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

The 5V 8 Channel Relay Board is an electronic module designed to control up to eight devices using a 5V power supply. It acts as an interface between low-voltage control signals (e.g., from a microcontroller) and high-voltage loads, such as lights, motors, or appliances. Each relay on the board can switch devices operating at up to 250V AC or 30V DC, making it ideal for home automation, industrial control, and IoT applications.

• Home automation systems (e.g., controlling lights, fans, or appliances)
• Industrial equipment control
• Robotics and motor control
• IoT projects requiring high-voltage switching
• Prototyping and testing circuits with high-power devices

• Operating Voltage: 5V DC
• Trigger Voltage: 3.3V to 5V (compatible with most microcontrollers)
• Relay Channels: 8
• Maximum Load (per relay):
  • 250V AC at 10A
  • 30V DC at 10A
• Relay Type: SPDT (Single Pole Double Throw)
• Isolation: Optocoupler isolation for each channel
• Indicator LEDs: One LED per channel to indicate relay status
• Dimensions: Approximately 140mm x 50mm x 20mm

1. Power the Relay Board:

   • Connect the VCC pin to a 5V power supply and the GND pin to ground.
   • Ensure the power supply can provide sufficient current for all active relays (approximately 70-80mA per relay).

2. Connect the Control Signals:

   • Connect the IN1-IN8 pins to the digital output pins of a microcontroller (e.g., Arduino UNO).
   • A LOW signal (0V) on an input pin will activate the corresponding relay.

3. Connect the Load:

   • Identify the device or circuit you want to control.
   • Connect the power source and load to the relay's COM, NO, or NC terminals based on the desired behavior:
     • Use COM and NO for devices that should be OFF by default.
     • Use COM and NC for devices that should be ON by default.

4. Test the Circuit:

   • Power on the relay board and microcontroller.
   • Send control signals to the relay board to toggle the relays and verify the load's behavior.

• Isolation: Ensure proper electrical isolation between the low-voltage control side and the high-voltage load side to prevent damage or hazards.
• Current Ratings: Do not exceed the maximum current and voltage ratings of the relays.
• Flyback Diodes: If controlling inductive loads (e.g., motors), use flyback diodes across the load to protect the relay from voltage spikes.
• Power Supply: Use a stable 5V power supply capable of handling the total current draw of all active relays.

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

• Connect the relay board's VCC to the Arduino's 5V pin.
• Connect the relay board's GND to the Arduino's GND pin.
• Connect the relay board's IN1-IN8 pins to Arduino digital pins 2-9.

// Example code to control an 8-channel relay board with an Arduino UNO

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

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

void loop() {
  // Example: Turn relays ON one by one, then OFF
  for (int i = 0; i < 8; i++) {
    digitalWrite(relayPins[i], LOW); // Activate relay (LOW signal)
    delay(1000); // Wait 1 second
    digitalWrite(relayPins[i], HIGH); // Deactivate relay (HIGH signal)
    delay(1000); // Wait 1 second
  }
}

1. Relays Not Activating:

   • Cause: Insufficient power supply.
   • Solution: Ensure the power supply provides 5V and sufficient current for all active relays.

2. Relay Stuck in ON or OFF State:

   • Cause: Incorrect wiring or damaged relay.
   • Solution: Double-check the wiring and replace the relay if necessary.

3. Microcontroller Resetting When Relays Activate:

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

4. Load Not Switching Properly:

   • Cause: Incorrect connection to the relay terminals.
   • Solution: Verify the load is connected to the correct COM, NO, or NC terminals.

• Q: Can I use a 3.3V microcontroller with this relay board?
  A: Yes, the relay board is compatible with 3.3V control signals, but ensure the VCC pin is powered with 5V.

• Q: How many relays can I activate simultaneously?
  A: You can activate all 8 relays simultaneously, provided your power supply can handle the total current draw.

• Q: Can this relay board switch DC loads?
  A: Yes, it can switch DC loads up to 30V at 10A.

• Q: Is the relay board safe for high-voltage applications?
  A: Yes, but ensure proper insulation and safety precautions when working with high voltages.