SmartPlug PCB

ESP32-C3 HomeKit Smart Plug

A standalone WiFi smart plug built around the ESP32-C3 Super Mini, exposing native Apple HomeKit control via esp-homekit-sdk.

Overview

The ESP32-C3 connects directly to the home WiFi network and implements the HomeKit Accessory Protocol (HAP) on-device using Espressif's open-source esp-homekit-sdk. It advertises itself as a HomeKit accessory and pairs directly with the Apple Home app. A relay switches mains power to a connected load (tested with a small AC fan), with a local status LED and a manual push-button override.

Hardware

• MCU: ESP32-C3 Super Mini (WiFi + BLE)
• Relay: Songle SRD-05VDC-SL-C
• Relay drive: 2N3904 NPN, low-side switched, 1k base resistor, 1N4007 flyback diode across the coil
• Mains supply: Hi-Link HLK-PM01 (AC → 5V)
• I/O: status LED, manual push-button (SW2)
• Connectors: 5.08mm pitch screw terminals for mains in/out
• Custom PCB (KiCad), hand-solderable THT components throughout

Firmware

• Toolchain: PlatformIO, framework = espidf
• Application logic: plain ESP-IDF C — GPIO config, debounced button input, LED/relay control
• HomeKit layer: esp-homekit-sdk (Espressif's open-source HAP implementation), added as an ESP-IDF component
• WiFi credentials configured via idf.py menuconfig (hardcoded); HomeKit pairing done separately after WiFi connects via the HomeKit setup code

Setup

• git clone --recursive git@github.com:mempb/ESP32-SmartPlug.git
• Install PlatformIO VSCode extension
• WiFi SSID & password:
  • Option A: pio run -t menuconfig → App Wi-Fi → Source of Wi-Fi Credentials → Use Hardcoded → set SSID and password
  • Option B: edit sdkconfig.esp32-c3-devkitm-1:
    • CONFIG_APP_WIFI_SSID="SSID"
    • CONFIG_APP_WIFI_PASSWORD="pass"
• Build/flash: pio run -t upload -t monitor

Roadmap

• Schematic design
• PCB layout and routing, order
• PCB assembly (hand soldering)
• GPIO firmware: button input, debounce, LED toggle
• HomeKit firmware (esp-homekit-sdk integration, relay control, button + LED sync)
• Respin PCB, order (smaller form factor, fix missing GND trace, add capacitor)
• Enclosure design/print
• Final writeup: build photos, schematics, wiring diagram, etc

Repo Structure

/components esp-homekit-sdk location
/pcb        KiCad project
/src        ESP-IDF source
/docs       Schematics, pictures, etc. (TODO)
/housing    3D print housing design (TODO)

References

• https://docs.espressif.com/projects/esp-idf/en/stable/esp32/index.html
• https://github.com/espressif/esp-homekit-sdk