for quick actuations:

Java
C++

Solenoid solenoid = new Solenoid(PneumaticsModuleType.REVPH, 0);

// Set pulse duration (PCM: 0.01-2.55s, PH: 0.001-65.534s)
solenoid.setPulseDuration(0.5); // 500ms pulse

// Trigger the pulse
solenoid.startPulse();
// Solenoid will activate for 500ms then deactivate automatically

frc::Solenoid solenoid{frc::PneumaticsModuleType::REVPH, 0};

// Set pulse duration (PCM: 0.01-2.55s, PH: 0.001-65.534s)
solenoid.SetPulseDuration(0.5_s); // 500ms pulse

// Trigger the pulse
solenoid.StartPulse();
// Solenoid will activate for 500ms then deactivate automatically

Compressor

Source: wpilibj/src/main/java/edu/wpi/first/wpilibj/Compressor.java:14 The compressor automatically maintains air pressure. It typically doesn’t need to be controlled directly.

Basic Compressor Usage

Java
C++

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

public class RobotContainer {
  private Compressor m_compressor;

  public RobotContainer() {
    // Compressor on default module
    m_compressor = new Compressor(PneumaticsModuleType.REVPH);
    
    // Or specify module ID
    m_compressor = new Compressor(1, PneumaticsModuleType.REVPH);
    
    // Compressor automatically runs in closed loop by default
  }

  public void disableCompressor() {
    m_compressor.disable();
  }

  public void enableCompressor() {
    m_compressor.enableDigital();
  }

  public boolean isCompressorRunning() {
    return m_compressor.isEnabled();
  }
}

#include <frc/Compressor.h>
#include <frc/PneumaticsModuleType.h>

class RobotContainer {
 public:
  RobotContainer()
    // Compressor on default module
    : m_compressor(frc::PneumaticsModuleType::REVPH)
  {
    // Or specify module ID:
    // m_compressor(1, frc::PneumaticsModuleType::REVPH)
    
    // Compressor automatically runs in closed loop by default
  }

  void DisableCompressor() {
    m_compressor.Disable();
  }

  void EnableCompressor() {
    m_compressor.EnableDigital();
  }

  bool IsCompressorRunning() {
    return m_compressor.IsEnabled();
  }

 private:
  frc::Compressor m_compressor;
};

Compressor Control Modes

Source: wpilibj/src/main/java/edu/wpi/first/wpilibj/Compressor.java:129

Java
C++

Compressor compressor = new Compressor(PneumaticsModuleType.REVPH);

// Digital mode (using pressure switch)
compressor.enableDigital();

// Analog mode (REV PH only with analog pressure sensor)
compressor.enableAnalog(100, 120); // Min 100 PSI, Max 120 PSI

// Hybrid mode (REV PH only - uses both digital and analog)
compressor.enableHybrid(100, 120);

// Disable compressor
compressor.disable();

frc::Compressor compressor{frc::PneumaticsModuleType::REVPH};

// Digital mode (using pressure switch)
compressor.EnableDigital();

// Analog mode (REV PH only with analog pressure sensor)
compressor.EnableAnalog(100, 120); // Min 100 PSI, Max 120 PSI

// Hybrid mode (REV PH only - uses both digital and analog)
compressor.EnableHybrid(100, 120);

// Disable compressor
compressor.Disable();

Compressor Monitoring

Source: wpilibj/src/main/java/edu/wpi/first/wpilibj/Compressor.java:82

Java
C++

Compressor compressor = new Compressor(PneumaticsModuleType.REVPH);

// Check if compressor is running
boolean running = compressor.isEnabled();

// Check pressure switch state
boolean pressureLow = compressor.getPressureSwitchValue();

// Get current draw
double current = compressor.getCurrent();

// REV PH only - analog pressure sensor
double voltage = compressor.getAnalogVoltage();
double pressure = compressor.getPressure(); // PSI

frc::Compressor compressor{frc::PneumaticsModuleType::REVPH};

// Check if compressor is running
bool running = compressor.IsEnabled();

// Check pressure switch state
bool pressureLow = compressor.GetPressureSwitchValue();

// Get current draw
double current = compressor.GetCurrent();

// REV PH only - analog pressure sensor
double voltage = compressor.GetAnalogVoltage();
double pressure = compressor.GetPressure(); // PSI

Complete Pneumatics Example

Java
C++

import edu.wpi.first.wpilibj.TimedRobot;
import edu.wpi.first.wpilibj.DoubleSolenoid;
import edu.wpi.first.wpilibj.Solenoid;
import edu.wpi.first.wpilibj.Compressor;
import edu.wpi.first.wpilibj.Joystick;
import edu.wpi.first.wpilibj.PneumaticsModuleType;
import static edu.wpi.first.wpilibj.DoubleSolenoid.Value;

public class Robot extends TimedRobot {
  private Compressor m_compressor;
  private DoubleSolenoid m_clawSolenoid;
  private Solenoid m_armSolenoid;
  private Joystick m_joystick;

  @Override
  public void robotInit() {
    // Initialize pneumatics module
    m_compressor = new Compressor(PneumaticsModuleType.REVPH);
    
    // Claw - double solenoid on channels 0 and 1
    m_clawSolenoid = new DoubleSolenoid(
      PneumaticsModuleType.REVPH, 0, 1
    );
    
    // Arm - single solenoid on channel 2
    m_armSolenoid = new Solenoid(PneumaticsModuleType.REVPH, 2);
    
    m_joystick = new Joystick(0);
  }

  @Override
  public void teleopPeriodic() {
    // Button 1: Open claw
    if (m_joystick.getRawButtonPressed(1)) {
      m_clawSolenoid.set(Value.kForward);
    }
    
