Though the following example uses the Circuit Playground Express to demonstrate, the code works exactly the same way with the Circuit Playground Bluefruit. Simply copy the code and follow along with your Circuit Playground Bluefruit!

The Circuit Playground Express can see you! OK, not really. That would be creepy. 

But, it can sense light and dark, as well as colors and even your pulse!!

The Light Sensor in the upper left of the board (look for the eye icon) is a phototransistor. Here's how to use it as a light sensor:

In the example below, click the Download Project Bundle button below to download the necessary libraries and the file in a zip file. Extract the contents of the zip file, open the directory Introducing_CircuitPlaygroundExpress/CircuitPlaygroundExpress_LightSensor/ and then click on the directory that matches the version of CircuitPython you're using and copy the contents of that directory to your CIRCUITPY drive.

Your CIRCUITPY drive should now look similar to the following image:

# SPDX-FileCopyrightText: 2017 John Edgar Park for Adafruit Industries
# SPDX-License-Identifier: MIT

# Circuit Playground Light Sensor
# Reads the on-board light sensor and graphs the brightness with NeoPixels

import time
import board
import neopixel
import analogio
import simpleio

pixels = neopixel.NeoPixel(board.NEOPIXEL, 10, brightness=.05, auto_write=False)
pixels.fill((0, 0, 0))

light = analogio.AnalogIn(board.LIGHT)

while True:
    # light value remapped to pixel position
    peak = simpleio.map_range(light.value, 2000, 62000, 0, 9)

    for i in range(0, 9, 1):
        if i <= peak:
            pixels[i] = (0, 255, 0)
            pixels[i] = (0, 0, 0)


The code reads the light sensor and then lights up the NeoPixels like a bar graph depending on the light level. Try waving your hand over it, or shining it with a flashlight to see it change!

This guide was first published on Sep 12, 2019. It was last updated on May 25, 2024.

This page (Playground Light Sensor) was last updated on May 25, 2024.

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