Wireless Data Logger

Wireless Data Logger

Image: AX3-electronics-enclosure-CC3.0.png by Open Movement -- the GitHub for the open source hardware ... via Wikimedia Commons, CC BY 3.0

How It Works

• A DHT11/DHT22 sensor takes temperature and humidity readings at a regular interval.
• An ESP8266/ESP32 connects to Wi-Fi and pushes each reading to a ThingSpeak channel via its REST API.
• ThingSpeak stores the incoming data over time and auto-generates live graphs, viewable from any browser without extra setup.
• Because storage and visualization happen in the cloud, there's no local card to retrieve and no risk of losing data if the device itself fails, as long as it uploaded before failing.

Components

ESP8266 or ESP32
DHT11/DHT22 temperature/humidity sensor
ThingSpeak account/channel (free tier)
Power supply

Applications

• Remote environmental monitoring
• Long-duration data collection for research/lab use
• Any application needing sensor history without a physical retrieval step

Advantages

• Live remote access to readings, no physical retrieval needed
• Automatic graphing and historical view built into the cloud platform
• Scales to multiple sensors/locations reporting to one dashboard

Sample Code — Uploading Sensor Data to ThingSpeak

// Simplified ThingSpeak data logger - ESP8266
#include 
#include 
#define DHTPIN 4
DHT dht(DHTPIN, DHT11);
String apiKey = "YOUR_THINGSPEAK_WRITE_KEY";

void setup() {
  Serial.begin(9600);
  dht.begin();
  WiFi.begin("SSID", "PASSWORD");
}

void loop() {
  float temp = dht.readTemperature();
  float hum = dht.readHumidity();

  WiFiClient client;
  if (client.connect("api.thingspeak.com", 80)) {
    String url = "/update?api_key=" + apiKey + "&field1=" + String(temp) + "&field2=" + String(hum);
    client.print(String("GET ") + url + " HTTP/1.1\r\nHost: api.thingspeak.com\r\n\r\n");
  }
  delay(60000); // ThingSpeak free tier: 1 update per 15s minimum, 60s is safe
}

Related Research

• Real-Time Data Communication with IoT Sensors and ThingSpeak Cloud — ResearchGate