Case 5: Wind Vane

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Introduction

The electronic compass (magnetometer) built into the micro:bit V2 board detects the direction of Earth's magnetic field and displays the board's current orientation on the 5×5 LED matrix in real time — showing the four cardinal directions: East, South, West, and North. Rotate the micro:bit V2 board to simulate a wind vane turning with the wind.

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Learning Objectives

1. Learn about the electronic compass (magnetometer) — a MEMS sensor capable of detecting geomagnetic direction.
2. Learn conditional branching (if-else if-else) — displaying different arrow icons based on different ranges of azimuth angle values.
3. Understand the important role of wind vanes in meteorological observation and navigation.

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Required Materials

Item	Image	Quantity
micro:bit V2		1
Jacdac Expansion Board		1
Jacdac 10cm Connector Cable		1
Jacdac Temperature & Humidity Sensor		1
USB Cable		1

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Sensor Principle

This case uses the built-in magnetometer (electronic compass) of the micro:bit V2 as the sensor. It detects the direction of Earth's magnetic field and outputs azimuth angle data ranging from 0° to 360°. The program displays corresponding arrow icons based on different azimuth angle ranges.

Assembly Steps

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Model Principle

Wind Vane — One of the Oldest Meteorological Instruments

The wind vane is a classic tool for measuring wind direction, consisting of three parts: an arrow, a tail fin, and a pivot axis. When the wind blows, the tail fin — which has a larger surface area and greater air resistance — is pushed to the downwind side. The arrow then points in the upwind direction — i.e., the direction the wind is coming from. This ingenious design allows the wind vane to automatically align with the oncoming wind direction without any electricity.

The naming convention for wind direction is: "named after where it comes from" — a north wind blows from the north, an east wind from the east. In meteorology, wind direction is precisely recorded using 16 compass points (N, NNE, NE, ENE, E, ...).

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Connection Diagram

As shown below, insert the micro:bit V2 board into the Jacdac expansion board, and connect the Jacdac Temperature & Humidity Sensor to the Jacdac expansion board's edge connector.

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Programming Software

Microsoft MakeCode

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MakeCode Programming

Step 1: Adding the Jacdac Extension

1. Go to Microsoft MakeCode and click "New Project".

   

2. Enter a project name in the pop-up window and click "Create".

   

3. Click "Extensions" in the code drawer.

   

4. In the pop-up interface, type "Jacdac" and click the search icon, then select the Jacdac software library as shown.

   

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Step 2: Connecting the Hardware

1. Use a USB cable to connect the micro:bit V2 board to the computer.

   Note: If this is the first time running a Jacdac program on the micro:bit V2, please pre-load a blank Jacdac program onto the board first. Otherwise, skip this step.

   

2. Connect the sensor. MakeCode will automatically detect and simulate it in the simulator area, where sensor status is displayed in real time.

   

3. Click "ADD BLOCKS" to add the sensor extension module.

   Note: When connecting a new sensor, repeat the "click 'ADD BLOCKS'" workflow once.

   

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Write the Program as Shown

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Reference Program Link

https://makecode.microbit.org/_3XeaWzi7FALP

You can also download the program directly from the webpage below. Once downloaded, you can start running the program.

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Result

Place the micro:bit V2 board horizontally and rotate it slowly. The 5×5 LED matrix displays arrow icons for the four cardinal directions — East, South, West, and North — using the magnetometer reading to determine the board's current orientation.

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Think

1. The magnetometer detects magnetic north, while the "north" on a map is geographic north — the two do not perfectly coincide. Do you know why? (Hint: search for "magnetic declination")
2. What happens to the direction reading if you place the micro:bit on a metal desk or near a phone? Why?

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Program Logic

Trigger Condition	Action	Source
Magnetometer detects azimuth angle	Based on azimuth angle range (0°–360°), determines direction and displays arrow icons for East, South, West, and North on the 5×5 LED matrix	micro:bit Magnetometer

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Knowledge Extension: From Compass to GPS — How Humans Found Their Way

I. The Compass — One of the Four Great Inventions That Changed World Navigation

The compass is one of ancient China's Four Great Inventions. As early as the Warring States period (~4th century BCE), the Chinese had discovered the directional properties of lodestone and created the earliest navigation tool — the sinan (a magnetic spoon placed on a smooth bronze plate, with the handle pointing south). By the Northern Song Dynasty (~11th century CE), the Chinese invented the guide fish and floating compass, which were widely applied to navigation.

Period	Navigation Method	Accuracy
Ancient times	Observing sun, stars, landmarks	Rough (clear days / nights only)
4th century BCE	Sinan (China)	Rough north-south
11th century	Floating compass (China)	Good; essential for navigation
12th–13th century	Compass introduced to Europe	Opened the Age of Sail
15th–16th century	Compass + sextant + nautical charts	Transoceanic voyages possible
20th century	Gyrocompass (unaffected by magnetic fields)	Accurate to 0.1°
21st century	GPS / BeiDou satellite navigation	Accurate to meter level

Without the compass, there would have been no Age of Sail — Columbus and Magellan's transoceanic voyages would have been impossible without it. A small piece of lodestone changed the map of human civilization.

II. Modern Applications of the Magnetometer

The magnetometer chip in your micro:bit works on the same principle as the compass chips in smartphones:

Application	Magnetometer's Role
Phone map navigation	Detects phone orientation, rotates map to keep "north up"
Drones / aircraft	Works with GPS to determine flight heading and yaw angle
Car navigation	Provides dead reckoning when GPS signal is weak (tunnels, underpasses)
Augmented Reality (AR)	Determines device orientation to overlay virtual objects in the correct direction
Geological surveying	Detects underground mineral deposits and geological structures (via local magnetic anomalies)
Archaeology	Detects magnetic traces of buried objects and ancient sites

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III. The Wind Vane — The Oldest Meteorological Instrument

The history of the wind vane dates back at least to 48 BCE — the Tower of the Winds in ancient Athens, Greece, had a large bronze wind vane (in the shape of a Triton) mounted on top, which is still well-preserved today.

Fact	Data
English name	Weather Vane / Wind Vane
Oldest surviving wind vane	Tower of the Winds, Athens (48 BCE)
Meteorological wind direction precision	16 compass points (22.5° each) or 360° (1° each)
Wind naming convention	Named after the direction the wind comes from
Airport windsock	Indicates both direction and speed (by how inflated it is)

Think about it: Over two thousand years ago, the Greeks — without batteries, without chips — created a device that could automatically indicate wind direction using only clever metal-sheet design. Today, you achieve the same function with a chip the size of a fingernail — and with higher precision, plus the ability to simultaneously record data. That is the beauty of technological progress.

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IV. Electronic Compass vs. Traditional Compass

Comparison	Traditional Compass	Electronic Compass (Magnetometer)
Principle	Magnetic needle interacts with Earth's magnetic field	MEMS chip detects geomagnetic field components
Accuracy	~5°–10°	Up to 1°–2°
Response speed	Slow (needle inertia)	Extremely fast (electronic readout)
Data output	Visual observation	Digital signal, programmable
Interference susceptibility	Vibration, tilt	Nearby metal, electromagnetic fields
Power consumption	Zero	Ultra-low (microwatt range)

The magnetometer on the micro:bit, combined with its accelerometer, can form a complete attitude sensor — knowing "which direction it faces" (magnetometer) and "how much it's tilted" (accelerometer). Together, these enable 3D spatial orientation tracking — the foundational technology behind drones and phone AR applications.