5V 4-Channel Optocoupler Relay Module

5V 4-Channel Relay Board with Optocoupler for Arduino DIY Projects

This 5V 4-Channel Relay Module is a vital component for hobbyists and students. It provides a simple and reliable way to control high-voltage appliances like lights, fans, and motors using a low-voltage signal from your microcontroller. Each of the four channels is equipped with a high-quality optocoupler. This essential feature provides electrical isolation, creating a safety barrier that protects your sensitive electronics (like an Arduino, ESP32, or Raspberry Pi) from dangerous high-voltage power surges. Available from Bigyan Project, this module is perfect for anyone in Bangladesh looking to build robust home automation, robotics, or other DIY electronics projects safely and effectively.

Product Specifications

Features

• Manage up to four separate high-power devices independently from a single board.
• Built-in optocouplers on each channel protect your microcontroller from high-voltage feedback and electrical noise.
• Equipped with high-quality relays capable of handling heavy loads up to 10A, suitable for most household appliances.
• Individual LEDs for each channel (plus a main power LED) visually confirm the relay's on/off status, making troubleshooting easier.
• Easily connects to the digital I/O pins of most microcontrollers, including Arduino, AVR, PIC, 51, and ARM.
• Features fixed screw holes for secure and permanent installation in your project enclosure.

Applications / Use Cases

• Control lights, fans, coffee makers, and other home appliances for Smart Home Automation.
• Activate high-power motors, actuators, or solenoids in robotics projects.
• Create web-controlled switches to manage devices remotely for IoT (Internet of Things) devices.
• A perfect and safe component for university and school-level science fair projects.
• Suitable for simple industrial automation tasks and interfacing with PLC systems.
• Control 12V water pumps and grow lights for automated gardening systems.

User Guide / How to Use

Connecting this 4-channel relay module is straightforward. The board has two main connection sections: the low-voltage control side and the high-voltage load side.

Control Side (Low Voltage - Connect to Microcontroller):

• Connect VCC to the 5V power supply pin from your Arduino or an external 5V source.
• Connect GND to the Ground (GND) pin of your microcontroller.
• Connect IN1, IN2, IN3, IN4 to the digital output pins of your microcontroller (e.g., Arduino digital pins 7, 8, 9, 10).

Important Note: Most of these modules are Active-LOW. This means sending a LOW signal (0V) from your microcontroller pin will turn the relay ON. Sending a HIGH signal (5V) will turn the relay OFF. You can test this by connecting IN1 to GND (relay should click ON) and then to VCC (relay should click OFF).

Load Side (High Voltage - Connect to Appliance):

Each of the four relays has three screw terminals for connecting your device:

• COM (Common): This is where you typically connect the "live" wire of your AC appliance or one wire of your DC device.
• NO (Normally Open): The connection between COM and NO is broken by default (relay OFF). When you activate the relay, this connection is made. This is the most common terminal to use.
• NC (Normally Closed): The connection between COM and NC is active by default (relay OFF). When you activate the relay, this connection is broken.

Frequently Asked Questions (FAQs)

• Q: Can I control this 5V relay module with a 3.3V microcontroller like an ESP32 or Raspberry Pi?
  A: While the relay coil itself needs 5V (at VCC), the trigger signal (IN pins) *might* work with a 3.3V logic signal. However, for guaranteed reliability, it is often recommended to use a logic level converter to shift the 3.3V signal to 5V.
• Q: What does the optocoupler (opto-isolator) do?
  A: The optocoupler uses light to transmit the control signal. This creates a physical air gap that electrically isolates your low-voltage (5V) microcontroller circuit from the high-voltage (220V AC) side of the relay. This is a critical safety feature.
• Q: Can I control both AC and DC devices with this module?
  A: Yes. The relays are rated for both AC (up to 250V) and DC (up to 30V), as long as you stay within the 10A current limit specified.
• Q: Does the module need a separate power supply?
  A: You can power the VCC pin from your Arduino's 5V pin. However, if you are using all four relays at once, they can draw significant current. For stability, using a dedicated 5V 1A power supply for the relay module (with a common ground) is a good practice.

Challenges and Considerations

• Ensure your 5V power source can supply enough current to energize all four relay coils simultaneously if your project requires it.
• Beginners often find the Active-LOW trigger logic (LOW = ON) counter-intuitive. Always double-check your code.
• When controlling inductive loads (like motors or fans), the load can create a high-voltage spike when turned off. For large motors, an external flyback diode is recommended.
• Always use extreme caution when working with AC 220V. Ensure all high-voltage connections are secure, insulated, and housed in a proper enclosure.

Compatibility

• Fully compatible with 5V logic microcontrollers like Arduino Uno, Arduino Mega, Arduino Nano, AVR, and PIC series.
• Can be used with ESP32, ESP8266, and Raspberry Pi, but may require a logic level shifter for the most reliable trigger signal.
• Works with any platform that can output a digital signal (High/Low) to trigger the input pins.

Future Enhancement Options

• Integrate this module into a custom PCB for a more permanent and professional-looking project.
• Combine it with an ESP8266 or ESP32 Wi-Fi module to create a smart switch you can control from your phone.
• House the module and your microcontroller in a 3D-printed enclosure for safety and a clean, finished product.
• Use it as the main control board for a multi-functional robot, controlling motors, lights, and other actuators.

Benefits

• The optocoupler isolation provides a crucial safety barrier, giving you peace of mind when working with high-voltage AC.
• This module is far easier and more reliable than building your own relay driver circuit from individual components.
• The on-board LEDs instantly show you which relays are active, saving valuable debugging time.
• The module's flexibility allows it to control both AC and DC devices, opening up a massive range of DIY project possibilities.

Conclusion

The 5V 4-Channel Relay Module with Optocoupler is an indispensable tool for any electronics enthusiast, student, or hobbyist in Bangladesh. It safely and effectively bridges the gap between low-voltage microcontrollers and the high-voltage real-world devices you want to control. Whether you are building your first smart home system, a complex robot, or a simple automated plant waterer, this module provides the reliable switching you need. Get your 4-channel relay module from Bigyan Project (বিজ্ঞান প্রজেক্ট) today and take confident control of your next great idea.

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