Lesson: waitUntil Bump then Move

Overview

In this lesson, you will learn how to program a waitUntil command with conditions that use the Bumper Switch sensors. Follow the instructions below and then build on these skills in the "Try It" activities!

waitUntil Command

1. Open the “waitUntil1” project you started on the Robot Configuration page.

2. Write the following code in your project:

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int main() {
    // Initializing Robot Configuration. DO NOT REMOVE!
    vexcodeInit();

   waitUntil(rearBumper.pressing());
   Drivetrain.driveFor(forward, 500, mm, 25, velocityUnits::pct);  
}

The waitUntil() command is used to keep the robot running at this spot until the code in parentheses is evaluated as true.

Attached to the waitUntil command is a condition (the code inside the parenthesis). Conditions are statements made for the robot to evaluate something as either true or false.
The .pressing() command checks the specified Bumper Switch:

Has a value of true when pressed
Has a value of false when not pressed

3. Download and Run the program.

4. Observe.

As programmed, your robot waits for the Bumper Switch to be pressed before moving forward. To allow the robot to read past the waitUntil command, press on the rear Bumper Switch! Your robot will move the set amount duration once it is pressed.

Try It: Modify Rear Bumper Switch

The red cap on the Bumper Switch can be replaced with other components or modified to serve a specific purpose. Modify your rear Bumper Switch by inserting a 0.375 OD x 0.500" Nylon Spacer with a #8-32 x 0.750" Star Drive Screw so that the red cap reaches out further than the arm’s red gear.

What happens?

Try It: Detect a Wall

Place the robot 500mm away from a wall.

Download and run the program.

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int main() {
    // Initializing Robot Configuration. DO NOT REMOVE!
    vexcodeInit();

    Drivetrain.driveFor(reverse, 500, mm, 25, velocityUnits::pct); 
    waitUntil(rearBumper.pressing());
    Drivetrain.driveFor(forward, 500, mm, 25, velocityUnits::pct);
}

What happens?

Try It: Detect a Wall Pt. 2

Use the same program. However, this time, place your robot at least 600mm away from the wall.

Download and run the program.

What happens?

Did You Know? Bumper Switch Sensor

The Bumper Switch v2 reports to the Robot Brain is whether it is pressed in, versus released. The Bumper Switch v2 allows the robot to sense physical collisions. When the Bumper Switch is pressed, it closes an electrical circuit, allowing current to flow. If the Bumper Switch is released, the circuit is broken and no current flows.

The flow (or lack) of current is detected by the robot, allowing it to determine the Bumper Switch is pressed.

The V5 Robot Brain allows you to check the values of the Bumper Switches under the Devices menu. Choose Devices, then select the triangular icon.

The Devices menu does not automatically “know” what type of sensor is connected. Tap the box where the Bumper Switch is connected until it displays Digital Input. The Bumper Switch is a type of touch sensor, which is a Digital Sensor. When the Bumper Switch is released, it should have a value of High (1), and when pressed a value of Low (0).

Which of the following commands checks if a Bumper Switch is pressed?

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Wait Until with VEX V5

Overview

waitUntil Command

Try It: Modify Rear Bumper Switch

What happens?

Try It: Detect a Wall

What happens?

Try It: Detect a Wall Pt. 2

What happens?

Did You Know? Bumper Switch Sensor