How to Use 1 Channel Relay module with Optocoupler: Examples, Pinouts, and Specs

The 1 Channel Relay Module with Optocoupler (Manufacturer: Songle, Part ID: SRD-05VDC-SL-C) is a versatile electronic component designed to control high-voltage devices using low-voltage signals. This module is equipped with an optocoupler, which provides electrical isolation between the control circuit and the high-voltage load, ensuring safety and protecting sensitive components from potential damage.

• Home automation systems (e.g., controlling lights, fans, or appliances)
• Industrial control systems
• IoT projects for remote device control
• Robotics and mechatronics
• Motor control and switching applications

Below are the key technical details and pin configuration for the 1 Channel Relay Module with Optocoupler:

1. Power the Module: Connect the VCC pin to a 5V DC power source and the GND pin to the ground.
2. Control Signal: Connect the IN pin to a microcontroller (e.g., Arduino UNO) or any other control circuit capable of providing a 3.3V to 5V signal.
3. Load Connection:
   • Connect the high-voltage device (load) to the COM and either the NO or NC terminal:
     • Use NO if the load should be OFF by default and turn ON when the relay is activated.
     • Use NC if the load should be ON by default and turn OFF when the relay is activated.
4. Activate the Relay: Send a HIGH signal (3.3V to 5V) to the IN pin to activate the relay and switch the load.

• Electrical Isolation: The optocoupler ensures isolation between the control circuit and the high-voltage load. Always verify the isolation to prevent damage to sensitive components.
• Power Supply: Ensure the power supply can provide sufficient current for the relay coil (typically ~70mA).
• Load Ratings: Do not exceed the maximum load voltage (250V AC / 30V DC) or current (10A) to avoid damage or hazards.
• Flyback Diode: If controlling an inductive load (e.g., motor), use a flyback diode across the load to suppress voltage spikes.
• Safety Precautions: When working with high-voltage loads, ensure proper insulation and avoid direct contact with live wires.

Below is an example of how to control the relay module using an Arduino UNO:

• Connect VCC to the Arduino's 5V pin.
• Connect GND to the Arduino's GND pin.
• Connect the IN pin to Arduino digital pin 7.
• Connect the load to the COM and NO terminals.

// Define the relay control pin
const int relayPin = 7;

void setup() {
  // Set the relay pin as an output
  pinMode(relayPin, OUTPUT);
  
  // Ensure the relay is OFF at startup
  digitalWrite(relayPin, LOW);
}

void loop() {
  // Turn the relay ON
  digitalWrite(relayPin, HIGH);
  delay(5000); // Keep the relay ON for 5 seconds
  
  // Turn the relay OFF
  digitalWrite(relayPin, LOW);
  delay(5000); // Keep the relay OFF for 5 seconds
}

1. Relay Not Activating:

   • Ensure the VCC and GND pins are properly connected to a 5V power source.
   • Verify that the control signal on the IN pin is within the required range (3.3V to 5V).
   • Check for loose or incorrect wiring.

2. Load Not Switching:

   • Confirm that the load is correctly connected to the COM and NO or NC terminals.
   • Ensure the load does not exceed the relay's maximum voltage or current ratings.
   • Test the relay module with a multimeter to verify proper operation.

3. Interference or Noise:

   • Use a flyback diode across inductive loads to suppress voltage spikes.
   • Keep high-voltage and low-voltage wiring separate to reduce interference.

4. Module Overheating:

   • Ensure the load current does not exceed 10A.
   • Provide adequate ventilation around the module.

Q1: Can I use this relay module with a 3.3V microcontroller?
A1: Yes, the module can be triggered with a 3.3V signal, but ensure the VCC pin is powered with 5V.

Q2: Is the relay module suitable for DC loads?
A2: Yes, the module supports DC loads up to 30V and 10A.

Q3: Can I control multiple relay modules with one microcontroller?
A3: Yes, as long as the microcontroller has enough GPIO pins and can supply the required current for each module.

Q4: What happens if I connect the load incorrectly?
A4: Incorrect connections may result in the load not switching or potential damage to the module. Double-check all connections before powering the circuit.