Week 11 — Ultrasonic Sensors & Echolocation

Focus Concept: Using input sensors + mapping & constraining to control output behaviour
Mini-Project: Echolocation Beeper (closer = faster beeps, farther = slower beeps)

Connections to STEAM Learning

  • Computing: We used an ultrasonic sensor to read real-world values, introduced two important maths functions — mapping (converting ranges) and constrain (keeping values safe), and used a MakeCode extension to simplify hardware control.
  • Science: We linked our project to echolocation in bats and dolphins, exploring how sound waves reflect off surfaces.
  • Maths: We worked with measurements (cm), comparisons, range conversions using mapping, and learned why we sometimes need to constrain noisy sensor values.
  • Engineering & Technology: We built a working sensing system using the micro:bit, a terminal block expansion board, a breadboard and an ultrasonic sensor.

This week we explored how computers can “sense” distance using sound, just like animals that use echolocation.
We learned how an ultrasonic sensor sends out a tiny ultrasonic “ping”, listens for the echo, and estimates distance based on how long the echo takes to return.

We first wired the sensor on P0 (TRIG) and P1 (ECHO) to understand the raw timing code behind the scenes.
Later, when switching to the MakeCode extension, we deliberately moved the sensor to P13 and P14. This showed that extensions can use any suitable pins — we are not limited to just P0 and P1 — and that choosing pins is part of designing a physical computing system.

With everything connected, we turned every micro:bit into a small “bat”: it beeps more quickly when something is close and slowly when things are far away.
To do this, we introduced two essential maths tools:

  • mapping — converting one range (10–300 cm) into another (100–1000 ms)
  • constrain — keeping sensor values inside a predictable range before mapping

These help keep the beeping smooth and realistic.

Objectives

  • Understand how echolocation helps animals and sensors detect distance.
  • Wire an ultrasonic sensor using the expansion board and breadboard.
  • Read distance values from the sensor using a MakeCode extension block.
  • Use constrain to keep distance readings in a safe range.
  • Use mapping to convert a distance value into a pause duration.
  • Build an echolocation beeper where beeping changes based on how near an object is.
  • Practise loops, input/output behaviour, and simple maths functions.

Success Criteria

  • I can explain how the ultrasonic sensor measures distance using echo time.
  • I can wire TRIG and ECHO pins correctly using the terminal block shield.
  • I can read distance easily using an extension block.
  • I can use constrain to stabilise sensor readings.
  • I can use mapping to convert distance into a delay.
  • I can make a program where beeping becomes faster as something gets closer.
  • I can test and adjust my code to improve the behaviour.

Key Vocabulary

  • Echolocation — finding where things are by sending sound and listening for the echo.
  • Ultrasonic sensor — an input device that sends high-frequency sound and listens for the reflection.
  • TRIG / ECHO — the pins used to send the pulse (TRIG) and receive the echo (ECHO).
  • Extension — an add-on pack in MakeCode that gives extra blocks for special hardware.
  • Mapping — converting a number from one range into another (e.g. 10–300 → 100–1000).
  • Constrain — keeping a value inside a chosen minimum and maximum range.
  • Input device — something that gives the micro:bit information.
  • Output — something the micro:bit does (sound, light, messages).
  • Transducer — a device that converts one type of energy into another (e.g., electrical energy into sound waves, or sound waves back into electrical signals).

Part A — Echolocation & Real-World Sensing

We began with a discussion about animals that use echolocation, such as bats and dolphins.
Children explored how sending a sound and listening for the reflection helps creatures navigate in the dark or underwater. We linked this to sonar used in ships and submarines.

We handled the ultrasonic sensor and identified the two “eyes”:

  • one sends the sound pulse,
  • the other listens for the echo.

This gave us a clear mental model of how the micro:bit measures distance.

Part B — Wiring & Understanding the Sensor

Using the Keyestudio terminal block shield and a breadboard, children wired:

  • VCC → 3V
  • GND → GND
  • TRIG → P0 (for the raw demo)
  • ECHO → P1 (for the raw demo)

We demonstrated the “behind the scenes” timing code and explained why dividing the echo time by 58 gives a distance in centimetres.

After this low-level demonstration, we added a MakeCode extension to make everything cleaner.
To emphasise that extensions are flexible, we wired the sensor to different pins for the main project:

  • TRIG → P13
  • ECHO → P14

Part C — Echolocation Beeper (Build & Play)

For our main activity, we turned each micro:bit into a “bat”.

Using the extension to read distance — and combining mapping + constrain — children created a system where:

  • Close object → fast beeps + bright LED
  • Medium distance → medium-speed beeps
  • Far away → slow beeps + dim LED

Mapping allowed us to convert 10–300 cm smoothly into 100–1000 ms.
Constraining kept the sensor values stable so the behaviour didn’t jump around.

Resources

  • MakeCode Editor: Link
  • Ultrasonic Sensor - no extension: Code
  • Echolocation project - using extension: Code
  • How Do Ultrasonic Distance Sensors Work?: Video 1 / Video 2
  • What Is Echolocation? - BBC Earth Explore: Video
  • How does whale communication work? - TED-Ed: Video
  • Makecode MAP function: Reference
  • Makecode CONSTRAIN function: Reference

Equipment

  • BBC micro:bits + USB cables
  • Laptops / Chromebooks
  • Keyestudio terminal block shield
  • Ultrasonic sensors (HC-SR04 or similar)
  • Breadboards + jumper wires
  • Objects for testing

Safety & Setup Notes

  • Double-check TRIG/ECHO wiring before powering.
  • Keep wires tidy to avoid disconnects.
  • Keep volume of beeps comfortable in groups.
  • Encourage children to experiment with distance safely.