Programming Solenoids and the Compressor in WPILib

Telling WPILib Which Module You Have#

Every pneumatics class takes a PneumaticsModuleType — REVPH for the REV Pneumatic Hub or CTREPCM for the CTRE PCM. WPILib's Solenoid, DoubleSolenoid, and Compressor classes do the rest; the controller hardware handles closed-loop compressor control automatically.

Single Solenoid#

A Solenoid controls one channel. Construct it with the module type and channel, then turn it on or off:

Solenoid exampleSolenoid = new Solenoid(PneumaticsModuleType.REVPH, 0);
exampleSolenoid.set(true);   // energize
exampleSolenoid.set(false);  // de-energize (springs back)
exampleSolenoid.toggle();    // flip current state

Double Solenoid#

A DoubleSolenoid takes a forward channel and a reverse channel, and is set to one of three states: kForward, kReverse, or kOff:

DoubleSolenoid exampleDouble =
    new DoubleSolenoid(PneumaticsModuleType.CTREPCM, 1, 2);
exampleDouble.set(DoubleSolenoid.Value.kForward);
exampleDouble.set(DoubleSolenoid.Value.kReverse);
exampleDouble.set(DoubleSolenoid.Value.kOff);  // both off, holds last air state

A DoubleSolenoid defaults to kOff, so you must set() it before toggle() will work. You can also pass an explicit CAN ID, e.g. new DoubleSolenoid(9, PneumaticsModuleType.REVPH, 4, 5).

Running the Compressor#

The Compressor class manages automatic compressor control. There are three modes:

Compressor compressor = new Compressor(PneumaticsModuleType.REVPH);

// 1) Digital: run until the pressure switch reports full. Works on PH and PCM.
compressor.enableDigital();

// 2) Analog: PH only - run while pressure is between min and max (psi)
compressor.enableAnalog(70, 120);

// 3) Hybrid: PH only - analog range AND the digital switch agree it is not full
compressor.enableHybrid(70, 120);

compressor.disable();                  // stop automatic control
double psi = compressor.getPressure(); // live pressure (PH analog only)

Closed-loop (digital) control is enabled by default when a Compressor is constructed, so simply creating the object usually starts the compressor running under pressure-switch control once the robot is enabled.

Best Practices#

• Put solenoid objects in a subsystem and expose methods like extend() / retract() rather than calling set() from all over your code.
• For double solenoids, decide a sensible disabled/init state (kForward, kReverse, or kOff).
• getPressure() returns valid data only with the REV analog sensor on a PH; on a PCM use the digital switch state instead.
• Test on the bench with the REV Hardware Client before relying on robot code.