Lesson 5.1: Using if Statements to Decide When a Motor Should Run

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Technical Context

The if statement is the fundamental mechanism for preventing unintended robot movement. By wrapping hardware commands in a conditional block, you ensure that voltage is only applied to I/O ports when specific criteria are met — such as a driver input or a sensor state. This prevents "runaway" robots and mechanical damage during the sensing-thinking-acting cycle.

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How if Statements Turn Inputs into Actions

In the Java JVM, an if statement evaluates a boolean expression found within the parentheses. If the expression evaluates to true, the code block encapsulated by curly braces {} is executed. In FTC, this is typically used to poll the state of a gamepad button (e.g., gamepad1.a) or a digital sensor. Because the loop() method executes approximately 50 times per second, the if statement allows the robot to make real-time decisions based on the current state of the hardware registry.

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Annotated Code

package org.firstinspires.ftc.teamcode.opmodes;

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

@TeleOp(name="Basic_Logic_Test")
public class BasicLogic extends OpMode {

    private DcMotor intake;

    @Override
    public void init() {
        // Hardware instantiation via the HardwareMap
        intake = hardwareMap.get(DcMotor.class, "intake");
    }

    @Override
    public void loop() {
        // Foundational if statement for hardware activation
        if (gamepad1.a) {
            // Command is only sent to the Control Hub if 'a' is true
            intake.setPower(1.0);
        }
        // Technical note: Without an 'else', the motor will never stop
        // once 'a' has been pressed.
    }
}

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Fill-in-the-Blank Practice

1. A foundational decision-making structure in Java starts with the __________ keyword followed by a conditional expression in parentheses.
2. The code following a conditional statement should be encapsulated in __________ to prevent logic errors and ensure multiple statements execute together.
3. In a sensing-thinking-acting machine, the if statement represents the __________ phase of the cycle.

Show answers

1. if
2. curly braces {}
3. thinking

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Template Challenge

Robot Scenario: Your team needs a safety switch. The DC Motor named "flywheel" should only run at full power if the driver is holding gamepad1.right_bumper.

Unit 5 simulator

Supports gamepad-driven `if`, `else if`, and `else` logic with live branch visualization.

Includes truth-table and condition-inspector views, plus mock distance and color sensor inputs when needed.

Best for practicing decision logic, thresholds, and simple actuator commands.

Show answer

@Override
public void loop() {
    if (gamepad1.right_bumper) {
        flywheel.setPower(1.0);
    } else {
        flywheel.setPower(0.0);
    }
}

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