How to Use 2 Channel Relay: Examples, Pinouts, and Specs

A 2 Channel Relay is an electromechanical switch that allows control of two separate circuits using a single control signal. It is widely used in applications where high voltage or high current loads need to be controlled by low-power control signals. The relay provides electrical isolation between the control circuit and the load, ensuring safety and reliability.

• Home automation systems (e.g., controlling lights, fans, or appliances)
• Industrial automation for switching motors or heavy machinery
• IoT projects for remote control of devices
• Robotics for controlling actuators or other high-power components
• Automotive systems for switching high-current loads

• Operating Voltage (Control Side): 5V DC (common), 12V DC (optional versions available)
• Trigger Voltage: 3.3V to 5V (compatible with most microcontrollers, including Arduino)
• Relay Type: SPDT (Single Pole Double Throw) for each channel
• Maximum Load (AC): 250V AC at 10A
• Maximum Load (DC): 30V DC at 10A
• Isolation: Optocoupler-based isolation between control and load circuits
• Indicator LEDs: Onboard LEDs for each channel to indicate relay status
• Dimensions: Typically 50mm x 40mm x 20mm (varies by manufacturer)

The 2 Channel Relay module typically has the following pin configuration:

1. Power the Relay Module:

   • Connect the VCC pin to a 5V DC power source.
   • Connect the GND pin to the ground of the power source.

2. Connect the Control Signals:

   • Connect the IN1 and IN2 pins to the digital output pins of a microcontroller (e.g., Arduino).
   • Ensure the control signals are within the operating voltage range (3.3V to 5V).

3. Connect the Load:

   • For each relay channel, connect the load to the COM and NO/NC terminals based on your requirements:
     • 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. Control the Relays:

   • Send a HIGH signal to IN1 or IN2 to activate the corresponding relay and switch the load.

• Power Supply: Ensure the relay module is powered by a stable 5V DC source. Avoid exceeding the voltage rating.
• Isolation: The relay provides electrical isolation, but ensure proper grounding to avoid noise or interference.
• Load Ratings: Do not exceed the maximum load ratings (10A at 250V AC or 30V DC) to prevent damage.
• Flyback Diodes: If controlling inductive loads (e.g., motors), use flyback diodes across the load terminals to suppress voltage spikes.
• Arduino Compatibility: The relay is compatible with 3.3V and 5V logic levels, making it suitable for Arduino and other microcontrollers.

// Example code to control a 2 Channel Relay with Arduino UNO
// Relay 1 is connected to pin 7, and Relay 2 is connected to pin 8

#define RELAY1 7  // Define pin for Relay 1
#define RELAY2 8  // Define pin for Relay 2

void setup() {
  pinMode(RELAY1, OUTPUT); // Set Relay 1 pin as output
  pinMode(RELAY2, OUTPUT); // Set Relay 2 pin as output

  // Initialize relays to OFF state
  digitalWrite(RELAY1, LOW); // Ensure Relay 1 is OFF
  digitalWrite(RELAY2, LOW); // Ensure Relay 2 is OFF
}

void loop() {
  // Turn Relay 1 ON and Relay 2 OFF
  digitalWrite(RELAY1, HIGH); // Activate Relay 1
  digitalWrite(RELAY2, LOW);  // Deactivate Relay 2
  delay(2000); // Wait for 2 seconds

  // Turn Relay 1 OFF and Relay 2 ON
  digitalWrite(RELAY1, LOW);  // Deactivate Relay 1
  digitalWrite(RELAY2, HIGH); // Activate Relay 2
  delay(2000); // Wait for 2 seconds
}

1. Relay Not Activating:

   • Cause: Insufficient control signal voltage.
   • Solution: Ensure the control signal voltage is within the required range (3.3V to 5V).

2. Load Not Switching:

   • Cause: Incorrect wiring of the load terminals.
   • Solution: Verify the connections to the COM, NO, and NC terminals.

3. Relay Clicking Noise:

   • Cause: Unstable power supply or noisy control signals.
   • Solution: Use a stable power source and add decoupling capacitors if necessary.

4. Overheating:

   • Cause: Exceeding the maximum load ratings.
   • Solution: Ensure the load does not exceed 10A at 250V AC or 30V DC.

• Q: Can I use the relay with a 3.3V microcontroller like ESP32?
  A: Yes, the relay is compatible with 3.3V control signals, but ensure the power supply to the relay module is 5V.

• Q: Is the relay suitable for switching DC motors?
  A: Yes, but use flyback diodes across the motor terminals to protect the relay from voltage spikes.

• Q: Can I control both relays independently?
  A: Yes, each relay has its own control pin (IN1 and IN2) for independent operation.