ESP-01 Relay Module
The smallest useful node — one ESP-01, one relay, one button.
- Minimum viable smart switch, small enough to fit inside an existing fitting
- Local button wired in parallel with network control
The baseline node that most of the other home automation projects here grew out of. An ESP-01 is barely a development board — two usable GPIOs and an awkward 3.3 V-only supply — but that is exactly enough for one relay and one button, and it fits in places a full ESP32 board does not.
Worth knowing before building one: the ESP-01’s two GPIOs are also its boot-mode straps, so whatever is attached to them must not pull them the wrong way at power-up. That constraint is what pushed later projects onto the ESP32 and eventually into the ESP Connection Board pin study.