The goal here is to build a system that collects temperature and humidity data using the DHT22 sensor and sends it to an InfluxDB server for storage and analysis, together with a Grafana server. The ESP32 acts as the bridge, connecting the sensor to Wi-Fi and managing communication with InfluxDB.
Required Hardware
- ESP32 — Microcontroller with built-in Wi-Fi and Bluetooth.
- DHT22 — Low-cost temperature and humidity sensor.
- Wi-Fi connection — Required for sending the data.
Pinout
DHT22 sensor:
- VCC: 3.3V from the ESP32
- GND: ESP32 GND
- DHTPIN: GPIO configured in code (set to
18)
Project Setup in VSCode with PlatformIO
[env:upesy_wroom]
platform = espressif32
board = upesy_wroom
framework = arduino
lib_deps =
adafruit/DHT sensor library@^1.4.6
arduino-libraries/NTPClient@3.1.0
tobiasschuerg/ESP8266 Influxdb@^3.13.1
Source Code Analysis
DHT22 Declaration
#include <Adafruit_Sensor.h>
#include <DHT.h>
#define DHTPIN 18
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);
Wi-Fi Connection
#include <WiFi.h>
#include <WiFiUdp.h>
const char* ssid = "MY_WIFI";
const char* password = "MY_PASSWORD";
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(2500);
Serial.println("Connecting to WiFi...");
}
Serial.println("Connected to WiFi");
InfluxDB Declaration and Initialization
#include <InfluxDbClient.h>
#define INFLUXDB_URL "http://influx.mfs.eng.br:8086"
#define INFLUXDB_DB_NAME "clima"
#define INFLUXDB_USER "esp32"
#define INFLUXDB_PASSWORD "esp32_password"
InfluxDBClient client(INFLUXDB_URL, INFLUXDB_DB_NAME);
Point sensor("clima");
client.setConnectionParamsV1(INFLUXDB_URL, INFLUXDB_DB_NAME,
INFLUXDB_USER, INFLUXDB_PASSWORD);
Collecting Data from the DHT22
float tempValue = dht.readTemperature();
float humidityValue = dht.readHumidity();
if (!isnan(tempValue) && !isnan(humidityValue)) {
Serial.print("Temperature: ");
Serial.println(tempValue);
Serial.print("Humidity: ");
Serial.println(humidityValue);
}
Sending Data to InfluxDB
sensor.clearFields();
sensor.addField("temperature", tempValue);
sensor.addField("humidity", humidityValue);
if (!client.writePoint(sensor)) {
Serial.print("InfluxDB write failed: ");
Serial.println(client.getLastErrorMessage());
}
InfluxDB Advantages
- Time-series database — ideal for continuous data.
- Scalability — handles large data volumes well.
- Seamless Grafana integration.
Visualization in Grafana
Example dashboard:
Link to the Grafana dashboard
Complete Code
Project repository:
https://gitlab.com/mfs.eng.br/hardware-quirks/temperatura_esp32
#include <Arduino.h>
#include <Adafruit_Sensor.h>
#include <DHT.h>
#include <WiFi.h>
#include <NTPClient.h>
#include <WiFiUdp.h>
#include <InfluxDbClient.h>
#include "config.h"
// Full code omitted here — included in the repository