F-4 Detect If Bumped

Finally, you'll code an app that uses the accelerometer to detect when the robot has been bumped (e.g., by colliding with another object, etc.). If the robot is bumped, it will stop its motors and make an alert sound.

Save Copy of App With New Name

In your Arduino code editor, use the "Save As" command to save a copy of the upside_down_test app as a different app named: detect_bump_test

Once you saved the new app name, modify the block comment near the beginning of the app code to change Detect Upside-Down Test to Detect Bump Test.

Start Bump Detection

The RedBotAccel class defines a method named checkBump() that can detect whether the robot has been physically bumped as the result of a collision or other force.

However, your app must first enable bump detection by using another method named enableBump() which is also defined in the RedBotAccel class. This is only required one-time.

To enable bump detection, add this code statement within the setup() function:

accel.enableBump();

Modify Code to Perform When Robot is Started

Your app can check for a "bump" using the RedBotAccel object's checkBump() method, which will return a value of true or false based on whether or not a physical bump was detected.

The checkBump() method can detect a bump from any direction on the robot's body (front, back, left, right, top, or bottom) — but it won't tell you which specific direction the bump came from.

When the D12 button is pressed to "start" the robot, we want the robot to check whether it has been bumped by using the checkBump() method and then performing appropriate actions based on the result:

  • If the robot has been bumped, it should brake its motors, make an alert sound, and "pause" itself.

  • Otherwise, the robot should drive forward.

The boolean value returned by the checkBump() method will be stored in a local variable named bump.

First, delete the existing code statements within the if statement in the loop() function that are performed when started is true

Next, add this code within the if statement in the loop() function, so it will be performed when started is true:

    bool bump = accel.checkBump();
    if (bump == true) {
      // add code to perform special actions: brake, distress signal, etc.
        motors.brake();
        // triple beep
        for (int i=0; i < 3; i++) {
          tone(speaker, 4000, 100);
          delay(200);
        }
        started = false; // pause until button pressed again
    }
    else {
        // add code to perform normal actions: drive, turn, etc.
        motors.drive(100);
    }

Upload App to Robot

Follow the steps to connect your robot to your computer, and upload the app.

Unplug the USB cable from the robot, and place the robot on the floor.

Press the D12 button to "start" the robot driving forward. You can use your hand to tap the front of the robot. When a bump is detected, the robot should stop, make an alert sound, and then pause itself.

Press the button again, and then tap on another part of the robot's chassis (side, back, etc.). You can repeat to test other bumps to the robot.

When you're done testing the robot, you can turn off its power.

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