Lesson 9.4: Using CRServos for Intake-Style Mechanisms

---

Technical Context

Continuous Rotation (CR) servos are used for high-speed intakes or spinning mechanisms where positional precision is not required. They provide a compact, lighter alternative to a full DC motor when you need continuous rotation but don't have a free motor port: or when the mechanism is small enough that a servo's current draw is acceptable.

---

How CRServos Differ from Standard Servos

Unlike standard positional servos, a CRServo does not have a target angle. It has no concept of "position": instead, it spins continuously at a speed determined by its power value. For this reason, the SDK exposes it through the setPower() method, exactly like a DcMotor:

• 1.0: full speed forward
• 0.0: stopped
• -1.0: full speed reverse

Because it uses setPower() instead of setPosition(), you must also remember that a CRServo will not hold any position when set to 0.0: it simply stops spinning. There is no equivalent of ZeroPowerBehavior.BRAKE for a CR servo.

Look up the device with CRServo.class, not Servo.class. The generic hardwareMap.get() call may still compile with the wrong requested type, but the Robot Controller cannot return a positional Servo interface for hardware configured as a CR servo and will report a runtime configuration or type error.

---

Annotated Code

package org.firstinspires.ftc.teamcode;

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

@TeleOp(name="CRServo_Demo")
public class CRServoDemo extends OpMode {

    // Must declare as CRServo: not Servo
    private CRServo intake;

    @Override
    public void init() {
        // Must get as CRServo.class from the hardwareMap
        intake = hardwareMap.get(CRServo.class, "intake_servo");
        intake.setPower(0);
        telemetry.addData("CR Intake", "Ready");
    }

    @Override
    public void loop() {
        // Trigger directly drives the servo speed: 0.0 to 1.0
        intake.setPower(gamepad1.right_trigger);

        // Left trigger runs it in reverse for ejecting
        if (gamepad1.left_trigger > 0.1) {
            intake.setPower(-gamepad1.left_trigger);
        }

        telemetry.addData("Intake Power", intake.getPower());
    }
}

---

Fill-in-the-Blank Practice

1. A CR Servo is commanded using the __________ method instead of setPosition().
2. To stop a CR Servo, the power must be set to __________.
3. If a CR Servo rotates the wrong direction for an intake, you can invoke the __________ method to flip it without changing your power logic.

Show answers

1. setPower()
2. 0.0
3. setDirection()

---

Simulator Challenge

Use the simulator below to practice mapping a CRServo, running it forward with B, reversing with X, and stopping it when neither button is held.

1.Complete the codeWork in fullscreen when you need more room for the editor and visualizer. Where file tabs are available, hover over the tab strip and choose + to create a file or reuse saved code.

2.Run the lifecyclePress Init, then Start. Use the available gamepad or scene controls.

3.Debug the behaviorCheck telemetry, motion, requirements, and hints before opening the answer.

Telemark Unit 9.4 Simulator

Loads the lesson-specific Telemark servo challenge with starter code for students to complete.

Includes live mechanism feedback, telemetry checks, and gamepad input for each servo-control concept.

Ready to move on?

Only mark complete if you genuinely understand the material. Your progress will be saved in this browser.

Stuck on this lesson?

Ask about anything on this page. It can see which lesson you have open and which part you are reading.