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Humidity and Temperature Sensing

Si7021. Easy! Inexpensive!

filename: aht4humidSi7021.htm

September 2018: You could buy a humidity and temperature sensor breakout from Sparkfun for $7, plus p&p.

And it is easy to use.

Once you install Sparkfun's library, the code boils down to....

#include "SparkFun_Si7021_Breakout_Library.h"
#include <Wire.h>

float humidity = 0;
float tempf = 0;

Weather sensor;

//-------------------------------
void setup()
{
    Serial.begin(9600);
    sensor.begin();
}// End of setup()

//-------------------------------
void loop()
{
    getWeather();
    printInfo();
    delay(1000);
}//End of loop()

//-------------------------------
void getWeather()
{
  humidity = sensor.getRH();
  tempf = sensor.getTempF();
}//End of getWeather()

//-------------------------------
void printInfo()
{
//This function prints the weather data out to the default Serial Port

  Serial.print("Temp:");
  Serial.print(tempf);
  Serial.print("F, ");

  Serial.print("Humidity:");
  Serial.print(humidity);
  Serial.println("%");
}//End of printInfo()

A few minor "pay attentions" to notice... not "problems", unless you fail to notice...

a) 3v3 only... but I'm told it plays nicely via a level shifter if you want to use a 5v controller
b) Do not remove "the white thing" covering the sensor... little (3mm) black square. Notes about this ARE present in the Sparkfun hookup guide... if you read it!
c) You can only have one of these on a given I2C string. This is due to the address being hardcoded (0x40) into the chip. Not Sparkfun's fault!

Don't, by the way, be scared by the I2C. I know little about it, but had no problems. Be sure you connect SDA and SCL to the right pins on whatever microcontroller you are using.

Put humidity/ temperature data from Si7021 online with $16 ESP8266

The code of a webserver in an 8266 ($16... programmed with Arduino IDE)... is available. See my discussion of creating an inexpensive webserver ($16) to report data from sensors.

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In addition to the tutorials for which this page serves as Table of Contents, I have other sites with material you might find useful.....

Sequenced set of tutorials on Arduino programming and electronics interfacing.
Tutorials about the free database supplied with Open Office/ Libre Office.

Some pages for programmers.
Using the parallel port of a Windows computer.

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Click here to visit editor's Sheepdog Software (tm) freeware, shareware pages.. Material on this page © TK Boyd qDATE

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Click here to visit the homepage of my biggest site.

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Click here to visit editor's pages about using computers in Sensing and Control, e.g. weather logging.

To email this page's editor, Tom Boyd.... Editor's email address. Suggestions welcomed!

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