Programming Servo Basics

Programming Position Movements

Add the line test_servo.setPosition(1); to the OpMode while loop.

        while (opModeIsActive()) {
            test_servo.setPosition(1);
            telemetry.addData("Status", "Running");
            telemetry.update();
            
        }

Select Build Everything to build the code.

Quick Check!

Let's give our program a try. Take a moment to observe what happens.

When running our program for the first time, we should have seen our servo move itself to position 1 and maintain that position. But what happens if we run it again? Does the servo move?

Running our program a second time

Likely, on a second run our servo did not move since it is already at the correct position. Now check what happens if you first manually rotate the servo while the robot is disabled. Once the code is activated again by pressing play we should see it move again!

Note: Servos are designed to maintain their position so long as the robot's program is enabled. Trying to forcibly move the servo while ON may damage it and is not recommended.

If your servo did not move as expected, double check your wiring and port are correct compared to your configuration.

Resetting Back to Zero

The intent of thetest_servo.setPosition();is to set the position of the servo. If the servo is already in the set position when a code is run, it will not change positions. Lets try adding the line test_servo.setPosition(0).

In this case, we do not want our servo to reset to 0 every time our code repeats. Because of this where do you think we would add this line?

Recall when we discussed the different sections of our OpMode during Programming Essentials. Since we only want our servo to reset ONCE we will request it do so during the initialization process when the code is first activated, but before play is pressed.

public void runOpMode() {
        control_Hub = hardwareMap.get(Blinker.class, "Control Hub");
        arm = hardwareMap.get(DcMotor.class, "arm");
        leftmotor = hardwareMap.get(DcMotor.class, "leftmotor");
        rightmotor = hardwareMap.get(DcMotor.class, "rightmotor");
        test_motor = hardwareMap.get(DcMotor.class, "test_motor");
        test_servo = hardwareMap.get(Servo.class, "test_servo");
        test_touch = hardwareMap.get(TouchSensor.class, "test_touch");
        
        test_servo.setPosition(0);

        telemetry.addData("Status", "Initialized");
        telemetry.update();
        // Wait for the game to start (driver presses PLAY)
        waitForStart();

        // run until the end of the match (driver presses STOP)
        while (opModeIsActive()) {
            test_servo.setPosition(1);
            telemetry.addData("Status", "Running");
            telemetry.update();

        }
    }
}

Try running this op mode on the test bed and consider the following question:

• What is different from the previous run?

In many applications starting the servo in a known state, like at position zero, is beneficial to the operation of a mechanism. Setting the servo to the known state in the initialization ensures it is in the correct position when the OpMode runs.

Take a moment to think about where setting the servo to a known state during initialization may be helpful before moving to the next section!