How to Use RELAY 2CHANNEL: Examples, Pinouts, and Specs

The RELAY 2CHANNEL module is a versatile electronic component designed to control high-voltage devices using low-voltage signals. It features two independent relay channels, allowing users to switch two separate devices simultaneously. The module is commonly equipped with opto-isolation to ensure safety and protect low-voltage control circuits from high-voltage spikes.

This relay module is widely used in home automation, industrial control systems, robotics, and IoT projects. It is particularly useful for controlling appliances, lights, motors, and other high-power devices with microcontrollers like Arduino, Raspberry Pi, or other low-power control systems.

• Relay Type: Electromechanical
• Number of Channels: 2
• Control Voltage: 3.3V to 5V DC
• Relay Voltage: 5V DC
• Maximum Switching Voltage: 250V AC or 30V DC
• Maximum Switching Current: 10A
• Opto-Isolation: Yes
• Trigger Type: Active Low
• Dimensions: ~50mm x 40mm x 20mm
• Mounting Holes: Yes

1. Power the Module: Connect the VCC pin to a 5V DC power supply and the GND pin to the ground of your control circuit.
2. Connect the Control Signals: Use digital output pins from a microcontroller (e.g., Arduino) to connect to the IN1 and IN2 pins. Ensure the control signals are active low.
3. Connect the Load:
   • For devices that should be OFF by default, connect the load between the COM and NO terminals.
   • For devices that should be ON by default, connect the load between the COM and NC terminals.
4. Trigger the Relays: Send a LOW signal (0V) to the IN1 or IN2 pin to activate the corresponding relay and switch the connected load.

• Opto-Isolation: Ensure the module's opto-isolation is intact to protect your microcontroller from high-voltage spikes.
• Power Supply: Use a stable 5V DC power supply to avoid erratic relay behavior.
• Inductive Loads: When controlling inductive loads (e.g., motors), use a flyback diode across the load to suppress voltage spikes.
• Current Ratings: Do not exceed the relay's maximum current rating of 10A to prevent damage.
• Safety: Always disconnect power when wiring high-voltage devices to avoid electric shock.

Below is an example code to control two relays using an Arduino UNO:

// Define the relay control pins
const int relay1Pin = 7; // Pin connected to IN1
const int relay2Pin = 8; // Pin connected to IN2

void setup() {
  // Set relay pins as outputs
  pinMode(relay1Pin, OUTPUT);
  pinMode(relay2Pin, OUTPUT);

  // Initialize relays to OFF state (HIGH signal)
  digitalWrite(relay1Pin, HIGH);
  digitalWrite(relay2Pin, HIGH);
}

void loop() {
  // Turn on Relay 1
  digitalWrite(relay1Pin, LOW); // Active Low signal to trigger relay
  delay(1000); // Wait for 1 second

  // Turn off Relay 1
  digitalWrite(relay1Pin, HIGH); // Deactivate relay
  delay(1000); // Wait for 1 second

  // Turn on Relay 2
  digitalWrite(relay2Pin, LOW); // Active Low signal to trigger relay
  delay(1000); // Wait for 1 second

  // Turn off Relay 2
  digitalWrite(relay2Pin, HIGH); // Deactivate relay
  delay(1000); // Wait for 1 second
}

1. Relays Not Activating:

   • Ensure the VCC and GND pins are properly connected to a 5V power supply.
   • Verify that the control signals (IN1, IN2) are active low (0V to trigger the relay).
   • Check for loose or incorrect wiring.

2. Erratic Relay Behavior:

   • Use a stable and sufficient power supply to avoid voltage drops.
   • Ensure the microcontroller's ground is connected to the relay module's ground.

3. Load Not Switching:

   • Verify the wiring of the load to the COM, NO, or NC terminals.
   • Ensure the load's voltage and current ratings are within the relay's specifications.

4. Microcontroller Resetting:

   • High-current loads may cause voltage spikes. Use a flyback diode across inductive loads.
   • Ensure the power supply can handle the combined current draw of the relay module and the microcontroller.

Q: Can I use the RELAY 2CHANNEL module with a 3.3V microcontroller?
A: Yes, the module is compatible with 3.3V control signals, but ensure the VCC pin is still powered with 5V.

Q: Is the module safe for high-voltage applications?
A: Yes, the module is designed for high-voltage applications, but proper insulation and safety precautions must be followed.

Q: Can I control DC devices with this module?
A: Yes, the module can switch DC devices up to 30V and 10A.

Q: What is the purpose of opto-isolation?
A: Opto-isolation protects the low-voltage control circuit from high-voltage spikes and electrical noise.