Description
The HR202 Humidity Sensor Module (4-Pin) is a compact, low-cost humidity detection board designed for environmental monitoring in smart car projects, robotics, and general DIY electronics. It uses the HR202L organic polymer humidity-sensitive resistor as the sensing element, combined with an LM393 comparator to provide both analog and digital outputs for flexible integration .
The 4-pin version is the most versatile variant in the HR202 module family. It provides a digital output (DO) that switches when ambient humidity crosses a user-adjustable threshold, plus an analog output (AO) that gives a continuous voltage proportional to humidity for more precise measurements via ADC . This dual-output design makes it suitable for both simple threshold-based switching (e.g., humidity alarms, fan control) and relative humidity trend monitoring.
The module operates from 3.3V to 5V, making it compatible with Arduino, ESP32, Raspberry Pi, and most hobbyist platforms . The onboard potentiometer allows threshold adjustment, and power/output indicator LEDs provide visual feedback during calibration. The compact PCB measures approximately 3.2 × 1.4 cm with mounting holes for easy installation .
Critical limitations: This is a budget-tier sensor with ±5% RH accuracy in the 20–95% RH range . It is not a precision hygrometer. The raw HR202L element requires AC excitation (1.5V max, sine wave) for long-term reliability, which the module handles internally, but the sensor is still prone to contamination-related drift over time. For applications requiring calibrated, stable humidity measurement, a capacitive digital sensor (DHT22, SHT31) is more appropriate.
Features
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Dual Outputs (DO + AO): Digital threshold signal plus analog voltage output for flexible integration .
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Adjustable Sensitivity: Onboard potentiometer sets the humidity trigger point for the digital output .
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Wide Operating Voltage (3.3–5V): Compatible with Arduino, ESP32, and most 3.3V/5V systems .
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LM393 Comparator: Provides clean, stable digital switching with drive capability >15mA .
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Indicator LEDs: Power LED (red) and digital output LED (green) for calibration feedback .
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Compact PCB with Mounting Holes: Approx. 3.2 × 1.4 cm with fixed bolt holes .
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Good Long-Term Stability: HR202L rated for ≤1% RH/year drift under proper operating conditions .
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Fast Response: Moisture absorption ≤20s, dehumidification ≤40s .
Technical Specifications
| Parameter | Specification (HR202L Element) |
|---|---|
| Sensing Element | HR202L organic polymer humidity resistor |
| Humidity Range | 20–95% RH (non-condensing) |
| Humidity Accuracy | ±5% RH |
| Operating Voltage (Module) | 3.3V – 5V DC |
| Output Type (4-Pin) | Digital (DO) + Analog (AO) |
| Comparator IC | LM393 |
| Response Time | ≤20s (absorption) / ≤40s (dehumidification) |
| Operating Temperature | 0°C to +60°C |
| PCB Size | Approx. 3.2 × 1.4 cm |
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