Temperature logger

Temperature logger with NodeMCU and DHT22

Here I will describe how to do a temperature logger using the NodeMCU and the DHT22 temperature and humidity reader.

The hardware

I used a NodeMCU board (ESP8266) like below:

And a DHT22 sensor like below:

The wiring

You need to connect these pins:

DHT22 OUT pin >> NodeMCU D2
DHT22 + pin >> NodeMCU 3V
DHT22 - pin >> NodeMCU GND

The code

I used Arduino IDE to make the code. You need to setup the IDE to use a NodeMCU board. You can see more details here.

The NodeMCU code is very simple:

#include <Arduino.h>
#include <DHT.h>
#include <ESP8266WiFi.h>
#include <ESP8266WiFiMulti.h>
#include <ESP8266HTTPClient.h>

ESP8266WiFiMulti WiFiMulti;

#define DHTPIN D2     // what pin the DHT sensor is connected
#define DHTTYPE DHT22   // DHT 22  (AM2302)
DHT dht(DHTPIN, DHTTYPE); //// Initialize DHT sensor

int chk;
float hum;  //For humidity value
float temp; //For temperature value

unsigned long lastConnectionTime = 0;         // last time we connected to the server, in milliseconds
const unsigned long postingInterval = 60000L; // delay between updates, in milliseconds

void setup() // We write some things to the serial, for debug purposes
{
  Serial.begin(115200);
  dht.begin();
    for(uint8_t t = 4; t > 0; t--) {
        Serial.printf("[SETUP] WAIT %d...\n", t);
        Serial.flush();
        delay(1000);
    }

WiFi.mode(WIFI_STA);
    WiFiMulti.addAP(<<YOUR SSID>>, <<YOUR PASSWORD>>);
    delay(2000);
}

void loop()
{

if (millis() - lastConnectionTime > postingInterval) {
      lastConnectionTime = millis();
      //Read data and store it to variables hum and temp
      hum = dht.readHumidity();
      temp= dht.readTemperature();
      //Print temp and humidity values to serial monitor
      Serial.print("Humidity: ");
      Serial.print(hum);
      Serial.print(" %, Temp: ");
      Serial.print(temp);
      Serial.println(" Celsius");
      httpRequest();
    }
}

void httpRequest() {
  if((WiFiMulti.run() == WL_CONNECTED)) {
    HTTPClient http;
    Serial.print("[HTTP] begin...\n");
    String command = "<<YOUR URL>>/templogger.php?device_serial=<<YOUR DEVICE SERIAL>>";
    command += "&temp=";
    command += temp;
    command += "&hum=";
    command += hum;
    http.begin(command);
    
// Make a GET request
    Serial.print("[HTTP] GET...\n");
    int httpCode = http.GET();
    if(httpCode > 0) {
      Serial.printf("[HTTP] GET... code: %d\n", httpCode);
      if(httpCode == HTTP_CODE_OK) {
        String payload = http.getString();
        Serial.println(payload);
      }
    } else {
      Serial.printf("[HTTP] GET... failed, error: %s\n", http.errorToString(httpCode).c_str());
    }
    http.end();
  }
}

Then you need to create two files. One to push the values to the MySQL database, and other to show the values on the web:

<?php>

$con = mysql_connect("localhost",<<YOUR USERNAME>>,<<YOUR PASSWORD>>);
if (!$con) {
		die('Connection error: ' . mysql_error());
	}
  mysql_select_db(<<YOUR DATABASE>>, $con) or die(mysql_error());
  mysql_query("SET NAMES 'utf8'");
  mysql_query('SET character_set_connection=utf8');
  mysql_query('SET character_set_client=utf8');
  mysql_query('SET character_set_results=utf8');

// Checks if we have a device serial
if (isset($_GET['device_serial'])) {

$temp = $_GET['temp'];
  $hum = $_GET['hum'];
  ConnectDB();

$device_serial = $_GET['device_serial'];
  //echo "DEBUG device_id: ".$device_id."<br>";

// Checks if the device serial is registered
  $result = mysql_query("SELECT device_id FROM tb_device WHERE device_serial='$device_serial'") or die(mysql_error());

$rowCount = mysql_num_rows($result);

if ($rowCount < 1) {
    echo "Device not found<br>";
    exit;
  }
  else {
// Push data to the table
    if (($temp != 0) && ($hum != 0)) {
      $result = mysql_query("INSERT INTO tb_templogger (temp, hum, device_serial, datetime) values ('$temp', '$hum', '$device_serial', NOW())");
    }
  }
}
?>

