Moving a Motor with motor.set()

1 Why this matters

Whole robots have been driven with nothing but this one method. The cardboard “kitbot” that many rookies build? Programmed entirely with motor.set(). Once you can spin a motor on command, you can run an intake, a feeder, a shooter wheel, or a climber. Any mechanism whose job is to turn on until something happens.

2 The signal path

Before code, picture where your command actually goes. When you call motor.set(0.7), the instruction travels a physical path through the robot:

The SparkMax is a motor controller. It takes your software command and delivers the right power to the Neo motor plugged into it. Every controller on the CAN bus has a unique CAN ID you set in the REV Hardware Client, so your code can say “motor number 2, specifically.”

3 Creating a motor object

Remember from Phase 1 that creating an object means instantiating a class. A motor is no different. A SparkMax object needs two things: the CAN ID you assigned it, and the motor type, which is brushless for a Neo.

import com.revrobotics.spark.SparkMax;
import com.revrobotics.spark.SparkLowLevel.MotorType;

// id = the CAN ID you set in the REV Hardware Client
// kBrushless = a Neo (brushless) motor
SparkMax motor1 = new SparkMax(2, MotorType.kBrushless);

4 motor.set() and percent output

Now the star of the show. motor.set(x) takes a percent output from -1.0 to 1.0:

• 1.0 = 100% power in one direction
• -1.0 = 100% power in the other direction
• 0.0 = stop

Which physical direction counts as positive? You will not know until you test, so run it slowly first and watch which way the mechanism moves.

motor1.set(0.7);    // run at 70% power, one direction
motor1.set(0.0);    // stop
motor1.set(-0.5);   // run at 50% power, the other direction

5 Staying under 80%

So set(0.7) is a healthy go value for many mechanisms. set(0.95) is asking for smoke. When a mechanism needs more force, teams add a second motor rather than redline one.

6 Practice challenges

This is robot code and it needs a real robot and WPILib to run, so these challenges test your understanding instead of a live compiler.

motor1.set(-0.5);

SparkMax intake = new SparkMax(, MotorType.);
intake.set();

7 Common mistakes

import com.revrobotics.spark.SparkMax;
import com.revrobotics.spark.SparkLowLevel.MotorType;

public class Intake {
    // 1) create the motor on CAN ID 2, brushless
    private final SparkMax roller = /* TODO */;

    // 2) pull a game piece IN at a safe 70%
    public void intake() {
        // TODO
    }

    // 3) stop the roller
    public void stop() {
        // TODO
    }
}

import com.revrobotics.spark.SparkMax;
import com.revrobotics.spark.SparkLowLevel.MotorType;

public class Intake {
    private final SparkMax roller = new SparkMax(2, MotorType.kBrushless);

    public void intake() {
        roller.set(0.7);   // pull the game piece in
    }

    public void stop() {
        roller.set(0);     // stop the roller
    }

    // Bonus: reverse to spit the piece out
    public void outtake() {
        roller.set(-0.5);
    }
}