How to Use RELAY RED: Examples, Pinouts, and Specs

A relay is an electromechanical switch that uses an electromagnetic coil to open or close contacts, enabling the control of a high-power circuit with a low-power signal. The "RELAY RED" designation may refer to a specific type, color-coded for identification, or a particular rating of the relay. Relays are widely used in applications where electrical isolation, high-power switching, or remote control of circuits is required.

• Home automation systems (e.g., controlling lights, fans, or appliances)
• Automotive electronics (e.g., controlling headlights, horns, or motors)
• Industrial control systems (e.g., motor starters, solenoids, or pumps)
• Microcontroller-based projects (e.g., Arduino or Raspberry Pi applications)
• Safety circuits requiring electrical isolation

• Coil Voltage: 5V DC (typical for microcontroller applications)
• Contact Rating: 10A at 250V AC or 10A at 30V DC
• Coil Resistance: ~70Ω (for 5V coil)
• Switching Type: SPDT (Single Pole Double Throw)
• Isolation: Electrical isolation between control and load circuits
• Operating Temperature: -40°C to 85°C
• Dimensions: 28mm x 10mm x 15mm (approximate)

The RELAY RED typically has 5 pins, as described in the table below:

1. Power the Coil: Connect the coil pins (1 and 2) to a 5V DC power source. Use a transistor or MOSFET to control the coil if using a microcontroller.
2. Connect the Load:
   • Connect the load to the Common (COM) pin (3).
   • Use the Normally Open (NO) pin (4) if you want the load to turn on when the relay is activated.
   • Use the Normally Closed (NC) pin (5) if you want the load to turn off when the relay is activated.
3. Control the Relay: Use a low-power control signal (e.g., from an Arduino) to energize the coil and switch the contacts.

• Flyback Diode: Always connect a flyback diode across the coil terminals to protect the circuit from voltage spikes when the relay is deactivated.
• Current Ratings: Ensure the load current does not exceed the relay's contact rating (10A).
• Isolation: Use optocouplers or transistors to isolate the control circuit from the high-power load circuit.
• Power Supply: Provide a stable 5V DC supply to the coil for reliable operation.

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

// Define the pin connected to the relay control
const int relayPin = 7;

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

void loop() {
  digitalWrite(relayPin, HIGH); // Activate the relay
  delay(1000); // Keep the relay on for 1 second
  digitalWrite(relayPin, LOW); // Deactivate the relay
  delay(1000); // Keep the relay off for 1 second
}

Note: Use a transistor (e.g., 2N2222) between the Arduino and the relay coil to handle the current required by the relay.

1. Relay Not Activating:

   • Cause: Insufficient voltage or current to the coil.
   • Solution: Verify the power supply and ensure the control circuit can provide enough current.

2. Relay Stuck in One State:

   • Cause: Damaged contacts or coil.
   • Solution: Check for physical damage or replace the relay.

3. Voltage Spikes Damaging the Circuit:

   • Cause: Lack of a flyback diode across the coil.
   • Solution: Add a flyback diode (e.g., 1N4007) across the coil terminals.

4. Load Not Switching Properly:

   • Cause: Incorrect wiring of the load to the relay contacts.
   • Solution: Double-check the connections to the COM, NO, and NC pins.

Q1: Can I use the RELAY RED with a 3.3V microcontroller?
A1: Yes, but you will need a transistor or MOSFET to drive the 5V relay coil from the 3.3V control signal.

Q2: What is the purpose of the flyback diode?
A2: The flyback diode protects the control circuit from voltage spikes generated when the relay coil is de-energized.

Q3: Can the RELAY RED switch both AC and DC loads?
A3: Yes, it can switch AC loads up to 250V and DC loads up to 30V, provided the current does not exceed 10A.

Q4: How do I know if the relay is activated?
A4: Many relays, including the RELAY RED, have a built-in LED indicator that lights up when the relay is activated.