ESP32 8 Channel Wi-Fi Relay | 7 Powerful Steps to Build an ESP32 Automation Project

The ESP32 8 Channel Wi-Fi Relay is a practical and low-cost automation project for controlling up to 8 electrical devices wirelessly. This ESP32 automation project is designed with simple components including an ESP32 Dev Board, ULN2803 relay driver, 8 relays, LEDs, and an OLED display. The system allows real-time monitoring and control through Wi-Fi, making it ideal for home automation, greenhouse monitoring, water pump control, HVAC systems, and industrial machine control.

This guide provides a full circuit explanation, a detailed BOM list, and step-by-step instructions for wiring and programming. The OLED screen displays the live status of each relay, while push buttons allow manual switching alongside web-based control. With built-in Wi-Fi capability, the ESP32 connects directly to a router for remote operation without extra hardware. This project is reliable, expandable, and perfect for DIY IoT automation.

Introduction

Automation has become a central part of both homes and industries. With IoT (Internet of Things), it’s now possible to control lights, fans, pumps, and even machines directly from a smartphone. Instead of buying expensive commercial modules, you can create your own ESP32 8 Channel Wi-Fi Relay system an ESP32 automation project that combines low-cost hardware with versatile software.

This DIY controller allows you to control 8 independent relays through Wi-Fi. Each relay can switch an AC or DC load, making it useful for:

• Smart home lighting

• HVAC (heating, ventilation, air conditioning)

• Water pumps and irrigation

• Greenhouse automation

• Industrial equipment control

In this article, I’ll show you the components, circuit diagram, build steps, and code to bring this project to life.

 Materials for the Project (ESP32 8 Channel Wi-Fi Relay) 

You can get datasheets and more details here:

• ESP32 Official Docs

• ULN2803 IC Datasheet

• Arduino Reference

• Adafruit SSD1306 Library

• Relay Basics

• OLED SSD1306 Datasheet

• I2C Communication Guide

• Safety Guide for Working with Relays

ESP32 Pinout

Gerber Files

⚡ Circuit Diagram Explanation (ESP32 8 Channel Wi-Fi Relay)

The wiring is straightforward but requires attention to safety:

1. ESP32 to ULN2803

   • GPIO pins from the ESP32 are connected to the input pins of the ULN2803 IC.

   • ULN2803 outputs drive the relay coils.

2. Relay Connections

   • Each relay is connected to a 3-pin terminal block (COM, NO, NC).

   • This allows external AC/DC loads to be switched safely.

3. LED Indicators

   • Each relay channel has a yellow LED + 100Ω resistor connected to indicate ON/OFF status.

4. OLED Display

   • Connected via I2C: SDA → GPIO 21, SCL → GPIO 22.

   • Displays relay status and system messages.

5. Push Buttons

   • Button 1 → Manual ON/OFF toggle

   • Button 2 → Reset ESP32

   • Button 3 → Auto/Manual mode switch

6. Power Supply

   • A regulated 5V DC supply powers the ESP32, relays, ULN2803, and OLED.

Step-by-Step Build Guide (ESP32 8 Channel Wi-Fi Relay)

Step 1: Power Setup

• Connect the 5V supply to the ESP32 and relay circuits via the terminal block.

Step 2: Relay Driver Wiring

• ESP32 GPIOs → ULN2803 Inputs

• ULN2803 Outputs → Relay IN pins

Step 3: LED Indicators

• Relay outputs → Yellow LED + 100Ω resistor → GND

Step 4: OLED Display

• Connect SDA → GPIO 21

• Connect SCL → GPIO 22

Step 5: Push Buttons

• Each button connected between GPIO pin and GND.

• Enable internal pull-ups in the ESP32 code.

Step 6: Install Arduino Libraries

• Adafruit SSD1306

• Adafruit GFX

• WiFi.h (for ESP32)

Step 7: Upload Code

• Flash the provided Arduino code onto the ESP32.

• Connect to your Wi-Fi network.

• Access the relay control panel via the ESP32 IP address.

Arduino Code Example (ESP32 8 Channel Wi-Fi Relay)

Here’s a simplified version (full version can be extended with MQTT/Home Assistant):

#include <WiFi.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);const char* ssid = “Your_SSID”;
const char* password = “Your_PASSWORD”;WiFiServer server(80);// Relay pins (ESP32 GPIOs)
int relayPins[8] = {5, 18, 19, 21, 22, 23, 25, 26};
bool relayState[8] = {0,0,0,0,0,0,0,0};void setup() {
Serial.begin(115200);

// Relay setup
for(int i=0; i<8; i++) {
pinMode(relayPins[i], OUTPUT);
digitalWrite(relayPins[i], HIGH); // OFF initially
}

// OLED init
if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
Serial.println(“SSD1306 allocation failed”);
for(;;);
}
display.clearDisplay();
display.setTextSize(1);
display.setTextColor(SSD1306_WHITE);
display.setCursor(0,0);
display.println(“ESP32 Relay Controller”);
display.display();

// Wi-Fi connection
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(“.”);
}
Serial.println(“WiFi connected!”);
server.begin();
}

void loop() {
WiFiClient client = server.available();
if (!client) return;

String request = client.readStringUntil(‘r’);
client.flush();

// Relay control via URL
for(int i=0; i<8; i++) {
if(request.indexOf(“/relay”+String(i+1)+”on”) != -1) {
digitalWrite(relayPins[i], LOW);
relayState[i] = 1;
}
if(request.indexOf(“/relay”+String(i+1)+”off”) != -1) {
digitalWrite(relayPins[i], HIGH);
relayState[i] = 0;
}
}

// HTML page
client.println(“HTTP/1.1 200 OK”);
client.println(“Content-type:text/html”);
client.println();
client.println(“<html><h1>ESP32 Relay Control</h1>”);
for(int i=0; i<8; i++) {
client.println(“<p>Relay ” + String(i+1) + ” – State: ” + (relayState[i]?”ON”:”OFF”));
client.println(” <a href=”/relay”+String(i+1)+”on”>ON</a> “);
client.println(“<a href=”/relay”+String(i+1)+”off”>OFF</a></p>”);
}
client.println(“</html>”);

// OLED update
display.clearDisplay();
display.setCursor(0,0);
display.println(“Relay Status:”);
for(int i=0; i<8; i++) {
display.print(“R”);
display.print(i+1);
display.print(“: “);
display.println(relayState[i] ? “ON” : “OFF”);
}
display.display();
}

Applications

Smart lighting
Greenhouse and irrigation control
HVAC automation
Industrial machinery control
Smart water pump system

❓ FAQs

Q1: Can I control this from anywhere on the internet?
Yes, with port forwarding or MQTT you can access it remotely.

Q2: How much current can each relay handle?
Standard 5V relays support 10A at 250V AC or 30V DC.

Q3: Can I expand beyond 8 relays?
Yes, by using additional ULN2803 ICs and relays.

Q4: Is it safe to use with high voltage?
Yes, but ensure isolation and proper insulation when wiring AC loads.

Conclusion

This ESP32 8 Channel Wi-Fi Relay project is a powerful DIY automation solution. With just an ESP32, ULN2803, relays, LEDs, and an OLED display, you can create a smart system to control multiple devices over Wi-Fi.

It’s flexible, expandable, and integrates easily with smart home systems like Home Assistant or MQTT. Whether for home, greenhouse, or industrial use, this ESP32 automation project delivers reliable results at low cost.