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Micropython

ESP32 and DHT11 example in Micropython

by shedboy71

In this example we look at a DHT11 example in Micropython for an ESP32. Once again we use uPyCraft and again we use Wemos shields. In this example we will use the original DHT version 1.0.0 shield which was based on the DHT11 . Later shields use the DHT12.

A reminder of the DHT11

The DHT11 digital temperature and humidity sensor is a composite Sensor contains a calibrated digital signal output of the temperature and humidity. Application of a dedicated digital modules collection technology and the temperature and humidity sensing technology, to ensure that the product has high reliability and excellent long-term stability. The sensor includes a resistive sense of wet components and an NTC temperature measurement devices, and connected with a high-performance 8-bit microcontroller.

 

Requirements

Lets take a look a the shields and boards that are required for this example

 

Image Summary
MH-ET LIVE ESP32 MINI KIT WiFi+Bluetooth Internet of Things development board based ESP8266 Fully functional D1 MINI Upgraded
This is the original DHT11 shield – still available from many sellers. The later version uses a DHT12 which is an I2C device
This is simply a base, you plug the Wemos Mini into one side and you can plug a shield or shields into the other side

 

Parts List

I connect the MH-ET LIVE ESP32 MINI KIT to the dual base and then put the DHT shield along side this.

Name Link
Wemos Base Tripler Base V1.0.0 Shield for WeMos D1 Mini
Wemos DHT11 1PCS DHT Shield for WeMos D1 mini DHT11 Single-bus digital temperature and humidity sensor module sensor
MH-ET LIVE ESP32 MINI KIT MH-ET LIVE ESP32 MINI KIT WiFi+Bluetooth Internet of Things development board based ESP8266 Fully functional D1 MINI Upgraded

Code

[codesyntax lang=”python”]

from machine import Pin
import dht
import time

while True:
	sensor = dht.DHT11(Pin(16))
	sensor.measure()

	print('Temperature = %.2f' % sensor.temperature())
	print('Humidity = %.2f' % sensor.humidity())
	time.sleep(3)

[/codesyntax]

 

Output

You should see something like the following in uPyCraft

Ready to download this file,please wait!
..
download ok
exec(open(‘dhtESP32.py').read(),globals())
Temperature = 25.00
Humidity = 18.00
Temperature = 27.00
Humidity = 17.00
Temperature = 27.00
Humidity = 17.00
Temperature = 27.00
Humidity = 17.00
Temperature = 27.00
Humidity = 17.00
Temperature = 27.00
Humidity = 17.00

 

Links

https://akizukidenshi.com/download/ds/aosong/DHT11.pdf

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Code

MH ET LIVE ESP32 MINI KIT and Wemos DHT11 shield example

by shedboy71

As promised we said we would try out some of the Wemos Mini shields with the MH ET LIVE ESP32 MINI KIT.  Here is a picture of the DH11 shield.

Each shield comes with a choice of header you can solder if you want, as you will be able to see in the code example later the DHT11 connects to D4, one disadvantage of using a shield is this cannot be changed but for beginners and most people this is not an issue as the benefits of using the shield outweigh any drawbacks

Here you can see the DHT11 shield connected to a MH ET LIVE ESP32 MINI KIT, again the headers I used allow you to stack another shield on top of the DHt11 such as logging shield or an OLED.

 

Code

This example uses the Adafruit libraries

https://github.com/adafruit/DHT-sensor-library

and

https://github.com/adafruit/Adafruit_Sensor

[codesyntax lang=”cpp”]
#include “DHT.h”

#define DHTPIN 16 // what pin we're connected to

// Uncomment whatever type you're using!
#define DHTTYPE DHT11 // DHT 11

DHT dht(DHTPIN, DHTTYPE);

void setup()
{
Serial.begin(9600);
Serial.println(“DHT11 test!”);
dht.begin();
}

void loop()
{
// Wait a few seconds between measurements.
delay(2000);

float h = dht.readHumidity();
float t = dht.readTemperature();
float f = dht.readTemperature(true);

// Check if any reads failed and exit early (to try again).
if (isnan(h) || isnan(t) || isnan(f))
{
Serial.println(“Failed to read from DHT sensor!”);
return;
}

