Does the 5V Photoresistor Relay Module require an Arduino to work?

No, the 5V Photoresistor Relay Module operates as a completely standalone device and does not require an Arduino or any programming. As long as you provide it with 5V power, the onboard photoresistor and potentiometer will automatically trigger the relay based on ambient light.

How is this module different from a standard photoresistor component?

The 5V Photoresistor Relay Module includes a built-in mechanical relay, allowing it to directly switch high-current appliances (up to 20A) on and off. A standard photoresistor is just a passive sensor that only changes resistance and cannot control power loads without additional circuitry.

How do I wire the COM, CK (NO), and CB (NC) terminals?

The COM (Common) terminal connects to your power source, while CK (Normally Open) and CB (Normally Closed) connect to your device. If you want a light to turn ON when it gets dark (relay activates), wire your device to the COM and CK terminals; if you want it to turn OFF when it gets dark, use COM and CB.

What happens if I wire the 5V power backwards by mistake?

If you wire the 5V power backwards, the 5V Photoresistor Relay Module will simply not power on, but it will not be damaged. The board features built-in reverse polarity protection to safeguard the components against accidental wiring errors during DIY assembly.

5V Photoresistor Relay Module | Light Sensor Switch

Name: 5V Photoresistor Relay Module | Light Sensor Switch
Brand: Sun Cheong Computer Company Limited
SKU: 21PS002380
Price: 15.0 HKD
Availability: InStock

Short Product Description

The 5V Photoresistor Relay Modulei s a standalone light-detecting switch designed for DIY automation, STEM projects, and smart lighting systems. Featuring an adjustable sensitivity potentiometer, reverse polarity protection, and a built-in relay capable of handling high-current loads, this module automatically turns devices on or off based on ambient light levels. Available for instant pickup at Sun Cheong Computer Co. Ltd.(新昌電腦有限公司) in Sham Shui Po, where our staff can provide expert technical advice for your custom electronic builds.

Key Features

Standalone Light Control: Operates independently to detect brightness and trigger switches without needing complex programming or external microcontrollers.
Adjustable Sensitivity: Features a built-in potentiometer to precisely calibrate the exact light level required to activate the relay.
Reverse Polarity Protection: Safely designed to prevent motherboard damage if the 5V power supply is accidentally connected backwards.
High Load Capacity: The integrated relay supports AC loads up to 125V/20A and DC loads up to 14V/20A, perfect for controlling high-power electronics.
Dual-Control Interface: Equipped with Common (COM), Normally Open (NO/CK), and Normally Closed (NC/CB) terminals for versatile wiring configurations.
Easy Installation: Designed with four M3 screw mounting holes for secure and straightforward integration into custom project enclosures.

Full Product Description

Automated Light Detection for DIY Projects

The 5V Photoresistor Relay Module automatically controls electrical circuits based on ambient light levels, acting as a smart switch for your automation projects. Whether you are building an automatic street light that turns on at dusk or a smart garden irrigation system, this module detects brightness changes through its dedicated photoresistor probe and triggers the onboard relay without requiring a separate microcontroller like an Arduino.

Built-In Potentiometer & Safe Wiring

You can easily adjust the light sensitivity threshold of the 5V Photoresistor Relay Module using the onboard blue potentiometer. By turning the dial, you dictate exactly how dark or bright the environment needs to be before the relay activates. Furthermore, the board features built-in reverse polarity protection, ensuring that accidentally swapping the 5V power and ground wires will not damage the module's circuitry.

Pro Tip from Our Technicians

For outdoor DIY lighting projects, our Sham Shui Po technical team strongly advises ensuring the photoresistor probe is physically shielded from the artificial light it controls. If the sensor detects the light bulb it just turned on, it will immediately turn the relay off, creating a rapid, continuous flickering loop. If you need help mapping out the COM, NO, and NC wiring for your specific STEM project, bring your schematic to our store for on-site advice!

Technical Specifications

Module Type: Photoresistor Relay Module (Light Detection Switch)
Operating Voltage: 5V DC
Protection Feature: Built-in reverse polarity protection
Load Capacity (AC): 0V - 125V / 20A
Load Capacity (DC): 0V - 14V / 20A
Output Terminals: Common (COM), Normally Open (CK), Normally Closed (CB)
Indicators: Power Indicator (Red LED), Relay Status Indicator (Red LED)
Mounting: 4 x M3 screw holes
Dimensions: 53 x 31 x 19 mm
Weight: 18.1 g

Delivery Options

Local delivery within Hong Kong and in-store pickup.
Free shipping for orders of HK$400 or above; HK$35 shipping fee for orders below HK$400.
Shipped by SF Express, usually dispatched the same day for orders confirmed before 6:00 PM (Mon–Sat).
Estimated delivery time: 1–3 business days after dispatch (Hong Kong).
In-store pickup details (location and time) will be confirmed by email or phone message.
Delivery times are estimates and may be affected by weather or unforeseen circumstances.

FAQ Section

Does the 5V Photoresistor Relay Module require an Arduino to work?No, the 5V Photoresistor Relay Module operates as a completely standalone device and does not require an Arduino or any programming. As long as you provide it with 5V power, the onboard photoresistor and potentiometer will automatically trigger the relay based on ambient light.
How is this module different from a standard photoresistor component?The 5V Photoresistor Relay Module includes a built-in mechanical relay, allowing it to directly switch high-current appliances (up to 20A) on and off. A standard photoresistor is just a passive sensor that only changes resistance and cannot control power loads without additional circuitry.
How do I wire the COM, CK (NO), and CB (NC) terminals?The COM (Common) terminal connects to your power source, while CK (Normally Open) and CB (Normally Closed) connect to your device. If you want a light to turn ON when it gets dark (relay activates), wire your device to the COM and CK terminals; if you want it to turn OFF when it gets dark, use COM and CB.
What happens if I wire the 5V power backwards by mistake?If you wire the 5V power backwards, the 5V Photoresistor Relay Module will simply not power on, but it will not be damaged. The board features built-in reverse polarity protection to safeguard the components against accidental wiring errors during DIY assembly.

Can I get technical advice for my STEM project at your store?Yes, you can bring your STEM project ideas to Sun Cheong Computer Co. Ltd. (新昌電腦有限公司) in Sham Shui Po for expert advice. Our staff has over 20 years of technical experience and can help you verify your wiring diagrams and select the right components for your automated lighting setup.

Target Users / Applications

STEM Educators & Students: Building automated science fair projects without needing to teach complex C++ Arduino coding.
Village House Owners: DIY retrofitting outdoor garden lights or rooftop lamps to turn on automatically at night.
Smart Agriculture Hobbyists: Automating grow lights or shading systems in small-scale indoor greenhouses based on natural sunlight.