How to Use 4 Channel Relay : Examples, Pinouts, and Specs

The 4 Channel Relay by JLC PCB (Manufacturer Part ID: UNIO) is an electromechanical switch designed to control four independent circuits using a single control signal. This versatile component is widely used in automation, home appliances, and industrial control systems. It allows low-power control signals, such as those from a microcontroller, to manage high-power devices like motors, lights, and heaters.

• Home automation systems (e.g., controlling lights, fans, or appliances)
• Industrial equipment control
• Robotics and IoT projects
• Motor and actuator control
• Security systems (e.g., activating alarms or locks)

The following table outlines the key technical details of the 4 Channel Relay:

The 4 Channel Relay module has the following pin configuration:

Each relay channel has three terminals:

1. Power the Relay Module: Connect the VCC pin to a 5V DC power source and the GND pin to the ground.
2. Connect Control Signals: Use a microcontroller (e.g., Arduino UNO) to send control signals to the IN1, IN2, IN3, and IN4 pins. A HIGH signal activates the corresponding relay.
3. Connect Load Devices: Attach the devices you want to control to the relay's output terminals (NO, NC, and COM) based on your desired switching configuration.
4. Ensure Safety: Use proper insulation and avoid exceeding the relay's voltage and current ratings.

• Isolation: The module uses optocouplers to isolate the control circuit from the high-power load, ensuring safety.
• Power Supply: Ensure the power supply can provide sufficient current for the relay coils.
• Flyback Diodes: If controlling inductive loads (e.g., motors), use flyback diodes to protect the relay from voltage spikes.
• Avoid Overloading: Do not exceed the maximum load voltage (250V AC / 30V DC) or current (10A).

Below is an example of how to control the 4 Channel Relay using an Arduino UNO:

// Example: Controlling a 4 Channel Relay with Arduino UNO
// Connect IN1, IN2, IN3, and IN4 to Arduino digital pins 2, 3, 4, and 5 respectively.

#define RELAY1 2  // Pin connected to IN1
#define RELAY2 3  // Pin connected to IN2
#define RELAY3 4  // Pin connected to IN3
#define RELAY4 5  // Pin connected to IN4

void setup() {
  // Set relay pins as outputs
  pinMode(RELAY1, OUTPUT);
  pinMode(RELAY2, OUTPUT);
  pinMode(RELAY3, OUTPUT);
  pinMode(RELAY4, OUTPUT);

  // Initialize all relays to OFF
  digitalWrite(RELAY1, LOW);
  digitalWrite(RELAY2, LOW);
  digitalWrite(RELAY3, LOW);
  digitalWrite(RELAY4, LOW);
}

void loop() {
  // Example sequence to toggle relays
  digitalWrite(RELAY1, HIGH); // Turn ON Relay 1
  delay(1000);                // Wait for 1 second
  digitalWrite(RELAY1, LOW);  // Turn OFF Relay 1
  delay(1000);                // Wait for 1 second

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

  // Repeat for RELAY3 and RELAY4 as needed
}

1. Relays Not Activating

   • Cause: Insufficient power supply or incorrect wiring.
   • Solution: Ensure the VCC pin is connected to a stable 5V DC source and the GND pin is properly grounded.

2. Relay Clicking but Load Not Switching

   • Cause: Incorrect wiring of the load to the relay terminals.
   • Solution: Verify the load is connected to the correct NO, NC, and COM terminals.

3. Microcontroller Resetting When Relay Activates

   • Cause: Voltage spikes from inductive loads.
   • Solution: Add flyback diodes across the load to suppress voltage spikes.

4. Relays Always ON or OFF

   • Cause: Control signal voltage mismatch or damaged relay module.
   • Solution: Ensure the control signal voltage matches the relay's trigger voltage (3.3V to 5V). Replace the module if damaged.

Q: Can I use the 4 Channel Relay with a 3.3V microcontroller?
A: Yes, the relay module supports trigger voltages as low as 3.3V, making it compatible with 3.3V microcontrollers like ESP32 or Raspberry Pi.

Q: Is the relay module safe for high-power applications?
A: Yes, but ensure the load does not exceed the maximum ratings (250V AC / 30V DC, 10A). Use proper insulation and safety precautions.

Q: Can I control DC motors with this relay?
A: Yes, but for inductive loads like motors, use flyback diodes to protect the relay from voltage spikes.

Q: How do I know if a relay is active?
A: The module typically includes an LED indicator for each relay channel that lights up when the relay is activated.