A compact, shield-style 4-channel relay module board designed for flexible DC control (5V, 12V, 24V). Built with optocoupler isolation and selectable trigger modes, it provides a practical, easy-to-integrate solution for switching electrical loads in hobby, prototyping, and light industrial projects. Key benefits Safe isolation: Optocoupler-based isolation protects control electronics from voltage spikes and electrical noise, lowering the risk of damage to microcontrollers and sensors. Flexible power compatibility: Works with DC 5V, 12V, or 24V power supplies, so you can use the module with a wide range of controllers and systems. Universal trigger modes: Supports both high-level and low-level trigger inputs for compatibility with different microcontrollers and logic levels. Shield-style convenience: Designed as a shield/module board to simplify wiring and mounting in project enclosures and development setups. Compact, application-focused size: Specifically sized for 4-channel 12V applications, offering a small footprint without sacrificing functionality. What it does and how it solves common problems Controls external devices: Lets you switch motors, lights, solenoids, and other DC/AC loads from low-voltage control signals, removing the need for direct manual switching. Protects control circuits: Optocoupler isolation reduces backfeed and interference, protecting sensitive electronics during switching events. Adapts to different controllers: Selectable high or low trigger modes mean you can connect outputs from a broad range of microcontrollers, PLCs, and single-board computers without level-shifting hardware. Simplifies integration: Shield-style layout and clear channel grouping speed up wiring, reduce errors, and make installation neater and more reliable. Key attributes Channels: 4 relay channels Power supply: Compatible with DC 5V, 12V, and 24V Isolation: Optocoupler isolation for each channel Trigger modes: Selectable high-level or low-level triggering Form factor: Shield/module board with compact dimensions designed for 4-channel 12V use Performance: Reliable switching for a variety of electrical control needs Typical applications Home automation: Control lighting circuits, fans, or small appliances from a central controller or automation system while keeping the controller isolated from mains-related disturbances. Prototyping and robotics: Interface motors, actuators, and external modules to microcontrollers and single-board computers; selectable trigger modes make it easy to connect to different logic levels. Light industrial control: Drive solenoid valves, indicator circuits, or auxiliary systems in test rigs and small-scale process control while maintaining isolation between control and power circuits. Practical notes Confirm the relay contact ratings of your specific module before connecting high-current or high-voltage loads. Use appropriate wiring, fuses, and safety practices when switching mains or inductive loads. Select high or low trigger mode to match your controller’s output logic for reliable operation. This 4-channel relay module board delivers a compact, flexible, and protected way to switch external loads from standard control electronics, making it suitable for development, automation, and light industrial projects.