Photoresistor Sensor with 12V Relay Light Control Switch Module / Light-Seeking Detection Switch Board

Description

The Photoresistor Sensor with 12V Relay Light Control Switch Module is a standalone, light-activated relay board designed to automatically control electrical loads based on ambient brightness. It uses a photoresistor (LDR) to sense light intensity and an electromagnetic relay to switch the connected load—no microcontroller or programming is required .

The module operates from a 12V DC supply and provides isolated relay contacts rated for 10A at 250V AC or 30V DC, making it suitable for direct control of lamps, LED strips, fans, and small appliances . An onboard potentiometer sets the light threshold: when ambient light is darker than the threshold, the relay energizes and connects COM to NO; when light is brighter than the threshold, the relay de-energizes and COM connects to NC . This makes it ideal for automatic night lighting, street lamps, garden lights, and light-seeking detection applications.

The module includes optocoupler isolation to protect the control circuit and a 78L05 voltage regulator for stable operation . Power and relay-status indicator LEDs provide visual feedback. Many variants include a detachable LDR probe on a cable (typically 30cm), allowing the sensor to be positioned away from the module for accurate ambient light sampling .

Critical limitations: This is a budget-tier module with no calibration certificate. The photoresistor detects light from a wide angle, making it suitable for general ambient brightness detection but not for directional light-source seeking. The relay provides on/off switching only, not proportional dimming. User reports and design guides note that relay chatter can occur when light fluctuates near the threshold—some variants include adjustable delay to mitigate this . For applications requiring precise lux measurement or proportional control, a digital light sensor with a microcontroller is more appropriate.

Features

• Standalone Light-Activated Switching: No microcontroller required; the photoresistor and comparator directly trigger the relay .

• Adjustable Light Threshold: Onboard potentiometer sets the trigger point for relay activation .

• Isolated Relay Output: 10A @ 250V AC or 30V DC contact rating for direct load control .

• 12V DC Operation with 78L05 Regulator: Stable power for reliable switching .

• Optocoupler Isolation: Protects the control circuit from load-side interference .

• Detachable LDR Probe (on most variants): 30cm cable allows the sensor to be placed away from the module .

• Indicator LEDs: Power and relay-status LEDs for calibration feedback .

• Anti-Reverse Power Protection: Reversing the 12V supply does not damage the module .

Technical Specifications