5V DC 4-Channel Relay Module

The 5V 4-Channel Relay Module is a professional-grade electromechanical switching board designed to provide your microcontroller with the ability to safely and reliably control high-power AC and DC loads. With four independent SPDT (Single Pole Double Throw) relays, this module is one of the most popular and versatile expansion boards in the DIY electronics, home automation, and IoT communities.

Each relay channel can switch loads up to AC 250V at 10A or DC 30V at 10A, making it suitable for controlling a wide range of devices including lights, fans, motors, pumps, solenoids, heaters, garage doors, and home appliances. The relays use NO (Normally Open) and NC (Normally Closed) contacts, providing maximum flexibility for both fail-safe and fail-on designs.

The module is built around the trusted SRD-05VDC-SL-C relays (or compatible) and features galvanic isolation between the control circuit and the load, providing important safety separation between your low-voltage microcontroller and high-voltage AC mains. Each channel includes a dedicated driver transistor and protective flyback diode, allowing the relay coil to be safely energized by a simple 5V TTL HIGH signal from any Arduino digital pin, ESP32 GPIO, or Raspberry Pi output.

Each relay channel features its own indication LED that lights up when the relay is activated, providing clear visual feedback during testing, debugging, and operation. The screw terminal blocks make wiring easy and secure, while the standard 0.1-inch (2.54mm) male header on the input side allows direct connection via Dupont jumper wires to any microcontroller.

With its compact dimensions (71 × 46 × 17 mm), 3mm mounting holes at each corner, and lightweight design (~58g), this module fits easily into project enclosures, control panels, and DIY home automation hubs. Its plug-and-play design and clear pin labeling make it accessible to beginners while still being reliable enough for commercial and industrial prototyping.

Pinout

Input Side (Microcontroller Connection)

• VCC: +5V Power Supply
• GND: Ground
• IN1: Channel 1 Trigger (HIGH = Relay ON)
• IN2: Channel 2 Trigger (HIGH = Relay ON)
• IN3: Channel 3 Trigger (HIGH = Relay ON)
• IN4: Channel 4 Trigger (HIGH = Relay ON)

Output Side (Each Relay)

• NO (Normally Open): Connected to COM when relay is ON
• COM (Common): Common contact
• NC (Normally Closed): Connected to COM when relay is OFF

Specifications

• Brand: N/A (Generic)
• Model: CG05SZ-009
• Number of Channels: 4
• Relay Type: SPDT (Single Pole Double Throw)
• Power Supply Voltage: 5V DC
• Trigger Voltage: 5V TTL (HIGH-level Trigger)
• Relay Coil Voltage: 5V DC
• Switching Capacity:
  • AC 250V @ 10A
  • DC 30V @ 10A
• Maximum Switching Power: 2,500 VA / 300 W per channel
• Status LEDs: 4 (one per channel) + 1 power LED
• Indicator LEDs: Red (typical) for relay activation
• Mounting Hole Diameter: 3 mm
• PCB Material: RF4 (FR-4 Glass Epoxy)
• Dimensions: 71 × 46 × 17 mm (2.8" × 1.81" × 0.67")
• Weight: ~58 g (2.05 oz)
• Color: Red PCB + Blue Relays
• Connectors:
  • Input: 6-pin male header (2.54mm pitch)
  • Output: Screw terminal blocks (3 per channel)
• Compliance: RoHS Compliant

Applications

• Home Automation Systems — controlling lights, fans, and appliances
• Smart Home & IoT Devices — WiFi-controlled relays via ESP32/ESP8266
• Lighting Control — automated indoor and outdoor lighting systems
• Motor Control — switching small AC and DC motors ON/OFF
• Pump Control — water pumps for gardens, aquariums, and irrigation
• Heater Control — switching heating elements and PTC heaters
• Solenoid & Valve Control — water valves and electric locks
• Garage Door Openers — remote-controlled door triggers
• Aquarium Automation — light, heater, pump scheduling
• Greenhouse Automation — fans, lights, irrigation, and ventilation
• Industrial Process Control — multi-channel switching for prototypes
• Security & Alarm Systems — siren, strobe, and door-lock control
• Robotics — switching auxiliary loads from microcontroller outputs
• CNC & 3D Printer Add-ons — controlling spindles, lights, and cooling
• DIY Time-Switches & Timers — combined with RTC modules and Arduino
• Educational & STEM Projects — teaching relay logic and isolation
• Power Distribution Systems — controlling multiple loads from a single MCU
• Sound-Activated Switches — combined with sound sensors
• Light-Activated Switches — combined with LDR or light sensors
• Replacement Module — for damaged 4-channel relay boards