HR202 Adjustable Humidity Detection Module with Relay

Description

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🌫️ HR202 Humidity Sensor Module + Relay

✅ General Description

The HR202 sensor is a capacitive hygrometer designed to measure the relative humidity of the air. Integrated into a module with a comparator and relay, it is perfect for automatic environmental monitoring projects, such as activating fans, dehumidifiers, or alarmswhen the humidity exceeds a certain threshold. Technical Specifications when the humidity exceeds a certain threshold.

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⚙️ Specification

Main Sensor	HR202 – Capacitive Humidity Sensor
Humidity Range	20% – 90% RH (approx.)
Humidity range	20% – 90% RH (approximately)
Operating Voltage	5V DC
Relay Output	Contact NO/NC (Normally Open/Closed)
Maximum Relay Current	10A 250VAC / 10A 30VDC
Status LED	ON when the relay is active
Potentiometer	Adjusts the activation threshold
Digital Output Type	HIGH/LOW (based on humidity level)
Compatibility	Arduino, ESP32, Raspberry Pi, STM32, etc.

📌 The module compares the sensor value with a adjustable threshold: if exceeded, activates the relay.

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🧰 How It Works

• The HR202 humidity sensor detects air humidity.
• A comparator (LM393) compares the read value with a adjustable threshold via trimmer.
• If the humidity exceeds (or falls below, depending on the setting) the threshold:
  • the relay activates/deactivates,
  • l’digital output (DO) changes state,
  • the status LED indicates activation.

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🔌 Connection with Arduino

HR202 module pin	Arduino Connection
VCC	5V
GND	GND
DO (Digital Output)	Ex. D2
COM (Relay Common)	to the load or power supply
NO / NC (Relay Output)	towards the controlled device

🧠 You can use only the output DO to read the state from Arduino or connect devices directly to the relay (fans, pumps, alarms…).

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🖥️ Arduino Programming

📜 Example Base – Humidity State Reading

const int pinHum = 2;

void setup() {
 Serial.begin(9600);
 pinMode(pinHum, INPUT);
}

void loop() {
 int stato = digitalRead(pinHum);
 if (stato == LOW) {
 Serial.println("Umidità SUPERIORE alla soglia – Relè ATTIVO");
 } else {
 Serial.println("Umidità INFERIORE alla soglia – Relè NON attivo");
 }
 delay(1000);
}

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⚡ Example: Fan Activation if Humidity > Threshold

const int sensoreHR = 2;
const int pinVentola = 8;

void setup() {
 pinMode(sensoreHR, INPUT);
 pinMode(pinVentola, OUTPUT);
 digitalWrite(pinVentola, LOW); // ventola spenta
}

void loop() {
 int umido = digitalRead(sensoreHR);
 if (umido == LOW) {
 digitalWrite(pinVentola, HIGH); // accendi ventola
 } else {
 digitalWrite(pinVentola, LOW); // spegni ventola
 }
}

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🔄 Direct Relay Use (Without Arduino)

You can power the module at 5V and let the relay activate automatically when the humidity exceeds the threshold, without microcontroller. The potentiometer allows for autonomous adjustment.

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📚 Common Applications

• 💨 Automatic Activation of Fans or Dehumidifiers
• 🌱 Environmental Control in Greenhouses or Grow Boxes
• 🏠 Home Automation Systems for Air Quality Monitoring 📦 Protection of Electronic Devices in Humid Environments
• 📦 Protection for electronic devices in humid environments

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🔧 Adjust the Threshold with the

• 🔧 Set the threshold with the trimmer based on the desired humidity level.
• 🛡️ Protect the module from condensation or splashes (not waterproof).
• 🧪 For quantitative readings, use a DHT22 sensor o BME280.

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📦 Advanced Extensions

Want to take it to the next level?

✅ LCD or OLED display to show the humidity level
📶 Wi-Fi (ESP8266/ESP32) to send data to the app or cloud
📁 SD card data logging of values and thresholds exceeded
📲 Smartphone App with Blynk, Telegram, or MQTT

✉️ Let me know if you want a complete project with these features!

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✅ Conclusion

The HR202 Module with relay is a simple and powerful solution for automatic humidity control.
With Arduino, you can easily automate reactions to humidity changes, turn on devices, o integrate into home automation systems.

Here is a complete project with Fritzing diagram, Wi-Fi inclusion (ESP8266/ESP32) for data transmission to smartphone and OLED or LCD display integrated circuits.

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🔧 1. Fritzing Schematic

A HR202 module is expected HR202 with analog output (AO) and digital (LM393 comparator + relay) connected to microcontroller:

• VCC → 5 V
• GND → GND
• DO (digital output) → digital pin (e.g., D2)
• AO (analog output) → analog pin (e.g., A0, if available)
• relay connected between COM e NO/NC to control a load (e.g., fan)

The typical Fritzing schema for similar IoT relay modules is available and can be used as a base (fritzing.org, openimpulse.com, arduitronics.com). You can easily place the sensor, microcontroller, and relay on the visual breadboard in the file .fzz.

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🌐 2. Version with ESP8266 / ESP32 and data sent to smartphone

Use a NodeMCU (ESP8266) or ESP32 connected to the HR202 module, reading the digital or analog output and displaying the data via local web page.

