Compare Uno, Nano, Mega, Leonardo, Pro Mini and LilyPad by MCU, I/O count, memory, voltage, size and programming requirements.
Build local phone control with an HC-05 and isolated relay, with correct 3.3V signal handling, safe startup logic, and mains precautions.
Understand the Arduino platform, the difference between a board and a microcontroller, the development environment, and a sound learning path.
Prepare a safe workspace, install Arduino IDE, select the correct board and port, and verify communication with Blink before wiring a circuit.