Introduction: Circuit Playground Express Thermometer

I wanted an office thermometer. Rather than buy one I used an Adafruit Circuit Playground Express to make one. It's digital/quasi-analog. The color shows the temperature range (green here - for 70's), with the number of NeoPixels showing the digits (so office temp shown here is 75). When it's dark the display turns off.


Adafruit Circuit Playground Express

3D Printer (I used PLA)

M3 x 8 screws(x4) and M3 nuts (x4)

Magnetic tape (

Step 1: Mount

I wanted some airflow in back since I wasn't sure if the board getting warm would affect the readings. The mount was designed in Fusion 360. Model available on Thingiverse ( Rather than try to keep the screws threaded in the PLA, I provided a space to put M3 nuts in for the M3 screws.

Step 2: Program

The code is Circuit Python, using the Adafruit libraries for the CPE. Most recent code available on GitHub ( but it's fairly basic.

# Office Thermometer
# for Adafruit Circuit Python Express # Uses color to indicate temp range, and then neopixels for exact temp # light sensor turns off NeoPixels if it's dark from import cpx import time BLANK = (0,0,0) BLUE = (0,0,24) # 50's BG = (0,12,12) # 60's GREEN = (0,24,0) # 70's ORANGE = (18,6,0) # 80's RED = (24,0,0) # 90's TEMP_COLOR = {5:BLUE, 6:BG, 7:GREEN, 8:ORANGE, 9:RED} while True: cpx.pixels.fill(BLANK) # make sure pixels refresh if cpx.light > 10: # don't display temp if room is dark temp = int(cpx.temperature * 1.8 + 32.5) # extra 0.5 to make sure temp # rounds correctly if temp < 50: temp = 50 # in the unlikely event temp is lower than 50's if temp > 99: temp = 99 # in unlikely event temp in the 100's tens = temp//10 digit = temp%10 # for temp ending in '0' light up only pixel 0 (tenth pixel as mounted) if digit == 0: cpx.pixels[0] = TEMP_COLOR[tens] # otherwise fill in digits clockwise from 7 o'clock position else: for i in range(digit): cpx.pixels[9 - i] = TEMP_COLOR[tens] # use '9 -' since pixels # in reverse order time.sleep(60) # cycle every 60 seconds

Step 3: Mount

I used some magnetic tape on the back to mount it.