Skip to content

Light Sensor

On this page we will learn

  • how the micro:bit measures light with its display
  • how to read the light level

Terminology

  • light sensor – a sensor that measures how much light is shining on it; on the micro:bit, the display LEDs do this job.

The micro:bit uses the LEDs on its display to measure how much light is shining on it.

Possible uses:

  • night lights
  • day and night detectors
  • light-activated alarms
  • automatic brightness

Connect it

The light sensor is the display itself, so we don't need to connect anything.

  • Each example is a main.py file. See Your First Program for how to create, upload and run it.
  • Readings go from 0 (dark) to 255 (bright).

Set it up

The light sensor is part of the microbit library. We import it at the top of every program:

1
from microbit import *

Methods

Method Parameters Returns Description
display.read_light_level() none int (0–255) The light level on the display

display.read_light_level()

Returns how much light is shining on the display, from 0 (dark) to 255 (bright).

1
2
3
4
5
from microbit import *

# Main loop
while True:
    display.scroll(display.read_light_level())

PRIMM

  1. Predict what you think will happen. Be specific.
  2. Run the program.
  3. Time to investigate the code. What does each line do?
Code explanation
  • line 1 → imports all the commands from the microbit library.
  • line 4 → starts an endless loop.
  • line 5 → reads the light level and scrolls it across the display.

Documentation

Documentation is the official guide written by the people who made the code library, and we can use it to look up every method and its parameters, including ones that aren't covered on this page.

Exercises

PRIMM

Time to modify the code and see what happens.

Starter files are in the light folder of your tutorial files. Solutions are on the Exercise Solutions page.

Exercise 1

Starter: light/ex1_up_down

Can you create a program that checks the light level every 2 seconds, and shows an up arrow if it has increased since the last check, or a down arrow if it has decreased?

Exercise 2

Starter: light/ex2_night_light

Can you create a program that turns on all the LEDs when the light level falls below 100?