4-Channel Relay for Arduino – Safely Control High-Voltage Devices with Opto-Isolation

The 4-Channel 5V Relay Control Expansion Board for Arduino Uno R3 / Mega2560 is an Arduino-compatible relay shield that allows you to control up to four independent electromechanical relays directly from your microcontroller. This makes it ideal for switching high-power AC or DC loads (like lights, pumps, fans, or other household appliances) that the Arduino alone cannot safely drive.

Key Features:

• 4 independent relay channels – each controlled separately via digital pins from the Arduino.

• Operating voltage: 5 V logic compatible with standard Arduino boards.

• LED status indicators – each relay channel has an LED showing when that relay is activated.

• Arduino shield form factor – easily plugs into Arduino Uno R3, Mega2560 and other R3 boards.

• Mounting holes: secured with M3 mounting holes for installation in projects and enclosures.

• Stackable expansion: standard shield shape allows stacking with other Arduino expansion boards.

How it works:
Each relay is activated by setting the corresponding Arduino digital pin to HIGH or LOW. When activated, the relay closes its NO (normally open) contact to COM, allowing you to switch external circuits.

Typical Uses:
✔ Smart home automation – lighting, fans, HVAC control.
✔ High-power switching – motors, pumps, heaters.
✔ Robotics and electromechanical systems.
✔ Educational and DIY electronics with microcontrollers.

Note: For high-current applications, always use an external power supply for the loads to avoid overloading the Arduino board.