Overview
Automated Light Switch is a retrofit smart home device designed around a single constraint: work with any existing light switch without touching the wall wiring. The actuator clips onto a standard rocker or toggle switch, physically flips it with a small servo, and receives commands over Wi-Fi — making any switch controllable from a phone, a voice assistant, or an automated schedule.
Mechanical Design
The housing was designed in CAD and 3D-printed in PLA. A tension-clip mechanism grips the switch plate without adhesives or screws, making installation and removal tool-free. A micro servo mounted inside the housing drives a small arm that presses against the switch rocker — the geometry was iterated to handle the range of switch heights and travel distances found on standard residential plates.
Electronics & Firmware
The controller is an ESP8266-based module running custom Arduino firmware. On startup it connects to the local Wi-Fi network and registers with a lightweight MQTT broker running on a home server. The firmware exposes three control modes:
- Phone app — a simple iOS shortcut sends MQTT payloads to toggle or set the switch state
- Voice — Siri shortcuts relay commands to the same MQTT topic
- Schedules — on-device cron-style rules (e.g., turn off at midnight) execute without requiring a phone to be present
State is persisted in EEPROM so the device remembers the last known switch position across power cycles.
Outcome
The device has been running continuously for over a year on a single USB power supply, with no wall modifications. The clip-on design means it can be moved between switches in seconds.