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Lesson 8.3: Using ZeroPowerBehavior.BRAKE to Hold Position Better

Technical Context​

When power is set to 0.0, a heavy mechanism — like a lift or a high-momentum drivetrain — may continue to move due to gravity or inertia. In FTC, this is critical for high-reach scoring assemblies: without software braking, a lift will "drift" downward as soon as the driver releases the joystick, potentially dropping a game element or crashing into the robot frame.

Why BRAKE and FLOAT Feel Different on a Real Robot​

The setZeroPowerBehavior() method defines how the Expansion Hub motor controller handles a zero-power state. There are two options:

  • BRAKE — electronically shorts the motor's terminals together, creating a resistive force that opposes any external motion. The motor actively resists gravity and inertia. This draws a small holding current.
  • FLOAT (the default) — disconnects the motor terminals, allowing the motor shaft to spin freely until mechanical friction brings it to rest. This is also called "coast."

The behavior is set on the hardware controller, not just in software — the Control Hub physically changes the circuit configuration of the motor port. This means BRAKE still holds its position even during brief communication interruptions.

Set ZeroPowerBehavior in init() immediately after mapping, so the hardware is always in the correct state before the match begins.

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.DcMotor;

@TeleOp(name="Brake_Demo")
public class BrakeDemo extends OpMode {

    private DcMotor armMotor;

    @Override
    public void init() {
        armMotor = hardwareMap.get(DcMotor.class, "arm_motor");

        // Configure the motor to resist gravity when stopped
        armMotor.setZeroPowerBehavior(DcMotor.ZeroPowerBehavior.BRAKE);
        armMotor.setPower(0);

        telemetry.addData("Status", "Arm motor — BRAKE mode active");
    }

    @Override
    public void loop() {
        armMotor.setPower(-gamepad1.left_stick_y);

        // When the stick returns to 0, the arm holds its position
        // instead of drifting downward under gravity
    }
}

Fill-in-the-Blank Practice​

  1. To allow a robot to coast smoothly to a stop, set the behavior to DcMotor.ZeroPowerBehavior.__________.
  2. The BRAKE behavior is implemented by the __________ on the robot, not just the software — the port circuit is physically reconfigured.
  3. If you want a linear slide to hold its position against gravity when the driver releases the joystick, you should use the __________ behavior.
Show answers
  1. FLOAT
  2. Control Hub / Expansion Hub (the hardware motor controller)
  3. BRAKE

Template Challenge​

Robot Scenario: Create a safety configuration for a motor named "lift". If the driver presses gamepad1.y, set the behavior to BRAKE. If they press gamepad1.x, set it back to FLOAT. Display the current mode on the Driver Station.

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="Lift_Safety_Challenge")
public class LiftSafety extends OpMode {

    private DcMotor lift;

    @Override
    public void init() {
        lift = hardwareMap.get(DcMotor.class, "lift");
        lift.setZeroPowerBehavior(DcMotor.ZeroPowerBehavior.BRAKE);
    }

    @Override
    public void loop() {
        // INSERT CODE HERE: If gamepad1.y is pressed, set behavior to BRAKE
        // INSERT CODE HERE: If gamepad1.x is pressed, set behavior to FLOAT

        // INSERT CODE HERE: Display the current ZeroPowerBehavior via telemetry
    }
}
Show answer
@Override
public void loop() {
    if (gamepad1.y) {
        lift.setZeroPowerBehavior(DcMotor.ZeroPowerBehavior.BRAKE);
    } else if (gamepad1.x) {
        lift.setZeroPowerBehavior(DcMotor.ZeroPowerBehavior.FLOAT);
    }

    telemetry.addData("Zero Power Behavior", lift.getZeroPowerBehavior());
}

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