This script check ambient conditions every 2 minutes and updates an LED matrix graph accordingly. It uses a Raspberry Pi Zero W, Adafruit VCNL4010 proximity sensor and a Sense HAT. More info can be found at www.movingelectrons.net.

ambient_conditions.py

#!/usr/bin/python3

# Import the VCNL40xx module.
import Adafruit_VCNL40xx
from sense_hat import SenseHat
import time
import threading
import subprocess

# Create a VCNL4010 instance.
vcnl = Adafruit_VCNL40xx.VCNL4010()


def pixel_image(orientation, temp):
    '''
    Returns a list with a pixel image that can be sent to the
    SenseHat. Each "pixel" (i.e. RGB tuple) is colored based on a
    predefined gradient color range and the temperature passed
    as an argument.

    orientation: can be down, up or same.
    temp: Float.
    '''

    o = (0, 0, 0)

    # Gradient codes from http://www.colorhexa.com/0055e5-to-bf2300
    if temp <= 68.00: x = (0, 85, 229)
    elif 68.01 <= temp <= 71.00: x = (0, 149, 226)
    elif 71.01 <= temp <= 73.00: x = (0, 213, 41)
    elif 73.01 <= temp <= 75.00: x = (192, 200, 0)
    elif 75.01 <= temp <= 78.00: x = (194, 91, 0)
    elif temp >= 78.01: x = (191, 35, 0)
    else: x = (255,255,255)

    up_image = [
    o,o,o,x,x,o,o,o,
    o,o,x,x,x,x,o,o,
    o,x,o,x,x,o,x,o,
    x,o,o,x,x,o,o,x,
    o,o,o,x,x,o,o,o,
    o,o,o,x,x,o,o,o,
    o,o,o,x,x,o,o,o,
    o,o,o,x,x,o,o,o,
    ]

    down_image = [
    o,o,o,x,x,o,o,o,
    o,o,o,x,x,o,o,o,
    o,o,o,x,x,o,o,o,
    o,o,o,x,x,o,o,o,
    x,o,o,x,x,o,o,x,
    o,x,o,x,x,o,x,o,
    o,o,x,x,x,x,o,o,
    o,o,o,x,x,o,o,o,
    ]

    same_image = [
    o,o,o,o,o,o,o,o,
    x,x,x,x,x,x,x,x,
    x,x,x,x,x,x,x,x,
    o,o,o,o,o,o,o,o,
    o,o,o,o,o,o,o,o,
    x,x,x,x,x,x,x,x,
    x,x,x,x,x,x,x,x,
    o,o,o,o,o,o,o,o,
    ]

    if orientation == 'up': px_img = up_image
    elif orientation == 'down': px_img = down_image
    elif orientation == 'same': px_img = same_image

    return px_img

def calc_temp(temp):
    '''
    Calculates adjusted temperature to account for
    CPU temperature and measured ambient temperature.
    Celsius.
    '''

    cmd = "cat /sys/class/thermal/thermal_zone0/temp"
    output = subprocess.check_output(cmd, shell = True)
    # decoding bytes string:
    cpu_str = output.decode('utf-8').strip('\n')
    cpu_float = int(cpu_str)/1000

    calc_temp = temp - ((cpu_float - temp) / 2.0) + TEMP_FACTOR

    return calc_temp

def turn_off():
    '''
    Asks if the device should be turned off and turns it off
    if requested.
    '''

    print('Turn off?')
    sense.show_message('Turn off?', scroll_speed = SCROLL_SPEED)
    event = sense.stick.wait_for_event(emptybuffer=True)
    time.sleep(0.3)

    if (event.direction == STICK_TRIGGER) and (event.action == 'pressed'):
        sense.show_message('Turning off device. Wait 15 sec. before disconnect...', scroll_speed = SCROLL_SPEED)
        subprocess.run(['sudo', 'shutdown', 'now'])
        return


def check_events():
    '''
    Function called by the Event Thread. It performs two tasks:
    a. Checks the distance between an object and the proximity sensor while
    the other thread is working. If the distance is below a
    threhold, it raises a flag (in_range) which is seen by the other
    Thread and interrupts operation in that thread.
    b. Checks if the SenseHat joystick is moved in the direction defined
    by STICK_TRIGGER and calls a function.
    '''

    while True:

        time.sleep(0.25)

        # Read proximity data and joystick input
        proximity = vcnl.read_proximity()
        stick = sense.stick.get_events()

        # Object at about 4.5 cms or closer.
        if proximity > 2050:
            print('Object in range')
            in_range.set()

        if stick: #i.e. If list is not empty.
            if stick[0].direction == STICK_TRIGGER:
                turn_off()

    return


def conditions():
    '''
    Main Thread. It shows an image on the LED matrix representing the change in
    temperature since the last measurement.
    '''

    prev_temp = 65 # Arbitrary initial temperature - Farenheit.

    while True:

        if not in_range.is_set():

            # Read sensors
            temp_c = sense.get_temperature()
            humidity = sense.get_humidity()
            pressure_mb = sense.get_pressure()
            #light_lx = vcnl.read_ambient()

            adjted_temp_c = calc_temp(temp_c)

            # Format data
            adjted_temp_f = adjted_temp_c*(9.0/5.0) + 32.0
            adjted_temp_f = float("{0:.2f}".format(adjted_temp_f))
            humidity = float("{0:.2f}".format(humidity))
            pressure_mb = float("{0:.2f}".format(pressure_mb))
            #pressure_in = 0.03937008*(pressure_mb)
            #pressure_in = float("{0:.2f}".format(pressure_in))

            print('SenseHat measured temperature: {} C'.format(temp_c))
            print('Adjusted temperature: {} C'.format(adjted_temp_c))
            print('Adjusted temperature: {} F'.format(adjted_temp_f))
            #print(light_lx)

            # Determine arrow direction
            if adjted_temp_f < prev_temp: arrow = 'down'
            elif adjted_temp_f > prev_temp: arrow = 'up'
            else: arrow = 'same'
            prev_temp = adjted_temp_f

            image = pixel_image(arrow, adjted_temp_f)
            sense.set_pixels(image)

            # This is used instead of time.sleep() to be able to interrupt
            # the 'sleep' when the event flag is raised.
            in_range.wait(READINGS_INTERVAL*60)

        else:
            ambient_str = 'Temp: {} F Humidity: {} % Pressure: {} mb'.format(adjted_temp_f, humidity, pressure_mb)
            sense.show_message(ambient_str, SCROLL_SPEED)
            in_range.clear()

    return

if __name__ == '__main__':

    STICK_TRIGGER = 'down'
    SCROLL_SPEED = 0.015
    TEMP_FACTOR = 1.65 #Temp. adjustment factor in Celsius.
    READINGS_INTERVAL = 2 # in minutes.

    sense= SenseHat()
    sense.set_rotation(180)

    # Threading event to be used as flag to communicate between threads.
    in_range = threading.Event()

    event_thread = threading.Thread(name='check events', target=check_events)
    main_thread = threading.Thread(name='conditions', target=conditions)

    event_thread.start()
    main_thread.start()