In this tutorial, you will learn how to control a standard AC bulb using the Greycode Board and a relay module. This is a foundational project in home automation, where microcontrollers like the Greycode Board can remotely control high-voltage appliances (like lights, fans, or sockets) using relays.

Components Needed

• Greycode IoT Dev Board
• Single-channel Relay Module
• AC Bulb + Holder
• 230V AC Power Source
• Jumper Wires
• C-type USB Cable
• Breadboard (Optional)

Additional Requirements

• BLYNK IoT Application
• Internet Connection

Part 1: Physical Connection

Relay Module Pins:

• IN - GPIO 26 (GREYCODE Board)
• VCC - 5V (GREYCODE Board)
• GND - GND (GREYCODE Board)
• COM - Live Wire From AC
• NO Live Wire To Bulb

Neutral wire goes directly to the bulb's other terminal

Circuit Diagram

Use the circuit diagram below as a connection reference.

Part 2: Setup Blynk App

Step 1: Blynk Setup

1. Install the Blynk IoT app from the Play Store or App Store.
2. Sign up and visit https://blynk.cloud.
3. Create a new template:
   • Name: LED Control
   • Hardware: Greycode Dev Board
   • Connection: Wi-Fi

4. Create a Datastream:
   • Type: Virtual Pin (V0)
   • Data Type: Integer
   • Min: 0
   • Max: 1

5. Save your template configuration.
6. Copy the following information:
   • Template ID
   • Device Name
   • Auth Token

Step 2: Code Setup (Visual Studio / PlatformIO)

1. Create a new project:
   • Name: BlynkLED
   • Board: ESP32 Dev Module
   • Framework: Arduino
2. Install the Blynk library (via Library Manager).

Main Code

#define BLYNK_TEMPLATE_ID "TMPL2RepqsLwr"
#define BLYNK_TEMPLATE_NAME "Blink LED/Bulb"
#define BLYNK_AUTH_TOKEN "6HlsOi4LFaPrH4vFrtVlsFy0HNMfcbXG"

#include <WiFi.h>
#include <BlynkSimpleEsp32.h>

#define RELAY_PIN 2

char auth[] = BLYNK_AUTH_TOKEN;
char ssid[] = "Peace C33";
char pass[] = "12345678";

BLYNK_WRITE(V0) {
  int state = param.asInt();
  digitalWrite(RELAY_PIN, state);
  Serial.println(state ? "Relay ON" : "Relay OFF");
}

void setup() {
  Serial.begin(115200);
  pinMode(RELAY_PIN, OUTPUT);
  digitalWrite(RELAY_PIN, LOW); // Relay is OFF by default
  Blynk.begin(auth, ssid, pass);
}

void loop() {
  Blynk.run();
}
                    

Step 3: Upload and Monitor

1. Connect your Greycode board via USB-C.
2. Click Build (✓) then Upload (→).
3. Open the Serial Monitor to confirm connection logs and relay status.

Step 4: Mobile App Setup

1. Create a device in Blynk using your template.

2. Add a Button widget and link it to V0.
3. Set the mode to Switch.

Manual Testing

• You can modify the code to blink the bulb ON for 3 seconds, OFF for 3 seconds as a test.
• Using the Blynk app, toggle the button to turn the bulb ON/OFF instantly.

Conclusion

You've successfully created a smart bulb setup using the Greycode IoT Board and Blynk. With this knowledge, you can control any AC appliance, schedule routines, or even integrate voice control.

Troubleshooting Tips

• No Wi-Fi connection? Check the code to see if Wi-Fi credentials are correct and ensure that your Wi-Fi is stable.

Start Your Own Project Now