Basics of Motors and Servos

Motors and servos are the primary actuators of an FTC robot. This guide covers how to program them in Java using the FTC Robot Controller app.

DC Motors

DC motors provide the power for your drivetrain and other mechanisms like arms or linear slides.

1. Initialization

Use the hardwareMap to initialize your motor.

DcMotor leftDrive = hardwareMap.get(DcMotor.class, "leftDrive");

2. Setting Direction

Depending on how your motor is oriented, you might need to reverse its direction.

leftDrive.setDirection(DcMotor.Direction.REVERSE);

3. Basic Control

You can control the motor’s power from -1.0 to 1.0.

leftDrive.setPower(0.5); // 50% power forward

4. Zero Power Behavior

Choose how the motor should behave when power is set to zero.

Brake: Resists movement (better for precision).
Float: Free to spin (better for some intakes).

leftDrive.setZeroPowerBehavior(DcMotor.ZeroPowerBehavior.BRAKE);

Servos

Servos are used for precision movements, like grippers or small rotations.

1. Standard Servos

Standard servos move to a specific position from 0.0 to 1.0.

Servo gripper = hardwareMap.get(Servo.class, "gripper");
gripper.setPosition(0.5); // Move to the middle position

2. Continuous Rotation (CR) Servos

CR servos rotate continuously and are controlled like a DC motor.

CRServo intake = hardwareMap.get(CRServo.class, "intake");
intake.setPower(1.0); // Full speed forward

Example Program: LinearOpMode

Here is a complete example of a LinearOpMode that initializes a motor and a servo, and allows you to control them.

package org.firstinspires.ftc.teamcode;

import com.qualcomm.robotcore.eventloop.opmode.LinearOpMode;
import com.qualcomm.robotcore.eventloop.opmode.TeleOp;
import com.qualcomm.robotcore.hardware.DcMotor;
import com.qualcomm.robotcore.hardware.Servo;

@TeleOp(name = "Motor and Servo Example", group = "Tutorial")
public class MotorServoExample extends LinearOpMode {

    private DcMotor armMotor;
    private Servo gripper;

    @Override
    public void runOpMode() {
        // 1. Initialize hardware
        armMotor = hardwareMap.get(DcMotor.class, "armMotor");
        gripper = hardwareMap.get(Servo.class, "gripper");

        // 2. Set directions and behaviors
        armMotor.setDirection(DcMotor.Direction.FORWARD);
        armMotor.setZeroPowerBehavior(DcMotor.ZeroPowerBehavior.BRAKE);

        telemetry.addData("Status", "Initialized");
        telemetry.update();

        // Wait for the game to start (driver presses START)
        waitForStart();

        // Run until the end of the match (driver presses STOP)
        while (opModeIsActive()) {
            
            // 3. Control Motor (e.g., using left stick Y)
            double motorPower = -gamepad1.left_stick_y; 
            armMotor.setPower(motorPower);

            // 4. Control Servo (e.g., using buttons)
            if (gamepad1.a) {
                gripper.setPosition(1.0); // Open
            } else if (gamepad1.b) {
                gripper.setPosition(0.0); // Closed
            }

            // 5. Send telemetry to the driver station
            telemetry.addData("Motor Power", motorPower);
            telemetry.addData("Servo Position", gripper.getPosition());
            telemetry.update();
        }
    }
}