A micro:bit light meter calibrated against a lux meter

The idea

A sensor turns light into a number on its own scale (0 to 255 on a micro:bit), and a calibration table made against a lux meter turns those numbers into a judgement such as 'too dark to read'.

What you need

• 1 BBC micro:bit per pair with a battery pack
• Computer with the MakeCode editor
• 1 lux meter, or a tablet with a light-meter app
• Recording table with columns: place, micro:bit value, lux

How to do it

1. Write a user story and design criteria, for example: as a teacher, I want to know whether the reading corner has enough light, so the meter must give a clear yes or no.
2. Sketch the display: which icon means too dark, which means OK, and what button A does.
3. Program: when button A is pressed, store the light level in a variable and show it.
4. Measure at 8 or more places from dark to bright (inside a cupboard, under a desk, on a desk, beside a window, outside in shade), holding the micro:bit and the lux meter side by side.
5. Record both readings at each place and sort the table from darkest to brightest.
6. Choose a threshold from the table and add: if the light level is below the threshold show a 'too dark' icon, else show a tick.
7. Test the program at the brightest and darkest places and at the threshold.
8. Compare your table with the ACARA example table and explain any differences.

What you should see

The micro:bit value rises with the lux reading, from near 0 in a cupboard to 255 in bright sun; 255 is the top of its scale, so anything brighter also reads 255. ACARA's Digital Technologies in focus table pairs micro:bit 102 with 592 lux, 224 with 2017 lux and 255 with 5000 lux, and uses 100 (about 500 lux; 575 lux by linear interpolation of the table) as the boundary for acceptable reading light. Lux is about 5.4 times the micro:bit value in dim light (190 lux at 35) but 9.0 times in bright light (2017 lux at 224), so no single multiplier converts the scale. A class table differs in detail because sensors differ, but the rise and the ceiling at 255 appear. The learner knows it worked when the icon changes at the threshold they chose.

What changes

What you change

place (light level)

What you measure

micro:bit value and lux reading

What you keep the same

• micro:bit and meter held side by side
• the same holding angle
• readings taken within a few seconds of each other

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

• The micro:bit measures in lux (it gives a number on its own 0 to 255 scale).
• Double the micro:bit number means double the light (the table shows the relationship is not a single multiplier).
• A reading of 255 is the brightest light there is (it is the top of the sensor's scale).

Safety card

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

• Science and Technology K–6 Syllabus (2017), NESA. The syllabus taught in 2026; the 2024 syllabus replaces it from 2027. Code read from the official syllabus document (DOCX) on 2026-09-22.ST3-11DI-T
• Science and Technology K–6 Syllabus (2024), NESA. Implementation from 2027, so this code describes the future syllabus. Code read from the outcomes page on 2026-09-22.ST3-DDT-02
• Australian Curriculum v9AC9TDI6P05AC9TDI6K03AC9TDI6P01AC9TDI6P03

Sources

The pages the author read to write this activity.

1. www.nsw.gov.au/education-and-training/nesa/curriculum/science/science-and-technology-k-6-2017
2. curriculum.nsw.edu.au/learning-areas/science/science-and-technology-k-6-2024/outcomes
3. www.digitaltechnologieshub.edu.au/media/fvnd5rer/acara-classroom-ideas-5-6-microbit-environmental-measurementpdf.pdf
4. makecode.microbit.org/reference/input/light-level