ESP8266 SHT31 Humidity Temperature Monitoring on Thingspeak

In this post we will
interface SHT31 Humidity & Temperature Sensor with NodeMCU ESP8266
Board. Thus using
Nodemcu ESP8266 & SHT31
, we will monitor the temperature and humidity data online on thingspeak.
Overview
There are various humidity & temperature sensors like
DHT11
&
HTU21D
. But while talking about the accuracy none of them are suitable for industrial level temperature humidity monitoring due to the
accuracy
and
precision
. They have poor accuracy as well as
sensitivity
. So here we will use the
SHT31 Temperature/Humidity sensor
. They are the
finest
&
highest-accuracy devices
you can get. It is a
digital sensor
with an
I2C interface
which makes for easy reading of humidity and temperature. The SHT31 sensor has an excellent
±2% relative humidity
and
±0.3°C
temperature accuracy for most uses.
In this project we will
interface SHT31 Temperature/Humidity Sensor with Nodemcu ESP8266
. We will send data to
Thingspeak Server
. ThingSpeak is an open-source Internet of Things application and API to store and retrieve data from things using the
HTTP
and
MQTT protocol
over the Internet or via a Local Area Network.
If you want to learn more about SHT31 you can check our earlier post:

Interfacing SHT3x Humidity & Temperature Sensor with Arduino

ESP32 SHT31 Temperature & Humidity Monitor on Web Server
Bill of Materials
Following are the components required for this simple IOT project. All the components can be easily purchased from Amazon. The component purchase link is given below.
S.N.
Components
Quantity
Purchase Links

NodeMCU ESP8266

Amazon
AliExpress

SHT31 Sensor

Amazon
AliExpress

Connecting Wires

Amazon
AliExpress

Breadboard

Amazon
AliExpress
SHT31 Humidity Temperature Sensor
SHT31
is the next generation of
Sensirion’s temperature and humidity sensors
. The SHT31 has increased intelligence, reliability, and improved accuracy specifications compared to its predecessor. Its functionality includes enhanced signal processing, temperature, and humidity that can be read out using
I2C communications
. This I2C Mini Module makes it easy to read temperature and humidity using our standardized sensor footprint. Plug into a Particle interface module for cloud access from anywhere in the world.
All I2C Mini Modules are designed to operate at
5V DC
. Using a convenient
4-Pin
plug, devices can be daisy-chained onto the I2C Bus, eliminating the need for soldering. Simply plug together the devices you need for your next
automation application
Features of SHT31 Sensor
1. Dual Purpose Temperature and Humidity Sensor
2. Accuracy of
±2%
Relative Humidity

0-100%
Humidity Sensing Range

-40 to +125°C (-40 to +257°F)
Operating Temperature

8-Second
Sensor Response Time

0x44
Start Address
7. Modular SHT31 breakout board
Schematic: Interfacing SHT31 with Nodemcu ESP8266
Here is the
schematic
for
Interfacing SHT31 Humidity Temperature Sensor with Nodemcu ESP8266
Connect the
VCC
pin of SHT31 to
3.3V
of ESP8266 & GND to GND. Connect the
SCL
&
SDA
pin of SHT31 to ESP38266
SCL (D1)
&
SDA (D2)
pin respectively as shown in the figure above.
Setting Up Thingspeak
Go to
https://thingspeak.com/
and create an account if you do not have one. Login to your account if you have already.
Create a new channel by clicking on the Create button. Enter basic details of the channel like field 1 & field2. Then Scroll down and save the channel.
Then go to API keys copy and paste this key to a separate notepad file. You will need it later while programming.
Source Code/Program
The source code for
Interfacing SHT31 with NodeMCU ESP8266
is given below. You can copy this code and upload it to
ESP8266 Board
. But before that you need library for SHT31 Sensor. So download the
library
from the link below.
Download SHT31 Library

#include <ESP8266WiFi.h>
#include <Arduino.h>
#include <Wire.h>
#include "Adafruit_SHT31.h"
String
apiKey
=
"PW3AKTNO270BFQGT"
;
// Enter your Write API key from ThingSpeak
const
char
*
ssid
=
"BYNARK"
;
// replace with your wifi ssid and wpa2 key
const
char
*
pass
=
"bynark@123"
;
const
char
*
server
=
"api.thingspeak.com"
;
WiFiClient
client
;
Adafruit_SHT31
sht31
=
Adafruit_SHT31
(
)
;
void
setup
(
)
{
Serial
begin
(
115200
)
;
while
(
!
Serial
)
delay
(

)
;
// will pause Zero, Leonardo, etc until serial console opens
Serial
println
(
"Connecting to "
)
;
Serial
println
(
ssid
)
;
WiFi
begin
(
ssid
pass
)
;
while
(
WiFi
status
(
)
!=
WL_CONNECTED
)
{
delay
(

)
;
Serial
(
"."
)
;
}
Serial
println
(
""
)
;
Serial
println
(
"WiFi connected"
)
;
Serial
println
(
"SHT31 test"
)
;
if
(
!
sht31
begin
(
0x44
)
)
// Set to 0x45 for alternate i2c addr
{
Serial
println
(
"Couldn't find SHT31"
)
;
while
(

)
delay
(

)
;
}
}
void
loop
(
)
{
float
t
=
sht31
readTemperature
(
)
;
float
h
=
sht31
readHumidity
(
)
;
if
(
client
connect
(
server

)
)
// "184.106.153.149" or api.thingspeak.com
{
String
sendData
=
apiKey
+
"&field1="
+
String
(
t
)
+
"&field2="
+
String
(
h
)
+
"\r\n\r\n"
;
//Serial.println(sendData);
client
(
"POST /update HTTP/1.1\n"
)
;
client
(
"Host: api.thingspeak.com\n"
)
;
client
(
"Connection: close\n"
)
;
client
(
"X-THINGSPEAKAPIKEY: "
+
apiKey
+
"\n"
)
;
client
(
"Content-Type: application/x-www-form-urlencoded\n"
)
;
client
(
"Content-Length: "
)
;
client
(
sendData
length
(
)
)
;
client
(
"\n\n"
)
;
client
(
sendData
)
;
}
if
(
!
isnan
(
t
)
)
// check if 'is not a number'
{
Serial
(
"Temp *C = "
)
;
Serial
println
(
t
)
;
}
else
{
Serial
println
(
"Failed to read temperature"
)
;
}
if
(
!
isnan
(
h
)
)
// check if 'is not a number'
{
Serial
(
"Hum. % = "
)
;
Serial
println
(
h
)
;
}
else
{
Serial
println
(
"Failed to read humidity"
)
;
}
Serial
println
(
)
;
delay
(
1000
)
;
}
Monitoring Data on Thingspeak
After uploading, open the
Serial Monitor
at a baud rate of
115200
. Press the ESP8266 reset button. The wifi connecting status should be printed in the serial monitor along with the humidity and temperature value.
Now you can go to
thingspeak private view
and check the data online. The data is updated to
thingspeak server
after the interval of 15 seconds.