HR202 Humidity Sensor Module – 3-Pin, for Smart Cars & Robotics

Description

The HR202 Humidity Sensor Module 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 a clean digital output when ambient humidity crosses a user-adjustable threshold .

The HR202L sensor offers a wide humidity detection range with ±5% RH accuracy and good long-term stability (≤1% RH/year drift) . Unlike capacitive humidity sensors, the HR202L is a resistive element whose resistance changes with humidity. The module’s comparator circuit converts this resistance change into a digital HIGH/LOW signal, with an onboard potentiometer allowing threshold adjustment .

The module operates from 3.3V to 5V, making it compatible with Arduino, ESP32, and most hobbyist platforms. The 3-pin version provides digital output (DO) only—when humidity exceeds the set threshold, the DO pin changes state and the onboard indicator LED illuminates . This makes it suitable for simple humidity-triggered applications such as condensation detection, enclosure monitoring, and smart car windshield fogging alerts.

Critical limitations: This is a budget-tier sensor with limited accuracy (±5% RH in the 20–90% range, with interpolated values outside this range) . It is not a precision hygrometer. The raw HR202L element requires AC excitation (not DC) 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

• Low-Cost Humidity Detection: HR202L organic polymer resistive element provides basic humidity sensing at a very low price point .

• Digital Output with Adjustable Threshold: LM393 comparator with onboard potentiometer sets the humidity trigger point .

• Wide Operating Voltage (3.3–5V): Compatible with Arduino, ESP32, and most 3.3V/5V systems .

• Indicator LEDs: Power LED and output-state LED provide visual feedback during calibration .

• Compact PCB with Mounting Holes: Small footprint (approximately 3.2×1.4cm) with fixed bolt holes for easy installation .

• Good Long-Term Stability: HR202L rated for ≤1% RH/year drift under proper operating conditions .

• Fast Response: Moisture absorption response ≤20s, dehumidification ≤40s .

• No Heating Required: Unlike some humidity sensors, the HR202L does not require a heater for operation .

Technical Specifications