Lesson 8.1: Using setPower() to Control Motor Speed

Technical Context

The Robot Controller manages motor output by sending pulse-width modulation (PWM) signals to the Expansion Hub or Control Hub. Sending power levels allows for variable speed control; however, providing too much power to a stalled mechanism, such as an arm pressed against a hard stop, can lead to motor burnout or stripped gears from sustained high-current draw.

What setPower() Is Really Doing

The setPower(double power) method is the primary tool for commanding hardware motion. It accepts a double parameter ranging from -1.0 (full reverse) to 1.0 (full forward), where 0.0 signifies a stop command.

Important behaviors to understand:

Values above 1.0 or below -1.0 are automatically clamped by the SDK. Passing 1.5 is treated as 1.0.
The method does not directly control velocity. It controls the PWM duty cycle (effectively the voltage fraction). Actual speed depends on battery voltage, load, and the motor's run mode.
The command is held until another setPower() call overrides it. If you never call setPower(0), the motor keeps running after your code finishes that loop cycle.

Official references

SDK API for motor methods: FTC RobotCore Javadocs
REV hardware and control-system context: REV DUO Control System

Common robot failure: motors hum but do not move

That is often a stalled mechanism, not a code problem. Stop testing at high power, lift the robot or remove the load, check gear mesh and hard stops, then re-test at low power while watching current draw if your tooling shows it.

In TeleOp (OpMode)

When a driver is commanding the motor live, setPower() belongs in loop(). The SDK refreshes the gamepad values between loop cycles, so this is the correct place to read stick or trigger input.

package org.firstinspires.ftc.teamcode;

import com.qualcomm.robotcore.eventloop.opmode.OpMode;
import com.qualcomm.robotcore.eventloop.opmode.TeleOp;
import com.qualcomm.robotcore.hardware.DcMotor;

@TeleOp(name="SetPower_Demo")
public class SetPowerDemo extends OpMode {

    private DcMotor intake;

    @Override
    public void init() {
        intake = hardwareMap.get(DcMotor.class, "intake");
        intake.setMode(DcMotor.RunMode.RUN_WITHOUT_ENCODER);
        intake.setPower(0); // Safe known state before match starts
        telemetry.addData("Status", "Intake ready");
    }

    @Override
    public void loop() {
        // Capture joystick input and pass it directly to the motor
        double powerRequest = -gamepad1.left_stick_y;
        intake.setPower(powerRequest);

        telemetry.addData("Power Sent", powerRequest);
    }
}

In Autonomous (LinearOpMode)

In autonomous, motor power is part of a planned sequence. No gamepad input is read. Instead, the program maps the hardware, waits for the start signal, runs the step, and then stops the motor.

package org.firstinspires.ftc.teamcode;

import com.qualcomm.robotcore.eventloop.opmode.LinearOpMode;
import com.qualcomm.robotcore.eventloop.opmode.Autonomous;
import com.qualcomm.robotcore.hardware.DcMotor;

@Autonomous(name="SetPower_Auto_Demo")
public class SetPowerAutoDemo extends LinearOpMode {

    private DcMotor driveMotor;

    @Override
    public void runOpMode() {
        driveMotor = hardwareMap.get(DcMotor.class, "drive_motor");
        driveMotor.setMode(DcMotor.RunMode.RUN_WITHOUT_ENCODER);
        driveMotor.setPower(0.0);

        waitForStart();

        driveMotor.setPower(0.5);
        sleep(1500);

        driveMotor.setPower(0.0);
    }
}

Fill-in-the-Blank Practice

The setPower() method accepts a __________ data type as its parameter.
To command a motor to rotate at half-speed in the reverse direction, you would pass the value __________ to the method.
If the motor power is set to 1.2 in code, the SDK will clamp the value and treat it as __________.

Show answers

double
-0.5
1.0

Simulator Challenge

Use the simulator below to practice intake power control with lesson-specific starter code and live trigger input.

Telemark Unit 8.1 Simulator

Loads the lesson-specific Telemark motor challenge with starter code instead of a completed solution.

Includes live hardware feedback, telemetry checks, and gamepad input for each motor-control concept.

Best for practicing power, direction, braking, stopping behavior, and limit-switch safety in context.

Connects to the mechanical track

Power is not speed. What a given power command produces at the mechanism depends on the reduction and the load the build team chose.

See Lesson 6.1: Reading Motor Curves, Free Speed, and Stall Torque.

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Technical Context​

What setPower() Is Really Doing​

In TeleOp (OpMode)​

In Autonomous (LinearOpMode)​

Fill-in-the-Blank Practice​

Simulator Challenge​