How to Use relaymk: Examples, Pinouts, and Specs

The RelayMK by NJ (Manufacturer Part ID: REL) is a relay module designed to act as an electronic switch. It uses an electromagnet to mechanically operate a switch, enabling the control of high-voltage or high-current devices using low-voltage signals. This makes it an essential component for interfacing microcontrollers, such as Arduino, with devices like motors, lights, and home appliances.

• Home automation systems (e.g., controlling lights or fans)
• Industrial control systems
• Motor control circuits
• IoT projects requiring high-power device control
• Safety circuits for isolating high-voltage systems from low-voltage control systems

The following table outlines the key technical details of the RelayMK module:

The RelayMK module has the following pin configuration:

1. Power the Module: Connect the VCC pin to a 5V DC power source and the GND pin to ground.
2. Control Signal: Connect the IN pin to a digital output pin of a microcontroller (e.g., Arduino UNO). The relay will activate when the control signal is HIGH.
3. Load Connection:
   • Connect the device you want to control (e.g., a light bulb or motor) to the NO or NC terminal, depending on your desired behavior.
   • Connect the other end of the device to the COM terminal.
4. Isolation: Ensure proper isolation between the low-voltage control circuit and the high-voltage load to prevent damage or hazards.

• Power Supply: Ensure the module is powered with a stable 5V DC supply.
• Load Ratings: Do not exceed the maximum load voltage (250V AC / 30V DC) or current (10A).
• Flyback Diode: If controlling an inductive load (e.g., a motor), use a flyback diode across the load to protect the relay from voltage spikes.
• Safety: Always handle high-voltage connections with care. Disconnect power before making any changes to the circuit.
• Logic Level Compatibility: The IN pin is compatible with both 3.3V and 5V logic levels, making it suitable for most microcontrollers.

Below is an example of how to control a light bulb using the RelayMK module and an Arduino UNO:

• Connect the RelayMK's VCC to the Arduino's 5V pin.
• Connect the RelayMK's GND to the Arduino's GND pin.
• Connect the RelayMK's IN pin to Arduino digital pin 7.
• Connect the light bulb to the NO and COM terminals of the relay.

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

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

void loop() {
  // Turn the relay on (light bulb ON)
  digitalWrite(relayPin, HIGH);
  delay(5000); // Keep the light ON for 5 seconds
  
  // Turn the relay off (light bulb OFF)
  digitalWrite(relayPin, LOW);
  delay(5000); // Keep the light OFF for 5 seconds
}

1. Relay Not Activating

   • Cause: Insufficient control signal voltage.
   • Solution: Ensure the IN pin receives a HIGH signal (3.3V or 5V) from the microcontroller.

2. Load Not Turning On/Off

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

3. Relay Clicking but No Output

   • Cause: Faulty relay or excessive load current.
   • Solution: Check the load's current and voltage ratings. Replace the relay if necessary.

4. Microcontroller Resetting

   • Cause: Voltage spikes from the relay coil.
   • Solution: Add a flyback diode across the relay coil to suppress voltage spikes.

Q1: Can I use the RelayMK with a 3.3V microcontroller like the ESP32?
A1: Yes, the IN pin is compatible with 3.3V logic levels. Ensure the module is powered with 5V.

Q2: Can I control multiple relays with one microcontroller?
A2: Yes, as long as each relay is connected to a separate digital output pin and the microcontroller can supply sufficient current.

Q3: Is the RelayMK suitable for switching DC motors?
A3: Yes, but ensure the motor's voltage and current do not exceed the relay's maximum ratings. Use a flyback diode for protection.

Q4: Can I use the RelayMK to control both AC and DC loads?
A4: Yes, the RelayMK supports both AC (up to 250V) and DC (up to 30V) loads. Always adhere to the specified ratings.