Home Automation

Design Motivation & Ideas

This 4-Channel IoT Home Automation Controller was designed to provide a safe, silent, and highly isolated method for switching AC mains loads via Wi-Fi. The primary goal was to eliminate the mechanical wear and acoustic noise of traditional electromechanical relays by utilizing solid-state TRIACs, while ensuring strict galvanic isolation to protect the low-voltage control logic. This architecture offers a robust, standalone solution for integrating conventional home appliances into modern smart home ecosystems without requiring external DC power adapters.

Project Overview

This project is a custom-designed, 4-Channel IoT Home Automation Controller. Built around the ESP8266 architecture, the board is designed to safely and silently switch up to four independent AC mains loads over Wi-Fi. It features complete galvanic isolation between the low-voltage control logic and high-voltage AC lines, making it a robust and safe solution for smart home integrations, lighting control, and automated appliance scheduling.

High Voltage Safety Warning

Please read before replicating this project: This printed circuit board deals directly with potentially lethal AC mains voltage (110V/220V).

• Do not touch the PCB or attempt to probe any components while the board is connected to AC power.

• The PCB layout has been designed with physical separation between the high-voltage traces and the low-voltage logic.

• Always disconnect mains power completely before handling, reprogramming the NodeMCU, or adjusting physical connections. Build and operate at your own risk.

Technical Specifications & Circuit Architecture

1. Core Processing & Connectivity

• Microcontroller: Powered by a NodeMCU Amica V2 (ESP8266) module, providing reliable 2.4GHz Wi-Fi connectivity for IoT applications (such as MQTT, Home Assistant, or custom web servers).

• Manual Override: Incorporates four Omron B3F tactile switches directly connected to the GPIO pins, allowing for manual, physical control of each channel alongside wireless operation.

2. Power Subsystem

• Standalone Operation: Eliminates the need for external DC power adapters by integrating an HLK-PM05 isolated AC-to-DC step-down converter onboard. This module safely converts 110V/220V AC mains directly into a stable 5V DC supply for the NodeMCU and logic circuitry.

3. Optoisolated AC Switching & Load Control

• Galvanic Isolation: To ensure maximum safety and protect the microcontroller from high-voltage spikes, each of the four channels utilizes a MOC3021 optocoupler. This strictly separates the AC side from the DC logic side.

• Solid-State Switching: The load switching is handled by four BT136-600D TRIACs, providing silent, solid-state AC control without the mechanical wear, arcing, or clicking noise associated with traditional mechanical relays.

• Status Indicators: Each output channel features a dedicated LED indicator on the low-voltage side for visual confirmation of the switching state during debugging or operation.

Key Applications

• Integration with open-source smart home ecosystems (e.g., Home Assistant, OpenHAB).

• Automated multi-zone lighting control.

• IoT-enabled fan or low-to-medium power appliance management.