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. It features an optocoupler for electrical isolation, ensuring safe operation by protecting the control circuit from high-voltage spikes or surges. This module is widely used in home automation, industrial control systems, and DIY electronics projects.

• Home automation (e.g., controlling lights, fans, or appliances)
• Industrial equipment control
• Robotics and IoT projects
• Motor and pump control
• Arduino and microcontroller-based projects

The relay module has a total of 6 pins, divided into two sections: control pins and load pins.

1. Power the Module: Connect the VCC pin to a 5V DC power supply and the GND pin to the ground.
2. Control Signal: Connect the IN pin to a microcontroller (e.g., Arduino) or any other control circuit. The relay is triggered when the IN pin receives a LOW signal.
3. Load Connection:
   • Connect the high-voltage device to the COM and NO pins if you want the device to turn on when the relay is activated.
   • Use the COM and NC pins if you want the device to turn off when the relay is activated.
4. Isolation: The optocoupler ensures electrical isolation between the control circuit and the high-voltage load, enhancing safety.

• Power Supply: Ensure the module is powered with a stable 5V DC supply.
• Signal Voltage: The IN pin is compatible with 3.3V and 5V logic levels, making it suitable for most microcontrollers.
• Load Ratings: Do not exceed the maximum load voltage (250V AC / 30V DC) or current (10A).
• Safety: Always disconnect the power supply before wiring the high-voltage side to avoid electric shock.
• Flyback Diode: If controlling an inductive load (e.g., motor), use a flyback diode across the load to protect the relay from voltage spikes.

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

• Connect the relay module's VCC to the Arduino's 5V pin.
• Connect the relay module's GND to the Arduino's GND pin.
• Connect the relay module's IN pin to Arduino digital pin 7.
• Connect the load (e.g., a light bulb) to the COM and NO pins of the relay.

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

void setup() {
  pinMode(relayPin, OUTPUT); // Set the relay pin as an output
  digitalWrite(relayPin, HIGH); // Keep the relay off initially (active LOW)
}

void loop() {
  digitalWrite(relayPin, LOW); // Turn the relay ON
  delay(5000); // Keep the relay ON for 5 seconds
  digitalWrite(relayPin, HIGH); // Turn the relay OFF
  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 supply.
   • Verify that the IN pin is receiving a LOW signal (0V) to activate the relay.
   • Check for loose or incorrect wiring.

2. Load Not Turning On/Off:

   • Confirm that the load is correctly connected to the COM and NO/NC pins.
   • Ensure the load does not exceed the relay's voltage and current ratings.

3. Microcontroller Resetting:

   • This may occur if the relay draws too much current. Use a separate power supply for the relay module.

4. High-Voltage Side Not Working:

   • Double-check the wiring on the high-voltage side.
   • Ensure the high-voltage device is functional and within the relay's specifications.

Q1: Can I use this relay module with a 3.3V microcontroller like ESP8266 or Raspberry Pi?
A1: Yes, the IN pin is compatible with 3.3V logic levels. However, ensure the relay module itself is powered with 5V.

Q2: Is the relay module safe for controlling AC appliances?
A2: Yes, the module is designed for high-voltage applications. However, always follow safety precautions when working with AC voltage.

Q3: Can I control multiple relays with one microcontroller?
A3: Yes, you can control multiple relay modules by connecting their IN pins to different GPIO pins on the microcontroller.

Q4: What is the purpose of the optocoupler?
A4: The optocoupler provides electrical isolation between the control circuit and the high-voltage load, protecting the microcontroller from voltage spikes or surges.

By following this documentation, you can safely and effectively use the 1 Channel Relay Module with Optocoupler in your projects.