How to Use Relay 3 Channel Optocoupler: Examples, Pinouts, and Specs

The Relay 3 Channel Optocoupler module, manufactured by Arduino (Part ID: Relay), is a versatile electronic component designed to control high-voltage devices using low-voltage signals. It features three independent relays, each capable of switching AC or DC loads, and optocoupler isolation to protect the controlling circuit from high-voltage spikes or interference. This module is ideal for applications requiring safe and reliable control of appliances, motors, or other high-power devices.

• Home automation systems (e.g., controlling lights, fans, or appliances)
• Industrial automation and motor control
• IoT projects requiring high-voltage device control
• Robotics and mechatronics systems
• Signal isolation in sensitive circuits

• Operating Voltage: 5V DC
• Relay Channels: 3
• Relay Type: SPDT (Single Pole Double Throw)
• Maximum Load (per channel):
  • AC: 250V at 10A
  • DC: 30V at 10A
• Trigger Voltage: 3.3V to 5V (compatible with Arduino and other microcontrollers)
• Optocoupler Isolation: Yes
• LED Indicators: One per channel (indicates relay activation)
• Dimensions: 50mm x 40mm x 20mm (approx.)

The module has two main interfaces: the control pins and the relay output terminals.

1. Power the Module: Connect the VCC pin to a 5V power source and the GND pin to ground.
2. Connect Control Signals: Use digital output pins from a microcontroller (e.g., Arduino UNO) to control the IN1, IN2, and IN3 pins. A LOW signal activates the corresponding relay.
3. Connect the Load: Wire the high-voltage device to the relay output terminals (COM, NO, and NC) as per your application:
   • Use the NO terminal for devices that should be off by default and turn on when the relay is activated.
   • Use the NC terminal for devices that should be on by default and turn off when the relay is activated.
4. Test the Circuit: Upload the control code to your microcontroller and verify the relay operation.

• Ensure the load current and voltage do not exceed the relay's maximum ratings.
• Use proper insulation and safety precautions when working with high-voltage circuits.
• Avoid switching inductive loads (e.g., motors) without a flyback diode or snubber circuit to prevent voltage spikes.
• Keep the module away from moisture and conductive surfaces to prevent short circuits.

// Example code to control a 3 Channel Relay module with Arduino UNO
// This code toggles each relay ON and OFF with a 1-second delay

// Define the control pins for the relays
#define RELAY1 2  // Relay 1 control pin connected to Arduino pin 2
#define RELAY2 3  // Relay 2 control pin connected to Arduino pin 3
#define RELAY3 4  // Relay 3 control pin connected to Arduino pin 4

void setup() {
  // Set relay control pins as outputs
  pinMode(RELAY1, OUTPUT);
  pinMode(RELAY2, OUTPUT);
  pinMode(RELAY3, OUTPUT);

  // Initialize all relays to OFF state (HIGH signal)
  digitalWrite(RELAY1, HIGH);
  digitalWrite(RELAY2, HIGH);
  digitalWrite(RELAY3, HIGH);
}

void loop() {
  // Turn Relay 1 ON
  digitalWrite(RELAY1, LOW); // Active LOW signal turns the relay ON
  delay(1000);               // Wait for 1 second

  // Turn Relay 1 OFF and Relay 2 ON
  digitalWrite(RELAY1, HIGH); // Turn Relay 1 OFF
  digitalWrite(RELAY2, LOW);  // Turn Relay 2 ON
  delay(1000);                // Wait for 1 second

  // Turn Relay 2 OFF and Relay 3 ON
  digitalWrite(RELAY2, HIGH); // Turn Relay 2 OFF
  digitalWrite(RELAY3, LOW);  // Turn Relay 3 ON
  delay(1000);                // Wait for 1 second

  // Turn all relays OFF
  digitalWrite(RELAY3, HIGH); // Turn Relay 3 OFF
  delay(1000);                // Wait for 1 second
}

1. Relays Not Activating:

   • Ensure the module is powered with a stable 5V supply.
   • Verify that the control signals (IN1, IN2, IN3) are correctly connected and set to LOW to activate the relays.
   • Check for loose or incorrect wiring.

2. High-Voltage Device Not Responding:

   • Confirm that the device is properly connected to the relay output terminals (COM, NO, or NC).
   • Ensure the device's voltage and current requirements are within the relay's specifications.

3. Interference or Unstable Operation:

   • Use a separate power supply for the relay module if the microcontroller's power source is insufficient.
   • Add a flyback diode across inductive loads to suppress voltage spikes.

Q1: Can I use this module with a 3.3V microcontroller?
A1: Yes, the module is compatible with 3.3V control signals, but ensure the VCC pin is still powered with 5V.

Q2: How do I know if a relay is active?
A2: Each relay has an LED indicator that lights up when the relay is activated.

Q3: Can I control AC and DC loads simultaneously?
A3: Yes, each relay channel is independent, so you can control a mix of AC and DC loads as long as they meet the relay's specifications.