IoT-Based 4-Channel Relay Control using ESP8266 and Arduino

Features

✅ Remote Control – Operate relays via the Arduino IoT Cloud dashboard✅ Manual Control – Use physical push buttons to toggle relays✅ WiFi Connectivity Indicator – An LED shows the status of the WiFi connection✅ State Synchronization – Whether toggled manually or remotely, relay states remain synchronized

Circuit Diagram

Connections

Relays

Relay

ESP8266 Pin

Relay 1

D1 (GPIO 5)

Relay 2

D2 (GPIO 4)

Relay 3

D5 (GPIO 14)

Relay 4

D6 (GPIO 12)

Push Buttons

Switch

ESP8266 Pin

Switch 1

SD3 (GPIO 10)

Switch 2

D3 (GPIO 0)

Switch 3

D7 (GPIO 13)

Switch 4

RX (GPIO 3)

WiFi LED

• WiFi Status LED → D0 (GPIO 16)

Setting Up Arduino IoT Cloud

Step 1: Create a New Thing

• Go to Arduino IoT Cloud
• Create a new "Thing"

Add four Boolean variables:

• relay1
• relay2
• relay3
• relay4
• Add four Boolean variables:relay1
relay2
relay3
relay4

• Set each as Read & Write with ON_CHANGE trigger.

Step 2: Configure Device

• Select ESP8266 NodeMCU as the device
• Link your WiFi credentials
• Copy the Secret Key for use in the code

Arduino Code

Upload the following final working code to your ESP8266:

Also Visit GitHub https://github.com/ElectroIoT/ESP8266-NodeMCU-4CH-Relay-Module

For Documents Visit My Bloghttps://electroiot.in/index.php/2025/01/30/esp8266-4-relay-iot-control-with-arduino-cloud-push-buttons

How It Works

• Cloud Dashboard: The Arduino IoT Cloud lets you toggle each relay remotely.
• Manual Push Buttons: Pressing a button toggles its corresponding relay.
• WiFi LED Indicator: If WiFi is disconnected, the LED turns ON; otherwise, it stays OFF.
• State Synchronization: The relays remain updated whether controlled remotely or manually.

#include <ArduinoIoTCloud.h>
#include <Arduino_ConnectionHandler.h>
#include <ESP8266WiFi.h>

const char DEVICE_LOGIN_NAME[] = ""; // Enter DEVICE ID
const char SSID[] = "";            // Enter WiFi SSID
const char PASS[] = "";            // Enter WiFi password
const char DEVICE_KEY[] = "";      // Enter Secret device password

// Define GPIO for Relays and Switches
#define RelayPin1 5  // D1
#define RelayPin2 4  // D2
#define RelayPin3 14 // D5
#define RelayPin4 12 // D6

#define SwitchPin1 10 // SD3
#define SwitchPin2 0  // D3
#define SwitchPin3 13 // D7
#define SwitchPin4 3  // RX

#define wifiLed 16 // D0

int toggleState_1 = 0, toggleState_2 = 0, toggleState_3 = 0, toggleState_4 = 0;

void onRelay1Change();
void onRelay2Change();
void onRelay3Change();
void onRelay4Change();

CloudSwitch relay1, relay2, relay3, relay4;

void initProperties() {
  ArduinoCloud.setBoardId(DEVICE_LOGIN_NAME);
  ArduinoCloud.setSecretDeviceKey(DEVICE_KEY);
  ArduinoCloud.addProperty(relay1, READWRITE, ON_CHANGE, onRelay1Change);
  ArduinoCloud.addProperty(relay2, READWRITE, ON_CHANGE, onRelay2Change);
  ArduinoCloud.addProperty(relay3, READWRITE, ON_CHANGE, onRelay3Change);
  ArduinoCloud.addProperty(relay4, READWRITE, ON_CHANGE, onRelay4Change);
}

WiFiConnectionHandler ArduinoIoTPreferredConnection(SSID, PASS);

void setup() {
  Serial.begin(9600);
  initProperties();
  ArduinoCloud.begin(ArduinoIoTPreferredConnection);
  
  pinMode(RelayPin1, OUTPUT); pinMode(RelayPin2, OUTPUT);
  pinMode(RelayPin3, OUTPUT); pinMode(RelayPin4, OUTPUT);
  pinMode(wifiLed, OUTPUT);

  pinMode(SwitchPin1, INPUT_PULLUP);
  pinMode(SwitchPin2, INPUT_PULLUP);
  pinMode(SwitchPin3, INPUT_PULLUP);
  pinMode(SwitchPin4, INPUT_PULLUP);

  digitalWrite(RelayPin1, HIGH); digitalWrite(RelayPin2, HIGH);
  digitalWrite(RelayPin3, HIGH); digitalWrite(RelayPin4, HIGH);
  digitalWrite(wifiLed, HIGH);
}

void loop() {
  ArduinoCloud.update();
  manual_control();
  digitalWrite(wifiLed, WiFi.status() != WL_CONNECTED ? HIGH : LOW);
}

void manual_control() {
  if (digitalRead(SwitchPin1) == LOW) { toggleState_1 = !toggleState_1; digitalWrite(RelayPin1, !toggleState_1); relay1 = toggleState_1; }
  if (digitalRead(SwitchPin2) == LOW) { toggleState_2 = !toggleState_2; digitalWrite(RelayPin2, !toggleState_2); relay2 = toggleState_2; }
  if (digitalRead(SwitchPin3) == LOW) { toggleState_3 = !toggleState_3; digitalWrite(RelayPin3, !toggleState_3); relay3 = toggleState_3; }
  if (digitalRead(SwitchPin4) == LOW) { toggleState_4 = !toggleState_4; digitalWrite(RelayPin4, !toggleState_4); relay4 = toggleState_4; }
}

void onRelay1Change() { digitalWrite(RelayPin1, relay1 ? LOW : HIGH); toggleState_1 = relay1; }
void onRelay2Change() { digitalWrite(RelayPin2, relay2 ? LOW : HIGH); toggleState_2 = relay2; }
void onRelay3Change() { digitalWrite(RelayPin3, relay3 ? LOW : HIGH); toggleState_3 = relay3; }
void onRelay4Change() { digitalWrite(RelayPin4, relay4 ? LOW : HIGH); toggleState_4 = relay4; }