How to Use Relay 2p 5VDC 8A: Examples, Pinouts, and Specs

The Relay 2p 5VDC 8A (Manufacturer: Relpol, Part ID: RM84-2012-35-1005) is an electromechanical switch designed to control high-power devices using low-power signals. This relay features two poles (DPDT - Double Pole Double Throw), operates at a 5V DC coil voltage, and can handle loads of up to 8A. It is widely used in applications such as home automation, industrial control systems, and robotics.

• Switching high-power AC or DC loads (e.g., motors, lights, heaters)
• Isolating low-power control circuits from high-power devices
• Home automation systems (e.g., smart switches)
• Industrial equipment and machinery control
• Robotics and IoT projects

The relay has a total of 8 pins. The pinout is as follows:

1. Power the Coil: Connect the Coil+ pin to a 5V DC power source and the Coil- pin to ground. This energizes the relay coil and switches the contacts.
2. Connect the Load:
   • For the first pole, connect the load between COM1 and either NO1 (Normally Open) or NC1 (Normally Closed), depending on the desired behavior.
   • For the second pole, connect the load between COM2 and either NO2 or NC2.
3. Control the Relay: Use a microcontroller (e.g., Arduino) or a transistor circuit to control the 5V DC signal to the relay coil.

• Flyback Diode: Always connect a flyback diode (e.g., 1N4007) across the relay coil terminals to protect the driving circuit from voltage spikes when the relay is de-energized.
• Current Ratings: Ensure the load current does not exceed the relay's maximum switching current of 8A.
• Isolation: Use optocouplers or transistors to isolate the control circuit from the relay coil if necessary.
• Power Supply: Use a stable 5V DC power supply to avoid relay malfunction.

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

• Connect Coil+ to a digital pin on the Arduino (e.g., pin 7) through a transistor (e.g., 2N2222) and a 1kΩ base resistor.
• Connect Coil- to the Arduino's GND.
• Add a flyback diode (e.g., 1N4007) across the relay coil terminals.
• Connect the load to the relay's COM and NO or NC terminals as needed.

// Relay Control Example
// This code toggles the relay on and off every second.

#define RELAY_PIN 7  // Define the Arduino pin connected to the relay

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

void loop() {
  digitalWrite(RELAY_PIN, HIGH); // Turn the relay on
  delay(1000);                   // Wait for 1 second
  digitalWrite(RELAY_PIN, LOW);  // Turn the relay off
  delay(1000);                   // Wait for 1 second
}

1. Relay Not Switching

   • Cause: Insufficient voltage or current to the coil.
   • Solution: Verify that the coil is receiving 5V DC and sufficient current. Check the power supply and connections.

2. Load Not Turning On/Off

   • Cause: Incorrect wiring of the load to the relay terminals.
   • Solution: Double-check the connections to COM, NO, and NC terminals. Ensure the load is properly connected.

3. Arduino Pin Not Driving the Relay

   • Cause: The Arduino pin cannot supply enough current to drive the relay directly.
   • Solution: Use a transistor (e.g., 2N2222) as a switch to control the relay.

4. Relay Buzzing Noise

   • Cause: Unstable power supply or insufficient coil voltage.
   • Solution: Ensure a stable 5V DC power supply and check for loose connections.

Q: Can this relay switch both AC and DC loads?
A: Yes, the relay can switch both AC (up to 250V) and DC (up to 30V) loads, provided the current does not exceed 8A.

Q: Is the relay safe for inductive loads like motors?
A: Yes, but you should use a snubber circuit or a flyback diode to protect the relay contacts from arcing caused by inductive loads.

Q: Can I use this relay with a 3.3V microcontroller?
A: Yes, but you will need a transistor or relay driver circuit to step up the control signal to 5V for the relay coil.

Q: What is the lifespan of this relay?
A: The relay has a mechanical lifespan of approximately 10 million operations and an electrical lifespan of around 100,000 operations under rated load conditions.