Playground Light Sensor

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:

# CircuitPlaygroundExpress_LightSensor
# reads the on-board light sensor and graphs the brighness with NeoPixels

import time

import board
import neopixel
from analogio import AnalogIn
from simpleio import map_range

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

analogin = AnalogIn(board.LIGHT)

while True:
    # light value remaped to pixel position
    peak = map_range(analogin.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)


Copy and paste that code into a text editor and then save it to your Circuit Playground Express as

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 Oct 12, 2017. It was last updated on Nov 17, 2018. This page (Playground Light Sensor) was last updated on Aug 01, 2018.