    // Button 2: Close claw
    if (m_joystick.getRawButtonPressed(2)) {
      m_clawSolenoid.set(Value.kReverse);
    }
    
    // Button 3: Toggle arm
    if (m_joystick.getRawButtonPressed(3)) {
      m_armSolenoid.toggle();
    }
    
    // Display compressor status
    if (m_compressor.isEnabled()) {
      System.out.println("Compressor running - Current: " + 
        m_compressor.getCurrent() + "A");
    }
  }

  @Override
  public void disabledInit() {
    // Retract all pneumatics when disabled
    m_clawSolenoid.set(Value.kOff);
    m_armSolenoid.set(false);
  }
}

#include <frc/TimedRobot.h>
#include <frc/DoubleSolenoid.h>
#include <frc/Solenoid.h>
#include <frc/Compressor.h>
#include <frc/Joystick.h>
#include <frc/PneumaticsModuleType.h>
#include <iostream>

class Robot : public frc::TimedRobot {
 public:
  void RobotInit() override {
    // Pneumatics components initialized in declarations
  }

  void TeleopPeriodic() override {
    // Button 1: Open claw
    if (m_joystick.GetRawButtonPressed(1)) {
      m_clawSolenoid.Set(frc::DoubleSolenoid::kForward);
    }
    
    // Button 2: Close claw
    if (m_joystick.GetRawButtonPressed(2)) {
      m_clawSolenoid.Set(frc::DoubleSolenoid::kReverse);
    }
    
    // Button 3: Toggle arm
    if (m_joystick.GetRawButtonPressed(3)) {
      m_armSolenoid.Toggle();
    }
    
    // Display compressor status
    if (m_compressor.IsEnabled()) {
      std::cout << "Compressor running - Current: "
                << m_compressor.GetCurrent() << "A" << std::endl;
    }
  }

  void DisabledInit() override {
    // Retract all pneumatics when disabled
    m_clawSolenoid.Set(frc::DoubleSolenoid::kOff);
    m_armSolenoid.Set(false);
  }

 private:
  frc::Compressor m_compressor{frc::PneumaticsModuleType::REVPH};
  frc::DoubleSolenoid m_clawSolenoid{frc::PneumaticsModuleType::REVPH, 0, 1};
  frc::Solenoid m_armSolenoid{frc::PneumaticsModuleType::REVPH, 2};
  frc::Joystick m_joystick{0};
};

Solenoid Safety

Source: wpilibj/src/main/java/edu/wpi/first/wpilibj/Solenoid.java:116

Check for Shorts

Java
C++

Solenoid solenoid = new Solenoid(PneumaticsModuleType.REVPH, 0);

// Check if solenoid is disabled due to short
if (solenoid.isDisabled()) {
  System.err.println("Solenoid is shorted and disabled!");
}

frc::Solenoid solenoid{frc::PneumaticsModuleType::REVPH, 0};

// Check if solenoid is disabled due to short
if (solenoid.IsDisabled()) {
  std::cerr << "Solenoid is shorted and disabled!" << std::endl;
}

Best Practices

One compressor per robot - Only instantiate one Compressor object
Use double solenoids for critical functions - They provide positive control in both directions
Turn off solenoids when disabled - Save air and reduce wear
Monitor compressor current - High current may indicate leaks or problems
Check for shorts - Use isDisabled() to detect solenoid shorts
Use pulse mode for quick actions - Saves air for brief actuations
Size your air storage - Ensure you have enough air for a full match

Troubleshooting

Solenoid Not Working

Check CAN connection to pneumatics module
Verify correct channel numbers
Check for shorts with isDisabled()
Ensure compressor is building pressure
Verify pneumatic connections

Compressor Not Running

Check pressure switch wiring
Verify compressor is enabled: enableDigital()
Check current draw (should be 0A when not running)
Ensure 12V power to compressor

Low Pressure

Check for air leaks in system
Verify pressure switch threshold
Check compressor current (should be high when running)
Inspect airline connections

Next Steps

Motor Control - Control motors
Sensors - Read sensor data
Vision - Process camera data

Getting Started

Core Concepts

Programming Guide

Simulation

Advanced Topics

Tools

Pneumatics Control

Overview

Pneumatics Modules

Module Types

Solenoids

Single Solenoid

Double Solenoid

Pulse Control

Compressor

Basic Compressor Usage

Compressor Control Modes

Compressor Monitoring

Complete Pneumatics Example

Solenoid Safety

Check for Shorts

Best Practices

Troubleshooting

Solenoid Not Working

Compressor Not Running

Low Pressure

Next Steps

Getting Started

Core Concepts

Programming Guide

Simulation

Advanced Topics

Tools

Documentation Index

​Overview

​Pneumatics Modules

​Module Types

​Solenoids

​Single Solenoid

​Double Solenoid

​Pulse Control

​Compressor

​Basic Compressor Usage

​Compressor Control Modes

​Compressor Monitoring

​Complete Pneumatics Example

​Solenoid Safety

​Check for Shorts

​Best Practices

​Troubleshooting

​Solenoid Not Working

​Compressor Not Running

​Low Pressure

​Next Steps

Overview

Pneumatics Modules

Module Types

Solenoids

Single Solenoid

Double Solenoid

Pulse Control

Compressor

Basic Compressor Usage

Compressor Control Modes

Compressor Monitoring

Complete Pneumatics Example

Solenoid Safety

Check for Shorts

Best Practices

Troubleshooting

Solenoid Not Working

Compressor Not Running

Low Pressure

Next Steps