Simplified example:

#include <WiFi.h>
#include <WebServer.h>

const char* ssid = "SSID"; const char* pwd = "PASSWORD";
WebServer server(80);

#define HR_DO 2 // uscita digitale sensore HR202
#define HR_AO A0 // uscita analogica (solo su ESP32)

void handleRoot(){
 int digital = digitalRead(HR_DO);
 int analog = analogRead(HR_AO);
 String html = "<h1>Umidità ambiente</h1>";
 html += "Stato digitale (soglia): " + String(digital);
 html += "Valore analogico: " + String(analog);
 server.send(200, "text/html", html);
}

void setup(){
 Serial.begin(115200);
 WiFi.begin(ssid,pwd);
 while(WiFi.status()!=WL_CONNECTED) delay(500);
 server.on("/", handleRoot);
 server.begin();
 pinMode(HR_DO, INPUT);
}

void loop(){
 server.handleClient();
}

Then access the IP shown on Serial Monitor from your smartphone browser to see the real-time status (Arduino Forum).

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🖥️ 3. Project with OLED or LCD display

Integrate an OLED SSD1306 I2C OLED o 16×2 I2C LCD to show the instant reading.

Example with OLED:

#include <Wire.h>
#include <Adafruit_SSD1306.h>
#define OLED_ADDR 0x3C
Adafruit_SSD1306 oled(128,64,&Wire);

#define HR_AO A0

void setup(){
 Serial.begin(115200);
 oled.begin(SSD1306_SWITCHCAPVCC, OLED_ADDR);
 oled.clearDisplay();
}

void loop(){
 int val = analogRead(HR_AO);
 float humidity = map(val, 0, 4095, 0, 100); // ESP32 ADC range
 oled.clearDisplay();
 oled.setTextSize(2);
 oled.setCursor(0,0);
 oled.print("Umidita':");
 oled.setCursor(0,28);
 oled.print(humidity);
 oled.print("%");
 oled.display();
 delay(1000);
}

If you use an I2C LCD display, just replace the library with LiquidCrystal_I2C and adapt the commands.

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📝 Connection Summary

Function	Components	Main Connections
HR202 Sensor	DO → D2, AO → A0	To the ESP32 / ESP8266 microcontroller
Relay (digital only)	COM → power, NO → load	Direct device control
OLED I2C	SDA → D1, SCL → D2	Data Display
Wi-Fi	ESP8266 / ESP32	Local web server for smartphone access

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💡 Useful Tips

• 🎚️ Adjust trimmer on the HR202 module to set the desired digital threshold .
• 📊 The analog reading (AO) is only indicative; for precise values use sensors like DHT22/BME. 💧 HR202 is not waterproof: avoid direct condensation.
• ⚠️ If using relays for AC, insert
• fuses and protection diodes for safety ( arduitronics.com✅ In Conclusion).

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You now have a modular project that includes:

Fritzing diagram with HR202 module + relay.

• Fritzing schema with HR202 module + relay.
• ESP8266/ESP32 and web server ESP8266/ESP32 and web server to display data on smartphone.
• Live display on OLED or LCD display.

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GENERAL	MODEL	switch relay module humidity
MATERIALS	pcb + components
COMPATIBILITY	ARDUINO
ELECTRICAL COMPONENTS	INPUT VOLTAGE	5VDC
WEIGHT AND DIMENSIONS	PRODUCT WEIGHT	500g
PACKAGE WEIGHT	0.800 kg
PRODUCT DIMENSIONS (L x W x H)	6.5 x 2.5 x 2.7 cm
PACKAGE DIMENSIONS (L x W x H)	10 x 5 x 3 cm
PACKAGE CONTENTS	PACKAGE CONTENTS	1 x Module

We have datasheets available for all components, if not present in the product download sheet, send us a message via the contact us form and we will publish it as soon as possible on our website.

Tutorial: How to Use HR202 Sensor

The HR202 sensor measures ambient humidity and can control the relay. Useful for humidity and environmental control projects.

What you need

• Arduino or compatible
• Power cable
• Relay (optional)
• Multimeter (for verification)

Steps

1. 1. Installation: Download HR202 libraries on Arduino IDE.
2. 2. Connection: Connect VCC to 5V, GND to GND, SDA to A4, SCL to A5.
3. 3. Configure relay (if present): Connect relay VCC to 5V, relay GND to GND, and relay output to a digital pin.
4. 4. Code: Include HR202.h, initialize sensor and read humidity.
5. 5. Check: Use a multimeter to verify connections.
6. 6. Test: Run sketch to verify humidity reading.
7. 7. Relay adjustment: Set humidity threshold and connect relay.
8. 8. Test: Activate relay when humidity exceeds threshold.

Example code

```cpp
#include <HR202.h>

HR202 sensor;

void setup() {
 Serial.begin(9600);
 sensor.begin();
}

void loop() {
 float humidity = sensor.readHumidity();
 Serial.println(humidity);
}
```

Mini project

Create an automatic irrigation system with HR202 and relay.

Common mistakes

• Incorrect connections.
• Libraries not updated.
• Relay threshold not set correctly.

Recommended accessories

• Relay
• Power cable
• Multimeter
• Control panel

Frequently asked questions

The sensor does not correctly read humidity.
Check connections and code. Check power supply voltage.

How to adjust the relay?
Set the humidity threshold in the code and connect the relay output to a digital pin.

What are the operating temperature limits?
Check the datasheet for temperature limits.

Can I use HR202 with a microcontroller other than Arduino?
Check compatibility on the datasheet.