Instruction Guide: EV3 - Move until Near


In this lesson students explore the use of the Ultrasonic Sensor.

In this Lesson we have 1 Primary Instruction Resource:

  1. The resource is a EV3 Trainer lesson on the Ultrasonic Sensor called Move Until Near.

The EV3 Trainer has a lesson describing the Ultrasonic Sensor

Behaviors >Sensors > 4. Move Until Near

The EV3 Trainer Teacher's Guide references this on pages 43-49.

Students should be able to answer all the review questions at the end of each step and end up with a solid command of each parameter in the Wait-until-Ultrasonic sensor block configuration panel and an understanding of how the ultrasonic sensors works.

The Optional Activities below the review questions in Step 3 include a "Did You Know" which shows the operation of the Ultrasonic Sensor and "Try It" sections which dig deeper into the Sound Block and Wait-for-Ultrasonic parameters.

The EV3 Trainer Teacher’s Guide has additional reproducibles for those who have purchased the product. The  reproducibles for Move Until Near can be found on pages 99-100.

As students progress through, have them document their milestones in the Move Until Near Task Assignment Sheet.

There are 3 challenges:

  1. Mini Challenge : Threshold Value Behaviors >Sensors > 4. Move Until Near > 3
  2. Mini Challenge : Backward Until Far  Behaviors >Sensors > 4. Move Until Near > 4
  3. Maze ChallengeBehaviors >Sensors > 4. Move Until Near > C

Maze Challenge

Key learning to check for during sign-off includes:

  • Ensure students have a basic understanding of the physics behind the ultrasonic sensor's operation:
    • Ensure students understand ultrasonic means sound waves above the human-audible range
    • But, they are still sound waves and behave as such:
      • They bounce of hard surfaces
      • They can be partially absorbed by soft surfaces
      • They bounce differently off of flat vs round vs angled surfaces
      • They can interfere with each other
    • Comparison to a bat's echo-location connects with some students
  • Have the students explain their choice of hardware design (how/where the Ultrasonic sensor was attached/positioned)
    • If your maze walls are relatively short (made of 2x4's, or shorter) the prescribed Ultrasonic Sensor attachment may be too high for optimal performance.
  • Revisit the concept of a threshold.
    • With the Color Sensor, a threshold is usually calculated from a measured "light" and "dark" value
    • With the Ultrasonic Sensor, a threshold is usually set based on some design constraint or desired outcome
    • Ensure students can distinguish between these two and explain the difference
    • Have students explain their program
      • Start with their flowchart/pseudocode to get an overall view of the program
      • Use the EV3-G program to show how each block was implemented
      • Ensure the understand the the parameters in the Wait-Until-Ultrasonic Sensor block
      • Ask how the Wait and Move block parameters were determined
      • Encourage the use of comments in their program - at a minimum, the block labels in the flowchart or pseudocode should appear as comments in EV3-G