Overview
The 4-Channel 5V Relay Module is an essential multi-channel expansion board that allows low-voltage microcontrollers to control high-voltage, high-current appliances safely. Each channel is equipped with a genuine Songle relay capable of switching currents up to 10 Amperes. To ensure maximum safety for your sensitive development boards, this module features complete optical isolation (optocouplers), meaning your Arduino or ESP32 is completely insulated from any reverse electrical feedback or spikes from the heavy loads.
Key Features
Dual AC & DC Switching: Highly versatile—safely switches AC mains appliances ($220\text{V}$) as well as high-current DC loads ($12\text{V}$ or $24\text{V}$ motors/valves).
Optocoupler Isolation: Built-in EL817 optocouplers completely separate your microcontroller’s fragile logic circuit from the high-voltage relay coils.
Flexible Triggering (JD-VCC Jumper): Includes a removable jumper that allows you to power the relay coils from a completely separate power supply, ensuring zero noise feedback to your microcontroller.
On-Board Status Indicators: Individual red SMD LEDs light up to clearly show which channel is currently activated.
Standard Terminal Blocks: Heavy-duty, blue screw terminals provide solid connections for thick appliance wiring with clear Normally Open (NO), Common (COM), and Normally Closed (NC) configurations.
Technical Specifications
| Feature | Specification |
| Channel Count | 4 Channels (Independently Controlled) |
| Coil Operating Voltage | 5V DC |
| Trigger Current | 15mA – 20mA per channel |
| Trigger Logic | Low-Level Trigger (0V to 1.5V activates relay) |
| Max AC Rating | 10A 250V AC / 10A 125V AC |
| Max DC Rating | 10A 30V DC / 10A 28V DC |
| Relay Brand | High-Quality Songle (SRD-05VDC-SL-C) |
| Board Dimensions | 75mm x 55mm x 18mm |
| Weight | ~60 grams |
Understanding the Output Terminals
Each channel features a 3-pin screw terminal block:
COM (Common): The main power feed line from your source.
NO (Normally Open): The circuit stays disconnected until your microcontroller sends a trigger signal to “click” the relay shut. Perfect for turning things on demand (like a light).
NC (Normally Closed): The circuit stays connected by default and disconnects only when the relay is triggered. Ideal for emergency cutoff systems.
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