Temperature And Humidity Sensor GY-21 HTU21 SHT21

Features:

• High Precision: Offers accurate measurement of temperature and humidity.
• I2C Communication: Supports direct data reading via the I2C protocol.
• Versatile Integration: Suitable for thermostats, weather stations, and more.
• Wide Humidity Range: 0% to 100% RH.
• Extended Temperature Range: -40°C to 125°C.
• Accuracy: ±2% RH, ±0.3°C in the 0°C to 70°C range.
• Resolution Options: Adjustable precision for different applications.
• Compact Size: 21mm x 16mm for easy integration.
• Power Efficiency: Low current consumption, ideal for battery-powered devices.
• Enhanced Precision Mode: Higher resolution with longer measurement times.
• Integrated IC: Built around the SHT21 chip for consistent performance.

Principle of Work:

The SHT21 sensor uses a capacitive sensor for humidity and a band gap sensor for temperature. These analog signals are converted via a 14-bit ADC and communicated digitally over I2C. I2C enables simple two-wire communication (SDA & SCL) and supports multiple devices, multi-master configurations, and open-drain signaling for low power and noise immunity.

Pinout of the Board:

Applications:

1. Weather Stations: Accurate environmental monitoring.
2. HVAC Systems: Control indoor air quality.
3. Industrial Automation: Maintain factory conditions.
4. Agriculture: Optimize greenhouses and storage environments.
5. Food and Beverage: Ensure quality during storage.
6. Medical Devices: Support sensitive applications like incubators.
7. Data Centers: Prevent overheating and improve efficiency.
8. Automotive: Monitor cabin climate.
9. Consumer Electronics: Smart home and wearable integration.
10. R&D: Accurate measurements for experimental setups.
11. Energy Efficiency: Optimize building energy use.
12. Environmental Monitoring: Study ecosystems and climate.

Circuit Diagram:

Connect the SHT21 sensor to an Arduino UNO as follows:

• VCC → 3.3V
• GND → GND
• SDA → A4
• SCL → A5

Library Installation:

1. Download the SHT21 Arduino library.
2. Open Arduino IDE.
3. Go to Sketch > Include Library > Add .ZIP Library.
4. Select the downloaded .ZIP file.
5. Verify it appears under Sketch > Include Library.

Example Code:

#include "SHT21.h"
SHT21 sht;
float temperature;
float humidity;

void setup() {
  Wire.begin();
  Serial.begin(9600);
  Serial.println("SHT21 Sensor Data:");
}

void loop() {
  temperature = sht.getTemperature();
  humidity = sht.getHumidity();

  if (isnan(temperature) || isnan(humidity)) {
    Serial.println("Error reading data from sensor");
    return;
  }

  Serial.print("Temperature: ");
  Serial.print(temperature, 2);
  Serial.print(" °C\t");

  Serial.print("Humidity: ");
  Serial.print(humidity, 2);
  Serial.println(" %");

  delay(2000);
}

Technical Details:

• IC: SHT21
• Operating Voltage: 3V – 5V DC
• Current Consumption: 150mA
• Humidity Range: 0% – 100% RH
• Temperature Range: -40°C – 125°C
• Accuracy: ±2% RH, ±0.3°C
• Resolution: 0.04% RH, 0.01°C (Max)
• Module Size: 21mm x 16mm

Resources:

• Download the SHT21 Arduino Library
• Tutorial

Comparison with Other Modules: