Wireless Temperature Detection System

Software Development Project Development
#1

Hey guys, I am new to the world of coding and I am working on a school project. I have MQTT client code that will run on the ESP32. It polls the DHT-22 and publishes the sensor data to a topic called temp humidity. Then I have another script that runs on the raspberry pi 3 that will subscribe to the temp humidity topic and present the results to an OLED display. What I am thinking of doing is that I want to use another ESP32 that will connect to a LED strip which will subscribe to topic “temp humidity” and go over the data and when the temperature get higher than a certain number, for example 50 degrees Celsius it should turn on the LED strip. I am using python for the main script on the raspberry pi 3 and micropython for the script on the ESP32. If anyone can point me in the right direction I would be grateful. Thanks

(Code is on the replies since for some reason it wouldn’t let me post it on the body)

#2

Here is the MQTT client code that will run on the ESP32.

from time import sleep

from umqtt.simple import MQTTClient

from machine import Pin

from dht import DHT22

SERVER = ‘192.168.1.22’  # MQTT Server Address (Change to the IP address of your Pi)

CLIENT_ID = ‘ESP32_DHT22_Sensor’

TOPIC = b’temp_humidity’

client = MQTTClient(CLIENT_ID, SERVER)

client.connect()   # Connect to MQTT broker

sensor = DHT22(Pin(15, Pin.IN, Pin.PULL_UP))   # DHT-22 on GPIO 15 (input with internal pull-up resistor)

while True:

    try:

        sensor.measure()   # Poll sensor

        t = sensor.temperature()

        h = sensor.humidity()

        if isinstance(t, float) and isinstance(h, float):  # Confirm sensor results are numeric

            msg = (b’{0:3.1f},{1:3.1f}’.format(t, h))

            client.publish(TOPIC, msg)  # Publish sensor data to MQTT topic

            print(msg)

        else:

            print(‘Invalid sensor readings.’)

    except OSError:

        print(‘Failed to read sensor.’)

    sleep(4)

#3

Here is the Raspberry Pi Python MQTT client code.

import paho.mqtt.client as mqtt

import Adafruit_SSD1306

from PIL import Image, ImageDraw, ImageFont

disp = Adafruit_SSD1306.SSD1306_128_32(rst=0)

disp.begin()

FONT_PATH = ‘/usr/share/fonts/truetype/piboto/PibotoCondensed-Regular.ttf’

FONT = ImageFont.truetype(FONT_PATH, 22)

def display_data(t, h):

    image = Image.new(‘1’, (disp.width, disp.height))

    draw = ImageDraw.Draw(image)

    # Draw temperature / Humidity values.

    draw.text((0, 8), ‘{0}°C’.format(t),  font=FONT, fill=255)

    draw.text((71, 8), ‘{0}%’.format(h), font=FONT, fill=255)

    # Draw bar charts.

    draw.rectangle((0, 0, 50, 8), outline=255, fill=0)

    draw.rectangle((71, 0, 121, 8), outline=255, fill=0)

    draw.rectangle((0, 0, t / 100.0 * 50, 8), outline=255, fill=255)

    draw.rectangle((71, 0, 71 + (h / 100.0 * 50), 8), outline=255, fill=255)

    # Send to OLED display.

    disp.clear()

    disp.image(image)

    disp.display()

        # Callback fires when conected to MQTT broker.

def on_connect(client, userdata, flags, rc):

    print(‘Connected with result code {0}’.format(rc))

    # Subscribe (or renew if reconnect).

    client.subscribe(‘temp_humidity’)

Callback fires when a published message is received.

def on_message(client, userdata, msg):

        # Decode temperature and humidity values from binary message paylod.

    t,h = [float(x) for x in msg.payload.decode(“utf-8”).split(’,’)]

    print(’{0}°C {1}%’.format(t, h))

    display_data(t, h)  # Display data on OLED display.

client = mqtt.Client()

client.on_connect = on_connect  # Specify on_connect callback

client.on_message = on_message  # Specify on_message callback

client.connect(‘localhost’, 1883, 60)  # Connect to MQTT broker (also running on Pi).

Processes MQTT network traffic, callbacks and reconnections. (Blocking)

client.loop_forever()