How to Use 8 Channel 5v Relay: Examples, Pinouts, and Specs

The 8 Channel 5V Relay (Manufacturer: AC, Part ID: Relay) is a versatile relay module designed to control multiple high-voltage devices using low-voltage signals, such as those from a microcontroller. This module features 8 independent relay channels, each capable of switching high-voltage loads, making it ideal for applications requiring control of multiple devices.

• Home automation systems (e.g., controlling lights, fans, or appliances)
• Industrial automation and control
• Robotics and mechatronics
• IoT (Internet of Things) projects
• Prototyping and educational projects

Below are the key technical details of the 8 Channel 5V Relay module:

The module has two main interfaces: the control pins and the relay output terminals.

Each relay channel has three output terminals:

1. Power the Module: Connect the VCC pin to a 5V DC power source and the GND pin to ground.
2. Connect Control Signals: Use digital output pins from a microcontroller (e.g., Arduino UNO) to connect to the IN1 to IN8 pins. Each pin controls one relay channel.
3. Connect the Load: For each relay channel, connect the load to the COM and NO/NC terminals:
   • Use the NO terminal if the load should be off by default and turn on when the relay is activated.
   • Use the NC terminal if the load should be on by default and turn off when the relay is activated.
4. Activate the Relays: Send a LOW signal (0V) to the corresponding IN pin to activate the relay. A HIGH signal (5V) will deactivate it.

• Power Supply: Ensure the module is powered with a stable 5V DC supply. Using a separate power supply for the relays and the microcontroller is recommended to avoid noise or voltage drops.
• Isolation: The module features optocoupler isolation to protect the microcontroller from high-voltage spikes. Ensure proper grounding for safety.
• Load Ratings: Do not exceed the maximum load voltage (250V AC / 30V DC) or current (10A) for each relay channel.
• Inductive Loads: When switching inductive loads (e.g., motors), use a flyback diode across the load to suppress voltage spikes.

Below is an example of how to control the 8 Channel 5V Relay module using an Arduino UNO:

• Connect the module's VCC to the Arduino's 5V pin.
• Connect the module's GND to the Arduino's GND pin.
• Connect the module's IN1 to IN8 pins to Arduino digital pins 2 to 9, respectively.
• Connect a load (e.g., a light bulb) to the COM and NO terminals of one relay channel.

// Example code to control an 8 Channel 5V Relay module with Arduino UNO

// Define the relay control pins
const int relayPins[] = {2, 3, 4, 5, 6, 7, 8, 9};

void setup() {
  // Initialize all relay pins as OUTPUT
  for (int i = 0; i < 8; i++) {
    pinMode(relayPins[i], OUTPUT);
    digitalWrite(relayPins[i], HIGH); // Set all relays to OFF state
  }
}

void loop() {
  // Example: Sequentially turn on each relay for 1 second
  for (int i = 0; i < 8; i++) {
    digitalWrite(relayPins[i], LOW);  // Turn ON relay (active LOW)
    delay(1000);                      // Wait for 1 second
    digitalWrite(relayPins[i], HIGH); // Turn OFF relay
  }
}

1. Relays Not Activating

   • Cause: Insufficient power supply.
   • Solution: Ensure the module is powered with a stable 5V DC source.

2. Microcontroller Resets When Relays Activate

   • Cause: Voltage drop due to high current draw.
   • Solution: Use a separate power supply for the relay module and the microcontroller.

3. Load Not Switching Properly

   • Cause: Incorrect wiring of the load to the relay terminals.
   • Solution: Verify the load is connected to the correct COM and NO/NC terminals.

4. Relays Stuck in ON/OFF State

   • Cause: Faulty relay or excessive load current.
   • Solution: Check the load current and replace the relay if necessary.

Q: Can this module be used with a 3.3V microcontroller (e.g., ESP32)?
A: Yes, the module is compatible with 3.3V control signals, but ensure the VCC pin is still powered with 5V.

Q: Is it safe to control AC appliances with this module?
A: Yes, but ensure proper insulation and follow safety guidelines when working with high-voltage AC loads.

Q: Can I control all 8 relays simultaneously?
A: Yes, as long as the total current draw does not exceed the power supply's capacity.

Q: Do I need external components to use this module?
A: No additional components are required for basic operation, but a flyback diode is recommended for inductive loads.