Serial.print(“Humidity: “);
Serial.print(h);
Serial.print(” %\t”);
Serial.print(“Temperature: “);
Serial.print(t);
Serial.print(” *C “);
Serial.print(f);
Serial.println(” *F”);

}
[/codesyntax]

 

Output

Open the serial monitor and you should see something like this

Humidity: 19.00 % Temperature: 24.00 *C 75.20 *F
Humidity: 18.00 % Temperature: 25.00 *C 77.00 *F
Humidity: 18.00 % Temperature: 25.00 *C 77.00 *F
Humidity: 18.00 % Temperature: 25.00 *C 77.00 *F
Humidity: 18.00 % Temperature: 25.00 *C 77.00 *F
Humidity: 18.00 % Temperature: 25.00 *C 77.00 *F
Humidity: 18.00 % Temperature: 26.00 *C 78.80 *F
Humidity: 18.00 % Temperature: 26.00 *C 78.80 *F

Links

You can pick one of these shields up for about $1.20

DHT Shield for WeMos D1 mini DHT11 Single-bus digital temperature and humidity sensor module sensor

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Code

Use a ESP32 to display DHT11 readings on a web page

by shedboy71

 

In a previous example we displayed DHT11 readings via the serial monitor and we also have had an ESP32 Web server example in the past, you can quite easily combine these two examples together to display readings from a DHT11 sensor on a web page.

Also this demonstrates how its quite easy to take readings from a sensor and display them via a web page

The schematics are the same as before and are here for reference

Parts Required

Here are the parts I used

 

Name Link
ESP32
DHT11
Connecting cables

Schematic

 

lolin32 and dht11

lolin32 and dht11

Code

You need to add the DHT11 library from adafruit to the Arduino IDE – https://github.com/adafruit/DHT-sensor-library

You will need to put your username and password for your wireless network by updating these lines

const char* ssid = “username”;
const char* password = “password”;

#include <WiFi.h>
#include "DHT.h"

// Uncomment one of the lines below for whatever DHT sensor type you're using!
#define DHTTYPE DHT11 // DHT 11

// Replace with your network credentials
const char* ssid = "username";
const char* password = "password";

WiFiServer server(80);

// DHT Sensor
const int DHTPin = A13;
// Initialize DHT sensor.
DHT dht(DHTPin, DHTTYPE);

// Temporary variables
static char celsiusTemp[7];
static char fahrenheitTemp[7];
static char humidityTemp[7];

// Client variables
char linebuf[80];
int charcount=0;

void setup() {
// initialize the DHT sensor
dht.begin();

//Initialize serial and wait for port to open:
Serial.begin(115200);
while(!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}

// We start by connecting to a WiFi network
Serial.println();
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);

WiFi.begin(ssid, password);

// attempt to connect to Wifi network:
while(WiFi.status() != WL_CONNECTED) {
// Connect to WPA/WPA2 network. Change this line if using open or WEP network:
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("WiFi connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());

server.begin();
}

void loop()
{
// listen for incoming clients
WiFiClient client = server.available();
if (client)
{
Serial.println("New client");
memset(linebuf,0,sizeof(linebuf));
charcount=0;
// an http request ends with a blank line
boolean currentLineIsBlank = true;
while (client.connected())
{
if (client.available())
{
char c = client.read();
Serial.write(c);
//read char by char HTTP request
linebuf[charcount]=c;
if (charcount<sizeof(linebuf)-1) charcount++;
// if you've gotten to the end of the line (received a newline
// character) and the line is blank, the http request has ended,
// so you can send a reply
if (c == '\n' && currentLineIsBlank)
{
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float h = dht.readHumidity();
// Read temperature as Celsius (the default)
float t = dht.readTemperature();
// Read temperature as Fahrenheit (isFahrenheit = true)
float f = dht.readTemperature(true);
// Check if any reads failed and exit early (to try again).
if (isnan(h) || isnan(t) || isnan(f))
{
Serial.println("Failed to read from DHT sensor!");
}
else{
// Computes temperature values in Celsius + Fahrenheit and Humidity
float hic = dht.computeHeatIndex(t, h, false);
dtostrf(hic, 6, 2, celsiusTemp);
float hif = dht.computeHeatIndex(f, h);
dtostrf(hif, 6, 2, fahrenheitTemp);
dtostrf(h, 6, 2, humidityTemp);
}

