Close menu


  1. Getting Started
  2. Blink
  3. Traffic Light
  4. Reaction Game
  5. Silly Stories
  6. Tally
  7. Guess My Number
  8. Speak Like A Machine
  9. Speech Command
  10. Pose Detect

  1. Security Zone
  2. Ultrasonic Drum
  3. Resistor Piano
  4. Walker Race
  5. Walker Dance
  6. Walker Detect
  7. Runaway Rover
  8. Rover Sensor Steering

  1. Lighthouse
  2. Frog Frenzy
  3. Game Controller
  4. Minecraft Controller

  1. Security Zone
  2. Ultrasonic Drum
  3. Resistor Piano
  4. Ther-Mood-Stat
  5. Color Coded
  6. Pulse

  1. Beam Break
  2. Car Race
  3. Motion Ball

  1. Solar House
  2. Soil Sensor
  3. Air Guitar

  1. Light Show
  2. Light Show Animation



Robotics expedition

Mission 6 of 8

Walker Detect


1 hour

Ages 8+

Learn how to use feedback sensors to send commands to your robot.

And last up, it’s time for final judging. In this mission, you’ll make sure Walker doesn’t walk into the judging table by using the Ultrasonic Range Finder to detect when it’s up against an obstacle.

View student interface at



Adult Zomar

Computer with USB port and Chrome or Edge browser
Piper Make Base Station or Starter Kit
Piper Make Walker


Learning Goals

  1. Students will learn how an ultrasonic range finder works to sense distance as a feedback sensor. 
  2. Students will reinforce their understanding of conditionals, how to use them in programming, and how they can affect actions.  
  3. Students will learn the term Boolean: a binary variable with two possible values called true or false, i.e., “do this or do that.”  
  4. Students are introduced to the term state variable, which is a variable that describes the current state of a system, i.e., sensing whether a true or false has happened.  
  5. Students will learn how to build and program feedback sensors as a binary input. 

Learning Activities

The following sections will contain step by step instructions for ELA, ELD and Math extensions directly related to this mission. Adjust the directions to fit your ELA, ELD and Math standards.

ELA Extension:

Math Extension: Detective Walker Pair students up or allow them to choose a partner. Students will connect time back to previous knowledge of fractions/decimals, or use this to introduce it.

  •  Partner A will be walking; Partner B will be giving commands. They will eventually switch roles. 
  • Connect back to the Walker Dance activity and ask them to describe what a half-step would look like for their Walker.  
  • They will then begin to figure out what a whole, ¾, ½, and ¼ step will look like for their partner.  
  • Have Partner B use tape, paper, or something similar as a marker to begin marking where a natural whole step is for Partner A. 
  • They will need to start using estimations and measurements to figure out each step, which will become their own unit of measurement.  
  • Have students use their initials as the unit of measurement. For example, Jesus Huerta would be 1JH as a whole step, ½ JH for a half step, and so on.  
  • Have students create a chart with their units of measurement that includes conversions to inches for each measurement.  
  • Digitize this into Google Classroom, or write it on a giant piece of butcher paper to display on the wall for future reference! 

Career Connections

Robotics Engineer: Salary $104,600/yr
Automotive Engineer: Salary $95,300/yr
Civil Engineer: Salary $88,050/yr
Electro-Mechanical and Mechtronics Technicians : Salary $60,570/yr

Hardware Diagram

Code Diagram

Tutorial Steps



Troubleshooting Tips

Our customer support specialists are on hand to ensure your implementation of Piper runs seamlessly.
View Support Docs or Contact Support


Material Library

A servo, which is short for servomotor, is a special kind of motor that is used to control something by moving it. A simple motor moved by spinning continuously. A servo turns to a specific position and it uses gears to transform the high speed of the motor into more force so it can move things more easily.

The servo is connected using three wires: one for ground, one for power, and one for a signal that tells the servo motor what position to turn to. The Pico tells the servo what position to turn to by changing the width of the pulse that it is sending out. A pulse with a shorter "ON" time will turn to one side, and a pulse with a longer "ON" time will turn to the opposite side.

The motor inside of the servo turns very fast, but it is also weak - it cannot apply very much force. The gears inside the servo convert the motor's high speed and low force into a slower speed with more force.

Standards Alignment