<?php>
$con = mysql_connect("localhost",<<YOUR USERNAME>>,<<YOUR PASSWORD>>);
if (!$con) {
		die('Connection error: ' . mysql_error());
	}
  mysql_select_db(<<YOUR DATABASE>>, $con) or die(mysql_error());
  mysql_query("SET NAMES 'utf8'");
  mysql_query('SET character_set_connection=utf8');
  mysql_query('SET character_set_client=utf8');
  mysql_query('SET character_set_results=utf8');

//Checks if we have a device serial
if (isset($_GET['device_serial'])) {

ConnectDB();

$device_serial = $_GET['device_serial'];
  //echo "DEBUG device_id: ".$device_id."<br>";

$result = mysql_query("SELECT device_id FROM tb_device WHERE device_serial='$device_serial'") or die(mysql_error());

$rowCount = mysql_num_rows($result);

if ($rowCount < 1) {
    echo "Device not found<br>";
    exit;
  }
  else {
    echo "<meta http-equiv='refresh' content='60'>"; // Updates the page every minute
    echo "<body bgcolor='#000000'>";
    echo "<style>TD{font-family: Arial; font-size: 30pt; color: green;}</style>";
    echo "<br><br>";
    $result = mysql_query("SELECT temp, hum, datetime FROM tb_templogger WHERE device_serial='$device_serial' ORDER BY datetime DESC LIMIT 1"); // Get the LAST record

while($row = mysql_fetch_array($result)) {
			$temp = $row['temp'];
			$hum = $row['hum'];
			$datetime = $row['datetime'];
      echo "<center><font face='Arial' color='yellow' size='4'>";
      echo "<h1>Actual Temp: ".$temp."ºC       Hum: ".$hum."%</h1></br>";
      echo "</font></center";
    }

$result = mysql_query("SELECT temp, hum, datetime from tb_templogger WHERE device_serial='$device_serial' ORDER BY temp DESC LIMIT 1"); // Get the highest temp value record

while($row = mysql_fetch_array($result)) {
			$temp = $row['temp'];
			$hum = $row['hum'];
			$datetime = $row['datetime'];
      echo "<center><font face='Arial' color='red' size='2'>";
      echo "<h1>Max Temp: ".$temp."ºC       Hum: ".$hum."%       Date: ".$datetime."</h1></br>";
      echo "</font></center";
    }

$result = mysql_query("SELECT temp, hum, datetime from tb_templogger WHERE device_serial='$device_serial' ORDER BY temp LIMIT 1"); // Get the lowest temp value record

while($row = mysql_fetch_array($result)) {
			$temp = $row['temp'];
			$hum = $row['hum'];
			$datetime = $row['datetime'];
      echo "<center><font face='Arial' color='blue' size='2'>";
      echo "<h1>Min Temp: ".$temp."ºC       Hum: ".$hum."%       Date: ".$datetime."</h1></br>";
      echo "</font></center>";
    }

}
}
?>

Finally, we need to create the MySQL tables:

TABLE TB_DEVICE

CREATE TABLE IF NOT EXISTS `tb_device` (
  `device_id` int(11) NOT NULL,
  `device_serial` varchar(50) COLLATE utf8_unicode_ci NOT NULL,
  `device_name` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
  `device_feed_limit` int(11) NOT NULL,
  `device_ssid` varchar(100) COLLATE utf8_unicode_ci DEFAULT NULL,
  `device_pwd` varchar(100) COLLATE utf8_unicode_ci DEFAULT NULL,
  `device_auth` int(11) NOT NULL,
  `config_changed` int(11) NOT NULL
) ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

ALTER TABLE `tb_device`
  ADD PRIMARY KEY (`device_id`);

ALTER TABLE `tb_device`
  MODIFY `device_id` int(11) NOT NULL AUTO_INCREMENT,AUTO_INCREMENT=1;

TABLE TB_TEMPLOGGER

CREATE TABLE IF NOT EXISTS `tb_templogger` (
  `id_log` int(11) NOT NULL,
  `device_serial` varchar(50) COLLATE utf8_unicode_ci NOT NULL,
  `temp` float NOT NULL,
  `hum` float NOT NULL,
  `datetime` datetime NOT NULL
) ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

ALTER TABLE `tb_templogger`
  ADD PRIMARY KEY (`id_log`);

ALTER TABLE `tb_templogger`
  MODIFY `id_log` int(11) NOT NULL AUTO_INCREMENT,AUTO_INCREMENT=1;

Live demo

You can see a live demo here. This device is located at Rio de Janeiro, Brazil.

I hope that you enjoy. If you want, contact-me.