// send a standard http response header
client.println("HTTP/1.1 200 OK");
client.println("Content-Type: text/html");
client.println("Connection: close"); // the connection will be closed after completion of the response
client.println();
client.println("<!DOCTYPE HTML><html><head><meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">");
client.println("<meta http-equiv=\"refresh\" content=\"2\"></head>");
client.println("<body><h1><p>ESP32 DHT11 example</h1><p>");

client.println(celsiusTemp);
client.println("*C</p><p>");
client.println(fahrenheitTemp);
client.println("*F</p><p>");
client.println(humidityTemp);
client.println("%</p>");
client.println("</body></html>");
break;
}
if (c == '\n')
{
// you're starting a new line
currentLineIsBlank = true;
memset(linebuf,0,sizeof(linebuf));
charcount=0;
}
else if (c != '\r')
{
// you've gotten a character on the current line
currentLineIsBlank = false;
}
}
}
// give the web browser time to receive the data
delay(1);
// close the connection:
client.stop();
Serial.println("client disconnected");
}
}

 

Output

Open the serial monitor and you should get the assigned IP address, once you get this paste this into your browser and all going well you should see something like this, the code is designed to refresh the page every 2 seconds

Link

DHT11 Temperature and Relative Humidity Sensor Module With Cable for Arduino

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Code

ESP32 and DHT11 sensor example

by shedboy71

DHT11 digital temperature and humidity sensor is a composite Sensor contains a calibrated digital signal output of the temperature and humidity.

Application of a dedicated digital modules collection technology and the temperature and humidity sensing technology, to ensure that the product has high reliability and excellent long-term stability.

The sensor includes a resistive sense of wet components and an NTC temperature measurement devices, and connected with a high-performance 8-bit microcontroller

dht11 module

dht11 module

Low cost, long-term stability, relative humidity and temperature measurement, excellent quality, fast response, strong anti-interference ability, long distance signal transmission, digital signal output, and precise calibration.

Parts Required

Here are the parts I used

 

Name Link
ESP32
DHT11
Connecting cables

Schematic

By using a module this avoids the need to build this on a breadboard

lolin32 and dht11

lolin32 and dht11

Code

You need to add the DHT11 library from adafruit to the Arduino IDE – https://github.com/adafruit/DHT-sensor-library

#include "DHT.h"
//here we use 14 of ESP32 to read data
#define DHTPIN A13
//our sensor is DHT11 type
#define DHTTYPE DHT11
//create an instance of DHT sensor
DHT dht(DHTPIN, DHTTYPE);

void setup()
{
Serial.begin(115200);
Serial.println("DHT11 sensor!");
//call begin to start sensor
dht.begin();
}

void loop() {
//use the functions which are supplied by library.
float h = dht.readHumidity();
// Read temperature as Celsius (the default)
float t = dht.readTemperature();
// 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;
}
// print the result to Terminal
Serial.print("Humidity: ");
Serial.print(h);
Serial.print(" %\t");
Serial.print("Temperature: ");
Serial.print(t);
Serial.println(" *C ");
//we delay a little bit for next read
delay(2000);
}

 

Output

Open the serial monitor and you should see something like this

Humidity: 23.00 % Temperature: 24.00 *C
Humidity: 23.00 % Temperature: 24.00 *C
Humidity: 24.00 % Temperature: 24.00 *C
Humidity: 24.00 % Temperature: 25.00 *C
Humidity: 24.00 % Temperature: 25.00 *C
Humidity: 25.00 % Temperature: 25.00 *C
Humidity: 29.00 % Temperature: 26.00 *C
Humidity: 29.00 % Temperature: 26.00 *C
Humidity: 29.00 % Temperature: 26.00 *C
Humidity: 28.00 % Temperature: 27.00 *C
Humidity: 29.00 % Temperature: 27.00 *C

 

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