Interface Relay with NodeMCU

Overview

In this tutorial, we will learn how to interface a relay module with NodeMCU, allowing us to safely control high-power AC devices using a microcontroller.

What We Will Learn in This Section

• Understanding how relays work
• Connecting a relay module to NodeMCU
• Writing Arduino and MicroPython code to control the relay
• Safety considerations when working with AC devices

Why Is This Lesson Important to You?

Learning to interface relays with NodeMCU opens up possibilities for home automation and IoT projects. It allows you to control appliances such as lights, fans, and more, using your microcontroller safely and effectively.

Components List (Amazon Affiliate Links)

• NodeMCU
• Relay module
• Jumper wires
• AC device (e.g., light bulb)
• Breadboard

Circuit Diagram (With Connection)

• NodeMCU D5 to Relay Signal Pin
• NodeMCU GND to Relay GND
• Relay VCC to External 5V Power Supply
• AC Device to Relay Common (COM) and Normally Open (NO) Pin

Code Arduino

int relayPin = D5; // Define NodeMCU pin connected to relay module

void setup() {
  pinMode(relayPin, OUTPUT);
}

void loop() {
  // Example: Turn on relay when button is pressed
  if (digitalRead(D2) == HIGH) { // Assuming D2 is connected to a push button
    digitalWrite(relayPin, HIGH); // Turn on relay
  } else {
    digitalWrite(relayPin, LOW); // Turn off relay
  }
}

Code Explanation (Arduino)

• int relayPin = D5;: Defines the pin connected to the relay module.
• pinMode(relayPin, OUTPUT);: Configures relayPin as an output.
• digitalRead(D2): Reads the state of D2 (connected to a push button).
• digitalWrite(relayPin, HIGH): Sets relayPin high, turning on the relay.

Code MicroPython

relay_pin = 14  # Define NodeMCU pin connected to relay module

def setup():
    global relay_pin
    pin(relay_pin, OUT)

def loop():
    global relay_pin
    if pin(4).value() == 1:  # Assuming pin 4 is connected to a push button
        pin(relay_pin, 1)  # Turn on relay
    else:
        pin(relay_pin, 0)  # Turn off relay

Code Explanation (MicroPython)

• relay_pin = 14: Defines the pin connected to the relay module.
• pin(relay_pin, OUT): Configures relay_pin as an output.
• pin(4).value(): Reads the state of pin 4 (connected to a push button).
• pin(relay_pin, 1): Sets relay_pin high, turning on the relay.

Final Notes

Interfacing relays with NodeMCU provides a flexible way to control high-power devices safely. Ensure proper wiring and observe safety precautions, especially when dealing with AC voltage. Experiment with different appliances and expand your IoT projects using these principles.