Description
The 5V/12V Humidity Switch Relay Module (White) is a versatile, dual-voltage humidity controller designed for automation projects and environmental monitoring. Unlike single-voltage units, this white module accepts either 5V DC or 12V DC input, making it compatible with USB power banks, Arduino systems, PLCs, or standard 12V industrial supplies. The module features a high-sensitivity humidity sensor, a clean white LCD backlit display, and a robust relay output that switches external devices such as exhaust fans, humidifiers, dehumidifiers, water pumps, or alarm systems.
With a simple two-button interface, users can set an exact humidity trigger point and choose between humidification or dehumidification modes. The relay status is indicated by a bright LED, and the compact white enclosure offers a professional, clean appearance for both DIY hobbyist projects and commercial installations. Whether you need to maintain humidity inside a 3D printer filament storage box, a musical instrument cabinet, a reptile terrarium, or a warehouse drying room, this module provides a plug-and-play solution without requiring microcontroller programming.
Key Features
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Dual Voltage Support – Operates on either 5V DC (USB compatible) or 12V DC (industrial standard).
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Selectable Working Mode – Switch between Humidify (activates when air is too dry) and Dehumidify (activates when air is too wet).
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Built-in SPDT Relay – Controls devices up to 10A / 250V AC or 10A / 30V DC.
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Clear White Backlit Display – Shows real-time humidity percentage and relay status at a glance.
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External Humidity Probe – Place the sensor exactly where needed, away from heat sources.
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One-Touch Calibration – Reset sensor reading to match a reference hygrometer.
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Hysteresis Setting – Adjustable switching differential prevents rapid on/off cycling.
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Non-Volatile Memory – Retains all settings after power loss.
Technical Parameters
Usage Guide
Wiring Instructions
Step 1 – Power Connection
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5V application : Connect USB cable or 5V power supply to VCC (+) and GND (-) terminals.
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12V application : Connect 12V DC power supply to the same VCC (+) and GND (-) terminals.
(No jumper or switch required – the module auto-adapts.)
Step 2 – Load (Device) Connection
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COM (Common): Connect to your power source (AC or DC live/positive line).
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NO (Normally Open): Relay closes when humidity setpoint is reached. Connect to device input.
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NC (Normally Closed): Relay opens when humidity setpoint is reached. Use for reverse logic.
Step 3 – Sensor Placement
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Plug the included external humidity probe into the 3-pin header. Place the probe in the target environment, avoiding direct water spray, heat vents, or metal surfaces.
Programming Instructions
Configuration Steps:
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Power on the module. Display shows current humidity (e.g., “55%”).
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Press SET once – the trigger humidity value blinks. Use UP/DOWN to set desired %.
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Press SET again – the hysteresis (L) value blinks. Set 3–10% to prevent rapid switching.
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Press SET a third time – select mode:
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Wait 5 seconds – display stops blinking. Settings are saved.
Example (Misting Pump for Reptile Tank):
Q: Can I use a 9V battery or 24V power supply?
No. The module is designed strictly for 5V or 12V DC only. 9V may cause erratic behavior; 24V will permanently damage the components. Use a regulated 5V USB adapter or a 12V LED driver.
Q: How do I know if the module is in 5V or 12V mode?
The module automatically detects voltage. No indicator is needed. However, at 5V the relay coil draws slightly more current, but both voltages work identically.
Q: What is the difference between the white version and the blue version?
The white version supports dual voltage (5V/12V) and has a white backlight. The blue version is fixed 12V only. For USB-powered or battery-powered projects, choose the white version.
Q: Can I connect this directly to an Arduino or Raspberry Pi?
Yes. For Arduino (5V logic), connect 5V and GND from the Arduino to the module. Use an external power source for high-current devices – do not power a 10A load through the Arduino. For Raspberry Pi, use a separate 5V power supply (do not draw from Pi’s 5V pin for the relay coil).
Q: My display shows "---" or "LL". What is wrong?
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The external humidity probe is unplugged or loose. Reconnect to the 3-pin header.
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Humidity is below 10% (rare). Move probe to a more humid area to test.
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Sensor is defective – replace with a standard resistive humidity sensor (HR202 type).
Q: Does this module work for both residential and business use?
Yes.
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Home users: Cigar humidors, 3D printer filament dry boxes, guitar rooms, wine coolers, pet terrariums.
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Business users: Mushroom cultivation tents, printing press rooms, pharmaceutical storage, greenhouse climate control, server room dehumidification.
Q: How often does the relay switch?
The module samples humidity every 2 seconds. However, to protect your appliances, the relay will not switch more than once every 5 seconds, even if humidity fluctuates rapidly.
Q: Why does my relay click on and off too frequently?
Increase the hysteresis (L) value. For example, change from 3% to 8% or 10%. This creates a larger “deadband” between ON and OFF points.
Q: Can I use this to control a 12V DC water pump directly?
Yes. Connect the pump’s positive wire through COM and NO terminals. Connect the pump’s negative wire directly to your 12V power supply negative. The relay switches the positive line.
Q: Is the humidity sensor replaceable? Where can I buy it?
Yes. The sensor is a standard 3-pin resistive type (compatible with HR202, HM1500, or similar). You can find replacements online or at electronics component stores. Search “resistive humidity sensor module 3-pin”.
Q: How do I calibrate the sensor to match my reference hygrometer?
Press and hold the UP button for 10 seconds while the module is powered on. The display will flash “CA”. Use UP/DOWN to adjust the offset (±10%). Press SET to confirm. Place both sensors side by side for 30 minutes before calibrating.
