5V SPDT Relay Documentation

1. Introduction

The 5V Single Pole Double Throw (SPDT) Relay is an electromechanical switch designed to control high-power circuits using a low-power signal. It is widely used in applications where electrical isolation is required between the control circuit and the load circuit. The relay consists of a coil, a common terminal (COM), a normally closed terminal (NC), and a normally open terminal (NO). When the relay is activated, the internal switch toggles between the NC and NO terminals.

Common Applications:

• Home automation (e.g., controlling lights, fans, or appliances)
• Industrial control systems
• Motor control
• Security systems
• Automotive electronics
• IoT projects with microcontrollers (e.g., Arduino, Raspberry Pi)

2. Technical Specifications

The following table outlines the key technical details of the 5V SPDT relay:

Pin Configuration and Descriptions

3. Usage Instructions

How to Use the 5V SPDT Relay in a Circuit

1. Power the Relay:

   • Connect the relay's VCC pin to a 5V DC power supply.
   • Connect the GND pin to the ground of the power supply.

2. Control Signal:

   • Connect the IN pin to a microcontroller's GPIO pin (e.g., Arduino) or any control circuit.
   • When the control signal is HIGH (5V), the relay activates, switching the internal contacts.

3. Load Connection:

   • Connect the load to the COM terminal.
   • Use the NC terminal if the load should be ON when the relay is inactive.
   • Use the NO terminal if the load should be ON when the relay is active.

4. Isolation:

   • Ensure electrical isolation between the control circuit and the load circuit to prevent damage.

Circuit Diagram Example

Below is a simple circuit diagram for controlling a 230V AC light bulb using an Arduino and a 5V SPDT relay:

Arduino Pin D7 -----> IN (Relay)
5V (Arduino) -------> VCC (Relay)
GND (Arduino) ------> GND (Relay)

COM (Relay) --------> Live wire of the AC load
NO (Relay) ---------> Live wire of the light bulb
Neutral (AC) -------> Neutral wire of the light bulb

Best Practices:

• Use a flyback diode across the relay coil to protect the control circuit from voltage spikes.
• Avoid exceeding the relay's maximum voltage and current ratings.
• Use proper insulation and safety precautions when working with high-voltage loads.
• Use an external transistor or relay driver circuit if the control signal cannot provide sufficient current.

4. Arduino Example Code

The following example demonstrates how to control a 5V SPDT relay using an Arduino UNO:

// Define the relay control pin
const int relayPin = 7; // Connect the relay's IN pin to Arduino pin 7

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

void loop() {
  // Turn the relay ON
  digitalWrite(relayPin, HIGH); // Activates the relay
  delay(5000); // Keep the relay ON for 5 seconds

  // Turn the relay OFF
  digitalWrite(relayPin, LOW); // Deactivates the relay
  delay(5000); // Keep the relay OFF for 5 seconds
}

Code Explanation:

• The relay is connected to pin 7 of the Arduino.
• The setup() function initializes the relay pin as an output and ensures the relay is OFF initially.
• The loop() function alternates between turning the relay ON and OFF every 5 seconds.

5. Troubleshooting and FAQs

Common Issues and Solutions

Frequently Asked Questions

1. Can I use the 5V SPDT relay with a 3.3V microcontroller?

   • Yes, but you may need a transistor or relay driver circuit to boost the control signal to 5V.

2. What is the purpose of the flyback diode?

   • The flyback diode protects the control circuit from voltage spikes generated when the relay coil is de-energized.

3. Can I control multiple relays with one Arduino?

   • Yes, as long as each relay is connected to a separate GPIO pin and the total current draw does not exceed the Arduino's limits.

4. Is the relay safe for high-voltage applications?

   • Yes, but ensure proper insulation and safety precautions when working with high-voltage loads.

6. Conclusion

The 5V SPDT Relay is a versatile and essential component for controlling high-power circuits with low-power signals. Its ability to provide electrical isolation and handle high voltages and currents makes it ideal for a wide range of applications. By following the usage instructions and best practices outlined in this documentation, you can safely and effectively integrate the relay into your projects.