12V 4-Channel Relay Module with SMD Optocoupler (OPTO) Isolation — Supports High and Low Level Triggers Key benefits Protects your controller: SMD optocoupler (OPTO) insulation isolates control inputs from the relay outputs, reducing noise, preventing ground loops, and protecting sensitive logic devices. Flexible control: Built-in support for both high-level and low-level trigger inputs lets you interface with a wide range of control signals without additional wiring changes. Multi-channel convenience: Four independent relay channels let you switch multiple circuits or devices from a single module, saving space and simplifying wiring. Stable 12V operation: Designed for 12V power supply environments for consistent relay activation and reliable switching performance. What it does Switches external loads using four electromagnetic relays while keeping the control side electrically isolated via SMD optocouplers. Accepts selectable trigger polarity (active-high or active-low) so the same module can work with different control logic setups. Reduces false triggers and interference by separating signal and power domains with OPTO insulation. Important attributes Function: 4 independent relay outputs with optocoupler-isolated control inputs. Isolation method: SMD optocoupler (OPTO) for input-to-output electrical separation. Supply voltage: 12V for module/relay power. Trigger modes: Supports both high-level and low-level trigger inputs (selectable). Build: Compact PCB-mounted relays with surface-mounted optocouplers for space-efficient assembly and consistent performance. Reliability: Isolation and input circuitry reduce noise-related faults and improve long-term stability. How this solves common problems Prevents damage to microcontrollers and control electronics caused by voltage spikes or ground noise by isolating the relay coil and switched circuit from the logic inputs. Simplifies integration when working with different logic levels or signal polarities — no need for level-shifting hardware if you can select the appropriate trigger mode. Consolidates multiple load controls into one module to reduce wiring complexity and panel space. Typical use scenarios Home automation: Control lighting, fans, or other household appliances from a centralized controller while protecting control electronics from mains noise. Prototyping and development: Interface multiple actuators or devices to a control board during testing without risking damage to the control board from switched loads. Industrial or small machinery control: Switch pumps, solenoids, or relays for equipment while keeping control logic isolated from electrical noise and transients. Quick integration tips Power the module with a stable 12V supply capable of supporting all four relays. Select the trigger polarity (high or low) to match your control signal behavior before wiring. Maintain proper separation between high-voltage switched circuits and low-voltage control wiring to preserve isolation effectiveness. This 12V 4-channel relay module with SMD optocoupler insulation delivers flexible, protected switching for multi-channel control applications while supporting both high and low level triggers for easy integration.