XH-M131 Light Sensor Module Photo Resistor Relay 5V-24V Automatic Light Control Switch

XH-M131 light sensor module with photo resistor and relay. Wide voltage 5V-24V. Automatically turns light on/off based on ambient brightness. Adjustable sensitivity, NO/NC output. Ideal for street light control, hallway lighting, automatic switch, smart home retrofit

XH-M131 Light Sensor Module Application features:

◆ Core Components
Photo resistor (LDR) + Relay

◆ Supply Voltage
DC 5V – 24V (wide voltage range)

◆ Output
Relay NO (Normally Open) / NC (Normally Closed) contacts

◆ Load Capacity

• Max current: 10A

• Max voltage: AC 250V / DC 30V

◆ Sensitivity Adjustment
Onboard potentiometer to adjust trigger brightness threshold

◆ Operating Modes

• Bright condition: relay OFF or ON (adjustable)

• Dark condition: relay ON or OFF (adjustable)

◆ Typical Applications

• Automatic street light control

• Hallway lighting control

• Light-controlled night light

• Solar lighting system

• Smart home retrofit

• Security system integration

◆ Key Advantages

• Wide voltage supply (5V-24V)

• No microcontroller programming required

• Adjustable sensitivity

• High load capacity (10A)

• Plug-and-play

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Quantity(Pieces)	1 ~ 30000	30001 ~ 300000	> 300000
Est. Time(days)	5	7	To be negotiated

FAQ

1. What is the XH‑M131 light sensor module and its key specifications?
The XH‑M131 is a compact automatic light‑control switch module that uses a photoresistor (LDR) to detect ambient light level and activates a relay based on a user‑adjustable threshold. It can be configured for light‑on or light‑off operation. Key specifications include:

• Sensor: external photoresistor (LDR) with 50 cm cable.
• Relay output: 1‑channel, 10 A / 250 V AC, 10 A / 30 V DC, SPDT (NO, COM, NC).
• Operating voltage: 5 V – 24 V DC (wide input range).
• Adjustment: on‑board potentiometer to set the light threshold.
• Operation modes: selectable "light‑on" (relay closes when dark) or "light‑off" (relay closes when bright) via a jumper.
• Indicators: red LED for power, green LED for relay status.
• Dimensions: approx. 50 mm × 26 mm × 19 mm.

2. How do I connect the XH‑M131 module to a power supply and load?
Wiring is straightforward. Connect a 5 V – 24 V DC power supply to the VCC (+) and GND (-) terminals. The relay output provides NO (normally open), COM (common), and NC (normally closed) contacts. To control a load (light, fan, alarm), wire the power source to COM and the load to NO (for a circuit that closes when the relay is active) or NC (for a circuit that opens when active). The external LDR sensor connects to the dedicated 2‑pin terminal (non‑polarised). After wiring, adjust the threshold using the on‑board potentiometer. Always ensure the load does not exceed the relay rating (10 A / 250 V AC).

3. How do I set the light threshold and choose the operating mode (light‑on vs. light‑off)?
The threshold is set by the on‑board potentiometer. Turn it clockwise to require more light to trigger (or more darkness, depending on mode), and counter‑clockwise to require less. The operating mode is selected by a jumper (or solder bridge) on the board: one position makes the relay energise when the environment is dark (light‑on), the other when it is bright (light‑off). To calibrate, place the sensor in the desired light condition and slowly turn the pot until the green status LED just turns on or off. The red LED indicates power is present.

4. What type of relay does the XH‑M131 use, and what loads can it switch?
The module uses a single‑pole double‑throw (SPDT) mechanical relay rated for 10 A at 250 V AC or 10 A at 30 V DC. This allows direct switching of mains‑powered devices such as incandescent bulbs, LED drivers, fans, solenoid valves, and small motors. For inductive loads (motors, transformers), the current must be derated, and a snubber circuit or MOV should be placed across the contacts to suppress voltage spikes. The relay contacts are galvanically isolated from the control circuit, providing safety and noise immunity.

5. What is the operating voltage range, and can I power the module from a battery?
The XH‑M131 accepts a wide DC input voltage of 5 V to 24 V. This makes it compatible with common power supplies such as 5 V USB adapters, 12 V lead‑acid batteries, 24 V industrial rails, and 3‑series or 6‑series Li‑Ion packs. The module's control circuit draws very little current (typically 10 mA – 20 mA, plus relay coil current when active). For battery‑powered applications, ensure the battery voltage stays within the rated range. The module does not have reverse‑polarity protection, so always double‑check the wiring before applying power.

6. How does the photoresistor (LDR) sensor work, and what is its detection range?
The photoresistor is a passive component whose resistance decreases with increasing light intensity. The XH‑M131 measures this resistance via a voltage divider and compares it to the potentiometer‑set reference. The sensor is sensitive to visible light and some near‑infrared, with a typical dark resistance of several megohms and a bright‑light resistance of a few hundred ohms. The module can detect a wide range of ambient light levels, from direct sunlight to dim indoor lighting. The sensor cable can be extended up to several meters using standard two‑core wire; for best noise immunity, use a twisted pair and avoid running it parallel to AC power cables.

7. Can I use the XH‑M131 to automatically turn on lights at dusk and off at dawn?
Yes, this is the most typical application. Set the module to "light‑on" mode (relay closes when dark). Place the sensor where it can see the natural ambient light but is shielded from artificial light sources (e.g., streetlights) to prevent feedback. Adjust the threshold so the relay activates at the desired darkness level. When dusk falls, the sensor resistance rises, the module triggers the relay, and the connected light turns on. At dawn, the light level increases, the relay de‑energises, and the light turns off. A small delay (hysteresis) is inherent in the comparator circuit, preventing rapid on/off cycling during twilight.

8. What is the difference between the XH‑M131 and other light‑sensor relay modules?
The XH‑M131 is distinguished by its wide voltage range (5 V – 24 V), selectable light‑on/light‑off modes, and an external LDR sensor that can be placed away from the control board. Many simpler modules operate only at 5 V or 12 V, have a fixed mode, or use an on‑board photodiode that cannot be positioned remotely. The XH‑M131 also features a robust 10 A relay, making it suitable for direct control of mains‑powered lighting without an external contactor. For applications that require a digital output instead of a relay, a simple LM393‑based light sensor module may be more appropriate.

9. Why is my XH‑M131 module not switching or behaving erratically?
Common causes and solutions:

• Threshold misadjusted: readjust the potentiometer; try turning it fully clockwise and counter‑clockwise to find the switching point.
• Wrong mode jumper: check that the mode jumper is set correctly for your application (light‑on or light‑off).
• Sensor exposed to interfering light: ensure the LDR is not seeing its own controlled light (feedback loop). Shield the sensor or point it away from the controlled light.
• Power supply noise: add a 100 µF electrolytic capacitor across VCC and GND near the module.
• Relay chattering: this can happen if the ambient light level is exactly at the threshold. Slightly adjust the potentiometer to move the threshold away from the ambient level, or add a larger hysteresis by modifying the feedback resistor (if comfortable with soldering).

10. What are the most typical applications for the XH‑M131 light sensor module?
It is widely used in automatic street‑light controllers, garden and pathway lighting, chicken coop door openers, aquarium lighting timers, hallway and staircase lights, energy‑saving office lighting, and any project that requires automatic switching based on ambient light. Its simple setup, wide voltage range, and robust relay make it a favourite for both hobbyist home‑automation projects and small‑scale industrial control.