Can I trigger this 12V relay module using a 3.3V ESP32 or Raspberry Pi?

Yes, while the relay coils require a separate 12V power supply, the optocoupler trigger inputs only require about 5mA and can be safely activated by 3.3V or 5V logic signals.

What does the High/Low level trigger jumper actually do?

The jumper allows you to choose how the relay activates: setting it to "H" means the relay turns on when your microcontroller sends a HIGH voltage signal, while "L" means it turns on when it sends a LOW (Ground) signal.

Is it safe to control 220V AC household appliances with this module?

Yes, the onboard Songle relays are rated to safely switch up to 10A at 250V AC, making them suitable for standard household lights and appliances. (Always exercise extreme caution when working with mains voltage).

What is the purpose of the optocoupler on this board?

The optocoupler uses light to transmit the trigger signal internally, creating a physical electrical barrier that prevents high-voltage spikes from the relay side from destroying your microcontroller.

Can I buy these relay modules in bulk at your Hong Kong store?

Yes, we stock all variations (1, 2, 4, and 8 channels) of this 12V relay module in large quantities at our Sun Cheong Computer Co. Ltd. physical store in Sham Shui Po.

12V Relay Module w/ Optocoupler | 1/2/4/8 Ch High/Low Trigger

Short Product Description

Take control of high-power devices safely with the 12V Opto-Isolated Relay Module. Available in 1, 2, 4, or 8-channel configurations, this module features genuine Songle 10A relays and true optocoupler isolation to protect your Arduino, Raspberry Pi, or ESP32 from dangerous voltage spikes. With selectable High/Low level triggers via onboard jumpers, it offers maximum compatibility for any DIY automation project. Available in-stock at Sun Cheong Computer Co. Ltd. (新昌電腦有限公司) in Sham Shui Po, this is the ultimate instant-pickup component for makers building custom smart home systems or industrial controls.

Key Features

Multiple Channel Options: Choose from 1, 2, 4, or 8-channel boards to perfectly scale with your specific automation project.
True Optocoupler Isolation: Protects your delicate microcontrollers from high-voltage spikes and electrical noise generated by heavy loads.
Selectable High/Low Trigger: Onboard jumpers allow you to independently set each channel to trigger on a HIGH (3.3V-12V) or LOW (0V) signal.
Heavy-Duty Songle Relays: Each channel utilizes a reliable Songle SRD-12VDC-SL-C relay, rated for a massive 10A at 250VAC or 30VDC.
Visual Status Indicators: Features dedicated power and relay activation LEDs for instant, at-a-glance circuit debugging.

Full Product Description

Safe High-Power Control for Microcontrollers

Microcontrollers like the Arduino or ESP32 operate on delicate 3.3V or 5V logic and cannot directly drive high-power appliances. This 12V Relay Module acts as a robust, electrically isolated bridge. Each channel is equipped with a genuine Songle SRD-12VDC-SL-C relay capable of switching heavy loads up to 10A at 250VAC or 30VDC. Whether you are automating living room lights, controlling a water pump for hydroponics, or managing industrial solenoids, this module ensures your high-voltage circuits remain completely separated from your low-voltage logic board.

True Optocoupler Isolation & Selectable Triggers

Unlike cheaper relay boards, this module features true optocoupler isolation on every channel. This optical barrier prevents catastrophic voltage spikes and ground loop interference from traveling back into your expensive microcontroller. Furthermore, the board offers unparalleled flexibility with its selectable High/Low level trigger jumpers. By simply moving a jumper cap, you can configure each individual relay to activate on a HIGH signal (e.g., 5V) or a LOW signal (0V/GND), making it universally compatible with almost any sensor or logic controller on the market.

Pro Tip from Our Technicians

Always ensure you are providing a dedicated 12V DC power supply to the DC+ and DC- terminals to power the relay coils. Our Sham Shui Po DIY specialists strongly warn against trying to power the relay coils directly from your Arduino's 5V pin, as the coils require 12V to actuate. However, the trigger pins (IN1, IN2, etc.) only draw about 5mA and are perfectly safe to connect directly to your 3.3V or 5V microcontroller GPIO pins.

Technical Specifications

Product Type: Opto-Isolated Relay Module
Available Configurations: 1-Channel, 2-Channel, 4-Channel, 8-Channel
Coil Operating Voltage: 12V DC
Relay Model: Songle SRD-12VDC-SL-C
Maximum Load Rating: 10A 250VAC / 10A 125VAC / 10A 30VDC / 10A 28VDC
Trigger Voltage Range: 3.3V - 12V DC
Trigger Current: Approx. 5mA per channel
Isolation Method: Optocoupler (Photocoupler)
Trigger Mode: High / Low Level (Selectable via Jumper)
Output Terminals: Normally Open (NO), Common (COM), Normally Closed (NC)

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

Can I trigger this 12V relay module using a 3.3V ESP32 or Raspberry Pi?Yes, while the relay coils require a separate 12V power supply, the optocoupler trigger inputs only require about 5mA and can be safely activated by 3.3V or 5V logic signals.
What does the High/Low level trigger jumper actually do?The jumper allows you to choose how the relay activates: setting it to "H" means the relay turns on when your microcontroller sends a HIGH voltage signal, while "L" means it turns on when it sends a LOW (Ground) signal.
Is it safe to control 220V AC household appliances with this module?Yes, the onboard Songle relays are rated to safely switch up to 10A at 250V AC, making them suitable for standard household lights and appliances. (Always exercise extreme caution when working with mains voltage).
What is the purpose of the optocoupler on this board?The optocoupler uses light to transmit the trigger signal internally, creating a physical electrical barrier that prevents high-voltage spikes from the relay side from destroying your microcontroller.
Can I buy these relay modules in bulk at your Hong Kong store?Yes, we stock all variations (1, 2, 4, and 8 channels) of this 12V relay module in large quantities at our Sun Cheong Computer Co. Ltd. physical store in Sham Shui Po.

Target Users / Applications

Smart home DIYers using ESP32 boards to build custom, multi-zone automated lighting and irrigation systems.
Industrial automation students learning to interface low-voltage PLCs with high-power 24V DC motors and solenoids.
Escape room designers creating complex puzzle mechanisms that require safe switching of 12V magnetic locks and sirens.