Temperature and humidity reading from RHT03 (also known as DHT22) using ESP8266 WeMos D1 mini board.
As many other examples available on the internet, it was inevitably to post myself a temperature and humidity reading application.
The values from sensors are displayed on the mobile phone, using Blynk IoT framework.
Ingredients:
ESP8266 WeMos D1 mini board
RHT03 temperature and humidity sensor
Sensor specifications:
- 3.3-6V Input
- Humidity from 0-100% RH, ±2% RH accuracy
- -40 – 80 degrees C temperature range,±0.5 degrees C
source: http://cdn.sparkfun.com/datasheets/Sensors/Weather/RHT03.pdf
Details here: https://learn.adafruit.com/dht
Download and install DHT22 arduino library into your Arduino IDE. The library is available here: https://github.com/adafruit/DHT-sensor-library
Blynk knowledge and blynk app installed on your android or iphone.
Breadboard and wires
Ok, let’s put this ingredients into one “bowl”, like this
Connect the data pin of the sensor to GPIO2 (marked as D4) which already has an internal 10k pull-up resistor.
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#define BLYNK_PRINT Serial // Comment this out to disable prints and save space #include <ESP8266WiFi.h> #include <BlynkSimpleEsp8266.h> #include <SimpleTimer.h> #include <DHT.h> #define DHTPIN D4 //pin gpio 2 in sensor #define DHTTYPE DHT22 // DHT 22 Change this if you have a DHT11 DHT dht(DHTPIN, DHTTYPE); //static const uint8_t SDA = 4; //static const uint8_t SCL = 5; // //static const uint8_t LED_BUILTIN = 2; //static const uint8_t BUILTIN_LED = 2; // //static const uint8_t D0 = 16; //static const uint8_t D1 = 5; //static const uint8_t D2 = 4; //static const uint8_t D3 = 0; //static const uint8_t D4 = 2; //static const uint8_t D5 = 14; //static const uint8_t D6 = 12; //static const uint8_t D7 = 13; //static const uint8_t D8 = 15; //static const uint8_t RX = 3; //static const uint8_t TX = 1; //////////////////// // Blynk Settings // //////////////////// char BlynkAuth[] = "142da76c91af47b192d396xxxxxxxxx"; char WiFiNetwork[] = "xxxxxxWlan"; char WiFiPassword[] = "xxx_xxx_xxx_xxx"; SimpleTimer timer; float t,h; unsigned long previousMillis = 0; // will store last temp was read const long interval = 2000; // interval at which to read sensor void setup() { Serial.begin(115200); // Serial // put your setup code here, to run once: pinMode(BUILTIN_LED, OUTPUT); // initialize onboard LED as output dht.begin(); // Initialize Blynk Blynk.begin(BlynkAuth, WiFiNetwork, WiFiPassword); // Setup a function to be called 30 second timer.setInterval(30000L, sendUptime); } void loop() { // put your main code here, to run repeatedly: //digitalWrite(BUILTIN_LED, HIGH); // turn on LED with voltage HIGH //delay(1000); // wait one second //digitalWrite(BUILTIN_LED, LOW); // turn off LED with voltage LOW //delay(1000); // wait one second Blynk.run(); timer.run(); } void sendUptime() { // You can send any value at any time. // Please don't send more that 10 values per second. //Read the Temp and Humidity from DHT gettemperature(); Serial.print("temp:"); Serial.println(t); Serial.print("humi:"); Serial.println(h); Blynk.virtualWrite(10, t); // virtual pin Blynk.virtualWrite(11, h); // virtual pin } void gettemperature() { // Wait at least 2 seconds seconds between measurements. // if the difference between the current time and last time you read // the sensor is bigger than the interval you set, read the sensor // Works better than delay for things happening elsewhere also unsigned long currentMillis = millis(); if(currentMillis - previousMillis >= interval) { // save the last time you read the sensor previousMillis = currentMillis; // Reading temperature for humidity takes about 250 milliseconds! // Sensor readings may also be up to 2 seconds 'old' (it's a very slow sensor) h = dht.readHumidity(); // Read humidity (percent) t = dht.readTemperature(); // Read temperature as C // Check if any reads failed and exit early (to try again). if (isnan(h) || isnan(t)) { Serial.println("Failed to read from DHT sensor!"); return; } } } |
Change your BlynkAuth, WiFiNetwork, WiFiPassword to your settings.
This program generate a serial output like this:
The blynk app has a gauge, a value display and a history graph item
updated 2020.07.23
BOM used in this article:
- Blynk app for android
- ESP8266 Wemos D1 mini (Amazon, Aliexpress)
- DHT22/AM2302/RHT03 temperature sensor (Amazon, Aliexpress)
- Breadboard Solderless Prototype with 4 power rails (Amazon, Aliexpress)
This is EXACTLY what I needed!
Many thanks for documenting this so good.
Still working right now in my home.
Glad it helps!
I’ve added a loop of 3 times readings from the sensor (with a pause of 3 seconds) if I get a fail reading from the sensor.
Thank you. This is one of the best well expleined instructions. Is this code suitable for ESP8266 only (without WeMos D1 mini board) if we program the ESP8266 module via CP2102 USB UART Board (mini)? I want to miniaturize the setup that is why I am asking:)
Thanks for reading.
This instructions and my knowledges are gathered from many sources. You cand find many instructables with this setup.
To answer on you question, yes, you can use this code on any ESP8266 module. The only mention is that to check if the board/module you have has an internal pull-up resistor on D4 pin (for this example).
If you are using any other digital pin, the reading of the sensor will also be ok.
Here is an example with nodemcu board
https://blog.squix.org/2016/01/esp8266-weather-station-measuring.html
Join us on facebook group “ESP8266” to get specific answers.
Just a little tip. Do not use the delay() function, IT will delay your commands to Blynk
Hello, thank you for the suggestion! That delay should not be inside the loop.
I’ve changed the code above, thank you.