Description
The Humidity-Sensitive Sensor Switch Electromagnetic Relay Module is a self-contained control board that automatically switches an electrical load based on ambient humidity. It combines a resistive humidity sensor (typically the HR202L) with a comparator circuit and an electromagnetic relay, allowing direct control of fans, heaters, dehumidifiers, or humidifiers without a microcontroller .
The module operates from 5V or 12V DC (selectable variant) and provides isolated relay contacts rated for 10A at 250V AC or 30V DC—sufficient for most household appliances and light commercial equipment . An onboard potentiometer sets the humidity threshold at which the relay activates. When ambient humidity crosses the set point, the relay pulls in (or drops out, depending on configuration), switching the connected load. Power and relay-status indicator LEDs provide visual feedback during calibration .
This module is suitable for individual makers building humidity-controlled projects (greenhouse ventilation, bathroom exhaust fans, terrarium misting) and for business purchasers seeking a cost-effective, standalone humidity switch for light commercial applications. Critical limitations: This is a budget-tier device with a resistive humidity sensor that is prone to drift and contamination over time. The relay provides no proportional control—it is on/off only. For applications requiring calibrated humidity measurement or proportional control, a digital sensor with a microcontroller is more appropriate.
Features
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Standalone Humidity-Controlled Switching: No microcontroller required; the module automatically switches loads based on ambient humidity .
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Isolated Relay Output: 10A @ 250V AC or 30V DC contact rating for direct control of fans, heaters, and small appliances .
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Adjustable Humidity Threshold: Onboard potentiometer sets the trigger point for relay activation .
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5V/12V Selectable Supply: Matches different power supply architectures .
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Indicator LEDs: Power LED (red) and relay-status LED (blue) for calibration feedback .
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Compact PCB with Mounting Holes: Approximately 50×26mm with 4× 3mm bolt holes for secure installation .
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Screw Terminal or Header Connections: For sensor input and relay output wiring.
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Low Cost: Inexpensive alternative to commercial humidistats for non-critical applications.
Technical Specifications
| Parameter | Specification (HR202-based relay module) |
|---|---|
| Sensing Element | HR202L resistive humidity sensor (verify with supplier) |
| Supply Voltage | DC 5V or 12V (selectable variant) |
| Supply Current | >150mA (some sources list >100mA) |
| Relay Contact Rating | 10A @ 250V AC or 30V DC |
| Humidity Threshold Adjustment | Onboard potentiometer |
| Relay Type | Electromagnetic, SPDT (COM/NO/NC) |
| Indicator LEDs | Power (red), Relay Status (blue) |
| PCB Dimensions | Approx. 50 × 26mm, 19mm height |
| Mounting | 4× 3mm bolt holes |
| Operating Temperature | 0°C to +60°C (typical for HR202) |
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