2-Channel 5V Opto-Isolated Relay Module – 10A/250VAC SPDT for Arduino PLC Automation (DIN Rail Mountable)5V

Usage Guide

How It Works

The module uses an optocoupler to isolate the low-voltage control side (connected to your microcontroller) from the high-voltage load side. When the trigger input (IN1 or IN2) receives the appropriate signal (HIGH or LOW depending on jumper configuration), the optocoupler activates, which energizes the relay coil. The energized relay switches the common (COM) terminal connection from the normally closed (NC) contact to the normally open (NO) contact, completing the circuit to your load .

The VCC-JD-VCC jumper (typically located near the power input header) connects the logic power supply to the relay coil power supply. When driving heavy loads or multiple relays simultaneously, you can remove this jumper and supply separate power to the JD-VCC pin to avoid overloading your microcontroller’s 5V regulator .

Wiring Instructions

Step 1 – Control Side Connection (to Microcontroller)

Connect the 4-pin male header (2.54mm pitch) as follows:

Step 2 – Load Side Connection (to High-Power Device)

Each relay channel has a 3-pin screw terminal block:

Wiring Example 1 – Controlling an AC Light Bulb (NO configuration):

• Connect AC Live wire → COM terminal

• Connect AC Neutral wire → Light bulb neutral

• Connect Light bulb live → NO terminal

• When relay activates, the circuit closes and the light turns ON

Wiring Example 2 – Controlling a DC Motor (NO configuration):

• Connect DC power supply positive → COM terminal

• Connect Motor positive → NO terminal

• Connect Motor negative → DC power supply negative directly

⚠️ Safety Warning: High voltage (110V/220V AC) is dangerous. Ensure all connections are properly insulated. Always disconnect power before wiring. Use appropriately gauged wire for your load current. Mount the module in an enclosure for permanent installations.

Trigger Mode Configuration (High/Low Level Jumper)

The module features jumper-selectable trigger modes, typically labeled S1 and S2 (one for each channel) or a single H/L jumper with individual channel selection .

Common Configurations:

• Arduino (5V logic) : Set jumper to HIGH position – relay activates when digitalWrite(pin, HIGH)

• Raspberry Pi (3.3V logic) : Set jumper to LOW position – relay activates when GPIO.output(pin, GPIO.LOW)

• Push-button control : Set to LOW position – connect button between IN pin and GND

To change trigger mode:

1. Locate the jumper on the PCB (usually a small black plastic cap covering two or three header pins)

2. Gently remove the jumper cap

3. Reposition it over the desired pins (refer to silkscreen labels: LOW/GND or HIGH/VCC)

4. Each channel may have its own jumper – configure independently

VCC-JD-VCC Jumper (Separate Relay Power Option)

By default, a jumper connects VCC to JD-VCC, powering the relay coils from the same 5V supply as the logic circuit.

When to remove the jumper:

• Controlling multiple relays simultaneously (high total coil current)

• Using a low-current 5V supply (e.g., USB from a computer)

• Driving heavy inductive loads that cause voltage fluctuations

How to use separate power:

1. Remove the VCC-JD-VCC jumper cap

2. Connect external 5V supply to JD-VCC pin (positive) and GND pin (negative)

3. Connect microcontroller 5V to VCC pin (positive) and same GND pin

4. The logic and relay circuits are now independently powered

Arduino Sample Code (Low-Level Trigger Configuration)

// 2-Channel Relay Module - Low Level Trigger (Jumper set to LOW position)
// Relay activates when pin is set to LOW (0V)

const int RELAY1 = 7;  // IN1 connected to digital pin 7
const int RELAY2 = 8;  // IN2 connected to digital pin 8

void setup() {
  pinMode(RELAY1, OUTPUT);
  pinMode(RELAY2, OUTPUT);
  
  // Initialize both relays to OFF state
  digitalWrite(RELAY1, HIGH);  // HIGH = relay OFF (Low-Level Trigger)
  digitalWrite(RELAY2, HIGH);
}

void loop() {
  // Turn ON Relay 1 (activates load connected to Channel 1)
  digitalWrite(RELAY1, LOW);   // LOW = relay ON
  delay(2000);                  // Wait 2 seconds
  
  // Turn OFF Relay 1
  digitalWrite(RELAY1, HIGH);  // HIGH = relay OFF
  delay(1000);                  // Wait 1 second
  
  // Turn ON Relay 2
  digitalWrite(RELAY2, LOW);
  delay(2000);
  
  // Turn OFF Relay 2
  digitalWrite(RELAY2, HIGH);
  delay(1000);
}

Installation Tips

• Mounting: Secure the module using the four 3.1mm mounting holes with M3 screws or double-sided tape. For DIN rail mounting, use an optional DIN rail adapter bracket .

• Ventilation: Allow adequate airflow around the module, especially when switching high currents continuously.

• Wire Gauge: Use 14-22 AWG wire for load connections depending on current. For 10A loads, minimum 18 AWG copper wire is recommended.

• Enclosure: For permanent installations, mount the module inside a UL-listed electrical enclosure with appropriate strain relief.